In order to explore the key genes associated with T-cell exhaustion in multiple cancers, we performed transcriptomic analysis of single CD8+ T cells isolated from three cancers, including CRC, HCC, and NSCLC and identified different cell types, thereunto, Pre_exhaust and Tex cells overexpressed exhaustion markers and enriched in the negative regulation of immune progress. The gene discussed is CD8A; the disease is colorectal carcinoma.