CD8A and esophageal squamous cell carcinoma: It has been demonstrated that a low proportion of CD103+CD8+ TRMs was strongly associated with immunotherapy failure in patients with different tumor types, such as esophageal squamous cell carcinoma, lung cancer and melanoma (18, 61–63), which showed indirectly that the role of CD103+CD8+ TRM subsets in immune checkpoint therapy cannot be ignored.