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AMPK Is a Negative Regulator of the Warburg Effect and Suppresses Tumor Growth In Vivo
Reporter-Curator: Stephen J. Williams, Ph.D.
Word Cloud by Daniel Menzin
There has been a causal link between alterations in cellular metabolism and the cancer phenotype. Reorganization of cellular metabolism, marked by a shift from oxidative phosphorylation to aerobic glycolysis for cellular energy requirements (Warburg effect), is considered a hallmark of the transformed cell. In addition, if tumors are to survive and grow, cancer cells need to adapt to environments high in metabolic stress and to avoid programmed cell death (apoptosis). Recently, a link between cancer growth and metabolism has been supported by the discovery that the LKB1/AMPK signaling pathway as a tumor suppressor axis[1].
LKB1/AMPK/mTOR Signaling Pathway
The Liver Kinase B1 (LKB1)/AMPK AMP-activated protein kinase/mammalian Target of Rapamycin Complex 1 (mTORC1) signaling pathway links cellular metabolism and energy status to pathways involved in cell growth, proliferation, adaption to energy stress, and autophagy. LKB1 is a master control for 14 other kinases including AMPK, a serine-threonine kinase which senses cellular AMP/ATP ratios. In response to cellular starvation, AMPK is allosterically activated by AMP, leading to activation of ATP-generating pathways like fatty acid oxidation and blocking anabolic pathways, like lipid and cholesterol synthesis (which consume ATP). In addition, AMPK regulates cell growth, proliferation, and autophagy by regulating the mTOR pathway. AMPK activates the tuberous sclerosis complex 1/2, which ultimately inhibits mTORC1 activity and inhibits protein translation. This mTOR activity is dis-regulated in many cancers.
LKB1/AMPK in Cancer
Somatic mutations of the STK11 gene encoding LKB1 are detected in lung and cervical cancers
Therefore LKB1 may be a strong tumor suppressor
Pharmacologic activation of LKB1/AMPK with metformin can suppress cancer cell growth
In a recent Cell Metabolism paper[2], Brandon Faubert and colleagues describe how AMPK activity reduces aerobic glycolysis and tumor proliferation while loss of AMPK activity promotes tumor proliferation by shifting cells to aerobic glycolysis and increasing anabolic pathways in a HIF1-dependent manner.
The paper’s major findings were as follows:
Loss of AMPKα1 cooperates with the Myc oncogene to accelerate lymphomagenesis
Inhibiting HIF-1α reverses the metabolic effects of AMPKα loss
HIF-1α mediates the growth advantage of tumors with reduced AMPK signaling
Summary
AMPK is a metabolic sensor that helps maintain cellular energy homeostasis. Despite evidence linking AMPK with tumor suppressor functions, the role of AMPK in tumorigenesis and tumor metabolism is unknown. Here we show that AMPK negatively regulates aerobic glycolysis (the Warburg effect) in cancer cells and suppresses tumor growth in vivo. Genetic ablation of the α1 catalytic subunit of AMPK accelerates Myc-induced lymphomagenesis. Inactivation of AMPKα in both transformed and nontransformed cells promotes a metabolic shift to aerobic glycolysis, increased allocation of glucose carbon into lipids, and biomass accumulation. These metabolic effects require normoxic stabilization of the hypoxia-inducible factor-1α (HIF-1α), as silencing HIF-1α reverses the shift to aerobic glycolysis and the biosynthetic and proliferative advantages conferred by reduced AMPKα signaling. Together our findings suggest that AMPK activity opposes tumor development and that its loss fosters tumor progression in part by regulating cellular metabolic pathways that support cell growth and proliferation.
Below is the graphical abstract of this paper.
(Photo credit reference(2; Faubert et. al) permission from Elsevier)
However, this regulation of tumor promotion by AMPK may be more complicated and dependent on the cellular environment.
Nissam Hay from the University of Illinois College of Medicine, Chicago, Illinois, USA and his co-workers Sang-Min Jeon and Navdeep Chandel were investigating the mechanism through which LKB1/AMPK regulate the balance between cancer cell growth and apoptosis under energy stress[3]. In their system, the loss of function of either of these proteins makes cells more sensitive to apoptosis in low glucose environments, and cells deficient in either AMPK or LKB1 were shown to be resistant to oncogenic transformation. Whereas previous studies showed (as above) AMPK opposes tumor proliferation in a HIF1-dependent manner, their results showed AMPK could promote tumor cell survival during periods of low glucose or altered redox status.
