One of the most promising areas for
the application of evolutionary principles in the fight against disease seems
to be cancer treatment. Cancer itself is a disease rooted in one of the most
fundamental principles of evolution; mutation. The NIH defines cancer as the
"uncontrolled growth of abnormal cells in the body." (Dugdale 2012)
These cells are abnormal because they reproduce at an increased rate or stop
the process of apoptosis (programmed cell death). These abnormalities are
genetic, caused by mutations in oncogenes. There are numerous genes which
regulate cell growth and death and thus even cancers originating from the same
organs can have very different genotypes and respond differently to treatment.
This is what makes cancer such a pernicious disease. Unlike atherosclerosis
(treated by regulating blood pressure and lowering LDL levels) or diabetes (treated
relatively effectively with well regulated insulin injections) there is no “one
size fits all” treatment for cancer. Therefore, it seems, an understanding of
everyone’s cancer cell genome will be exceedingly helpful in tailoring a
treatment specific to their disease. This type of individualized treatment has
become much more viable as the cost of genotyping cells has declined. Knowledge
of the cancer’s genome allows oncologists to employ more targeted treatments
rather than the broad brushed “forms of cytotoxic chemotherapy and radiation
therapy” (Hannun 1997) that are in most cases still the standard of care.
However, even with the knowledge of a cancer’s genome
oncologists are still battling the forces of natural selection. They may be
successful in eliminating the most aggressive or most prevalent strain of
cancer, but may leave behind mutant cancer strains which then go on to fill the
niche emptied by the cancer treatment. A new treatment is required because “tumors
that are intrinsically resistant to chemotherapy are unable to activate the
apoptotic machinery and may therefore be fundamentally resistant to
chemotherapeutic cell death” (Hannun 1997). Furthermore, the selectivity
of current chemotherapy treatments for cancer cells is limited and these
treatments are usually accompanied by debilitating side effects. Cancer cells
“may preferentially undergo cell cycle arrest or other nonapoptotic responses
to damaging insults” and therefore “selectivity over normal cells may not be
achievable”(Hannun 1997). Doctors have therefore begun to look
towards the immune system for effective treatment options. The merit of a
treatment utilizing our own immune machinery is that the immune cells could, in
theory, adapt to the mutations in cancer cells and therefore treat multiple
related cancer strains much more effectively than a targeted therapy.
Researchers have discovered a dendritic immune cell (DC)
which is believed to influence which foreign matter is attacked by the immune
system and which is left alone. While “B and T lymphocytes are the mediators of
immunity…their function is under the control of dendritic cells” (Banchereau
& Steinman 1998). The DCs “display many fine dendrites” (Banchereau &
Steinman 1998) which are used to capture potential antigens. DCs exist in
the “skin, airways and lymphoid organs” (Banchereau & Steinman 1998)
in their immature form. When exposed to pathogens however the DCs undergo a
transformation during which “antigen-capturing devices disappear, and T-cell
stimulatory functions increase” (Banchereau & Steinman 1998) thereby
allowing the DCs to communicate with T-cells and confer information about the
new pathogen. Researchers believe that they can use these cells to induce the
immune system to attack cancer cells as well as to treat other diseases such as
HIV or TB. (Engber 2012) Vaccines have been synthesized with cancer markers and
activators which attract DCs, but cancer response to these treatments has been
limited and, like other treatments, variable from patient to patient.
Researchers believe that large tumors that have become prolific enough to
affect a patient’s health have mutated in such a fashion so as to be ignored by
T-cells so immunotherapy treatments must be tailored to bypass these disguises.
Hopefully, through an increased understanding of evolution, biology and
chemistry a breakthrough in customized immune therapy is not that far off.
Works Cited
Banchereau, Jacques, and Ralph M. Steinman. "Dendritic Cells and the Control of
Immunity." Nature 392
(1998): 245-52. Print.
Dugdale, David C. "Cancer." Cancer. U.S.
National Library of Medicine, 3 Sept. 2012 .
Web. 16 Feb. 2013.
Engber, Daniel. "Is the Cure for Cancer Inside
You?" NY Times. N.p., 21 Dec. 2012 .
Web. 16
Feb. 2013 .
Hannun, Yusuf A. "Apoptosis and the Dilemma of Cancer Chemotherapy." Bloodjournal.hematologylibrary.org. The Journal of the American Society of
Hematology, 15 Mar. 1997 .Web. 16 Feb. 2013 .
word count: 656
Ben Kirby
Are the DCs related to neurons by any chance? Since axons and dendrites are parts of a neuron.
ReplyDeleteCool findings! It's great that finding the cure for cancer could also mean a cure for HIV, TB, and other diseases.
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ReplyDeleteI think it's really cool that cancer treatments are progressing towards more a "personalized" approach and catering to the individual. Perhaps further studies can be done to determine whether there are certain patient characteristics (eg: white cell counts, co-morbidities) that make them more or less responsive to treatment than others.
ReplyDeleteOncology is a very interesting field because of the many different types of cancers and the various behaviors of cancer cells. I could see treatment with dendritic cells becoming popular, especially if patients can avoid the adverse affects of chemotherapy and radiation therapy by fighting cancer with their own immunity.
ReplyDeleteI agree with Rande that it is indeed interesting that researchers are using immune cells to address cancer. However, while individualized approaches can be more beneficial on a individual level, I do question if customized therapy is the way to go. Do you think that this would result in the therapy being too impractical for widespread usage since the majority might not be able to afford it? (since specificity is usually correlated the cost)
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