What Is a Cancer Vaccine?
Vaccines are medications given to help the body fight or prevent disease. The immune system benefits from vaccines by being able to recognize and destroy harmful substances. Traditional vaccines, which prevent viruses like chickenpox or the flu, are made from small amounts of weak or dead viruses. By exposing your body to the vaccine, it will be able to adapt to that particular disease and fight it more effectively. This concept is called immunization, meaning the patient becomes immune, or, is not susceptible to a specific disease.
Cancer vaccines are designed to kill cancer cells. There are two types of cancer vaccines: preventative and treatment. Preventative or “prevention” vaccines, similar to traditional vaccines, protect the body from disease-causing viruses. Typically, healthy patients receive this type to keep cancers from developing. A person has to get a prevention vaccine before the virus infects them in order for the vaccine to work.
The U.S. Food and Drug Administration (FDA) currently approves two types of cancer prevention vaccines: the HPV vaccine and Hepatitis B vaccine. Both infections can cause different types of cancer that typically affect the reproductive organs or the liver.
Cancer treatment vaccines, or therapeutic vaccines, are a form of immunotherapy that boosts the body’s natural defense – the immune system. Doctors administer treatment vaccines to cancer patients in an attempt to destroy cancer cells still in the body once treatment has ended. Also, treatment vaccines aid in preventing the cancer from returning.
In 2010, the FDA approved Sipuleucel-T to treat advanced prostate cancer. The FDA has also approved Talimogene Laherparepvec (T-VEC) to treat advanced melanoma. There are currently no therapeutic cancer vaccines approved to treat mesothelioma, but current clinical trials are testing several options.
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How Do Cancer Vaccines Work?
Cancer vaccines target the body’s cancer-specific antigens (molecules on the surface of diseased cells, bacteria, or viruses not normally supposed to be there). The immune system gets rid of the antigens by attacking and killing them. When this happens, the immune system remembers how to respond to those antigens in the future.
Cancers like mesothelioma can weaken the immune system, and treatments like chemotherapy can actually destroy healthy blood cells. The purpose of a vaccine is to boost the immune system’s ability to recognize and destroy uninvited antigens.
Additional molecules administered through the vaccine act as antigens, which stimulate the immune system to recognize and destroy cancer cells with the same molecules on their surface. Cancer vaccines also contain adjuvants, the agents that help strengthen the immune system’s response.
Cancer vaccines made for individual patients are produced from a sample of that person’s tumor. With this approach, the patient undergoes surgery to remove a tumor. Generally, researchers use the cells from the tumor or immune cells from the patient’s blood to treat them with the vaccine. Then, the immune cells are given back to the patient, with hopes that the body’s immune system will attack the disease.
Sipuleucel-T (Provenge®), for men with metastatic prostate cancer, is customized for each person and works by removing white blood cells from the patient. Then, the cells are modified by doctors to recognize and kill prostate cancer cells. Once this step is completed in a laboratory, the modified white blood cells are put back into the patient through intravenous (IV) infusion.
Limitations of Cancer Vaccine Research
Developing cancer vaccines can be challenging for researchers because of their limited knowledge. Researchers believe treatment vaccines may work better in early-stage cancers or for smaller tumors because of these complications.
Since cancer cells suppress the immune system, they are able to spread and grow rapidly. Because of this, vaccine researchers use adjuvants, agents that boost the immune system’s response, to fight them.
Another limitation of early vaccine research is the ability of the vaccine to destroy large tumors. Larger or more advanced tumors are hard to eliminate using only the vaccine. As such, patients usually receive one after standard treatment, like chemotherapy or surgery.
Because of the long latency period, the period of time between exposure to asbestos and the development of symptoms, mesothelioma typically affects people over the age of 65. Older individuals tend to have weaker immune systems, making it harder for their bodies to have a strong immune response after vaccination.
Mesothelioma Vaccines in Clinical Trials
Most cancer vaccines are not approved by the FDA and are only available through clinical trials. The trials study and learn important information about improving cancer vaccines. Clinical trials are currently testing vaccines for several forms of cancer, including bladder, brain, kidney, prostate, and more.
Preventative Vaccines for Mesothelioma
Researchers at the John A. Burns School of Medicine at the University of Hawaii Cancer Center are working on a preventative vaccine for mesothelioma, called HIvax. The vaccine targets a protein, survivin, found in mesothelial cells. After finding improved survival time in mice, researchers are working towards preparation for human clinical trials.
A Phase II clinical trial of the WT1 vaccine, also known as galinpepimut-S, met the one-year progression free survival (PFS) in pleural mesothelioma patients. Participants experienced an overall increase in survival rate compared to subjects who did not receive the vaccine. In 2016, the FDA approved WT1 as an orphan drug, a drug that may show enough promise for commercial use in the future. Researchers are planning a larger, randomized phase III trial once funding becomes available.
Stem Cell Vaccines
The Stanford University School of Medicine is working on a stem cell vaccine for the treatment of malignant mesothelioma. Since cancer cell repopulation during standard treatment limits efficacy, researchers believe injecting the stem cell vaccine, involving induced pluripotent stem (IPS) cells or a patient’s own modified cells, will stimulate an immune response. Researchers have only tested the vaccine on animals and are awaiting approval for human subjects.
Learn More About Mesothelioma Treatment
Treatment for mesothelioma typically involves surgery, chemotherapy, radiation, or a combination of these treatments. Curative treatment for mesothelioma, however, has been limited or unsuccessful. Researchers hope cancer vaccines will eventually be an effective tool in treating mesothelioma. To learn more about treatment options, download our free mesothelioma guide.
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