CD4/CD8 + T cells, DC subsets, Foxp3, and IDO expression are predictive indictors of gastric cancer prognosis

Abstract

Background: The tumor microenvironment represents an abnormal niche containing numerous factors, such as T cells, dendritic cells (DCs), regulatory T cells (Tregs), and indoleamine 2,3-dioxygenase (IDO), involved in maintaining immune homeostasis and tolerance. All these factors may influence the choice of therapy and the clinical outcomes.

Methods: Flow cytometry was performed to identify CD4+/CD8 + T cells and DCs, and immunohistochemistry was used to evaluate IDO and Forkhead Box P3 (Foxp3) expression; these experiments were performed in order to explore the clinical and prognostic significance of CD4/CD8 + T cells, DCs, Tregs, and IDO expression in gastric carcinoma.

Results: Smaller tumor size was correlated with higher expression levels of peripheral CD4 + T cells (P = .003) and CD8 + T cells (P = .002), and lower IDO expression (P = .044) in tumors. Well-differentiated gastric carcinomas displayed higher peripheral (P = .029) and tumor-infiltrating CD4 + T cell (P = .009) populations and a higher tumor-infiltrating DC1/DC2 ratio (P = .048). Gastric cancer in the early T stages exhibited higher populations of peripheral DC2s (P = .044) and a higher tumor-infiltrating DC1/DC2 ratio (P = .012). Gastric cancer at the N0 stage had lower tumor-infiltrating DC2s (P = .032) and a higher DC1/DC2 ratio (P = .037). IDO expression was positively correlated with tumor-infiltrating Foxp3 + Tregs (P < .001) as well as DC2s (P < .001), whereas it was negatively correlated with the tumor-infiltrating CD4/CD8 + T cell ratio (P = .023). Tumor-infiltrating Foxp3 + Treg was positively correlated with tumor-infiltrating DC2s (r² = 0.772; P < .001). At T, N, and TNM stages, the expression levels of peripheral DC2s, tumor-infiltrating DC1/DC2 ratios, Foxp3 + Tregs, and IDO were significantly correlated with prognosis (P < .05). The T stage and peripheral DC2s were significant risk factors for overall survival.

Conclusion: Immunocompetent cells and humoral immune factors, including DC2s, CD4+/CD8 + T cells, Foxp3 + Tregs, and IDO, interact with each other to compose a complex community of tumor immune microenvironment, ultimately affecting tumor progression and survival of gastric cancer.

Keywords: dendritic cell; gastric cancer; indoleamine 2,3-dioxygenase; regulator T cell.

Figure 1

Flow cytometry plots of peripheral and tumor‐infiltrating CD4 + and CD8 + T cells. (A) peripheral blood CD4 + T cells and CD8 + T cells; (B) tumor‐infiltrating CD4 + T cells and CD8 + T cells

Figure 2

Flow cytometry plots of peripheral and tumor‐infiltrating DC and its subsets. (A) peripheral DC and its subsets; (B) tumor‐infiltrating DC and its subsets

Figure 3

Immunohistochemical staining for Foxp3 + Treg and IDO expression in gastric cancer tissues (×400): (A) Foxp3 + Treg was high (positive cell staining index = 2.9%); (B) Foxp3 + Treg was low (positive cell staining index = 0.2%). (C) IDO expression was positive. (D) IDO expression was negative

Figure 4

The correlation between peripheral T cell, DCs, and tumor‐infiltrating T cell, DCs, IDO expression, and Foxp3 + Treg. (A) tumor‐infiltrating IDO expression was correlated with Foxp3 + Treg; (B) tumor‐infiltrating IDO expression was correlated with ratio of tumor‐infiltrating DC1/DC2; (C) tumor‐infiltrating IDO expression was correlated with tumor‐infiltrating CD8 + T cells; (D) tumor‐infiltrating IDO expression was correlated with tumor‐infiltrating DC2; (E) peripheral CD4 + T cells were correlated with peripheral DC2 negatively; (F) tumor‐infiltrating Foxp3 + Treg cells were correlated with tumor‐infiltrating DC2 positively

Figure 5

Significant prognostic factors for gastric cancer patients. (A) T stage; (B) N stage; (C) TNM stage; (D) peripheral DC2; (E) Ratio of tumor‐infiltrating DC1/DC2; (F) Tumor‐infiltrating Foxp3 + Treg; (G) Tumor‐infiltrating IDO expression