Intraepithelial effector (CD3+)/regulatory (FoxP3+) T-cell ratio predicts a clinical outcome of human colon carcinoma

Abstract

Background & aims: Regulatory T cells (Tregs) express the forkhead box transcription factor (FoxP3) and suppress the antitumor immune response. We investigated whether the intratumoral densities of FoxP3(+) and effector CD3(+) lymphocytes are associated with prognosis of patients with colon cancer.

Methods: FoxP3 and CD3 expression and location were determined in stage II and III colon carcinomas (n = 160) and normal mucosa (n = 25) by immunohistochemistry; CD4 and FoxP3 were localized by dual immunofluorescence microscopy. T-cell markers were compared with pathological variables, DNA mismatch repair status, and patient survival using Cox proportional hazards models.

Results: FoxP3(+) and CD3(+) T-cell densities were increased in carcinomas compared with autologous normal mucosa (P < .0001). An increase in intraepithelial FoxP3(+) cells was associated with poor tumor differentiation (P = .038), female sex (P = .028), and advanced patient age (P = .042). FoxP3(+) cell density was not prognostic, yet patients with tumors with reduced intraepithelial CD3(+) T-cell densities had reduced disease-free survival (DFS) rates (hazard ratio [HR], 1.87 [95% confidence interval, 1.10-3.16]; P = .018). A low intraepithelial CD3(+)/FoxP3(+) cell ratio predicted reduced DFS (46.2% vs 66.7% survival at 5 years; HR, 2.17 [95% confidence interval, 1.11-4.23]; P = .0205). The prognostic impact of these markers was maintained when tumors were stratified by mismatch repair status. By multivariate analysis, a low CD3(+)/FoxP3(+) cell ratio (P= .0318) and low numbers of CD3(+) T cells (P = .0397) predicted shorter DFS times and were stronger prognostic variables than tumor stage or number of lymph node metastases.

Conclusions: A low intraepithelial CD3(+)/FoxP3(+) cell ratio and reduced numbers of CD3(+) T cells were associated with shorter patient survival time, indicating the importance of an effector to Treg cell ratio in colon cancer prognosis.

Figure 1

Top, FoxP3⁺ T lymphocytes (brown color) are seen in peritumoral stroma and infiltrating epithelial cells of a sporadic colon carcinoma using immunohistochemistry (400X). Inset, Dual staining for FoxP3⁺ (nuclear) and CD4⁺ (cytoplasm) are seen in colon carcinoma cells using immunofluorescence microscopy. Bottom, Epithelial and stromal CD3⁺ T lymphocytes are shown in a colon carcinoma at light microscopy (400X).

Figure 2

Top, density of intraepithelial versus stromal FoxP3⁺ (A), CD3⁺ (B), or the CD3⁺:FoxP3⁺ T lymphocyte ratio (C) in TNM stages II and III colon carcinomas. Bottom, comparison of the density of FoxP3⁺ T lymphocytes infiltrating tumor epithelia (A), stroma (B), and the epithelial to stromal ratio in DNA mismatch repair (MMR)-deficient versus –proficient colon carcinomas. Box plots show median values, interquartile ranges, and extreme values (error bars).

Figure 3

Association of intraepithelial FoxP3⁺ (A), CD3⁺ (B) TILs or the CD3⁺:FoxP3⁺ ratio (C) with disease-free survival (DFS) in patients with TNM stage II and III colon carcinomas. Data are dichotomized by quartiles into high (> 1^st quartile) and low (≤ 1^st quartile) groups as shown.