Co-expression of carcinoembryonic antigen-related cell adhesion molecule 6 and 8 inhibits proliferation and invasiveness of breast carcinoma cells.

The carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 6 and CEACAM8 form heterodimers and exert their effects. Therefore, we examined the effects of CEACAM6 and CEACAM8 co-expression in breast cancer. We first studied CEACAM6/8 expression using immunohistochemistry in 109 patients with breast cancer. We then established MCF-7 cells that were stably transfected with CEACAM8 and studied cell proliferation, invasion and adhesion. The number of CEACAM6 and CEACAM8 double-positive breast carcinoma cells significantly increased in patients with low histopathological grade and stage. Proximity ligation assay (PLA) confirmed high CEACAM6/8 expression in MCF-7 cells. CEACAM6/8 expression promoted the adhesion of MCF-7 cells to endothelial cell monolayers but inhibited their invasion and proliferation. Furthermore, CEACAM6 status in carcinoma cells was significantly higher in bone than in lung metastases. CEACAM6/8 expression is associated with the inhibition of vascular invasion and cell proliferation. CEACAM6 expression was also considered to be involved in bone metastases of breast cancer. This is the first study to demonstrate the possible role of CEACAM6/8 heterodimer and CEACAM6 expression in breast cancer patients.