Enhancer Role of rMnSOD in apoptosis triggering by daunorubicin of pediatric B-ALL cells.

Background/Objectives Leukemic cells produce higher amounts of ROS than healthy cells and express low levels of antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD). Recently, it was demonstrated that rMnSOD, a recombinant new isoform of MnSOD, recently isolated from human liposarcoma cell line, is able to trigger apoptosis of human T-ALL cells (99%) without toxic effects on healthy cells. The present study was aimed to verify if rMnSOD is able to induce apoptosis and to stop in G0/G1 stage of the cell cycle in pediatric patients with B-cell acute lymphoblastic leukaemia (ALL) and if it displays synergic action with daunorubicin. Design and Methods Cells were collected from three patients diagnosed for B-cell ALL at the Pediatric Oncology of University “Luigi Vanvitelli”. Cell viability, apoptosis and cell cycle of lymphoblasts and SUP-B15 cell line (ATCC) were analyzed through “ Muse Kit” after rMnSOD treatment. ROS analysis was detected with NAC. Apoptotic fragmentations of SUP-B15 were demonstrated by confocal imaging. Results We observed that low concentrations of rMnSOD are able to trigger apoptosis of SUP-B15 cell line and B-ALL cells from pediatric patients. In detail, we observed an apoptosis rate from 30% to 46% in B-ALL pediatric patient cells and of 45% in SUP-B15 cell line. Instead, cell cycle analysis showed a cell fraction decrease in G0/G1 phase. Moreover, the synergic activity of rMnSOD and Daunorubicin induces apoptosis in 92% of cells, by comparing the treatment with the single substances, rMnSOD (64,7%) and Daunorubicin (23,9%). Confocal microscopy analysis revealed internalization of rMnSOD in SUP-B15 cells and evident apoptotic alterations, such as nuclear fragmentations and apoptotic-bodies. In conclusion, rMnSOD exerts toxic activity only against cancer cells, by enhancing drug effect, thus allowing to utilize lower concentration of standard chemotherapy to increase the apoptosis level.