 Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D. In mammals cholesterol is either absorbed from dietary sources or is synthesized "de novo".Up to 70-80% of "de novo" cholesterol synthesis occurs in the liver, and about 10% of "de novo" cholesterol synthesis occurs in the small intestine.Cancer cells require cholesterol for cell membranes, so cancer cells contain many enzymes for "de novo" cholesterol synthesis from acetyl-CoA.