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BackgroundWe have previously shown that the grape bioactive compound resveratrol (RSV) potentiates grape seed extract (GSE)-induced colon cancer cell apoptosis at physiologically relevant concentrations. However, RSV-GSE combination efficacy against colon cancer stem cells (CSCs), which play a key role in chemotherapy and radiation resistance, is not known.MethodsWe tested the anti-cancer efficacy of the RSV-GSE against colon CSCs using isolated human colon CSCs in vitro and an azoxymethane-induced mouse model of colon carcinogenesis in vivo.ResultsRSV-GSE suppressed tumor incidence similar to sulindac, without any gastrointestinal toxicity. Additionally, RSV-GSE treatment reduced the number of crypts containing cells with nuclear β-catenin (an indicator of colon CSCs) via induction of apoptosis. In vitro, RSV-GSE suppressed - proliferation, sphere formation, nuclear translocation of β-catenin (a critical regulator of CSC proliferation) similar to sulindac in isolated human colon CSCs. RSV-GSE, but not sulindac, suppressed downstream protein levels of Wnt/β-catenin pathway, c-Myc and cyclin D1. RSV-GSE also induced mitochondrial-mediated apoptosis in colon CSCs characterized by elevated p53, Bax/Bcl-2 ratio and cleaved PARP. Furthermore, shRNA-mediated knockdown of p53, a tumor suppressor gene, in colon CSCs did not alter efficacy of RSV-GSE.ConclusionThe suppression of Wnt/β-catenin signaling and elevated mitochondrial-mediated apoptosis in colon CSCs support potential clinical testing/application of grape bioactives for colon cancer prevention and/or therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1254-2) contains supplementary material, which is available to authorized users.

The World Health Organization predicts over a 70% increase in cancer incidents in developing nations over the next decade. Although these nations have limited access to novel therapeutics, they do have access to foods that contain chemopreventive bioactive compounds such as anthocyanins, and as such, consumption of these foods can be encouraged to combat cancer. We and others have previously characterized the anti-colon cancer properties of dietary anthocyanins from different sources. Eugenia jambolana (Java plum) is a tropical medicinal fruit rich in anthocyanins, however, its anti-colon cancer properties are not well characterized. Furthermore, recent evidence suggests that colon cancer stem cells (colon CSCs) promote resistance to chemotherapy, relapse of tumors and contribute to poor prognosis. The objectives of this study were to 1) characterize the anthocyanin profile of Java plum using HPLC-MS; and 2) determine the anti-proliferative (cell counting and MTT) and pro-apoptotic (TUNEL and caspase 3/7 glo assay) properties of Java plum fruit extract (JPE) using HCT-116 colon cancer cell line and colon CSCs (positive for CD 44, CD 133 and ALDH1b1 markers). HPLC-MS analysis showed that JPE contains a variety of anthocyanins including glucosides of delphinidin, cyanidin, petunidin, peonidin and malvidin. JPE anthocyanins suppressed (p < 0.05) proliferation in HCT-116 cells and elevated (p < 0.05) apoptosis in both HCT-116 cells and colon CSCs. JPE also suppressed the stemness in colon CSCs as evaluated using colony formation assay. These results warrant further assessment of the anti-cancer activity of JPE, and its molecular mechanisms using pre-clinical models of colon cancer.

Basal colonic crypt stem cells are long lived and play a role in colon homeostasis. Previous evidence has shown that high-calorie diet (HCD) enhances colonic stem cell numbers and expansion of the proliferative zone, an important biomarker for colon cancer. However, it is not clear how HCD drives dysregulation of colon stem cell/colonocyte proliferative kinetics. We used a human-relevant pig model and developed an immunofluorescence technique to detect and quantify colonic stem cells. Pigs (n = 8/group) were provided either standard diet (SD; 5 % fat) or HCD (25 % fat) for 13 weeks. HCD and SD consuming pigs had similar total calorie intake, serum iron, insulin, and glucose levels. However, HCD elevated both colonic proliferative zone (KI-67) and stem cell zone (ASCL-2 and BMI-1). Proliferative zone correlated with elevated innate colonic inflammatory markers TLR-4, NF-kB, IL-6 and lipocalin-2 (r ≥ 0.62, p = 0.02). Elevated gut bacterial phyla proteobacteria and firmicutes in HCD consuming pigs correlated with proliferative (r ≥ 0.67, p = 0.05) and stem cell zone (r ≥ 0.66, p = 0.05). Colonic proteome data revealed the upregulation of proteins involved in cell migration and proliferation, and correlated with proliferative and stem cell zone expansion. Our study suggests that pig colon, unlike mice, has two distinct stem cells (ASCL-2 and BMI-1) similar to humans and HCD increases expansion of colonic proliferative and stem cell zone. Thus, pig model can aid in development of preventive strategies against gut bacterial dysbiosis and inflammation promoted diseases such as colon cancer.

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