Injection helps the immune system obliterate tumors, at least in mice

Our immune cells can destroy tumors, but sometimes they need a kick in the pants to do the job. A study in mice describes a new way to incite these attacks by injecting an immune-stimulating mixture directly into tumors. The shots trigger the animals’ immune system to eliminate not only the injected tumors, but also other tumors in their bodies. 

To bring the wrath of the immune system down on tumors, researchers have tried shooting them up with a variety of molecules and viruses. So far, however, almost every candidate they’ve tested hasn’t worked in people.

Hoping to develop a more potent approach, medical oncologist Ron Levy of Stanford University in Palo Alto, California, and colleagues used mice to test the cancer-fighting capabilities of some 20 molecules, including several types of antibodies that activate immune cells.

The researchers first induced tumors by inserting cancer cells just below the skin at two different locations on the animals’ abdomens. After tumors started growing at both sites, the scientists injected the molecules, alone or in combination, into one tumor in each mouse. They then tracked the responses of both tumors.

A pair of molecules-a type of DNA snippet called CpG and an antibody against the immune cell protein OX40 – produced the best results. “On their own, they do almost nothing, but the combination is synergistic,” Levy says. When the researchers injected the two molecules into mouse tumors, they disappeared in less than 10 days. In less than 20 days, the noninjected tumors had also vanished.