The intratumoural subsite and relation of CD8(+) and FOXP3(+) T lymphocytes in colorectal cancer provide important prognostic clues

Abstract

Background: To find improved tools for prognostic evaluation in patients with colorectal cancer (CRC), we have analysed how infiltration of cytotoxic T lymphocytes (CD8(+)) and regulatory T lymphocytes (FoxP3(+)) correlates to prognosis, not only according to quantity and relation, but also to subsite within tumours of different molecular characteristics (microsatellite instability and CpG island methylator phenotype status).

Methods: CD8 and FOXP3 expression was evaluated by immunohistochemistry in 426 archival tumour tissue samples from patients surgically resected for CRC. The average infiltration of CD8(+) and FOXP3(+) cells was assessed along the tumour invasive front, in the tumour centre and within the tumour epithelium (intraepithelial).

Results: We found that infiltration of CD8(+) T lymphocytes within the tumour epithelium provided the strongest prognostic information (P<0.001). At the tumour invasive front and tumour centre, FOXP3 expression withheld the strongest association to prognosis (P<0.001), suggesting FOXP3(+) T-lymphocyte infiltration to be a better prognostic tool than CD8(+) T lymphocytes at these intratumoural subsites. We further analysed the possible prognostic impact of the relation between these T-cell subsets, finding that a high intraepithelial CD8 expression was associated with a better patient outcome, independent of FOXP3 infiltration. In groups of low intraepithelial CD8 expression, however, a high infiltration rate of FOXP3(+) cells at the tumour invasive front, significantly improved prognosis.

Conclusions: Analyses of intraepithelial infiltration of CD8(+) T lymphocytes, infiltration of FOXP3(+) T lymphocytes at the tumour front or centre, and the relation between these subsets, may be a valuable tool for predicting prognosis in colon cancer.

Figure 1

Evaluation of immune marker expression at intratumoural subsites of colon carcinoma. Expression of CD8⁺ cells determined by immunohistochemistry at the invasive front, tumour centre and within the tumour epithelium (intraepithelial expression, indicated by arrows).

Figure 2

Cancer-specific survival in colon cancers. Cases scored (A) for expression of CD8 and FOXP3 total score: score 3–4 (low), 5–6 (moderate) or 7–12 (abundant) expression; or (B) at intratumoural subsites, CD8 IE (intraepithelial) and FOXP3 F (front), score 1–4: score 1 (no/sporadic), score 2 (moderate), score 3 (abundant) and score 4 (highly abundant). Shown are Kaplan–Meier plots. Log-rank tests were used to calculate P values.

Figure 3

Cancer-specific survival of colon cancers. Cases scored for the quotient of (A) the total score: score 3–4 (low), 5–6 (moderate) or 7–12 (abundant) of CD8/FOXP3 expression; or (B) CD8 IE/FOXP3 F, score 1–4: score 1 (no/sporadic), score 2 (moderate), score 3 (abundant) and score 4 (highly abundant). (C) Cancer-specific survival of cases scored for subgroups of CD8Lo, score 1–2; CD8Hi, score 3–4; FOXP3Lo, score 1–2; and FOXP3Hi, score 3–4. Shown are Kaplan–Meier plots. Log-rank tests were used to calculate P values.

Figure 4

Cancer-specific survival in subgroups of colon cancer arranged according to MSI screening status. Cases scored for CD8 IE or FOXP3 F expression, score 1–4: score 1 (no/sporadic), score 2 (moderate), score 3 (abundant) and score 4 (highly abundant). Shown are Kaplan–Meier plots of specimens of (A) MSI cases and (B) MSS cases. Log-rank tests were used to calculate P values.