A Cancer-Fighting Implant

A polymer disc shrinks tumors in rodents by eliciting an immune attack.

In a new approach to fighting cancer, scientists from Harvard University have engineered an implantable disc designed to attract immune cells and prep them to attack tumors. Mice with melanoma tumors were much more likely to survive if they'd been implanted with the device, and tumors disappeared in up to half of the vaccinated animals, according to research published today in the journal Science Translational Medicine. Researchers believe that the implant elicits a broader immune response than traditional vaccines, and may therefore prove more effective. A startup called InCytu, based in Lincoln, RI, is now developing the technology for human testing.

Cancer killer: A cross section of a polymer matrix designed to prime the immune system against cancer. Immune cells crawl through the pores and are activated by chemical signals and tumor molecules. Credit: Edward Doherty, Omar Ali and Microvision Labs

A number of vaccines for treating different types of cancer are currently being tested in clinical trials, though none has yet been approved by the U.S. Food and Drug Administration. Unlike traditional vaccines, therapeutic cancer vaccines are designed to halt or reverse the course of the disease after it has developed. Gardasil, Merck's vaccine against the human papillomavirus, is considered a preventative cancer vaccine and acts in a similar way to traditional vaccines. It helps prevent the development of cervical cancer by stopping viral infection--but it cannot treat existing cervical cancer.

While cancer vaccines come in several variations, the general approach is to trigger the immune system to recognize and destroy cells bearing a cancer-specific marker. The immune system can be tuned to cancer cells by injecting patients with specific molecules linked to different types of cancer, or by injecting irradiated cancer cells. Scientists have also tried to enhance this process by training the immune cells in a controlled environment outside the body--the cells are isolated from the patient's blood and exposed to cancer-specific molecules. The primed immune cells are then injected back into the patient, where they travel to the lymph nodes and trigger an immune response against the cancer.

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However, a problem with this approach is that few cells survive the transplant process, making it difficult for the lymph nodes to mount a strong immune response. David Mooney and colleagues at Harvard University have developed an approach that allows this carefully controlled immune training to take place inside the body. A polymer scaffold, made of the same material used in biodegradable sutures and other surgical products, is impregnated with cytokines, signaling molecules produced by the immune system that attract immune cells known as dendritic cells."The cytokines diffuse into the tissue and the [dendritic] cells follow the gradient to the material and crawl right into it," says Mooney.