Loss of ataxia telangiectasia mutated- and Rad3-related function potentiates the effects of chemotherapeutic drugs on cancer cell survival.

The diverse responses of human cells to various forms of DNA damage are controlled by a complex network of signaling proteins. There has been considerable interest in the components of this signaling apparatus as potential targets for new forms of anticancer therapy. In this report, we examine the contributions of an upstream signaling molecule, the ataxia telangiectasia mutated- and Rad3-related (ATR) protein kinase, to the resistance of cancer cells to DNA-damaging agents that are commonly used as anticancer therapeutics. Loss of ATR function in knock-in cancer cells strikingly enhanced the effects of several of the most commonly used therapeutic compounds, impeding the progression of the cell cycle and reducing long-term cancer cell survival. Loss of ATR function potentiated the toxicity of alkylating agents most strikingly, antimetabolites moderately, and double-strand break-inducing agents to a lesser extent. These results suggest that specific inhibition of ATR activity will be a valid strategy to increase the effectiveness of currently used modes of therapy.