Abstract IA09: Replication fork stability confers chemoresistance in BRCA-deficient cells
Brca1- and Brca2-deficient cells have reduced capacity to repair DNA double strand breaks (DSBs) by homologous recombination (HR) and consequently are hypersensitive to DNA damaging agents including cisplatin and poly(ADP-ribose) polymerase (PARP) inhibitors. Here we show that loss of the MLL3/4 complex protein PTIP protects Brca1/2-deficient cells from DNA damage and rescues the lethality of Brca2-deficient embryonic stem cells. However, PTIP deficiency does not restore HR activity at DSBs. Instead, its absence inhibits the recruitment of the MRE11 nuclease to stalled replication forks, which in turn, protects nascent DNA...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Chaudhuri, A. R., Callen, E., Ding, X., Gogola, E., Duarte, A. A., Lee, J.-E., Wong, N., Lafarga, V., Calvo, J. A., Panzarino, N. J., John, S., Day, A., Crespo, A. V., Shen, B., Starnes, L. M., Ruiter, J. R. d., Daniel, J. A., Konstantinopoulos, P. A., Co Tags: Synthetic Lethality and Viability: Oral Presentations - Invited Abstracts Source Type: research
Abstract B09: DNA damage inducible phosphorylation of ATR at threonine 1989 and quantitative analysis of the effect of ATR inhibition on DNA damage signaling using PTMScan
DNA repair pathways and checkpoint control are crucial in the maintenance of genome integrity. Agents that cause DNA damage, and agents that perturb DNA repair pathways, have been used successfully in the treatment of human cancer.The PI3K-like protein kinases ATR (ATM and Rad3-related) and ATM (ataxia telangiectasia mutated) are critical regulators of the DNA damage response (DDR), signaling to downstream effector molecules that in turn regulate cellular responses such as DNA repair, cell cycle arrest, and cell death.ATM is activated in response to DNA damage in part via autophosphorylation at serine 1981. ATR was long th...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Roberts, H. J., Stokes, M. P., Jia, X., Lee, K. A., Keezer, S. M. Tags: DNA Damage Signaling: Poster Presentations - Proffered Abstracts Source Type: research
Abstract IA08: Synthetic viability due to BRCA2 and PARP1 loss
It is very well established that BRCA1 and BRCA2 deficient cells are hypersensitive to PARP inhibitors (PARPi) due to synthetic lethality. Because Parp1 parylates proteins involved in a wide range of biological processes, we hypothesized that inhibiting PARP activity may have detrimental effect on cells that are HR proficient and do not undergo synthetic lethality. We have demonstrated that although Brca2 null ES cells are not viable, they can survive after ES cells expressing a conditional allele of Brca2 are treated with olaparib prior to Cre-mediated deletion of the conditional allele. We also found that while Parp1 los...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Sharan, S. K. Tags: Synthetic Lethality and Viability: Oral Presentations - Invited Abstracts Source Type: research
Abstract A08: PARP1-mediated E2F1 regulation of DNA repair capacity
PARP1 holds two major functions on chromatin, DNA damage repair and transcriptional regulation, both of which are relevant in the context of cancer. Notably, PARP1 has been found to be a key modulator of androgen receptor (AR) function and AR-dependent phenotypes, which is a driving factor in prostate cancer (PCa) biology and therapeutic management. Recent studies indicate an unanticipated prevalence of DNA repair alterations in advanced PCa and showed that PARP1 inhibitors (PARPi) can effectively manage of a subset of these tumors. Despite the functions of PARP1 in DNA repair having been exploited as a therapeutic target ...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Schiewer, M. J., Mandigo, A. C., Gordon, N., Han, S., Zhao, S., Evans, J., Parsons, T., Birbe, R., McCue, P., Visakorpi, T., Raj, G., Rubin, M., Bono, J. d., Lallas, C., Trabulsi, E., Gomella, L. G., Dicker, A. P., Kelly, W. K., Feng, F. Y., Knudsen, K. E Tags: Homologous Recombination Defects: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR07: Identifying factors mediating response and resistance to chemotherapy through a chemical-genetic interaction map
Nearly every cancer patient, especially those with highly lethal and aggressive tumor types, is treated with cytotoxic chemotherapy. Currently, the selection of chemotherapy is based on average responses over a large number of patients. This belies our understanding of DNA repair that has demonstrated that the inability of a tumor cell to properly repair particular types of DNA damage has a dramatic influence on cell survival. Here, we report the generation of a quantitative chemical-genetic interaction map to chart the influence of knockdown of 625 genes on sensitivity to 30 FDA approved chemotherapeutic agents in breast ...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Hu, H.-M., Bandyopadhyay, S. Tags: Synthetic Lethality and Viability: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA07: Genetic determinants of tumor development, therapy response and resistance in mouse models of BRCA-deficient breast cancer
