Utility of BMI-1 and NANOG expression levels in survival prediction of pediatric acute lymphoblastic leukemia

BACKGROUND: Acute lymphoblastic leukemia (ALL) is the most common malignancy in children characterized by the overproduction and accumulation of immature lymphoid cells in the bone marrow and peripheral blood. The BMI-1 is an important component of the Polycomb Repressive Complex-1 (PRC1). It is an important molecule for the self-renewal of hematopoietic stem cells (HSCs). The BMI-1 expression is generally high in HSCs and decreases after cell differentiation. The BMI-1 is required for the maintenance of normal and cancer stem cells and has been reported as an oncogene in various tumors. The NANOG is a homeodomain transcription factor responsible for maintaining the stem cell compartment at the blastocyst stage of developing embryos. The NANOG gene has been proven to be transcribed in CD34+ cells and different leukemic cells. METHODS: The ribonucleic acid (RNA) was extracted from the peripheral blood mononuclear cells (PBMNCs) of 30 pediatric ALL patients (16 B-ALL and 14 T-ALL) and 14 healthy controls. The Bmi-1 and NANOG expression levels were determined using the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). RESULTS: Compared to normal controls, patients with ALL exhibited upregulated levels of Bmi-1 (p = 0.03). Patients who overexpressed Bmi-1 and NANOG displayed a significantly worse survival than low-expressing patients (hazard ratio (HR) 5.74, 95% confidence interval (CI):1.48–22, p = 0.012 and HR 3.8, 95% CI:1.009–14.3, p = 0.048, respectively). CONCLUSIONS: Taken together, these data suggest that the Bmi-1 and NANOG might serve as a novel survival predictor in ALL patients. Our observation also suggests that the Bmi-1 and NANOG could serve as new therapeutic targets for treatment of pediatric ALL.