Natural products to prevent drug resistance in cancer chemotherapy: a review

Chemotherapy is the standard internal medical treatment for cancer. However, the resistance of cancer cells to nearly all kinds of chemotherapeutic drugs and targeted drugs has become prevalent, and approximately 80-90% of deaths in cancer patients are directly or indirectly attributed to drug resistance. The progress of new drug research and development has also been impeded by the occurrence of drug resistance, which has emerged as a considerable challenge in cancer therapy. Fortunately, natural products with diverse chemical structures and pharmacological effects serve as effective substances against drug resistance. Since the discovery of a series of drug-resistant proteins, drug-efflux inhibition has been applied as the primary strategy to overcome drug resistance by maintaining the intracellular concentrations of chemotherapeutic drugs. Nonapoptotic cell death is considered an alternative strategy because most cases of drug resistance result in evasion and insensitivity to apoptosis. In this concise review, we summarize two strategies using natural products against drug resistance.