DBH and neuroblastoma: We investigated the direct effect of IH on the gene expression(s) of catecholamine-synthesizing enzymes in neuroblastoma cells, and found significant increases in the mRNA levels of dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in response to IH treatment via the down-regulation of microRNA (miR)-375.