YTHDC1 is a Therapeutic Target for B-cell Acute Lymphoblastic Leukemia by Attenuating DNA Damage Response Through the KMT2C-H3K4me1/me3 Epigenetic Axis

B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive malignancy characterized by the aberrant accumulation of immature and dysfunctional B cells in bone marrow (BM). Although chemotherapy and other therapies have been widely applied, some patients such as relapsed or drug-refractory (R/R) B-ALL patients exhibit limited response. YT521-B homologous domain-containing protein 1 (YTHDC1) is a nuclear reader of N-methyladenosine (mA) RNA modification, which has been implicated in different malignancies including leukemia. In the current study, we show that YTHDC1 is highly expressed in B-ALL cells. YTHDC1 knockdown attenuated B-ALL cell proliferation and cell cycle progression in vitro, and prolonged survival of mice in the human B-ALL xenograft model in vivo attributable to compromised leukemogenesis. Mechanistically, YTHDC1 knockdown significantly increased the accumulation of endogenous and chemotherapeutic agents-induced DNA damage in B-ALL cells. Furthermore, we identified that YTHDC1 binds to and stabilizes mA-modified KMT2C mRNA. KMT2C is a key enzyme catalyzing histone H3K4 methylation required for the expression of DNA damage response (DDR)-related genes, implying that YTHDC1 inhibitors might improve chemotherapy by attenuating DDR via reducing KMT2C. Indeed, with molecular docking and biochemical experiments, we identified EPZ-5676 as a YTHDC1 inhibitor, and combination of EPZ-5676 with Cytarabine (Ara-c) significantly improved the efficacy of chemotherapy in B-ALL mouse models using YTHDC1 primary and lined B-ALL cells. Collectively, YTHDC1 is required for DDR in B-ALL cells by upregulating DDR-related gene expression via stabilizing mA-modified KMT2C mRNA, thereby leading to increased histone H3K4 methylation, and targeted inhibition of YTHDC1 is a potentially new therapeutic strategy against B-ALL, especially YTHDC1 B-ALL.