Glutathione-mediated antioxidant response and aerobic metabolism: two crucial factors involved in determining the multi-drug resistance of high-risk neuroblastoma

Abstract

Neuroblastoma, a paediatric malignant tumor, is initially sensitive to etoposide, a drug to which many patients develop chemoresistance. In order to investigate the molecular mechanisms responsible for etoposide chemoresistance, HTLA-230, a human MYCN-amplified neuroblastoma cell line, was chronically treated with etoposide at a concentration that in vitro mimics the clinically-used dose. The selected cells (HTLA-Chr) acquire multi-drug resistance (MDR), becoming less sensitive than parental cells to high doses of etoposide or doxorubicin. MDR is due to several mechanisms that together contribute to maintaining non-toxic levels of H2O2. In fact, HTLA-Chr cells, while having an efficient aerobic metabolism, are also characterized by an up-regulation of catalase activity and higher levels of reduced glutathione (GSH), a thiol antioxidant compound. The combination of such mechanisms contributes to prevent membrane lipoperoxidation and cell death. Treatment of HTLA-Chr cells with L-Buthionine-sulfoximine, an inhibitor of GSH biosynthesis, markedly reduces their tumorigenic potential that is instead enhanced by the exposure to N-Acetylcysteine, able to promote GSH synthesis.Collectively, these results demonstrate that GSH and GSH-related responses play a crucial role in the acquisition of MDR and suggest that GSH level monitoring is an efficient strategy to early identify the onset of drug resistance and to control the patient's response to therapy.

Power frequency magnetic field promotes a more malignant phenotype in neuroblastoma cells via redox-related mechanisms

“…In brief, our results indicate that the several MF-induced adaptations may provide a mechanism of resistance to anticancer treatments that acts on a redox basis. The aggressiveness of malignancies is known to correlate to the degree of antioxidant capacity 28 , 48 , and this highlights the importance of our findings.…”

“…Some of us have also reported that human neuroblastoma cells respond to an ELF field by increasing the availability of reduced glutathione (GSH), a powerful endogenous thiol-based free radical scavenger 12 , thus confirming the shared opinion that the interaction between ELF-MF and biosystems may involve the perturbation of the cellular redox balance 19 – 26 . Besides being a critical mediator of chemoresistance in both neuroblastomas and gliomas 27 , 28 , GSH is an essential co-factor for both antioxidant glutathione peroxidase (GPX) and phase II drug-metabolizing glutathione S-transferase (GST) enzymes, with the latter being one of the major determinants of MDR phenotype in tumor cells 29 – 31 . Among the major controllers of the cellular redox environment, sirtuins 1 and 3 (SIRT1 and 3), along with the master regulator erythroid 2-related nuclear transcription factor 2 (NRF2), have been recognized to play crucial roles in the cytoprotective response against oxidative challenge as well as in the onset of drug resistance phenotype, mainly through the transcriptional activation of key antioxidant and detoxifying enzymes, such as GPX, GST, superoxide dismutases (SOD) and catalase (CAT) 32 – 37 .…”

Polyester-Based Dendrimer Nanoparticles Combined with Etoposide Have an Improved Cytotoxic and Pro-Oxidant Effect on Human Neuroblastoma Cells

“…In particular, compared to control cells, ROS levels were increased by 70% and 190% after 48 and 72 h, respectively, while the treatment with free ETO or dendrimer 4 stimulated ROS production by 60% and 80% after 48 and 72 h (Figure 8). To our knowledge, ETO is well known to exert its cytotoxic action by increasing ROS production [91,92], while a pro-oxidant effect of nanoparticles was reported only for polyamidoamine dendrimers (PAMAMs) [93]. Our present data shows that dendrimer 4, which was able per se to increase ROS production, when included in the formation of CPX 5 markedly enhanced the pro-oxidant action of ETO, thus creating conditions of oxidative stress capable of triggering cell death (Figure 7).…”

Metabolic Remodelling: An Accomplice for New Therapeutic Strategies to Fight Lung Cancer

“…This glutamine consumer phenotype may also be linked to cyst(e)ine dependency, as xCT concomitantly exports glutamate and imports cyst(e)ine. Glutamate is a direct product of glutamine degradation and maintaining the glutamine import sustains the import of cyst(e)ine, which has been related to increased therapy resistance in different cancer models [51], mostly due to its role in glutathione synthesis [52][53][54][55], for which glutamine-derived glutamate is also needed.…”

“…Riluzole interferes with glutamate flux and was shown to increase reactive oxygen species (ROS) by suppressing lactate dehydrogenase A (LDHA) and NAD+ [197]. Glutamate stimulates the glutamine import and glutaminolysis, sustaining the import of cyst(e)ine, which has been related to increased therapy resistance in different cancer models [51], mostly due to its role in glutathione synthesis [52,54]. Riluzole interferes with system xCT-cystine/glutamate antiporter, resulting in decreased GSH levels [197].…”