Regulatory T cell infiltration predicts outcome following resection of colorectal cancer liver metastases

Abstract

Background: Tumor-infiltrating lymphocyte (TIL) counts in colorectal cancer liver metastases (CRCLM) predict survival following resection. While CD4 and CD8 T cells have been correlated with outcome following CRCLM resection, the role of regulatory T cells (Treg) is not well defined.

Methods: TIL in 188 patients who underwent CRCLM resection between 1998 and 2000 were analyzed by immunohistochemistry using tissue microarrays. Correlation between TIL composition and outcome was determined while controlling for established prognostic factors. Total T cells (CD3), helper T cells (CD4), cytotoxic T cells (CD8), and Treg (FoxP3) were analyzed.

Results: Median follow-up time was 40 months for all patients and 95 months for survivors. Overall survival (OS) at 5 and 10 years was 40 and 25%, respectively. The CD4 T cell count correlated with OS (p = .02) and recurrence-free survival (p = .04). A high number of CD8 T cells relative to total T cells (CD8:CD3 ratio) predicted longer OS times (p = .05). Analysis of Treg revealed that high FoxP3:CD4 (p = .03) and FoxP3:CD8 (p = .05) ratios were independent predictors of shorter OS. Patients with a high clinical risk score (CRS) were more likely to have a high number of intratumoral Treg, and patients ≥65 years old had a less robust CRCLM T cell infiltration.

Conclusions: A high number of Treg relative to CD4 or CD8 T cells predicted poor outcome, suggesting an immunosuppressive role for FoxP3 + TIL. The intratumoral immune response was an independent predictor of outcome in patients with colorectal liver metastases.

FIG. 1

Tissue microarray samples from resected CRCLM were stained for various T cell markers. a The distributions of TIL counts for each marker are shown. The bars indicate the cutoff points (cells/tissue core) for each cell marker (CD3 = 174, CD4 = 26, CD8 = 95, FoxP3 = 44). Overall (b) and recurrence-free (c) survival were determined by the Kaplan–Meier method, and we used the log-rank test to compare groups

FIG. 2

Tissue microarray samples from resected CRCLM were stained for various T cell markers and cell ratios were calculated. We analyzed various ratios based on CD3, CD4, and CD8 staining of TIL (a). In addition, we examined ratios of FoxP3+ TIL to CD4 and CD8 T cells (b). Overall and recurrence-free survival were determined by the Kaplan–Meier method and we used the log-rank test to compare groups

FIG. 3

The frequencies of CD3+ TIL counts and proportion with high TIL subset counts is shown for subgroups defined by clinical risk score (a), systemic therapy (b), age (c), primary tumor node status (d), and presence of extrahepatic disease (e). Neoadjuvant therapy refers to treatment given prior to hepatic resection. The distribution plots on the left reveal the CD3+ TIL counts for all patients, and the p values represent comparisons of the mean cell numbers among subgroups. The bar graphs on the right demonstrate the proportion of patients within each subgroup who had high TIL counts for each marker. The cutoff points (cells/ tissue core) for each cell marker are as follows: CD3 = 174, CD4 = 26, CD8 = 95, FoxP3 = 44