The researchers incubated LKB1-deficient cancer cells in the presence of either glucose or one of the non-metabolizable glucose analogues 2-deoxyglucose (2DG) and 5-thioglucose (5TG), and found that 2DG, but not 5TG, induced the activation of AMPK and protected the cells from apoptosis, even in cells that were deficient in LKB1.
The authors demonstrated that glucose deprivation depleted NADPH levels, increased H2O2 levels and increased cell death, and that this was accelerated in cells deficient in the enzyme glucose-6-phosphate dehydrogenase. Anti-oxidants were also found to inhibit cell death in cells deficient in either AMPK or LKB1.
Knockdown or knockout of either LKB1 or AMPK in cancer cells significantly increased levels of H2O2 but not of peroxide (O2–) during glucose depletion. The glucose analogue 2DG was able to activate AMPK and maintain high levels of NADPH and low levels of H2O2 in these cells.
The nucleotide coenzyme NADPH is generated in the pentose phosphate pathway and mitochondrial metabolism, and consumed in H2O2 elimination and fatty acid synthesis. If glucose is limited mitochondrial metabolism becomes the major source of NADPH, supported by fatty acid oxidation. AMPK is known to be a regulator of fatty acid metabolism through inhibition of two acetyl-CoA carboxylases, ACC1 and ACC2.
Short interfering RNAs (siRNAs) to knock down levels of both ACC1 and ACC2 in A549 cancer cells and found that only ACC2 knockdown significantly increased peroxide accumulation and apoptosis, while over-expression of mutant ACC1 and ACC2 in LKB1-proficient cells increased H2O2 and apoptosis.
Therefore, it was concluded AMPK acts to promote early tumor growth and prevent apoptosis in conditions of energy stress through inhibiting acetyl-CoA carboxylase activity, thus maintaining NADPH levels and preventing the build-up of peroxide in glucose-deficient conditions.
This may appear to be conflicting with the previous report in this post however, it is possible that these reports reflect differences in the way cells respond to various cellular stresses, be it hypoxia, glucose deprivation, or changes in redox status. Therefore a complex situation may arise:
AMPK promotes tumor progression under glucose starvation
AMPK can oppose tumor proliferation under a normoxic, HIF1-dependent manner
Could AMPK regulation be different in cancer stem cells vs. non-stem cell?
References:
1. Green AS, Chapuis N, Lacombe C, Mayeux P, Bouscary D, Tamburini J: LKB1/AMPK/mTOR signaling pathway in hematological malignancies: from metabolism to cancer cell biology. Cell Cycle 2011, 10(13):2115-2120.
2. Faubert B, Boily G, Izreig S, Griss T, Samborska B, Dong Z, Dupuy F, Chambers C, Fuerth BJ, Viollet B et al: AMPK is a negative regulator of the Warburg effect and suppresses tumor growth in vivo. Cell metabolism 2013, 17(1):113-124.
3. Jeon SM, Chandel NS, Hay N: AMPK regulates NADPH homeostasis to promote tumour cell survival during energy stress. Nature 2012, 485(7400):661-665.
Other posts on this site related to Warburg Effect and Cancer include:
This discussion will identify the huge expansion of genomic technology in the search for biopharmacotherapeutic targets that continue to be explored involving different levels and interacting signaling pathways. There are several methods of analyzing gene expression that will be discussed. Great primary emphasis required investigation of combinations of mutations expressed in different cancer types. James Watson has proposed a major hypothesis that expresses the need to focus on “central” “driver mutations” that correspond with the regulation of gene expression, cell proliferation, and cell metabolism eith a critical rejection of antioxiant benefits. What hasn’t been know is why drug resistance develops and whether the cellular migration and aerobic glycolysis can be redirected after cell metastasis occurs. I attempt to bring out the complexities of current efforts.
.Introduction
This discussion is a continuation of a previous discussion on the role of genomics if discovery of therapeutic targets for cancer, each somewhat different, but all related to:
The reversal of carcinoma by targeting a key driver of multiple signaling pathways that activate cell proliferation
Pinpointing a stage in a multistage process at which tumor progression links to changes in morphology from basal cells to invasive carcinoma with changes in polarity and loss of glandular architecture
Reversal of the carcinoma through using a small molecule that either is covalently bound to a nanoparticle delivery system that blocks or reverses tumor development
Synthesis of a small molecule that interacts with the translation of the genome either by substitution of a key driver molecule or by blocking at the mRNAstage of translation
Blocking more than one signaling pathway that are links to carcinogenesis and cellular proliferation and invasion
Difficulty of the problem
A problem expressed by James Watson is that the investigations that are ongoing
are following a pathway that is not driven by attacking the “primary” driver of carcinogenesis.
