AFF1 and acute lymphoblastic leukemia: The complete loss of PROM1/CD133, which was shown to be transcriptionally regulated via KMT2A::AFF1-mediated H3K79me2/3 enhancer–promoter interactions, [29] in SEMPINO_RES is highly remarkable, since the expression of PROM1/CD133 was reported to be essential for leukemic cell growth in KMT2A-rearranged ALL [29, 30].