The Study Of The Biological Function Of Pu-erh Tea In Adjuvant Chemotherapy

Due to the fast proliferation of the tumor cells, DNA replication is much more active in tumor cells than in normal cells, which has become the major target for chemotherapy. In clinical practice, preventing DNA from replicating has become the main target of chemotherapeutics, such as cisplatin and its derivatives, cyclophosphamide and doxorubicin, which are genotoxic compounds. However, these chemotherapeutics can also damage the DNA of normal cells, especially the hernatopoietic stem cells. Thus cancer patients receiving chemotherapy usually manifest serious side effects. Reducing the side effects of chemotherapy has become an important issue in clinical practice.Pu-erh tea is produced in the Yunnan province, southwest part of China. The most important process of Pu-erh preparation is the step of fermentation. Modern biomedical research has shown that Pu-erh tea is believed to have anti-obesity and anti-inflammatory effect. In fact, its hypolipidemic function, hypoglycemic function, and antioxidative properties have also been demonstrated. Recent study also showed that Pu-erh tea has anti-tumor activity. Thewater extracts of Pu-erh tea could induce cellular apoptosis in tumor cells but not in control wild type cells.Heat shock protein (HSP) plays an important role in the process of cellular stress response (such as heat, UV radiation, chemical drugs, etc.), so HSP is related with the cell survival or apoptosis. High expression level of heat shock protein in tumor cells facilitates the maintenance and development of tumor, thus HSP has become an important target for anti-cancer therapy. P53plays a pivotal role in response to DNA damage. When cells become genetically damaged, such as the DNA damage, p53can cause cell cycle arrest and lead cells into the repair process. Severely damaged cells will be induced into apoptosis. So the p53status determines the cell fate. However, mutant p53not only lose its normal monitoring function, but also acquires some new features which promote tumor occurrence and development. Mutant p53has also become another important target for anti-cancer therapy.In our recent studies, we accidentally discovered that Pu-erh tea could reduce the expression level of heat shock proteins in wild type cells. This finding made us concerned about the impact of Pu-erh tea on cell survival after DNA damaged by chemotherapy drugs. In this study,we will investigate the effect of water extracts of Pu-erh tea on tumor cells and wild type mouse embryonic fibroblasts after treating with chemotherapy drugs.Our results show that normal cells treated with chemotherapy drugs underwent apoptosis seriously. While treated with both Pu-erh tea and chemotherapy drug significantly reduce the cellular apoptosis. Further experiments found that the expression level of the heat shock proteins HSP70/90and p53are significantly lower in the cells treated with Pu-erh tea and the chemotherapy drug together than in cells treated with the chemotherapy drug only. The results suggest that, Pu-erh tea protects normal cells by reducing the expression of heat shock proteins, which makes the sensitivity of normal cells to chemotherapeutic drugs lower. On the other hand, Pu-erh tea increases cell survival by reducing the expression level of p53which mediates cell apoptosis.Next, we studied the impact of Pu-erh tea on tumor cell survival after DNA damaged by chemotherapy drugs. The mouse tumor cell p53-/-+S+Ras and the human breast cancer cell SK-BR-3are used in the study. It was found that Pu-erh tea significantly increased the sensitivity of these two cells to chemotherapeutic drugs. Tumor cells treated with Pu-erh tea and chemotherapy drug together underwent apoptosis more serious than treated with chemotherapy drug only. We also detect that the expression of HSP70/90and p53have no difference in both cases. The results prompted us that the sensitizing effect of Pu-erh tea is not achieved through HSP70/90and p53. The specific mechanism needs further study.In conclusion, we discovered for the first time that Pu-erh tea might be used in adjuvant chemotherapy. In the next step of the research,we will make use of animal models to verify the action of Pu-erh tea in adjuvant chemotherapy.