Archive for the ‘Calcium Signaling’ Category

Happy 80th Birthday: Radioiodine (RAI) Theranostics: Collaboration between Physics and Medicine, the Utilization of Radionuclides to Diagnose and Treat: Radiation Dosimetry by Discoverer Dr. Saul Hertz, the early history of RAI in diagnosing and treating Thyroid diseases and Theranostics


Guest Author: Barbara Hertz



Celebrating eighty years of radionuclide therapy and the work of Saul Hertz

First published: 03 February 2021

Both authors contributed to the development, drafting and final editing of this manuscript and are responsible for its content.


March 2021 will mark the eightieth anniversary of targeted radionuclide therapy, recognizing the first use of radioactive iodine to treat thyroid disease by Dr. Saul Hertz on March 31, 1941. The breakthrough of Dr. Hertz and collaborator physicist Arthur Roberts was made possible by rapid developments in the fields of physics and medicine in the early twentieth century. Although diseases of the thyroid gland had been described for centuries, the role of iodine in thyroid physiology had been elucidated only in the prior few decades. After the discovery of radioactivity by Henri Becquerel in 1897, rapid advancements in the field, including artificial production of radioactive isotopes, were made in the subsequent decades. Finally, the diagnostic and therapeutic use of radioactive iodine was based on the tracer principal that was developed by George de Hevesy. In the context of these advancements, Hertz was able to conceive the potential of using of radioactive iodine to treat thyroid diseases. Working with Dr. Roberts, he obtained the experimental data and implemented it in the clinical setting. Radioiodine therapy continues to be a mainstay of therapy for hyperthyroidism and thyroid cancer. However, Hertz struggled to gain recognition for his accomplishments and to continue his work and, with his early death in 1950, his contributions have often been overlooked until recently. The work of Hertz and others provided a foundation for the introduction of other radionuclide therapies and for the development of the concept of theranostics.











Dr. Saul Hertz was Director of The Massachusetts General Hospital’s Thyroid Unit, when he heard about the development of artificial radioactivity. He conceived and brought from bench to bedside the successful use of radioiodine (RAI) to diagnose and treat thyroid diseases. Thus was born the science of theragnostics used today for neuroendocrine tumors and prostate cancer. Dr. Hertz’s work set the foundation of targeted precision medicine.

Keywords: Dr. Saul Hertz, nuclear medicine, radioiodine


How to cite this article:
Hertz B. A tribute to Dr. Saul Hertz: The discovery of the medical uses of radioiodine. World J Nucl Med 2019;18:8-12


How to cite this URL:
Hertz B. A tribute to Dr. Saul Hertz: The discovery of the medical uses of radioiodine. World J Nucl Med [serial online] 2019 [cited 2021 Mar 2];18:8-12. Available from: http://www.wjnm.org/text.asp?2019/18/1/8/250309



  • Dr Saul Hertz (1905-1950) discovers the medical uses of radioiodine

Barbara Hertz, Pushan Bharadwaj, Bennett Greenspan»

Abstract » PDF» doi: 10.24911/PJNMed.175-1582813482





  • Happy 80th Birthday: Radioiodine (RAI) Theranostics

Thyroid practitioners and patients are acutely aware of the enormous benefit nuclear medicine has made to mankind. This month we celebrate the 80th anniversary of the early use of radioiodine(RAI).

Dr. Saul Hertz predicted that radionuclides “…would hold the key to the larger problem of cancer in general,” and may just be the best hope for diagnosing and treating cancer successfully.  Yes, RAI has been used for decades to diagnose and treat disease.  Today’s “theranostics,” a term that is a combination of “therapy” and “diagnosis” is utilized in the treatment of thyroid disease and cancer. 

            This short note is to celebrate Dr. Saul Hertz who conceived and brought from bench to bedside the medical uses of RAI; then in the form of 25 minute iodine-128.  

On March 31st 1941, Massachusetts General Hospital’s Dr. Saul Hertz (1905-1950) administered the first therapeutic use of Massachusetts Institute of Technology (MIT) cyclotron produced RAI.  This landmark case was the first in Hertz’s clinical studies conducted with MIT, physicist Arthur Roberts, Ph.D.

[Photo – Courtesy of Dr Saul Hertz Archives ]

Dr Saul Hertz demonstrating RAI Uptake Testing

            Dr. Hertz’s research and successful utilization of radionuclides to diagnose and treat diseases and conditions, established the use of radiation dosimetry and the collaboration between physics and medicine and other significant practices.   Sadly, Saul Hertz (a WWII veteran) died at a very young age.  


About Dr. Saul Hertz

Dr. Saul Hertz (1905 – 1950) discovered the medical uses of radionuclides.  His breakthrough work with radioactive iodine (RAI) created a dynamic paradigym change integrating the sciences.  Radioactive iodine (RAI) is the first and Gold Standard of targeted cancer therapies.  Saul Hertz’s research documents Hertz as the first and foremost person to conceive and develop the experimental data on RAI and apply it in the clinical setting.

Dr. Hertz was born to Orthodox Jewish immigrant parents in Cleveland, Ohio on April 20, 1905. He received his A.B. from the University of Michigan in 1925 with Phi Beta Kappa honors. He graduated from Harvard Medical School in 1929 at a time of quotas for outsiders. He fulfilled his internship and residency at Mt. Sinai Hospital in Cleveland. He came back to Boston in 1931 as a volunteer to join The Massachusetts General Hospital serving as the Chief of the Thyroid Unit from 1931 – 1943.

Two years after the discovery of artifically radioactivity, on November 12, 1936 Dr. Karl Compton, president of the Massachusetts Institute of Technology (MIT), spoke at Harvard Medical School.  President Compton’s topic was What Physics can do for Biology and Medicine. After the presentation Dr. Hertz spontaneously asked Dr. Compton this seminal question, “Could iodine be made radioactive artificially?” Dr. Compton responded in writing on December 15, 1936 that in fact “iodine can be made artificially radioactive.”

Shortly thereafter, a collaboration between Dr. Hertz (MGH) and Dr. Arthur Roberts, a physicist of MIT, was established. In late 1937, Hertz and Roberts created and produced animal studies  involving 48 rabbits that demonstrated that the normal thyroid gland concentrated Iodine 128 (non cyclotron produced), and the hyperplastic thyroid gland took up even more Iodine.  This was a GIANT step for Nuclear Medicine.

In early 1941, Dr. Hertz administer the first therapeutic treatment of MIT Markle Cyclotron produced radioactive iodine (RAI) at the Massachusetts General Hospital.  This  led to the first series of twenty-nine patients with hyperthyroidism being treated successfully with RAI. ( see “Research” RADIOACTIVE IODINE IN THE STUDY OF THYROID PHYSIOLOGY VII The use of Radioactive Iodine Therapy in Hyperthyroidism, Saul Hertz and Arthur Roberts, JAMA Vol. 31 Number 2).

In 1937, at the time of the rabbit studies Dr Hertz conceived of RAI in therapeutic treatment of thyroid carsonoma.  In 1942 Dr Hertz gave clinical trials of RAI to patients with thyroid carcinoma.

After serving in the Navy during World War II, Dr. Hertz wrote to the director of the Mass General Hospital in Boston, Dr. Paxon on March 12, 1946, “it is a coincidence that my new research project is in Cancer of the Thyroid, which I believe holds the key to the larger problem of cancer in general.”

Dr. Hertz established the Radioactive Isotope Research Institute, in September, 1946 with a major focus on the use of fission products for the treatment of thyroid cancer, goiter, and other malignant tumors. Dr Samuel Seidlin was the Associate Director and managed the New York City facilities. Hertz also researched the influence of hormones on cancer.

Dr. Hertz’s use of radioactive iodine as a tracer in the diagnostic process, as a treatment for Graves’ disease and in the treatment of cancer of the thyroid remain preferred practices. Saul Hertz is the Father of Theranostics.

Saul Hertz passed at 45 years old from a sudden death heart attack as documented by an autopsy. He leaves an enduring legacy impacting countless generations of patients, numerous institutions worldwide and setting the cornerstone for the field of Nuclear Medicine. A cancer survivor emailed, The cure delivered on the wings of prayer was Dr Saul Hertz’s discovery, the miracle of radioactive iodine. Few can equal such a powerful and precious gift. 

