KMT2A and acute lymphoblastic leukemia: To analyze the effect of MLL rearrangements expression on telomere transcription, we quantified the levels of UUAGGG repeat-containing RNA in a panel of MLL-r and non-MLL-r myeloid and lymphoblastic leukemia cell lines (Table 1) by slot-blot analysis with a 5′-(CCCTAA)4-3′ probe, which gives an unbiased quantification of UUAGGG repeat content in a cell (Figure 2A).