A Cross-Talk between TrkB and Ret Tyrosine Kinases Receptors Mediates Neuroblastoma Cells Differentiation

Abstract

Understanding the interplay between intracellular signals initiated by multiple receptor tyrosine kinases (RTKs) to give the final cell phenotype is a major pharmacological challenge. Retinoic acid (RA)-treatment of neuroblastoma (NB) cells implicates activation of Ret and TrkB RTKs as critical step to induce cell differentiation. By studying the signaling interplay between TrkB and Ret as paradigmatic example, here we demonstrate the existence of a cross-talk mechanism between the two unrelated receptors that is needed to induce the cell differentiation. Indeed, we show that TrkB receptor promotes Ret phosphorylation by a mechanism that does not require GDNF. This reveals to be a key mechanism, since blocking either TrkB or Ret by small interfering RNA causes a failure in NB biochemical and morphological differentiation. Our results provide the first evidence that a functional transactivation between distinct tyrosine kinases receptors is required for an important physiological process.

Complexity of Receptor Tyrosine Kinase Signal Processing

“…Moreover, TrkB knockdown prevents cell differentiation (Esposito et al 2008). "Reverse" cross talk, in which TrkA and TrkB receptors induce activation of Ret, was also observed (TsuiPierchala et al 2002;Esposito et al 2008). Although in this case positive regulation of Ret In a recent study (Gujral et al 2012), breast cancer samples were subjected to "reversephase" protein microarrays (Sevecka and MacBeath 2006) and phosphorylation or total protein levels of multiple signaling molecules were tested.…”

“…Receptor cross activation can also be mediated via transcriptional induction of an RTK (or its ligands) by another RTK (Jones et al 2006;Esposito et al 2008;Gujral et al 2012;Velpula et al 2012). For instance, in neuroblastoma-derived cell lines retinoic acid induces activation of the RTK Ret, leading to cell differentiation, as indicated by morphological changes and expression of several differentiation markers.…”

“…Several studies suggested that TrkB (another RTK and indicator of poor prognosis for neuroblastoma tumors) can link retinoic acid stimulation and the phenotype change. Ret activation induces expression of both TrkB and its primary ligand brain-derived neurotrophic factor (BDNF) (Kaplan et al 1993;Esposito et al 2008). Moreover, TrkB knockdown prevents cell differentiation (Esposito et al 2008).…”

“…Ret activation induces expression of both TrkB and its primary ligand brain-derived neurotrophic factor (BDNF) (Kaplan et al 1993;Esposito et al 2008). Moreover, TrkB knockdown prevents cell differentiation (Esposito et al 2008). "Reverse" cross talk, in which TrkA and TrkB receptors induce activation of Ret, was also observed (TsuiPierchala et al 2002;Esposito et al 2008).…”

Interplay Between Protein Kinase C Isoforms Alpha and Epsilon, Neurofibromin, and the Ras/MAPK Pathway in Neuroblastoma Differentiation

“…Neurofibromin-deficient cells continue to proliferate in the presence of low concentrations of RA, bypassing check points for growth arrest and induction of differentiation, and exhibiting reduced expression of RA-target genes, Ret included (Holzel et al, 2010). Expression of Ret, the GDNF receptor, is very important for differentiation of NB cells (Peterson & Bogenmann, 2004;Esposito et al, 2008), especially through its action on upregulation of TrkA, a powerful and favorable prognostic marker in NB tumors (Edsjo et al, 2007;Brodeur, 2003). The need for prognostic markers and therapeutic targets has strongly driven research on the signalling mechanisms that regulate RA-induced NB differentiation.…”