Systematic identification of anticancer drug targets reveals a nucleus-to-mitochondria ROS sensing pathway

Multiple anticancer drugs have been proposed to cause cell death, in part, by increasing the steady-state levels of cellular reactive oxygen species (ROS). However, for most of these drugs exactly how the resultant ROS function and are sensed is poorly understood. It remains unclear which proteins the ROS modify and their roles in drug sensitivity/resistance. To answer these questions, we examined 11 anticancer drugs with an integrated proteogenomic approach identifying many unique targets but also shared ones–including ribosomal components, suggesting common mechanisms by which drugs regulate translation. We focus on CHK1 which we find is a nuclear H2O2 sensor that launches a cellular program to dampen ROS. CHK1 phosphorylates the mitochondrial-DNA binding protein SSBP1 to prevent its mitochondrial localization, which in turn decreases nuclear H2O2. Our results reveal a druggable nucleus-to-mitochondria ROS sensing pathway–required to resolve nuclear H2O2 accumulation and mediate resistance to platinum-based agents in ovarian cancers.