US researchers have devised a cancer vaccine that can be implanted on a finger-nail size disk and eliminate tumours in mice.
Reported in the journal Science Translational Medicine, the researchers impregnated plastic disks with tumour-specific antigens and then implanted them under the skin of mice. The vaccine works by reprogramming the immune system to attack tumours.
The study demonstrated that this technology could be used to eradicate melanoma tumours in mice.
Most cancer cells are able to skirt the immune system. The researchers' approach was to redirect the immune system to target tumours, and appears both more effective and less cumbersome than other cancer vaccines currently in clinical trials.
Conventional cancer vaccinations remove immune cells from the body, reprogram them to attack malignant tissues, and return them to the body. However, more than 90% of reinjected cells have died before having any effect in experiments.
The slender implants developed by the group at Harvard University are 8.5mm in diameter and made of an FDA-approved biodegradable polymer. Ninety percent air, the disks are highly permeable to immune cells and release cytokines, powerful recruiters of immune-system messengers called dendritic cells.
These cells enter an implant's pores, where they are exposed to antigens specific to the type of tumour being targeted. The dendritic cells then migrate to nearby lymph nodes, where they direct the immune system's T cells to hunt down and kill tumour cells.
The researchers say that the disk can be inserted anywhere under the skin, much like the implantable contraceptives that can be placed in a woman's arm.
The technique may have advantages over surgery and chemotherapy, and may also be useful in combination with existing therapies. It only targets tumour cells, avoiding collateral damage elsewhere in the body.
The researchers also anticipate that these cancer vaccines will generate permanent and body-wide resistance against cancerous cells, just as an immune system generates long-term resistance to bacteria or viruses, thereby providing durable protection against relapse.