June 25, 2008
Colon Cancer Vaccine on the Horizon
Researchers at Thomas Jefferson University in Philadelphia reported Tuesday that a protein found only in the intestines could hold the key to the development of a colon cancer vaccine. The researchers believe the protein might also pave the way to vaccines against other types of tumors.
In conducting their study, the scientists found that mice immunized with the protein and subsequently infected with colon tumors saw fewer tumors spread to the liver and lung than typically expected.
Although many cancer vaccines are in the works, scientists struggle to identify the proper antigens that are found only on the tumors and not in healthy tissue. The researchers, led by Adam Snook and Dr. Scott Waldman, decided to work with colon cancer in particular because the intestinal lining and other mucosal areas are protected from much of the immune system activity. Furthermore, some proteins from these immune-protected sites are also active in cancer cells.
The team looked specifically at guanylyl cyclase C (GCC) protein, which is normally expressed only in the lining of the intestines or in spreading colon cancer cells.
The researchers injected mice with colon cancer cells either before or after immunization with GCC. On average, the unvaccinated mice had 30 new tumors in the lungs and liver, whereas the vaccinated mice had only three, and also lived longer.
The researchers said that while the approach may not be a cure, it could certainly be used as an important treatment.
An estimated 1.2 million people worldwide are affected by colon cancer, and 130,000 are killed each year from the disease.
"More than 50 percent of patients with colorectal cancer die of metastatic disease, primarily in the liver and lung," they wrote in a report about the study.
The researchers warned that although injecting mice with tumor cells does indeed cause cancer, it does not perfectly replicate human cancer development. It is far more complex to treat a person with cancer than a mouse in a lab.
But the researchers remain optimistic their work will lead to a vaccine.
"We think this identifies a novel class of vaccine candidate targets for tumors that originate and metastasize from mucosa, like colorectal cancer," said Waldman in a statement reported by Reuters.
The researchers believe their approach may also work in cancers of the head and neck, breast, lung, vagina and bladder, all of which begin in the mucosa.
Other promising cancer vaccines under development include a melanoma vaccine made by Antigenics Inc. Another vaccine, made by Avant Immunotherapeutics Inc and licensed by drug giant Pfizer Inc, attacks the most common and lethal type of brain tumor known as a glioblastoma multiforme. And on Tuesday, Cuban scientists reported the availability of a vaccine that extends the lives of lung cancer patients.
The current research was reported in the Journal of the National Cancer Institute. An abstract can be viewed here.