Biol. Pharm. Bull. 28(1) 138—142 (2005)

(THM) being used clinically as complementary medicine or alternative medicine is increasing. As well as this increase in popularity of THM in clinical situations, the co-administration of THM and drugs (manufactured chemicals) has also increased remarkably. Especially in cancer chemotherapy, it is true that the incidence of co-administration of THM and anticancer drugs is high. However, there is little information about the effects of THMs on the action of anticancer drugs, but many patients are exposed instead to an intensive bombardment by the information coming from the sources of socalled complementary medicine or alternative medicine. On the other hand, the development of multidrug resistance (MDR) to anticancer drugs remains a major hurdle to successful cancer chemotherapy. Although the cellular basis underlying MDR is not fully understood, several factors have been identified. These include down-regulation of uptake, induction of the efflux system (MDR1/P-glycoprotein etc.), induction of inactivation enzymes (glutathione-S-transferase etc.), alteration of the targeted molecule (topoisomerase etc.), changes in DNA repair processes, alteration of the apoptotic mechanism (p53 mutation, bcl-2 overexpression etc.). The overexpression of MDR1/P-glycoprotein in tumor cells is known to be one of the best-characterized mechanisms of MDR. The final goal of our research is to introduce a means of reversing MDR. If some THMs are capable of reversing MDR, these may contribute to the improvement of clinical outcomes in cancer chemotherapy. Therefore, in the beginning, it is necessary to examine the effects of major THMs on the sensitivity to anticancer drugs of tumor cells. This may create a base for providing both patients and doctors as well with warnings and a valuable information, respectively. In this study, nineteen kinds of herbs were chosen from the ingredients of major THMs, and their effects on the sensitivity to anticancer drugs of tumor cells were investigated using the human cervical carcinoma cell line HeLa. Focusing on the major mechanism for MDR, i.e., MDR1, the effects of herbal extracts on its transport function were also examined using Rhodamine123, which is a MDR1 substrate.