The translational repair pathway is a frequent synthetic lethal target in cancer
Synthetic lethality exploits the genetic vulnerabilities of cancer cells enabling, a targeted, precision approach to treat cancer. Synthetic lethal discovery approaches have led to clinical successes of PARP inhibitors and the progression of several next-generation therapeutic targets such as WRN, USP1, PKMYT1, POLQ, and PRMT5 into the clinic. To date, however, most discovery efforts in the synthetic lethal space have focused on DNA repair.  Here, we show, for the first time in humans, a frequent synthetic lethal interaction between two complexes of the translational repair pathway, PELO/HBS1L and the superkiller (SKI) complex. In distinct genetic contexts, either in 9p21.3 (FOCAD) deleted or MSI-H tumors, we found that phenotypically destabilized SKI complex leads to dependence on the PELO/HBS1L ribosomal rescue complex. We estimate that 20% of all tumors have a destabilized SKI complex. The concomitant loss of PELO in a SKI destabilized tumor drives an unfolded protein stress response, cell cycle arrest, and robust tumor growth inhibition. Furthermore, we demonstrate that the loss of HBS1L phenocopies PELO loss, presenting a second potential therapeutic target within the rescue complex. Our results indicate that PELO/HBS1L represent novel therapeutic targets whose dependence converges upon SKI complex destabilization, a common phenotypic biomarker in diverse genetic contexts and a significant patient population. Overall design: To understand the impact of PELO or HBS1L loss in SKI destabilized lines, we performed RNAseq on MIAPACA2 PELO and HBS1L dox-inducible knockout systems. Samples were prepped in triplicate at 48 and 96 hours post induction of PELO or HBS1L knockout.