The TrkAIII Oncoprotein Inhibits Mitochondrial Free Radical ROS-Induced Death of SH-SY5Y Neuroblastoma Cells by Augmenting SOD2 Expression and Activity at the Mitochondria, within the Context of a Tumour Stem Cell-like Phenotype

Abstract

The developmental and stress-regulated alternative TrkAIII splice variant of the NGF receptor TrkA is expressed by advanced stage human neuroblastomas (NBs), correlates with worse outcome in high TrkA expressing unfavourable tumours and exhibits oncogenic activity in NB models. In the present study, we report that constitutive TrkAIII expression in human SH-SY5Y NB cells inhibits Rotenone, Paraquat and LY83583-induced mitochondrial free radical reactive oxygen species (ROS)-mediated death by stimulating SOD2 expression, increasing mitochondrial SOD2 activity and attenuating mitochondrial free radical ROS production, in association with increased mitochondrial capacity to produce H2O2, within the context of a more tumour stem cell-like phenotype. This effect can be reversed by the specific TrkA tyrosine kinase inhibitor GW441756, by the multi-kinase TrkA inhibitors K252a, CEP-701 and Gö6976, which inhibit SOD2 expression, and by siRNA knockdown of SOD2 expression, which restores the sensitivity of TrkAIII expressing SH-SY5Y cells to Rotenone, Paraquat and LY83583-induced mitochondrial free radical ROS production and ROS-mediated death. The data implicate the novel TrkAIII/SOD2 axis in promoting NB resistance to mitochondrial free radical-mediated death and staminality, and suggest that the combined use of TrkAIII and/or SOD2 inhibitors together with agents that induce mitochondrial free radical ROS-mediated death could provide a therapeutic advantage that may also target the stem cell niche in high TrkA expressing unfavourable NB.

Mitochondrial aerobic respiration is activated during hair follicle stem cell differentiation, and its dysfunction retards hair regeneration

“…3B ), but SOD1 was not (data not shown). Elevated SOD2 expression during differentiation of iPSCs and neuroblastoma cells was discovered in previous studies for sustaining redox homeostasis and preventing ROS-induced cell death ( Armstrong et al, 2010 ; Case et al, 2013 ; Ruggeri et al, 2014 ). Interestingly, enhanced mitochondrial activity upon HFSCs differentiation is age-independent ( Fig.…”

Enhancement of SOX-2 expression and ROS accumulation by culture of A172 glioblastoma cells under non-adherent culture conditions

“…The higher levels seemed to be more dependent on serum deprivation than on the presence of a non-adherent surface. ROS is a critical factor for maintaining stemness by the expression of SOX-2 (43), and SOD2 promotes migration and invasion and protects cells from ROS-mediated cell death (44)(45)(46). Therefore, we hypothesized that a ROS scavenger would block SOX-2 induction under our cell culture conditions.…”

Retrograde TrkAIII transport from ERGIC to ER: a re-localisation mechanism for oncogenic activity

“…This highlights the importance of intracellular TrkAIII re-localisation for oncogenic activity, identifies the ERGIC/COPI compartment as a preferential site for spontaneous TrkAIII activation and provides an explanation for how TrkAIII, compromised by the omission of the D4 IGC1 spontaneous activation-prevention domain, is able to overcome the threshold for spontaneous activation. The subsequent and altered oncogenic signalling through PI3K/Akt but not Ras/MAPK results in increased survival, a pattern of malignant gene expression, increased genetic instability and promotion of stem cell-like behaviour rather than differentiation [ 1 , 3 , 4 , 6 , 35 ], which together not only promote tumour progression but may also be involved in tumour initiation. TrkA tyrosine kinase inhibitors abrogate this mechanism by promoting the anterograde transport of inactivated TrkAIII to the GN, resulting in GN-associated TrkAIII maturation to a 120kDa form that is degraded at the proteasome, reducing both intracellular accumulation and oncogenic activity of the TrkAIII oncoprotein.…”