TNF-alpha induces caspase 3 (CPP 32) dependent apoptosis in human cholangiocarcinoma cell line

Cholangiocarcinoma (CCA), a malignant tumor derived from bile duct epithelium, occurs with a higher incidence in tropical countires especially in some areas of Southeast Asian countries such as Thailand. This tumor is relatively resistant to chemotherapy. In this study, molecular mechanism of killing of this tumor by TNF-alpha was investigated. Human cholangiocarcinoma cell line (HuCCA-1) was developed and used as a model for treatment. Activation of HuCCA-1 with TNF-alpha in the present of actinomycin D (1 microg/ml) caused death of the tumor cells. Western blotting analysis of the cells extracted demonstrated the cleavage of poly (ADP-ribose) polymerase (PARP) within 6-8 hours following TNF-alpha treatment indicating apoptotic death. The cleavage of PARP was inhibited when the cell line was pretreated with peptide inhibitor, Ac-DEVD-CHO, suggesting that apoptosis induced by TNF-alpha of this cell line involves activation of caspase II subfamily. The procaspase 3 (proCPP-32), one of the caspase group II subfamily was degraded after the HuCCA- I cell line was treated with TNF-alpha. Furthermore, Gelsolin, an 83 kDa protein which is identified as caspase 3 substrate, was cleaved to 43 kDa fragments after the cells were treated with TNF-alpha. These results indicate that apoptosis of human cholangiocarcinoma cell line as induced by TNF-alpha treatment is mediated through caspase 3.