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: Biochemistry
[{'content': 'Which  enzymatic  mutation  is  responsible  for immortality of cancer cells? \nSelect and explain. \nA. DNA reverse transcriptase, B. RNA polymerase, C. Telomerase, D. DNA polymerase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: With respect to cancer, when tumor cells divide rapidly their telomeres often shorten.\nSuch telomeres\xa0 (usually detected in leukocytes because of ease of obtaining them) have been implicated as a risk\xa0 factor for many, but not all, solid tumors (eg, breast cancer).\xa0\nShort telomeres appear to be of predictive value regarding the progression of chronic inﬂammatory diseases (such as\xa0 ulcerative colitis and Barrett esophagus) to cancer.\nThe activity of telomerase, the main enzyme involved in synthesizing telomeres, is frequently\xa0 elevated in cancer cells, providing one mechanism for overcoming telomere shortening.\xa0\nSelective\xa0 inhibitors of telomerase have been considered as possible drugs for treating cancer, but have not as\xa0 yet been translated into successful clinical usuage.\n\nKey Concept:\nTelomerase is the main enzyme that is seen elevated in cancer cells.\nRef : Harper’s illustrated biochemistry, 31st edition.', 'role': 'assistant'}]