Because SMARCA4/SMARCA2-deficient and SS18–SSX fusion cancer cells depend on transcriptional upregulation of KREMEN2 due to SMARCA4/SMARCA2 deficiency and SS18–SSX fusion, we clarified that synthetic lethality is induced by repressing expression of KREMEN2 by simultaneous inhibition of CBP/p300. The gene discussed is CREBBP; the disease is cancer.