We’re all used to getting vaccines. Whether they’re against the flu, measles or tetanus, vaccines are the best way to prevent infection and have saved hundreds of millions of people from death and disability. The success of vaccines in revving up the immune system to rapidly attack infection has led many scientists and physicians to wonder if the same mechanism might be used to fight or even prevent certain types of cancer.
Vaccines work by alerting the immune system early to an invader it might not have seen yet. Most vaccines are injections that carry small, harmless amounts of pieces of a dangerous virus. The body recognizes those viral pieces, called proteins, as foreign and spends the time and energy to mount an attack to eliminate the invader. This recognition step is the hardest step. Once it’s done, each exposure to the same chunk of virus is faster and easier. The body does this on its own for the billions of viruses and bacteria we’re exposed to on a daily basis, but vaccines speed up the process for the deadliest invaders.
So if our immune system fights deadly viruses, why not deadly cancer? The problem is, cancers are a part of us. They grow from our own cells and the immune system has been trained not to respond to proteins that come from our own body. While this makes immune attack of cancers challenging, the body is still able to pick out and eliminate cancer cells. This is because cancer cells look different than normal cells. They make huge amounts of proteins helpful in boosting growth that normally are present only in small amounts in normal cells. The immune system can pick up on this increased amount of some proteins and respond as long as the cancer doesn’t find a way to evade those attacks.
One protein scientists had found to cause this kind of immune response to cancer is Mammaglobin-A (MAM-A). MAM-A is found only in breast tissue, and many breast cancers make abnormally large amounts of it. That makes MAM-A a good alert protein for a vaccine. A new study out this week used a creative experimental vaccination technique to trigger an immune response in a group of people with metastatic breast cancer.
The vaccine they used is called a DNA vaccine. It differs from protein-based vaccines in that it uses the body to make the protein, rather than relying on a company to make the protein for injection. Using the body to make the protein from foreign, injected DNA leads to a protein that seems more foreign to the body. Scientists have found that when a DNA vaccine is used to make the protein in the body, the immune system can pick up the target better and may attack it more vigorously.
The research team re-created the gene for MAM-A in the lab in large amounts and injected it into 14 patients whose breast cancer was found to have lots of MAM-A and that had spread from the breast to other parts of the body. Normally these patients have tried many treatments without success. The researchers found that the vaccine slowed the progress of their cancer and that the patients who got it lived longer without a relapse. They also confirmed that their immune system had responded to the injected DNA and that their immune cells were attacking tissues with MAM-A.
While the results are exciting, they should be taken with caution. The study included only 14 participants and was mostly testing for safety. These patients also often have problems with their immune system since they’ve had many rounds of damaging chemotherapy to treat their cancer. In spite of that, the results are promising. The authors of the study hope that moving the vaccine into more patients in earlier stages of cancer, before their immune system has been damaged by chemotherapy, will show it to be even more effective at prolonging the lives of those diagnosed.