Overcoming chemotherapy resistance with herbal medicines: past, present and future perspectives

Drug resistance is a major problem in cancer chemotherapy and such resistance may be responsible for treatment failure in 90 % of patients with metastatic cancer. From the research work in the past 30 years, multi-mechanisms responsible for the development of drug resistance have been identified. However, to date single agents that target specific single mechanisms of resistance have not been proven effective. Theoretically, herbs have the potential to target multi-mechanisms of resistance since they contain multiple components and may provide an exciting potential in overcoming drug resistance. The present paper provides an overview of the known mechanisms of resistance and reviews the existing data on herbal medicines (Chinese medicines) as chemosensitizing agents from both the English and Chinese literature. Our review found that certain herbs are capable of inducing strong chemosensitizing effect with various mechanisms, but relevant information useful for development of herbs as viable products for therapeutic use is generally inadequate. Ideas for improving in vitro screening and animal/clinical studies that could enhance future development of herbal product as chemosensitizing agent for the treatment of resistant cancer are also discussed.