Autocrine and paracrine regulation by cytokines and growth factors in melanoma

Tumour development and progression involves the expression of oncogenes and inactivation of tumour suppressor genes, leading to the appearance of mult iple malignant characteristics. Malignant melanoma cells express different growth factors and cytokines and their receptors in respective stages of tu mour progression, which by autocrine and paracrine effects enable them to g row autonomously and confer competence to metastasis. Autocrine growth fact ors (bFGF, MGSA/GRO, IL-8 and sometimes IL-6, PDGF-A, IL-10) produced by me lanoma cells stimulate proliferation of the producing cell itself, while pa racrine growth factors (for example PDGF, EGF, TGF-beta, IL-1, GM-CSF, IGF- I, NGF, VEGF) modulate the microenvironment to the benefit of tumour growth and invasion. Paracrine effects include angiogenesis, stroma formation, mo dulation of host immune response, activation of proteolytic enzymes, adhesi on or motility and metastasis formation. Some growth factors have inhibitor y effects on melanocytes and early lesions (IL-1, IL-6, TGF-beta, OSM, TNF and IFN) but not on advanced stage melanomas, and in some cases they switch to autocrine stimulator (IL-6, TGF-beta). Understanding the involvement of different growth factors and cytokines in the molecular mechanism of melan oma progression will help to provide an insight into new future therapeutic approaches for melanoma. (C) 2000 Academic Press.