Parathyroid hormone-related protein, chromogranin A, and calcitonin gene products in the neuroendocrine skin carcinoma cell lines MKL1 and MKL2.

We studied the production of parathyroid-hormone-related protein, chromogranin A, calcitonin and calcitonin-gene-related peptide in the neuroendocrine skin cell line, MKL1, and a subsequently derived cell line designated MKL2. Both cell lines had cytological, histological and electron-microscopic features typical of neuroendocrine differentiation. Immunohistology and radioimmunoassay studies demonstrated the presence of parathyroid-hormone-related protein, chromogranin A, calcitonin-gene-related peptide, and calcitonin in the MKL2 cell line and the last three substances in both cell lines. The secretion of each of the first three substances was regulated by phorbol in the MKL2 cells. Additional immunohistochemical studies demonstrated the variable expression of bombesin, substance P, and vasoactive intestinal polypeptide in MKL2 cells, and the expression of synaptophysin in both MKL1 and MKL2 cells. These studies demonstrate the neuroendocrine characteristics of the MKL cell lines and provide a novel model for studies of the production and interactions of several neuroendocrine proteins and peptides by human skin cells.