This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen & Pelvis, Subject name: Anatomy
[{'content': 'A 3-year-old boy is admitted to the hospital with signs of acute renal failure. Radiologic studies reveal that the boy has bilateral masses involving both kidneys. Examination of biopsy material confirms the diagnosis of Wilms tumor. Which of the following gene mutations is the most common in Wilms tumor? \nSelect and explain. \nA. The gene responsible for WT1, B. The gene responsible for HGF, C. The gene responsible for VEGF, D. The gene responsible for GDNF', 'role': 'user'}, {'content': "Answer: A \nExplanation: Wilms tumor is a kidney malignancy that usually occurs in children. It has recently been shown that it can be caused by mutations in the WT1 gene, behaving according to Knudson's two-hit model for tumor suppressor genes.", 'role': 'assistant'}]