Publications by authors named "Victor Kofia"

6 Publications

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Modeling Cellular Response in Large-Scale Radiogenomic Databases to Advance Precision Radiotherapy.

Cancer Res 2019 12 26;79(24):6227-6237. Epub 2019 Sep 26.

Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.

Radiotherapy is integral to the care of a majority of patients with cancer. Despite differences in tumor responses to radiation (radioresponse), dose prescriptions are not currently tailored to individual patients. Recent large-scale cancer cell line databases hold the promise of unravelling the complex molecular arrangements underlying cellular response to radiation, which is critical for novel predictive biomarker discovery. Here, we present RadioGx, a computational platform for integrative analyses of radioresponse using radiogenomic databases. We fit the dose-response data within RadioGx to the linear-quadratic model. The imputed survival across a range of dose levels (AUC) was a robust radioresponse indicator that correlated with biological processes known to underpin the cellular response to radiation. Using AUC as a metric for further investigations, we found that radiation sensitivity was significantly associated with disruptive mutations in genes related to nonhomologous end joining. Next, by simulating the effects of different oxygen levels, we identified putative genes that may influence radioresponse specifically under hypoxic conditions. Furthermore, using transcriptomic data, we found evidence for tissue-specific determinants of radioresponse, suggesting that tumor type could influence the validity of putative predictive biomarkers of radioresponse. Finally, integrating radioresponse with drug response data, we found that drug classes impacting the cytoskeleton, DNA replication, and mitosis display similar therapeutic effects to ionizing radiation on cancer cell lines. In summary, RadioGx provides a unique computational toolbox for hypothesis generation to advance preclinical research for radiation oncology and precision medicine. SIGNIFICANCE: The RadioGx computational platform enables integrative analyses of cellular response to radiation with drug responses and genome-wide molecular data. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/24/6227/F1.large.jpg..
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http://dx.doi.org/10.1158/0008-5472.CAN-19-0179DOI Listing
December 2019

Identifying clusters of -regulatory elements underpinning TAD structures and lineage-specific regulatory networks.

Genome Res 2019 10 18;29(10):1733-1743. Epub 2019 Sep 18.

Princess Margaret Cancer Centre, Toronto, Ontario M5G 1L7, Canada.

Cellular identity relies on cell-type-specific gene expression controlled at the transcriptional level by -regulatory elements (CREs). CREs are unevenly distributed across the genome, giving rise to individual CREs and clusters of CREs (COREs). Technical and biological features hinder CORE identification. We addressed these issues by developing an unsupervised machine learning approach termed clustering of genomic regions analysis method (CREAM). CREAM automates CORE detection from chromatin accessibility profiles that are enriched in CREs strongly bound by master transcription regulators, proximal to highly expressed and essential genes, and discriminating cell identity. Although COREs share similarities with super-enhancers, we highlight differences in terms of the genomic distribution and structure of these -regulatory units. We further show the enhanced value of COREs over super-enhancers to identify master transcription regulators, highly expressed and essential genes defining cell identity. COREs enrich at topologically associated domain (TAD) boundaries. They are also preferentially bound by the chromatin looping factors CTCF and cohesin, in contrast to super-enhancers, forming clusters of CTCF and cohesin binding regions and defining homotypic clusters of transcription regulator binding regions (HCTs). Finally, we show the clinical utility of CREAM to identify COREs across chromatin accessibility profiles to stratify more than 400 tumor samples according to their cancer type and to delineate cancer type-specific active biological pathways. Collectively, our results support the utility of CREAM to delineate COREs underlying, with greater accuracy than individual CREs or super-enhancers, the cell-type-specific biological underpinning across a wide range of normal and cancer cell types.
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http://dx.doi.org/10.1101/gr.248658.119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6771399PMC
October 2019

Consensus on Molecular Subtypes of High-Grade Serous Ovarian Carcinoma.

Clin Cancer Res 2018 10 3;24(20):5037-5047. Epub 2018 Jul 3.

City University of New York School of Public Health, New York, New York.