To read and hear more about Dr. Hertz and the early history of RAI in diagnosing and treating thyroid diseases and theranostics see –



   References in https://www.wjnm.org/article.asp?issn=1450-1147;year=2019;volume=18;issue=1;spage=8;epage=12;aulast=Hertz




Hertz S, Roberts A. Radioactive iodine in the study of thyroid physiology. VII The use of radioactive iodine therapy in hyperthyroidism. J Am Med Assoc 1946;131:81-6.  Back to cited text no. 1
Hertz S. A plan for analysis of the biologic factors involved in experimental carcinogenesis of the thyroid by means of radioactive isotopes. Bull New Engl Med Cent 1946;8:220-4.  Back to cited text no. 2
Thrall J. The Story of Saul Hertz, Radioiodine and the Origins of Nuclear Medicine. Available from: http://www.youtube.com/watch?v=34Qhm8CeMuc. [Last accessed on 2018 Dec 01].  Back to cited text no. 3
Braverman L. 131 Iodine Therapy: A Brief History. Available from: http://www.am2016.aace.com/presentations/friday/F12/hertz_braverman.pdf. [Last accessed on 2018 Dec 01].  Back to cited text no. 4
Hofman MS, Violet J, Hicks RJ, Ferdinandus J, Thang SP, Akhurst T, et al. [177Lu]-PSMA-617 radionuclide treatment in patients with metastatic castration-resistant prostate cancer (LuPSMA trial): A single-centre, single-arm, phase 2 study. Lancet Oncol 2018;19:825-33.  Back to cited text no. 5
Krolicki L, Morgenstern A, Kunikowska J, Koiziar H, Krolicki B, Jackaniski M, et al. Glioma Tumors Grade II/III-Local Alpha Emitters Targeted Therapy with 213 Bi-DOTA-Substance P, Endocrine Abstracts. Vol. 57. Society of Nuclear Medicine and Molecular Imaging; 2016. p. 632.  Back to cited text no. 6
Baum RP, Kulkarni HP. Duo PRRT of neuroendocrine tumours using concurrent and sequential administration of Y-90- and Lu-177-labeled somatostatin analogues. In: Hubalewska-Dydejczyk A, Signore A, de Jong M, Dierckx RA, Buscombe J, Van de Wiel CJ, editors. Somatostatin Analogues from Research to Clinical Practice. New York: Wiley; 2015.  Back to cited text no. 7



From: htziev@aol.com” <htziev@aol.com>

Reply-To: htziev@aol.com” <htziev@aol.com>

Date: Tuesday, March 2, 2021 at 11:04 AM

To: “Aviva Lev-Ari, PhD, RN” <AvivaLev-Ari@alum.berkeley.edu>

Subject: Dr Saul Hertz : Discovery for the Medical Uses of RADIOIODINE (RAI) MARCH 31ST: 80 Years


Other related articles published in this Open Access Online Scientific Journal include the following:


Experience with Thyroid Cancer

Author: Larry H. Bernstein, MD, FCAP



New Guidelines and Meeting Information on Advanced Thyroid Cancer as Reported by Cancer Network (Meeting Highlights)

Reporter: Stephen J. Williams, Ph.D.


The Experience of a Patient with Thyroid Cancer

Interviewer and Curator: Larry H Bernstein, MD, FCAP



Parathyroids and Bone Metabolism

Writer and Curator: Larry H. Bernstein, MD, FCAP



Thyroid Function and Disorders

Writer and Curator: Larry H. Bernstein, MD, FCAP


Summary and Perspectives: Impairments in Pathological States: Endocrine Disorders, Stress Hypermetabolism and Cancer

Author and Curator: Larry H. Bernstein, MD, FCAP


Introduction to Impairments in Pathological States: Endocrine Disorders, Stress Hypermetabolism and Cancer

Author and Curator: Larry H. Bernstein, MD, FCAP


Metformin, Thyroid-Pituitary Axis, Diabetes Mellitus, and Metabolism

Larry H, Bernstein, MD, FCAP, Author and Curator
and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/9/27/2014/Metformin,_thyroid-pituitary_ axis,_diabetes_mellitus,_and_metabolism

Autophagy-Modulating Proteins and Small Molecules Candidate Targets for Cancer Therapy: Commentary of Bioinformatics Approaches

Author and Curator: Larry H Bernstein, MD, FCAP and Article Architect: Aviva Lev-Ari, PhD, RN



Neural Activity Regulating Endocrine Response

Writer and Curator: Larry H. Bernstein, MD, FCAP



Pituitary Neuroendocrine Axis

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On the Influence of Hormones on Cancer

VOLUME 4: Human Reproductive System, Genomic Endocrinology and Cancer Types

(Series D: BioMedicine & Immunology) Kindle Edition. On Amazon.com  since February 2, 2021


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Lesson 6 of Cell Signaling & Motility – Cytoskeleton II: #TUBiol3373

Stephen J. Williams, Ph.D.

In this lesson we will go over the biochemical makeup and formation of various actin containing cellular structures involved in cellular motility, structure, as well as the dynamics of muscular contraction.  The lesson had been put on your Canvas and I am emailing you the Google Docs version.  If you are having problems downloading you can download here (I believe maybe the Canvas version had problems with embedding videos properly so that is why I am sending you also by email)

Download Below

cell signaling 6 lesson 2020

After opening the powerpoint (or Google Doc) please review with the following notes which highlight some concepts as well as some reviews and reminders of past lectures.  It may be handy to also have lecture 5 handy if you need to refer to it.  In between some sections there will be polls (really multiple choice quizzes DON’T WORRY you will not be graded on them but they are for your benefit.  There will also be a section under Comments all the way at the end and at the last quiz where you can also ask questions.

Remember you can always email me or Tweet me any questions @StephenJWillia2 using the hashtag #TUBiol3373.

In addition you can also leave comments at the very bottom which can be answered.

Slide 2 of lesson 6 is a refresher of the end of our last lecture, talking about Actin Binding Regulatory Proteins.



















The picture above shows a brief review of some of the structures and actin binding proteins involved in helping to form these actin filament structures (like filamin in cross linked structures, profilin which binds the actin monomers [G-actin] and helps with addition of these monomers to the leading plus end.

*** Remember G-actin (Globular Actin) is the monomer and F-actin (filamentious actin) is the polymerized actin strand [filament]

Also remember from the last lecture that G-Actin as monomer has affinity for ATP {Adenosine triphosphate} and these G-Actin-ATP will be able to polymerize to form the F-Actin form.  Also F-actin can then hydrolyze the ATP to ADP and inorganic phosphate.  At this point the actin-ADP unit looses affinity for the remaining F-Actin chain and depolymerization can occur


An event referred to as TREADMILLING or when the G actin units are removed from minus end and added to the plus (or growing barbed) end

Also remember that there is a critical concentration of G-Actin-ATP needed for bypassing the lag phase of nucleation before the elongation phase and the rate of addition to the plus end is faster than addition to minus end and greater than the rate of depolymerization at the minus end

Cell Structures That Involve Actin (see links for more information)

  1. filopodia
  2. parallel actin bundles
  3. actin cortex
  4. lamellipodia
  5. stress fibers
  6. microvilli
  7. contractile ring in cytokinesis



















Nucleating proteins Arp (actin related protein and Formins

Arp ====> formation of lamellipodia

Formins ====> formation of stress fibers

Process involving formins starts with a signaling event by activation of a G-protein, the GTP binding protein Rho

Rho is a subfamily member of the Ras superfamily.  The Rho family consists of cdc42, rac1, and RhoA (we will discuss at a later date).  Rho acts like G proteins, as a molecular switch.

Note that just like the Ras member of G-proteins and the Ras GTP/GDP cycle, the Rho activation, deactivation cycle also depends on GEFs [Guanine nucleotide exchange factors] and GAPs [GTPase activating proteins] and also GDIs [guanine nucleotide dissociation inhibitors which we will discuss later but involved in preventing Rho diffusion in the cell, acting as a tether].

Myosin and Motor (muscle) Function; Neuromuscular junctions, the sarcoplasmic reticulum and Ohhh the plethora of signaling events

In this section, from slides 29 to 54, we talk about myosin and the interactions between myosin and actin in formation of the contractile unit of the muscle (skeletal).

We also talk about some familiar signaling events, in particular the neuromuscular junction.

At this junction is a special type of acetylcholine receptor

Remember we talked about two types of acetylcholine receptors:

  1. muscarinic receptors – typical GPCRs that tranduce the signal via Gi or Gq depending on the muscarinic subtype
  2. nicotinic receptors – these are ligand {receptor} operated channels and when activated opens a Na+ channel which leads to depolarization


Now the depolarization activates another set of channels, the voltage operated calcium channels so we have two types of ion channels: Receptor {ligand} operated channels and Voltage operated channels.  These are sometimes abbreviated as ROCs and VOCs.

The unit of the myofibril on the contactile unit of the skeletal muscle is the sarcomere and upon the calcium transient, the sarcomere shortens with the two z-disks moving closer to each other as shown in the video in the lecture.

Also briefly review the introduction part on microtubules. We will finish that next week. Note that the microtubule is comprised of the protein tubulin, which is another GTP binding protein.

For other articles and more information please see

Lesson 5 Cell Signaling And Motility: Cytoskeleton & Actin: Curations and Articles of reference as supplemental information: #TUBiol3373

Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Identification of Biomarkers that are Related to the Actin Cytoskeleton










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Lesson 5 Cell Signaling And Motility: Cytoskeleton & Actin: Curations and Articles of reference as supplemental information: #TUBiol3373

Curator: Stephen J. Williams, Ph.D.

