Stealth Cell Destroys Cancer
MIT researchers' "nanocell" delivers a toxic double whammy to tumors.
By Tracy Staedter, Technology Review, May/June 2006
A team of MIT biological engineers has created a new method for treating cancer that works like an undercover agent. Disguised as a harmless cell, the researchers' "nanocell" sneaks past the body's immune system and delivers a double dose of toxins inside tumor walls. First, the nanocell shuts down the tumor's vascular network, and then it unwraps a package of cancer-killing drugs. Shutting down the vascular network effectively traps the nanocell -- and the toxins it releases -- inside the tumor.
The nanocell could lead to effective cancer therapies that target diseased cells without harming healthy ones. Such therapies would greatly reduce patients' chances of losing their hair and becoming weak, nauseous, and vulnerable to infection.
Today, the two main types of drugs used to treat cancer are chemotherapy, which destroys cancerous cells, and antiangiogenesis drugs, which shut down a tumor's blood vessels. While each therapy can be effective, both have limitations. Chemotherapeutic agents are highly toxic and destroy both healthy and cancerous cells. As antiangiogenesis drugs shut down a tumor's vascular network, they close off the very paths by which chemotherapy would reach the diseased area. And as the tumor begins to die from lack of nutrients, it goes into a fit of hyperactive blood-vessel production in a last-ditch effort to survive.
"It's logical that you can cut the supply line, but then you want to deliver a payload that takes care of these cells that become roguelike," says team leader Ram Sasisekharan, professor of biological engineering.
Sasisekharan and his colleagues found a way to effectively combine the two drugs. They designed the nanocell as a bubble within a bubble. The outer layer resembles a fat cell, which helps the nanocell sneak by the body's security checkpoints without detection.
About 200 nanometers in diameter, the nanocell can easily slip into the highly porous tumor. Once it's inside, its outer layer automatically releases a drug that completely destroys the tumor's blood vessels in about 30 hours. When the outer shell falls away, the inner bubble is exposed. After it is broken down by the tumor's natural enzymes, the inner bubble unloads a package of toxins designed to seep into the cancer over 15 days. The drugs can't harm nearby healthy cells because the tumor no longer has any blood vessels to transport the toxins beyond its walls.
In lab experiments, the technique kept cancerous mice (those exhibiting melanoma or lung cancer) alive for 65 days. Such mice typically survive up to 28 days with current therapies.
It could be years before this treatment is available for humans, but
the approach represents a radical new way to combine drugs to treat disease.
Sasisekharan and his team are working with the medical community and the
U.S. Food and Drug Administration to develop further experiments to test