Proliferation of T-cell subsets that contact tumour cells in colorectal cancer

Abstract

We have investigated the proliferation rates of T-cell subsets in colorectal carcinomas using immunohistochemistry. It was found that the tumour-infiltrating T cells in contact with the tumour cells have a significantly higher frequency of proliferation than those in the stroma. In particular, the CD8+ intraepithelial lymphocytes (T-IEL) within the tumours have a significantly higher frequency of proliferation in comparison with CD8+ T cells in the stromal compartment or in any normal mucosal lymphoid tissues. It is possible that the proliferation of the CD8+ T-IEL may be driven by self-antigens expressed on the tumour cells. The proportion of CD3+ CD7- T cells is increased within carcinomas compared with the normal colon, and a population of CD57+ T cells was observed which is absent from the normal colon. It is possible that these phenotypes are acquired in situ due to repeated stimulation of the T cells by tumour antigens. Intact colorectal carcinoma explants were cultured, and the presence of tumour-infiltrating T cells analysed after 3 days of culture in isolation from the systemic compartments. CD3+ T cells were proliferating (at a low rate) within the explants after 3 days of culture, indicating that they may be sustained by factors present in the tumour microenvironment.

Fig. 1

A comparison of the proportions of colorectal carcinoma-infiltrating T cells of different subsets in the IEL and stromal compartments. The mean percentages (and standard errors) of T cells expressing various phenotypic markers are compared in colorectal carcinoma-infiltrating IEL () and colorectal carcinoma-infiltrating stromal cells (□).

Fig. 2

A comparison of the proliferation frequencies of different colorectal carcinoma-infiltrating T-cell subsets. The mean percentages (and standard errors) of proliferating T cells from various subsets were calculated in intraepithelial cells () and in stromal cells (□).

Fig. 3

(a) Section of colorectal carcinoma from patient A, stained using an antibody to Ki67 (immunoperoxidase: brown), followed by an antibody to CD4 (alkaline phosphatase: blue); (b) section of colorectal carcinoma from patient A, stained using an antibody to Ki67 (immunoperoxidase: brown), followed by an antibody to CD8 (alkaline phosphatase: blue); (c) section of a colorectal carcinoma explant from patient M on day 3 of culture, stained using an antibody to Ki67 (immunoperoxidase: brown), followed by an antibody to CD3 (alkaline phosphatase: blue).

Fig. 4

A comparison of the proliferation frequencies of different T-cell subsets in colorectal carcinomas, tonsils and Peyer’s patches. The mean percentages (and standard errors) of proliferating CD3⁺, CD4⁺ and CD8⁺ T cells are compared in tonsillar TCZ (▪), Peyer’s patch TCZ (□), colorectal carcinoma IEL () and colorectal carcinoma stroma (). The CD8⁺ subset is proliferative in the carcinoma specimens, but not in the tonsils or the Peyer’s patches.

Fig. 5

(a) The proportions of Ki67⁺ tumour cells in colorectal carcinomas before culture () and after 3 days of culture (□); (b) the numbers of CD3⁺ cells in the IEL compartment were determined on day 0 () and day 3 (□) of culture of specimens of colorectal carcinomas.