Chemotherapy has been widely used in cancer treatment, but the prognosis of the cancer patients following chemotherapy has not been substantially improved. Alternative strategies such as immunotherapy and their combinations with chemotherapy are now being considered; however, the effects of chemotherapy on the immune responses of cancer cells are not fully understood. In the present studies, we reveal a potential link between chemotherapy and cancer immunoresistance, we first examined the effects of chemopreventive agent DDP on the expression of a cell surface glycopreotein Trop-2 in lung cancer cells, and found that DDP not only induce Trop-2 surface expression in human lung cancer cells, but also induce T-cell apoptosis effectively. In order to investigate the relationship between DDP-induced Trop-2 expression and T-cell apoptosis, we stably transfected A549 and PC14 lung cancer cells with Trop-2 shRNA, the DDP-induced Trop-2 surface expression was effectively decreased in stably transfected cell lines, but chemotherapeutic reagent-induced cell proliferation inhibition and apoptosis were increased through inhibition of the MAPK signaling pathway. In vivo animal experiments showed that Trop-2 knockdown tumors displayed a slower growth rate than the control xenografts. Importantly, DDP treatment exhibited a strong antitumor activity in the mice with Trop-2 knockdown tumors, but only a marginal effect in the control group. Taken together, our data show that DDP resistance in lung cancer cells could be induced through increased surface expression of Trop-2, which at least partially by interfering with MAPK pathway. These results provide novel insight into the function of Trop-2 and encourage the design and testing of approaches targeting this protein and its partners.
Keywords: DDP; MAPK; Trop-2; immunoresistance; lung cancer.