He uses the Myc gene as an example, as noted in the previous discussion. The problem may be more complicated than he envisions.
The most consistent problem in chemotherapy, irrespective of the design and the target has been cancer remission for a short time followed by recurrence, and then
switching to another drug, or combination chemotherapy.
It is common to “clean” the field at the time of resection using radiotherapy before chemotherapy.
But the goal is understood to be “palliation”, not cure.
This raises a serious issue in the hypothesis posed by Watson. The issue is
whether there is a core locus of genetic regulation that is common to carcinogenesis irrespective of tissue metabolic expression.
This is supported by the observation that tissue specific express is lost in cancer cells by de-differentiation.
In 1967Otto Warburgpublished his view in a paper “The prime cause and prevention of cancer”.
There are primary and secondary causes of all diseases
plague – primary: plague bacillus
plague – secondary: filth, rats, and fleas
cancer, above all diseases,
has countless seconday causes
primary – replacement of respiration of oxygen in normal body tissue by fermentation of glucose with conversion from obligate aerobic to anaerobic, as in bacterial cells
The cornerstone to understanding cancer is in study of the energetics of life
This thinking came out of decades of work in the Dahlem Institute Kaiser Wilhelm pre WWII and Max Planck Institute after WWII, supported by the Rockefeller Foundation.
The oxygen- and hydrogen-transferring enzymes were discovered and isolated.
The methods were elegant for that time, using a manometer that improved on the method used by Haldane, that did not allow the leakage of O2 or CO2.
The interest was initiated by the increased growth of Sea Urchin eggs after fertization, which turned out to be not comparable to the rapid growth of cancer cells.
Warburg used both normal and cancer tissue and measured the utilization of O2. He found
that the normal tissue did not accumulate lactic acid.
Cancer tissue generated lactic acid
the rate of O2 consumption the same as normal tissue, but
the rate of lactate formation far exceeded any tissue, except the retina.
Hematopoietic cells of bone marrow develop aerobic glycolysis when exposed to a low oxygen condition.
He then followed on an observation by Otto Meyerhoff (Embden-Myerhoff cycle) that in muscle
the consumption of one molecule of oxygen generates two molecules of lactate, but in aerobic glycolysis, the relationship disappears.
He expressed the effectiveness of respiration by the ‘Meyerhoff quotient’.
He found that cancer cells didn’t have a quotient of ‘2’
The role of the allosteric enzyme phosphofructokinase (PFK) not then known, would tie together the glycolytic and gluconeogenic pathways.
He used a heavy metal ion chelator ethylcarbylamine to
sever the link and turn on aerobic glycolysis.
The explanation for this was provided years later by the work fleshed out by Lynen, Bucher, Lowry, Racker, and Sols.
The rate-limiting enzyme, PFK is regulated by the concentrations of ATP, ADP, and inorganic phosphate. The ethylcarbylamide was an ‘uncoupler’ of oxidative phosphorylation.
Warburg understood that when normal cells switched to aerobic glycolysis
it is a re-orientation of normal cell expression.
this provides the basis for the inference that neoplastic cells become more like each other than their cell of origin.
embryonic cells can be transformed into cancer cells under hypoxic conditions
re-exposure to higher oxygen did not cause reversion back to normal cells.
Warburg publically expressed the rejected view in 1954 (at age 83) that restriction of chemical wastes, food additives, and air pollution would substantially reduce cancer rates.
His emphasis on the impairment of respiration was inadequate.
the prevailing view today is loss of controlled growth of normal cells in cancer cells.
The Human Genome Project, driven by Francis Collins at NIH, and by Craig Venter at the Institute for Genome Research (TIGR) had parallel projects to map the human chromosome, completed in 2003. It originally aimed to map the nucleotides contained in a human haploid reference genome (more than three billion). TIGR was the first complete genomic sequencing of a free living organism, Haemophilus influenzae, in 1995. This used a shotgun sequencing technique pioneered earlier, but which had never been used for a whole bacterium.
