Melanoma cells constitutively produce various
cytokines as well as
growth factors and express their corresponding receptors. Exogenous
histamine is known to be a
growth factor for some tumours while in other cases
histamine inhibits tumour growth, and acts on
G protein-coupled H1 and H2
histamine receptors. In previous studies we have detected the expression of the
l-histidine decarboxylase (HDC) gene and the presence of HDC
protein in human
melanoma cell lines. In the present study, the activities of the
histamine-forming
enzyme HDC and of the degrading
enzymes diamine oxidase (DAO) and
histamine N-methyltransferase (HNMT) were measured in primary (WM35 and WM983) and metastatic (M1 and HT168) human
melanoma cell lines. HDC activity was found in WM35 and WM983 cell lines, while detectable HNMT activity was measured in WM983, M1 and HT168 lines. In contrast, DAO showed very low activity in
melanoma cell lines.
Melanoma cells release a detectable amount of
histamine into the medium without external stimuli. These findings support the possibility of autonomous
histamine metabolism in
melanoma cells. Our results suggest that not only exogenous
histamine but also
histamine produced and released by the
melanoma cells and acting as an autocrine and paracrine factor may influence cell proliferation and modulate the in situ immune response of the host.