How Does Paclitaxel Work as a Cancer Medicine?

Paclitaxel is an important anti-cancer drug that stabilizes microtubules, causing dividing cancer cells to arrest in mitosis and eventually die. If we could understand the principles by which this effective, but toxic, drug acts, we might be able to design better future drugs. Paclitaxel and other cytotoxic chemotherapy drugs are thought to gain their selectivity from tumor cells proliferating faster than normal cells, yet the reality is that most human tumors grow slowly, with infrequent divisions. Using intravital imaging to visualize dividing cells in living mice, Dr. Mitchison and his colleagues have been comparing how paclitaxel kills cancer cells in tissue culture and model mouse tumors. They have found that the mitotic death mechanism seen in culture does occur in a subset of tumor cells, but it is not sufficient to explain the overall tumor response. The scientists are investigating how paclitaxel may cause a change in the tumor environment to promote regression.