Venter broke away from the HGP and started Celera in 1998 because of resistance to the shotgun sequency method, and his team completed the genome sequence in three years – seven years’ less time than the HGP timetable (using the gene of Dr. Venter). TIGR eventually sequenced and analyzed more than 50 microbial genomes. Its bioinformatics group developed
pioneering software algorithms that were used to analyze these genomes,
including the automatic gene finder GLIMMER and
the sequence alignment program MUMmer.
In 2002, Venter created and personally funded theJ. Craig Venter Institute (JCVI) Joint Technology Center (JTC), which specialized in high throughput sequencing. The JTC, in the top ranks of scientific institutions worldwide, sequenced nearly 100 million base pairs of DNA per day for its affiliated institutions (JCVI) .
He received his his Ph.D. degree in physiology and pharmacology from the University of California, San Diego in 1975 under biochemist Nathan O. Kaplan. A full professor at the State University of New York at Buffalo, he joined the National Institutes of Health in 1984. There he learned of a technique for rapidly identifying all of the mRNAs present in a cell and began to use it to identify human brain genes. The short cDNA sequence fragments discovered by this method are called expressed sequence tags (ESTs), a name coined by Anthony Kerlavage at TIGR.
Venter believed that shotgun sequencing was the fastest and most effective way to get useful human genome data. There was a belief that shotgun sequencing was less accurate than the clone-by-clone method chosen by the HGP, but the technique became widely accepted by the scientific community and is still the de facto standard used today.
An article has been discussed by Dr. Tilda Barilya on use of a sensitive fluorescent probe in the near IR spectrum at > 700 nm to identify malignant ovarian cells in-vivo in abdominal exploration by tagging an overexpressed FR-α (folate-FITA)
The author makes the point that:
In ovarian cancer, the FR-α appears to constitute a good target because it is overexpressed in 90–95% of malignant tumors, especially serous carcinomas.
Targeting ligand, folate, is attractive as it is nontoxic, inexpensive and relatively easily conjugated to a fluorescent dye to create a tumor-specific fluorescent contrast agent.
The report is identified as “ the first in-human proof-of-principle of the use of intraoperative tumor-specific fluorescence imaging in staging and debulking surgery for ovarian cancer using the systemically administered targeted fluorescent agent folate-FITC.”
While this does invoke possibilities for prognosis, the decision to perform the surgery, whether laparoscopic or open, is late in the discovery process. However, it does suggest the possibility that the discovery and the treatment might be combined if the biomarker itself had the fluorescence to identify the overexpression, but it also is combined with a tag to block the overexpession. This hypothetical possibility is now expressed below. http://pharmaceuticalintelligence.com/2013/01/19/ovarian-cancer-and-fluorescence-guided-surgery-a-report/
can achieve much greater control over where new genes are inserted
According to Feng Zhang, this is an improvement beyond splicing the gene in specific locations and insertion of complexes difficult to assemble known as transcription activator-like effector nucleases (TALENs).
The researchers create DNA-editing complexes
using naturally occurring bacterial protein-RNA systems
that recognize and snip viral DNA, including
a nuclease called Cas9 bound to short RNA sequences.
they target specific locations in the genome, and
when they encounter a match, Cas9 cuts the DNA.
This approach can be used either to
disrupt the function of a gene or
to replace it with a new one.
To replace the gene, a DNA template for the new gene has to be copied into the genome after the DNA is cut. The method is also very precise —
if there is a single base-pair difference between the RNA targeting sequence and the genome sequence, Cas9 is not activated.
In its first iteration, it appears comparable in efficiency to what zinc finger nucleases and TALENs have to offer.
The research team has deposited the necessary genetic components with a nonprofit called Addgene, and they have also created a website with tips and tools for using this new technique.
The above story is reprinted from materials provided by Massachusetts Institute of Technology. The original article was written by Anne Trafton.
Le Cong, F. Ann Ran, David Cox, Shuailiang Lin, Robert Barretto, Naomi Habib, Patrick D. Hsu, Xuebing Wu, Wenyan Jiang, Luciano Marraffini, and Feng Zhang. Multiplex Genome Engineering Using CRISPR/Cas Systems. Science, 3 January 2013 DOI: 10.1126/science.1231143. http://Science.com. Editing genome with high precision: New method to insert multiple genes in specific locations, delete defective genes. ScienceDaily. Retrieved January 20, 2013, from http://www.sciencedaily.com /releases/2013/01/130103143205.htm?goback=%2Egde_4346921_member_205356312.
