Autophagy­mediated adaptation of hepatocellular carcinoma cells to hypoxia­mimicking conditions constitutes an attractive therapeutic target.

Hepatocellular carcinoma has extremely poor prognosis. In cancerous liver tissues, aberrant proliferation of cancer cells leads to the creation of an area where an immature vascular network is formed. Since oxygen is supplied to cancer tissues through the bloodstream, a part of the tumor is exposed to hypoxic conditions. As hypoxia is known to severely reduce the effectiveness of existing anticancer agents, novel valid therapeutic targets must be identified for the treatment of hepatocellular carcinoma. Generally, autophagy has been reported to play an important role in the adaptation of cancer cells to hypoxia. However, the exact role and significance of this process vary depending on the cancer type, requiring detailed analysis in individual primary tumors and cell lines. In the present study, we examined autophagy induced by cobalt chloride, a hypoxia­mimicking agent, in hepatocellular carcinoma cells with the aim to evaluate the validity of this process as a potential therapeutic target. We observed that treatment with cobalt chloride induced autophagy, including the intracellular quality control mechanism, in an AMPK­dependent manner. Furthermore, treatment with autophagy inhibitors (bafilomycin and LY294002) resulted in significant, highly­selective cytotoxicity and apoptosis activation under hypoxia­mimicking conditions. The knockdown of AMPK also revealed significant cytotoxicity in hypoxia­mimicking conditions. These results clearly demonstrated that autophagy, especially mitophagy, was induced by the AMPK pathway when hepatocellular carcinoma cells were subjected to hypoxic conditions and played an important role in the adaptation of these cells to such conditions. Thus, autophagy may constitute an attractive therapeutic target for the treatment of hepatocellular carcinoma.

An Adaptation System to Avoid Apoptosis via Autophagy Under Hypoxic Conditions in Pancreatic Cancer Cells.

BACKGROUND/AIM: Pancreatic cancer tissue is a hypoxic environment resistant to anticancer drugs. This study examined the role of autophagy as a response to hypoxic stress in pancreatic cancer. MATERIALS AND METHODS: Pancreatic cell lines (PANC-1, BxPC-3 and AsPC-1) were exposed to hypoxic conditions using cobalt chloride, a hypoxia-mimicking agent. Protein expression and cytotoxicity assays were performed to determine the effect of hypoxia on autophagy. RESULTS: When pancreatic cancer cells were exposed to hypoxia, autophagy was induced. The autophagy-inducing signal was dependent on the AMPK pathway. Inhibition of autophagy in a hypoxic state induced a remarkable cytotoxicity and enhanced apoptosis. When an AMPK inhibitor was added, cytotoxicity was observed in the hypoxic environment. CONCLUSION: The induced autophagy, dependent on the AMPK pathway, is a necessary survival strategy adopted by pancreatic cancer cells to adapt to hypoxic stress, and could be an attractive target for drug development.