Correlation of MET and PD-L1 expression in malignant melanoma
Abstract Background: The proto-oncogene MET, the hepatocyte growth factor (HGF) receptor, is a transmembrane receptor tyrosine kinase (RTK) with a prominent role in tumor metastasis and resistance to anti-cancer therapies. Melanoma demonstrates relatively frequent MET aberrations, including MET gene amplification. Concurrently, PD-L1, with its ability to evade anti-tumor immune responses, has emerged as a prominent therapeutic target in melanoma and other malignancies and its expression is used as a predictive biomarker of response to immunotherapy. Methods: We performed immunohistochemistry analysis of MET and PD-L1 in 18 human melanoma cell lines derived from both primary and metastatic lesions; we then performed the same analysis in a human melanoma tissue microarray (TMA) containing 100 melanocytic lesions, including 42 cutaneous malignant melanomas, 20 mucosal melanoma, 21 metastatic melanomas and 17 benign melanocytic nevi as controls. After color deconvolution, TMA cores were identified and segmented to isolate staining and calculate the percentage of positive cells in each core. Results: Overall, MET expression was higher in metastatic lesions and it was higher in tumors with increased PD-L1 expression. Moreover, a positive correlation between MET and PD-L1 expression was found in metastatic melanoma. Conclusions: These data suggest that testing for expression of these markers should be conducted in patients with melanoma with metastatic disease and selective therapies targeting these proteins should be considered for advanced disease.