Abstract 5123: Proteogenomic characterization reveals mitotic kinase and replication stress implicated in ovarian high-grade serous cancer

Abstract

Abstract High-grade serous cancer (HGSC), the most prevalent histotype of ovarian cancer, has the lowest survival rates and is the leading cause of gynecological cancer-related deaths in the developed world. HGSC is characterized by the presence of nearly universal TP53 mutations, diverse and widespread chromosomal instability, and a general shortage of targetable driving mutations. The major clinical needs in HGSC include the identification of alternative therapeutic targets and an improved understanding of the mechanisms driving chromosomal heterogeneity. We prospectively collected 83 new ovarian HGSC samples and 20 normal precursor tissue samples (Fallopian tube, FT) for deep characterization at the genomic, transcriptomic, proteomic, and phosphoproteomic levels. We were also able to obtain cytobrush samples of Fallopian tube epithelium and provide the first extensive comparison of HGSC and FT proteomes and phosphoproteomes that used surgical specimens rather than cell lines. The ability to compare tumor and normal precursor tissues provided new biological insights regarding the role of increased proliferation in promoting replication stress in a DNA repair-deficient background, potentially explaining the high degree of chromosomal instability associated with HGSC. Our collection protocols were specifically designed to minimize the effect of ischemia on protein phosphorylation, which has been identified as a significant confounding variable. Thus, we were able to identify novel signaling interactions that would have been lost in the background of ischemic stress, most notably the activation of CDK4 and CDK7. Widespread increases in protein phosphorylation and pathway activation in tumors compared to normal tissues, particularly in the proliferation-associated CDK/RB and AURKA pathways that are targetable by FDA-approved inhibitors, provide a rational basis for the use of these therapeutics in ovarian cancer. Phosphosite-specific analysis of CDKs and FANCD was consistent with an elevated response to replication stress, potentially induced by proliferative signals. Additionally, pathway-level observations from the retrospective TCGA cohort were conserved in the prospective cohort, including histone acetylation marks associated with homologous repair deficiency. In addition to confirming key features of HGSC from previous proteogenomic study, analysis of prospectively collected HGSC samples provided significant new insights stemming from direct comparisons to normal precursor tissues; deep phosphoproteomics revealed new insights regarding the potential role of proliferation-induced replication stress in promoting the characteristic chromosomal instability of HGSC and suggested novel therapeutic targets for use in precision medicine trials. Citation Format: Jason McDermott, Osama Arshad, Vladislav Petyuk, Yi Fu, Marina Gritsenko, Chia-Feng Tsai, Samuel Payne, Mathangi Thiagarajan, Christopher Kinsinger, Ana Robles, Emily Boja, Henry Rodriguez, Daniel Chan, Bing Zhang, Zhen Zhang, Li Ding, Richard Smith, Tao Liu, Karin Rodland. Proteogenomic characterization reveals mitotic kinase and replication stress implicated in ovarian high-grade serous cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5123.