Expression profile of CADM1 and CADM4 in triple negative breast cancer with primary systemic therapy

Triple negative breast cancer (TNBC) is defined by a lack of ER, PgR, and HER2 expression, and to date there have been no significant advances in treatment by targeted therapies against those molecules. Therefore, primary systemic therapy (PST) followed by surgery is the standard therapy for patients with advanced TNBC. According to gene expression analysis, TNBC has a distinct profile when compared with non-TNBC, suggesting that a unique gene affects the treatment efficacy of PST. Cell adhesion molecule (CADM) genes encode an immunoglobulin superfamily molecule involved in cell-to-cell adhesion in a variety of human epithelial cells. While it has been reported that inactivation of CADM1 and CADM4 serves a pivotal role in the progression of breast cancer, a full analysis has not been completed for TNBC. Previous studies have reported that CADM1 and CADM4 expression is less likely to be decreased in TNBC than in non-TNBC. In the present study, CADM1 and CADM4 expression was evaluated in patients with TNBC who had received PST. The present study revealed that loss or weak expression of CADM1 was frequently observed in non-pathological complete response patients. Furthermore, while the majority of TNBC cases exhibited high CADM1 expression, a small number of cases exhibited low CADM1 expression and low therapeutic response of PST for TNBC. These results suggest that CADM1 has a pivotal role in anti-PST efficacy in patients with TNBC.