Absence of EZH2 gene mutation in chronic myeloid leukemia patients in blast crisis.

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disease consisting of chronic phase (CP), accelerated phase (AP) and blast crisis (BC). In recent years, molecular mechanism of CMLBC has been comprehensively investigated. Based on the DNA sequencing, several somatic gene mutations in patients with CML-BC has been revealed. These gene including RUNX1, ASXL1, IKZF1, WT1, TET2, IDH1, IDH2, NRAS, KRAS, CBL, CBLB, TP53, and GATA2 (Zhang et al., 2008; Grossmann et al., 2011; Makishima et al., 2011). The histone methyltransferase gene EZH2 is the catalytic subunit of the PRC2 polycomb complex and mediates transcriptional repression through its histone methyltransferase activity (Grossmann et al., 2012). Mutations in the EZH2 gene were recently described in patients with B-cell lymphomas (Morin et al., 2010), chronic myelomonocytic leukemia (CMML) ( Jankowska et al., 2011), adult and pediatric acute myeloid leukemia (Makishima et al., 2010; Ernst et al., 2012), myelofibrosis (Guglielmelli et al., 2011), myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN) and the overlap myelodysplastic/myeloproliferative neoplasms (MDS/MPN) (Ernst et al., 2010; Makishima et al., 2010). It was revealed that EZH2 mutations were correlated with poor survival. Among patients with MDS/MPN, patients harboring EZH2 mutations had an inferior LETTER to the EDITOR