Cancer vaccines
In another field, scientists are researching ways of teaching the body's immune system to attack and destroy cancer cells. Leaders in the field include the Dana-Farber/Harvard Cancer Center, home of the Monoclonal Antibody Core, dedicated to the study of this technology. The immune system works like this: Foreign substances, called antigens, stimulate a “fight” response by the body's immune system. The body produces proteins, called antibodies, each of which locks on to its specific antigen, identifying it to the immune system as something that needs to be destroyed. In order to use this immune response against cancer cells, scientists have designed antibodies called monoclonal antibodies. Each can identify a single antigen in cancer cells, attach itself to that antigen and trigger that cell's destruction.
The best known monoclonal antibody is Herceptin, approved since 1999 for use in women with a certain kind of breast cancer. Avastin, another monoclonal antibody, treats advanced colon cancer. As of August 2006, American companies had 160 different monoclonal antibodies, with a variety of applications, in clinical trials or awaiting government approval.
In another strategy, adoptive immunotherapy, T cells, a type of white blood cell that is central to a healthy immune system, are taken from the patient and genetically programmed in such a way that, when returned to the patient, they will recognize, target and kill cancer cells.
A cancer treatment breakthrough
Just last year, both Canadian doctors in Toronto and Italian researchers in Rome announced a breakthrough discovery: not all cells in a tumour make the tumour grow and spread. Those that do, which the scientists are calling “cancer stem cells,” have a unique chemical profile. If doctors can engineer antibodies to attack these particular cells they might be able to kill cancer for good, with no chance of recurrence.
In addition, doctors hope to tap into how our bodies naturally destroy diseased or damaged cells. Researchers have discovered that cancer cells may block the mechanisms that regulate this apoptosis, or programmed cell death, so that cancer cells are not getting the signal to die, but instead continue to grow and multiply. The proteins that cause programmed cell death have already been discovered. Now EpiCept Corporation in California is working with drugs that would mimic these proteins, to see if they would increase tumour cell death. This novel approach to targeted cancer treatment is in the early stages.
Cancer vaccines
When we think of vaccines, we think of preventing illnesses caused by viruses, such as polio or measles. The new cervical cancer vaccine works by preventing infection by the sexually transmitted human papillomavirus, which can cause cancer. But other cancer vaccines are a bit different.
How do they work? Cancer cells have mechanisms to make themselves invisible to the body's immune system. Cancer vaccines are used to help the immune system recognize the tumour cells and then fight back against them. They are not preventive; they are administered after the cancer develops.
Therapeutic vaccines have some advantages over standard cancer therapies: they are well tolerated and have few side-effects, thanks to the immune system's ability to attack only foreign cells. Scientists hope that they will produce longer remissions by triggering the immune system to remain on guard for longer periods of time. They might even prevent the cancer from ever coming back.
Vaccines against breast, lung and ovarian cancers, as well as melanoma, are still in the experimental stage, and much work remains to be done. As with many cancer treatments, they will likely be used in conjunction with other therapies rather than as a stand-alone treatment. Huge strides are being made in progressive and humane ways to tackle cancer. We are on the verge of a radically new future, made possible by the dedication of many researchers, who hope that one day a cancer diagnosis will provoke no more fear than that of any other disease or sickness.
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 | This article was first published in the February/March 2007 issue of Homemakers Magazine. Click to subscribe online and never miss an issue. |
