Abstract A21: Enhancing chemotherapeutic responses in CNS malignancy through suppression of hyperactive DNA damage repair pathways
Conclusion: I have identified unique DNA repair enzymes, which may mediate specific differential chemo-radioresistant phenotypes in MB and MG. An expanded analysis is currently underway to further differentiate DNA repair mechanisms and therapeutic responses between these two brain tumor types. I hope to translate these findings into pre-clinical models whereby my data may lead to identifying next-generation brain cancer treatments with improved patient survival and quality-of-life.Citation Format: Marina Mostafizar, Sachin Katyal. Enhancing chemotherapeutic responses in CNS malignancy through suppression of hyperactive DN...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Mostafizar, M., Katyal, S. Tags: Synthetic Lethality and Viability: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR20: A 53BP1 integrates DNA repair and p53-dependent cell fate decisions via distinct mechanisms
The tumor suppressor protein 53BP1 was first identified as a p53-interacting protein over two decades ago, however its direct contribution to p53-dependent cellular activities has remained enigmatic. Having reinvestigated the link between 53BP1 and p53, we now show 53BP1 plays an important role in directly stimulating genome-wide p53-dependent gene transactivation and repression events in response to ionizing radiation (IR) and synthetic p53 activation. We have also fine-mapped the domains in 53BP1 that modulate p53 activity and reveal it requires both auto-oligomerization and its tandem-BRCT domain-mediated bivalent inter...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Cuella-Martin, R., Oliveira, C., Lockstone, H. E., Snellenberg, S., Grolmusova, N., Chapman, J. R. Tags: DNA Damage Signaling: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA20: Phosphorylation of BRCA1 by CHK2 mediates resection activity and recruitment of BRCA2
There is genetic evidence that Chk2, BRCA1 and BRCA2 are functioning in the same pathway of DNA repair, but the links between the proteins are poorly understood. We have previously shown that BRCA1's regulation of homologous recombination (HR) is dependent on Chk2-mediated phosphorylation of BRCA1 at serine 988 (BRCA1-S988). We also found that BRCA1 regulates BRCA2 recruitment in response to DNA damage, which is also dependent on the phosphorylation of BRCA1 at Serine-988. Furthermore, in HCT116/Chk2-/- cells and in MCF7 cells with depleted Chk2, the same effects on HR and BRCA2 recruitment has been found as found in cells...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Powell, S. N. Tags: DNA Damage Signaling: Oral Presentations - Invited Abstracts Source Type: research
Abstract B20: Schedule-dependent activation of DNA helicases by Checkpoint Kinase 1 inhibition following dNTP depletion causes CDK2-independent replication catastrophe
DNA damaging agents are standard of care therapies for many cancers, but frequently produce poor outcomes in many patients. Using DNA damage checkpoint inhibitors to sensitize cancer cells to standard therapies is a rapidly emerging strategy. Understanding the mechanism behind sensitization will help clinicians develop rational combinations and schedules to improve cancer care. Additionally, understanding how defects in the DNA damage response affect treatment outcomes may help identify which patients will respond to treatment. We have previously demonstrated that inhibition of Checkpoint Kinase 1 (Chk1) with MK8776 sensit...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Warren, N. J., Eastman, A. R. Tags: Therapies Targeting Checkpoints and Mismatch Repair: Poster Presentations - Proffered Abstracts Source Type: research
Abstract A20: Synthetic lethality induced by pharmacological inhibition of ATM and PARP1
DNA double-stranded breaks (DSBs) are highly deleterious and need to be repaired for maintaining genomic stability and viability. Cells resolve DSBs via non-homologous end-joining or homologous recombination repair (HRR). The simultaneous downregulation of both repair mechanisms induces synthetic lethality. Accordingly, PARP1 inhibitors (PARPi) are being used to target cancers with defective HRR such as cancers with BRCA1/2 mutations. Similar to BRCA1/2, ATM is involved in HRR; and ATM deficiency enhances sensitivity towards PARPi. But unlike BRCA1/2, ATM can be targeted using various small-molecule inhibitors (ATMi) in ca...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Mak, J. P. Y., Poon, R. Y. C. Tags: Synthetic Lethality and Viability: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR19: Targeting DNA double-strand break repair to potentiate radio- and chemo-therapy of glioblastoma
