Jongmin Sim1, You Jeong Heo2, Hyunsik Bae1, Hyeong Chan Shin1, Binnari Kim1, Junhun Cho1, Seung Tae Kim2, Jeeyun Lee2, Won Ki Kang2, Kyoung-Mee Kim3. 1. Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. 2. Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. 3. Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. Electronic address: kkmkys@skku.edu.
Abstract
BACKGROUND: MET is a tyrosine kinase receptor for the hepatocyte growth factor, and its overexpression is a poor prognostic factor in gastric carcinomas. Programmed death-ligand 1 (PD-L1) is an important biomarker of immunotherapy and is frequently positive in microsatellite instability-high (MSI-H) gastric carcinomas. In lung cancers, MET activation up-regulates PD-L1 expression. In this study, we investigated expression of MET and PD-L1 in MSI-H gastric carcinoma and the effects on prognosis. METHODS: MET and PD-L1 (SP142) immunohistochemistry was performed in 73 gastric carcinomas with MSI-H. In cases with MET overexpression, we performed fluorescent in situ hybridization (FISH). PD-L1 expression was calculated from both tumor cells (2+ and 3+ in > 10% of tumor cells was defined as PD-L1TC+) and immune cells (positive in >5% immune cells was PD-L1IC+), and also used a combined positive score (CPS; number of PD-L1 staining cells relative to all viable tumor cells; > 1 was PD-L1+). RESULTS: In 73 MSI-H gastric carcinomas, MET overexpression was observed in 11 cases (15.1%). In all 11 cases with MET overexpression,MET amplification was not found. MET overexpression was not related to any of clinico-pathological variables and PD-L1 expression. However, the PD-L1 CPS tended to be higher in tumors that were MET positive. Although MET overexpression alone was not a prognostic indicator, combined MET overexpression/PD-L1 predictive models showed that patients with MET+/PD-L1+ showed the best prognosis for overall survival as compared to other groups. CONCLUSION: MET overexpression was observed in 15% of MSI-H gastric carcinomas and was associated with high level expression of PD-L1.
BACKGROUND: MET is a tyrosine kinase receptor for the hepatocyte growth factor, and its overexpression is a poor prognostic factor in gastric carcinomas. Programmed death-ligand 1 (PD-L1) is an important biomarker of immunotherapy and is frequently positive in microsatellite instability-high (MSI-H) gastric carcinomas. In lung cancers, MET activation up-regulates PD-L1 expression. In this study, we investigated expression of MET and PD-L1 in MSI-H gastric carcinoma and the effects on prognosis. METHODS: MET and PD-L1 (SP142) immunohistochemistry was performed in 73 gastric carcinomas with MSI-H. In cases with MET overexpression, we performed fluorescent in situ hybridization (FISH). PD-L1 expression was calculated from both tumor cells (2+ and 3+ in > 10% of tumor cells was defined as PD-L1TC+) and immune cells (positive in >5% immune cells was PD-L1IC+), and also used a combined positive score (CPS; number of PD-L1 staining cells relative to all viable tumor cells; > 1 was PD-L1+). RESULTS: In 73 MSI-H gastric carcinomas, MET overexpression was observed in 11 cases (15.1%). In all 11 cases with MET overexpression,MET amplification was not found. MET overexpression was not related to any of clinico-pathological variables and PD-L1 expression. However, the PD-L1 CPS tended to be higher in tumors that were MET positive. Although MET overexpression alone was not a prognostic indicator, combined MET overexpression/PD-L1 predictive models showed that patients with MET+/PD-L1+ showed the best prognosis for overall survival as compared to other groups. CONCLUSION: MET overexpression was observed in 15% of MSI-H gastric carcinomas and was associated with high level expression of PD-L1.