Abstract P5-04-01: Expression of epithelial-mesenchymal transition (EMT)-related markers in primary tumors and matched lymph node metastases in breast cancer patients

Abstract

Abstract Background. Malignant tumors may include multiple cancer cell populations with various metastatic potential. More aggressive subpopulations might easier be captured in lymph nodes metastases (LNM) than in primary tumors (PT). We evaluated mRNA and protein levels of master EMT regulators: TWIST1, SNAIL and SLUG, protein levels of EMT-related markers: E-cadherin, vimentin, and expression of classical breast cancer receptors: HER2, ER and PR in PT and corresponding LNM. The results were correlated with clinicopathological data and patient outcomes. Methods. Formalin-fixed paraffin-embedded (FFPE) samples from PT and matched LNM from 42 stage II-III breast cancer patients were examined. Expression of TWIST1, SNAIL and SLUG was measured by RT-qPCR, with median as cut off for positive result. Protein expression was examined by immunohistochemistry on tissue microarrays. For TWIST1, SNAIL, SLUG, E-cadherin and vimentin >10% of positively stained cells defined positive result. ER and PR were scored according to Allred system, and HER2 - according to HercepTest criteria. Results were considered concordant if PT and LNM were both positive or both negative. Concordance was measured by estimating Cohen's kappa coefficient (κ), with κ value equal 1 indicating perfect agreement. Disease-free survival (DFS) and overall survival (OS) were compared using F-Cox test. Hazard ratios (HRs) with 95% confidence intervals (95% CI) were computed using Cox regression analysis. Results. On average, expression of TWIST1, SNAIL and SLUG was significantly higher in LNM compared to PT (P < 0.00001 for all). Gene and protein levels of TWIST1, SNAIL and SLUG were highly discordant between PT and matched LNM (Tab 1). Receptor conversion, particularly loss of ER and PgR, occurred in 18% and 29% of cases, respectively. Increased expression of TWIST1 and SNAIL in LNM was associated with shorter OS (p = 0.045 and p = 0.022, respectively) and DFS (p = 0.02 and p = 0.01, respectively), whereas their expression in PT had no prognostic impact. Negative-to-positive switch of TWIST, SNAIL and vimentin correlated with shorter OS and DFS. Conversion of ER and PR had no significant impact on survival. Conclusions. LNM are enriched in cells with more aggressive phenotype, marked by elevated levels of EMT regulators. High expression of TWIST1 and SNAIL in LNM, as well as negative-to-positive conversion of both TWIST1 and SNAIL confer worse prognosis, confirming the correlation of EMT with aggressive disease behavior. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-04-01.