GSE61826
PARALLEL IN VIVO AND IN VITRO MELANOMA RNAi DROPOUT SCREENS
To identify factors preferentially necessary to drive tumor expansion we performed parallel in vitro and in vivo negative selection shRNA screens. Melanoma cells harboring shRNAs targeting several DNA Damage Response (DDR) kinases had a greater selective disadvantage in vivo than in vitro, indicating an essential contribution of these factors during tumor expansion. In growing tumors, DDR kinases were activated following hypoxia. Correspondingly, depletion or pharmacologic inhibition of DDR kinases was toxic to melanoma cells, including those that were resistant to BRAF inhibitor, and this could be enhanced by angiogenesis blockade. These results reveal that hypoxia sensitizes melanomas to targeted inhibition of the DDR and illustrate the utility of in vivo shRNA dropout screens for identification of pharmacologically tractable targets. Overall design: A lentivirus-based kinome shRNA library (four pools) was used to transduce 888mel cells (MOI<0.2). After puromycin selection (1µg/ml), two reference samples were collected as controls. Next, tumor cells (5x105 per injection) were either injected s.c. into 6 NSG mice or plated into 6 independent plates (5x105) for in vitro culture. Tumors were removed from the mice and genomic DNA used to recover shRNAs by PCR amplification followed by deep sequencing. Three analyses were performed independently in parallel: (1) Tumors versus cultured cells (Log2 Fold Change < -1); (2) Tumors versus references (Log2 Fold Change < -2.5) and (3) Cultured cells versus references (Log2 Fold Change < -2.5). Genes targeted with at least 2 shRNAs in each of the analysis were considered hits with an enhanced in vivo effect.