Genome-wide screening identifies cell cycle control as a synthetic lethal pathway with SRSF2P95H mutation.

Current strategies to target RNA splicing mutant myeloid cancers proposes targeting the remaining splicing apparatus. This approach has only been modestly sensitizing and is also toxic to non-mutant bearing wild-type cells. To explore potentially exploitable genetic interactions with spliceosome mutations, we combined data mining and functional screening for synthetic lethal interactions with an Srsf2P95H/+ mutation. Analysis of mis-splicing events in a series of both human and murine SRSF2P95H mutant samples across multiple myeloid diseases (AML, MDS, CMML) was performed to identify conserved mis-splicing events. From this analysis, we identified that the cell cycle and DNA repair pathways were overrepresented within the conserved mis-spliced transcript sets. In parallel, to functionally define pathways essential for survival and proliferation of Srsf2P95H/+ cells, we performed a genome-wide CRISPR loss of function screen using Hoxb8 immortalized R26-CreERki/+ Srsf2P95H/+ and R26-CreERki/+ Srsf2+/+ cell lines. We assessed loss of sgRNA representation at three timepoints: immediately after Srsf2P95H/+ activation, and at one week and two weeks post Srsf2P95H/+ mutation. Pathway analysis demonstrated that the cell cycle and DNA damage response pathways were amongst the top synthetic lethal pathways with Srsf2P95H/+ mutation. Based on the loss of guide RNAs targeting Cdk6, we identified that Palbociclib, a CDK6 inhibitor, showed preferential sensitivity in Srsf2P95H/+ cell lines and in primary non-immortalized lin-cKIT+Sca-1+ cells compared to wild type controls. Our data strongly suggest that the cell cycle and DNA damage response pathways are required for Srsf2P95H/+ cell survival, and that Palbociclib could be an alternative therapeutic option for targeting SRSF2 mutant cancers.