Our conclusion is different from those of Kamens et al. that KMT2A::AFF1-expressing ALL cells are highly sensitive to Btz because of Btz-induced histone H2B de-ubiquitylation, which leads to H3K79 demethylation and subsequent downregulation of KMT2A::AFF1 expressing genes37. The gene discussed is AFF1; the disease is acute lymphoblastic leukemia.