Glioblastomas (GBMs) are lethal brain tumors which are treated with ionizing radiation (IR) in combination with the DNA alkylating agent temozolomide (TMZ). Unfortunately, not all GBMs respond to therapy, and most of them quickly acquire resistance to TMZ and recur. In order to better understand the molecular basis for therapy-driven TMZ resistance, mice bearing orthotopic GBM xenografts were subjected to protracted TMZ treatment, and cell lines were generated from the primary (untreated) and recurrent (TMZ-treated) tumors. We found that cell lines derived from recurrent tumors were more resistant to TMZ in vitro compared ...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Mukherjee, B., Alcazar, C. G. d., Todorova, P., Burma, S. Tags: Therapies Targeting Checkpoints and Mismatch Repair: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA19: PARP trapping and Schlafen 11
Poly(ADP-ribose) polymerase inhibitors (PARPIs) kill cancer cells by trapping PARP1 and PARP2. Talazoparib, the most potent PARP inhibitor (PARPI), exhibits remarkable selectivity among the NCI-60 cancer cell lines beyond BRCA inactivation. Our genomic analyses reveal high correlation between response to talazoparib and Schlafen 11 (SLFN11) expression. Causality was established in four isogenic SLFN11-positive and -negative cell lines and extended to olaparib. Response to the talazoparib-temozolomide combination was also driven by SLFN11 and validated in 36 small cell lung cancer cell lines, and in xenograft models. Resist...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Pommier, Y., Murai, J. Tags: DNA Damage Signaling: Oral Presentations - Invited Abstracts Source Type: research
Abstract B19: The ATR inhibitor, AZD6738, synergizes with other DNA damage response inhibitors and genotoxic drugs in pancreatic ductal adenocarcinoma cell lines: Opportunities for new therapeutic combinations
Mutations in oncogenes, tumor suppressor and DNA damage response (DDR) mediator genes drive or permit malignant transformation but also increase endogenous replication stress. The serine/threonine kinase ATR plays a critical role in safeguarding genome integrity from such replication stress and several studies have demonstrated the increased reliance of cancer cells on ATR function. We investigated the therapeutic opportunities for the ATR inhibitor, AZD6738, in combination with DNA damaging or DDR-targeted agents, in the context of pancreatic ductal adenocarcinoma (PDAC).We evaluated four DNA-damaging agents (gemcitabine,...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Wallez, Y., Koh, S.-B., Bhogadi, V. S. V., Lau, A., Richards, F. M., Jodrell, D. I. Tags: Therapies Targeting Checkpoints and Mismatch Repair: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR18: Somatic ERCC2 mutations, nucleotide excision repair (NER) function, and cisplatin response in muscle-invasive bladder cancer (MIBC)
ERCC2 is a core member of the nucleotide excision repair (NER) pathway, a highly conserved and remarkably versatile DNA repair pathway responsible for repairing intrastrand DNA adducts created by genotoxic agents such as UV irradiation and platinum-based chemotherapies. Recent large-scale genomic efforts have shown that somatic ERCC2 missense mutations are present in approximately 20% of all primary muscle-invasive bladder cancers (MIBC). We previously showed that ERCC2 mutations are associated with treatment response and overall survival in MIBC patients treated with cisplatin-based chemotherapy. Initial functional studie...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Mouw, K., Lazaro, J.-B., Damish, A., Reznichenko, E., Frazier, Z., Liu, D., Kim, J., Polak, P., Garraway, L., Getz, G., Rosenberg, J., Allen, E. V., D'Andrea, A. Tags: DNA Repair Gene Mutations in Cancer Genomes: Oral Presentations - Proffered Abstracts Source Type: research
Abstract PR17: The transcriptional repressor Slug promotes the DNA damage response
The transcriptional repressor Slug/SNAI2 orchestrates epigenetic programs indispensable for tissue self-renewal and tumorigenesis. Although Slug-deficient animals are highly sensitive to lethal irradiation, the direct biological relationship between Slug and the DNA damage response remains largely unexplored. Here we report that Slug interacts with DNA repair proteins, including FANCI, BCCIP and PARP1, in a mass spectrometry screen for Slug binding partners. In response to double-strand breaks (DSBs) induced by irradiation, Slug-deficient cells exhibited a marked delay in the resolution of H2ax foci. Furthermore, we showed...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Zhou, W., Ouyang, J., Huber, K., Kuperwasser, C. Tags: DNA Damage Signaling: Oral Presentations - Proffered Abstracts Source Type: research
Abstract IA17: Non-canonical aspects of ATM and p53 signaling pathways
