Abstract A25: CK 5/6 and EMT-markers as poor prognostic factors in breast cancer patients

Abstract

Abstract Introduction: Cytokeratins 5/6 are expressed in basal layer of breast epithelium and are considered as markers of poor prognosis in breast cancer patients. It was also shown that tumors expressing basal markers often present phenotypical changes connected with epithelial-to-mesenchymal transition (EMT), like vimentin expression and E-cadherin loss. The aim of this study was to evaluate the expression of master regulators of EMT - TWIST, SNAIL and SLUG in breast cancer samples and correlate it with expression of CK 5/6 and markers of EMT - E-cadherin and vimentin. Materials and Methods: Fresh-frozen and FFPE tumor samples from 136 consecutive, stage l-III breast cancer patients were examined. Expression of TWIST, SNAIL and SLUG in frozen tissues was measured by RT-qPCR method using ΔΔCt approach. Expression of CK 5/6, E-cadherin and vimentin was analyzed in FFPE material with a use of immunohistochemical staining of tissue microarrays (TMA-IHC). Based on the median gene expression level or intensity of the IHC staining samples were classified as positive or negative for a particular marker. Results were correlated with clinicopathological data of the patients and their outcome. Results: CK 5/6 staining was positive in 19 (11.3%) of the samples and correlated positively with presence of EMT phenotype (0.00027, χ2 test), with 58% and 19.5% of EMT-positive samples in CK5/6 positive and negative subgroup, respectively. Moreover, elevated expression of SNAIL mRNA was detected more often in CK 5/6 positive than in negative samples (89% vs. 51 %, p=0.032, Fisher's exact test). Elevated expression of TWIST (p=0.05, Fisher's exact test) and SNAIL (p=0.003, Fisher's exact test) genes was found in tumors with EMT phenotype. No correlation was found between TWIST, SNAIL, SLUG protein levels as well as SLUG gene expression and EMT phenotype. Expression of CK 5/6 was associated with decreased DFS (p = 0.00044, log-rank test) and OS (p = 0.00001, log-rank test), while occurrence of EMT phenotype with worse OS (p=0.01, log-rank test) Conclusions: CK 5/6 was found to be a marker of poor prognosis in terms of DFS and OS in the whole studied group of patients. EMT phenotype and SNAIL gene overexpression were more frequent in CK 5/6-positive tumors, which suggests a link between basal phenotype of the tumors and their predisposition to undergo EMT process. As EMT is thought to confer aggressive behavior of the tumor, this correlation might explain the observed negative impact of CK5/6 positive tumors on patients' survival. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A25.