This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Which of the following is not a cyclin dependent kinase (CDK) inhibitor? \nSelect and explain. \nA. p21, B. p27, C. p53, D. p57', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cyclins form complex with cyclin dependent kinases and regulate the transition of cell cycle from one stage to the other.\nThese CDK complexes in turn are regulated by CDK inhibitor. The inhibitors control the cell cycle by balancing the activity of CDKs. The signals from these inhibitors determine whether a cell progresses through the cell cycle. Changes in the level of these inhibitors may occur in some tumors, or possibly in aging cells.\n\nThe cyclin dependent kinase inhibitors are - p21 - p27 - p57 - p15 - p16 - p18 - p19.', 'role': 'assistant'}]