Transcription profiling of human core binding factor acute myeloid leukemias to identify molecular subclasses within the group

Core binding factor (CBF) leukemias, characterized by either inv(16)/t(16;16) or t(8;21), constitute acute myeloid leukemia (AML) subgroups with favorable prognosis. However, there exists substantial biological and clinical heterogeneity within these cytogenetic groups, which is not fully reflected by the current classification system. To improve the molecular characterization we profiled gene expression in a large series (n=93) of AML patients with CBF leukemia [inv(16) n=55, t(8;21) n=38]. By unsupervised hierarchical clustering we were able to define a subgroup of CBF cases (n=35) characterized by shorter overall survival times (P=0.03). While there was no obvious correlation with fusion gene transcript levels, FLT3 tyrosine kinase domain, KIT, and NRAS mutations, the newly defined inv(16)/t(8;21)-subgroup was associated with elevated white blood cell counts and FLT3 internal tandem duplications (P=0.011 and P=0.026, respectively). Supervised analyses of gene expression suggested alternative cooperating pathways leading to transformation. In the ?favorable? CBF leukemias anti-apoptotic mechanisms and deregulated mTOR-signaling, and in the newly defined ?unfavorable? subgroup aberrant MAPKinase-signaling and chemotherapy-resistance mechanisms might play a role. While the leukemogenic relevance of these signatures remains to be validated, their existence nevertheless supports a prognostically relevant biological basis for the heterogeneity observed in CBF leukemia.