Glutathione and the switch of aerobic metabolism collaborate for multi-drug resistance of neuroblastoma

The availability of antioxidants is recognized as one of the critical factors able to make cancer cells resistant to chemotherapy. In this context, it has been demonstrated that many chemoresistant cancers display high levels of glutathione (GSH) and consequently, its depletion by L-buthionine sulfoximine (BSO), has been proposed as a chemosensitizing therapy. To investigate the role of GSH and of tumor metabolism in multi-drug resistance (MDR), HTLA-230 neuroblastoma cells were chronically treated with etoposide at a concentration that in vitro mimics the clinically-used dose. The selected cells (HTLA-Chr) were highly tumorigenic and acquired MDR, becoming less sensitive to etoposide or doxorubicin compared to parental cells. Moreover, HTLA-Chr cells, while having an efficient aerobic metabolism, owing to a favourable P/O ratio and a decreased formation of lactic acid, were also characterized by an up-regulation of catalase and higher levels of GSH. BSO treatment of HTLA-Chr cells markedly reduced their tumorigenicity that was, instead, enhanced by N-Acetylcysteine, able to promote GSH synthesis. Collectively, our results show that GSH and the switch of aerobic metabolism collaborate for the acquisition of MDR, providing pre-clinical evidence that may drive future therapeutic approaches for sensitizing neuroblastoma to conventional therapies.