The Phox2B homeobox gene is mutated in sporadic neuroblastomas

Neuroblastomas are embryonal tumours of the sympatho-adrenal lineage with a clinical course ranging from spontaneous regression to fatal progression. The Phox2B homeobox transcription factor functions in the differentiation of the sympatho-adrenal lineage. Targets of Phox2B are, for example, genes of the (nor)adrenalin synthesis route, like Dopamine Beta Hydroxylase (DBH). Congenital Central Hypoventilation Syndrome was recently found to result from Phox2B mutations and two such patients in addition developed neuroblastoma. A germline mutation in Phox2B was identified in a family with hereditary neuroblastoma. Here, we report the first analysis of Phox2B in a series of 237 sporadic neuroblastomas and 22 cell lines. Six frameshift mutations were found in exons 2 and 3; including one in cell line SK-N-SH. Two patients showed de novo constitutional mutations. One of them was diagnosed with Haddad syndrome. All analysed cases expressed the mutated and wild-type Phox2B alleles. Ectopic expression of TrkA, the Nerve Growth Factor receptor, strongly downregulated Phox2B and DBH expression in cell line SH-SY5Y. However, TrkA and Phox2B showed a positive correlation in a panel of 66 neuroblastoma tumours. Although Phox2B mutations are infrequent (2.3%), they implicate a role for the Phox2B pathway in oncogenesis.