Immunodetection of gastrin-releasing peptide in malignant melanoma cells

Gastrin-releasing peptide (GRP), the mammalian counterpart of bombesin, was first identified in the nervous system of the gastrointestinal tract. Litt le is known about its distribution in the human skin or about its function in certain diseases such as malignant melanoma. Recently functional GRP rec eptors have been found on human melanoma cell lines. We therefore investiga ted, using immunohistochemistry, whether human melanoma cells express GRP a nd whether there is a significant change in its distribution among the diff erent clinical types of melanoma and a connection to histopathological feat ures such as growth phase, type of malignant cells, Breslow thickness and C lark level of invasion. We demonstrated the existence of GRP in all clinico pathological types of melanoma; a predilection for quantitatively increased GRP immunostaining was noticed in nodular melanomas (P = 0.007). As well a s this, we observed a restriction of GRP expression at a specific level of invasion, i.e. within the reticular dermis (Clark IV) (P = 0.032). GRP immu noreactivity was found to be associated with an increased amount of melanin pigment in malignant cells (P = 0.054). The presence of GRP in malignant m elanocytes, along with its association with the various histopathological f eatures, suggests that GRP may play a role in the pathophysiology of this t ype of cutaneous tumour. (C) 2000 Lippincott Williams & Wilkins.