Importantly, using a PDX model generated from a patient with MCL who had ATM mutations and deletion of exon 7 in the TP53 at diagnosis and relapsed after CD19-directed CAR T-cell therapy, we observed that PRMT5 inhibitor treatment markedly attenuated the tumor growth (Fig. 5m, n), with decreased methylation of PRMT5 substrate histone H4R3me2s (Fig. 5o). The gene discussed is CD19; the disease is mantle cell lymphoma.