Healthcare analytics, AI solutions for biological big data, providing an AI platform for the biotech, life sciences, medical and pharmaceutical industries, as well as for related technological approaches, i.e., curation and text analysis with machine learning and other activities related to AI applications to these industries.
2.1.5.5 Promising research for a male birth control pill, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 2: CRISPR for Gene Editing and DNA Repair
Scientists think excessive population growth is a cause of scarcity and environmental degradation. A male pill could reduce the number of unintended pregnancies, which accounts for 40 percent of all pregnancies worldwide.
But, big drug companies long ago dropped out of the search for a male contraceptive pill which is able to chemically intercept millions of sperm before they reach a woman’s egg. Right now the chemical burden for contraception relies solely on the female. There’s not much activity in the male contraception field because an effective solution is available on the female side.
Presently, male contraception means a condom or a vasectomy. But researchers from Center for Drug Discovery at Baylor College of Medicine, USA are renewing the search for a better option—an easy-to-take pill that’s safe, fast-acting, and reversible.
The scientists began with lists of genes active in the testes for sperm production and motility and then created knockout mice that lack those genes. Using the gene-editing technology called CRISPR, in collaboration with Japanese scientists, they have so far made more than 75 of these “knockout” mice.
They allowed these mice to mate with normal (wild type) female mice, and if their female partners don’t get pregnant after three to six months, it means the gene might be a target for a contraceptive. Out of 2300 genes that are particularly active in the testes of mice, the researchers have identified 30 genes whose deletion makes the male infertile. Next the scientists are planning a novel screening approach to test whether any of about two billion chemicals can disable these genes in a test tube. Promising chemicals could then be fed to male mice to see if they cause infertility.
Female birth control pills use hormones to inhibit a woman’s ovaries from releasing eggs. But hormones have side effects like weight gain, mood changes, and headaches. A trial of one male contraceptive hormone was stopped early in 2011 after one participant committed suicide and others reported depression. Moreover, some drug candidates have made animals permanently sterile which is not the goal of the research. The challenge is to prevent sperm being made without permanently sterilizing the individual.
As a better way to test drugs, Scientists at University of Georgia, USA are investigating yet another high-tech approach. They are turning human skin cells into stem cells that look and act like the spermatogonial cells in the testes. Testing drugs on such cells might provide more accurate leads than tests on mice.
The male pill would also have to start working quickly, a lot sooner than the female pill, which takes about a week to function. Scientists from University of Dundee, U.K. admitted that there are lots of challenges. Because, a women’s ovary usually release one mature egg each month, while a man makes millions of sperm every day. So, the male pill has to be made 100 percent effective and act instantaneously.
Translation of whole human genome sequencing to clinical practice: The Joint Initiative for Metrology in Biology (JIMB) is a collaboration between the National Institute of Standards & Technology (NIST) and Stanford University, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 1: Next Generation Sequencing (NGS)
Translation of whole human genome sequencing to clinical practice: The Joint Initiative for Metrology in Biology (JIMB) is a collaboration between the National Institute of Standards & Technology (NIST) and Stanford University.
Reporter: Aviva Lev-Ari, PhD, RN
JIMB’s mission is to advance the science of measuring biology (biometrology). JIMB is pursuing fundamental research, standards development, and the translation of products that support confidence in biological measurements and reliable reuse of materials and results. JIMB is particularly focused on measurements and technologies that impact, are related to, or enabled by ongoing advances in and associated with the reading and writing of DNA.
Stanford innovators and industry entrepreneurs have joined forces with the measurement experts from NIST to create a new engine powering the bioeconomy. It’s called JIMB — “Jim Bee” — the Joint Initiative for Metrology in Biology. JIMB unites people, platforms, and projects to underpin standards-based research and innovation in biometrology.
Genome in a Bottle
Authoritative Characterization of
Benchmark Human Genomes
The Genome in a Bottle Consortium is a public-private-academic consortium hosted by NIST to develop the technical infrastructure (reference standards, reference methods, and reference data) to enable translation of whole human genome sequencing to clinical practice. The priority of GIAB is authoritative characterization of human genomes for use in analytical validation and technology development, optimization, and demonstration. In 2015, NIST released the pilot genome Reference Material 8398, which is genomic DNA (NA12878) derived from a large batch of the Coriell cell line GM12878, characterized for high-confidence SNPs, indel, and homozygous reference regions (Zook, et al., Nature Biotechnology 2014).
There are four new GIAB reference materials available. With the addition of these new reference materials (RMs) to a growing collection of “measuring sticks” for gene sequencing, we can now provide laboratories with even more capability to accurately “map” DNA for genetic testing, medical diagnoses and future customized drug therapies. The new tools feature sequenced genes from individuals in two genetically diverse groups, Asians and Ashkenazic Jews; a father-mother-child trio set from Ashkenazic Jews; and four microbes commonly used in research. For more informationclick here. To purchase them, visit:
Data and analyses are publicly available (GIAB GitHub). A description of data generated by GIAB is published here. To standardize best practices for using GIAB genomes for benchmarking, we are working with the Global Alliance for Genomics and Health Benchmarking Team (benchmarking tools).
High-confidence small variant and homozygous reference calls are available for NA12878, the Ashkenazim trio, and the Chinese son with respect to GRCh37. Preliminary high-confidence calls with respect to GRCh38 are also available for NA12878. The latest version of these calls is under the latest directory for each genome on the GIAB FTP.
The consortium was initiated in a set of meetings in 2011 and 2012, and the consortium holds open, public workshops in January at Stanford University in Palo Alto, CA and in August/September at NIST in Gaithersburg, MD. Slides from workshops and conferences are available online. The consortium is open and welcomes new participants.
Stanford innovators and industry entrepreneurs have joined forces with the measurement experts from NIST to create a new engine powering the bioeconomy. It’s called JIMB — “Jim Bee” — the Joint Initiative for Metrology in Biology. JIMB unites people, platforms, and projects to underpin standards-based research and innovation in biometrology.
JIMB’s mission is to motivate standards-based measurement innovation to facilitate translation of basic science and technology development breakthroughs in genomics and synthetic biology.
By advancing biometrology, JIMB will push the boundaries of discovery science, accelerate technology development and dissemination, and generate reusable resources.
MicroRNAs (miRNAs) are a group of small non-coding RNA molecules that play a major role in posttranscriptional regulation of gene expression and are expressed in an organ-specific manner. One miRNA can potentially regulate the expression of several genes, depending on cell type and differentiation stage. They control every cellular process and their altered regulation is involved in human diseases. miRNAs are differentially expressed in the male and female gonads and have an organ-specific reproductive function. Exerting their affect through germ cells and gonadal somatic cells, miRNAs regulate key proteins necessary for gonad development. The role of miRNAs in the testes is only starting to emerge though they have been shown to be required for adequate spermatogenesis. In the ovary, miRNAs play a fundamental role in follicles’ assembly, growth, differentiation, and ovulation.
Deciphering the underlying causes of idiopathic male infertility is one of the main challenges in reproductive medicine. This is especially relevant in infertile patients displaying normal seminal parameters and no urogenital or genetic abnormalities. In these cases, the search for additional sperm biomarkers is of high interest. This study was aimed to determine the implications of the sperm miRNA expression profiles in the reproductive capacity of normozoospermic infertile individuals. The expression levels of 736 miRNAs were evaluated in spermatozoa from normozoospermic infertile males and normozoospermic fertile males analyzed under the same conditions. 57 miRNAs were differentially expressed between populations; 20 of them was regulated by a host gene promoter that in three cases comprised genes involved in fertility. The predicted targets of the differentially expressed miRNAs unveiled a significant enrichment of biological processes related to embryonic morphogenesis and chromatin modification. Normozoospermic infertile individuals exhibit a specific sperm miRNA expression profile clearly differentiated from normozoospermic fertile individuals. This miRNA cargo has potential implications in the individuals’ reproductive competence.
