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Dartmouth researchers used this experimental design to show how heating iron oxide nanoparticles may be the newest treatment for metastatic cancer. Credit: Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center.

Iron oxide nanoparticles aren’t new to the scene of cancer therapy.

But Dartmouth researchers have heated things up with a new study published online last week in the journal Nanomedicine: Nanotechnology, Biology and Medicine.

The scientists used an alternating magnetic field to heat iron oxide nanoparticles injected directly into a mouse tumor, warming the nanoparticles to 43°C for just half an hour. While you can imagine how heat kills local cells, the results show something more interesting is going on.

In a Dartmouth University press release, senior author and Dartmouth genetics professor Steven Fiering says, “The study demonstrates that controlled heating of one tumor can stimulate an immune response that attacks another tumor that has not had the heat treatment. This is one way to try to train the immune system to attack metastatic tumors that may not be recognized yet.”

The results show directed heat therapy to just one localized tumor in a mouse generates a whole body-wide immune response to those cancer cells. In this system, the lynchpin of the immune response is activation of CD8+ cells, otherwise known as killer T cells. Killer T cells are white blood cells that live up to their name—they’re kind of like tiny policemen in your blood, trolling for bad guys (e.g., cancer cells, virus-infected cells, or otherwise damaged cells) and taking them out.

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Schematic diagram of how the immune response, particularly CD8-positive T cells, mediates anti-tumor effects in local and distant tumors. Credit: Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center.

So treating a tumor to hot iron oxide nanoparticles helps kill the localized tumor, but also posts “mug shots” so that the rest of the immune system can recognize the bad guy and his accomplices. The response shows the immune system what to look for, allowing even distant immune cells to recognize rogue cancer cells and take them out. These new results are some of the latest in a promising new field of cancer research called cancer immunotherapy, which tries to harness the killing power of the body’s own immune system to fight cancer.

The precise temperature of the nanoparticles was important for the Dartmouth researchers’ results, which is why iron oxide nanoparticles could have a big role in the future of tumor therapy. The nanoparticles and magnetic field allowed the scientists to precisely control what was happening in the tumor, allowing fine-tuning to find that cancer-killing sweet spot.

The developments are an exciting advance for the treatment of metastatic cancer. Metastasis occurs when tumor cells wander away from a tumor and find their way into the circulatory system, allowing the spread of cancer to distant sites. Metastatic cancer is difficult to treat and often signals the end for cancer patients, because no current treatments can efficiently tackle nomadic cancer cells. Let’s hope this new development can help change that.

The paper is “Local Hyperthermia Treatment of Tumors Induces CD8+ T cell-Mediated Resistance Against Distal and Secondary Tumors” (DOI: 10.1016/j.nano.2014.01.011).