Role of rMnSOD as Cytotoxic Agent and Chemotherapy Enhancer in Paediatric Acute Lymphoblastic Leukemia B Cells

Background/Objectives: An isoform of Manganese-superoxide-dismutase (rMnSOD) was isolated and sequenced for the first time from a human Liposarcoma cells and obtained in recombinant form. The protein showed a specific and selective cytotoxicity on many cancer cell lines. rMnSOD enters cells by means of its 24-aa leader peptide that linked to the oestrogen receptor (ER). A 6-aa sequence, that participates in ER binding, was identified as a molecular carrier by mass spectrometric analysis. The aim of this study was to test the ability of this molecule to inhibit the growth of SUP-B15 cell line and leukemic B-cells and kill them alone and as enhancer of chemotherapic drug. Design/Methods: SUP-B15 cell line and leukemic B cells were cultured in RPMI medium and treated for 5 hours with rMnSOD and Daunoblastine, single and in combination. Cell viability assay was analyzed by MUSE analyzer (Millipore). Apoptotic cell death and cell cycle were analyzed by Annexin-V-FITC staining and PI fluorescence.We analyzed ER expression levels by Real time PCR. Results: A high level of ER was observed in SUP-B15. Our preliminary data showed that in SUP-B15 cell line rMnSOD induced apoptosis with a reduction of vitality from 61.9% to 31.40% respect to untreated. Treatment with rMnSOD of leukemic cell samples showed in all apoptotic profiles an increase in late apoptosis up to 52%. Better apoptotic induction was observed in prednisone poor responders. Cell cycle analysis showed an arrest in Go/G1 after treatment. Conclusion: rMnSOD is a promising molecule for the treatment of paediatric B-ALL due to its selective action to cancer cells and to its enhancer action which leads to reduction of drug dose and significantly reducing side effects. Targeted delivery can increase the therapeutic index of conventional chemotherapy, with low doses to kill cancer cells.