Programmed cell death-ligand 1 expression predicts survival in patients with gastric carcinoma with microsatellite instability

// Junhun Cho 1 , Jeeyun Lee 2 , Heejin Bang 3 , Seung Tae Kim 2 , Se Hoon Park 2 , Ji Yeong An 4 , Min Gew Choi 4 , Joon Ho Lee 4 , Tae Sung Sohn 4 , Jae Moon Bae 4 , Won Ki Kang 2 , Sung Kim 4 , Kyoung-Mee Kim 3 1 Department of Pathology, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, Cheonan, Korea 2 Department of Medicine, Division of Hematology-Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 3 Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 4 Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea Correspondence to: Kyoung-Mee Kim, email: kkmkys@skku.edu Keywords: programmed death-ligand 1, gastric cancer, prognosis, immune, therapy Received: October 15, 2016 Accepted: December 27, 2016 Published: January 05, 2017 ABSTRACT Programmed death-ligand 1 (PD-L1) is expressed in a subgroup of gastric cancers that may benefit from immunotherapy. Microsatellite instability-high (MSI-H) is a potential predictive factor for response to immunotherapy targeting the PD-1 or its ligand PD-L1. The relationship between PD-L1 expression and MSI-H status remains poorly understood. In this study, we investigated PD-L1 expression in patients with MSI-H gastric cancer. We analyzed PD-L1 expression in 78 MSI-H gastric cancer tissue samples using immunohistochemistry. PD-L1 expression was classified as expression on tumor cells or on immune cells. We observed PD-L1 expression in 48 gastric cancer samples (61.5%), consisting of 7 (9.0%) cases with tumor PD-L1 expression and 47 (60.3%) cases with immune cell PD-L1 expression. Immune cell PD-L1 expression was frequently associated with intestinal type cancer by the Lauren classification ( p = 0.015), with a lower risk of lymph node metastasis ( p = 0.027) and lower tumor stages ( p = 0.029) compared to MSI-H gastric cancers without PD-L1 expression. Moreover, immune cell PD-L1 expression was an independent favorable prognostic factor for overall survival (versus PD-L1 negative; hazard ratio, 3.451; 95% confidence interval, 1.172–12.745; p = 0.025). In MSI-H gastric cancer, PD-L1 expression was observed to be independently associated with a longer survival.