CDKN2A and chronic myelogenous leukemia, BCR-ABL1 positive: However, CDKN2A/B deletions do not occur in CML; probably because the leukemia arises from HSC-like progenitors [123,125], in which the CDKN2A/B locus is epigenetically silenced and “poised” to respond to an abnormally higher and sustained threshold of hyperproliferative signals [122].