Eugenol enhances the chemotherapeutic potential of gemcitabine and induces anticarcinogenic and anti-inflammatory activity in human cervical cancer cells

Administration of natural or synthetic agents to inhibit, delay, block, or reverse the initiation and promotional events associated with carcinogenesis opens a new avenue for cancer prevention and treatment to reduce cancer morbidity and mortality. Eugenol, a potential chemopreventive agent, is a component of clove and several other spices such as basil, cinnamon, and bay leaves. A number of reports have shown that eugenol possesses antiseptic, analgesic, antibacterial, and anticancer properties. The present study was undertaken to evaluate the chemopreventive potential of eugenol alone and in combination with a chemotherapeutic agent such as gemcitabine. Eugenol showed dose-dependent selective cytotoxicity toward HeLa cells in comparison to normal cells, pointing to its safe cytotoxicity profile. A combination of eugenol and gemcitabine induced growth inhibition and apoptosis at lower concentrations, compared with the individual drugs. The analysis of the data using a combination index showed combination index values of <1 indicating strong synergistic interaction. The combination thus may enhance the efficacy of gemcitabine at lower doses and minimize the toxicity on normal cells. In addition, the expression analysis of genes involved in apoptosis and inflammation revealed significant downregulation of Bcl-2, COX-2, and IL-1β on treatment with eugenol. Thus, the results suggest that eugenol exerts its anticancer activities via apoptosis induction and anti-inflammatory properties and also provide the first evidence demonstrating synergism between eugenol and gemcitabine, which may enhance the therapeutic index of prevention and/or treatment of cervical cancer.