The information needed for the production of a mature protein is encoded in segments called exons .
In the splicing process, the non-coding segments of the RNA (introns) are spliced from the pre-mRNA and
the exons are joined together.
Alternative splicing is when a specific ”scene” (or exon) is either inserted or deleted from the movie (mRNA), thus changing its meaning.
Over 90 percent of the genes in our genome undergo alternative splicing of one or more of their exons, and
the resulting changes in the proteins encoded by these different mRNAs are required for normal function.
the normal process of alternative splicing is altered in cancer, and
”bad” protein forms are generated that aid cancer cell proliferation and survival.
The researchers reported in online Cell Reports that breast cancer cells
change the alternative splicing of an important enzyme, calledS6K1, which is
a protein involved in the transmission of information into the cell.
when this happens, breast cancer cells start to produce shorter versions of this enzyme and
these shorter versions transmit signals ordering the cells to grow, proliferate, survive and invade other tissues (otherwise proliferation is suppressed)
The application to biotherapeutics would be to ”reverse” the alternative splicing of S6K1 in cancer cells back to the normal situation as a novel anti-cancer therapy.
With a new approach, researchers may rapidly distinguish the range of
genetic changes that are causally linked to cancer (i.e. “driver” mutations)
versus those with limited impact on cancer progression.
This study published in the prestigious journal Genes & Development could pave the way to design more targeted treatment against different cancer types, based on the specific cancer-linked mutations present in the patient, an advance in the development of personalized medicine.
Signaling pathways involved in tumour formation are conserved from fruit flies to humans. In fact, about 75 percent of known human disease genes have a recognizable match in the genome of fruit flies.
Leveraging on their genetic similarities, Dr Hector Herranz, a post-doctorate from the Dr. Stephen Cohen’s team developed an innovative strategy to genetically screen the whole fly genome for “cooperating” cancer genes.
These genes appear to have little or no impact on cancer.
However, they cooperate with other cancer genes, so that
the combination causes aggressive cancer, which
neither would cause alone.
In this study, the team was specifically looking for genes that
could cooperate with EGFR “driver” mutation,
a genetic change commonly associated with breast and lung cancers in humans.
SOCS5 (reported in this paper) is one of the several new “cooperating” cancer genes to be identified.
Already, there are indications that levels of SOCS5 expression are
reduced in breast cancer, and
patients with low levels of SOCS5 have poor prognosis.”
The IMCB team is preparing to explore the use of SOCS5 as a biomarker in diagnosis for cancer. http://genes&development.com
‘Altered cellular metabolism is a hallmark of cancer,’ says Dr Patrick Pollard, in the Nuffield Department of Clinical Medicine at Oxford. Most cancer cells get the energy they need predominantly through a high rate of glycolysis, allowing cancer cells deal with the low oxygen levels that tend to be present in a tumour.
But whether dysfunctional metabolism causes cancer, as Warburg believed, or is something that happens afterwards is a different question. In the meantime, gene studies rapidly progressed and indicated that genetic changes occur in cancer.
DNA mutations spring up all the time in the body’s cells, but
most are quickly repaired.
Alternatively the cell might shut down or be killed off (apoptosis) before any damage is caused. However, the repair machinery is not perfect.
If changes occur that bypass parts of the repair machinery or sabotage it,
the cell can escape the body’s normal controls on growth and
DNA changes can begin to accumulate as the cell becomes cancerous.
Patrick believes certain changes in cells can’t always be accounted for by ‘genetics.’
He is now collaborating with Professor Tomoyoshi Soga’s large lab at Keio University in Japan, which has been at the forefront of developing the technology for metabolomics research over the past couple of decades.
The Japanese lab’s ability to
screen samples for thousands of compounds and metabolites at once, and
the access to tumour material and cell and animal models of disease
enables them to probe the metabolic changes that occur in cancer.
There is reason to believe that
dysfunctional cell metabolism is important in cancer.
genes with metabolic functions are associated with some cancers
changes in the function of a metabolic enzyme have been implicated in the development of gliomas.
These results have led to the idea that some metabolic compounds, or metabolites, when they accumulate in cells, can cause changes to metabolic processes and set cells off on a path towards cancer.
Patrick Pollard and colleagues have now published a perspective article in the journal Frontiers in Molecular and Cellular Oncology that proposes fumarate as such an ‘oncometabolite’. Fumarate is a standard compound involved in cellular metabolism.
