PHOX2B and neuroblastoma: As the expression of PHOX2B precedes that of PHOX2A during development, and in vitro experiments have shown that the forced over-expression of PHOX2B regulates PHOX2A[5], [6], it is possible to speculate that PHOX2A up-regulation may be due to a high level of PHOX2B expression, because silencing PHOX2B in NB cell lines leads to the down-regulation of PHOX2A[22].