Heterozygous germline mutations in BRCA1 or BRCA2 strongly predispose to development of breast and ovarian cancer (as well as other cancer types) via loss of the remaining wildtype allele. BRCA1/2-deficient cancers are defective in DNA double-strand break (DSB) repair via homologous recombination (HR) and therefore hypersensitive to DNA-damaging agents, including platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors. However, these treatments do not result in tumor eradication and eventually resistance develops. To maximize therapeutic efficacy of these drugs and achieve durable remissions, it is important to un...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Jonkers, J. Tags: Synthetic Lethality and Viability: Oral Presentations - Invited Abstracts Source Type: research
Abstract B07: Learning from human tumors: Modeling of Mre11 complex patient mutations in yeast
The Mre11 complex plays a central role in the eukaryotic DNA damage response (DDR) in which it acts as a sensor of DNA double strand breaks (DSBs), and thereby governs DNA damage signaling as well as DSB repair. The complex is comprised of Mre11, Rad50, and Nbs1 (or Xrs2 in budding yeast), with dimers of Rad50 and Mre11 forming its core and a Nbs1/Xrs2 protomer binding to each Mre11. The Mre11 complex globular domain harbors all enzymatic and DNA binding functions of the Mre11 complex and is a very dynamic domain regulated by conformational changes induced by Rad50 ATP binding and hydrolysis cycles. It was suggested that t...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Hohl, M., Inagaki, A., Petrini, J. H. J. Tags: DNA Damage Signaling: Poster Presentations - Proffered Abstracts Source Type: research
Abstract A07: The RAD51 paralog complex SWS1-SWSAP1 is critical for homologous recombination in the mouse
Homologous recombination (HR), also termed homology-directed repair, is a major pathway for the repair of DNA double-strand breaks (DSBs) generated by DNA damaging agents, replication fork collapse and during meiosis. Failure to repair DSBs correctly causes genomic instability, leading to mutagenesis, and developmental defects. Moreover, defects in HR impact the response to many therapeutics. Components of the HR machinery include BRCA2 and five RAD51 paralogs, which are critical for RAD51 assembly onto single-stranded DNA, an important intermediate for homologous strand invasion. Disruption of these HR genes in mice resul...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Prakash, R., Abreu, C. M., Keeney, S., Jasin, M. Tags: Homologous Recombination Defects: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR06: Targeted chemotherapy for Homologous Repair Defects (HRD) in molecularly profiled cancer patients
Precision Medicine Tumor Boards (PMTB) are now established at many academic institutions and provide a forum for multidisciplinary teams to discuss tumor profiling results to aid treatment choices for cancer patients. PMTBs typically focus on kinase mutations and well defined translocations, mostly because of limited gene panels explored. Established treatments exist for some of these genetic aberrations and multiple clinical trials have been initiated for specific kinase-targeted investigational drugs in development.The Yale 409 Gene Panel (Ion Torrent; AmpliSeq Comprehensive Cancer Panel) includes a large set of Homologo...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Eder, J. P., McLaughlin, J. F., Sklar, J., Walther, Z., Finberg, K., Minnella, A., Juergensmeier, J. M. Tags: Other Topics: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA06: The Fanconi anemia-BRCA pathway and cancer
The Fanconi anemia (FA)-BRCA pathway has emerged as an important pathway in cancer biology. FA is a rare genetic disease characterized by chromosomal instability, cancer-susceptibility and cellular sensitivity to interstrand DNA crosslink (ICL)-inducing agents. The FA proteins including breast/ovarian cancer susceptibility proteins, BRCA1(FANCS) and BRCA2(FANCD1), cooperate in a common pathway (the FA-BRCA pathway) required for cellular resistance to ICL-inducing agents. The main function of the pathway is to coordinate multiple DNA repair mechanisms during ICL repair, although many of the components of the pathway also pl...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Taniguchi, T. Tags: Homologous Recombination Defects: Oral Presentations - Invited Abstracts Source Type: research
