Oleuropein and Colorectal Cancer Chemoprevention: Recent Advances into Cellular and Molecular Mechanisms

A growing number of epidemiological studies provide strong evidence regarding the significant association between Olive Oil (OO) consumption and reduced risk of colorectal cancer (CRC). The chemopreventive effects of OO on CRC growth and progression appear likely to be related to the presence, among various components, of "minor bioactive compounds", such as flavonoids, phenolic acids, alcohols, lignans, and secoiridoids, as these molecules have been shown to be endowed with antioxidant, anti-inflammatory, immunomodulatory, and anticancer properties. In particular, Oleuropein (Ole), the major glycosylated secoiridoid found in olive leaves and fruits of the olive tree (Olea europea L.), has attracted growing interest as this molecule exhibits a remarkable anticancer activity. The antitumor activity of Ole appears to rely on targeting multiple signalling pathways underlying cancer cell growth and progression. These observations further indicate a possible therapeutic role of this molecule in the prevention and treatment of human tumors. On the basis of these observations, a growing number of preclinical in vitro and in vivo investigations have been undertaken to unravel the specific mechanisms underlying the antitumor activity of Ole and to assess its potential therapeutic effectiveness in the prevention and treatment of CRC. The results from these studies underpin the potential clinical role of Ole in the prevention and treatment of CRC and may pave the path for more effective and less toxic therapeutic approaches to the prevention and clinical treatment of this tumor and other human neoplasms. This review provides further insight into the molecular mechanisms through which Ole may counteract the growth and progression of CRC and examines the results from emerging studies that underpin the potential clinical role of this molecule in the prevention and treatment of this neoplastic disease.