RUNX1 and breast cancer: Direct sequencing of coding regions of AML1 amplified by RT-PCR revealed the presence of mutations in 3 (25%) of 12 evaluable CML-BC patients: G190R, R135EfsX42 and A297LfsX7. AML1 mutations were not found in any of the 5 CML-BC cell lines examined (exons 3–5 of MegA2 were excluded because of the consistent failure of RT-PCR-mediated amplification).