Promoter hypermethylation and expression of sprouty 2 in endometrial carcinoma

Abstract

Sprouty 2 is a key antagonist regulator of receptor tyrosine kinases, and downstream signaling pathways, like fibroblastic growth factor (FGF) and Ras-mitogen-activated protein kinase (RAS-MAPK). By controlling these pathways, sprouty 2 is involved in regulation of cell proliferation, differentiation, and angiogenesis. Alterations in fibroblastic growth factor receptor (FGFR) and members of the RAS-MAPK pathway are frequent in endometrial carcinoma. The expression of sprouty 2 has been found to be decreased in several types of human cancer, by mechanisms of promoter methylation. In the present study, we have assessed the expression of sprouty 2 in endometrial carcinoma, in correlation with sprouty 2 promoter methylation. Sprouty 2 immunohistochemical expression was assessed using 3 different tissue microarrays: one constructed from paraffin blocks of 80 samples of normal endometrium and 2 tissue microarrays containing samples of 157 endometrial carcinoma (1 tissue microarray constructed with 95 endometrial carcinomas previously studied for microsatellite instability and alterations in phosphatase and tensin homolog (PTEN), k-ras, and b-catenin, and 1 tissue microarray containing 62 endometrial carcinoma, which were also subjected to sprouty 2 promoter methylation analysis). The immunohistochemical expression of sprouty 2 was correlated with cellular proliferation (Ki67) and clinicopathologic data. Sprouty 2 promoter methylation was assessed by methylation-specific polymerase chain reaction, with DNA obtained from fresh-frozen samples of endometrial carcinoma and corresponding normal tissues, and correlated with promoter methylation of RAS association domain family-1A (RASSF1A). A highly significant decrease in sprouty 2 immunoexpression was seen in the proliferative phase of normal endometrium (P < .001). Differences were detected between types I and II endometrial carcinoma, but they were not statistically significant. Reduced immunoexpression of sprouty 2 was seen in 19.85% of endometrial carcinoma and was strongly and inversely associated with increased cell proliferation (Ki67; r = -0.367; P = .001). Sprouty 2 promoter methylation was detected in 31 (53.4%) of 58 endometrial carcinomas. Results from our study show that alterations in sprouty 2 may be involved in endometrial carcinogenesis by controlling cell proliferation.