Abstract 2155: BRCAness in HGSC cancer initiation
Authors: Sowamber Ramlogan , Paudel Iru , Sanchez Alex , Diaz Alexandra , Shaw Patricia , Schlumbrecht Matthew , George Sophia 
Published: July 2021

Introduction: The luteal phase of BRCA mutation carrier tissues has distinct profiles of differentially expressed genes compared to wild-type fimbria. High Grade Serous Ovarian Carcinoma (HGSOC) is one of the most lethal gynecological diseases and presents at late tumor stage. Studies focusing on the early events of the disease have implicated the fimbriated end of the fallopian tube as the high-risk zone for cancer development. In this study, we aim to identify BRCA transcriptomic signatures in the fimbria of patients with a BRCA mutation and compare the luteal and follicular phases to capture the effect of the extrinsic milieu in response to stressors.

Experimental Procedures: Laser capture microdissection (LCM) was performed on 68 formalin fixed paraffin embedded (FFPE) fallopian tube samples based on BRCA mutation status and ovulatory cycle: Normal-Follicular, Normal-Luteal, BRCA-Follicular, BRCA-Luteal. Nine HGSC samples were derived from patients with a mutation in BRCA1. Six-Twelve, 10um FFPE sections were cut and stained with hematoxylin prior to LCM. RNA was extracted using the Roche High Pure FFPE Micro Kit and samples and were processed using Illumina Tru-Seq Stranded Total RNA Kit with RiboGold ready and sequenced on the Illumina Hi-seq 2000 V3. Bioinformatic analysis performed on multiple comparisons highlighted differentially expressed genes. Gene Set Enrichment Analysis (GSEA) performed on subgroups highlighted pathways of interest for each comparison. Genes highly expressed or strongly suppressed were shortlisted for further analysis. Western blot analysis performed on wildtype patients (WT), BRCA1 mutation and BRCA2 mutation showed protein expression of selected genes.

Results: The fimbriae compared to ampullae have more stem-like features, have up-regulated antioxidant/xenobiotic genes, and have more inflammatory cells intercalated within the epithelia. The fimbria of FTE-BRCA have distinctly up-regulated genes involved in DDR (DNA damage response) which are exacerbated in the luteal phase of the ovulatory cycle. BRCA1/2 luteal versus follicular phases are involved in endoplasmic reticulum stress, migration, MAPKK. Whereas decreased differentially expressed genes are involved with G2/M checkpoint, DNA replication and ER-associated degradation pathway. Post-ovulatory phase of the ovarian cycle drives inflammation, differentiation and DNA damage-repair in FTE cells. Furthermore, GSEA analysis of the luteal and follicular phases showed positive enrichment of the inflammatory response pathway and negative enrichment of oxidative phosphorylation in the luteal phase.

Conclusions: Our results highlight distinct pathways related to repair and inflammation for the BRCA1 mutation carriers and luteal phase of the fimbria. These results are consistent with previous examination of the fallopian tube and provide insight into targetable genes associated with the development of HGSC.

Citation Format: Ramlogan Sowamber, Iru Paudel, Alex Sanchez, Alexandra Diaz, Patricia Shaw, Matthew Schlumbrecht, Sophia George. BRCAness in HGSC cancer initiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2155.