Circulating or “extracellular” miRNAs detected in biological fluids, could be used as potential diagnostic and prognostic biomarkers of several disease, such as cancer, gynecological and pregnancy disorders. However, their contributions in female infertility and in vitro fertilization (IVF) remain unknown. Polycystic ovary syndrome (PCOS) is a frequent endocrine disorder in women. PCOS is associated with altered features of androgen metabolism, increased insulin resistance and impaired fertility. Furthermore, PCOS, being a syndrome diagnosis, is heterogeneous and characterized by polycystic ovaries, chronic anovulation and evidence of hyperandrogenism, as well as being associated with chronic low-grade inflammation and an increased life time risk of type 2 diabetes. Altered miRNA levels have been associated with diabetes, insulin resistance, inflammation and various cancers. Studies have shown that circulating miRNAs are present in whole blood, serum, plasma and the follicular fluid of PCOS patients and that these might serve as potential biomarkers and a new approach for the diagnosis of PCOS. Presence of miRNA in mammalian follicular fluid has been demonstrated to be enclosed within microvesicles and exosomes or they can also be associated to protein complexes. The presence of microvesicles and exosomes carrying microRNAs in follicular fluid could represent an alternative mechanism of autocrine and paracrine communication inside the ovarian follicle. The investigation of the expression profiles of five circulating miRNAs (let-7b, miR-29a, miR-30a, miR-140 and miR-320a) in human follicular fluid from women with normal ovarian reserve and with polycystic ovary syndrome (PCOS) and their ability to predict IVF outcomes showed that these miRNAs could provide new helpful biomarkers to facilitate personalized medical care for oocyte quality in ART (Assisted Reproductive Treatment) and during IVF (In Vitro Fertilization).
LIVE 9/21 8AM to 10:55 AM Expoloring the Versatility of CRISPR/Cas9 at CHI’s 14th Discovery On Target, 9/19 – 9/22/2016, Westin Boston Waterfront, Boston
8:10 Functional Genomics Using CRISPR-Cas9: Technology and Applications
Neville Sanjana, Ph.D., Core Faculty Member, New York Genome Center and Assistant Professor, Department of Biology & Center for Genomics and Systems Biology, New York University
CRISPR Cas9 is easier to target to multiple genomic loci; RNA specifies DNA targeting; with zinc finger nucleases or TALEEN in the protein specifies DNA targeting
This feature of crisper allows you to make a quick big and cheap array of a GENOME SCALE Crisper Knock out (GeCKO) screening library
How do you scale up the sgRNA for whole genome?; for all genes in RefSeq, identify consitutive exons using RNA-sequencing data from 16 primary human tissue (alot of genes end with ‘gg’) changing the bases on 3’ side negates crisper system but changing on 5’ then crisper works fine
Rank sequences to be specific for target
Cloned array into lentiviral and put in selectable markers
GeCKO displays high consistency betweens reagents for the same gene versus siRNA; GeCKO has high screening sensitivity
98% of genome is noncoding so what about making a library for intronic regions (miRNA, promoter regions?)
So you design the sgRNA library by taking 100kb of gene-adjacent regions
They looked at CUL3; (data will soon be published in Science)
Do a transcription CHIP to verify the lack of binding of transcription factor of interest
Can also target histone marks on promoter and enhancer elements
TJ Cradick , Ph.D., Head of Genome Editing, CRISPR Therapeutics
NEHJ is down and dirty repair of single nonhomologous end but when have two breaks the NEHJ repair can introduce the inversions or deletions
High-throughput screens are fine but can limit your view of genomic context; genome searches pick unique sites so use bioinformatic programs to design specific guide Rna
Compared COSMID and CCTOP; 320 COSMID off-target sites, 333 CCtop off target
Young lab GUIDESeq program genome wide assay useful to design guides
If shorten guide may improve specificity; also sometime better sensitivity if lengthen guide
Manufacturing of autologous gene corrected product ex vivo gene correction (Vertex, Bayer, are partners in this)
They need to use a clones from multiple microarrays before using the GUidESeq but GUIDEseq is better for REMOVING the off targets than actually producing the sgRNA library you want (seems the methods for library development are not fully advanced to do this)
The score sometimes for the sgRNA design programs do not always give the best result because some sgRNAs are genome context dependent
9:10 Towards Combinatorial Drug Discovery: Mining Heterogeneous Phenotypes from Large Scale RNAi/Drug Perturbations
Arvind Rao, Ph.D., Assistant Professor, Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center
Bioinformatics in CRISPR screens: they looked at image analysis of light microscopy of breast cancer cells and looked for phenotypic changes
Then they modeled in a small pilot and then used the algorithm for 20,000 images (made morphometric measurements)
Can formulate training statistical algorithms to make a decision tree how you classify data points
Although their algorithms worked well there was also human input from scientists
Aggregate ranking of hits programs available on web like LINKS
@MDAndersonNews
10:25 CRISPR in Stem Cell Models of Eye Disease
Alexander Bassuk, M.D., Ph.D., Associate Professor of Pediatrics, Department of Molecular and Cellular Biology, University of Iowa
Blind athlete Michael Stone, biathlete, had eye disease since teenager helped fund and start the clinical trial for Starbardt disease; had one bad copy of ABCA4, heterozygous (inheritable in Ahkenazi Jewish) – a recessive inheritable mutation with juvenile macular degeneration
Also had another male in family with disease but he had another mutation in the RPGR gene
December 2015 paper Precision Medicine: Genetic Repair of retinitis pigmentosa in patient derived stem cells
They were able to correct the iPSCs in the RPGR gene derived from patient however low efficiency of repair, scarless repair, leaves changes in DNA, need clinical grade iPSCs, and need a humanized model of RPGR
@uiowa
10:55 CRISPR in Mouse Models of Eye Disease
Vinit Mahajan, M.D., Ph.D., Assistant Professor of Ophthalmology and Visual Sciences, University of Iowa College of Medicine
degeneration of the retina will see brown spots, the macula will often be preserved but retinal cells damaged but with RPGR have problems with peripheral vision, retinitis pigmentosa get tunnel vision with no peripheral vision (a mouse model of PDE6 Knockout recapitulates this phenotype)
the PDE6 is linked to the rhodopsin GTP pathway
rd1 -/- mouse has something that looks like retinal pigmentosa; has mutant PDE6; is actually a nonsense mutation in rd1 so they tried a crisper to fix in mice
with crisper fix of rd1 nonsense mutation the optic nerve looked comparible to normal and the retina structure restored
photoreceptors layers- some recovery but not complete
sequence results show the DNA is a mosaic so not correcting 100% but only 35% but stil leads to a phenotypic recovery; NHEJ was about 12% to 25% with large deletions
histology is restored in crspr repaired mice
CRSPR off target effects: WGS and analyze for variants SNV/indels, also looked at on target and off target regions; there were no off target SNVs indels while variants that did not pass quality control screening not a single SNV
Rhodopsin mutation accounts for a large % of patients (RhoD190N)
injection of gene therapy vectors: AAV vector carrying CRSPR and cas9 repair templates
CAPN mouse models
family in Iowa have dominant mutation in CAPN5; retinal degenerates
used CRSPR to generate mouse model with mutation in CAPN5 similar to family mutation
compared to other transgenic methods CRSPR is faster to produce a mouse model
To Follow LIVE CONFERENCE COVERAGE PLEASE FOLLOW ON TWITTER USING
Chapter 1: Evolution of the Foundation for Diagnostics and Pharmaceuticals Industries
1.1 Outline of Medical Discoveries between 1880 and 1980
