Phase I Biomarker Study of Dietary Grape-derived Low Dose Resveratrol for Colon Cancer Prevention

It has long been recognized that dietary factors influence the risk of developing colon cancer, with populations consuming a higher proportion of fruits and vegetables having lower risk. A compound found in the skin of grapes, resveratrol, has been purported to have colon cancer prevention activity though the dosages obtained through the diet have always seemed too low to produce inhibitory effects against cancer cells in the laboratory. We have found that low concentrations of resveratrol inhibit the Wnt pathway, a key signaling pathway which is activated in over 85% of colon cancers. We have also found in a small pilot trial that low dosages of freeze-dried grape powder can directly inhibit Wnt signaling in the normal colon and that grape powder was more effective than resveratrol alone in blocking Wnt throughput. This suggests that components of grapes may have direct activity in inhibiting a key signaling pathway and that this may correlate with cancer prevention activity.

In this study, we will directly test the impact of a diet containing a specific amount of red grapes in the context of a controlled amount of other resveratrol containing foodstuffs on Wnt signaling in the colon. This grape-supplemented diet provides a low-dose of resveratrol in conjunction with other potentially active components contained within the grapes. Participants will be normal volunteers and molecular studies will be done on colon tissue obtained by a limited flexible sigmoidoscopy before, and after, the red grape-containing diet is ingested. Different dosages of grapes will be utilized. This study will define the effect of dietary grape-derived low dose resveratrol on biomarkers related to the Wnt pathway, and provide critical information as to the utility of this nutritional approach toward colon cancer prevention.

For this study, seedless red grapes will be used. Ten participants will be enrolled at each dose level of grapes as follows:

Dose level 1: 1 lb/day fresh red grapes
Dose level 2: 2/3 lb/day fresh red grapes
Dose level 3: 1/3 lb/day fresh red grapes

Participants will be normal volunteers identified through advertisements, referrals, and community outreach.

Primary Objective:

Define the minimum dietarily achievable amount of resveratrol-rich fresh red grapes which are effective in inhibiting Wnt signaling in human colonic mucosa.

Secondary Objectives

Define whether grape-supplemented diet affects colonic mucosa cell proliferation.
Define any side-effects associated with the resveratrol-rich dietary program.