CD8A and esophageal cancer: When CD8+ T cells ingest exosomal circCCAR122 released from HCC cells, exosomal circUSP727 secreted by non‐small cell lung cancer (NSCLC) or O‐GlcNAc transferase28 derived from esophageal cancer (EC) stem cells, the degradation of PD‐1 is inhibited, which further represses the effects of CD8+ T cells.