Elevated mitochondrial DNA copy numbers in pediatric acute lymphoblastic leukemia: A potential biomarker for predicting inferior survival.

BACKGROUND: Studies on mitochondrial DNA copy number reveal an increase or decrease in copy number that appears to be cancer specific, but data on acute lymphoblastic leukemia have been inconsistent regarding the significance of changes in mitochondrial DNA copies. The purpose of this pilot study was to analyze mitochondrial DNA copy number and mitochondrial DNA integrity.

PROCEDURE: Copy number and mitochondrial deletion ratios were estimated in the bone marrow of 51 patients and peripheral blood of 30 healthy controls using quantitative real-time PCR. The copy number values were correlated with prognostic markers in patients.

RESULTS: Significantly increased mitochondrial DNA copy number (P-value < 0.0001) and increased mitochondrial deletion ratios (P-value = 0.0018) were observed in patients compared with controls. The copy numbers were significantly decreased in patients after chemotherapy (P-value = 0.0232). Patients with higher copy numbers exhibited significantly inferior survival than patients with lower copy numbers (for event-free survival, P-value = 0.04 and overall survival, P-value = 0.1175).

CONCLUSIONS: Significant decreases in mitochondrial DNA copy number with therapy indicates that copy number could be evaluated as a potential marker for therapeutic efficacy and a higher mitochondrial DNA copy number could be a poor prognostic marker.