A Mastic Gum Extract Induces Suppression of Growth of Human Colorectal Tumor Xenografts in Immunodeficient Mice

Background: We recently reported that ethanol and hexane extracts of the plant product, mastic gum (MG), contain constituents which can induce p53- and p21-independent G 1 -phase arrest followed by apoptosis of human HCT116 colon cancer cells in vitro. Herein, we extended these studies to investigate the in vivo anticancer activity of the hexane extract of MG (He-MG) against human colon tumor. The in vivo anticancer activity of He-MG was assessed in a human colon cancer/immunodeficient mouse model. Materials and Methods: Control and HCT116 tumor bearing SCID mice were injected intraperitoneally with He-MG at different administration schedules and doses ranging from 100 to 220 mg/kg body weight and tumor growth (size) was monitored. Results: He-MG administered at a dose of 200 mg/kg administered daily for 4 consecutive days (followed by 3 days without treatment) inhibited tumor growth by approximately 35% in the absence of toxicity (side-effects) after 35 days. Conclusion: He-MG was found to possess antitumor activity against human colorectal cancer under the experimental conditions of this study. The extent of suppression and toxicity by a specific He-MG dose depends on the schedule of administration.