Activation of the mitochondria-driven pathway of apoptosis in human PC-3 prostate cancer cells by a novel hydrophilic paclitaxel derivative, 7-xylosyl-10-deacetylpaclitaxel.

Paclitaxel, a natural product originally isolated from Taxus brevifolia, belongs to the most successful anticancer drugs. Nevertheless, its poor water solubility represents a considerable disadvantage in clinical use, and novel derivatives with improved pharmacological features are required. We isolated 7-xylosyl-10-deacetylpaclitaxel from Taxus chinensis, which reveals higher water solubility than paclitaxel. This compound induced mitotic cell cycle arrest and apoptosis as measured by flow cytometry, DNA laddering, and transmission electron microscopy. Pro-apoptotic Bax and Bad protein expression was up-regulated and anti-apoptotic Bcl-2 and Bcl-XL expression down-regulated, 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-deacetyl-paclitaxel-triggered apoptosis. Moreover, 7-xylosyl-10-deacetylpaclitaxel had no effect on the expression of CD95 and NF-kappaB proteins, indicating that apoptosis was induced through the mitochondrial-dependent pathway in PC-3 cells.