A novel apoptosis-inducing monoclonal antibody (anti-LHK) against a cell surface antigen on colon cancer cells

Background. Apoptosis is a crucial element in the behavior of mammalian cells in many different situations. We here report the establishment of a novel monoclonal antibody (anti-LHK mAb) that has apoptosis-inducing activity against colon cancer Colo205 cells. Methods. The mechanism of anti-LHK mAb-induced cell death was assessed by microscopic morphology, Annexin V/Hoechst 33528 staining, and detection of DNA fragmentation. The molecular weight of LHK antigen was determined by Western blotting. Growth inhibition of Colo205 cells induced by anti-LHK mAb was determined by in vitro and in vivo studies. Results. Anti-LHK reacted with a 70-kDa antigen and completely blocked the proliferation of Colo205 cells bearing LHK in vitro in a manner characteristic of apoptosis. Strikingly, anti-LHK mAb suppressed tumor growth in a murine peritoneal dissemination model. Conclusions. LHK antigen, which is restricted to epithelial cells, may be a novel death receptor that plays a critical role in controlling the growth, invasion, and metastasis of human colon cancer cells.