Grape compounds suppress colon cancer stem cells in vitro and in a rodent model of colon carcinogenesis.

Lavanya Reddivari,Ramakrishna Vadde,Joshua D. Lambert,Venkata Charepalli,Jairam K. P. Vanamala,Ryan J. Elias,Sridhar Radhakrishnan

doi:10.1186/s12906-016-1254-2

Abstract

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.

Highlights

We have previously shown that the grape bioactive compound resveratrol (RSV) potentiates grape seed extract (GSE)-induced colon cancer cell apoptosis at physiologically relevant concentrations
Our previous studies support this notion, as we demonstrated using a well-established combination index method that a RSV (~25 μM) and GSE (35–50 μg/ml) mixture was potent in suppressing proliferation and elevating apoptosis in the HCT-116 human colon cancer cell line at lower concentrations compared to RSV or GSE alone [10, 11]
RSV-GSE and sulindac treatment for one week reduced the number of crypts containing cells with nuclear β-catenin by more than 50 % (Fig. 2b, c)

Summary

Introduction

We have previously shown that the grape bioactive compound resveratrol (RSV) potentiates grape seed extract (GSE)-induced colon cancer cell apoptosis at physiologically relevant concentrations. We previously reported that RSV suppressed proliferation and induced apoptosis via p53 activation in HT-29 and SW-480 human colon cancer cell lines, it was effective only at higher concentrations (75–100 μM) [7]. Our previous studies support this notion, as we demonstrated using a well-established combination index method that a RSV (~25 μM) and GSE (35–50 μg/ml) mixture was potent in suppressing proliferation and elevating apoptosis in the HCT-116 human colon cancer cell line at lower concentrations compared to RSV or GSE alone [10, 11]. Our preliminary results led us to believe that a combinatorial approach towards colon cancer chemoprevention using bioactive compounds is a feasible strategy

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Discussion

Conclusion