Abstract B15: BRCA haploinsufficiency promotes gluconeogenesis in fallopian tube epithelial cells
Authors: Paudel Iru , Sowamber Ramlogan , Dodds Leah , Sanchez Alex , Huang Marilyn , Schlumbrecht Matthew , Slomovitz Brian , George Sophia 
Published: September 2020

Introduction: High-grade serous ovarian cancer (HGSC) is one of the deadliest gynecologic malignancies due to presentation at advanced stages and the development of chemotherapy resistance. The recent discovery that HGSC arises from fallopian tube epithelia (FTE) and the analysis results obtained from TCGA study are helping in understanding the genes involved in the progression of the disease. HGSC is genetically unstable due to the loss of function mutations in BRCA1, BRCA2, PALB2, ATM, and RAD51 genes involved in DNA damage response. These genes also regulate cellular metabolism, antioxidant, and detoxification responses. Preliminary data show that phase II antioxidant enzymes are significantly reduced in HGSC and there is an increase in reactive oxygen species (ROS) in cells harboring p53 and BRCA1 mutations in precursor lesions of FTE and HGSC. We also observed differential mRNA expression of PCK1 and PCK2, GLUT1 genes involved in gluconeogenesis and glycolysis. Mitochondria are one of the major organelles for the production of ROS, and it is a well-known fact that metabolism is drastically changed in cancer cells compared to normal cells. Our aim was to determine the metabolic and fuel dependency in preneoplastic transformed cells, characterize the mitochondrial phenotype, and link these dependencies to transformation in FTE.

Methods: Fallopian tube specimens were obtained from the Biospecimen Shared Resources Core at SCCC. Patients undergoing risk reduction surgery were consent and FTE cells were obtained from BRCA and non-BRCA. Preneoplastic cell lines were then generated by hTERT, p53 mutation (R175H), and HPVE7. To mimic the genetic changes of in vivo HGSC, oncogenes CCNE1 and PIK3CA-H1047R were then overexpressed (OE) in these immortalized cell lines. Xenografts were generated from the transformed FTE cells lines. Agilent Seahorse assays were used to study the fuel dependency, oxidative phosphorylation, and glycolysis.

Results: FTE-BRCA1 and FTE-BRCA2 cells showed differences in both glycolytic and oxidative metabolism depending on the oncogenic type. The transformed cells had lower oxidative metabolism and there was also discrepancy in the dependency of metabolites utilized by these cell lines for energy. As seen by mRNA, FTE-BRCA cells had more PCK2 protein and were characterized by higher metabolic rates; these observations were augmented in the presence of PIK3CA-H1047R. However, these FTE preneoplastic and oncogene transformed cells showed no difference in their mitochondrial mass or membrane potential.

Conclusion: FTE-BRCA mutant cells utilize glycolysis or gluconeogenesis pathways to overcome metabolic stress depending on which oncogene is driving carcinogenesis. Further work is required to elucidate the mechanism of PCK2 and BRCA link in ovarian cancer carcinogenesis.

Citation Format: Iru Paudel, Ramlogan Sowamber, Leah Dodds, Alex Sanchez, Marilyn Huang, Matthew Schlumbrecht, Brian Slomovitz, Sophia George. BRCA haploinsufficiency promotes gluconeogenesis in fallopian tube epithelial cells [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B15.