An Example of Targeted Cancer Therapy Using Exosomes

The immediate benefits of targeted systems of cancer treatment are fairly straightforward: if a clinic can deliver cell-killing payloads directly to cancer cells, then far lower doses are necessary. This is why the development of targeting methodologies that can reach and accurately distinguish cancer cells is in many ways more important at the present time than the development of actual therapeutics. There are a lot of existing ways to kill cancer cells, and many can be used in a targeted way, reducing their unpleasant and debilitating side-effects in cancer patients while achieving the same or better outcomes.

The cancer drug paclitaxel just got more effective. For the first time, researchers from the have packaged it in containers derived from a patient's own immune system, protecting the drug from being destroyed by the body's own defenses and bringing the entire payload to the tumor. "That means we can use 50 times less of the drug and still get the same results. That matters because we may eventually be able to treat patients with smaller and more accurate doses of powerful chemotherapy drugs resulting in more effective treatment with fewer and milder side effects."

The work is based on exosomes, which are tiny spheres harvested from the white blood cells that protect the body against infection. The exosomes are made of the same material as cell membranes, and the patient's body doesn't recognize them as foreign, which has been one of the toughest issues to overcome in the past decade with using plastics-based nanoparticles as drug-delivery systems. "Exosomes are engineered by nature to be the perfect delivery vehicles. By using exosomes from white blood cells, we wrap the medicine in an invisibility cloak that hides it from the immune system. We don't know exactly how they do it, but the exosomes swarm the cancer cells, completely bypassing any drug resistance they may have and delivering their payload."

In their experiment, the team extracted exosomes from mouse white blood cells and loaded them with paclitaxel. They then tested the treatment - which they call exoPXT - against multiple-drug-resistant cancer cells in petri dishes. The team saw that they needed 50 times less exoPXT to achieve the same cancer-killing effect as formulations of the drug currently being used, such as Taxol. The researchers next tested the therapy in mouse models of drug-resistant lung cancer. They loaded the exosomes with a dye in order to track their progress through the lungs and found that the exosomes were thorough in seeking out and marking cancer cells, making them a surprisingly effective diagnostic tool in addition to being a powerful therapeutic.



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