Previous studies with the human neuroblastoma cell lines SK-N-BE, CHP-134, SK-N-SH, LA-N-1 and LA-N-5 using standard RT-PCR have revealed marked induction of HOXD1 and HOXD8 following RA treatment in all of the neuroblastoma cell lines, as well as low levels of HOXD4 and HOXD9 induction in some neuroblastoma cell lines [14], [15]. Here, HOXD4 is linked to neuroblastoma.