The researchers summarize evidence that shows how
accumulation of fumarate when an enzyme goes wrong affects various biological pathways in the cell.
It shifts the balance of metabolic processes and disrupts the cell in ways that could favour development of cancer.
Patrick and colleagues write in their latest article that the shift in focus of cancer research to include cancer cell metabolism ‘has highlighted how woefully ignorant we are about the complexities and interrelationships of cellular metabolic pathways’.
Using genome-wide Chromatin Interaction Analysis with Paired-End-Tag sequencing (ChIA-PET),
mapped long-range chromatin interactions associated with RNA polymerase II in human cells
uncovered widespread promoter-centered intragenic, extragenic, and intergenic interactions.
These interactions further aggregated into higher-order clusters
proximal and distal genes were engaged through promoter-promoter interactions.
most genes with promoter-promoter interactions were active and transcribed cooperatively
some interacting promoters could influence each other implying combinatorial complexity of transcriptional controls.
Comparative analyses of different cell lines showed that
cell-specific chromatin interactions could provide structural frameworks for cell-specific transcription,
and suggested significant enrichment of enhancer-promoter interactions for cell-specific functions.
genetically-identified disease-associated noncoding elements were spatially engaged with corresponding genes through long-range interactions.
Overall, our study provides insights into transcription regulation by
three-dimensional chromatin interactions for both housekeeping and
Transcriptional regulation is a complex process that requires the integrated action of many multi-protein complexes.
The way in which a living cell coordinates the action of these complexes in time and space is still poorly understood.
nuclear pores, well known for their role in 3′ processing and export of transcripts, also participate in the control of transcriptional initiation.
nuclear pores interface with the well-described machinery that regulates initiation.
This work led to the discovery that
specific nucleoporins are required for binding of the repressor protein Mig1 to its site in target promoters.
Nuclear pores are involved in repressing, as well as activating, transcription.
Here we discuss in detail the main models explaining our result and consider what each implies about the roles that nuclear pores play in the regulation of gene expression.
(M Burton, M Thomassen, Q Tan, and TA Kruse.) Cancer Informatics 2012:11 193–217 doi: 10.4137/CIN.S10375
The popularity of a large number of microarray applications has in cancer research led to the development of predictive or prognostic gene expression profiles. However, the diversity of microarray platforms has made the full validation of such profiles and their related gene lists across studies difficult and, at the level of classification accuracies, rarely validated in multiple independent datasets. Frequently, while the individual genes between such lists may not match, genes with same function are included across such gene lists. Development of such lists does not take into account the fact that
genes can be grouped together as metagenes (MGs) based on common characteristics such as pathways, regulation, or genomic location.
In this study we compared the performance of either metagene- or single gene-based feature sets and classifiers using random forest and two support vector machines for classifier building. The performance
within the same dataset,
feature set validation performance, and
validation performance of entire classifiers in strictly independent datasets
were assessed by
10 times repeated 10-fold cross validation,
leave-one-out cross validation, and
one-fold validation, respectively.
To test the significance of the performance difference between MG- and SG-features/classifiers, we used a repeated down-sampled binomial test approach.
MG- and SG-feature sets are transferable and perform well for training and testing prediction of metastasis outcome
in strictly independent data sets, both
between different and
within similar microarray platforms, while
classifiers had a poorer performance when validated in strictly independent datasets.
The study showed that MG- and SG-feature sets perform equally well in classifying independent data. Furthermore, SG-classifiers significantly outperformed MG-classifier
when validation is conducted between datasets using similar platforms, while
no significant performance difference was found when validation was performed between different platforms.
Prediction of metastasis outcome in lymph node–negative patients by MG- and SG-classifiers showed that SG-classifiers performed significantly better than MG-classifiers when validated in independent data based on the same microarray platform as used for developing the classifier. However, the MG- and SG-classifiers had similar performance when conducting classifier validation in independent data based on a different microarray platform. The latter was also true when only validating sets of MG- and SG-features in independent datasets, both between and within similar and different platforms.
to identify the differentially expressed miRNAs in the serum of children with RB in comparison with the normal age matched serum,
to analyze its concurrence with the existing RB tumor miRNA profile,
to identify its novel gene targets specific to RB, and
to study the expression of a few of the identified oncogenic miRNAs in the advanced stage primary RB patient’s serum sample.
