HMOX1 and neuroblastoma: Along the same line, Rider andco-workers found analogous results in SK-N-SH neuroblastoma cells,which showed no expression of HO-1 without induction.35 In comparison, as little as 1 μM DA resulted in detectablelevels of HO-1, with no change in the constitutive HO-2 expressioneven at high concentrations of DA.