CD8A and carcinoma of esophagus: O‐GlcNAc transferase, a nutrient sensor that regulates glycolysis and lipid metabolism in cancer, could be contained in exosomes derived from aldehyde dehydrogenase (ALDH) positive esophageal carcinoma stem cells and was capable of penetrating adjacent CD8+ T cells and upregulating PD‐1 expression in CD8+ T cells.209