Anthocyanin-containing purple-fleshed potatoes suppress colon tumorigenesis via elimination of colon cancer stem cells
7 September 2015

Bergerac, our purple-fleshed potato

Cancer stem cells (CSCs) are shown to be responsible for initiation and progression of tumors in a variety of cancers. We previously showed that anthocyanin-containing baked purple-fleshed potato (PP) extracts (PA) suppressed early and advanced human colon cancer cell proliferation and induced apoptosis, but their effect on colon CSCs is not known. Considering the evidence of bioactive compounds, such as anthocyanins, against cancers, there is a critical need to study anti-cancer activity of PP, a global food crop, against colon CSCs. Thus, isolated colon CSCs (positive for CD 44, CD 133 and ALDH1b1 markers) with functioning p53 and shRNA-attenuated p53 were treated with PA at 5.0 μg/mL. Effects of baked PP (20 % w/w) against colon CSCs were also tested in vivo in mice with azoxymethane induced colon tumorigenesis. Effects of PA/PP were compared to positive control sulindac. In vitro, PA suppressed proliferation and elevated apoptosis in a p53 independent manner in colon CSCs. PA, but not sulindac, suppressed levels of Wnt pathway effector β-catenin (a critical regulator of CSC proliferation) and its downstream proteins (c-Myc and cyclin D1) and elevated Bax and cytochrome c, mitochondria-mediated apoptotic proteins. In vivo, PP reduced the number of crypts containing cells with nuclear β-catenin (an indicator of colon CSCs) via induction of apoptosis and suppressed tumor incidence similar to that of sulindac. Combined, our data suggests that suppression of Wnt/β-catenin signaling and elevated apoptosis via mitochondria-mediated apoptotic pathway by PP may contribute to reduced colon CSCs number and tumor incidence in vivo.