So, we’re 42 years into the War on Cancer, and while the enemy remains formidable, our strategy is shifting into yet another phase. We’ve been through the equivalent of hand-to-hand combat–surgery–carpet bombing–radiation–and chemical warfare–chemotherapy. Now the fight is about stealth. Instead of concentrating on blasting away at cancer cells, or poisoning them, you’re more likely to hear cancer scientists talk about “Trojan horses” or “cloaking strategies” or “tricking” the immune system. All are cell-level ploys hatched through nanomedicine–medical treatment gone very, very small. How small? At the nano level, about 5,000 particles would be as wide as a human hair. Okay, so we’re in beyond comprehension territory here. But let’s not get hung up on size; let’s focus on deception. The latest example of microscopic trickery was laid out last week a paper from researchers at the University of Pennsylvania. One of the most appealing aspects of nanomedicine is that it allows scientists to deliver drugs directly to a tumor instead flooding the whole body with chemotherapy. Unfortunately, the immune system sees the nanoparticles as invaders and tries to clear them away before they can go to work on the tumor cells.
The trick was to make the “sentry cells” of the body’s immune system think that the drug-delivering nanoparticles were native cells, that they weren’t intruders. The researchers did this by attaching to each nanoparticle a protein that’s present in every cell membrane. And put simply, it sent out a “don’t eat me” message to the body’s guard cells. The result, at least in mice, is that this technique dramatically improved the success rate of two different kinds of nanoparticles–one that delivered tumor-shrinking drugs and one filled with dye that would help doctors capture images of cancer cells. Meanwhile, earlier this year, scientists at the Methodist Hospital Research Institute in Houston announced that they had found their own way of letting nanoparticles fool the immune system. They developed a procedure to physically remove the membranes from active white blood cells and drape them over nanoparticles. And that “cloaking strategy” was enough to keep proteins that activate the immune system from doing their job and ordering it to go repel the invaders. The researchers believe it will one day be possible to harvest a patient’s own white blood cells and use them to cloak the nanoparticles, making it that much more likely that they’ll get to their target without being attacked. As magical as all this can sound, nanomedicine is not without risk. Much more research needs to be done on the long-term impact of nanoparticles inside the body. Could they accumulate in healthy body tissues? And if they do, what effect would it have? Can those tiny particles now seemingly so full of promise, eventually turn toxic?
Still plenty of questions about nanomedicine, but it’s feeling more like an answer.