CTLA4 and head and neck squamous cell carcinoma: Through TCGA-HNSCC data analysis, we proved that overexpression of SEMA7A was positively correlated with elevation of immune checkpoint (PDCD1LG2, PD-L1, CTLA4, TIM3, TIGIT, and PD-1) expression, a decrease in activated CD8+ T cells and increased infiltration of exhausted CD8+ T cells (Fig. 8a, b).