Preclinical Development of Anti-Cancer Drugs from Natural Products.

Abstract

Cancer has been and will continue to be the common concern in the United States and worldwide. As a conventional treatment to fight cancer, new anti-cancer drugs with more efficiency and less toxicity are extremely required. In this study, we have identified two novel compounds with anti-cancer properties from two traditional Chinese medicinal plants. One is Lappaol F that was extracted from the seeds of the plant Actium Lapp L., which has been used in China for centuries as anti-viral and anti-bacterial medicine. Another is M-9 that was extracted from the stem of Marsdenia tenacissima,a plant that has been applied to treat inflammation and cancer in China. Our results showed that Lappaol F inhibited cancer cell growth by regulating a series of cell cycle related proteins and inducing cell cycle arrest at G1 and/or G2 phase. p21 played a critical role in Lappaol F-induced cyclin B1 and cyclin-dependent kinase 1 (CDK1) suppression as well as G2arrest. Lappaol F also induced cell death in a number of cancer cells through caspases activation. Lappaol F-mediated cell growth inhibition was p53-independent. Notably, results from animal studies showed that Lappaol F effectively inhibited tumor growth in vivo, while being well tolerated by the mice. Thus, Lappaol F has a strong potential to be developed as a novel anti-cancer chemotherapeutic. Our studies showed that M-9 successfully sensitized several tumor cells but not non-tumorigenic cells to paclitaxel (Taxol) treatment. Additionally, M-9 reversed chemotherapeutic resistance in a number of multidrug resistant cells. Further results suggested that M-9 functioned, at least to a certain extent, via inhibiting drug efflux by competitively binding to P-glycoprotein (P-gp), a protein that accounts for multidrug resistance. Importantly, results from the in vivostudies demonstrated that M-9 strongly enhanced Taxol-induced growth suppression against xenografts derived from HeLa cells. Moreover, mice tolerated the treatment of Taxol and M-9 well. Therefore, M-9 is a novel chemosensitizer candidate to overcome P-gp-mediated multidrug resistance. Taken together, our studies provide a solid basis for further development of these two compounds as anti-cancer remedies.