Heterogeneous Patterns of CEBPa Mutation Status in the Progression of Myelodysplastic Syndrome and Chronic Myelomonocytic Leukemia to Acute Myelogenous Leukemia

Purpose: We aimed to assess the role of CEBPa mutations in the progression of myelodysplastic syndrome (MDS) to acute myelogenous leukemia (AML) and their cooperating mutations. Experimental Design: Mutational analysis of CEBPa with direct sequencing for each PCR product was done on matched bone marrow samples obtained from 50 adult patients with MDS at diagnosis and at AML transformation. Cloning analysis was used to determine the allelic distribution. Results: CEBPa mutations were identified in four patients at diagnosis of MDS, including one with refractory anemia with excess blasts and three with chronic myelomonocytic leukemia. At AML transformation, three patients retained the identical mutant clones as their initial diagnosis, three acquired the mutations, and one lost CEBPa mutation when she gained FLT3 /ITD mutation. Together, seven patients had CEBPa mutations throughout the disease course; four patients had NH2-terminal mutations resulting in a frameshift and truncation of the protein, three of them had two different mutations either on the same alleles or on different alleles, two had missense mutations, and one had a deletion in the basic region leucine zipper domain. Except for one with coexistence of N-ras mutation, no sample harbored cooperating mutations with FLT3 or N-ras genes. CEBPa mutations had no influence on the time to AML progression or overall survival. Conclusions: Our results show that CEBPa mutations play a role in a subset of patients with MDS, especially in chronic myelomonocytic leukemia. The mutation status was heterogeneous, exhibiting identical clone, clonal change, or clonal evolution during the progression to AML.