c-Kit-dependent growth of uveal melanoma cells : a potential therapeutic target?

• PURPOSE: This study was conducted to investigate the expression and functional impact of the proto-oncogene c-kit in uveal melanoma. METHODS: Based on immunohistochemical (IHC) study of paraffin-embedded specimens from 134 uveal melanomas and Western blot analysis on eight fresh-frozen samples the expression of c-kit in uveal melanoma was studied. Furthermore, the phosphorylation of c-kit and the impact of the tyrosine kinase inhibitor STI571 was examined in the three uveal melanoma cell lines OCM-1, OCM-3, and 92-1. RESULTS: Eighty-four of 134 paraffin-embedded samples and six of eight fresh-frozen samples expressed c-kit. c-Kit was strongly expressed and tyrosine phosphorylated in cultured uveal melanoma cells compared with cutaneous melanoma cells. Moreover, in contrast to cutaneous melanoma cell lines c-kit maintained a high phosphorylation level in serum-depleted uveal melanoma cells. No activation-related mutations in exon 11 of the KIT gene were found. On the contrary, expression of the stem cell growth factor (c-kit ligand) was detected in all three uveal melanoma cell lines, suggesting the presence of autocrine (paracrine) stimulation pathways. Treatment of uveal melanoma cell lines with STI571, which blocks c-kit autophosphorylation, resulted in cell death. The IC(50) of the inhibitory effects on c-kit phosphorylation and cell proliferation was of equal size and less than 2.5 microM. CONCLUSIONS: The results confirm that c-kit is vastly expressed in uveal melanoma, suggest that the c-kit molecular pathway may be important in uveal melanoma growth, and point to its use as a target for therapy with STI571.

Keyword

Adult

Aged

Aged; 80 and over

Blotting; Western

Cell Division

Female

Humans

Immunoenzyme Techniques

Male

Melanoma/*metabolism/*pathology

Middle Aged

Paraffin Embedding

Phosphorylation/drug effects

Polymerase Chain Reaction

Proto-Oncogene Proteins c-kit/genetics/*metabolism

Pyrimidines/pharmacology

RNA; Messenger/metabolism

Skin Neoplasms/metabolism/pathology

Tumor Cells; Cultured

Tyrosine/metabolism

Uveal Neoplasms/*metabolism/*pathology

MEDICINE

MEDICIN

Publication and Content Type

ref (subject category)

art (subject category)