Clinical relevance of PD-1 positive CD8 T-cells in gastric cancer

Abstract

Background We evaluated the relevance of PD-1+CD8+ T-cells in gastric cancer (GC) including prognostic significance, association with chemotherapy and immunotherapy sensitivity and correlations with the tumor microenvironment (TME). Methods Discovery cohort: GC samples were evaluated for AE1/3, CD8, PD-1, Ki-67 and Granzyme-B expression with fluorescence-based multiplex immunohistochemistry (mIHC). Validation cohorts: we analyzed bulk RNAseq GC datasets from TCGA, the “3G” chemotherapy trial and an immunotherapy phase 2 trial. The cox proportional hazards model was used to identify factors that influenced overall survival (OS). To study the TME, we analyzed single-cell RNAseq performed on GCs. Results In the discovery cohort of 350 GCs, increased PD-1 expression of CD8 T-cells was prognostic for OS (HR 0.822, p = 0.042). PD-1 expression in CD8 T-cells highly correlated with cytolytic [Granzyme-B+] (r = 0.714, p < 0.001) and proliferative [Ki-67+] (r = 0.798, p < 0.001) activity. Analysis of bulk RNAseq datasets showed tumors with high PD-1 and CD8A expression levels had improved OS when treated with immunotherapy (HR 0.117, p = 0.036) and chemotherapy (HR 0.475, p = 0.017). Analysis of an scRNAseq dataset of 152,423 cells from 40 GCs revealed that T-cell and NK-cell proportions were higher (24% vs 18% and 19% vs 15%, p < 0.0001), while macrophage proportions were lower (7% vs 11%, p < 0.0001) in CD8PD-1high compared to CD8PD-1low tumors. Conclusion This is one of the largest GC cohorts of mIHC combined with analysis of multiple datasets providing orthogonal validation of the clinical relevance of PD-1+CD8+ T-cells being associated with improved OS. CD8PD-1high tumors have distinct features of an immunologically active, T-cell inflamed TME.

Progresses in biomarkers for cancer immunotherapy

“…What is more, PD‐1+ CD8 T cells that express Ki67 have been reported a predictive character of proliferating T cells for the response to anti‐PD‐1 therapy in melanoma and NSCLC 102,103 . This result is consistent with a most recent study from discovery cohort of 350 GCs patients, indicating that increased PD‐1+CD8+ T‐cells were statistically prognostic for OS and correlated with Granzyme‐B+ and proliferative Ki‐67+ activity with immunotherapy 104 . Additionally, According to Hashemi et al., 105 stromal CD8 + TILs could be powerful predictors of better outcomes in NSCLC patients previously treated with anti‐PD‐1 therapy, based on real‐world study.…”

Early Increase in Circulating PD-1+CD8+ T Cells Predicts Favorable Survival in Patients with Advanced Gastric Cancer Receiving Chemotherapy

“…However, there was a significant difference in the DOR, and the significant difference in survival was largely attributed to the differences among responders. Similarly, Choo et al showed that in 58 patients who received first-line platinum and fluoropyrimidine doublet as palliative treatment, patients with high PDCD1 and CD8A expression had longer PFS and OS, albeit not related to the response [23,49]. This suggests that even if the cytotoxic effect of chemotherapy provides a similar reduction effect on the tumor, other factors beyond cytotoxicity contribute to the durable effect of chemotherapy, which may be associated with increased tumor-specific immunity, represented by high circulating PD-1 + CD8 + T cells levels on day 7.…”

“…Several studies have been conducted to elucidate the prognostic significance of PD-1 + CD8 + T cells present in the TME of GC; however, their results are conflicting [11,17,23,47]. Choo et al analyzed tissues from 350 patients with stage I-IV GC and found a strong correlation between PD-1 + CD8 + tumor-infiltrating lymphocytes (TILs) and the expression of Ki-67 and Granzyme B.…”

“…Choo et al analyzed tissues from 350 patients with stage I-IV GC and found a strong correlation between PD-1 + CD8 + tumor-infiltrating lymphocytes (TILs) and the expression of Ki-67 and Granzyme B. Their findings highlight the association between the presence of PD-1 + CD8 + TIL and improved prognosis [23]. Park et al also showed that PD-1 expression in CD8 + TIL is associated with other immune checkpoint molecules (LAG3 and TIM) and better survival [47].…”

“…Recent studies on GC have shown that PD-1 expression in tumor-infiltrating CD8 + T cells does not always indicate exhaustion or diminished cytokine production, as these cells can produce pro-inflammatory cytokines similar to effector T cells [17]. Associations between high PD-1 + CD8 + T cell levels in TME or peripheral blood and the presence of a favorable prognosis have been established [20][21][22][23].…”