Abstract A06: Regulation of homologous recombination by the SUMO ligase NSMCE2
Conclusions: The hyper-accumulation of RAD51 at stalled forks we observed in NSMCE2-deficient cells suggests the sumoylation of one or more substrates by NSMCE2 is required for the remodeling of stalled forks that normally leads to unloading of RAD51 at the fork, strand breakage, and repair by HR. We suggest that the RAD51 accumulation that is observed in a substantial fraction of cancers may not be sufficient to demonstrate that the cells are HR proficient. Based on our data, RPA staining combined with RAD51 may be able to distinguish HR-proficient and deficient cells.Citation Format: Kelvin W. Pond, Christelle DeRenty, M...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Pond, K. W., DeRenty, C., Yagle, M., Ellis, N. Tags: Homologous Recombination Defects: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR05: Distinct BRCA1- and BRCA2-specific functions at stalled replication forks: Clinical implications for differences between BRCA1 and BRCA2 mutation-driven cancer
BRCA1 and BRCA2 are tumor suppressor genes, and germ line mutations in these two genes increase the risk of breast cancer. Both BRCA1 and BRCA2 are required for stabilization and repair of stalled replication forks. Stalled forks, when not resolved, lead to mutations, or collapse into double strand breaks (DSBs). Both outcomes result in what is commonly referred to as replication stress (RS), which, when chronic, is a driving force behind cancer development. However, it is not clear what are the differences, if any, between BRCA1 and BRCA2 dependent stabilization and repair of stalled replication fork. Getting a better und...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Duan, H., Reed, R., Garber, J., Pathania, S. Tags: Replication Stress: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA05: Prospective identification of vulnerabilities to DNA repair inhibitors
The advent of CRISPR/Cas9 as a gene editing tool has enable the development of genome-scale libraries of single-guide RNAs that can be used to probe biological processes. CRISPR/Cas9 screens can be used to profile the essential gene complement of cancer cell lines, map genetic interactions and chart the response to drugs. During my presentation, I will present our efforts to map the genetic networks that govern the DNA damage response and will discuss our work aimed at mapping the genetic architecture of the response to PARP inhibitors. Our work revealed new types of genetic vulnerabilities to PARP inhibition and in partic...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Durocher, D. Tags: Homologous Recombination Defects: Oral Presentations - Invited Abstracts Source Type: research
Abstract A05: Improving outcome in homologous recombination competent epithelial ovarian cancer: Hyperthemia and surgeon's perspective
Conclusions: Personalized surgical and chemotherapeutic strategies may be developed for HR stratified EOCs. Primary surgery may be the preferred approach in HRC due to poor chemoresponse and resources should be optimized to achieve complete cytoreduction anticipating difficult resection. Intra-operative hyperthermic treatment and selective HR inhibitors (HSP90) may improve subsequent chemoresponse in HRC. Pre-clinical studies on patient tissues and after HIPEC procedures are proposed in ongoing studies to consolidate our hypothesis.1. Epithelial ovarian cancer: HR assay to stratify as HRD and HRC2. HRC: Primary surgery+ HI...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Mukhopadhyay, A., Abdulrahman, G., Davison, E., Matheson, E., Drew, Y., Curtin, N. Tags: Homologous Recombination Defects: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR04: Mechanism for PARPi resistance: Homologous recombination without BRCA1
Approximately 15-20% of all epithelial ovarian cancers harbor germline or somatic mutations in BRCA1/2. Despite PARP inhibitor induce synthetic lethality in non-cancerous mouse embryo fibroblast cells that harbor BRCA1/2 mutations, a substantial fraction of BRCA1/2-mutated tumors patients do not respond to PARPi treatment, and a large fraction of BRCA1/2-mutated tumors patients eventually develop resistance to PARPi suggest significant frequency of acquired mutation lead to PARPi resistance preventing complete cure.We use CRISPR based library screen identified ATMIN/DYNLL1 loss as strong candidate for PARPi and cisplatin r...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: He, Y. J., Meghani, K., Chowdhury, D. Tags: Synthetic Lethality and Viability: Oral Presentations - Proffered Abstracts Source Type: research
