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c-Met Is a Potentially New Therapeutic Target for Treatment of Human Melanoma

Authors' Affiliation: Departments of Hematology/Oncology and Pathology, University of Chicago Medical Center, Chicago, Illinois

Requests for reprints: Ravi Salgia, Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, 5841 S. Maryland Avenue, MC 2115, Chicago, IL 60607. Phone: 773-702-4399; Fax: 773-784-1698; E-mail: rsalgia{at}medicine.bsd.uchicago.edu.

Purpose: c-Met is a receptor tyrosine kinase involved in cell growth, invasion, metastases, and angiogenesis. In this study, we investigated the role of c-Met in melanoma biology using a novel small-molecule tyrosine kinase inhibitor SU11274 and small interfering (si) RNA against the receptor.

Experimental Design: The effects of SU11274 and c-Met siRNA were studied on proliferation, apoptosis, differentiation, reactive oxygen species, and intracellular signaling. c-Met mutations were examined, and the expression of c-Met and activated c-Met was studied in nevi, primary, and metastatic melanoma.

Results: c-Met was expressed in 6:7 melanoma cell lines by immunoblotting. SU11274 inhibited cell growth in all melanoma cell lines by 85% to 98% with an IC₅₀ between 1 and 2.5 µmol/L and caused apoptosis (12-58%) in five out of six cell lines. siRNA against c-Met inhibited proliferation of melanoma cells by 60%. This is the first study that shows that SU11274 and siRNA induced microphthalmia-associated transcription factor (MITF) and several other melanoma differentiation proteins and a morphologically differentiated phenotype. SU11274 also inhibited reactive oxygen species formation and phosphorylation of c-Met receptor, AKT and S-6 kinase by the hepatocyte growth factor. A new missense c-Met mutation N948S was identified in cell lines and R988C in tumor tissue in the juxtamembrane domain of c-Met. It was found that c-Met was expressed in 88% of melanomas and 15% of nevi, and that c-Met (pY1003) was activated in 21% of human melanomas.

Conclusion: These results support the role of c-Met in proliferation, apoptosis, differentiation, and tumor progression of melanoma. SU11274 could be used in the therapeutic inhibition of melanoma.

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				R. Salgia c-Met Receptor Tyrosine Kinase as a Therapeutic Target in Cancer ASCO Educational Book, January 1, 2008; 2008(1): 113 - 118. [Abstract] [Full Text] [PDF]