An autophagic switch in the response of tumor cells to radiation and chemotherapy.

Four different functional forms of autophagy have been observed to occur in tumor cells in response to chemotherapeutic drugs and radiation. Currently the different forms of autophagy are distinguished almost exclusively by determining the impact of autophagy inhibition on drug and radiation sensitivity. That is, it cannot otherwise be predicted whether the autophagy induced by radiation or chemotherapy is associated with resistance and the circumstances under which autophagy inhibition might be a useful strategy for enhancing sensitivity to therapy. This commentary highlights an additional level of complexity in the autophagy landscape, specifically that autophagy can switch its function even within the context of a specific external stress and/or a biological cancer model.