Pan-cancer analysis of non-oncogene addiction to DNA repair

Abstract Cancer cells usually depend on the aberrant function of one or few driver genes to initiate and promote their malignancy, an attribute known as oncogene addiction. However, cancer cells might become dependent on the normal cellular functions of certain genes that are not oncogenes but ensure cell survival (non-oncogene addiction). The downregulation of DNA repair genes and the consequent genetic and epigenetic instability is key to promote malignancy, but the activation of the DNA-damage response (DDR) has been shown to become a type of non-oncogene addiction that critically supports tumour survival. While we know that different cancer types can become dependent on specific DDR genes for their survival, a systematic evaluation of DNA repair addiction at the pan-cancer level is missing. In the present study, this systematic evaluation was addressed using data derived from The Cancer Dependency Map and The Cancer Genome Atlas (TCGA). Following this approach, 59 DDR genes were identified as commonly essential in cancer cells with 14 genes being exclusively associated with better overall patient survival and 19 with worse overall survival. Notably, a specific molecular signature among the latter, characterized by DDR genes showing the weakest dependency scores, but significant upregulation was strongly associated with worse survival, supporting the presence and relevance of non-oncogenic addiction to DNA repair in cancer. Particularly, UBE2T, RFC4, POLQ, BRIP1, and H2AFX represent the best predictors of poor overall survival, and some might represent promising therapeutic targets, especially under the synthetic lethality approach.