NFkB signaling and ISGylation associated with BRCA1-mutated fallopian tube epithelium

Germline BRCA1 or BRCA2 mutations (mtBRCA1 and mtBRCA2) dramatically increase risk for high-grade serous ovarian cancer (HGSOC), the most commonly diagnosed histotype. Other risk factors for this cancer, which originates primarily in the distal fallopian tube epithelium (FTE), implicate ovulation. To test whether mtBRCA1 or mtBRCA2 FTE cells respond differently to peri-ovulatory follicular fluid (FF) exposure than control patient FTE, gene expression profiles from primary FTE cultures were compared at baseline, 24h after FF exposure, and 24h after FF replacement with culture medium. Hierarchical clustering revealed both FF exposure and BRCA mutation status affect gene expression, with BRCA1 mutation having the greatest impact. Analysis revealed increased NFB and EGFR signaling at baseline, with increased interferon signaling after recovery from FF exposure in mtBRCA1 samples. Inhibition of EGFR signaling and ISGylation by increased BRCA1 expression was verified in an immortalized FTE cell line, OE-E6/E7, stably transfected with BRCA1. Suppression of ISG15 and ISGylated protein levels by BRCA1 expression was found to be mediated by decreased NFB signaling and was transiently suppressed by FF exposure. This study demonstrates increased NFB signaling associated with decreased BRCA1 expression resulting in increased ISG15 and ISGylation following FF exposure, which could represent potential targets for chemoprevention.

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Hollingsworth J, Lau A, Tone A, Kollara A, Allen L, Colgan TJ, Dube V, Rosen B, Murphy KJ, Greenblatt EM, Feigenberg T, Virtanen C, Brown TJ