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': 'A 55 year old male patient complains of abnormal growth on right cheek. Patient has a habit of tobacco chewing since 30 years. Radiologic findings reveal 8x8 cm fungating mass, invading maxilla and mandible on right side. Histologic findings are suggestive of squamous cell carcinoma. Which of the following is not true regarding the treatment of this condition? \nSelect and explain. \nA. The drugs used are designed to block DNA replication, B. Methotrexate and 5-fluorouracil block nucleotide synthesis, C. Topoisomerase inhibitors promote the unwinding of parental DNA  strands and prevent replication, D. The drugs used for cancer therapy inhibit the enzymes that participate in replication', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Majority of the drugs used for cancer therapy are designed to block DNA replication or inhibit the\xa0enzymes that\xa0participate in\xa0replication (directly\xa0or\xa0indirectly).\xa0\nMethotrexate (inhibits dihydrofolate\xa0reductase)\xa0and\xa05-fluorouracil (inhibits thymidylate synthase) block nucleotide synthesis.\nIn\xa0recent years, topoisomerase inhibitors\xa0are being\xa0used.\xa0They\xa0block\xa0the\xa0unwinding\xa0of parental DNA\xa0 strands and prevent replication.\n\nKey Concept:\nTopoisomerase inhibitors block the unwinding of parental DNA strands and hence preventing replication.', 'role': 'assistant'}]