Towards novel radiosensitizing agents: the role of cytosolic PLA2α in combined modality cancer therapy.

The radioresistant nature of some tumors serves as an obstacle to curative therapy for several poor-prognosis malignancies. The radiosensitivity of a cancer is dependent not only on the intrinsic ability of tumor cells to recover from radiation-induced damage, but also the ability of stromal elements (e.g., vasculature) in the tumor microenvironment to survive and continue proliferating in the face of ionizing radiation. In this regard, it is important to understand the initial events activating radiation-induced signal transduction pathways. Among these events is the activation of cytosolic phospholipase A2 α and the subsequent production of the lipid second messengers. These events occur within minutes following exposure to ionizing radiation, and have been shown to enhance cell viability through a number of prosurvival signaling pathways. Furthermore, inhibition of cytosolic phospholipase A2 α has now been shown to reduce the viability of endothelial cells in culture after exposure to ionizing radiation, as well as slowing the growth of tumors in animal models of cancer.