Diacylglycerol kinase α is a critical signaling node and novel therapeutic target in glioblastoma and other cancers

Abstract

Although diacylglycerol kinase α (DGKα) has been linked to several signaling pathways related to cancer cell biology, it has been neglected as a target for cancer therapy. The attenuation of DGKα activity via DGKα-targeting siRNA and small-molecule inhibitors R59022 and R59949 induced caspase-mediated apoptosis in glioblastoma cells and in other cancers, but lacked toxicity in noncancerous cells. We determined that mTOR and hypoxia-inducible factor-1α (HIF-1α) are key targets of DGKα inhibition, in addition to its regulation of other oncogenes. DGKα regulates mTOR transcription via a unique pathway involving cyclic AMP. Finally, we showed the efficacy of DGKα inhibition with short hairpin RNA or a small-molecule agent in glioblastoma and melanoma xenograft treatment models, with growth delay and decreased vascularity. This study establishes DGKα as a central signaling hub and a promising therapeutic target in the treatment of cancer. Significance: DGKα, which converts diacylglycerol to phosphatidic acid, regulates critical oncogenic pathways, notably HIF-1α and mTOR. DGKα knockdown and small-molecule inhibition are selectively toxic to human cancer cells but not normal human cells, and DGKα inhibition slows tumor growth, decreases angiogenesis, and increases mouse survival in xenograft models. © 2013 American Association for Cancer Research.