Abstract 5148: Immune landscapes and interactions in human fallopian tubes and their implications for early high-grade serous ovarian cancers
Authors: Brand Josh , Harro Marcela , Abbasi Forough , Lin Xianzhi , Siedhoff Matthew , Andrew Li , Rimel Bobbie J. , Medeiros Fabiola , Lawrenson Kate , Dinh Huy Q. 
Published: June 2022

Abstract
The five-year survival rate of ovarian cancer (OC) dramatically rises from below 40% to 90% with patients who are diagnosed early (stage I), when the disease restricts to the ovary. Thus, the ultimate goals of our research are to learn how to detect ovarian cancer at its earliest stages of development and thereby improve patient survival and to learn how the immune microenvironment contributes to the development of OC. Achieving these goals requires us to better characterize the earliest steps in ovarian carcinogenesis. The human fallopian tube harbors the cell-of-origin for most high-grade serous 'ovarian' cancers (HGSOCs), but its cellular composition, particularly the immune component, is poorly characterized. Emerging evidence from several research groups using molecular sequencing technologies of fallopian tube epithelium strongly support this hypothesis. We recently described our use of single-cell transcriptome technology (scRNA-Seq) to profile the heterogeneity of non-malignant FT and define a novel transcriptional gene regulatory network of epithelial differentiation and tumorigenesis in the human FT. Here we present an in-depth characterization of the immune cell atlas for human fallopian tubes, which has not been reported. Our unpublished analyses of our FT dataset and the publicly available HGSOC scRNA-Seq dataset demonstrate a significant difference in the immune cell landscape. There are limited macrophages and a high abundance of monocytes in non-malignant FT and adjacent normal ovaries compared to those in HGSOC tumors. This finding leads us to hypothesize that the macrophage-to-monocyte ratio and their interactions with other immune cell types in human fallopian tubes create a permissive microenvironment allowing for the development of HGSOC and can provide a biomarker for early cancer detection. To test if those myeloid cells could be a marker for early HGSOC, we performed scRNA-seq on FT from women carrying mutant alleles of BRCA1 or BRCA2 who are at high risk of HGSOC. Intriguingly, the ratio of monocytes to macrophages in the FTs from half of these high-risk individuals is more like that found in HGSOC than in normal FT. Furthermore, computational analyses on myeloid cell types and their interactions with different epithelial cells, stromal fibroblast cells, and T and NK cells revealed the extended contribution of the non-epithelial microenvironment in FT, potentially driving early HGSOC development and progression. This cellular and molecular compendium of the human fallopian tube immune landscapes in cancer-free and cancer-high-risk women is expected to advance our understanding of the earliest stages of fallopian epithelial neoplasia.
Citation Format: Josh Brand, Marcela Harro, Forough Abbasi, Xianzhi Lin, Matthew Siedhoff, Li Andrew, Bobbie J. Rimel, Fabiola Medeiros, Kate Lawrenson, Huy Q. Dinh. Immune landscapes and interactions in human fallopian tubes and their implications for early high-grade serous ovarian cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5148.