A New Weapon Against Cancer: Implanted Disks

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Tiny plastic disks impregnated with tumor-specific antigens and implanted beneath the skin can prompt the mammalian immune system to attack tumors, according to bioengineers at Harvard University.

In what represents the most effective demonstration to date of a cancer vaccine, researchers report that an aggressive melanoma that normally kills rodents within 25 days was eliminated in 90 percent of mice. The research is described in the journal Nature Materials.

"Our immune systems work by recognizing and attacking foreign invaders, allowing most cancer cells — which originate inside the body -- to escape detection," David J. Mooney, Gordon McKay professor of bioengineering in Harvard's School of Engineering and Applied Sciences, was quoted in a press release announcing the study. "This technique, which redirects the immune system from inside the body, appears to be easier and more effective than other approaches to cancer vaccination."

Most previous research on cancer vaccines has involved removing immune cells from the body, reprogramming them to attack malignant tissues, and then reinjecting these altered cells into the body. Although this approach should work in theory, in experiments more than 90 percent of the reinjected cells perish before having any impact.

The implants created by Mooney and his colleagues are slender disks, about 8.5 millimeters across, made of an FDA-approved biodegradable polymer. They work much like the implantable contraceptives that can be inserted subcutaneously into a woman's arm. Because the disks are 90 percent air, they are highly permeable to immune cells. They release cytokines, powerful attractants of immune-system messengers called dendritic cells, which enter an implant's pores and are exposed to tumor-specific antigens. The dendritic cells then report to nearby lymph nodes, where they activate the immune system's T cells to track down and destroy tumor cells throughout the body.

The implants could also be loaded with bacterial or viral antigens to safeguard against several different infectious diseases or conditions such as type 1 diabetes, which occurs when immune cells attack insulin-producing pancreatic cells.
In the Nature Materials article, Mooney and his co-authors write:

"This study demonstrated a powerful new application for polymeric biomaterials that may potentially be used to treat a variety of diseases by programming or reprogramming host cells. The system may be applicable to other situations in which it is desirable to promote a destructive immune response (for example, eradicate infectious diseases) or to promote tolerance (for example, subvert autoimmune disease)."

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