Can you imagine how long the average life
expectancy would be if cancer were ever eradicated the way polio and smallpox
have been? It's amazing to think about what doctors might be able to achieve in
our lifetime. Scientists have made significant inroads in the last few decades
and are now testing several vaccines that could possibly lead
to the complete prevention of cancer.
Probably the most promising form of cancer
treatment is in immunotherapy, where scientists are developing several
experimental cancer vaccines that could lead to the eradication of cancer this
century. There are two major categories that cancer vaccines fit into:
- · Specific cancer vaccine
- · Universal cancer vaccine
As the name suggests, specific cancer
vaccines are designed to treat specific types of cancers. In other
words, a vaccine could be developed for lung cancer, another vaccine could be
used to treat colon cancer, and yet another vaccine could treat skin cancer,
and so on. A more appealing cancer vaccine would be one that could fight cancer
cells regardless of cancer type. This type of vaccine is called a universal
cancer vaccine. In these two categories, there are more specific types of
cancer vaccines. Each type of cancer vaccine works on the same basic idea: The
vaccine, which contains tumor cells or antigens, stimulates the patient's
immune system, which produces special cells that kill cancer cells and prevent
relapses of the cancer. Unlike vaccines for other disease that prevent
the occurrence of the disease, there isn't a vaccine in development that can
prevent the onset of cancer. Cancer vaccines are used only as a treatment after
the cancer has been found in a patient. Here is a list of five kinds of cancer
vaccines being developed:
- · Antigen vaccines
- · Anti-idiotype vaccines
- · Dendritic cell vaccines
- · DNA vaccines
- · Tumor cell vaccines
Antigen vaccines use tumor-specific antigens -- proteins
displayed on a tumor cell -- to stimulate the immune system. By injecting these
antigens into the cancerous area of the patient, the immune system will produce
an increased amount of antibodies or cytotoxic T lymphocytes, also known as killer
T cells, to attack cancer cells that carry that specific antigen. Multiple
antigens can be used in this type of vaccine to vary the immune system
response.
In some instances, some antibodies, called
idiotype antibodies, act as antigens, triggering an immune response similar to
that described above. In this case, the immune system will produce anti-idiotype antibodies
to attack the idiotypes. Scientists have found a way to mass-produce
anti-idiotype antibodies to produce a vaccine that can be injected to treat
cancer.
Dendritic cells break the antigens on the
cancer cell surfaces into smaller pieces. The dendritic cells then act as
most-wanted posters for the immune system, displaying those antigen pieces to
the killer T cells. To make adendritic cell vaccine, scientists extract
some of the patient's dendritic cells and use immune cell stimulants to
reproduce large amounts of dendritic cells in the lab. These dendritic cells
are then exposed to antigens from the patient's cancer cells. This combination
of dendritic cells and antigens is then injected into the patient, and the
dendritic cells work to program the T cells.
With recent DNA (deoxyribonucleic acid)
research, scientists are finding ways to use the genetic code of proteins produced
in cells to aid the immune systems fight against cancer. Bits of DNA from the
patient's cells are injected into the patient, which instructs the other cells
to continuously produce certain antigens. This DNA vaccine
increases production of antigens, which forces the immune system to respond by
producing more T cells.
Tumor cell vaccines can be produced using cancer cells from
the patient or another patient. These cells are killed and injected into the
patient. While the cells are dead, the antigens are still recognized by the
immune system, which responds by attacking the dead cells. The immune system
will also attack the live cancer cells carrying the antigen that was displayed
on the dead cells.
While scientists have had
some success with each of these cancer vaccines, it is still much too early to
predict when a true cancer vaccine will be developed. However, science has
brought us closer than ever to being able to develop a method that could
eradicate some forms of cancer in our lifetime, if not all cancer entirely.
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