A relatively new approach for cancer treatment is biological
therapy. This cancer treatment is also known as biotherapy,
immunotherapy, or biological response modifier therapy.
Biological therapy began with the discovery
of immunization more than 200 years ago. Edward Jenner
discovered the benefits of injecting humans with fluid
taken from sores on cattle infected with
cowpox, a disease also
|
|
known as vaccinia.
This fluid contains the organisms that produce the disease.
His inoculation worked because the cells of the immune
system developed antibodies against the cowpox organism.
|
About a century later, William Coley, a New York surgeon,
started using biological therapy to treat cancer patients.
He noticed that people with some kinds of cancer appeared
to enter remission after developing certain bacterial infections.
He concluded that the body's response to the infection must
be exerting some effect on the cancer. He injected cancer
patients with live bacteria,
then later with filtered toxins. This induced an infectious
response that sometimes led to a remission of their cancer.
This method of treatment became known as Coley's toxins and
was used for decades.
Paul Ehrlich, a German Nobel Prize winner in 1908, theorized
that the surfaces of cells carried receptor molecules, or
side chains as he called them. He pointed out that antibodies
attached to these "side chains" triggered the release
of antitoxins. He also believed that antibodies might be developed
that could target invaders.
In the mid-1980s, encouraging results were seen in the use
of interferon to treat a rare blood disorder called hairy-cell
leukemia. The FDA has approved interferon for this disease,
as well as chronic myelogenous leukemia, AIDS-related Kaposi's
sarcoma, and genital warts.
|
More recently,
Steven Rosenberg, a researcher at the U.S. National Cancer
Institute, proved that the human immune system could be
directed to discriminate between healthy cells and cancerous
ones. Handled properly, immunotherapy could indeed stimulate
the body's defenses. In 1992 genetically engineered IL-2
received the FDA's approval for treating advanced kidney
cancer. In 1994 clinical trials were started to determine
whether another interleukin, interleukin ("IL-12"),
might have some benefit against metastatic cancer and
AIDS. |
To understand biological therapy, it helps to know some basics
about the immune
system, a complex network of organs and cells.
There are two basic types of defense protecting the body
from foreign invaders such as bacteria, viruses,
or cancer cells. The first line of defense is a physical barrier
involving the skin, mucous membranes, the lining of the respiratory
tract. This line of defense produces a nonspecific response
because it works regardless of the invader.
The second line of defense, unlike the physical barrier,
recognizes these invaders and then develops the specific weapons
to fight them. It is even able to remember what the invader
looked like so that the next time its response will be even
swifter. This line of defense that produces a specific response
is made by immune system cells. The immune system cells circulate
throughout the body and defend the body against attacks by
foreign invaders.
This immune network is one of the body's main defenses against
disease. It works against diseases, including cancer, in a
variety of ways. For example, the immune system may recognize
the difference between healthy cells and cancer cells in the
body and work to eliminate those that become cancerous.
Immune system cells include lymphocytes (white blood cells)
and other immune cells. Lymphocytes are the most important
cells of the immune system and can be categorized into T-cells,
B-cells, and
NK (Natural Killer)
cells.
T-cells directly attack infected, foreign,
or cancerous cells. T-cells also regulate the immune
response by signaling other immune system defenders.
B-cells secrete antibodies, the proteins that recognize
and attach to foreign substances known as antigens.
Natural Killer cells produce powerful chemical substances
that bind to and kill any foreign invader. They attack
without first having to recognize a specific antigen.
Monocytes are white blood cells that circulate in the
bloodstream. When they settle in tissue, the macrophages
engulf the invaders and actually digest them.
|
|
Understanding how immune system cells exchange messages and
finding ways to make these messages clearer and stronger are
the goals of research in immunology. Each of these components,
and each step in the immune response, represents a potential
avenue for the development of a cancer therapy.
Biological therapy research focuses on isolating specific
cells of the immune system and their chemical products, then
manipulating them in the laboratory to target their activity
and control their effects.
In summary, biological therapies use the body's immune system,
either directly or indirectly, to fight cancer or to reduce
the side effects that may be caused by some cancer treatments.
|