New Cancer Vaccine Experiment Involving Glioblastoma in Mice
Researchers recently tested a new combination therapy for cancer on mice that had a specific kind of brain tumor called glioblastoma. The two combined therapies were an anti tumor vaccine with what is called a checkpoint inhibitor. These inhibitors block proteins that the cancer cell needs to survive and thereby help control its growth. The researchers found that when used in combination, the therapy was effective in prolonging survival of the mice, while either of the therapies alone had no such effect.
Past studies have suggested that tumors use the molecules at these checkpoints in order to grow accustomed and resistant to vaccines, so inhibiting them is key to stopping tumor growth.
Glioblastoma is a particularly aggressive brain cancer, with most people who are diagnosed dying around a year after starting vaccinations. Better vaccines against this tumor are now in trials, but survival rates have varied widely.
Treating cancers like this one is difficult because tumors are good at protecting themselves from the therapies we try to use to combat them. Cancer grows quickly so its cells have the constant opportunity to grow resistant to the immunotherapies or anything else that might threaten their survival.
Studies have indicated that tumors are getting better at hijacking the checkpoint molecules that have been used to stop their growth, which is of great concern because many combination and checkpoint inhibitor therapies could become worthless in the fight against these evolving tumors.
Even when the vaccine by itself triggers an immune response, it is of little use in fighting glioblastoma that has already infiltrated the brain. The only inhibitor that is of use at this late stage is a molecule called PD-1. So the researchers in this study added a PD-1 blocker, and this improved the results of the vaccine by increasing long term survival by forty percent. It appeared that this blockade activated more T cells, which are the cells that fight cancer. Further research on PD-1 showed that the vaccine may have the same potential in humans.