Prognostic relevance of tumor-resident memory T cells in metastatic lymph nodes of esophageal squamous cell carcinoma

Tumor-resident memory T (T_RM) cells in primary tumors are reportedly associated with a favorable prognosis in several malignancies. However, the behaviors and functions of T_RM cells in regional lymph nodes (LNs) of esophageal cancer remain poorly understood. The aim of this study was to elucidate the effects of T_RM cells in regional LNs of esophageal cancer on clinicopathological findings and prognosis. Specimens of esophageal cancer and primary metastatic LNs (recurrent nerve LNs) were obtained from 84 patients who underwent radical esophagectomy between 2011 and 2017. We performed immunohistochemistry to enumerate and analyze T_RM cells, and used flow cytometry to investigate the function of T_RM cells. T_RM cells were observed in both metastatic LNs and primary tumors. T_RM cell-rich specimens exhibited reduced lymphatic invasion and LN metastasis and prolonged survival compared with T_RM cell-poor specimens. T_RM cells in metastatic LNs were more significantly associated with enhanced survival than T_RM cells in primary tumors. T_RM cells expressed high levels of granzyme B as a cytotoxicity marker. Our results suggested that high T_RM cell infiltration in metastatic LNs improves survival even though LN metastasis is commonly associated with poor prognosis. T_RM cells possibly contribute to antitumor immunity in regional LNs.