RB1 and osteosarcoma: To confirm the dependency of RB1 null osteosarcoma models upon DYRK1A, we selected 14 osteosarcoma models and characterized these according to their RB1 mutation and protein expression status and established that multiple distinct DYRK1A siRNAs could replicate the RB1 selectivity observed in the initial screen as well as eliciting DYRK1A silencing (Figure S3).