RANKL and CSF-1 are elevated in periovulatory follicular fluid of BRCA1 mutation carriers and increase proinflammatory signaling in fallopian tube epithelial cells

Pathogenic germline mutations in BRCA1 predispose individuals to high-grade serous tubo-ovarian cancer (HGSTOC), which originates in the fallopian tube epithelium (FTE). Identified non-genetic risk factors are consistent with a potential role for repetitive exposure of FTE cells to follicular fluid during ovulation in the development of this disease. We previously showed that BRCA1 deficiency in non-malignant FTE cells associates with increased proinflammatory NFκB signaling, which could contribute to the development of HGSTOC. Additionally, exposure of BRCA1 mutated primary FTE cells to periovulatory follicular fluid resulted in further increased levels of proinflammatory gene transcripts as compared to cells isolated from control patients. In this study, we compared cytokine levels in periovulatory follicular fluid collected from BRCA1 mutation carriers to that of non-BRCA1 mutation carriers. Follicular fluid was collected from 59 patients diagnosed with breast cancer undergoing controlled ovarian stimulation and oocyte retrieval as part of their oncofertility treatment. Samples included 13 patients with confirmed BRCA1 mutations, 15 patients with mutations in other susceptibility genes and 31 patients confirmed as non-BRCA1 mutation carriers. Levels of 92 inflammatory proteins were measured using an antibody array with a proximity extension assay. Partial Least-Squares Discriminant Analysis indicated that samples from BRCA1 mutation carriers clustered separately from other samples, indicating BRCA1 mutation status influences cytokine levels in follicular fluid. RANKL and CSF-1 were among 7 proteins found to be statistically elevated in follicular fluid from BRCA1 mutation carriers. Treatment of an immortalized FTE cell line with RANKL and CSF-1 increased NFκB signaling and levels of proteins encoded by type I interferon-stimulated genes. These findings support further investigation exploring the potential of targeting RANKL and CSF-1 for HGSTOC prevention strategies in BRCA1 mutation carriers.