Podophyllotoxin

Podophyllotoxin, a kind of non-alkaloid toxin lignan extracted from the roots and rhizomes of Podophyllum plant, has been shown to inhibit the growth of various carcinoma cells. Podophyllotoxin is a natural product that inhibits the polymerization of tubulin and has served as a prototype for the development of diverse antitumor agents in clinical use.

Apoptosis of human gastric cancer SGC-7901 cells induced by podophyllotoxin.[Pubmed:24940431]

Exp Ther Med. 2014 May;7(5):1317-1322.

Numerous studies have demonstrated that Podophyllotoxin and its derivatives exhibit antitumor effects. The aim of the present study was to investigate SGC-7901 cell apoptosis and the underlying mechanism induced by Podophyllotoxin. SGC-7901 cells were treated with varying concentrations of Podophyllotoxin. MTT assays and flow cytometry were used to evaluate the effects of Podophyllotoxin on the proliferation and apoptosis of SGC-7901 cells, while fluorescence inverted microscopy was used to observe the morphology of SGC-7901 cells that had been dyed with Hoechst 33258. In addition, laser scanning confocal microscopy was used to analyze the mitochondrial membrane potential (MMP) of SGC-7901 cells dyed with Rhodamine 123. Western blotting was performed to analyze the expression levels of cytochrome c (cyt-c), caspase-9 and caspase-3 in the SGC-7901 cells. The results indicated that Podophyllotoxin was capable of inhibiting growth and inducing the apoptosis of SGC-7901 cells in a dose-dependent manner, causing cell cycle arrest at the G2/M phase. After 48 h of treatment, the apoptotic morphology of SGC-7901 cells was clear, exhibiting cell protuberance, concentrated cytoplasms and apoptotic bodies. Following 24 h of treatment, the MMP of the SGC-7901 cells decreased. In addition, after 48 h, the expression of cyt-c was shown to be upregulated, while the expression levels of pro-caspase-9 and pro-caspase-3 in the SGC-7901 cells were shown to be downregulated. In conclusion, apoptosis can be induced in SGC-7901 cells by Podophyllotoxin, potentially via a mitochondrial pathway, indicating that Podophyllotoxin may be a potent agent for cancer treatment.

Recent developments towards podophyllotoxin congeners as potential apoptosis inducers.[Pubmed:25469512]

Anticancer Agents Med Chem. 2015;15(5):565-74.

Podophyllotoxin, a lignan extracted from rhizomes of Podophyllum species, is a well established lead in the development of new chemical agents for the treatment of cancer. Its semi-synthetic variant, etoposide is an anticancer drug which inhibits DNA topoisomerase II causing cell cycle arrest in the S the phase. Its clinical success and intriguing mode of action made it a much sought after skeleton for the development of better antitumor agents. Modifications were made at several positions of its skeleton with the aim to either improve its potency or to overcome drug resistance. In recent years, the structurally modified Podophyllotoxins have been investigated for their apoptosis inducing ability. Although numerous reviews emphasized the occurrence, synthesis and applications of Podophyllotoxins, the recent progress towards development of structurally modified Podophyllotoxins possessing apoptosis inducing ability has not been previously reviewed. Therefore the present review focuses on the studies carried out in the design and synthesis of new Podophyllotoxin derivatives and their evaluation as apoptosis inducers.

Antitumor properties of podophyllotoxin and related compounds.[Pubmed:11102564]

Curr Pharm Des. 2000 Dec;6(18):1811-39.

The lignan family of natural products includes compounds with important antineoplastic and antiviral properties such as Podophyllotoxin and two of their semisynthetic derivatives, etoposide and teniposide. The latter are included in a wide variety of cancer chemotherapy protocols. Due to these biological activities, lignans, and especially cyclolignans, have been the objective of numerous studies focused to prepare better and safer anticancer drugs. The mechanism by which Podophyllotoxin blocks cell division is related to its inhibition of microtubule assembly in the mitotic apparatus. However, etoposide and teniposide were shown not to be inhibitors of microtubule assembly which suggested that their antitumor properties were due to another mechanism of action, via their interaction with DNA and inhibition of DNA topoisomerase II. Other Podophyllotoxin derivatives has also been reported which retained or even improved the cytotoxic activity, but these were weak inhibitors of topoisomerase II in vitro; the data revealed that such analogs exhibit a different, as yet unknown, mechanism of action. The main deficiency of these compounds is their cytotoxicity for normal cells and hence side effects derived from their lack of selectivity against tumoral cells. In this regard it is necessary to investigate and prepare new more potent and less toxic analogs, that is, with better therapeutic indices. It is well accepted from structure-activity studies in this field that the trans-lactones are more potent as antineoplastics than the cis-lactones. Not only the configuration of the D ring is an important factor for high cytotoxic activity, but also a quasi-axial arrangement of the E ring is necessary. On this basis, studies on lignans have been addressed to modify the lactone moiety and prepare analogs with heteroatoms at different positions of the cyclolignan skeleton. Our group has been working during the last few years on chemical transformations of Podophyllotoxin and analogs and we have prepared a large number of cyclolignan derivatives some of which display potent antiviral, immunosuppressive and cytotoxic activities. We have reported several new cytotoxic agents with nitrogen atoms at C-7 or C-9 or at both C-7 and C-9: imine derivatives, oxime derivatives, pyrazoline-, pyrazo- and isoxazoline-fused cyclolignans. At present, we are preparing mainly new compounds by modifications of the A and E cyclolignan-rings. They are being tested on cultures of different tumoral cell lines (P-388 murine leukemia, A-549 human lung carcinoma, HT-29 human colon carcinoma and MEL-28 human melanoma) and some of them have shown an interesting and selective cytotoxicity.