A putative role for ALDH inhibitors and chemoprevention of BRCA-mutation-driven tumors.

Aldehyde dehydrogenase (ALDH) enzymatic activity is a marker of cancer-initiating cells (CIC) in many tumor types. Our group and others have found that ALDH1A family inhibitors (ALDHi) can preferentially induce death of ovarian CIC in established ovarian cancer. We sought to determine if ALDHi, by targeting CIC at the time of tumor initiation, could function as a chemopreventive for ovarian cancer. As BRCA1/2 mutation carriers represent a population who could benefit from an ovarian cancer chemopreventive, we focused on BRCA mutation-associated tumor cell lines and murine tumor models. We found that, compared to BRCA wild-type cells, BRCA mutant ovarian cancer cells are more sensitive to the ALDHi673A. Similarly, while 673A treatment of wild-type fallopian tube epithelial (FTE) cells is non-toxic, 673A induces death in FTE cells with BRCA1 knockdown. Using a murine fallopian tube organoid model of ovarian carcinogenesis, we show that 673A reduced organoid complexity and significantly reduce colony formation of BRCA-mutant cells. Organoids that persisted after 673A treatment were predominantly BRCA1wt, but NF1 mutant, suggesting a resistance mechanism. Finally, using the BPRN (Brca1, Trp53, Rb1, Nf1 inactivated) mouse model of tubo-ovarian cancer, we evaluated the impact of intermittent 673A therapy on carcinogenesis. 673A treatment resulted in a significant reduction in serous tubal intraepithelial carcinoma (STIC) lesions and carcinomas. Collectively, the findings suggest that ALDHi, such as 673A, could serve as chemopreventive agents for BRCA1/2 mutation carriers.