Delivering Cancer A One-Two Punch

The ideal cancer treatment kills tumor cells while leaving normal cells unharmed. Bert Vogelstein, Shibin Zhou, and their coworkers at Johns Hopkins University School of Medicine have achieved that ideal by developing a two-pronged treatment for mice with colorectal tumors (Science 2006, 314, 1308). Their method involves injecting spores of the anaerobic bacterium Clostridium novyi-NT followed by a single dose of a liposome-encapsulated form of the anticancer drug doxorubicin. The bacteria selectively infect the tumors because of the low-oxygen environment, and the liposome-encapsulated doxorubicin is selectively taken up by tumors because they have leaky blood vessels. Neither of these treatments alone is enough to cause the significant tumor regression observed. The key seems to be a bacterial protein dubbed liposomase that enhances the release of doxorubicin by rupturing the liposomes. The researchers believe the effect is general for any liposome-encapsulated chemotherapeutic.