PHOX2A and neuroblastoma: We investigated the effects of ATRA on the expression of PHOX2A, a candidate tumour suppressor gene [14], using the undifferentiated SK-N-BE(2)C human NB cell line as a model, and found that they were apparently opposite: it initially acted as a positive regulator of gene expression, but later triggered a process that culminated in the complete disappearance of the transcription factor.