CTLA4 and esophageal squamous cell carcinoma: Recently, Gao et al. implemented Single-SampleGeneSet Enrichment Analysis to establish two ESCC subtypes (Immunity-High and Immunity-Low) and suggested the Immunity-High subtype may respond to immunotherapy because of higher expression of immune checkpoints, such as PD1, PD-L1, CTLA4 and CD80 [50].