High FOXP3+ regulatory T-cell density in the sentinel lymph node is associated with downstream non-sentinel lymph-node metastasis in gastric cancer

Background: We aimed to evaluate the immunologic nature of sentinel lymph nodes (SLNs) in gastric cancer patients and to determine whether it can predict non-SLN metastasis. Methods: Sentinel lymph node samples were collected from 64 gastric carcinoma patients who had undergone gastrectomy with SLN biopsy. One representative SLN sample was selected from each patient and was subjected to immunostaining for CD8, CD57, FOXP3, and DC-LAMP. The numbers of marker-positive cells in each sample were counted. The relationships between various immune cell densities and clinicopathologic parameters or metastasis status of SLNs and non-SLNs were sought. Results: High FOXP3+ Treg density of the SLN was found to be significantly associated with the presence of metastasis in either SLNs or non-SLNs. DC-LAMP+ cell density of the SLN was the highest at the isolated tumours cell level, and this decreased along with an increase in tumour metastasis in either SLNs or non-SLNs. Univariate and multivariate logistic regression models revealed that high FOXP3+ Treg density of the SLN was an independently significant predictor of non-SLN metastasis. Conclusions: This study is the first to indicate an important role of SLNs in metastatic dissemination of gastric cancer. Our findings suggest that Tregs could be a new therapeutic target for regulating the metastasis of gastric cancer.