Compared with para-tumor-derived CD8+ T cells, immune checkpoint genes (LAG3, CTLA4, CD96, and HAVCR2) were under-expressed in tumor-derived CD8+ T cells, while cytotoxic effector molecules (GZMH and GZMA) and pro-inflammatory cytokines (IL32 and CCL5) were highly expressed, indicating that these cells in cluster CD8_3 were tumor-associated cytotoxic T lymphocytes. The gene discussed is HAVCR2; the disease is neoplasm.