Apoptosis: A biomarker of high-risk phenotype in pediatric acute myeloid leukemia?

Dysregulation of apoptosis has been explored in acute myeloid leukemia (AML); yet, its correlation with clinical outcomes in pediatric AML is unknown. This study was aimed to analyze percentage of apoptosis and apoptosis mediated through the intrinsic pathway with clinical outcomes in patients with pediatric AML.

This prospective study included pediatric AML patients enrolled from July 2013 to August 2016. Annexin-V (marker of total apoptosis) and caspase-9 expression (marker of intrinsic pathway) was determined in baseline bone marrow (BM) samples by flow cytometery and compared with controls (unaffected BM of solid tumors and peripheral blood [PB] of unaffected siblings). Overall survival (OS) and event-free survival (EFS) were compared using log-rank test.

A total of 151 AML patients were enrolled, median age 10 (range: 0.7-18 years). Annexin-V expression in blast cells was significantly high in AML patients as compared to BM of subjects with solid tumors (P = 0.01) and PB of healthy subjects (P = 0.04). Caspase-9 expression in blast cells was not significantly different. Median annexin-V expression was significantly higher in patients with WBC count ≥11 000/mm³ (P = 0.02), poor-risk cytogenetics (P = 0.02), the absence of RUNX1-RUNX1T1 translocation (P = 0.004), and the absence of NPM1 mutation (P = 0.05). Patients with high annexin-V expression had significantly inferior OS (P = 0.05) in univariate analysis but not in multivariate analysis (P = 0.32).

Apoptosis as a whole was found to be activated in baseline BM samples of AML patients. High apoptosis may be associated with high-risk phenotype in this disease.