Targeting PTEN in colorectal cancers

Phosphatase and tensin homolog (PTEN) is a tumour suppressor that represents one of the most common targets for genetic defect in human cancer. PTEN controls an array of physiopathological processes related to cell proliferation, differentiation, DNA/chromosome integrity, apoptosis and invasiveness. PTEN dephosphorylates not only proteins, but also phosphoinositides generated by phosphatidylinositol 3-kinase, thus counteracting the Akt signalling pathway. Interestingly, PTEN can also exert some biological functions independently of its catalytic activity. A feature of colorectal cancers is the relatively low incidence of PTEN mutation or deletion, whereas PTEN downregulation occurs in approximately one third of tumours. PTEN inactivation may be even higher when changes in posttranslational modifications and/or mislocalization of the tumour suppressor are accounted for. Strategies based on pharmacologically-induced restoration of wild-type PTEN function in colon cancer cells could therefore be considered, to impact cell growth, trigger apoptosis, and sensitize tumour cells to therapeutic agents. This review details current knowledge of the mechanisms regulating PTEN expression, activity and function. It also focuses on the use of small molecules targeting positive or negative PTEN regulators and summarizes alternative strategies that could be used to alter PTEN conformation/activity. Finally, we propose an outline of a personalized approach to restore PTEN function in colon cancer cells.