Cancer vaccines have been studied for several decades, but advances in this field have been slower than for other forms of immunotherapy. They are still mostly experimental treatments at this time.

Most of us know about vaccines given to healthy people for infectious diseases, such as measles and mumps. These vaccines use weakened or killed viruses, bacteria, or other germs to start an immune response in the body. Getting the immune system ready to defend against these germs helps it keep the germs from making people sick.

Some so-called "cancer vaccines" are designed to work the same way. For example, new vaccines against the human papilloma virus (HPV) help prevent women from getting cervical, vaginal, and vulvar cancer. Vaccines against hepatitis B virus (HBV) may lower some people's risk of getting liver cancer. But these vaccines don't target cancer cells; they target the viruses that can cause these cancers.

True cancer vaccines are different from the vaccines that work against viruses. Instead of preventing disease, they are meant to get the immune system to attack a disease that already exists.

A true cancer vaccine contains cancer cells, parts of cells, or pure antigens. The vaccine increases the immune response against cancer cells that are already present in the body. It may be combined with other substances or cells called adjuvants that help boost the immune response even further.

Cancer vaccines are thought of as active immunotherapies because they are meant to trigger your own immune system to respond. They are specific because they should only affect the cancer cells. These vaccines don't just boost the immune system in general; they cause the immune system to attack cells with one or more specific antigens. And because the immune system has special cells for memory, it's hoped that the drugs will help keep cancer from coming back.

Although cancer vaccines have shown some promise in clinical trials, none have yet been approved in the United States to treat cancer. Several types of cancer vaccines are now being studied. A few have reached late stage clinical trials.

Tumor cell vaccines

Tumor cell vaccines are made up of actual cancer cells that have been removed during surgery. The cells are treated in the lab, usually with radiation, so they cannot form more tumors. In most cases, doctors also change the cells in certain ways, often by adding chemicals or new genes, to make them more likely to be seen as foreign by the immune system. The cells are then injected into the patient. The immune system recognizes antigens on these cells, then seeks out and attacks any other cells with these antigens that are still in the body.

In some cases, doctors give the vaccine along with substances called adjuvants that increase the immune response. The general boost that adjuvants give to the immune system is meant to make the vaccine work better.

Some promising newer versions of these vaccines use tumor cells that are fused to dendritic cells, in the hope of further stimulating the immune system.

A possible advantage of tumor cell vaccines over antigen-based vaccines (described in the "Antigen vaccines" section) is that not all cancer antigens have been found yet. Using the whole tumor cell may expose the immune system to a large number of important cancer antigens, including some that researchers have not yet recognized. This may make them more effective. Also, dendritic cell–based vaccines may be better than antigen vaccines at recruiting other parts of the immune system to fight the cancer. They seem to be more likely to cause T cells to react against the cancer.

The 2 basic kinds of tumor cell vaccines are autologous and allogeneic.

Autologous vaccines

Autologous (pronounced aw-TAH-luh-gus) means "coming from the self." An autologous tumor cell vaccine is made from killed tumor cells taken from the same person in whom they will later be used. In other words, cells are taken from you (during surgery), the vaccine is made from them in a lab, and the cells are injected back into you. Autologous cancer cells may be reinjected shortly after surgery, or they may be grown in the lab or frozen and given later.

Although autologous tumor cell vaccines are promising, there are some potential drawbacks:

• It can be expensive to create a new, unique vaccine for each patient.

• Cancer cells tend to mutate (change) over time, so an autologous tumor vaccine might become less effective later if the cancer cells in your body change.

• Depending on the surgery and the size of your tumor(s), you may not have enough usable cells in the removed tumor to make a vaccine, or there may not be enough to re-treat if the cancer starts growing again.

Because of these problems, researchers are also looking at ways to create tumor cell vaccines that could work in any patient with that particular kind of cancer.

Allogeneic vaccines

Allogeneic (pronounced a-loh-jeh-NAY-ik) means "coming from another." These vaccines use cells of a particular cancer type that originally came from someone other than the patient being treated.

Allogeneic vaccines are easier to make than autologous vaccines.They are more like off-the-shelf drugs than a vaccine made for just one person. The cells for the vaccine are grown in the lab from a stock of cancer cells kept for that purpose. Some allogeneic tumor vaccines use a mixture of cells which were removed from several patients. The cells are treated and are usually injected along with one or more adjuvant substances to stimulate the immune system.

Types of cancers for which tumor cell vaccines are being studied

Although the FDA has not yet approved any tumor cell vaccines for general use, they are being studied in clinical trials against many types of cancer, including:

• melanoma
• kidney cancer
• ovarian cancer
• breast cancer
• colorectal cancer
• lung cancer
• prostate cancer
• non-Hodgkin lymphoma
• leukemia

Antigen vaccines

Antigen vaccines boost the immune system by using only one antigen (or a few), rather than whole tumor cells that contain many thousands of antigens. The antigens are usually proteins or pieces of proteins called peptides. Antigen vaccines may be specific for a certain type of cancer, but they are not made for a unique patient like autologous cell vaccines are.

Scientists have learned how to mass-produce many antigens in the lab. They can also change these antigens to make them more easily recognized by the immune system. This new technology means that large amounts of these very specific antigens can now be given to many patients.