The ATM protein kinase and p53 protein are both central mediators of many aspects of DNA damage and cellular stress signaling. While there is a clear, direct relationship between ATM and p53, ATM has numerous substrates in addition to p53 and, conversely, p53 can be activated by selected stresses without ATM. We have identified novel aspects of stress response signaling independently involving either ATM or p53. Though ATM plays a central role in mediating cellular responses to DNA breakage, some of the clinical abnormalities in the cancer-prone disorder, Ataxia-telangiectasia (A-T), are difficult to attribute directly to ...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Kastan, M. B., Scarbrough, P., Chen, J., Brown, A., Crutchley, J., Fleenor, D. Tags: DNA Damage Signaling: Oral Presentations - Invited Abstracts Source Type: research
Abstract B17: Development of novel, potent orally available Wee1 inhibitors with robust antitumor efficacy in vivo
In this study, we describe the development of novel and highly potent small molecule inhibitors of Wee1 emanating from 2 distinct chemical series (ADC730, ADC999). These inhibitors exhibit single digit nM IC50 values versus the enzyme and good selectivity profiles against the kinome. In cells, target engagement was demonstrated through the inhibition of both CDC2- and CDK2-dependent Wee1 phosphorylation. In line with the mechanism of action, gH2AX and apoptosis induction was also observed in a dose-dependent manner. Further profiling in panels of cell lines indicated strong anti-proliferative activity both in combination w...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Gavory, G., O'Dowd, C., Rozycka, E., Boyd, C., Gorges, B., McLean, E., Rountree, S., Sheperd, S., Burton, S., McFarland, M., Janssen, D., Treder, A., Wilkinson, A., Burkamp, F., Harrison, T. Tags: Therapies Targeting Checkpoints and Mismatch Repair: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR16: Normal and neoplastic tissues with partial Hus1 impairment show hypersensitivity to cisplatin in vivo
The DNA damage response (DDR) factor HUS1 is vital for proper functioning of the ATR checkpoint pathway. Following DNA damage, HUS1 forms a heterotrimeric complex with RAD9 and RAD1 and works with other checkpoint and scaffold proteins to activate ATR and CHK1 kinases. HUS1 also has separate functions that promote DNA repair. Due to its essential nature and diverse roles in genome maintenance, we hypothesized that HUS1 would be critical in the response of normal and neoplastic tissues to the DNA-damaging chemotherapeutic, cisplatin. Cisplatin is a widely used chemotherapeutic that damages DNA via platinated adducts, which ...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Noe, T. E., Siderides, C. C., Gallastegui, A., Cheung, J. M., Abratte, T., Hume, K. R. Tags: DNA Damage Signaling: Oral Presentations - Proffered Abstracts Source Type: research
Abstract A16: Potent and selective ATR inhibitors for the treatment of homologous-recombination deficient and PARPi-resistant cancers
We report the generation of a novel class of highly potent and specific ATR inhibitors (ATRN series) that exhibit low nanomolar activity in cultured cells (IC50 = 2-8 nM) and do not detectably inhibit ATM, DNA-PK or mTOR (IC50 > 10 µM). In side-by-side comparisons, both the potency and selectivity of the ATRN series is superior to previously reported ATR inhibitors (VE821, VE822, AZD20, AZD6738, ETP-46464). In addition, the ATRN series has sufficient bioavailability and stability for in vivo application. Our lead compound (ATRN-119) slows progression of human BRCA2-deficient PDAC (CAPAN1) and RAS oncogene-driven p...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Butler, L. R., Ragland, R. L., Breslin, H. J., George, E., Gill, T., Scheiwer, M., Gordon, N., Knudsen, K., Simpkins, F., Gilad, O., Brown, E. J. Tags: Synthetic Lethality and Viability: Poster Presentations - Proffered Abstracts Source Type: research
Abstract PR15: Cas9/RNA-based forward genetic screenings in mouse embryonic stem cells uncovered the role of genes mediating resistance to ATR inhibitors
Mouse embryonic stem cells (mESCs) represent an excellent platform to study processes of developmental biology, model disease in vitro and in vivo or perform drug discoveries. In the last few years, the development of precise genome engineering tools based on the RNA-guided Cas9 nuclease from the type II prokaryotic clustered regularly interspaced short palindromic repeats (CRISPR) adaptive immune system, has enabled efficient and easy to engineer targeted genome modifications in mammalian cells. Using this technology, we generated a highly controlled doxycycline-inducible Cas9 mESC line, which harbor one single copy of Ca...
Source: Molecular Cancer Research - April 2, 2017 Category: Cancer & Oncology Authors: Ruiz, S., Mayor-Ruiz, C., Lafarga, V., Murga, M., Vega, M., Ortega, S., Fernandez-Capetillo, O. Tags: Replication Stress: Oral Presentations - Proffered Abstracts Source Type: research
