Lifestyle and reproductive factors and ovarian cancer risk by p53 and MAPK Expression

Abstract

Background: One model of ovarian cancer development model divides tumors into two types. Type I tumors are characterized by KRAS and BRAF mutations, which can activate mitogenactivated protein kinase (MAPK). Type II tumors are characterized by tubal precursor lesions with p53 mutations. We evaluated the association between lifestyle and reproductive factors and risk of ovarian cancer defined by p53 and MAPK expression. Methods: Epithelial ovarian cancer cases (n = 274) and controls (n = 1,907) were identified from the Nurses' Health Study and Nurses' Health Study II prospective cohorts, and the population- basedNewEngland Case-Control study. Reproductive and lifestyle exposures were assessed by questionnaire/interview. We performed immunohistochemical assays for p53 and MAPK expression. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using polytomous logistic regression. Results: Parity was associated with a decreased risk of p53 wildtype tumors (OR=0.31;95%CI, 0.18-0.55), but not p53-mutant tumors (OR = 0.92; 95% CI, 0.54-1.59)(Pheterogeneity > 0.01). Family history of breast or ovarian cancer was associated with risk of MAPK-negative (OR = 2.06; 95% CI, 1.39-3.06), but not MAPK-positive tumors (OR = 0.74; 95% CI, 0.43-1.27; Pheterogeneity> 0.01). In cross-classified analyses, family history of breast or ovarian cancer was most strongly associated with p53- mutant/MAPK-negative tumors (OR = 2.33; 95% CI, 1.44-3.75). Differences by MAPK expression were also observed for estrogen plus progesterone hormone therapy use (Pheterogeneity = 0.03). Conclusions: These findings provide evidence that parity, family history, and estrogen plus progesterone hormone therapy use may be differentially associated with tumor subtypes defined by p53 and MAPK expression. Impact: In future studies, other immunohistochemical markers or gene expression profiles that more clearly define these subtypes should be considered.