June 10th, 2015

Many cancer patients survive treatment only to have a recurrence within a few years. Recurrences and tumor spreading are likely due to cancer stem cells that can be tough to kill with conventional cancer drugs. But now researchers have designed nanoparticles that specifically target these hardy cells to deliver a drug. The nanoparticle treatment, reported in the journal ACS Nano, worked far better than the drug alone in mice.

Anti-cancer drugs can often shrink tumors but don't kill cancer stem cells (CSCs). Although CSCs might only make up a small part of a tumor, their resistance to drugs allows them to persist. They can then cause a tumor to regrow or spread cancerous cells throughout the body. Xiaoming He and colleagues wanted to develop a nanoparticle system to overcome these cells' defenses.
The researchers packaged the anti-cancer drug doxorubicin into nanoparticles coated with chitosan, a natural polysaccharide that can specifically target CSCs. Once in the acidic environment of the tumor, the nanoparticles degraded and released the drug. Tests on tiny, tissue-like clumps of both normal and cancer stem cells in vitro and on human breast tumors grown in mice showed the therapy successfully killed CSCs and destroyed tumors. The mice showed no obvious side effects.

Image: After two hours, special nanoparticles accumulated in cancer cells (red and yellow) in mice and destroyed most of the tumor within a day (right).