e15609 Background: Recent data supports a potentially significant role for immune checkpoint inhibitors in the treatment of gastric cancer. However, there are few data on the clinical implications of immunotherapy markers in gastric signet-ring cell carcinoma (SRCC). We evaluated the expression of programmed cell death protein-1 (PD-1), programmed cell death ligand 1 (PD-L1), infiltration by CD3+ T cell, microsatellite instability (MSI), and Epstein-Barr Virus (EBV), and the relationship of each factor to survival in SRCC patients. Methods: SRCC samples from 89 patients were stained by immunohistochemistry to evaluate PD-L1, PD-1, CD3+ T cells, and MSI. EBV was detected by DNA in-situ hybridization. Results: All 89 patients had advanced gastric SRCC (89.9% were stage III, 10.1% were stage IV). All patients received 5-FU-based first-line chemotherapy. PD-L1 and PD-1 were expressed in 40.4% and 18.0% of the patients, respectively. There was a significant correlation between PD-L1 and PD-1 expression (r = 0.363, p < 0.001). There was loss of at least 1 of the 4 DNA mismatch repair (DNA-MMR) gene proteins in 32.6% of samples. However, there was no association between the expression of PD-L1, PD-1 or MSI status to overall survival (OS). Only 1 case out of 89 was EBV positive, with concurrent PD-L1 positivity, a high degree of CD3+ T cell infiltration and MSI. Increased CD3+ T cells numbers was associated with increased PD-1 expression (r = 0.256, p = 0.012) and MSI status (r = 0.208, p = 0.05). High CD3+ T cell infiltration was related to better OS (23.7 months, 95% CI: 19.0-38.0 vs 15.8 months, 95% CI: 13.0-22.0, p = 0.033), but was not an independent prognostic factor for survival after multivariate analysis (HR = 0.68, 95% CI: 0.42-1.10, p = 0.116). Conclusions: CD3+ T cell was more infiltrated in PD-1 positive, tumors with MSI and were associated with better OS, indicating an adaptive immune resistance may be occurring. Further research into the cancer characteristics and immunotherapy markers of the gastric SRCC immune microenvironment may highlight targets for immunotherapy.
Automated Quantitation of CD8-positive T Cells Predicts Prognosis in Colonic Adenocarcinoma With Mucinous, Signet Ring Cell, or Medullary Differentiation Independent of Mismatch Repair Protein Status