Cell motility or migration is an essential cellular process for a variety of biological events. In embryonic development, cells migrate to appropriate locations for the morphogenesis of tissues and organs. Cells need to migrate to heal the wound in repairing damaged tissue. Vascular endothelial cells (ECs) migrate to form new capillaries during angiogenesis. White blood cells migrate to the sites of inflammation to kill bacteria. Cancer cell metastasis involves their migration through the blood vessel wall to invade surrounding tissues.

Please Click on the Following Powerpoint Presentation for Lesson 4 on the Cytoskeleton, Actin, and Filaments


cell signaling 5 lesson

This post will be updated with further information when we get into Lesson 6 and complete our discussion on the Cytoskeleton

Please see the following articles on Actin and the Cytoskeleton in Cellular Signaling

Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

This article, constitutes a broad, but not complete review of the emerging discoveries of the critical role of calcium signaling on cell motility and, by extension, embryonic development, cancer metastasis, changes in vascular compliance at the junction between the endothelium and the underlying interstitial layer.  The effect of calcium signaling on the heart in arrhtmogenesis and heart failure will be a third in this series, while the binding of calcium to troponin C in the synchronous contraction of the myocardium had been discussed by Dr. Lev-Ari in Part I.

Universal MOTIFs essential to skeletal muscle, smooth muscle, cardiac syncytial muscle, endothelium, neovascularization, atherosclerosis and hypertension, cell division, embryogenesis, and cancer metastasis. The discussion will be presented in several parts:
1.  Biochemical and signaling cascades in cell motility
2.  Extracellular matrix and cell-ECM adhesions
3.  Actin dynamics in cell-cell adhesion
4.  Effect of intracellular Ca++ action on cell motility
5.  Regulation of the cytoskeleton
6.  Role of thymosin in actin-sequestration
7.  T-lymphocyte signaling and the actin cytoskeleton


Identification of Biomarkers that are Related to the Actin Cytoskeleton

In this article the Dr. Larry Bernstein covers two types of biomarker on the function of actin in cytoskeleton mobility in situ.

  • First, is an application in developing the actin or other component, for a biotarget and then, to be able to follow it as

(a) a biomarker either for diagnosis, or

(b) for the potential treatment prediction of disease free survival.

  • Second, is mostly in the context of MI, for which there is an abundance of work to reference, and a substantial body of knowledge about

(a) treatment and long term effects of diet, exercise, and

(b) underlying effects of therapeutic drugs.

Microtubule-Associated Protein Assembled on Polymerized Microtubules

(This article has a great 3D visualization of a microtuble structure as well as description of genetic diseases which result from mutations in tubulin and effects on intracellular trafficking of proteins.

A latticework of tiny tubes called microtubules gives your cells their shape and also acts like a railroad track that essential proteins travel on. But if there is a glitch in the connection between train and track, diseases can occur. In the November 24, 2015 issue of PNAS, Tatyana Polenova, Ph.D., Professor of Chemistry and Biochemistry, and her team at the University of Delaware (UD), together with John C. Williams, Ph.D., Associate Professor at the Beckman Research Institute of City of Hope in Duarte, California, reveal for the first time — atom by atom — the structure of a protein bound to a microtubule. The protein of focus, CAP-Gly, short for “cytoskeleton-associated protein-glycine-rich domains,” is a component of dynactin, which binds with the motor protein dynein to move cargoes of essential proteins along the microtubule tracks. Mutations in CAP-Gly have been linked to such neurological diseases and disorders as Perry syndrome and distal spinal bulbar muscular dystrophy.


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Lesson 4 Cell Signaling And Motility: G Proteins, Signal Transduction: Curations and Articles of reference as supplemental information: #TUBiol3373

Curator: Stephen J. Williams, Ph.D.

Updated 7/15/2019

Below please find the link to the Powerpoint presentation for lesson #4 for #TUBiol3373.  The lesson first competes the discussion on G Protein Coupled Receptors, including how cells terminate cell signals.  Included are mechanisms of receptor desensitization.  Please NOTE that desensitization mechanisms like B arrestin decoupling of G proteins and receptor endocytosis occur after REPEATED and HIGH exposures to agonist.  Hydrolysis of GTP of the alpha subunit of G proteins, removal of agonist, and the action of phosphodiesterase on the second messenger (cAMP or cGMP) is what results in the downslope of the effect curve, the termination of the signal after agonist-receptor interaction.


Click below for PowerPoint of lesson 4

Powerpoint for lesson 4


Please Click below for the papers for your Group presentations

paper 1: Membrane interactions of G proteins and other related proteins

paper 2: Macaluso_et_al-2002-Journal_of_Cellular_Physiology

paper 3: Interactions of Ras proteins with the plasma membrane

paper 4: Futosi_et_al-2016-Immunological_Reviews


Please find related article on G proteins and Receptor Tyrosine Kinases on this Open Access Online Journal

G Protein–Coupled Receptor and S-Nitrosylation in Cardiac Ischemia and Acute Coronary Syndrome

Action of Hormones on the Circulation

Newer Treatments for Depression: Monoamine, Neurotrophic Factor & Pharmacokinetic Hypotheses

VEGF activation and signaling, lysine methylation, and activation of receptor tyrosine kinase


Read Full Post »

Lesson 3 Cell Signaling & Motility: G Proteins, Signal Transduction: Curations and Articles of reference as supplemental information: #TUBiol3373

Curator: Stephen J. Williams, Ph.D.

Updated 7/15/2019

Lesson 3 Powerpoint (click link below):

cell signaling and motility 3 finalissima sjw

Four papers to choose from for your February 11 group presentation:

Structural studies of G protein Coupled receptor


G protein as target in neurodegerative disease

fish technique



Today’s lesson 3 explains how extracellular signals are transduced (transmitted) into the cell through receptors to produce an agonist-driven event (effect).  This lesson focused on signal transduction from agonist through G proteins (GTPases), and eventually to the effectors of the signal transduction process.  Agonists such as small molecules like neurotransmitters, hormones, nitric oxide were discussed however later lectures will discuss more in detail the large growth factor signalings which occur through receptor tyrosine kinases and the Ras family of G proteins as well as mechanosignaling through Rho and Rac family of G proteins.

Transducers: The Heterotrimeric G Proteins (GTPases)

An excellent review of heterotrimeric G Proteins found in the brain is given by

Heterotrimeric G Proteins by Eric J Nestler and Ronald S Duman.



from Seven-Transmembrane receptors – Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Examples-of-heterotrimeric-G-protein-effectors_tbl1_11180073 [accessed 4 Feb, 2019] and see references within



See below for the G Protein Cycle









<a href=”https://www.researchgate.net/figure/32-The-G-protein-cycle-In-the-absence-of-agonist-A-GPCRs-are-mainly-in-the-low_fig2_47933733″><img src=”https://www.researchgate.net/profile/Veli_Pekka_Jaakola/publication/47933733/figure/fig2/AS:669499451781133@1536632516635/32-The-G-protein-cycle-In-the-absence-of-agonist-A-GPCRs-are-mainly-in-the-low.ppm&#8221; alt=”.3.2: The G protein cycle. In the absence of agonist (A), GPCRs are mainly in the low affinity state (R). After agonist binding, the receptor is activated in the high affinity state (R*), and the agonist-GPCR-G protein complex is formed. GTP replaces GDP in Gα. After that the G protein dissociates into the Gα subunit and the Gβγ heterodimer, which then activate several effector proteins. The built-in GTPase activity of the Gα subunit cleaves the terminal phosphate group of GTP, and the GDP bound Gα subunit reassociates with Gβγ heterodimer. This results in the deactivation of both Gα and Gβγ. The G protein cycle returns to the basal state. RGS, regulator of G protein signalling.”/></a>


From Citation: Review: A. M. Preininger, H. E. Hamm, G protein signaling: Insights from new structures. Sci. STKE2004, re3 (2004)


For a tutorial on G Protein coupled receptors (GPCR) see





cyclic AMP (cAMP) signaling to the effector Protein Kinase A (PKA)

from https://courses.washington.edu/conj/gprotein/cyclicamp.htm

Cyclic AMP is an important second messenger. It forms, as shown, when the membrane enzyme adenylyl cyclase is activated (as indicated, by the alpha subunit of a G protein).


The cyclic AMP then goes on the activate specific proteins. Some ion channels, for example, are gated by cyclic AMP. But an especially important protein activated by cyclic AMP is protein kinase A, which goes on the phosphorylate certain cellular proteins. The scheme below shows how cyclic AMP activates protein kinase A.

