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Widespread expression of parathyroid hormone-related peptide in melanocytic cells
T Kageshita1, T Ishihara, H Tokuo
1Department of Dermatology, Kumamoto University School of Medicine, 1-1 Honjo, Kumamoto 860-0811, Japan. toshiro@kaiju.medic.kumamoto-u.ac.jp
Background:
Parathyroid hormone-related peptide (PTH-rP) was associated with the syndrome of hypercalcaemia of malignancy. An increased serum level of PTH-rP could occur in patients with advanced melanoma.
Objectives:
We examined PTH-rP expression in cultured melanocytic cell lines and in lesions of melanocytic origin for associations with clinicopathological variables of disease progression. We measured the supernatant and cell lysate level of PTH-rP in cultured melanoma cells to clarify whether melanoma cells secrete PTH-rP.
Methods:
PTH-rP expression was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) in cultured melanocytic cell lines and by immunoperoxidase staining in 18 melanocytic naevi, 40 primary melanoma and 19 metastatic melanoma lesions. The supernatant level of PTH-rP was measured with an immunoradiometric assay.
Results:
RT-PCR products of PTH-rP mRNA were detected in six of eight melanoma cell lines; however, neither naevus cells nor melanocytes showed positive products. On the other hand, immunohistochemical analysis showed that PTH-rP was widely expressed both in benign and malignant melanocytic lesions. In addition, PTH-rP expression was not associated with any clinicopathological variables. Cell lysate but not the supernatant of melanoma cells showed high PTH-rP levels.
Conclusions:
These results suggest that PTH-rP was widely expressed in melanocytic cells; however, the cells did not secrete PTH-rP.