8O_PR MUCIN-1 Protein and Mrna Expression in Breast Cancer Patients Treated with Neoadjuvant Chemotherapy

Abstract

ABSTRACT Mucin-1 (MUC1) is expressed in normal breast epithelium and invasive breast cancer. It has pleiotropic effects on tumour biology, e.g. regulation of cell polarity, crosstalk with cellular signalling and regulation of immune response. Tumor vaccines targeting MUC1 are currently tested in clinical trials. The aim of this study was to evaluate the frequency of MUC1 expression and its predictive value for response and survival after neoadjuvant anhracycline/taxane-based chemotherapy. We investigated MUC1 protein (n = 691) and mRNA (n = 268) expression in pre-treatment core biopsies from participants of the GeparTrio trial by immunohistochemistry and quantitative RT-PCR from formalin-fixed paraffin-embedded (FFPE) samples. MUC1 protein expression was detectable in 656 (95%) cases; mRNA levels covered a range of 103 copy numbers. Protein and mRNA expression were correlated (p High MUC1 protein and mRNA expression were more frequently in HR+ (hormone-receptor positive) tumors (p Low MUC1 protein and mRNA expression were predictive for pCR (pathologic complete response) in the overall population (p MUC1 protein expression was a positive prognostic marker for survival in the overall population (p = 0.03) and in HER2- (p = 0.005) tumors. MUC1 mRNA was prognostic in the overall population (p MUC1 is frequently expressed in a large cohort of breast cancer, especially in HR+ tumors. Evaluation is feasible by immunohistochemistry and quantitative RT-PCR from FFPE tissue and provides information on therapy response and survival following neoadjuvant chemotherapy. MUC1 expression may serve as a predictive marker in clinical immunotherapy trials. Disclosure All authors have declared no conflicts of interest.