A team of researchers from UNC Chapel Hill just made an intriguing and potentially revolutionary announcement: By using the body's own "exosomes," they have not only developed a powerful new way to diagnose cancer, but a sort of invisibility cloak that can help keep chemotherapy drugs safe in the patient's system. The team's research shows(Opens in a new window) that by using one of the body's own natural structures to hide their chemotherapeutic drugs, they were able to have normal therapeutic effects with about a fiftieth of the overall dose.
What is an exosome? It's a bit of cell membrane that has "budded" off from the cell itself, basically pinched off by a little protein lasso into a much, much smaller little cell with little, or a specific list of things, inside of it. Exosomes are used to ferry signaling molecules between cells, to eliminate wastes, even as a crude way of getting rid of unwanted cell surface proteins -- just throw them off.
Recently, there's been an explosion of research into how exosomes could be used to deliver drugs -- they are, after all, the body's own molecular-delivery vehicles. Most excitingly, there has been progress in using exosomes to cross the much-maligned blood-brain barrier, which makes the delivery of drugs to the brain far more difficult. In fact, some of the same researchers from the UNC Chapel Hill team have published research on hijacking this property of exosomes to attack Parkinson's.
In that case, it's the fact that the body is expecting exosomes, and lets them pass as friendlies, that could revolutionize brain medicine -- in this case, it's the same property that could revolutionize cancer treatment. Exosomes have to be at least somewhat safe in the bloodstream, since you can't run a successful business if your security guards are constantly attacking your mailroom guys.
Chemotherapeutic drugs are often very fragile on a molecular level, and if they're injected on their own, they can't even get close to the area of the body where they're actually needed. Recently, there's been a ton of research into using plastic, biopolymer, or even DNA-based shells to keep those molecules safe while they're in transit. These earlier approaches basically equate to delivering your drug inside a Brinks truck; the UNC Chapel Hill team's approach acts more like a cloaking device. The team calls it exoPXT.
The results of doing it that way are impressive, if they can be replicated going forward. The team tested their therapy both in cell cultures and in mouse models -- in both cases, they found that the delivery mechanism meant they had to inject about 50 times less chemotherapeutic agent to get the same therapeutic effect. Not only could that lessen the negative side-effects experienced by patients, many of which result from the body's well-meaning breakdown of chemo-agents, but it could make viable therapies from drugs that would otherwise be too nonspecifically toxic to the body to work.
Staining tissues with dyes like this can show you were disease cells are building up -- but it's hard to do in a living body.
The team found that if they dye the exosomes to track their progress through the body, the exosomes cluster specifically at the sites of their mouse's lung tumors. This could allow an easy way of locating the full extent of lung cancers, which are often difficult to map. The team admits they don't fully understand the mechanism of the cancer-targeting, but it seems to go on by a different mechanism than most cell-targeting, since their therapy was widely unaffected by the forms of drug resistance they tested.
In his most recent State of the Union, President Obama announced a sort of War on Cancer, saying that we could see space race-like levels of advancement if we make space race-like levels of investment. This study is by necessity quite limited, studying the reaction of lung cancer to the delivery of just one drug. But it's just the sort of innovative approach that could allow an explosion of new treatments to be developed.Tagged In
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