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: Pharmacology
[{'content': 'How does MDR gene act? \nSelect and explain. \nA. Block drug activation, B. Block intracellular DNA synthesis, C. Cause efflux of drug, D. DNA repair inhibition', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The multidrug resistance (MDR) gene encodes a protein that actively pumps drugs out of tumor cells. This gene confers resistance on a variety of antitumor drugs, including the antibiotics and plant-derived compounds. Tumor resistance to a given chemotherapeutic agent can often be overcome by the administration of multiple drugs. Ref: Sabel M.S. (2010). Chapter 44. Oncology. In G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13e.', 'role': 'assistant'}]