CD8A and colorectal cancer: CDKN1A, also known as p21, is a gene that could control cell cycle.29 Deficiency of CDKN1A could inhibit exhaustion of Th1 cells and reduce cancer-related survival in colorectal cancer, which can be reversed by cyclin-dependent kinase (CDK) inhibitors such as palbociclib.30 Similarly, we found that CDKN1A + CD8 T lymphocytes exhibited low-level of exhaustion with high stemness and memory.