Histidine decarboxylase expression in human melanoma

Histamine has been implicated as one of the mediators involved in regulatio n of proliferation in both normal and neoplastic tissues. Histidine decarbo xylase, the only enzyme that catalyzes the formation of histamine from L-hi stidine, is an essential regulator of histamine levels. In this study, we i nvestigated the gene and protein expression of histidine decarboxylase in m elanoma. Reverse transcriptase polymerase chain reaction and in situ hybrid ization studies of WM-35, WM-983/B, HT-168, and M1 human melanoma cell line s both resulted in positive signals for histidine decarboxylase messenger R NA. A polyclonal chicken antibody was developed against human histidine dec arboxylase and protein expression was confirmed by western blot analysis of the cell lysates, revealing a predominant immunoreactive band at approxima tely 54 kDa corresponding to monomeric histidine decarboxylase. Protein exp ression of histidine decarboxylase was also shown by flow cytometric analys is and strong punctate cytoplasmic staining of melanoma cell lines. Moreove r, both primary and metastatic human melanoma tissues were brightly stained for histidine decarboxylase. When compared with the very weak or no reacti ons on cultivated human melanocytes both western blot and immunohistochemic al studies showed much stronger histidine decarboxylase expression in melan oma cells. These findings suggest that expression of histidine decarboxylas e is elevated in human melanoma.