MiRNA profiling performed on 14 pooled serum from children with advanced RB and 14 normal age matched serum samples
21 miRNAs found to be upregulated (fold change > 2.0, P < 0.05) and
24 downregulated (fold change > 2.0, P < 0.05).
Intersection of 59 significantly deregulated miRNAs identified from RB tumor profiles with that of miRNAs detected in serum profile revealed that
33 miRNAs had followed a similar deregulation pattern in RB serum.
Later we validated a few of the miRNAs (miRNA 17-92) identified by microarray in the RB patient serum samples (n = 20) by using qRT-PCR.
Expression of the oncogenic miRNAs, miR-17, miR-18a, and miR-20a by qRT-PCR was significant in the serum samples
exploring the potential of serum miRNAs identification as noninvasive diagnosis.
Moreover, from miRNA gene target prediction, key regulatory genes of
cell proliferation,
apoptosis, and
positive and negative regulatory networks
involved in RB progression were identified in the gene expression profile of RB tumors.
Therefore, these identified miRNAs and their corresponding target genes could give insights on
potential biomarkers and key events involved in the RB pathway.
Computational Design of Targeted Inhibitors of Polo-Like Kinase 1 ( lk1).
(KS Jani and DS Dalafave) Bioinformatics and Biology Insights 2012:6 23–31.doi: 10.4137/BBI.S8971.
Down regulation of Plk1 has been shown to inhibit tumor progression.
Most kinase inhibitors interact with the ATP binding site on Plk1, which is highly conserved.
This makes the development of Plk1-specific inhibitors challenging, since different kinases have similar ATP sites.
However, Plk1 also contains a unique region called the polo-box domain (PBD), which is absent from other kinases.
the PBD site was used as a target for designed Plk1 putative inhibitors.
Common structural features of several experimentally known Plk1 ligands were first identified.
The findings were used to design small molecules that specifically bonded Plk1.
Drug likeness and possible toxicities of the molecules were investigated.
Molecules with no implied toxicities and optimal drug likeness values were used for docking studies.
Several molecules were identified that made stable complexes only with Plk1 and LYN kinases, but not with other kinases.
One molecule was found to bind exclusively the PBD site of Plk1.
Possible utilization of the designed molecules in drugs against cancers with over expressed Plk1 is discussed.
Conclusions
The previous discussions reviewed the status of an evolving personalized medicine multicentered and worldwide enterprise. It is also clear from these reports that the search for targeted drugs matched to a cancer profile or signature has identified several approaches that show great promise.
We know considerably more about metabolic pathways and linked changes in transcription that occur in neoplastic development.
There are several methods used to do highly accurate insertions in gene sequences that are linked to specific metabolic changes, and
some may have significant implications for therapeutics, if
the link is a change that is associated with a driver mutation
the link can be identified by a fluorescent or other probe
the link is tied to a mRNA or peptide product that is a biomarker measured in the circulation
We have probes to genetic links to the control of many and interacting signaling pathways.
We know more about transcription through mRNA.
We are closer to the possibility that metabolic substrates, like ‘fumarate’ (a key intermediate in the TCA cycle), may provide a means to reverse regulate the neoplastic cells.
We may also find metabolic channels that drive the cells from proliferation to apoptosis or normal activity.
Summary
This discussion identified the huge expansion of genomic technology in the investigation of biopharmacotherapeutic targets that have been identified involving different levels and interacting signaling pathways. There are several methods of analyzing gene expression, and a primary emphasis is given to combinations of mutations expressed in different cancer types. There is a major hypothesis that expresses the need to focus on “central” “driver mutations” that correspond with the regulation of gene expression, cell proliferation, and cell metabolism. What hasn’t been know is why drug resistance develops and whether the cellular migration and aerobic glycolysis can be redirected after cell metastasis occurs.
.
A slight mutation in the matched nucleotides can lead to chromosomal aberrations and unintentional genetic rearrangement. (Photo credit: Wikipedia)
Deutsch: Regulation der Phosphofructokinase (Photo credit: Wikipedia)
Other posts related to this discussion were published on this Open Source Online Scientific Journal from Leaders in Pharmaceutical Business Intelligence:
Otto Heinrich Warburg (October 8, 1883 – August 1, 1970), son of physicist Emil Warburg, was a German physiologist, medical doctor and Nobel laureate.
