RAGE is a multiligand receptor able to bind advanced glycation end-products (AGEs), amphoterin, calgranulins, and amyloid-beta peptides, identified in many tissues and cells, including neurons. RAGE stimulation induces the generation of reactive oxygen species (ROS) mainly through the activity of NADPH oxidases. In neuronal cells, RAGE-induced ROS generation is able to favor cell survival and differentiation or to induce death through the imbalance of redox state. The dual nature of RAGE signaling in neurons depends not only on the intensity of RAGE activation but also on the ability of RAGE-bearing cells to adapt to ROS generation. In this review we highlight these aspects of RAGE signaling regulation in neuronal cells.

The activation of Nrf2 has been demonstrated to play a crucial role in cancer cell resistance to different anticancer therapies. The inhibition of proteasome activity has been proposed as a chemosensitizing therapy but the activation of Nrf2 could reduce its efficacy. Using the highly chemoresistant neuroblastoma cells HTLA-230, here we show that the strong reduction in proteasome activity, obtained by using low concentration of bortezomib (BTZ, 2.5 nM), fails in reducing cell viability. BTZ treatment favours the binding of Nrf2 to the ARE sequences in the promoter regions of target genes such as heme oxygenase 1 (HO-1), the modulatory subunit of γ-glutamylcysteine ligase (GCLM) and the transporter for cysteine (x-CT), enabling their transcription. GSH level is also increased after BTZ treatment. The up-regulation of Nrf2 target genes is responsible for cell resistance since HO-1 silencing and GSH depletion synergistically decrease BTZ-treated cell viability. Moreover, cell exposure to all-trans-Retinoic acid (ATRA, 3 μM) reduces the binding of Nrf2 to the ARE sequences, decreases HO-1 induction and lowers GSH level increasing the efficacy of bortezomib. These data suggest the role of Nrf2, HO-1 and GSH as molecular targets to improve the efficacy of low doses of bortezomib in the treatment of malignant neuroblastoma.

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Neuroblastoma (NB), the second most common pediatric tumor, is characterized by biological and clinical heterogeneity. Considering the limited success of chemotherapy, the aim of our study is to identify and target key molecular pathways associated with NB chemoresistance. In this context, we analyzed the main survival and death pathways triggered by etoposide, a commonly used chemotherapeutic agent, in HTLA‐230, a MYCN‐amplified NB cell line isolated from a high‐risk patient. Etoposide induced a concentration‐dependent reduction of cell viability and, at very high doses, totally counteracted cell tumorigenicity and neurosphere formation. In addition, etoposide activated p38 Mitogen‐activated protein Kinase (MAPK), AKT and c‐Jun N‐terminal kinase. Therefore, the treatment with etoposide combined with SB203580, an inhibitor of p38MAPK activity, decreased cell viability and tumorigenicity, counteracted neurosphere generation and slowed down the cell migration and invasion. In this context, the expression of COX‐2, ICAM‐1 and CXCR4 was down regulated, the formation of capillary‐like structures was prevented, by generating a phenotype inadequate for tumor development.. Collectively, our results suggest that p38MAPK inhibitors, in combination with standard chemotherapy, could be a novel strategy to counteract NB resistance and relapse.Grants: PRIN 2009M8FKBB_002; Genoa University.

Depletion of glutathione (GSH) by buthionine sulfoximine (BSO) has been reported to be toxic against some cancer cells and to sensitize many tumours including neuroblastoma (NB) to anticancer drugs. The balance between the production rate of reactive oxygen species (ROS) and the function of GSH affects the intracellular reduction-oxidation status, which is crucial for the regulation of several cellular physiological functions. To assess the role of glutathione in neuroblastoma therapy, the effect of sublethal concentrations of BSO was studied in a panel of neuroblastoma cell lines characterized by different MYCN status. We found that GSH depletion per se not accompanied by ROS overproduction, does not affect cell survival, and is not genotoxic but induces HO-1 expression in GI-ME-N cell line, a representative example of MYCN non-amplified NB cells, having the highest basal levels of GSH among the tested NB lines. These observations might open a novel therapeutic window based on the possibility of modulating the cellular 'activity' of GSH.