CDK4 and neoplasm: Treatment of CT26 syngeneic mouse tumors with the CDK4/6 inhibitor abemaciclib led to an increase in tumor-infiltrating T lymphocytes, and a significant upregulation of T-cell activity, as evidenced by the increased expression of T-lymphocyte activation markers (e.g., IFNG, GZMB, CCL4 and CCL5).