Chemotherapeutic Agents Subvert Tumor Immunity by Generating Agonists of Platelet-Activating Factor

Oxidative stress suppresses host immunity by generating oxidized lipid agonists of the platelet-activating factor receptor (PAF-R). Because many classical chemotherapeutic drugs induce reactive oxygen species (ROS), we investigated whether these drugs might subvert host immunity by activating PAF-R. Here we show that PAF-R agonists are produced in melanoma cells by chemotherapy that is administered in vitro, in vivo or in human subjects. Structural characterization of the PAF-R agonists induced revealed multiple oxidized glycerophosphocholines that are generated non-enzymatically. In a murine model of melanoma, chemotherapeutic administration could augment tumor growth by a PAF-R-dependent process that could be blocked by treatment with antioxidants or cyclooxygenase-2 inhibitors or by depletion of regulatory T cells. Our findings reveal how PAF-R agonists induced by chemotherapy treatment can promote treatment failure. Further, they offer new insights into how to improve the efficacy of chemotherapy by blocking its heretofore unknown impact on PAF-R activation.