PTEN and malignant colon neoplasm: Our results agree with many studies that have shown cell cycle arrest and apoptosis in colon cancer cells with 5-FU single treatment [8,9,21,45,46,47], and further support the notion that resistance to chemotherapy could, at least in part, be related to limited efficacy in modulating the PI3K/PTEN/Akt/mTOR pathway by 5-FU monotherapy [16,48,49].