A Wnt-BMP4 signalling axis induces MSX and NOTCH proteins and promotes growth suppression and differentiation in neuroblastoma
The Wnt and bone morphogenetic protein (BMP) signalling pathways are known to be crucial in the development of neural crest lineages, including the sympathetic nervous system. Surprisingly, their role in paediatric neuroblastoma, the prototypic tumour arising from this lineage, remains relatively uncharacterised. We previously demonstrated that Wnt/{beta}-catenin signalling can have cell-type specific effects on neuroblastoma phenotypes, including growth inhibition and differentiation, and that BMP4 mRNA and protein were induced by Wnt3a/Rspo2. In this study, we characterise the phenotypic effects of BMP4 on neuroblastoma cells, demonstrating convergent induction of MSX homeobox transcription factors by Wnt and BMP4 signalling and BMP4-induced growth suppression and differentiation. Immunohistochemical analysis of BMP4 expression in primary neuroblastomas confirms a striking absence of BMP4 in poorly differentiated tumours, in contrast to high expression in ganglion cells. These results are consistent with a tumour suppressive role for BMP4 in neuroblastoma. RNA sequencing following BMP4 treatment revealed induction of Notch signalling, verified by increases of Notch3 and Hes1 proteins. Together, our data demonstrate for the first time Wnt-BMP-Notch signalling crosstalk associated with growth suppression of neuroblastoma.