Abstract 893: Associations between HGF, MET, and phospho-MET expression, overall survival, and HGF genotypes in epithelial ovarian cancer

Abstract

Abstract Background. The hepatocyte growth factor (HGF) signaling pathway regulates key cellular functions related to tumor invasion and metastasis including cell motility, cell proliferation, and morphogenesis. We previously found that minor alleles at a single-nucleotide polymorphism (SNP; rs5745709) in the gene encoding the cytokine HGF was associated with poorer overall survival in women with invasive epithelial ovarian cancer (EOC) enrolled at Mayo Clinic (MAY) and The Cancer Genome Atlas (TCGA) (HR 1.6, 95% CI 1.3-1.9, p=8.9×10−5). In addition, we found that that genotype correlated with HGF expression in ovarian cancer tissue from TCGA women, suggesting that genetically-regulated expression of HGF may play a role in post-diagnosis survival. To further examine this possibility, we evaluated intensity of antibody immunostaining for HGF, MET (HGF's transmembrane tyrosine kinase receptor), and phospho-MET (pMET; MET's activated form) in tumor cells using tissue microarrays (TMAs) created from genotyped primary peritoneal and EOC cases, and correlated these expression levels with overall survival and HGF SNP genotypes. Methods. Participants were 326 white non-Hispanic women over 20 years of age with histologically-confirmed invasive EOC diagnosed between 1998 and 2009. All cases were enrolled at MAY within one year of diagnosis. Five μm sections of TMAs including three 0.6 mm cores per case were immunostained with HGF, MET, and pMET primary antibodies. Staining levels were classified according to combinations of staining extent and intensity as negative (< 10% cells stained), weak, moderate, or strong. The maximal expression value recorded over the multiple cores for each case was used. Cox proportional hazards regression was used to examine associations of overall survival with HGF, MET and pMET expression levels, adjusted for relevant clinical variables. Associations between expression levels and HGF SNP rs5745709 genotypes were examined using linear regression models. Results. HGF and MET expression were not associated with overall survival in our series of EOC cases (p=0.48 and 0.90, respectively). pMET expression was associated with survival, but in the opposite direction of that hypothesized (HR 0.77, 95% CI 0.39-1.52 for moderate expression; HR 0.55, 95% CI 0.27-1.10 for strong expression; each referent to negative/weak, p=0.01). Expression levels were not significantly associated with HGF rs5745709 genotypes (p=0.80 for HGF expression, p=0.89 for MET, p=0.41 for pMET). Conclusion. HGF expression levels were not associated with overall survival or with HGF SNP genotypes that correlated with survival in a previous study. Functional studies such as this one are crucial as a follow-up to discovery-based studies in order to assess biologic plausibility of observed results. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 893. doi:10.1158/1538-7445.AM2011-893