Updated 7/15/2019

Additional New Studies on Regulation of the Beta 2 Adrenergic Receptor

We had discussed regulation of the G protein coupled beta 2 adrenergic receptor by the B-AR receptor kinase (BARK)/B arrestin system which uncouples and desensitizes the receptor from its G protein system.  In an article by Xiangyu Liu in Science in 2019, the authors describe another type of allosteric modulation (this time a POSITIVE allosteric modulation) in the intracellular loop 2.  See below:

Mechanism of β2AR regulation by an intracellular positive allosteric modulator

Xiangyu Liu1,*, Ali Masoudi2,*, Alem W. Kahsai2,*, Li-Yin Huang2, Biswaranjan Pani2Dean P. Staus2, Paul J. Shim2, Kunio Hirata3,4, Rishabh K. Simhal2, Allison M. Schwalb2, Paula K. Rambarat2, Seungkirl Ahn2, Robert J. Lefkowitz2,5,6,Brian Kobilka1

Positive reinforcement in a GPCR

Many drug discovery efforts focus on G protein–coupled receptors (GPCRs), a class of receptors that regulate many physiological processes. An exemplar is the β2-adrenergic receptor (β2AR), which is targeted by both blockers and agonists to treat cardiovascular and respiratory diseases. Most GPCR drugs target the primary (orthosteric) ligand binding site, but binding at allosteric sites can modulate activation. Because such allosteric sites are less conserved, they could possibly be targeted more specifically. Liu et al. report the crystal structure of β2AR bound to both an orthosteric agonist and a positive allosteric modulator that increases receptor activity. The structure suggests why the modulator compound is selective for β2AR over the closely related β1AR. Furthermore, the structure reveals that the modulator acts by enhancing orthosteric agonist binding and stabilizing the active conformation of the receptor.


Drugs targeting the orthosteric, primary binding site of G protein–coupled receptors are the most common therapeutics. Allosteric binding sites, elsewhere on the receptors, are less well-defined, and so less exploited clinically. We report the crystal structure of the prototypic β2-adrenergic receptor in complex with an orthosteric agonist and compound-6FA, a positive allosteric modulator of this receptor. It binds on the receptor’s inner surface in a pocket created by intracellular loop 2 and transmembrane segments 3 and 4, stabilizing the loop in an α-helical conformation required to engage the G protein. Structural comparison explains the selectivity of the compound for β2– over the β1-adrenergic receptor. Diversity in location, mechanism, and selectivity of allosteric ligands provides potential to expand the range of receptor drugs.


Recent structures of GPCRs bound to allosteric modulators have revealed that receptor surfaces are decorated with diverse cavities and crevices that may serve as allosteric modulatory sites (1). This substantiates the notion that GPCRs are structurally plastic and can be modulated by a variety of allosteric ligands through distinct mechanisms (2-7). Most of these structures have been solved with negative allosteric modulators (NAMs), which stabilize receptors in their inactive states (1). To date, only a single structure of an active GPCR bound to a small-molecule positive allosteric modulator (PAM) has been reported, namely, the M2 muscarinic acetylcholine receptor with LY2119620 (8). Thus, mechanisms of PAMs and their potential binding sites remain largely unexplored.



Fig 1. Structure of the active state T4L-B2AR in complex with the orthosteric agonist BI-167107, nanobody 689, and compound 6FA.  (A) The chemical structure of compound-6FA (Cmpd-6FA). (B) Isoproterenol (ISO) competition binding with 125I-cyanopindolol (CYP) to the β2AR reconstituted in nanodisks in the presence of vehicle (0.32% dimethylsulfoxide; DMSO), Cmpd-6, or Cmpd-6FA at 32 μM. Values were normalized to percentages of the maximal 125I-CYP binding level obtained from a one-site competition binding–log IC50 (median inhibitory concentration) curve fit. Binding curves were generated by GraphPad Prism. Points on curves represent mean ± SEM obtained from five independent experiments performed in duplicate. (C) Analysis of Cmpd-6FA interaction with the BI-167107–bound β2AR by ITC. Representative thermogram (inset) and binding isotherm, of three independent experiments, with the best titration curve fit are shown. Summary of thermodynamic parameters obtained by ITC: binding affinity (KD = 1.2 ± 0.1 μM), stoichiometry (N = 0.9 ± 0.1 sites), enthalpy (ΔH = 5.0 ± 1.2 kcal mol−1), and entropy (ΔS =13 ± 2.0 cal mol−1 deg−1). (D) Side view of T4L-β2AR bound to the orthosteric agonist BI-167107, nanobody 6B9 (Nb6B9), and Cmpd-6FA. The gray box indicates the membrane layer as defined by the OPM database. (E) Close-up view of Cmpd-6FA binding site. Covering Cmpd-6FA is 2Fo– Fc electron density contoured at 1.0 σ (green mesh).From Science  28 Jun 2019:
Vol. 364, Issue 6447, pp. 1283-1287



Fig 3. Fig. 3 Mechanism of allosteric activation of the β2AR by Cmpd-6FA.

(A) Superposition of the inactive β2AR bound to the antagonist carazolol (PDB code: 2RH1) and the active β2AR bound to the agonist BI-167107, Cmpd-6FA, and Nb6B9. Close-up view of the Cmpd-6FA binding site is shown. The residues of the inactive (yellow) and active (blue) β2AR are depicted, and the hydrogen bond formed between Asp1303.49and Tyr141ICL2 in the active state is indicated by a black dashed line. (B) Topography of Cmpd-6FA binding surface on the active β2AR (left, blue) and the corresponding surface of the inactive β2AR (right, yellow) with Cmpd-6FA (orange sticks) docked on top. Molecular surfaces are of only those residues involved in interaction with Cmpd-6FA. Steric clash between Cmpd-6FA and the surface of inactive β2AR is represented by a purple asterisk. (C) Overlay of the β2AR bound to BI-167107, Nb6B9, and Cmpd-6FA with the β2AR–Gscomplex (PDB code: 3SN6). The inset shows the position of Phe139ICL2 relative to the α subunit of Gs. (D) Superposition of the active β2AR bound to the agonist BI-167107, Nb6B9, and Cmpd-6FA (blue) with the inactive β2AR bound to carazolol (yellow) (PDB code: 2RH1) as viewed from the cytoplasm. For clarity, Nb6B9 and the orthosteric ligands are omitted. The arrows indicate shifts in the intracellular ends of the TM helices 3, 5, and 6 upon activation and their relative distances.





Allosteric sites may not face the same evolutionary pressure as do orthosteric sites, and thus are more divergent across subtypes within a receptor family (2426). Therefore, allosteric sites may provide a greater source of specificity for targeting GPCRs.



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Additional information on Nitric Oxide as a Cellular Signal

Nitric oxide is actually a free radical and can react with other free radicals, resulting in a very short half life (only a few seconds) and so in the body is produced locally to its site of action (i.e. in endothelial cells surrounding the vascular smooth muscle, in nerve cells). In the late 1970s, Dr. Robert Furchgott observed that acetylcholine released a substance that produced vascular relaxation, but only when the endothelium was intact. This observation opened this field of research and eventually led to his receiving a Nobel prize. Initially, Furchgott called this substance endothelium-derived relaxing factor (EDRF), but by the mid-1980s he and others identified this substance as being NO.

Nitric oxide is produced from metabolism of endogenous substances like L-arginine, catalyzed by one of three isoforms of nitric oxide synthase (for link to a good article see here) or release from exogenous compounds like drugs used to treat angina pectoris like amyl nitrate or drugs used for hypertension such as sodium nitroprusside.

The following articles are a great reference to the chemistry, and physiological and pathological Roles of Nitric Oxide:

46. The Molecular Biology of Renal Disorders: Nitric Oxide – Part III

Curator and Author: Larry H Bernstein, MD, FACP


47. Nitric Oxide Function in Coagulation – Part II

Curator and Author: Larry H. Bernstein, MD, FCAP


48. Nitric Oxide, Platelets, Endothelium and Hemostasis

Curator and Author: Larry H Bernstein, MD, FACP


49. Interaction of Nitric Oxide and Prostacyclin in Vascular Endothelium

Curator and Author: Larry H Bernstein, MD, FACP


50. Nitric Oxide and Immune Responses: Part 1

Curator and Author:  Aviral Vatsa PhD, MBBS


51. Nitric Oxide and Immune Responses: Part 2

Curator and Author:  Aviral Vatsa PhD, MBBS


56. Nitric Oxide and iNOS have Key Roles in Kidney Diseases – Part II

Curator and Author: Larry H Bernstein, MD, FACP


57. New Insights on Nitric Oxide donors – Part IV

Curator and Author: Larry H Bernstein, MD, FACP


59. Nitric Oxide has a ubiquitous role in the regulation of glycolysis -with a concomitant influence on mitochondrial function

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/09/16/nitric-oxide-has-a-ubiquitous-role-in-the-regulation-of-glycolysis-with-         a-concomitant-influence-on-mitochondrial-function/

Biochemistry of the Coagulation Cascade and Platelet Aggregation: Nitric Oxide: Platelets, Circulatory Disorders, and Coagulation Effects

Nitric Oxide Function in Coagulation – Part II

Nitric oxide is implicated in many pathologic processes as well.  Nitric oxide post translational modifications have been attributed to nitric oxide’s role in pathology however, although the general mechanism by which nitric oxide exerts its physiological effects is by stimulation of soluble guanylate cyclase to produce cGMP, these post translational modifications can act as a cellular signal as well.  For more information of NO pathologic effects and how NO induced post translational modifications can act as a cellular signal see the following:

Nitric Oxide Covalent Modifications: A Putative Therapeutic Target?

