CEBPα Mutations in Childhood Acute Myeloid Leukemia.

Transcription factor CCAAT/enhancer binding protein alpha(C/EBPα) is essential for granulocyte differentiation. CEBPα mutations have been described in 7–10% of adult patients with acute myeloid leukemia (AML) at initial diagnosis and conferred a favorable prognosis. CEBPα mutations in childhood AML has not been reported yet. In this study, we sought to assess the frequency of CEBPα mutration, its clinicohematologic correlation and to analyze the cooperating mutations, including FLT3 and N-ras mutations in childhood AML. CEBPα mutations were analyzed in 117 children (age one day to 17 years, median 5 years) with de novo AML. CEBPα mutation status was examined by performing DNA polymerase chain reaction (PCR) followed by direct sequencing for each PCR product. CEBPα mutations were detected in 7 (6.0%) of 117 patients. Of the 7 patients with CEBPα mutations, 4 had FAB subtype of M2, 2 M1 and 1 M4. All had intermediate cytogenetics and comprised 11.5% (7/61) of the intermediate cytogenetic risk group. Five of the 7 mutations occurred in both N-terminal part and bZIP domain, one had N-terminal frameshift mutation and the remaining one had an inframe insertion in the bZIP domain. Clonal analysis using expand long template PCR assay with a primer pair covering entire coding sequence was performed in all 5 patients carrying two different mutations. The results demonstrated that one had homozygous combined mutation and 4 had heterozygous biallelic mutations with the cloned alleles carrying single mutations at N-terminal or bZIP domain in the different alleles or harboring combined mutations in the same alleles. None of the remission marrow samples obtained from 5 patients who had CEBPα mutations at diagnosis carried the mutations. FLT3-ITD mutations were detected in 2 of the 7 patients with CEBPα mutations compared to 15 of the 109 patients without CEBPα mutations. None of the patients carrying CEBPα mutations had FLT3-TKD mutations. Two of the 7 CEBPα(+) patients also harbored N-ras mutations compared to 10 of the 110 patients without CEBPα mutations. Taken together, 4 of 7 CEBPα(+) patients had cooperating mutations including FLT3-ITD or N-ras as compared to 27 in 109 CEBPα(−) patients (P=0.081). There were no statistical differences in age, WBC count, LDH level, 5-year overall survival and event-free survival between patients with and without CEBPα mutations; similar results were obtained if we only analyzed patients with intermediate cytogenetics. The present data showed that the frequency of CEBPα mutations in our series of childhood AML was similar to that in adults. CEBPα mutations were frequently associated with FLT3-ITD or N-ras mutations supporting the two-hit hypothesis for the pathogenesis of AML.