Inhibitors of the RET kinase and the RAS-MAPK pathway have previously been shown to be effective against neuroblastoma, suggesting that combined inhibition may have increased efficacy.
We demonstrate that ETV5 is regulated both at the protein and mRNA levels upon ALK activation or inhibition in neuroblastoma cell lines and that this regulation precedes RET modulation.
Consistent with this result, ZAR1-depleted NB cells showed well-differentiated phenotypes with elongated neurites and upregulated expression of TRKA and RET, which are markers for differentiated NB.
In summary, our study suggests that RET is a potential therapeutic target in NB, and that using a novel RET inhibitor, like regorafenib, should be investigated as a therapeutic treatment option for children with NB.
Altogether, our findings demonstrate the critical role of activated ALK in SNS development and pathogenesis and identify RET as a therapeutic target in ALK mutated neuroblastoma.
We developed a RET mini-gene reporter system, and showed that MCS+9.7 enhanced HOXB5 trans-activation from RET promoter in human neuroblastoma SK-N-SH cells and in chick embryos.
NB-39-nu neuroblastoma cells show high expression and elevated tyrosine phosphorylation of RET, although short interfering RNA against RET (RET siRNA) did not significantly inhibit cell proliferation or suppression of basal levels of phosphorylation of extracellular regulated kinase (ERK)1/2 or protein kinase B (AKT).
Transfection experiments using human neuroblastoma cells showed that the mutant RET, unlike the wild-type receptor, is constitutively phosphorylated in the absence of ligand, and thus resembles other previously characterized MEN 2A mutations.
Taken together, these results indicate that GDNF up-regulates the expression of the TH gene by promoting the transcription of the TH gene and the stability of TH mRNA with the Ret receptor dependency in some neuroblastoma cell lines.
In the present work, we have studied the ability of GDNF proteins, each bearing one of the reported mutations, to activate RET by performing a functional test in cultured neuroblastoma cells.
In the present study, we generated a novel monoclonal antibody (NBL-1) to RET, a receptor tyrosine kinase expressed in both neuroblastoma cells and cells present in substantia nigra, a responsive locus of Parkinson's disease.
Taken together these data suggest that abnormalities of the RET signalling pathway, rather than oncogenic, MEN2-type RET activation by mutation, may play a role in neuroblastoma tumorigenesis.
We have also demonstrated by the in vitro premethylation of a RET promoter-chloramphenicol acetyltransferase (CAT) gene construct and transient transfection experiments into neuroblastoma cells that the transcriptional activity of the RET promoter is decreased by HpaII (5'-CCGG-3') methylation and abolished by SssI (5'-CG-3') methylation.
In addition, there was strong evidence against linkage to two Hirschsprung disease susceptibility genes (RET and EDNRB), a condition that can cosegregate with neuroblastoma as in one of the kindreds tested here.
To better understand the role of the activated RET oncogene in neural crest cells, we transfected two adherent human neuroblastoma tumor cell lines with oncogenic MEN2 mutant RET cDNAs.
RET expression is enhanced in vitro by several differentiating agents, including retinoic acid (RA), which up-regulates RET expression in neuroblastoma cell lines.
Furthermore, there is strong evidence against linkage to two Hirschsprung disease (a condition that can cosegregate with neuroblastoma) susceptibility genes, RET and EDNRB.