58. Crucial role of Nitric Oxide in Cancer

Curator and Author: Ritu Saxena, Ph.D.


Note:  A more comprehensive ebook on Nitric Oxide and Disease Perspectives is found at

Cardiovascular Diseases, Volume One: Perspectives on Nitric Oxide in Disease Mechanisms

available on Kindle Store @ Amazon.com


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Lesson 9 Cell Signaling:  Curations and Articles of reference as supplemental information for lecture section on WNTs: #TUBiol3373

Stephen J. Wiilliams, Ph.D: Curator

UPDATED 4/23/2019

This has an updated lesson on WNT signaling.  Please click on the following and look at the slides labeled under lesson 10

cell motility 9b lesson_2018_sjw

Remember our lessons on the importance of signal termination.  The CANONICAL WNT signaling (that is the β-catenin dependent signaling)

is terminated by the APC-driven degradation complex.  This leads to the signal messenger  β-catenin being degraded by the proteosome.  Other examples of growth factor signaling that is terminated by a proteosome-directed include the Hedgehog signaling system, which is involved in growth and differentiation as well as WNTs and is implicated in various cancers.

A good article on the Hedgehog signaling pathway is found here:

The Voice of a Pathologist, Cancer Expert: Scientific Interpretation of Images: Cancer Signaling Pathways and Tumor Progression

All images in use for this article are under copyrights with Shutterstock.com

Cancer is expressed through a series of transformations equally involving metabolic enzymes and glucose, fat, and protein metabolism, and gene transcription, as a result of altered gene regulatory and transcription pathways, and also as a result of changes in cell-cell interactions.  These are embodied in the following series of graphics.

Figure 1: Sonic_hedgehog_pathwaySonic_hedgehog_pathway

The Voice of Dr. Larry

The figure shows a modification of nuclear translocation by Sonic hedgehog pathway. The hedgehog proteins have since been implicated in the development of internal organs, midline neurological structures, and the hematopoietic system in humans. The Hh signaling pathway consists of three main components: the receptor patched 1 (PTCH1), the seven transmembrane G-protein coupled receptor smoothened (SMO), and the intracellular glioma-associated oncogene homolog (GLI) family of transcription factors.5The GLI family is composed of three members, including GLI1 (gene activating), GLI2 (gene activating and repressive), and GLI3 (gene repressive).6 In the absence of an activating signal from either Shh, Ihh or Dhh, PTCH1 exerts an inhibitory effect on the signal transducer SMO, preventing any downstream signaling from occurring.7 When Hh ligands bind and activate PTCH1, the inhibition on SMO is released, allowing the translocation of SMO into the cytoplasm and its subsequent activation of the GLI family of transcription factors.


And from the review of  Elaine Y. C. HsiaYirui Gui, and Xiaoyan Zheng   Regulation of Hedgehog Signaling by Ubiquitination  Front Biol (Beijing). 2015 Jun; 10(3): 203–220.

the authors state:

Finally, termination of Hh signaling is also important for controlling the duration of pathway activity. Hh induced ubiquitination and degradation of Ci/Gli is the most well-established mechanism for limiting signal duration, and inhibiting this process can lead to cell patterning disruption and excessive cell proliferation (). In addition to Ci/Gli, a growing body of evidence suggests that ubiquitination also plays critical roles in regulating other Hh signaling components including Ptc, Smo, and Sufu. Thus, ubiquitination serves as a general mechanism in the dynamic regulation of the Hh pathway.

Overview of Hedgehog signaling showing the signal termination by ubiquitnation and subsequent degradation of the Gli transcriptional factors. obtained from Oncotarget 5(10):2881-911 · May 2014. GSK-3B as a Therapeutic Intervention in Cancer


















Note that in absence of Hedgehog ligands Ptch inhibits Smo accumulation and activation but upon binding of Hedgehog ligands (by an autocrine or paracrine fashion) Ptch is now unable to inhibit Smo (evidence exists that Ptch is now targeted for degradation) and Smo can now inhibit Sufu-dependent and GSK-3B dependent induced degradation of Gli factors Gli1 and Gli2.  Also note the Gli1 and Gli2 are transcriptional activators while Gli3 is a transcriptional repressor.

UPDATED 4/16/2019

Please click on the following links for the Powerpoint presentation for lesson 9.  In addition click on the mp4 links to download the movies so you can view them in Powerpoint slide 22:

cell motility 9 lesson_SJW 2019

movie file 1:

Tumorigenic but noninvasive MCF-7 cells motility on an extracellular matrix derived from normal (3DCntrol) or tumor associated (TA) fibroblasts.  Note that TA ECM is “soft” and not organized and tumor cells appear to move randomly if  much at all.

Movie 2:


Note that these tumorigenic and invasive MDA-MB-231 breast cancer cells move in organized patterns on organized ECM derived from Tumor Associated (TA) fibroblasts than from the ‘soft’ or unorganized ECM derived from normal  (3DCntrl) fibroblasts


The following contain curations of scientific articles from the site https://pharmaceuticalintelligence.com  intended as additional reference material  to supplement material presented in the lecture.

Wnts are a family of lipid-modified secreted glycoproteins which are involved in:

Normal physiological processes including

A. Development:

– Osteogenesis and adipogenesis (Loss of wnt/β‐catenin signaling causes cell fate shift of preosteoblasts from osteoblasts to adipocytes)

  – embryogenesis including body axis patterning, cell fate specification, cell proliferation and cell migration

B. tissue regeneration in adult tissue

read: Wnt signaling in the intestinal epithelium: from endoderm to cancer

And in pathologic processes such as oncogenesis (refer to Wnt/β-catenin Signaling [7.10]) and to your Powerpoint presentation


The curation Wnt/β-catenin Signaling is a comprehensive review of canonical and noncanonical Wnt signaling pathways


To review:












Activating the canonical Wnt pathway frees B-catenin from the degradation complex, resulting in B-catenin translocating to the nucleus and resultant transcription of B-catenin/TCF/LEF target genes.

Fig. 1 Canonical Wnt/FZD signaling pathway. (A) In the absence of Wnt signaling, soluble β-catenin is phosphorylated by a degradation complex consisting of the kinases GSK3β and CK1α and the scaffolding proteins APC and Axin1. Phosphorylated β-catenin is targeted for proteasomal degradation after ubiquitination by the SCF protein complex. In the nucleus and in the absence of β-catenin, TCF/LEF transcription factor activity is repressed by TLE-1; (B) activation of the canonical Wnt/FZD signaling leads to phosphorylation of Dvl/Dsh, which in turn recruits Axin1 and GSK3β adjacent to the plasma membrane, thus preventing the formation of the degradation complex. As a result, β-catenin accumulates in the cytoplasm and translocates into the nucleus, where it promotes the expression of target genes via interaction with TCF/LEF transcription factors and other proteins such as CBP, Bcl9, and Pygo.

NOTE: In the canonical signaling, the Wnt signal is transmitted via the Frizzled/LRP5/6 activated receptor to INACTIVATE the degradation complex thus allowing free B-catenin to act as the ultimate transducer of the signal.

Remember, as we discussed, the most frequent cancer-related mutations of WNT pathway constituents is in APC.

This shows how important the degradation complex is in controlling canonical WNT signaling.

Other cell signaling systems are controlled by protein degradation:

A.  The Forkhead family of transcription factors

Read: Regulation of FoxO protein stability via ubiquitination and proteasome degradation

B. Tumor necrosis factor α/NF κB signaling

Read: NF-κB, the first quarter-century: remarkable progress and outstanding questions

1.            Question: In cell involving G-proteins, the signal can be terminated by desensitization mechanisms.  How is both the canonical and noncanonical Wnt signal eventually terminated/desensitized?

We also discussed the noncanonical Wnt signaling pathway (independent of B-catenin induced transcriptional activity).  Note that the canonical and noncanonical involve different transducers of the signal.

Noncanonical WNT Signaling

Note: In noncanonical signaling the transducer is a G-protein and second messenger system is IP3/DAG/Ca++ and/or kinases such as MAPK, JNK.

Depending on the different combinations of WNT ligands and the receptors, WNT signaling activates several different intracellular pathways  (i.e. canonical versus noncanonical)


In addition different Wnt ligands are expressed at different times (temporally) and different cell types in development and in the process of oncogenesis. 