Some antigens cause an immune response only in patients with a certain kind of cancer, while others produce immune reactions to more than one kind of cancer. Scientists often combine several antigens in a vaccine to try to get a stronger immune response.

Antigen vaccines are being studied to be used against these cancers, among others:

• breast cancer
• prostate cancer
• colorectal cancer
• ovarian cancer
• melanoma
• kidney cancer
• pancreatic cancer
• multiple myeloma

Dendritic cell vaccines

Dendritic cells are special antigen-presenting cells that help the immune system recognize cancer cells. They break down cancer cells into smaller pieces (including antigens), then hold out, or "present," these antigens to T cells. This makes it easier for the immune system cells to recognize and attack them. Dendritic cells are the most effective antigen-presenting cells known.

Dendritic cell vaccines are autologous vaccines, and must be made individually for each patient. The process used to create them is complex and expensive:

• Doctors remove some of the cells that grow into dendritic cells (from the blood) and treat them in the lab to make them multiply and turn into dendritic cells. This creates many more dendritic cells than if they just used cells taken from the patient. These dendritic cells are then exposed to cancer cells or cancer antigens.

• Other methods are to change their genes so that they make their own antigens or to fuse the dendritic cells with tumor cells. These procedures lead to dendritic cells with cancer antigens on their surface.

• The dendritic cells are then injected back into the body.

The dendritic cells that have cancer antigens on their surface are better able to help the immune system recognize and destroy cancer cells that have those antigens on them.

The dendritic cell vaccine approach has shown promise in tests in lab animals and in some human studies. They are only available through clinical trials at this time. They are being studied for use in people with these and other cancers:

• prostate cancer
• melanoma
• kidney cancer
• colorectal cancer
• lung cancer
• breast cancer
• leukemia
• non-Hodgkin lymphoma

Anti-idiotype vaccines

Every B cell or plasma cell makes only one kind of antibody. The unique part of each type of antibody is called an idiotype.

Antibodies are made when the immune system responds to antigens. But the immune system also makes some antibodies that treat other antibodies like antigens. In other words, sometimes the body makes antibodies against other antibodies. Scientists believe these antibodies against antibodies are important in helping to keep the immune system in check.

Antibodies and antigens fit together like a lock and key. So an antibody to a particular idiotype of another antibody (an anti-idiotype) will usually look like the antigen that triggered cells to make the antibody in the first place (like using the lock itself to make an extra key). Because the anti-idiotype antibodies look like the antigen and appear foreign, injecting them into the body causes the immune system to attack the anti-idiotypes, along with the antigens themselves.

Scientists have learned how to make these anti-idiotype antibodies in the lab. They can be used as part of a cancer vaccine because they look like the antigens on the cancer cells in the patient's body. Therefore, they can trigger an immune response against that specific cancer.

Researchers consider lymphomas to be the most promising targets for anti-idiotype vaccines. This is because all lymphoma cells have unique antigen receptors not present on normal lymphocytes or other normal cells of the body. These unique antigens can be used to make lymphoma vaccines. Early studies of B-cell lymphoma vaccines have been promising.

DNA vaccines

When tumor cells or antigens are injected into the body as a vaccine, they may cause the desired immune response at first, but they may become less effective over time. This is because the immune system recognizes them as foreign and quickly destroys them. Without any further stimulation, the immune system often returns to its normal (pre-vaccine) state of activity. To get around this, scientists have looked for a way to provide a steady supply of antigens to keep the immune response going.

DNA is the substance in cells that contains the genetic code for the proteins that cells make. Cells can be injected with bits of DNA that code for protein antigens. This DNA might be taken up by cells and instruct them to keep making more antigens. These types of therapies are called DNA vaccines.

Scientists may be able to do this by removing some of your cells, treating them with DNA that codes for a certain antigen, and then returning them to you. The altered cells would then make the antigen on an ongoing basis to keep the immune response strong.

DNA vaccines are now being studied in clinical trials for use against the following cancers, among others:

• melanoma
• leukemia
• prostate cancer
• head and neck cancer

Not all cancer treatments using DNA focus on the immune system. There are other types of experimental therapy that use DNA to treat cancer cells directly by replacing the damaged genes responsible for the cells' abnormal growth. Some add new genes that make the cancer cells more sensitive to anti-cancer drugs. For more information, please see our document, Gene Therapy.

Vector-based vaccines

These vaccines use special delivery systems (called vectors) to make them more effective. They aren't really a separate category of vaccine; for example, there are vector-based antigen vaccines and vector-based DNA vaccines.

Vectors are special viruses, bacteria, yeast cells, or other structures that can be used to get antigens or DNA into the body. The vectors are often germs that have been altered to make sure they can no longer cause disease.

Vectors may be helpful in making vaccines for a number of reasons. First, they may be used to deliver more than one cancer antigen at a time, which may make the body's immune system more likely to mount a response. Second, vectors such as viruses and bacteria may trigger their own immune responses from the body, which may help make the overall immune response even stronger. Finally, these vaccines may be easier and less expensive to make than some other vaccines. Many clinical trials of vector-based vaccines are now under way.

Go back to Immunotherapy.

Last Medical Review: 08/25/2009
Last Revised: 08/25/2009