KMT2A and acute lymphoblastic leukemia: Because MLL‐fusions are also known to drive the development of B‐ALL, we then assessed the effect of MPA on CB cells expressing MLL‐Af4 that recapitulate t (4;11) pro‐B ALL (Lin et al, 2016) using a coculture assay with murine stromal cell line MS‐5 (Appendix Fig S4A).