The following paper on Wnt signaling in ovarian oncogenesis shows how certain Wnt ligands are expressed in normal epithelial cells but the Wnt expression pattern changes upon transformation and ovarian oncogenesis. In addition, differential expression of canonical versus noncanonical WNT ligands occur during the process of oncogenesis (for example below the authors describe the noncanonical WNT5a is expressed in normal ovarian  epithelia yet WNT5a expression in ovarian cancer is lower than the underlying normal epithelium. However the canonical WNT10a, overexpressed in ovarian cancer cells, serves as an oncogene, promoting oncogenesis and tumor growth.

Wnt5a Suppresses Epithelial Ovarian Cancer by Promoting Cellular Senescence

Benjamin G. Bitler,1 Jasmine P. Nicodemus,1 Hua Li,1 Qi Cai,2 Hong Wu,3 Xiang Hua,4 Tianyu Li,5 Michael J. Birrer,6Andrew K. Godwin,7 Paul Cairns,8 and Rugang Zhang1,*

A.           Abstract

Epithelial ovarian cancer (EOC) remains the most lethal gynecological malignancy in the US. Thus, there is an urgent need to develop novel therapeutics for this disease. Cellular senescence is an important tumor suppression mechanism that has recently been suggested as a novel mechanism to target for developing cancer therapeutics. Wnt5a is a non-canonical Wnt ligand that plays a context-dependent role in human cancers. Here, we investigate the role of Wnt5a in regulating senescence of EOC cells. We demonstrate that Wnt5a is expressed at significantly lower levels in human EOC cell lines and in primary human EOCs (n = 130) compared with either normal ovarian surface epithelium (n = 31; p = 0.039) or fallopian tube epithelium (n = 28; p < 0.001). Notably, a lower level of Wnt5a expression correlates with tumor stage (p = 0.003) and predicts shorter overall survival in EOC patients (p = 0.003). Significantly, restoration of Wnt5a expression inhibits the proliferation of human EOC cells both in vitro and in vivo in an orthotopic EOC mouse model. Mechanistically, Wnt5a antagonizes canonical Wnt/β-catenin signaling and induces cellular senescence by activating the histone repressor A (HIRA)/promyelocytic leukemia (PML) senescence pathway. In summary, we show that loss of Wnt5a predicts poor outcome in EOC patients and Wnt5a suppresses the growth of EOC cells by triggering cellular senescence. We suggest that strategies to drive senescence in EOC cells by reconstituting Wnt5a signaling may offer an effective new strategy for EOC therapy.

Oncol Lett. 2017 Dec;14(6):6611-6617. doi: 10.3892/ol.2017.7062. Epub 2017 Sep 26.

Clinical significance and biological role of Wnt10a in ovarian cancer. 

Li P1Liu W1Xu Q1Wang C1.

Ovarian cancer is one of the five most malignant types of cancer in females, and the only currently effective therapy is surgical resection combined with chemotherapy. Wnt family member 10A (Wnt10a) has previously been identified to serve an oncogenic function in several tumor types, and was revealed to have clinical significance in renal cell carcinoma; however, there is still only limited information regarding the function of Wnt10a in the carcinogenesis of ovarian cancer. The present study identified increased expression levels of Wnt10a in two cell lines, SKOV3 and A2780, using reverse transcription-polymerase chain reaction. Functional analysis indicated that the viability rate and migratory ability of SKOV3 cells was significantly inhibited following Wnt10a knockdown using short interfering RNA (siRNA) technology. The viability rate of SKOV3 cells decreased by ~60% compared with the control and the migratory ability was only ~30% of that in the control. Furthermore, the expression levels of β-catenin, transcription factor 4, lymphoid enhancer binding factor 1 and cyclin D1 were significantly downregulated in SKOV3 cells treated with Wnt10a-siRNA3 or LGK-974, a specific inhibitor of the canonical Wnt signaling pathway. However, there were no synergistic effects observed between Wnt10a siRNA3 and LGK-974, which indicated that Wnt10a activated the Wnt/β-catenin signaling pathway in SKOV3 cells. In addition, using quantitative PCR, Wnt10a was overexpressed in the tumor tissue samples obtained from 86 patients with ovarian cancer when compared with matching paratumoral tissues. Clinicopathological association analysis revealed that Wnt10a was significantly associated with high-grade (grade III, P=0.031) and late-stage (T4, P=0.008) ovarian cancer. Furthermore, the estimated 5-year survival rate was 18.4% for patients with low Wnt10a expression levels (n=38), whereas for patients with high Wnt10a expression (n=48) the rate was 6.3%. The results of the present study suggested that Wnt10a serves an oncogenic role during the carcinogenesis and progression of ovarian cancer via the Wnt/β-catenin signaling pathway.

Targeting the Wnt Pathway includes curations of articles related to the clinical development of Wnt signaling inhibitors as a therapeutic target in various cancers including hepatocellular carcinoma, colon, breast and potentially ovarian cancer.


2.         Question: Given that different Wnt ligands and receptors activate different signaling pathways, AND  WNT ligands  can be deferentially and temporally expressed  in various tumor types and the process of oncogenesis, how would you approach a personalized therapy targeting the WNT signaling pathway?

3.         Question: What are the potential mechanisms of either intrinsic or acquired resistance to Wnt ligand antagonists being developed?


Other related articles published in this Open Access Online Scientific Journal include the following:

Targeting the Wnt Pathway [7.11]

Wnt/β-catenin Signaling [7.10]

Cancer Signaling Pathways and Tumor Progression: Images of Biological Processes in the Voice of a Pathologist Cancer Expert

e-Scientific Publishing: The Competitive Advantage of a Powerhouse for Curation of Scientific Findings and Methodology Development for e-Scientific Publishing – LPBI Group, A Case in Point 

Electronic Scientific AGORA: Comment Exchanges by Global Scientists on Articles published in the Open Access Journal @pharmaceuticalintelligence.com – Four Case Studies


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Colon cancer and organoids

Larry H. Bernstein, MD, FCAP, Curator





Guts and Glory

An open mind and collaborative spirit have taken Hans Clevers on a journey from medicine to developmental biology, gastroenterology, cancer, and stem cells.

By Anna Azvolinsky    http://www.the-scientist.com/?articles.view/articleNo/45580/title/Guts-and-Glory

Ihave had to talk a lot about my science recently and it’s made me think about how science works,” says Hans Clevers. “Scientists are trained to think science is driven by hypotheses, but for [my lab], hypothesis-driven research has never worked. Instead, it has been about trying to be as open-minded as possible—which is not natural for our brains,” adds the Utrecht University molecular genetics professor. “The human mind is such that it tries to prove it’s right, so pursuing a hypothesis can result in disaster. My advice to my own team and others is to not preformulate an answer to a scientific question, but just observe and never be afraid of the unknown. What has worked well for us is to keep an open mind and do the experiments. And find a collaborator if it is outside our niche.”

“One thing I have learned is that hypothesis-driven research tends not to be productive when you are in an unknown territory.”

Clevers entered medical school at Utrecht University in The Netherlands in 1978 while simultaneously pursuing a master’s degree in biology. Drawn to working with people in the clinic, Clevers had a training position in pediatrics lined up after medical school, but then mentors persuaded him to spend an additional year converting the master’s degree to a PhD in immunology. “At the end of that year, looking back, I got more satisfaction from the research than from seeing patients.” Clevers also had an aptitude for benchwork, publishing four papers from his PhD year. “They were all projects I had made up myself. The department didn’t do the kind of research I was doing,” he says. “Now that I look back, it’s surprising that an inexperienced PhD student could come up with a project and publish independently.”

Clevers studied T- and B-cell signaling; he set up assays to visualize calcium ion flux and demonstrated that the ions act as messengers to activate human B cells, signaling through antibodies on the cell surface. “As soon as the experiment worked, I got T cells from the lab next door and did the same experiment. That was my strategy: as soon as something worked, I would apply it elsewhere and didn’t stop just because I was a B-cell biologist and not a T-cell biologist. What I learned then, that I have continued to benefit from, is that a lot of scientists tend to adhere to a niche. They cling to these niches and are not that flexible. You think scientists are, but really most are not.”

Here, Clevers talks about promoting a collaborative spirit in research, the art of doing a pilot experiment, and growing miniature organs in a dish.

Clevers Creates

Re-search? Clevers was born in Eindhoven, in the south of The Netherlands. The town was headquarters to Philips Electronics, where his father worked as a businessman, and his mother took care of Clevers and his three brothers. Clevers did well in school but his passion was sports, especially tennis and field hockey, “a big thing in Holland.” Then in 1975, at age 18, he moved to Utrecht University, where he entered an intensive, biology-focused program. “I knew I wanted to be a biology researcher since I was young. In Dutch, the word for research is ‘onderzoek’ and I knew the English word ‘research’ and had wondered why there was the ‘re’ in the word, because I wanted to search but I didn’t want to do re-search—to find what someone else had already found.”

