Targeting Neuroblastoma Stem Cells with Retinoic Acid and Proteasome Inhibitor

Abstract

BackgroundNeuroblastma cell lines contain a side-population of cells which express stemness markers. These stem-like cells may represent the potential underlying mechanism for resistance to conventional therapy and recurrence of neuroblastoma in patients.Methodology/Principal FindingsTo develop novel strategies for targeting the side-population of neurobastomas, we analyzed the effects of 13-cis-retinoic acid (RA) combined with the proteasome inhibitor MG132. The short-term action of the treatment was compared with effects after a 5-day recovery period during which both chemicals were withdrawn. RA induced growth arrest and differentiation of SH-SY5Y and SK-N-BE(2) neuroblastoma cell lines. Inhibition of the proteasome caused apoptosis in both cell lines, thus, revealing the critical role of this pathway in the regulated degradation of proteins involved in neuroblastoma proliferation and survival. The combination of RA with MG132 induced apoptosis in a dose-dependent manner, in addition to promoting G2/M arrest in treated cultures. Interestingly, expression of stem cell markers such as Nestin, Sox2, and Oct4 were reduced after the recovery period of combined treatment as compared with untreated cells or treated cells with either compound alone. Consistent with this, neurosphere formation was significantly impaired by the combined treatment of RA and MG132.ConclusionsGiven that stem-like cells are associated with resistant to conventional therapy and are thought to be responsible for relapse, our results suggest that dual therapy of RA and proteasome inhibitor might be beneficial for targeting the side-population of cells associated residual disease in high-risk neuroblastoma.

RA Differentiation Enhances Dopaminergic Features, Changes Redox Parameters, and Increases Dopamine Transporter Dependency in 6-Hydroxydopamine-Induced Neurotoxicity in SH-SY5Y Cells

“…Previous studies have demonstrated that RAinduced differentiation can cause cell cycle arrest either in G1/G0 phase or in G2/M phase and a decrease in proliferation rates, which leads to terminal differentiation of neuroblastoma cells (Qiao et al 2012;Hämmerle et al 2013). …”

Retinoic acid signaling and neuronal differentiation

“…Neuroblastoma cell lines were commonly used to demonstrate the differentiation and anti-tumorigenic potential of RA. LA-N-1/2/5, CHP-134, KA [210,211], SH-SY5Y [212], Neuro-2a [213], SK-N-BE2 [214], IMR-32 [215], SMS-KCNR [216], and D283 [217] can all be differentiated by retinoids into cells expressing neuronal markers and exhibiting neurite morphology. Although many cell lines can be differentiated in response to RA, the clinical response to RA treatment is variable.…”

Roles of PPAR transcription factors in the energetic metabolic switch occurring during adult neurogenesis

“…In order to identify the metabolic events occurring during neuronal precursor differentiation, the glucose and lipid metabolism was followed in a recognized model of neuronal differentiation in vitro, the SH-SY5Y neuroblastoma cell line, which presents, according to literature, a subpopulation of stemlike cells expressing nestin and SOX2. 26 In the same model, considering its role in glucose and lipid metabolism and its involvement in NSCs maintenance, the PPARg isotype was specifically investigated. Moreover, in order to gain more insight into PPARg distribution also in situ, and considering the difficulties to obtain adult human normal brain specimens, the immunolocalization of PPARg in adult mouse brain SVZ was also studied.…”