UPR activation alters chemosensitivity of tumor cells.

A growing body of literature demonstrates that the unfolded protein response (UPR) is activated in a number of tumors. Recent data suggests that the UPR may play a role in protecting transformed cells from the inadequate environment that exists prior to vascularization and therefore contribute to tumor growth and survival. In addition, data from cell culture based studies demonstrate that pharmacological activation of the UPR can alter the sensitivity of cells to chemotherapeutic agents, making them either more sensitive in some cases or more resistant in others. Thus, it will be important to understand and integrate data on the role of the UPR in tumor growth and survival with studies on the effects of UPR activation on chemosensitivity before considering therapeutic interventions into this signaling pathway.