Expression of small breast epithelial mucin (SBEM) protein in tissue microarrays (TMAs) of primary invasive breast cancers

International audienceExpression of small breast epithelial mucin (SBEM) protein in tissue microarrays (TMAs) of primary invasive breast cancers Aims: Small breast epithelial mucin (SBEM) is a recently described gene product that shows promise as a new breast biomarker. The aim was to investigate for the first time SBEM protein expression in a large cohort (n = 300) of invasive breast cancers, its relationship to established clinical variables and its association with clinical outcome. Methods and results: Immunohistochemical analysis was performed on tissue microarrays consisting of 149 oestrogen receptor (ER) a) and 151 ERa+ breast cancers. Overall, 18% of tumours were SBEM+ (n = 53 ⁄ 300). However, SBEM protein was more frequently observed in ER) (22%) than in ER+ cancers (13%; P = 0.049). A significant association with psoriasin ⁄ S100A7 expression (P £ 0.0001) was observed in the entire cohort. SBEM was also positively associated with HER-2 (P = 0.046) in ER) cancers, and increased levels of SBEM were strongly associated with higher tumour grade (P = 0.0015). Furthermore, SBEM expression showed a trend towards an association with reduced overall survival and relapse-free survival in the ER+ cohort (P = 0.063 and P = 0.072, respectively). Conclusions: Our results suggest that SBEM may identify a unique subset of breast cancers with poor prognosis and may have future implications for therapeutic management of this disease