Mutant p53 disrupts antioxidant defense in fallopian tube epithelium via GSTAs suppression: A pathway to serous tubal carcinogenesis.

High grade serous ovarian cancer (HGSOC) is the most common and aggressive type of epithelial ovarian cancer. The fimbria of the fallopian tube is the likely site of origin based on the presence of distinct precancerous lesions with TP53 signatures known clinically as serous tubal intraepithelial carcinoma (STICs) detected in this region in individuals at genetically high risk or with HGSOC. Previously we identified that matched fallopian tube epithelia (FTE) from fimbria and ampulla of normal fallopian tubes from premenopausal women exhibit differential expression of genes associated with antioxidant and inflammatory pathways. One gene, glutathione S-transferase 2 (GSTA2), showed both higher expression in the fimbria and in the follicular phase (pre-ovulation) compared to the ampulla, suggesting that GSTA2 expression may regulate reactive oxygen homeostasis in these cells in response to ovulation-related stress. Here, to understand how preneoplastic genomic alterations influence regulation of oxidative stress, FTE cells were isolated from healthy tissue and introduced with p53 mutations, from which expression and function of GSTA2 and other antioxidant enzymes were investigated. Mutant p53 downregulated the expression of GSTA2 and subsequently increased DNA damage. The combination of p53 mutation and dysregulated oxidative response likely promotes the genomic instability that initially drives the transformation to high grade serous ovarian carcinoma.