Study On 7-xylosyl-10-deacetylpaclitaxel Antitumor Activity And Mechanism

Water decoctions from the leaves of Taxus.cuspidata are used in traditional chinese medicine to treat cancer,indicating that water soluble constituents of this tree may indeed possess anticancer activity.In an effort to search for natural products from Taxus.cuspidata with improved pharmacological features compared to paclitaxel,7-xylosyl-10-deacetylpaclitaxel has been isolated and identified by our group.This is a naturally occurring xyloside,which has been shown to possess higher water solubility than paclitaxel.The mode of action of 7-xylosyl-10-deacetylpaclitaxel is scarcely known as of yet.So 7-xylosyl-10-deacetylpaclitaxel was first time systematicly studied on antineoplsamic activity and mechanism,and the results showed that:1.We first time discovered that inhibitory rate of 7-xylosyl-10-deacetylpaclitaxel was similar to that of paclitaxel through calculating S-180 tumor weight in mice via v.i(Inhibitory rate of 7-xylosyl-10-deacetylpaclitaxel was 68.2%,inhibitory rate of paclitaxel was 59.4%).2.A simple,rapid and sensitive liquid chromatography-mass spectrometry(LC-MS /MS) method for quantitating 7-xylosyl-10-deacetylpaclitaxel and paclitaxel in rat plasma was established.Approximating 500ng/mL 7-xylosyl-10-deacetylpaclitaxel was first time determinated in rats plasma after v.i.administration of 2.5mg/kg 7-xylosyl- 10-deacetylpaclitaxel.3.Antitumor activity of 7-xylosyl-10-deacetylpaclitaxel was first time determinated in MCF-7,A549,CEM,PC-3 human cancer cells through MTT method.And PC-3 human prostate cancer cells were sensitive to 7-xylosyl-10-deacetylpaclitaxel(48h IC₅₀:5μM,72h IC₅₀:586nM).4.We first time discovered that 7-xylosyl-10-deacetylpaclitaxel induced PC-3 human prostate cancer cells apoptosis as measured by flow cytometry,DNA laddering,laser confocal microscopy,transmission electron microscopy and atomic force microscopy.5.We first time discovered that pathway of 7-xylosyl-10-deacetylpaclitaxel-triggered apoptosis in PC-3 human prostate cancer cells:an up-regulation of pro-apoptotic Bax and Bad protein expression and a down-regulation of anti-apoptotic Bcl-2 and Bcl-X_L expression,which lead to a disturbance of the mitochondrial membrane permeability and to the activation of caspase-9.In turn, caspase-9 activated downstream caspases-3 and -6,but not caspase-8.Bid was also activated by caspase-3.Reversely,treatment with a caspase-10-specific inhibitor could not protect PC-3 cells from 7-xylosyl-10-deacetylpaclitaxel-triggered apoptosis. Moreover,7-xylosyl-10-deacetylpaclitaxel had no effect on the expression of CD95 and NF-κB proteins,indicating that apoptosis was induced through the mitochondrial-dependent pathway in PC-3 cells.The pathway of 7-xylosyl-10-deacetylpaclitaxel-triggered apoptosis was different to the pathway of paclitaxel-triggered apoptosis.In summary,Systematic study on antitumor activity and mechanism of 7-xylosyl-10 -deacetylpaclitaxel established substantial basis to develop new drug.