Pancratistatin causes early activation of caspase-3 and the flipping of phosphatidyl serine followed by rapid apoptosis specifically in human lymphoma cells
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Recently a major research effort has been focused on the development of anticancer drugs by targeting the components of a biochemical pathway to induce apoptosis in cancerous cells. Some of the natural products (e.g. paclitaxel) have been proven to be useful in inducing apoptosis in cancer cells with limited specificity. Pancratistatin, a natural product isolated and characterized over a decade ago, has been shown to be cytostatic and antineoplastic. We investigated the specificity and biochemical mechanism of action of pancratistatin. Pancratistatin seemed to show more specificity than VP-16 or paclitaxel as an efficient inducer of apoptosis in human lymphoma (Jurkat) cells, with minimal effect on normal nucleated blood cells. Caspase-3 activation and exposure of phosphatidyl serine on the outer leaflet of the plasma membrane were earlier events than the generation of ROS and DNA fragmentation observed following pancratistatin treatment. This indicates a possible involvement of caspase-3 and plasma membrane proteins in the induction phase of apoptosis. Our results indicate that pancratistatin does not cause DNA double-strand breaks or DNA damage prior to the execution phase of apoptosis in cancer cells. Parallel experimentation with VP-16, a currently used medication for cancer treatment, indicated that VP-16 causes substantial DNA damage in normal non-cancerous blood cells, while pancratistatin does not cause any DNA double-strand breaks or DNA damage in non-cancerous cells. Taken together, our finding that pancratistatin induces apoptosis in cancer cells using non-genomic targets, and more importantly does not seem to have any affect non-cancerous cells, presents a significant platform to develop non-toxic anticancer therapies.