1.2 The History of Infectious Diseases and Epidemiology in the late 19th and 20th Century
1.3 The Classification of Microbiota
1.4 Selected Contributions to Chemistry from 1880 to 1980
1.5 The Evolution of Clinical Chemistry in the 20th Century
1.6 Milestones in the Evolution of Diagnostics in the US HealthCare System: 1920s to Pre-Genomics
Chapter 2. The search for the evolution of function of proteins, enzymes and metal catalysts in life processes
2.1 The life and work of Allan Wilson
2.2 The evolution of myoglobin and hemoglobin
2.3 More complexity in proteins evolution
2.4 Life on earth is traced to oxygen binding
2.5 The colors of life function
2.6 The colors of respiration and electron transport
2.7 Highlights of a green evolution
Chapter 3. Evolution of New Relationships in Neuroendocrine States
3.1 Pituitary endocrine axis
3.2 Thyroid function
3.3 Sex hormones
3.4 Adrenal Cortex
3.5 Pancreatic Islets
3.6 Parathyroids
3.7 Gastointestinal hormones
3.8 Endocrine action on midbrain
3.9 Neural activity regulating endocrine response
3.10 Genomic Promise for Neurodegenerative Diseases, Dementias, Autism Spectrum, Schizophrenia, and Serious Depression
Chapter 4. Problems of the Circulation, Altitude, and Immunity
4.1 Innervation of Heart and Heart Rate
4.2 Action of hormones on the circulation
4.3 Allogeneic Transfusion Reactions
4.4 Graft-versus Host reaction
4.5 Unique problems of perinatal period
4.6. High altitude sickness
4.7 Deep water adaptation
4.8 Heart-Lung-and Kidney
4.9 Acute Lung Injury
4.10 Reconstruction of Life Processes requires both Genomics and Metabolomics to explain Phenotypes and Phylogenetics
Chapter 5. Problems of Diets and Lifestyle Changes
5.1 Anorexia nervosa
5.2 Voluntary and Involuntary S-insufficiency
5.3 Diarrheas – bacterial and nonbacterial
5.4 Gluten-free diets
5.5 Diet and cholesterol
5.6 Diet and Type 2 diabetes mellitus
5.7 Diet and exercise
5.8 Anxiety and quality of Life
5.9 Nutritional Supplements
Chapter 6. Advances in Genomics, Therapeutics and Pharmacogenomics
6.1 Natural Products Chemistry
6.2 The Challenge of Antimicrobial Resistance
6.3 Viruses, Vaccines and immunotherapy
6.4 Genomics and Metabolomics Advances in Cancer
6.5 Proteomics – Protein Interaction
6.6 Pharmacogenomics
6.7 Biomarker Guided Therapy
6.8 The Emergence of a Pharmaceutical Industry in the 20th Century: Diagnostics Industry and Drug Development in the Genomics Era: Mid 80s to Present
6.09 The Union of Biomarkers and Drug Development
6.10 Proteomics and Biomarker Discovery
6.11 Epigenomics and Companion Diagnostics
Chapter 7
Integration of Physiology, Genomics and Pharmacotherapy
7.1 Richard Lifton, MD, PhD of Yale University and Howard Hughes Medical Institute: Recipient of 2014 Breakthrough Prizes Awarded in Life Sciences for the Discovery of Genes and Biochemical Mechanisms that cause Hypertension
7.2 Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD
7.3 Diagnostics and Biomarkers: Novel Genomics Industry Trends vs Present Market Conditions and Historical Scientific Leaders Memoirs
7.4 Synthetic Biology: On Advanced Genome Interpretation for Gene Variants and Pathways: What is the Genetic Base of Atherosclerosis and Loss of Arterial Elasticity with Aging
Inotuzumab Ozogamicin: Success in relapsed/refractory Acute Lymphoblastic Leukemia (ALL)
Reporter: Aviva Lev-Ari, PhD, RN
About Inotuzumab Ozogamicin
Inotuzumab ozogamicin is an investigational antibody-drug conjugate (ADC) comprised of a monoclonal antibody (mAb) targeting CD22,9 a cell surface antigen expressed on approximately 90 percent of B-cell malignancies,10 linked to a cytotoxic agent. When inotuzumab ozogamicin binds to the CD22 antigen on malignant B-cells, it is internalized into the cell, where the cytotoxic agent calicheamicin is released to destroy the cell.11
Inotuzumab ozogamicin originates from a collaboration between Pfizer and Celltech, now UCB. Pfizer has sole responsibility for all manufacturing, clinical development and commercialization activities for this molecule.
Acute lymphoblastic leukemia (ALL)
is an aggressive type of leukemia with high unmet need and a poor prognosis in adults.4The current standard treatment is intensive, long-term chemotherapy.5 In 2015, it is estimated that 6,250 cases of ALL will be diagnosed in the United States6, with about 1 in 3 cases in adults. Only approximately 20 to 40 percent of newly diagnosed adults with ALL are cured with current treatment regimens.7 For patients with relapsed or refractory adult ALL, the five-year overall survival rate is less than 10 percent.8
REFERENCES
1 Fielding A. et al. Outcome of 609 adults after relapse of acute lymphoblastic leukemia (ALL); an MRC UKALL12/ECOG 2993 study. Blood. 2006; 944-950.
7 Manal Basyouni A. et al. Prognostic significance of survivin and tumor necrosis factor-alpha in adult acute lymphoblastic leukemia. doi:10.1016/j.clinbiochem.2011.08.1147.
8 Fielding A. et al. Outcome of 609 adults after relapse of acute lymphoblastic leukemia (ALL); an MRC UKALL12/ECOG 2993 study. Blood. 2006; 944-950.
10 Leonard J et al. Epratuzumab, a Humanized Anti-CD22 Antibody, in Aggressive Non-Hodgkin’s Lymphoma: a Phase I/II Clinical Trial Results. Clinical Cancer Research. 2004; 10: 5327-5334.
11 DiJoseph JF. Antitumor Efficacy of a Combination of CMC-544 (Inotuzumab Ozogamicin), a CD22-Targeted Cytotoxic Immunoconjugate of Calicheamicin, and Rituximab against Non-Hodgkin’s B-Cell Lymphoma. Clin Cancer Res. 2006; 12: 242-250.
Latest deaths in Juno trial underscore the need for greater transparency in clinical trials
quote
In recent years, numerous states have passed so-called “right-to-try” laws that encourage patients to seek access to experimental drugs outside of the clinical trial framework. In addition, libertarian activists and even some individuals associated with the incoming Trump administration continue to propose moving new medicines out into widespread use after only scant safety testing. That would increase the number of patients at risk for adverse outcomes, like the ones observed in the Juno trials, before we even know whether the drugs work.
The best way to identify transformative new medicines, protect patients from unexpectedly dangerous drugs, and avoid wasting health care resources is by subjecting experimental products to well-designed clinical trials that enroll sufficient numbers of patients and test relevant clinical outcomes that can then be independently reviewed by the experts at the FDA. When severe, unanticipated problems arise, the FDA needs a transparent and systematic evaluation process that can provide public insight into what happened and why. That would contribute to the progress of science and the development of the next generation of safer, better therapies.
Juno Therapeutics to Resume JCAR015 Phase II ROCKET Trial
SEATTLE–(BUSINESS WIRE)–Jul. 12, 2016– Juno Therapeutics, Inc. (Nasdaq: JUNO), a biopharmaceutical company focused on re-engaging the body’s immune system to revolutionize the treatment of cancer, today announced that the U.S. Food and Drug Administration has removed the clinical hold on the Phase II clinical trial of JCAR015 (known as the “ROCKET” trial) in adult patients with relapsed or refractory B cell acute lymphoblastic leukemia (r/r ALL).
Under the revised protocol, the ROCKET trial will continue enrollment using JCAR015 with cyclophosphamide pre-conditioning only.
Juno Therapeutics (NASDAQ:JUNO) acquires privately held Boston, MA-based RedoxTherapies. Juno’s primary aim of the deal was to secure an exclusive license to vipadenant, a small molecule adenosine A2a receptor antagonist that may disrupt key immunosuppressive pathways in the tumor microenvironment in certain cancers.
Redox licensed vipadenant from London-based Vernalis in October 2014. It was under development for the treatment of Parkinson’s disease by Biogen (NASDAQ:BIIB) but safety concerns scuppered the effort in 2010 despite encouraging efficacy in mid-stage studies. Biogen returned the rights to Vernalis in 2011.
Under the terms of the transaction, Juno will pay $10M in upfront cash plus undisclosed milestones.