Otto Heinrich Warburg was born on October 8, 1883, in Freiburg, Baden. His father, the physicist Emil Warburg, was President of the Physikalische Reichsanstalt, Wirklicher Geheimer Oberregierungsrat. He was a member of the Warburg family, a prominent family and financial dynasty of German Jewish descent, noted for their varied accomplishments in physics, classical music, art history, pharmacology, physiology, finance, private equity and philanthropy. They are believed to be descended from the Venetian Jewish del Banco family, in the early 1500s one of the wealthiest Venetian families. The Warburgs fled from Italy to Warburg in Germany in the 16th century before moving to Altona, near Hamburg in the 17th century taking their surname from the city of Warburg. The brothers Moses Marcus Warburg(1763 – 1830) and Gerson Warburg (1765 – 1826) founded the M. M. Warburg & Co. banking company in 1798 that is still in existence.
Otto studied chemistry under the great Emil Fischer, and gained the degree, Doctor of Chemistry (Berlin), in 1906. He then studied under von Krehl and obtained the degree, Doctor of Medicine (Heidelberg), in 1911.
He served as an officer in the elite Uhlan (cavalry regiment) during the First World War, and won the Iron Cross (1st Class) for bravery. Warburg was one of the 20th century’s leading biochemists. [1] He won the Nobel Prize of 1931. In total, he was nominated an unprecedented three times for the Nobel prize for three separate achievements.
While working at the Marine Biological Station, Warburg performed research on oxygen consumption in sea urchin eggs after fertilization, and proved that upon fertilization, the rate of respiration increases by as much as sixfold. His experiments also proved iron is essential for the development of the larval stage.
In 1918, Warburg was appointed professor at the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem (part of the Kaiser-Wilhelm-Gesellschaft). By 1931 he was named director of the Kaiser Wilhelm Institute for Cell Physiology, which was founded the previous year by a donation of the Rockefeller Foundation to the Kaiser Wilhelm Gesellschaft (since renamed the Max Planck Society).
Warburg’s early researches with Fischer were in the polypeptide field.
At Heidelberg he worked on the process of oxidation. His special interest in the investigation of vital processes by physical and chemical methods led to attempts to relate these processes to phenomena of the inorganic world. His methods involved detailed studies on the assimilation of carbon dioxide in plants, the metabolism of tumors, and the chemical constituent of the oxygen transferring respiratory ferment. Warburg was never a teacher, and he has always been grateful for his opportunities to devote his whole time to scientific research. His later researches at the Kaiser Wilhelm Institute have led to the discovery that the flavins and the nicotinamide were the active groups of the hydrogen-transferring enzymes.
This, together with the iron-oxygenase discovered earlier, gives a complete account of the oxidations and reductions in the living world. Warburg investigated the metabolism of tumors and the respiration of cells, particularly cancer cells, and in 1931 was awarded the Nobel Prize in Physiology for his “discovery of the nature and mode of action of the respiratory enzyme.”[2]
The award came after receiving 46 nominations over a period of nine years beginning in 1923, 13 of which were submitted in 1931, the year he won the prize. This discovery opened up new ways in the fields of cellular metabolism and cellular respiration. He hypothesized, among other things, that cancerous cells can live and develop, even in the absence of oxygen. Warburg also wrote about oxygen’s relationship to the pH of cancer cells’ internal environments, since fermentation was a major metabolic pathway of cancer cells.
Three scientists who worked in Warburg’s lab, including Sir Hans Adolf Krebs, went on to win the Nobel Prize. Among other discoveries, Krebs is credited with the identification of the citric acid cycle (or Szent györgyi-Krebs cycle).
In 1944, Warburg was nominated for a second Nobel Prize in Physiology by Albert Szent-Györgyi, for his work on nicotinamide, the mechanism and enzymes involved in fermentation, and the discovery of flavine (in yellow enzymes). Although he was considered a worthwhile candidate, he was not selected for the prize.
References
Krebs, HA (1972), “Warburg Heinrich Warburg. 1883-1970”, Biographical Memoirs of Fellows of the Royal Society (The Royal Society) 18: 628–699,doi:10.1098/rsbm.1972.0023
Som P; Atkins HL; Bandoypadhyay D et al. (1 July 1980), “A fluorinated glucose analog, 2-fluoro-2-deoxy-D-glucose (F-18): nontoxic tracer for rapid tumor detection”, J. Nucl. Med.21 (7): 670–5, PMID7391842
Chernow, Ron (1993), The Warburgs: The Twentieth-Century Odyssey of a Remarkable Jewish Family, New York, NY: Random House, ISBN0-679-41823-7
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