Clinical significance of CD45RO+ memory T cell in human esophageal cancer

263 Memory T cells survive for many months and years and critically important for host defence in humans. In tumor immunity, they have been also suggested to play a significant role in tumor progression and metastasis. However, the clinical importance of memory T cells in actual human cancer remains largely unknown. In this study, we tried to reveal the clinical significance of tumor-infiltrating CD45RO+ memory T cells in human esophageal cancer. We examined 60 esophageal cancer patients who underwent surgery in our department. The median age of the patients was 61.9 years, with a range of 42 to 75 years. Forty-six patients were male and 14 were female. Histopathological and clinical findings were scored according to the UICC-TNM classification. We performed immunohistochemistry on esophageal cancer tissues and counted the cells stained positively for CD45RO+ infiltrating into cancer tissue. The mean number of positively stained cells was 104 (range 105-211). Then we defined 30 patients with high density of CD45RO+ T cells (more than 104 positive cells per HPF) as CD45RO+hi and 30 patients with low density of CD45RO+ T cells as CD45RO+lo (fewer than 104 positive cells per HPF). Interestingly, CD45RO+hi patients with esophageal cancer had a significantly better prognosis than CD45RO+lo patients (1-year survival rate; 86.7% vs 70%, 3-year survival rate; 64.8% vs 30.8%, 5-year survival rate; 54.1% vs 30.8%, respectively; P=0.036). In addition, among T1 tumors, there was significant difference in postoperative overall survival rate between CD45RO+hi and CD45RO+lo patients with esophageal cancer (1-year survival rate; 100% vs 83.3%, 3-year survival rate; 83.3% vs 33.3%, 5-year survival rate; 83.3% vs 33.3%, respectively; P=0.011). Further analysis revealed that there was significant correlation of CD45RO status with positive venous invasion (P=0.045: 5 of 30, 16.7% CD45RO+hi versus 12 of 30, 40% CD45RO+lo). In conclusion, we have demonstrated for the first time that CD45RO+ memory T cell has a significant prognostic value in human esophageal cancer, and also our data suggested that adaptive immune response is functionally critical in human esophageal cancer.