Abstract 5479: Spatially resolved molecular features in the tumor-immune microenvironment of germline BRCA1/2 mutated versus BRCA wild type high grade serous ovarian cancers

Abstract High-grade serous ovarian cancer (HGSC) is the most common and aggressive subtype of epithelial ovarian cancer. Importantly, germline mutations in BRCA1/2 give rise to HGSC. Because most HGSC are diagnosed at stage III/IV, outcomes are poor and more effective therapies are needed. Although immune checkpoint inhibitors show promise for a number of cancer types, efficacy has been variable in HGSC. To help provide new clues to the molecular features of HGSC, we set out to elucidate the tumor microenvironment of HGSC using spatial transcriptomics approaches. Specifically, we applied 10x Genomics Visium Spatial Transcriptomics (ST) technology to 48 samples representing primary HGSC tumors from 24 patients, including 15 BRCA1/2 mutated cases and 9 BRCA non-mutated cases. In addition to individual sample analysis, we normalized data from 64, 784 total features across all sections and performed an integrated cluster analysis to get an overall picture of the cellular architecture of HGSC, but to also directly investigate differences in the tumor microenvironment based on BRCA mutation status. The resulting 17 integrated clusters were subjected to molecular annotation using GSEA, ESTIMATE, and CIBERSORTx, which revealed feature clusters representing important cell types defined by marker genes. Analysis of the entire dataset identified a primary tumor cluster defined by the expression of known ovarian cancer genes including WFDC2 and “don’t eat me” marker genes CD24 and CD47. However, the predominant tumor cell population in BRCA mutated cases was marked by the expression of MUC1, EPCAM, CLDN3, and CD24, while BRCA non-mutated tumor cell cluster was marked by EFNA1, ID1, LSR, and CD9. Importantly, both groups revealed the presence of a specialized monocyte derived macrophage cluster defined by the expression of LYZ and genes involved in cholesterol metabolism including APOE and APOC1. These lipid-associated macrophages are M2 polarized and shown to be associated with poor outcome. Additional analyses are underway to determine spatial dependencies of various tumor and immunological cell compartments. These data provide novel insights into the HGSC tumor microenvironment that may influence HGSC’s vulnerability to immunological therapies. Citation Format: Jing Qian, Lynda D. Roman, Rania Bassiouni, Seeta Rajpara, Monica Neuman, Varun Khetan, David W. Craig, Joseph W. Carlson, John D. Carpten. Spatially resolved molecular features in the tumor-immune microenvironment of germline BRCA1/2 mutated versus BRCA wild type high grade serous ovarian cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5479.