Other related articles published in this open Access Online Scientific Journal include the following:
What does this mean for Immunotherapy? FDA put a temporary hold on Juno’s JCAR015, Three Death of Celebral Edema in CAR-T Clinical Trial and Kite Pharma announced Phase II portion of its CAR-T ZUMA-1 trial
Reporters and Curators: Stephen J Williams, PhD and Aviva Lev-Ari, PhD, RN
mRNA Data Survival Analysis, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 1: Next Generation Sequencing (NGS)
mRNA Data Survival Analysis
Curators: Larry H. Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN
SURVIV for survival analysis of mRNA isoform variation
The rapid accumulation of clinical RNA-seq data sets has provided the opportunity to associate mRNA isoform variations to clinical outcomes. Here we report a statistical method SURVIV (Survival analysis of mRNA Isoform Variation), designed for identifying mRNA isoform variation associated with patient survival time. A unique feature and major strength of SURVIV is that it models the measurement uncertainty of mRNA isoform ratio in RNA-seq data. Simulation studies suggest that SURVIV outperforms the conventional Cox regression survival analysis, especially for data sets with modest sequencing depth. We applied SURVIV to TCGA RNA-seq data of invasive ductal carcinoma as well as five additional cancer types. Alternative splicing-based survival predictors consistently outperform gene expression-based survival predictors, and the integration of clinical, gene expression and alternative splicing profiles leads to the best survival prediction. We anticipate that SURVIV will have broad utilities for analysing diverse types of mRNA isoform variation in large-scale clinical RNA-seq projects.
Eukaryotic cells generate remarkable regulatory and functional complexity from a finite set of genes. Production of mRNA isoforms through alternative processing and modification of RNA is essential for generating this complexity. A prevalent mechanism for producing mRNA isoforms is the alternative splicing of precursor mRNA1. Over 95% of the multi-exon human genes undergo alternative splicing2, 3, resulting in an enormous level of plasticity in the regulation of gene function and protein diversity. In the last decade, extensive genomic and functional studies have firmly established the critical role of alternative splicing in cancer4, 5, 6. Alternative splicing is involved in a full spectrum of oncogenic processes including cell proliferation, apoptosis, hypoxia, angiogenesis, immune escape and metastasis7, 8. These cancer-associated alternative splicing patterns are not merely the consequences of disrupted gene regulation in cancer but in numerous instances actively contribute to cancer development and progression. For example, alternative splicing of genes encoding the Bcl-2 family of apoptosis regulators generates both anti-apoptotic and pro-apoptotic protein isoforms9. Alternative splicing of the pyruvate kinase M (PKM) gene has a significant impact on cancer cell metabolism and tumour growth10. A transcriptome-wide switch of the alternative splicing programme during the epithelial–mesenchymal transition plays an important role in cancer cell invasion and metastasis11, 12.
RNA sequencing (RNA-seq) has become a popular and cost-effective technology to study transcriptome regulation and mRNA isoform variation13, 14. As the cost of RNA-seq continues to decline, it has been widely adopted in large-scale clinical transcriptome projects, especially for profiling transcriptome changes in cancer. For example, as of April 2015 The Cancer Genome Atlas (TCGA) consortium had generated RNA-seq data on over 11,000 cancer patient specimens from 34 different cancer types. Within the TCGA data, breast invasive carcinoma (BRCA) has the largest sample size of RNA-seq data covering over 1,000 patients, and clinical information such as survival times, tumour stages and histological subtypes is available for the majority of the BRCA patients15. Moreover, the median follow-up time of BRCA patients is ~400 days, and 25% of the patients have more than 1,200 days of follow-up. Collectively, the large sample size and long follow-up time of the TCGA BRCA data set allow us to correlate genomic and transcriptomic profiles to clinical outcomes and patient survival times.
To date, systematic analyses have been performed to reveal the association between copy number variation, DNA methylation, gene expression and microRNA expression profiles with cancer patient survival16, 17. By contrast, despite the importance of mRNA isoform variation and alternative splicing, there have been limited efforts in transcriptome-wide survival analysis of alternative splicing in cancer patients. Most RNA-seq studies of alternative splicing in cancer transcriptomes focus on identifying ‘cancer-specific’ alternative splicing events by comparing cancer tissues with normal controls (see refs 18, 19, 20, 21, 22, 23 for examples). A recent analysis of TCGA RNA-seq data identified 163 recurrent differential alternative splicing events between cancer and normal tissues of three cancer types, among which five were found to have suggestive survival signals for breast cancer at a nominal P-value cutoff of 0.05 (ref. 21). Some other studies reported a significant survival difference between cancer patient subgroups after stratifying patients with overall mRNA isoform expression profiles24, 25. However, systematic cancer survival analyses of alternative splicing at the individual exon resolution have been lacking. Two main challenges exist for survival analyses of mRNA isoform variation and alternative splicing using RNA-seq data. The first challenge is to account for the estimation uncertainty of mRNA isoform ratios inferred from RNA-seq read counts. The statistical confidence of mRNA isoform ratio estimation depends on the RNA-seq read coverage for the events of interest, with larger read coverage leading to a more reliable estimation14. Modelling the estimation uncertainty of mRNA isoform ratio is an essential component of RNA-seq analyses of alternative splicing, as shown by various statistical algorithms developed for detecting differential alternative splicing from multi-group RNA-seq data14, 26, 27, 28,29. The second challenge, which is a general issue in survival analysis, is to properly model the association of mRNA isoform ratio with survival time, while accounting for missing data in survival time because of censoring, that is, patients still alive at the end of the survival study, whose precise survival time would be uncertain. To date, no algorithm has been developed for survival analyses of mRNA isoform variation that accounts for these sources of uncertainty simultaneously.
Here we introduce SURVIV (Survival analysis of mRNA Isoform Variation), a statistical model for identifying mRNA isoform ratios associated with patient survival times in large-scale cancer RNA-seq data sets. SURVIV models the estimation uncertainty of mRNA isoform ratios in RNA-seq data and tests the survival effects of isoform variation in both censored and uncensored survival data. In simulation studies, SURVIV consistently outperforms the conventional Cox regression survival analysis that ignores the measurement uncertainty of mRNA isoform ratio. We used SURVIV to identify alternatively spliced exons whose exon-inclusion levels significantly correlated with the survival times of invasive ductal carcinoma (IDC) patients from the TCGA breast cancer cohort. Survival-associated alternative splicing events are identified in gene pathways associated with apoptosis, oxidative stress and DNA damage repair. Importantly, we show that alternative splicing-based survival predictors outperform gene expression-based survival predictors in the TCGA IDC RNA-seq data set, as well as in TCGA data of five additional cancer types. Moreover, the integration of clinical information, gene expression and alternative splicing profiles leads to the best prediction of survival time.
SURVIV statistical model
The statistical model of SURVIV assesses the association between mRNA isoform ratio and patient survival time. While the model is generic for many types of alternative isoform variation, here we use the exon-skipping type of alternative splicing to illustrate the model (Fig. 1a). For each alternative exon involved in exon-skipping, we can use the RNA-seq reads mapping to its exon-inclusion or -skipping isoform to estimate its exon-inclusion level (denoted as ψ, or PSI that is Per cent Spliced In14). A key feature of SURVIV is that it models the RNA-seq estimation uncertainty of exon-inclusion level as influenced by the sequencing coverage for the alternative splicing event of interest. This is a critical issue in accurate quantitative analyses of mRNA isoform ratio in large-scale RNA-seq data sets14, 26, 27, 28, 29. Therefore, SURVIV contains two major components: the first to model the association of mRNA isoform ratio with patient survival time across all patients, and the second to model the estimation uncertainty of mRNA isoform ratio in each individual patient (Fig. 1a).
Figure 1: The statistical framework of the SURVIV model.
(a) For each patient k, the patient’s hazard rate λk(t) is associated with the baseline hazard rate λ0(t) and this patient’s exon-inclusion level ψk. The association of exon-inclusion level with patient survival is estimated by the survival coefficient β. The exon-inclusion level ψk is estimated from the read counts for the exon-inclusion isoform ICk and the exon-skipping isoform SCk. The proportion of the inclusion and skipping reads is adjusted by a normalization function f that considers the lengths of the exon-inclusion and -skipping isoforms (see details in Results and Supplementary Methods). (b) A hypothetical example to illustrate the association of exon-inclusion level with patient survival probability over time Sk(t), with the survival coefficient β=−1 and a constant baseline hazard rate λ0(t)=1. In this example, patients with higher exon-inclusion levels have lower hazard rates and higher survival probabilities. (c) The schematic diagram of an exon-skipping event. The exon-inclusion reads ICk are the reads from the upstream splice junction, the alternative exon itself and the downstream splice junction. The exon-skipping reads SCk are the reads from the skipping splice junction that directly connects the upstream exon to the downstream exon.
