Heterogeneity within AML with CEBPA mutations; only CEBPA double mutations, but not single CEBPA mutations are associated with favourable prognosis

Abstract

CCAAT/enhancer binding protein alpha (CEBPA) mutations in AML are associated with favourable prognosis and are divided into N- and C-terminal mutations. The majority of AML patients have both types of mutations. We assessed the prognostic significance of single (n=7) and double (n=12) CEBPA mutations among 224 AML patients. Double CEBPA mutations conferred a decisively favourable overall (P=0.006) and disease-free survival (P=0.013). However, clinical outcome of patients with single CEBPA mutations was not different from CEBPA wild-type patients. In a multivariable analysis, only double -- but not single -- CEBPA mutations were identified as independent prognostic factors. These findings indicate heterogeneity within AML patients with CEBPA mutations.

Figure 1

(A) Overall survival of AML patients without CEBPA mutations (wt; n=205), with a single (n=7), and with the combination of C- and N-terminal CEBPA mutations (double; n=12). Patients who are alive were censored at the last follow-up. X-axis indicates months, Y-axis is probability of survival. (B) Disease-free survival of AML patients without (wt; n=205)), with a single (n=7), or with double (n=12) CEBPA mutations. (C) Transient transfection experiments in H1299 cells using equal amounts of pcDNA3 expression plasmids encoding human CEBPA wild-type (wt), the N-terminal frame-shift mutation 245delC (as present in patient #3s in Supplementary Table S2), the C-terminal in-frame mutation 1079–1080insTCT (as present in patient #5s), and the combination of both plasmids. V: pcDNA3 expression plasmid alone. The luciferase reporter construct encodes an oligomeric CEBPA binding site. (D) Western blot analyses for CEBPA protein using whole-cell lysates of patients #27 (AML-M1 with a normal karyotype and no abnormalities in CEBPA, FLT3, and NPM1), #3s (AML-M2 with the N-terminal frame-shift mutation 245delC), #11d (AML-M1 with both the N-terminal 213insAG and the C-terminal 1088-1089insCCG mutations), and #5 s (AML-M1 with the C-terminal in-frame mutation 1079–1080insTCT). (E) Schematic presentation of CEBPA wild-type protein (upper panel) and the 30-kDa peptide initiated at the ATG at amino acid 120 (lower panel). Black bars indicate the two transactivation domains, and grey bars represent the region for DNA binding and homo-/heterodimerisation.