These vaccines are made from actual cancer cells that have been removed from the patient during surgery. The cells are altered (and killed) in the lab to make them more likely to be attacked by the immune system and then injected back into the patient. The patient's immune system then attacks these cells and any similar cells still in the body. Most tumor cell vaccines are autologous, meaning the vaccine is made from killed tumor cells taken from the same person in whom they will later be used. Other vaccines are allogeneic, meaning the cells for the vaccine come from someone other than the patient being treated. Allogeneic vaccines are easier to make than autologous vaccines, but it's not yet clear if one type works better than the other.
These vaccines boost the immune system by using only one antigen (or a few), rather than whole tumor cells. The antigens are usually proteins or pieces of proteins called peptides. Antigen vaccines can be specific for a certain type of cancer, but they are not made for a specific patient like autologous tumor cell vaccines are.
Dendritic cell vaccines:
These vaccines have shown the most success so far in treating cancer. Sipuleucel-T (Provenge), which is approved for the treatment of advanced prostate cancer, is an example of a dendritic cell vaccine. Dendritic cells are special immune cells in the body that help the immune system recognize cancer cells. They break down cancer cells into smaller pieces (including antigens), and then hold out these antigens so other immune cells called T cells can see them. The T cells then start an immune reaction against any cells in the body that contain these antigens. Dendritic cell vaccines are made from the person in whom they will be used. The process used to create this type of vaccine (known as an autologous vaccine) is complex and expensive. Doctors remove some immune cells from the patient's blood and expose them in the lab to cancer cells or cancer antigens, as well as to other chemicals that turn the immune cells into dendritic cells and help them grow. The dendritic cells are then injected back into the patient, where they should cause an immune response to cancer cells in the body.
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. Vectors are special viruses, bacteria, yeast cells, or other structures that can be used to get antigens into the body. The vectors are often germs that have been altered to make sure they can no longer cause disease. Vectors can be helpful in making vaccines for a number of reasons. First, they can be used to deliver more than one cancer antigen at a time, which might make the body's immune system more likely to mount a response. Second, vectors such as viruses and bacteria might trigger their own immune responses from the body, which could help make the overall immune response even stronger. Finally, these vaccines might be easier and less expensive to make than some other vaccines.
Viruses are a type of germ that can infect and kill cells. Some viruses can be altered in the lab so that they infect and kill mainly cancer cells. These are known as oncolytic viruses. Along with killing the cells directly, the viruses can also alert the immune system to attack the cancer cells. An example is talimogene laherparepvec (Imlygic) which is an oncolytic virus that has been modified to make GM-CSF, a protein that boosts the immune response. This virus can be used to treat melanomas in the skin or lymph nodes that can't be removed with surgery. It is injected directly into the tumors, typically every 2 weeks. This treatment can sometimes shrink these tumors, but it has not been shown to shrink tumors in other parts of the body.