Briefly, for any individual exon-skipping event, the first component of SURVIV uses a proportional hazards model to establish the relationship between patient k’s exon-inclusion level ψk and hazard rate λk(t).
For each exon, the association between the exon-inclusion level and patient survival time is reflected by the survival coefficient β. A positive β means increased exon inclusion is associated with higher hazard rate and poorer survival, while a negative β means increased exon inclusion is associated with lower hazard rate and better survival. λ0(t) is the baseline hazard rate estimated from the survival data of all patients (see Supplementary Methods for the detailed estimation procedure). A particular patient’s survival probability over time Sk(t) can be calculated from the patient-specific hazard rate λk(t) as . Figure 1b illustrates a simple example with a negative β=−1 and a constant baseline hazard rate λ0(t)=1, where higher exon-inclusion levels are associated with lower hazard rates and higher survival probabilities.
The second component of SURVIV models the exon-inclusion level and its estimation uncertainty in individual patient samples. As illustrated in Fig. 1c, the exon-inclusion level ψk of a given exon in a particular sample can be estimated by the RNA-seq read count specific to the exon inclusion isoform (ICk) and the exon-skipping isoform (SCk). Other types of alternative splicing and mRNA isoform variation can be similarly modelled by this framework29. Given the effective lengths (that is, the number of unique isoform-specific read positions) of the exon-inclusion isoform (lI) and the exon-skipping isoform (lS), the exon-inclusion level ψk can be estimated as . Assuming that the exon-inclusion read count ICk follows a binomial distribution with the total read count nk=ICk+SCk, we have:
The binomial distribution models the estimation uncertainty of ψk as influenced by the total read count nk, in which the parameter pk represents the proportion of reads from the exon-inclusion isoform, given the exon-inclusion level ψk adjusted by a length normalization function f(ψk) based on the effective lengths of the isoforms. The definitions of effective lengths for all basic types of alternative splicing patterns are described in ref. 29.
Distinct from conventional survival analyses in which predictors do not have estimation uncertainty, the predictors in SURVIV are exon-inclusion levels ψk estimated from RNA-seq count data, and the confidence of ψk estimate for a given exon in a particular sample depends on the RNA-seq read coverage. We use the statistical framework of survival measurement error model30 to incorporate the estimation uncertainty of isoform ratio in the proportional hazards model. Using a likelihood ratio test, we test whether the exon-inclusion levels have a significant association with patient survival over the null hypothesis H0:β=0. The false discovery rate (FDR) is estimated using the Benjamini and Hochberg approach31. Details of the parameter estimation and likelihood ratio test in SURVIV are described in Supplementary Methods.
Figure 2: Simulation studies to assess the performance of SURVIV and the importance of modelling the estimation uncertainty of mRNA isoform ratio.
We compared our SURVIV model with Cox regression using point estimates of exon-inclusion levels, which does not consider the estimation uncertainty of the mRNA isoform ratio. (a) To study the effect of RNA-seq depth, we simulated the mean total splice junction read counts equal to 5, 10, 20, 50, 80 and 100 reads. We generated two sets of simulations with and without data-censoring. For each simulation, the true-positive rate (TPR) at 5% false-positive rate is plotted. The inset figure shows the empirical distribution of the mean total splice junction read counts in the TCGA IDC RNA-seq data (x axis in the log10 scale). (b) To faithfully represent the read count distribution in a real data set, we performed another simulation with read counts directly sampled from the TCGA IDC data. Sampled read counts were then multiplied by different factors ranging from 10 to 300% to simulate data sets with different RNA-seq read depth. Continuous and dashed lines represent the performance of SURVIV and Cox regression, respectively. Red lines represent the area under curve (AUC) of the ROC curve (TPR versus false-positive rate plot). Black lines represent the TPR at 5% false-positive rate.
Using these simulated data, we compared SURVIV with Cox regression in two settings, without or with censoring of the survival time. In the setting without censoring, the death and survival time of each individual is known. In the setting with censoring, certain individuals are still alive at the end of the survival study. Consequently, these patients have unknown death and survival time. Here, in the simulation with censoring, we assumed that 85% of the patients were still alive at the end of the study, similar to the censoring rate of the TCGA IDC data set. In both settings and with different depths of RNA-seq coverage, SURVIV consistently outperformed Cox regression in the true-positive rate at the same false-positive rate of 5% (Fig. 2a). As expected, we observed a more significant improvement in SURVIV over Cox regression when the RNA-seq read coverage was low (Fig. 2a).
To more faithfully recapitulate the read count distribution in a real cancer RNA-seq data set, we performed another simulation study with read counts directly sampled from the TCGA IDC data. To assess the influence of RNA-seq read depth on the performance of SURVIV and Cox regression, sampled read counts were then multiplied by different factors ranging from 10 to 300% to simulate data sets with different RNA-seq read depths (Fig. 2b). The TCGA IDC data set has an average RNA-seq depth of ~60 million paired-end reads per patient. Thus, the read depth of these simulated RNA-seq data sets ranged from ~6 million reads to 180 million reads per patient, representing low-coverage RNA-seq studies designed primarily for gene expression analysis32 up to high-coverage RNA-seq studies designed primarily for alternative isoform analysis29. At all levels of RNA-seq depth, SURVIV consistently outperformed Cox regression, as reflected by the area under curve of the receiver operating characteristic (ROC) curve as well as the true-positive rate at 5% false-positive rate (Fig. 2b). The improvement of SURVIV over Cox regression was particularly prominent when the read depth was low. For example, at 10% read depth, SURVIV had 7% improvement in area under curve (68% versus 61%) and 8% improvement in the true-positive rate at 5% false-positive rate (46% versus 38%). Collectively, these simulation results suggest that SURVIV achieves a higher accuracy by accounting for the estimation uncertainty of mRNA isoform ratio in RNA-seq data.
SURVIV analysis of TCGA IDC breast cancer data
To illustrate the practical utility of SURVIV, we used it to analyse the overall survival time of 682 IDC patients from the TCGA breast cancer (BRCA) RNA-seq data set (see Methods for details of the data source and processing pipeline). We chose to analyse IDC because it is the most frequent type of breast cancer33, comprising ~70% of patients in the TCGA breast cancer data set. To control for the effects of significant clinical parameters such as tumour stage and subtype and identify alternative splicing events associated with patient outcomes across multiple molecular and clinical subtypes, we followed the procedure of Croce and colleagues in analysing mRNA and microRNA prognostic signature of IDC33 and stratified the patients according to their clinical parameters. We then conducted SURVIV analysis in 26 clinical subgroups with at least 50 patients in each subgroup. We identified 229 exon-skipping events associated with patient survival in multiple clinical subgroups that met the criteria of SURVIV P-value≤0.01 in at least two subgroups of the same clinical parameter (cancer subtype, stage, lymph node, metastasis, tumour size, oestrogen receptor status, progesterone receptor status, HER2 status and age as shown in Fig. 3). DAVID (Database for Annotation, Visualization and Integrated Discovery) Gene Ontology analyses34 of the 229 alternative splicing events suggest an enrichment of genes in cancer-related functional categories such as intracellular signalling, apoptosis, oxidative stress and response to DNA damage (Supplementary Fig. 1). Table 1 shows a few selected examples of survival-associated alternative splicing events in cancer-related genes. Using two-means clustering of each individual exon’s inclusion levels, the 682 IDC patients can be segregated into two subgroups with significantly different survival times as illustrated by the Kaplan–Meier survival plot (Fig. 4). We also carried out hierarchical clustering of IDC patients using 176 survival-associated alternative exons (P≤0.01; SURVIV analysis of all IDC patients). Using the exon-inclusion levels of these 176 exons, we clustered IDC patients into three major subgroups, with 95, 194 and 389 patients, respectively. As illustrated by the Kaplan–Meier survival plots, the three subgroups had significantly different survival times (Supplementary Fig. 2).
Figure 3: SURVIV analysis of exon-skipping events in the TCGA IDC RNA-seq data set.
