Antitumor activity of 3,5,4′-trimethoxystilbene in COLO 205 cells and xenografts in SCID mice

Resveratrol (R‐3), a trihydroxy trans‐stilbene from grape, inhibits multistage carcinogenesis in animal models. Here we report that 3,5,4′‐trimethoxystilbene (MR‐3), the permethylated derivative of R‐3 was more potent against the growth of human cancer cells (HT‐29, PC‐3, COLO 205) with estimated IC50 values of 81.31,42.71, and 6.25 µM, respectively. We further observed that MR‐3 induced apoptosis in COLO 205 cells through modulation of mitochondrial functions regulated by reactive oxygen species (ROS). ROS generation occurs in the early stages of MR‐3‐induced apoptosis, preceding cytochrome‐c release, caspase activation, and DNA fragmentation. Significant therapeutic effects were demonstrated in vivo by treating severe combined immune deficiency (SCID) mice bearing COLO 205 tumor xenografts with MR‐3 (50 mg/kg ip). Assays on DNA fragmentation and caspase activation were performed and demonstrated that apoptosis occurred in tumor tissues treated with MR‐3. The appearance of apoptotic cells, as shown by Hematoxylin and Eosin (H&E) staining, and an increase in p21 and decrease in proliferating cell nuclear antigen (PCNA) protein by immuno‐histochemistry were observed in tumor tissues under MR‐3 treatment. Our study identifies the novel mechanisms of the antitumor effects of MR‐3 and indicates that these results may have significant applications for cancer chemotherapy. © 2007 Wiley‐Liss, Inc.