Inherited GI Disorders, Nutrition & Abdominal Hernias
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Clinical VignetteQuestion 1 of 21
Polyp Carpet Kid
A 19-year-old man is referred to gastroenterology because his father died of colorectal cancer at age 38. He has no abdominal symptoms. Screening colonoscopy reveals hundreds of small polyps carpeting the entire colon; biopsy confirms tubular adenoma histology. Genetic testing identifies a germline pathogenic variant in the APC gene on chromosome 5q21. Immunohistochemistry of the polyp tissue shows complete absence of APC protein in the adenomatous epithelium.
In colonocytes lacking APC protein, which of the following most directly drives uncontrolled proliferation?