IDC patients are stratified into multiple clinical subgroups based on clinical parameters including cancer subtype, stage, lymph node status, metastasis, tumour size, oestrogen receptor status, progesterone receptor status, HER2 status and age. Only clinical subgroups with at least 50 patients are included in further analyses. Numbers of patients in the subgroups are indicated next to the names of the subgroups. Shown in the heatmap are the log10 SURVIV P-values of the 229 exons associated with patient survival (P≤0.01) in at least two subgroups of the same class of clinical parameters. Turquoise colour indicates positive correlation that higher exon-inclusion levels are associated with higher survival probabilities. Magenta colour indicates negative correlation that lower exon-inclusion levels are associated with higher survival probabilities.
Figure 4: Kaplan–Meier survival plots of IDC patients stratified by two-means clustering of the exon-inclusion levels of four survival-associated alternative splicing events.
Clustering was generated for each of the four exons separately. Black lines represent patients with high exon-inclusion levels. Red lines represent patients with low exon-inclusion levels. The P-values are from SURVIV analysis of the TCGA IDC RNA-seq data. (a) ATRIP. (b) BCL2L11. (c) CD74. (d) PCBP4.
Figure 5: Alternative splicing of STAT5A exon 5 is significantly associated with IDC patient survival.
(a) The gene structure of the STAT5A full-length isoform compared to the ΔEx5 isoform skipping the 5th exon. (b) Kaplan–Meier survival plot of IDC patients stratified by two-means clustering using exon-inclusion levels of STAT5A exon 5. The 420 patients in Group 1 (average exon 5 inclusion level=95%) have significantly higher survival probabilities than the 262 patients in Group 2 (average exon 5 inclusion level=85%) (SURVIV P=6.8e−4). (c) Exon 5 inclusion levels of IDC patients stratified by two-means clustering using exon 5 inclusion levels. Group 1 has 420 patients with average exon-inclusion level at 95%. Group 2 has 262 patients with average exon-inclusion level at 85%. (d) STAT5A exon 5 inclusion levels in normal breast tissues versus breast cancer tumour samples. Exon-inclusion levels are extracted from 86 TCGA breast cancer patients with matched normal and tumour samples. Normal breast tissues have average exon 5 inclusion level at 95%, compared to 91% average exon-inclusion level in tumour samples. Error bars represent 95% confidence interval of the mean.
Figure 6: Splicing factor regulatory network of survival-associated alternative splicing events in IDC.
(a–c) Kaplan–Meier survival plots of IDC patients stratified by the gene expression levels of three splicing factors: TRA2B (a, Cox regression P=1.8e−4), HNRNPH1 (b, P=3.4e−4) and SFRS3 (c, P=2.8e−3). Black lines represent patients with high gene expression levels. Red lines represent patients with low gene expression levels. (d) The exon-inclusion levels of a DHX30 alternative exon are negatively correlated with TRA2B gene expression levels (robust correlation coefficient r=−0.26, correlation P=1.2e−17). (e) The exon-inclusion levels of a MAP3K4 alternative exon are positively correlated withHNRNPH1 gene expression levels (robust correlation coefficient r=0.16, correlation P=2.6e−06). (f) A splicing co-expression network of the three splicing factors and their correlated survival-associated alternative exons. In total, 84 survival-associated alternative exons are significantly correlated with the three splicing factors. The positive/negative correlation between splicing factors and alternative exons is represented by blue/red lines, respectively. Exons whose inclusion levels are positively/negatively correlated with survival times are represented by blue/red dots, respectively. The size of the splicing factor circles is proportional to the number of correlated exons within the network.
Figure 7: Cross-validation of different classes of IDC survival predictors measured by the C-index
A C-index of 1 indicates perfect prediction accuracy and a C-index of 0.5 indicates random guess. The plots indicate the distribution of C-indexes from 100 rounds of cross-validation. The centre value of the box plot is the median C-index from 100 rounds of cross-validation. The notch represents the 95%confidence interval of the median. The box represents the 25 and 75% quantiles. The whiskers extended out from the box represent the 5 and 95% quantiles. Two-sided Wilcoxon test was used to compare different survival predictors. The different classes of predictors are: (a) clinical information (median C-index 0.67). (b) Gene expression (median C-index 0.68). (c) Alternative splicing (median C-index 0.71). (d) Clinical information+gene expression (median C-index 0.69). (e) Clinical information+alternative splicing (median C-index 0.73). (f) Clinical information+gene expression+alternative splicing (median C-index 0.74). Note that ‘Gene’ refers to ‘Gene-level expression’ in these plots.
Next, we carried out the SURVIV analysis in five additional cancer types in TCGA, including GBM (glioblastoma multiforme), KIRC (kidney renal clear cell carcinoma), LGG (lower grade glioma), LUSC (lung squamous cell carcinoma) and OV (ovarian serous cystadenocarcinoma). As expected, the number of significant events at different FDR or P-value significance cutoffs varied across cancer types, with LGG having the strongest survival-associated alternative splicing signals with 660 significant exon-skipping events at FDR≤5% (Supplementary Data 3 and 4). Strikingly, regardless of the number of significant events, alternative splicing-based survival predictors outperformed gene expression-based survival predictors across all cancer types (Supplementary Fig. 3), consistent with our initial observation on the IDC data set.
Alternative processing and modification of mRNA, such as alternative splicing, allow cells to generate a large number of mRNA and protein isoforms with diverse regulatory and functional properties. The plasticity of alternative splicing is often exploited by cancer cells to produce isoform switches that promote cancer cell survival, proliferation and metastasis7, 8. The widespread use of RNA-seq in cancer transcriptome studies15, 47, 48 has provided the opportunity to comprehensively elucidate the landscape of alternative splicing in cancer tissues. While existing studies of alternative splicing in large-scale cancer transcriptome data largely focused on the comparison of splicing patterns between cancer and normal tissues or between different subtypes of cancer18, 21, 49, additional computational tools are needed to characterize the clinical relevance of alternative splicing using massive RNA-seq data sets, including the association of alternative splicing with phenotypes and patient outcomes.
We have developed SURVIV, a novel statistical model for survival analysis of alternative isoform variation using cancer RNA-seq data. SURVIV uses a survival measurement error model to simultaneously model the estimation uncertainty of mRNA isoform ratio in individual patients and the association of mRNA isoform ratio with survival time across patients. Compared with the conventional Cox regression model that uses each patient’s mRNA isoform ratio as a point estimate, SURVIV achieves a higher accuracy as indicated by simulation studies under a variety of settings. Of note, we observed a particularly marked improvement of SURVIV over Cox regression for low- and moderate-depth RNA-seq data (Fig. 2b). This has important practical value because many clinical RNA-seq data sets have large sample size but relatively modest sequencing depth.
Using the TCGA IDC breast cancer RNA-seq data of 682 patients, SURVIV identified 229 alternative splicing events associated with patient survival time, which met the criteria of SURVIVP-values≤0.01 in multiple clinical subgroups. While the statistical threshold seemed loose, several lines of evidence suggest the functional and clinical relevance of these survival-associated alternative splicing events. These alternative splicing events were frequently identified and enriched in the gene functional groups important for cancer development and progression, including apoptosis, DNA damage response and oxidative stress. While some of these events may simply reflect correlation but not causal effect on cancer patient survival, other events may play an active role in regulating cancer cell phenotypes. For example, a survival-associated alternative splicing event involving exon 5 of STAT5A is known to regulate the activity of this transcription factor with important roles in epithelial cell growth and apoptosis37. Using a co-expression network analysis of splicing factor to exon correlation across all patients, we identified three splicing factors (TRA2B, HNRNPH1 and SFRS3) as potential hubs of the survival-associated alternative splicing network of IDC. The expression levels of all three splicing factors were negatively associated with patient survival times (Fig. 6a–c), and both TRA2B and HNRNPH1 were previously reported to have an impact on cancer-related molecular pathways40, 41, 42, 43, 44, 45. Finally, despite the limited power in detecting individual events, we show that the survival-associated alternative splicing events can be used to construct a predictor for patient survival, with an accuracy higher than predictors based on clinical parameters or gene expression profiles (Fig. 7). This further demonstrates the potential biological relevance and clinical utility of the identified alternative splicing events.