Opportunity to travel. “I was very disappointed in my biology studies, which were old-fashioned and descriptive,” says Clevers. He thought medicine might be more interesting and enrolled in medical school while still pursuing a master’s degree in biology at Utrecht. For the master’s, Clevers had to do three rotations. He spent a year at the International Laboratory for Research on Animal Diseases (ILRAD) in Nairobi, Kenya, and six months in Bethesda, Maryland, at the National Institutes of Health. “Holland is really small, so everyone travels.” Clevers saw those two rotations more as travel explorations. In Nairobi, he went on safaris and explored the country in Land Rovers borrowed from the institute. While in Maryland in 1980, Clevers—with the consent of his advisor, who thought it was a good idea for him to get a feel for the U.S.—flew to Portland, Oregon, and drove back to Boston with a musician friend along the Canadian border. He met the fiancé of political activist and academic Angela Davis in New York City and even stayed in their empty apartment there.

Life and lab lessons. Back in Holland, Clevers joined Rudolf Eugène Ballieux’s lab at Utrecht University to pursue his PhD, for which he studied immune cell signaling. “I didn’t learn much science from him, but I learned that you always have to create trust and to trust people around you. This became a major theme in my own lab. We don’t distrust journals or reviewers or collaborators. We trust everyone and we share. There will be people who take advantage, but there have only been a few of those. So I learned from Ballieux to give everyone maximum trust and then change this strategy only if they fail that trust. We collaborate easily because we give out everything and we also easily get reagents and tools that we may need. It’s been valuable to me in my career. And it is fun!”

Clevers Concentrates

On a mission. “Once I decided to become a scientist, I knew I needed to train seriously. Up to that point, I was totally self-trained.” From an extensive reading of the immunology literature, Clevers became interested in how T cells recognize antigens, and headed off to spend a postdoc studying the problem in Cox Terhorst’s lab at Dana-Farber Cancer Institute in Boston. “Immunology was young, but it was very exciting and there was a lot to discover. I became a professional scientist there and experienced how tough science is.” In 1988, Clevers cloned and characterized the gene for a component of the T-cell receptor (TCR) called CD3-epsilon, which binds antigen and activates intracellular signaling pathways.

On the fast track in Holland. Clevers returned to Utrecht University in 1989 as a professor of immunology. Within one month of setting up his lab, he had two graduate students and a technician, and the lab had cloned the first T cell–specific transcription factor, which they called TCF-1, in human T cells. When his former thesis advisor retired, Clevers was asked, at age 33, to become head of the immunology department. While the appointment was high-risk for him and for the department, Clevers says, he was chosen because he was good at multitasking and because he got along well with everyone.

Problem-solving strategy. “My strategy in research has always been opportunistic. One thing I have learned is that hypothesis-driven research tends not to be productive when you are in an unknown territory. I think there is an art to doing pilot experiments. So we have always just set up systems in which something happens and then you try and try things until a pattern appears and maybe you formulate a small hypothesis. But as soon as it turns out not to be exactly right, you abandon it. It’s a very open-minded type of research where you question whether what you are seeing is a real phenomenon without spending a year on doing all of the proper controls.”

Trial and error. Clevers’s lab found that while TCF-1 bound to DNA, it did not alter gene expression, despite the researchers’ tinkering with promoter and enhancer assays. “For about five years this was a problem. My first PhD students were leaving and they thought the whole TCF project was a failure,” says Clevers. His lab meanwhile cloned TCF homologs from several model organisms and made many reagents including antibodies against these homologs. To try to figure out the function of TCF-1, the lab performed a two-hybrid screen and identified components of the Wnt signaling pathway as binding partners of TCF-1. “We started to read about Wnt and realized that you study Wnt not in T cells but in frogs and flies, so we rapidly transformed into a developmental biology lab. We showed that we held the key for a major issue in developmental biology, the final protein in the Wnt cascade: TCF-1 binds b-catenin when b-catenin becomes available and activates transcription.” In 1996, Clevers published the mechanism of how the TCF-1 homolog in Xenopus embryos, called XTcf-3, is integrated into the Wnt signaling pathway.

Clevers Catapults


3DCrypt building and colon cancer.

Clevers next collaborated with Bert Vogelstein’s lab at Johns Hopkins, linking TCF to Wnt signaling in colon cancer. In colon cancer cell lines with mutated forms of the tumor suppressor gene APC, the APC protein can’t rein in b-catenin, which accumulates in the cytoplasm, forms a complex with TCF-4 (later renamed TCF7L2) in the nucleus, and caninitiate colon cancer by changing gene expression. Then, the lab showed that Wnt signaling is necessary for self-renewal of adult stem cells, as mice missing TCF-4 do not have intestinal crypts, the site in the gut where stem cells reside. “This was the first time Wnt was shown to play a role in adults, not just during development, and to be crucial for adult stem cell maintenance,” says Clevers. “Then, when I started thinking about studying the gut, I realized it was by far the best way to study stem cells. And I also realized that almost no one in the world was studying the healthy gut. Almost everyone who researched the gut was studying a disease.” The main advantages of the murine model are rapid cell turnover and the presence of millions of stereotypic crypts throughout the entire intestine.

Against the grain. In 2007, Nick Barker, a senior scientist in the Clevers lab, identified the Wnt target gene Lgr5 as a unique marker of adult stem cells in several epithelial organs, including the intestine, hair follicle, and stomach. In the intestine, the gene codes for a plasma membrane protein on crypt stem cells that enable the intestinal epithelium to self-renew, but can also give rise to adenomas of the gut. Upon making mice with adult stem cell populations tagged with a fluorescent Lgr5-binding marker, the lab helped to overturn assumptions that “stem cells are rare, impossible to find, quiescent, and divide asymmetrically.”

On to organoids. Once the lab could identify adult stem cells within the crypts of the gut, postdoc Toshiro Sato discovered that a single stem cell, in the presence of Matrigel and just three growth factors, could generate a miniature crypt structure—what is now called an organoid. “Toshi is very Japanese and doesn’t always talk much,” says Clevers. “One day I had asked him, while he was at the microscope, if the gut stem cells were growing, and he said, ‘Yes.’ Then I looked under the microscope and saw the beautiful structures and said, ‘Why didn’t you tell me?’ and he said, ‘You didn’t ask.’ For three months he had been growing them!” The lab has since also grown mini-pancreases, -livers, -stomachs, and many other mini-organs.

Tumor Organoids. Clevers showed that organoids can be grown from diseased patients’ samples, a technique that could be used in the future to screen drugs. The lab is also building biobanks of organoidsderived from tumor samples and adjacent normal tissue, which could be especially useful for monitoring responses to chemotherapies. “It’s a similar approach to getting a bacterium cultured to identify which antibiotic to take. The most basic goal is not to give a toxic chemotherapy to a patient who will not respond anyway,” says Clevers. “Tumor organoids grow slower than healthy organoids, which seems counterintuitive, but with cancer cells, often they try to divide and often things go wrong because they don’t have normal numbers of chromosomes and [have] lots of mutations. So, I am not yet convinced that this approach will work for every patient. Sometimes, the tumor organoids may just grow too slowly.”

Selective memory. “When I received the Breakthrough Prize in 2013, I invited everyone who has ever worked with me to Amsterdam, about 100 people, and the lab organized a symposium where many of the researchers gave an account of what they had done in the lab,” says Clevers. “In my experience, my lab has been a straight line from cloning TCF-1 to where we are now. But when you hear them talk it was ‘Hans told me to try this and stop this’ and ‘Half of our knockout mice were never published,’ and I realized that the lab is an endless list of failures,” Clevers recalls. “The one thing we did well is that we would start something and, as soon as it didn’t look very good, we would stop it and try something else. And the few times when we seemed to hit gold, I would regroup my entire lab. We just tried a lot of things, and the 10 percent of what worked, those are the things I remember.”

Greatest Hits

  • Cloned the first T cell–specific transcription factor, TCF-1, and identified homologous genes in model organisms including the fruit fly, frog, and worm
  • Found that transcriptional activation by the abundant β-catenin/TCF-4 [TCF7L2] complex drives cancer initiation in colon cells missing the tumor suppressor protein APC
  • First to extend the role of Wnt signaling from developmental biology to adult stem cells by showing that the two Wnt pathway transcription factors, TCF-1 and TCF-4, are necessary for maintaining the stem cell compartments in the thymus and in the crypt structures of the small intestine, respectively
  • Identified Lgr5 as an adult stem cell marker of many epithelial stem cells including those of the colon, small intestine, hair follicle, and stomach, and found that Lgr5-expressing crypt cells in the small intestine divide constantly and symmetrically, disproving the common belief that stem cell division is asymmetrical and uncommon
  • Established a three-dimensional, stable model, the “organoid,” grown from adult stem cells, to study diseased patients’ tissues from the gut, stomach, liver, and prostate
 Regenerative Medicine Comes of Age   
“Anti-Aging Medicine” Sounds Vaguely Disreputable, So Serious Scientists Prefer to Speak of “Regenerative Medicine”
  • Induced pluripotent stem cells (iPSCs) and genome-editing techniques have facilitated manipulation of living organisms in innumerable ways at the cellular and genetic levels, respectively, and will underpin many aspects of regenerative medicine as it continues to evolve.

