Brain tumors: Cancer vaccines help the immune system fight back
On a daily basis, the immune system deals with infections, foreign contaminants and damaged cells to keep the body in operating condition. However, cancer – most notably brain cancer – has defense mechanisms that can hide from, or overwhelm, the immune system.
Vaccines may have the potential to overcome those defenses. Two are now in phase III clinical trials at City of Hope for newly diagnosed patients; phase III clinical trials are usually the last step before submitting a new drug to the Food and Drug Administration for approval. Meanwhile, two other vaccines are in the works.
The first vaccine undergoing phase III testing harnesses dendritic cells, a type of white blood cell that has easy access to the brain, to reboot the immune system and boost response against the cancer cells. The other targets a version of the EGFR gene receptor, which is very active in brain tumors, also rebooting the immune system to recognize and respond to cancer cells.
At the same time, Behnam Badie, M.D., director of City of Hope’s Brain Tumor Program , is working on two other potential vaccines – one using nanoparticles and the other based on macrophages, another type of immune cell.
Brain tumors are hard to treat, Badie says, due to their location, the tumor’s aggressive nature, and the blood-brain barrier. Combined, these factors contribute to the overall poor survival rates.
As Badie noted, toxicity and access are two major obstacles to successfully treating brain tumors. Most chemotherapy drugs can’t get into the brain to reach the cancer cells, and those that can are untargeted, killing healthy brain cells along with cancer tumor cells. Cancer vaccines may overcome those problems, he says, by targeting treatment to the tumor alone without the use of toxic chemicals.
Vaccines are a relatively new development in the treatment of cancer. Only two types of vaccines have been approved to prevent cancer – human papillomavirus vaccines to prevent infection with the virus that causes many cervical cancers, anal cancers and head and neck cancers, and hepatitis B vaccines to prevent infection with the virus that can lead to liver cancer. Only one vaccine has been approved to treat prostate cancer.
But many researchers and physicians are pursuing the development of cancer vaccines, with clinical trials already under way for various cancers. However, Badie says, vaccines aren’t miracle cures. For example, only 30 percent of brain tumors have active levels of the EGFR target.
There won’t be one vaccine that can treat all brain tumors, he says, but there can be multiple versions. He envisions a future in which vaccines are an important part of brain tumor treatment, but it will take time to get there.
To find out more about the vaccine clinical trials – Badie is principal investigator for the EGFR vaccine and Jana Portnow, M.D., is principal investigator for the dendritic vaccine – go to City of Hope’s clinical trials website.