A new method of brewing a cancer vaccine inside a patient’s tumor could harness the power of the immune system to destroy the disease, researchers report.
Immune stimulants are injected directly into a tumor, which teaches the immune system to recognize and destroy all similar cancer cells throughout the body, said senior researcher Dr. Joshua Brody. He is director of the Lymphoma Immunotherapy Program at the Icahn School of Medicine at Mount Sinai in New York City.
“We’re injecting two immune stimulants right into one single tumor,” Brody said. “We inject one tumor and we see all of the other tumors just melt away.”
Eight out of 11 lymphoma patients in a small, early clinical trial experienced partial or complete destruction of the tumor that received the initial injection, according to the report published April 8 in the journal Nature Medicine.
The vaccine also halted overall cancer progression in six patients for three to 18 months, and caused significant regression or actual remission in three patients, the investigators found.
The results were solid enough that the research team is expanding its next clinical trial to include lymphoma, breast, and head and neck cancer patients, Brody said. That trial started in March.
Prior efforts at unleashing the immune system to fight cancer have focused on T-cells, which Brody calls the “soldiers” of the immune army because they directly attack harmful invaders in the body.
Drugs called checkpoint inhibitors help T-cells identify cancer cells as the bad guys and kill them off.
“We call them the ‘Jimmy Carter’ medicines because that’s what Jimmy got when he had very advanced-stage melanoma,” Brody said.
But the checkpoint inhibitors have typically only been able to help about one in five cancer patients significantly, “so there’s lots of room for improvement,” he added.
This new vaccine approach focuses on dendritic cells, which Brody calls the “generals” of the immune system’s army. Dendritic cells guide the response of T-cells to fight off invaders.
“We’re trying to mobilize these immune generals to tell the soldiers what to do,” Brody said.
Patients first received nine daily injections of an immune stimulant intended to “recruit” dendritic cells by teaching them how to recognize cancerous cells, the study authors said.
The patients then received eight injections of a second stimulant that “activates” the dendritic cells, prompting them to instruct T-cells to hunt and destroy the now revealed cancer cells in the body.
Essentially, the method turns the injected tumor into a cancer vaccine factory, the researchers explained.
The approach differs from traditional vaccines for the flu or measles because those are preventive, teaching the body beforehand how to fight off an infectious disease, Brody pointed out.
This vaccine is therapeutic. “We’re trying to teach the immune system to get rid of the thing even after you’ve already got the problem,” he said.
Lab tests involving mice show that this vaccine approach could be at least three times more powerful if combined with checkpoint inhibitors, Brody added.
Because of this, patients in the new trial will receive both the vaccine and checkpoint inhibitors, the researchers said.
Susanna Greer, scientific director of clinical cancer research and immunology for the American Cancer Society, said that “priming” dendritic cells inside a person’s tumor to produce the best anti-tumor immune response “suggests a promising immunotherapy strategy.”
“Additional human studies are warranted to confirm these findings,” Greer said.
Dr. Catherine Diefenbach, director of clinical lymphoma at the NYU Langone Perlmutter Cancer Center in New York City, said the vaccine approach is “novel and extremely interesting,” and could help explain why checkpoint inhibitors usually don’t help patients with non-Hodgkin lymphoma.
However, she noted that really only three of the 11 patients in the initial clinical trial had truly meaningful responses to the vaccine.
“These are indolent lymphoma patients,” said Diefenbach, an expert for the American Society of Clinical Oncology. “The fact there was stable disease doesn’t really mean anything because these cancers don’t grow fast.”
What Is Cancer Immunotherapy?
Immunotherapy is treatment that uses certain parts of a person’s immune system to fight diseases such as cancer. This can be done in a couple of ways:
- Stimulating your own immune system to work harder or smarter to attack cancer cells
- Giving you immune system components, such as man-made immune system proteins
Some types of immunotherapy are also sometimes called biologic therapy or biotherapy.
In the last few decades immunotherapy has become an important part of treating some types of cancer. Newer types of immune treatments are now being studied, and they’ll impact how we treat cancer in the future.
Immunotherapy includes treatments that work in different ways. Some boost the body’s immune system in a very general way. Others help train the immune system to attack cancer cells specifically.
Immunotherapy works better for some types of cancer than for others. It’s used by itself for some of these cancers, but for others it seems to work better when used with other types of treatment.
What the immune system does
Your immune system is a collection of organs, special cells, and substances that help protect you from infections and some other diseases. Immune cells and the substances they make travel through your body to protect it from germs that cause infections. They also help protect you from cancer in some ways.
The immune system keeps track of all of the substances normally found in the body. Any new substance that the immune system doesn’t recognize raises an alarm, causing the immune system to attack it. For example, germs contain substances such as certain proteins that are not normally found in the human body. The immune system sees these as “foreign” and attacks them. The immune response can destroy anything containing the foreign substance, such as germs or cancer cells.
The immune system has a tougher time targeting cancer cells, though. This is because cancer starts when cells become altered and start to grow out of control. The immune system doesn’t always recognize cancer cells as foreign.
Clearly there are limits on the immune system’s ability to fight cancer on its own, because many people with healthy immune systems still develop cancer. Sometimes the immune system doesn’t see the cancer cells as foreign because the cells aren’t different enough from normal cells. Sometimes the immune system recognizes the cancer cells, but the response might not be strong enough to destroy the cancer. Cancer cells themselves can also give off substances that keep the immune system in check.
To overcome this, researchers have found ways to help the immune system recognize cancer cells and strengthen its response so that it will destroy them.
Types of cancer immunotherapy
The main types of immunotherapy now being used to treat cancer include:
Monoclonal antibodies: These are man-made versions of immune system proteins. Antibodies can be very useful in treating cancer because they can be designed to attack a very specific part of a cancer cell.
Immune checkpoint inhibitors: These drugs basically take the ‘brakes’ off the immune system, which helps it recognize and attack cancer cells.
Cancer vaccines: Vaccines are substances put into the body to start an immune response against certain diseases. We usually think of them as being given to healthy people to help prevent infections. But some vaccines can help prevent or treat cancer.
Other, non-specific immunotherapies: These treatments boost the immune system in a general way, but this can still help the immune system attack cancer cells.
Immunotherapy drugs are now used to treat many different types of cancer. For more information about immunotherapy as a treatment for a specific cancer, please see our information on that type of cancer.
Many newer types of immunotherapy are now being studied for use against cancer.