    An attitudinal change is also occurring. Experts in regenerative medicine have increasingly begun to embrace the view that comprehensively repairing the damage of aging is a practical and feasible goal.

    A notable proponent of this view is Aubrey de Grey, Ph.D., a biomedical gerontologist who has pioneered an regenerative medicine approach called Strategies for Engineered Negligible Senescence (SENS). He works to “develop, promote, and ensure widespread access to regenerative medicine solutions to the disabilities and diseases of aging” as CSO and co-founder of the SENS Research Foundation. He is also the editor-in-chief of Rejuvenation Research, published by Mary Ann Liebert.

    Dr. de Grey points out that stem cell treatments for age-related conditions such as Parkinson’s are already in clinical trials, and immune therapies to remove molecular waste products in the extracellular space, such as amyloid in Alzheimer’s, have succeeded in such trials. Recently, there has been progress in animal models in removing toxic cells that the body is failing to kill. The most encouraging work is in cancer immunotherapy, which is rapidly advancing after decades in the doldrums.

    Many damage-repair strategies are at an  early stage of research. Although these strategies look promising, they are handicapped by a lack of funding. If that does not change soon, the scientific community is at risk of failing to capitalize on the relevant technological advances.

    Regenerative medicine has moved beyond boutique applications. In degenerative disease, cells lose their function or suffer elimination because they harbor genetic defects. iPSC therapies have the potential to be curative, replacing the defective cells and eliminating symptoms in their entirety. One of the biggest hurdles to commercialization of iPSC therapies is manufacturing.

  • Building Stem Cell Factories

    Cellular Dynamics International (CDI) has been developing clinically compatible induced pluripotent stem cells (iPSCs) and iPSC-derived human retinal pigment epithelial (RPE) cells. CDI’s MyCell Retinal Pigment Epithelial Cells are part of a possible therapy for macular degeneration. They can be grown on bioengineered, nanofibrous scaffolds, and then the RPE cell–enriched scaffolds can be transplanted into patients’ eyes. In this pseudo-colored image, RPE cells are shown growing over the nanofibers. Each cell has thousands of “tongue” and “rod” protrusions that could naturally support rod and cone cells in the eye.

    “Now that an infrastructure is being developed to make unlimited cells for the tools business, new opportunities are being created. These cells can be employed in a therapeutic context, and they can be used to understand the efficacy and safety of drugs,” asserts Chris Parker, executive vice president and CBO, Cellular Dynamics International (CDI). “CDI has the capability to make a lot of cells from a single iPSC line that represents one person (a capability termed scale-up) as well as the capability to do it in parallel for multiple individuals (a capability termed scale-out).”

    Minimally manipulated adult stem cells have progressed relatively quickly to the clinic. In this scenario, cells are taken out of the body, expanded unchanged, then reintroduced. More preclinical rigor applies to potential iPSC therapy. In this case, hematopoietic blood cells are used to make stem cells, which are manufactured into the cell type of interest before reintroduction. Preclinical tests must demonstrate that iPSC-derived cells perform as intended, are safe, and possess little or no off-target activity.

    For example, CDI developed a Parkinsonian model in which iPSC-derived dopaminergic neurons were introduced to primates. The model showed engraftment and enervation, and it appeared to be free of proliferative stem cells.

    • “You will see iPSCs first used in clinical trials as a surrogate to understand efficacy and safety,” notes Mr. Parker. “In an ongoing drug-repurposing trial with GlaxoSmithKline and Harvard University, iPSC-derived motor neurons will be produced from patients with amyotrophic lateral sclerosis and tested in parallel with the drug.” CDI has three cell-therapy programs in their commercialization pipeline focusing on macular degeneration, Parkinson’s disease, and postmyocardial infarction.

    • Keeping an Eye on Aging Eyes

      The California Project to Cure Blindness is evaluating a stem cell–based treatment strategy for age-related macular degeneration. The strategy involves growing retinal pigment epithelium (RPE) cells on a biostable, synthetic scaffold, then implanting the RPE cell–enriched scaffold to replace RPE cells that are dying or dysfunctional. One of the project’s directors, Dennis Clegg, Ph.D., a researcher at the University of California, Santa Barbara, provided this image, which shows stem cell–derived RPE cells. Cell borders are green, and nuclei are red.

      The eye has multiple advantages over other organ systems for regenerative medicine. Advanced surgical methods can access the back of the eye, noninvasive imaging methods can follow the transplanted cells, good outcome parameters exist, and relatively few cells are needed.

      These advantages have attracted many groups to tackle ocular disease, in particular age-related macular degeneration, the leading cause of blindness in the elderly in the United States. Most cases of age-related macular degeneration are thought to be due to the death or dysfunction of cells in the retinal pigment epithelium (RPE). RPE cells are crucial support cells for the rods, cones, and photoreceptors. When RPE cells stop working or die, the photoreceptors die and a vision deficit results.

      A regenerated and restored RPE might prevent the irreversible loss of photoreceptors, possibly via the the transplantation of functionally polarized RPE monolayers derived from human embryonic stem cells. This approach is being explored by the California Project to Cure Blindness, a collaborative effort involving the University of Southern California (USC), the University of California, Santa Barbara (UCSB), the California Institute of Technology, City of Hope, and Regenerative Patch Technologies.

      The project, which is funded by the California Institute of Regenerative Medicine (CIRM), started in 2010, and an IND was filed early 2015. Clinical trial recruitment has begun.

      One of the project’s leaders is Dennis Clegg, Ph.D., Wilcox Family Chair in BioMedicine, UCSB. His laboratory developed the protocol to turn undifferentiated H9 embryonic stem cells into a homogenous population of RPE cells.

      “These are not easy experiments,” remarks Dr. Clegg. “Figuring out the biology and how to make the cell of interest is a challenge that everyone in regenerative medicine faces. About 100,000 RPE cells will be grown as a sheet on a 3 × 5 mm biostable, synthetic scaffold, and then implanted in the patients to replace the cells that are dying or dysfunctional. The idea is to preserve the photoreceptors and to halt disease progression.”

      Moving therapies such as this RPE treatment from concept to clinic is a huge team effort and requires various kinds of expertise. Besides benefitting from Dr. Clegg’s contribution, the RPE project incorporates the work of Mark Humayun, M.D., Ph.D., co-director of the USC Eye Institute and director of the USC Institute for Biomedical Therapeutics and recipient of the National Medal of Technology and Innovation, and David Hinton, Ph.D., a researcher at USC who has studied how actvated RPE cells can alter the local retinal microenvironment.

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Cellular switch molecule for sperm motility control: a novel target for male contraception and infertility treatments

Reporter and Curator: Sudipta Saha, Ph.D.


Researchers have discovered the cellular switch that boosts the activity of sperm cells so that they can travel to the egg.  The finding may lead to new options for male contraception as well as treatments for infertility resulting from problems with sperm mobility.

Inside the male reproductive tract, mature sperm are capable of limited movement. This limited movement, however, is not enough to propel them toward the egg when they enter the female reproductive tract. To begin their journey, they must first be activated by the hormone progesterone, which is released by the egg.

The researchers reported that the molecule to which progesterone must bind is the enzyme alpha/beta hydrolase domain containing protein 2 (ABHD2), found in the sperm cell’s outer membrane. Similarly, strategies to bypass or enhance the enzyme might provide therapies for treating infertility resulting from sperm that lack movement capability.

Before a sperm can transition to the hyper-active phase, calcium must pass through the cell’s outer membrane and enter the flagella, the tail-like appendage the cell uses to propel itself. The sperm protein known as CatSper joins with similar proteins in the flagella to allow the entry of calcium.

When the researchers undertook the current study, it was not known whether progesterone interacted directly with CatSper to trigger the calcium influx, or acted on some other molecule (which, in turn, acted on CatSper). Before treating sperm with progesterone, the researchers exposed them to a chemical that inhibits a particular class of enzymes that they believed could include the candidate molecule that acted on CatSper. The hunch proved correct: the treated cells remained inactive after progesterone exposure, indicating that CatSper was not directly involved.

Working with modified progesterone, the researchers eventually isolated ABHD2 from the sperm tails. When the researchers inactivated ABHD2, exposure to progesterone failed to activate the sperm cells, confirming that ABHD2 is the molecular target for progesterone.

All of the technical terminology aside, this means that the researchers have pinned down the cellular switch that boosts the sperm along to the egg, so by blocking the ABHD2 activity, new male birth control methods could be on the way. Conversely, enhancing the enzyme could lead to new treatments for male infertility.

It will be interesting to see how this discovery impacts future research concerning male birth control and infertility treatments. Perhaps it’s the missing piece of information that will quickly yield an effective new male contraception option.








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