CDK4 had been reported to be highly expressed and associates with D type cyclins and plays a crucial role in breast cancer.37 However, the basal-like TNBC was reported to be insensitive to CDK4/6 inhibitors due to complicated mechanisms, including regulating the cyclin E/CDK2 activity in a noncatalytic manner by CDK4. The gene discussed is CCNE1; the disease is breast cancer.