We performed cross-validation analyses to evaluate and compare the prognostic value of alternative splicing, gene expression and clinical information for predicting patient survival, either independently or in combination. As expected, the combined use of all three types of information led to the best prediction accuracy. Because we used penalized regression to build the prediction model, combining information from multiple layers of data did not necessarily increase the number of predictors in the model. The perhaps more surprising and intriguing result is that alternative splicing-based predictors appear to outperform gene expression-based predictors when used alone and when either type of data was combined with clinical information (Fig. 7). We observed the same trend in five additional cancer types (Supplementary Fig. 3). We note that this finding was consistent with a previous report that cancer subtype classification based on splicing isoform expression performed better than gene expression-based classification25. While this trend seems counterintuitive because accurate estimation of gene expression requires much lower RNA-seq depth than accurate estimation of alternative splicing29, one possible explanation may be the inherent characteristic of isoform ratio data. By definition, mRNA isoform ratio is estimated as the ratio of multiple mRNA isoforms from a single gene. Therefore, mRNA isoform ratio data have a ‘built-in’ internal control that could be more robust against certain artefacts and confounding issues that influence gene expression estimates across large clinical RNA-seq data sets, such as poor sample quality and RNA degradation12. Regardless of the reasons, our data call for further studies to fully explore the utility of mRNA isoform ratio data for various clinical research applications.
The SURVIV source code is available for download at https://github.com/Xinglab/SURVIV. SURVIV is a general statistical model for survival analysis of mRNA isoform ratio using RNA-seq data. The current statistical framework of SURVIV is applicable to RNA-seq based count data for all basic types of alternative splicing patterns involving two isoform choices from an alternatively spliced region, such as exon-skipping, alternative 5′ splice sites, alternative 3′ splice sites, mutually exclusive exons and retained introns, as well as other forms of alternative isoform variation such as RNA editing. With the rapid accumulation of clinical RNA-seq data sets, SURVIV will be a useful tool for elucidating the clinical relevance and potential functional significance of alternative isoform variation in cancer and other diseases.
Preclinical Data Presented at ASCO 2016 Annual Meeting Demonstrate that Single-Agent NKTR-214 Produces a Large Increase in Tumor-Infiltrating Lymphocytes to Provide Durable Anti-Tumor Activity
SAN FRANCISCO, June 6, 2016 /PRNewswire/ — Nektar Therapeutics (NASDAQ: NKTR) today announced new preclinical data for NKTR-214, an immuno-stimulatory CD-122 biased cytokine currently being evaluated in cancer patients with solid tumors in a Phase 1/2 clinical trial being conducted at MD Anderson Cancer Center and Yale Cancer Center. The new preclinical data presented demonstrate that treatment with single-agent NKTR-214 mobilizes tumor-killing T cells into colon cancer tumors. In addition, mouse pharmacodynamics data demonstrated that a single dose of NKTR-214 can increase and sustain STAT5 phosphorylation (a marker of IL-2 pathway activation) through one week post-dose. These data were presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, IL from June 3-7, 2016.
“These latest data build upon our growing body of preclinical evidence demonstrating the unique mechanism of NKTR-214,” added Jonathan Zalevsky, PhD, Vice President, Biology and Preclinical Development at Nektar Therapeutics. “The studies presented at ASCO show that NKTR-214 promotes tumor-killing immune cell accumulation directly in the tumor, providing a mechanistic basis for its significant anti-tumor activity in multiple preclinical tumor models. The ability to grow TILs1 in vivo and replenish the immune system is exceptionally important. We’ve now learned that many human tumors lack sufficient TIL populations and the addition of the NKTR-214 TIL-enhancing MOA could improve the success of many checkpoint inhibitors and other agents, and allow more patients to benefit from immuno-therapy.”
In studies previously published for NKTR-214, when mice bearing established breast cancer tumors are treated with NKTR-214 and anti-CTLA4 (a checkpoint inhibitor therapy known as ipilimumab for human treatment), a large proportion of mice become tumor-free. Anti-tumor immune memory was demonstrated when tumor-free mice were re-challenged by implant with a new breast cancer tumor and then found to clear the new tumor, without further therapy. The new data presented at ASCO demonstrate that upon re-challenge, there is a rapid expansion of newly proliferative CD8 T cells and particularly CD8 effector memory T cells. Both cell populations were readily detectable in multiple tissues (blood, spleen, and lymph nodes) and likely contribute to the anti-tumor effect observed in these animals. Adoptive transfer studies confirmed the immune-memory effect as transplant of splenocytes from tumor-free mice into naïve recipients provided the ability to resist tumor growth.
“NKTR-214 provides a highly unique immune activation profile that allows it to access the IL-2 pathway without pushing the immune system into pathological overdrive,” said Dr. Steve Doberstein, Senior Vice President and Chief Scientific Officer. “NKTR-214’s unique immune-stimulatory profile and antibody-like dosing schedule positions it as a potentially important medicine within the immuno-oncology landscape.”
The data presentation at ASCO entitled, “Immune memory in nonclinical models after treatment with NKTR-214, an engineered cytokine biased towards expansion of CD8+ T cells in tumor,” can be accessed at http://www.nektar.com/2016_NKTR-214_ASCO_poster.pdf
NKTR-214 is a CD122-biased agonist designed to stimulate the patient’s own immune system to kill tumor cells by preferentially activating production of specific immune cells which promote tumor killing, including CD8-positive T cells and Natural Killer (NK) cells, within the tumor micro-environment. CD122, which is also known as the Interleukin-2 receptor beta subunit, is a key signaling receptor that is known to increase proliferation of these types of T cells.2
In preclinical studies, NKTR-214 demonstrated a highly favorable mean ratio of 450:1 within the tumor micro-environment of CD8-positive effector T cells relative to regulatory T cells.3 Furthermore, the pro-drug design of NKTR-214 enables an antibody-like dosing regimen for an immuno-stimulatory cytokine.4
About the NKTR-214 Phase 1/2 Clinical Study
A Phase 1/2 clinical study is underway to evaluate NKTR-214 in patients with advanced solid tumors, including melanoma, renal cell carcinoma and non-small cell lung cancer. The first stage of this study, which is expected to be complete in the second half of 2016, is evaluating escalating doses of single-agent NKTR-214 treatment in approximately 20 patients with solid tumors. The primary objective of the first stage of the study is to evaluate the safety and efficacy of NKTR-214 and to identify a recommended Phase 2 dose. In addition, the study will also assess the immunologic effect of NKTR-214 on TILs and other immune cells in both blood and tumor tissue, and it will also include TCR repertoire profiling. Dose expansion cohorts are planned to evaluate NKTR-214 in specific tumor types, including melanoma, renal cell carcinoma and non-small cell lung cancer.
The NKTR-214 clinical study is being conducted initially at two primary investigator sites: MD Anderson Cancer Center under Drs. Patrick Hwu and Adi Diab; and Yale Cancer Center, under Drs. Mario Sznol and Michael Hurwitz. Patients and physicians interested in the ongoing NKTR-214 study can visit the “Clinical Trials” section of www.mdanderson.org using identifier 2015-0573 or visit https://medicine.yale.edu/cancer/research/trials/active/858.trial.
About Nektar
Nektar Therapeutics has a robust R&D pipeline and portfolio of approved partnered medicines in oncology, pain, immunology and other therapeutic areas. In the area of oncology, Nektar is developing NKTR-214, an immuno-stimulatory CD122-biased agonist, that is in Phase 1/2 clinical development for patients with solid tumors. ONZEALD™ (etirinotecan pegol), a long-acting topoisomerase I inhibitor, is being developed for patients with advanced breast cancer and brain metastases and is partnered with Daiichi Sankyo in Europe. In the area of pain, Nektar has an exclusive worldwide license agreement with AstraZeneca for MOVANTIK™ (naloxegol), the first FDA-approved once-daily oral peripherally-acting mu-opioid receptor antagonist (PAMORA) medication for the treatment of opioid-induced constipation (OIC), in adult patients with chronic, non-cancer pain. The product is also approved in the European Union as MOVENTIG® (naloxegol) and is indicated for adult patients with OIC who have had an inadequate response to laxatives. The AstraZeneca agreement also includes NKTR-119, an earlier stage development program that is a co-formulation of MOVANTIK and an opioid. NKTR-181, a wholly owned mu-opioid analgesic molecule for chronic pain conditions, is in Phase 3 development. In hemophilia, Nektar has a collaboration agreement with Baxalta for ADYNOVATE™ [Antihemophilic Factor (Recombinant)], a longer-acting PEGylated Factor VIII therapeutic approved in the U.S. and Japan for patients over 12 with hemophilia A. In anti-infectives, the company has two collaborations with Bayer Healthcare, Cipro Inhale in Phase 3 for non-cystic fibrosis bronchiectasis and Amikacin Inhale in Phase 3 for patients with Gram-negative pneumonia.