The majority of ovarian carcinomas are of high-grade serous histology, which is associated with poor prognosis. Surgery and chemotherapy are the mainstay of treatment, and molecular characterization is necessary to lead the way to targeted therapeutic options. To this end, various computational methods for gene expression-based subtyping of high-grade serous ovarian carcinoma (HGSOC) have been proposed, but their overlap and robustness remain unknown. We assess three major subtype classifiers by meta-analysis of publicly available expression data, and assess statistical criteria of subtype robustness and classifier concordance. We develop a consensus classifier that represents the subtype classifications of tumors based on the consensus of multiple methods, and outputs a confidence score. Using our compendium of expression data, we examine the possibility that a subset of tumors is unclassifiable based on currently proposed subtypes. HGSOC subtyping classifiers exhibit moderate pairwise concordance across our data compendium (58.9%-70.9%; < 10) and are associated with overall survival in a meta-analysis across datasets ( < 10). Current subtypes do not meet statistical criteria for robustness to reclustering across multiple datasets (prediction strength < 0.6). A new subtype classifier is trained on concordantly classified samples to yield a consensus classification of patient tumors that correlates with patient age, survival, tumor purity, and lymphocyte infiltration. A new consensus ovarian subtype classifier represents the consensus of methods and demonstrates the importance of classification approaches for cancer that do not require all tumors to be assigned to a distinct subtype. .
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http://dx.doi.org/10.1158/1078-0432.CCR-18-0784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207081PMC
October 2018

PharmacoDB: an integrative database for mining in vitro anticancer drug screening studies.

Nucleic Acids Res 2018 01;46(D1):D994-D1002

Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.

Recent cancer pharmacogenomic studies profiled large panels of cell lines against hundreds of approved drugs and experimental chemical compounds. The overarching goal of these screens is to measure sensitivity of cell lines to chemical perturbations, correlate these measures to genomic features, and thereby develop novel predictors of drug response. However, leveraging these valuable data is challenging due to the lack of standards for annotating cell lines and chemical compounds, and quantifying drug response. Moreover, it has been recently shown that the complexity and complementarity of the experimental protocols used in the field result in high levels of technical and biological variation in the in vitro pharmacological profiles. There is therefore a need for new tools to facilitate rigorous comparison and integrative analysis of large-scale drug screening datasets. To address this issue, we have developed PharmacoDB (pharmacodb.pmgenomics.ca), a database integrating the largest cancer pharmacogenomic studies published to date. Here, we describe how the curation of cell line and chemical compound identifiers maximizes the overlap between datasets and how users can leverage such data to compare and extract robust drug phenotypes. PharmacoDB provides a unique resource to mine a compendium of curated cancer pharmacogenomic datasets that are otherwise disparate and difficult to integrate.
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http://dx.doi.org/10.1093/nar/gkx911DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5753377PMC
January 2018

JSBML 1.0: providing a smorgasbord of options to encode systems biology models.

Bioinformatics 2015 Oct 16;31(20):3383-6. Epub 2015 Jun 16.

University of California, San Diego, La Jolla, CA, USA, Center for Bioinformatics Tuebingen (ZBIT), University of Tuebingen, Tübingen, Germany.

Unlabelled: JSBML, the official pure Java programming library for the Systems Biology Markup Language (SBML) format, has evolved with the advent of different modeling formalisms in systems biology and their ability to be exchanged and represented via extensions of SBML. JSBML has matured into a major, active open-source project with contributions from a growing, international team of developers who not only maintain compatibility with SBML, but also drive steady improvements to the Java interface and promote ease-of-use with end users.

Availability And Implementation: Source code, binaries and documentation for JSBML can be freely obtained under the terms of the LGPL 2.1 from the website http://sbml.org/Software/JSBML. More information about JSBML can be found in the user guide at http://sbml.org/Software/JSBML/docs/.

Contact: jsbml-development@googlegroups.com or andraeger@eng.ucsd.edu

Supplementary Information: Supplementary data are available at Bioinformatics online.
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http://dx.doi.org/10.1093/bioinformatics/btv341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4595895PMC
October 2015

Social Network: a Cytoscape app for visualizing co-authorship networks.

F1000Res 2015 5;4:481. Epub 2015 Aug 5.

The Donnelly Centre, University of Toronto, Toronto, ON, M5S 1A8, Canada.

Networks that represent connections between individuals can be valuable analytic tools. The Social Network Cytoscape app is capable of creating a visual summary of connected individuals automatically. It does this by representing relationships as networks where each node denotes an individual and an edge linking two individuals represents a connection. The app focuses on creating visual summaries of individuals connected by co-authorship links in academia, created from bibliographic databases like PubMed, Scopus and InCites. The resulting co-authorship networks can be visualized and analyzed to better understand collaborative research networks or to communicate the extent of collaboration and publication productivity among a group of researchers, like in a grant application or departmental review report. It can also be useful as a research tool to identify important research topics, researchers and papers in a subject area.
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http://dx.doi.org/10.12688/f1000research.6804.3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760270PMC
March 2016