Intratumoral CD8(+) T/FOXP3 (+) cell ratio is a predictive marker for survival in patients with colorectal cancer

Abstract

The human immune system consists of a balance between immune surveillance against non-self antigens and tolerance of self-antigens. CD8(+) T cells and CD4(+) regulatory T cells (Tregs) are the main players for immune surveillance and tolerance, respectively. We examined immunohistochemically the immunological balance at the tumor site using 94 surgically resected colorectal cancer tissues. Forkhead box P3 (FOXP3)(+) cells were considered to be Tregs in the present study. The number of intratumoral FOXP3(+) cells (itFOXP3(+) cells) was positively correlated with lymph node metastases (P = 0.030). itCD8(+) T/itFOXP3(+) cell ratio negatively correlated with pathological stages (P = 0.048). Next, relationship between the number of itCD8(+) T cells or itFOXP3(+) cells and survival prognosis in 94 patients who underwent a curative resection was analyzed. Only itCD8(+) T/itFOXP3(+) cell ratio positively correlated with disease-free survival (0.023) and overall survival (P = 0.010). Multivariate analysis indicated that itCD8(+) T/itFOXP3(+) cell ratio is an independent prognostic factor (P = 0.035) of overall survival. The number of itFOXP3(+) cells positively correlated with transforming growth factor-beta TGF-beta production at the tumor site (P = 0.020). In conclusion, itCD8(+) T/itFOXP3(+) cell ratio is a predictive marker for both disease-free survival time and overall survival time in patients with colorectal cancer. Importantly, itCD8(+) T/itFOXP3(+) cell ratio may be an independent prognostic factor. And, tumor-producing TGF-beta may contribute to the increased number of itFOXP3(+) cells.

Fig. 1

Immunohistochemical staining shows that FOXP3⁺ lymphocytes are distinguishable from CD8⁺ lymphocytes in colorectal cancer. a FOXP3 positive cells are stained brown, as shown by asterisks (×400). b CD8 positive cells are stained red, as shown by arrows (×400). c Double staining of FOXP3 (asterisks, in cell nucleus) and CD8 (arrows, on cell membrane) (×400). d The correlation between CD8⁺ T cells and FOXP3⁺ cells is shown (Mann–Whitney U test). P values less than 0.05 were considered significant (color figure online)

Fig. 2

The itCD8⁺ T/itFOXP3⁺ cell ratio predicts poor disease-free survival and overall survival in 94 colorectal cancer patients. itCD8⁺ T cells (a and b) and itFOXP3⁺ cells (c and d) correlated with neither disease-free survival nor with overall survival. Disease-free survival and overall survival of the patients showing high an itCD8⁺ T/itFOXP3⁺ cell ratio were significantly better compared with those of the patients showing a low itCD8⁺ T/itFOXP3⁺ cell ratio (e and f). P values less than 0.05 were considered significant

Fig. 3

Representative pictures of immunohistochemical double staining. a A high TGF-β-expressing specimen (red) (×400). b A low TGF-β-expressing specimen are shown (×400). c There are a high number of FOXP3⁺ cells (brown) indicated by asterisks, in the high TGF-β expressing area (×400) (color figure online)