Induction of cellular contractions in the human melanoma cell line SK-mel 28 after muscarinic cholinergic stimulation.

In a previous immunohistochemical study we observed muscarinic acetylcholine receptors in primary and metastatic human melanomas, which were not present in normal skin melanocytes. In the present study we demonstrated the endogenous expression of muscarinic receptors, of choline acetyltransferase and of cholinesterase activity in the human melanoma cell line SK-mel 28. We tested the effect of muscarinic agonists on cellular movements of the melanoma cells in a perfusion chamber by digital video time-lapse microscopy. Within 3 to 10 min after onset of muscarinic perfusion cell body contractions and retraction of cell processes of more than 5 micrometer occurred in about 30% of the melanoma cells. The effect disappeared after addition of atropine. The proportion of reacting cells corresponded to the endogenous expression of muscarinic receptors revealed by immunocytochemistry with the monoclonal antibody M35. The experiments indicate the presence of an autocrine muscarinic cholinergic system in the melanoma cells and demonstrate a direct link between muscarinic receptors and the contractile apparatus. Melanocytes are derived from neural crest cells that express cholinesterase activity and muscarinic receptors during their migratory phase in the embryo. Therefore, re-expression of the muscarinic cholinergic system in tumour cells may be involved in invasive growth.