Ubenimex Activates the E‐Cadherin‐mediated Adhesion of a Breast Cancer Cell Line YMB‐S

It has been reported that ubenimex, a biological response modifier, has a direct anti‐tumor effect. To clarify the mechanism involved, we examined the effects of ubenimex on the growth and adhesive property of a breast cancer cell line YMB‐S. The cells proliferate in a floating manner without aggregation in normal complete medium. Ubenimex induced cell‐cell and cell‐surface adhesion of the cells accompanied with growth suppression. E‐Cadherin localized at cell‐cell contact sites of adhered cells, and anti‐E‐cadherin antibody inhibited the adhesion. Both Western blot analysis and binding assay disclosed that there was no apparent difference between E‐cadherin levels of the cells before and after the treatment with ubenimex. These results indicate that ubenimex inhibits the proliferation of YMB‐S cells and augments cell‐to‐cell adhesion through the induction of E‐cadherin ‐mediated adhesion resulting from the functional activation of pre‐expressed but inefficient E‐cadherin.