Optimized combinations of bortezomib, camptothecin, and doxorubicin show increased efficacy and reduced toxicity in treating oral cancer

Oral cancer continues to be a major cause of morbidity and mortality worldwide. Treatment of oral cancer with combinatorial drugs is increasingly being performed as drugs with different molecular targets often exert synergistic effects, thereby enhancing treatment efficacy. Current combinatorial drug regimens often combine the tolerable dosages of individual drugs. However, the optimized ratio of a drug combination and sequence of drug administration could contribute toward the synergy, leading to increased efficacy and reduced dosages. This report aims to study the possible synergistic effects of three anticancer drugs, a proteasome inhibitor, bortezomib, a topoisomerase I inhibitor, Camptothecin, and a DNA intercalation drug, Doxorubicin, when used in combination for treating oral cancer. To rapidly optimize the three-drug regimen with minimal experimental efforts, a Feedback System Control optimization technique, a recent platform technique developed particularly for drug combination screening, was applied. The optimized regimen showed a therapeutic window (death rate difference between cancer cells and normal cells) close to 100%. This is the first report on the use of a combination of bortezomib, Camptothecin, and Doxorubicin in the treatment of oral cancer. Our results indicate that to have the most synergistic anticancer effect, the drugs in the optimized regimen should be dosage specific and ratio specific. Furthermore, the sequence of drug administration plays a vital role in ensuring that the combination is effective. The optimized regimen reported here has the potential to considerably increase the cure rate of oral cancer and reduce the toxicity of chemotherapy.