RB1 and neoplasm: The main difference between tumor cells and normal cells is that tumor cells can proliferate wirelessly, CDK is a key enzyme that regulates the transition of cell cycle phases, and its continuous activation can lead to proliferation of tumor cells.CDK4/6 is a key regulator of the cell cycle and phosphorylates RB protein with cyclin D, which triggers the cell cycle to enter the S-phase from the G1-phase, thus inhibiting the cellular DNA replication process.