Since AML models with KMT2A rearrangements are particularly sensitive to PL treatment, we performed colony-forming cell (CFC) assays to determine whether PL affects the ability of AML cell lines harbouring KMT2A rearrangements (MV-4-11, MOLM-13, Cas9 Flt3-ITD MLL-AF4 and MLL-AF9) to initiate colony formation, an in vitro surrogate for leukaemia stem/progenitor activity. Here, AFF1 is linked to acute myeloid leukemia.