Immune memory in nonclinical models after treatment with NKTR-214, an engineered cytokine biased towards expansion of CD8+ T cells in tumor
Deborah H. Charych, Vidula Dixit, Peiwen Kuo, Werner Rubas, Janet Cetz, Rhoneil Pena, John L. Langowski, Ute Hoch, Murali Addepalli, Stephen K. Doberstein, Jonathan Zalevsky | Nektar Therapeutics, San Francisco, CA
INTRODUCTION
• Recombinant human IL-2 (aldesleukin) is an effective immunotherapy for metastatic melanoma and renal cell carcinoma with durable responses in ~ 10% of patients, but side effects limit its use
• IL-2 has pleiotropic immune modulatory effects[1] which may limit its anti-tumor activity
• Binding to the heterodimeric receptor IL-2Rβγ leads to expansion of tumor-killing CD8+ memory effector T cells and NK cells
• Binding to the heterotrimeric IL-2Rαβγ leads to expansion of suppressive Treg which antagonizes anti-tumor immunity
• NKTR-214 delivers a controlled, sustained and biased signal through the IL-2 receptor pathway.
• The prodrug design of NKTR-214 comprises recombinant human IL-2 chemically conjugated with multiple releasable chains of polyethylene glycol (PEG)
• Slow release of PEG chains over time generates active PEG-conjugated IL-2 metabolites of increasing bioactivity, improving pharmacokinetics and tolerability compared to aldesleukin
• Active NKTR-214 metabolites bias IL-2R activation towards CD8 T cells over Treg[2]
NKTR-214 was engineered to release PEG at physiological pH with predictable kinetics.
The kinetics of PEG release was evaluated in vitro by quantifying free PEG over time using HPLC.
The release of PEG from IL-2 followed predictable kinetics. Symbols = measured data; Line = curve fit based on first order kinetic model. R2 =0.997
In mice, a single dose of NKTR-214 gradually builds and sustains pSTAT5 levels through seven days post-dose. In contrast, IL-2 produces a rapid burst of pSTAT5 that declines four hours post-dose
C57BL/6 mice were treated with either one dose of NKTR-214 (blue) or aldesleukin (red); blood samples were collected at various time points post-dose. pSTAT5 in peripheral blood CD3+ T cells was assessed using flow cytometry. Top graph is an inset showing the 0-4 hour time period. Bottom graph shows the full 10 day time course of the experiment. Histograms on right depict pSTAT5 MFI for IL-2 (red) and NKTR-214 (blue)
Mobilization of lymphocytes from the periphery into the tumor is an inherent property of NKTR-214
A. C57BL/6 mice bearing established subcutaneous B16F10 melanoma tumors were dosed with either NKTR-214 (2 mg/kg, i.v., q9d x2) or aldesleukin (3 mg/kg, i.p. bid x5, two cycles)
B. Tumor infiltrating lymphocytes were analyzed by flow cytometry from treated tumors (*, p<0.05 relative to vehicle; ‡, p<0.05 relative to aldesleukin)
C. Tumor growth inhibition from NKTR-214 was compromised when NKTR-214 was co-administered with Fingolimod, an agent that blocks lymphocyte trafficking.[3], (C57BL/6 mice, B16F10 subcutaneous mouse melanoma). Fingolimod was dosed qd p.o. 5 ug/animal. Lymphocyte count in blood was significantly reduced as expected, for study duration. Tumor growth inhibition (TGI) shown at study endpoint. (One-way ANOVA, Dunnets multiple comparison test ***=p<0.001, ****=p<0.0001 vs. vehicle; #=p<0.05 vs. NKTR-214)
D. Balb/c mice bearing established subcutaneous CT26 colon tumors were dosed with NKTR-214, 0.8 mg/kg i.v. q9dx3 or checkpoint inhibitors, 200 ug/mouse 2x/week. (*, p<0.05 relative to vehicle) E. T cell infiltration into mouse CT26 colon tumors was determined by TIL DNA fraction 7 days post-dose, Adaptive Biotechnologies, n=4 per group
The combination of NKTR-214 and anti-CTLA4 delivers durable anti-tumor activity and vigorous immune memory recall Durable treatment-induced immune memory demonstrated by:
A. Rejection of new tumors implanted into tumor-free mice without further therapy,
Durable anti-tumor immune memory demonstrated by rechallenging treated tumor-free mice with new tumors. New tumors can be eliminated without further treatment.
Balb/c mice initially were implanted with EMT6 murine breast tumors and treated with NKTR-214 0.8mg/kg q9dx3 and anti-CTLA4 200ug/mouse 2x/week. Several weeks later, tumor-free mice were rechallenged with tumor cells EMT6 (blue), CT26 (red) or vehicle (black). Tumor outgrowth occurred when non-related CT26 tumors were implanted. In contrast, tumors were rejected by up to 100% of mice when the same EMT6 tumors were implanted (2×106 EMT6 or CT26 cells)
B. Production of proliferating CD8 effector memory T cells in 3 tissues after tumor rechallenge and
Durable anti-tumor immune memory demonstrated by vigorous proliferative (Ki67+) CD8 T cell responses. The increased activity of these cells is greatest for mice previously treated with NKTR-214 and anti-CTLA4, rechallenged with the same tumor type (blue) compared to a different tumor (red) or mice who were never treated (brown, gray). Treated mice received therapy ~6 months prior. Top row shows total CD8+ cells, bottom row shows effector memory CD8+ in 3 tissues. The role of CD8 and NK cells in mediating the anti-tumor response was previously shown using depletion antibodies.[2]
Mice that became tumor-free from NKTR-214+anti-CTLA4 therapy and treatment naïve controls were rechallenged ~6 months later with either EMT6, CT26 or Sham buffer. No further treatment was given. Immune cells in spleen, lymph and blood were enumerated by flow cytometry, n=4/group. Graphs indicate proliferating Ki67+ total CD8 T cells (top) and effector memory CD8+ CD44hi CD67L-lo (bottom).
C. Transference of immune memory from tumor-free mice to recipient mice.
Durable anti-tumor immune memory demonstrated by adoptive spleen transfer from tumor-free mice to recipient mice. The recipients resist tumor growth without further treatment.
Mouse EMT6 breast tumors were implanted in recipient mice 1 day after receiving spleens from tumor-free mice or naïve mice; (****=p<0.0001 vs. normal control , two way ANOVA Tukey’s multiple comparison test, ns = non-significant)
CONCLUSIONS
• NKTR-214 mechanism of action delivers a controlled, sustained and biased signal to the IL-2 pathway, potentially mitigating systemic toxicities observed from bolus activation by IL-2 (aldesleukin)
• NKTR-214 provides marked efficacy in multiple tumor models, alone or in combination, using lower doses of reduced administration frequency
• Mobilization of T cells from the periphery into the tumor is an inherent property of NKTR-214
• NKTR-214 mechanism enables durable complete anti-tumor response with immune memory recall when combined with anti-CTLA4
• Treatment provides tumor-free mice that consistently eliminate new tumors even in the absence of further therapy • Mice becoming tumor-free from prior treatment reject new tumors by mounting a vigorous CD8+ effector memory response up to 6 months post-therapy
• Adoptive spleen transfer from tumor-free mice confers an anti-tumor response in recipient mice in the absence of further therapy
• NKTR-214 is being evaluated in an ongoing outpatient Phase 1/2 clinical trial for the treatment of solid tumors