Localisation pattern of Foxp3(+) regulatory T cells is associated with clinical behaviour in gastric cancer

It has been reported that the population of regulatory T cells (T regs) is increased in tumour-infiltrating lymphocytes in cancer-bearing hosts. Recently, forkhead/winged helix transcription factor p3, Foxp3, is thought to be the most reliable marker of T regs. In the present study, we investigated the prevalence and localisation pattern of Foxp3(+) cells in gastric cancer (n=80) by immunohistochemistry, in relation to the clinical outcome of gastric cancer patients. Immunohistochemical staining was performed with anti-Foxp3 mAb, and Foxp3(+) cells were semiquantified. We divided all cases into two groups: Foxp3(+)-high (n=40) and Foxp3(+)-low (n=40) groups, by the median size of the population of Foxp3(+) cells. Furthermore, in terms of the localisation pattern of accumulating Foxp3(+) cells in tumours, we classified all cases into three groups: a peri-tumour group (n=30), a diffuse group (n=40), and a follicular group (n=10). As a result, although the populations of Foxp3(+) cells in stage IV were significantly larger than those in stage I (P<0.05), there was no significant difference in survival between the patients with high and low population levels of Foxp3(+) cells. However, survival in patients with a diffuse pattern of Foxp3(+) cells was significantly poorer than in those with a peri-tumoral pattern. In conclusion, the localisation pattern, but not the population size, of Foxp3(+) cells was significantly related to patient survival.