Studies On The Antitumor Activity Of Three Kinds Of Natural Compounds

Tumor is one of the principle diseases that seriously threaten human health. In 2000, compared with that in1950 by American Tumor Association, the mortality of some diseases including angiocardiopathy, cerebrovascular diseases, pneumonia and some infectious diseases was decreased greatly except for tumor. Thus, finding the high effective antitumor-drugs with low toxicity is the most important task in medical field.The objective of the work described in this Ph. D thesis is to find active compounds which have low toxicity, high selectivity and good inhibition to cancer cells from three kinds of natural compounds, and the mechanism of the active compound.In first part of the thesis, the anti-tumor effects of 63 steroidal saponins were investigated. By using different model cell lines, including NCI-H460, SF-268 and MCF-7, which was NCI recommended, and HepG2 (human hepatoma carcinoma cell line), R-HepG2 (Resist-HepG2 line) as well as QSG-7701 (human normal hepatic cell line), methyl protodioscin (MPD) was found to have significant growth-inhibitory effect on the five tumor cell lines and little toxicity to the normal cells. To investigate its influence on tumor progression in vivo, S180 and Luis lung cancer models were established in Kun Ming species mice and C57BL/6 mice, respectively. As a result, the restrain rate of tumor growth was 30%, which indicated that MPD has considerable effect on intragastric administration. The most effective way of administration was intravenous injection which could increase the restrain rate of tumor growth to 50%, yet intraperitoneal injection has no significant effect on tumor growth. And we also examined the antitumor effect of MPD on HepG2 xenografts in nude mice, and the restrain rate of tumor growth was 37%. Based on the in vivo results, we further investigated the cellular and molecular mechanism of anti-tumor effect of MPD. It was found that MPD could induce HepG2 cell growth arrest at G2/M phase through up-regulating of p21 gene expression and down-regulating of Cyclin B1 expression. It could also promote HepG2 cells apoptosis through up-regulating of Bax and down-regulating of Bcl-2. On the other hand, MPD could inhibit the polymerization of microtubule protein that may conduce to G2/M phase arrest. Moreover, the gene expression profiles of HepG2 cells in response to MPD were examined by high density cDNA microarray, several genes relate to cell cycle, apoptosis and differentiation were found to be differentially expressed upon MPD treatment. Further mechanism needs to be approached.In second par of the thesis, the anti-tumor activities of 23 stilbenes and bibenzyls were investigated by using MTT method. PYB showed better activity than resveratrol, it could induce HepG2 cells apoptosis as well as growth arrest at G2/M phase, which was similar to resveratrol. These effects were attributed to up-regulation of Cyclin B1 and Bax, and cleavage of the substrate of caspase-3, named PARP. Using Matrigel-Boyden chamber method, PYB also showed considerable inhibitory activity on FHCC-98 cells invasion.From the third part of the thesis, among 22 phenanthrene derivatives, compound 4, 5-dihydro-2-methoxy-9, 10-dihydrophenanthrene showed the best anti-cancer activity in vitro and was used to molecular mechanism study. The result suggested that this compound may induce HepG2 cells G2/M arrest by decreasing the level of Cyclin B1, yet showed little effect on apoptosis.In general, the work made the systematic research on anti-cancer mechanism of three kinds of natural products. Among the investigated steroidal saponins, MPD was found to exhibit strong anti-tumor activities both in vitro and in vivo, with low toxicity, which give us a hint for its possibility to be new kinds of anticancer-drugs or health remedy; From the results of investigation on stilbenes and bibenzyls, Phoyunbene showed better activity than resveratrol in vitro, which suggested considerable developmental significance; By studying phenanthrene derivatives, we found that 4, 5-dihydroxy-2-methoxy-9, 10-dihydrophenanthrene not only fill in the blank of this research field but also suggested its new application in the future. The studies of the three types of natural products will make foundation for the development of new anti-tumor drugs and also provide the theoretical evidence for their application on curing cancer diseases.