Using Vaccines to Treat Cancer
Unlike traditional vaccines intended to directly prevent diseases such as polio, small pox or measles, cancer vaccines do not directly attack the disease. Still, vaccines are critical to the prevention of many cancers and in the treatment of others.
A vaccine introduces a small amount of weakened or mutated disease cells into the body. Although it is not enough to make a patient sick, the vaccine has enough cells to help the body build antibodies to recognize and fight off the disease. Depending on the vaccine, the body may know how to prevent certain diseases for an entire lifetime, or the patient may need a booster, or “reminder,” to continue to ward off the disease.
Keywords:Cancer Vaccines, Vaccines for cancer, Vaccines
Cancer vaccines come in three categories:
Preventive Cancer Vaccines
Viral infections are responsible for the development of several cancers and preventive vaccines play an important role in reducing risk. For instance, cervical cancer and head and neck cancer can be caused by human papilloma virus, or HPV, whereas liver cancer can be caused by hepatitis B virus or HBV. Several vaccines have been developed that can prevent HBV and HPV infection and, as a result, protect against the formation of HBV- and HPV-related cancers. Four of these preventive cancer vaccines have been approved by the U.S. Food and Drug Administration (FDA).
Therapeutic Cancer Vaccines
Each individual’s tumor is in some sense unique and has its own distinguishing antigens. As a result, more sophisticated cancer vaccine approaches are necessary.
Fortunately, doctors can now identify targets on patients’ tumors that can help distinguish cancer cells from their normal cells. Sometimes these targets are normal proteins that are produced at abnormally high levels by cancer cells, such as prostatic acid phosphatase (PAP), which is often overexpressed by prostate cancer cells. Taking advantage of that insight, the sipuleucel-T vaccine was developed and received FDA approval in 2010 for the treatment of patients with advanced prostate cancer. Additionally, virus-derived proteins expressed by virus-infected cancer cells offer another promising source of markers that can be targeted through vaccines.
Another exception is Bacillus Calmette-Guérin, or BCG, a tuberculosis vaccine that acts as a general immune stimulant. In 1990, BCG became the first immunotherapy of any type to be approved by the FDA and is still used for the treatment of early-stage bladder cancer.
Personalized Neoantigen Vaccines
In contrast to normal-yet-overexpressed proteins like PAP, tumors also display unique targets that arise as a result of mutations. These are referred to as neoantigens (“new antigens”) and they are expressed exclusively by tumor cells and not by any of a patient’s healthy cells. With neoantigen vaccines, therefore, it is conceivable that immune responses could be directed precisely against patients’ tumor cells while sparing their healthy cells from immune attack, thus possibly preventing side effects.
In addition to the previously mentioned vaccines, several types of neoantigen vaccines are currently being evaluated, both alone and in combination with other treatments, in a variety of cancer types in clinical trials.