Current options to treat cancer include surgery, chemotherapy, and radiotherapy; but will there ever be a cancer vaccine?
Vaccines are a powerful method to prevent infectious diseases. They work by stimulating the immune system to mount a reaction against dangerous germs. The success of vaccines in controlling infectious diseases prompted scientists to explore their use against cancer. Researchers hoped to create vaccines capable of directing the protective activity of the immune system against cancer cells. For vaccination to be effective, a functioning immune system is necessary. Unfortunately, this is often not the case for cancer patients. The advanced age of patients, the burden of cancer and its treatment often compromise immune defenses. As a result, cancer vaccines did not live up to expectations despite the century-long efforts. On a brighter note, recent developments in medical research uncovered some of the mechanisms affecting immune defenses of cancer patients.
Recent studies sparked new interest in developing a cancer vaccine
Researchers at Mount Sinai developed a new vaccine and tested its efficacy in patients with lymphoma, a type of cancer that affects white blood cells. Their results are published in Nature Medicine. This approach consists of injecting the vaccine into the specific areas affected by the cancer. The goal is to trigger a strong immune response against cancer cells within the affected body areas. This strategy differs from traditional vaccination, which prevents future infections.
How does the cancer vaccine work?
First, a small molecule called Flt3L is injected into the tumor mass. This molecule recruits immune cells called dendritic cells to the affected areas. Second, the administration of local radiotherapy will kill cancer cells. Dendritic cells on-site capture the dead cancer cells and process them. This activity allows dendritic cells to learn how to distinguish cancer cells from the body’s own cells and to instruct other immune cells to selectively kill tumor cells. Poly-ICLC is the third component of the vaccine, a substance that works by stimulating the activity of dendritic cells.
Preliminary studies in mice and a clinical trial in humans put the new vaccine to the test
Vaccination of mice with lymphoma in laboratory experiments led to tumor regression and improved survival. Despite the positive and promising results, tumor growth recurred a few weeks after treatment due to the adaptive capabilities of cancer. Scientists then tested a new therapy by combining the vaccine with ‘checkpoint blockade therapy’, which is a technique already in use to treat lymphoma. These experiments showed that combining the vaccine with this type of immunotherapy drastically improved outcomes in mice.
A clinical trial evaluated the effectiveness of the vaccine in 11 patients with advanced-stage lymphoma. Following treatment, most of the patients showed tumor shrinkage, and some of them achieved remission lasting from months to years.
Further clinical trials
A new clinical trial is currently underway. The new study will evaluate the vaccine in combination with immunotherapy to treat lymphoma, breast, and head and neck cancer.
Written by Raffaele Camasta, PhD
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- Butterfield, L. H. (2015). Cancer vaccines. BMJ (Clinical Research Ed.), 350, 1-14.
- Mount Sinai researchers develop treatment that turns tumors into cancer vaccine factories. https://www.eurekalert.org/pub_releases/2019-04/tmsh-msr040219.php
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