Meditations of an oncology geek

Can Aspirin Prevent Cancer?

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1 October 2011

Ed: I realize that this is a partial re-post, but in the time since I originally posted this article my readership has grown by a large amount. Moving from the experimental to theoretical, many postulate that this mechanism of cancer suppression might explain why athletes often develop the common cancers (minus skin cancer) less frequently. But I digress…

It’s easy to think of cancer as the enemy. Cancer is not the enemy. The body is the enemy: it’s an unwilling accomplice for the development of tumors. Though counterintuitive, it might actually be beneficial to treat cancer by slightly suppressing the immune system. This paradigm might actually define the future of cancer treatment and prevention.

(Emerging studies suggest that anti-inflammatory agents like aspirin might retard or prevent cancer in seniors, like a recent one in the peer-reviewed scientific journal Lancet, see below)

Tumors are not exclusively made up of cancer cells. In fact, some tumors contain only a very small percentage of cancer cells. When you take a trip inside the tissue architecture of tumors, you often find many fibroblasts, recruited blood vessels, and immune cells (like white blood cells). On the molecular level we see a trend as well. Due to the amount of infiltrating white blood cells, if you didn’t know better, you would think you were looking at a wound, or an infection.

The current trend in cancer research is to view cancer like a wound or infection that never heals. Your immune system consists of many specialized blood cells that can literally crawl right through your tissues, and through the margins between cells to inspect cells for damage or for invading bacteria. As part of a response to wound or trauma, immune cells rush to the scene and quickly colonize the tissue. This process is called inflammation, which I am sure you, dear reader, have become familiar with at some point in your life. To the immune system, a tumor cell likely looks like some sort of blunt trauma or physical wound, but as part of our evolutionary upbringing of a species over the eons, it was important to mount a VERY robust anti-bacterial and anti-viral response to any wound. Today we have the help of antibiotics… but that is a discussion for another time.

Once immune cells clear the area of “foreign” cells like bacteria or cells damaged with viruses, they secrete mitogenic factors that stimulate cell growth! AND, they secrete factors that guard against apoptosis, the cell’s natural self-destruct mechanism. Resisting apoptosis is a hallmark of cancer.

The problem is that to the immune system, a cancer cell looks almost identical to a normal cell. The two cells differ in ways so subtle that even our awesome immune systems cannot tell the difference. Not being foreign, the default action is “repair” instead of “destroy.”

In a nutshell, the body often treats tumors like wounds, and actually nourishes it and provides it with the building blocks to grow! As proof of this concept, it is now widely accepted in the cancer biology field through numerous studies in cells, animals, and humans that mild immuno-suppression actually reduces cancer risk. An example of this theory being applied successfully is the re-purposing of the drug Rapamycin. Rapamycin has been used for forty years as an immunosuppressant with people who receive organ transplants. Recently, it has been tested and found (in much smaller doses) to have very potent anti-cancer effects as well (1).

(A little nerd trivia for you: What do giant stone heads and rapamycin have in common? They can both be found on Easter Island. Rapamycin was originally isolated from soil bacteria native to the island)

Beyond Rapamycin, there have been large-scale studies on habitual users of Aspirin as a guard against stroke and heart attack. In these long-term studies scientists have also realized that seniors who consume aspirin regularly also have a reduced risk of developing cancer (2). This type of study is long-term, double blind, with a decent control group, and is considered fairly sound.

There are many more studies currently underway investigating the use of anti-inflammants as cancer suppressors. Drugs like aspirin and rapamycin are already cheap to produce, and have been around long enough that their long-term toxicities are well documented. I personally follow these with great interest, as they have the potential for immediate positive impact in the area of cancer prevention. I will explore this topic to a greater extent in a future article.

That being said, DO NOT begin ANY drug regimen without consulting your physician. If you are young and concerned about hereditary cancer affecting you before you get old, please first read up on the genetics of cancer, and if you are still concerned, please contact a genetic counselor.

Summary: The body sees tumors as wounds that never heal, and can actually help tumors grow because the immune system aids it like it would a regenerating tissue. Reducing chronic inflammation can retard or prevent cancer development, with a proof of concept demonstrated by large-scale studies of anti-inflammants in humans.

-Ryon

Back to Cancer for Dummies main page for more topics.

References:
1) Zoncu, R, Efeyan, A, Sabatini, DM. mTOR: from growth signal integration to cancer, diabetes and ageing. Nat Rev Mol Cell Biol 2011;12(1):21-35.
http://www.ncbi.nlm.nih.gov/pubmed/21157483
2) Rothwell, PM, Fowkes, FG, Belch, JF, Ogawa, H, Warlow, CP, Meade, TW. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Lancet 2011;377(9759):31-41.
http://www.ncbi.nlm.nih.gov/pubmed/21144578

Written by Ryon

October 1st, 2011 at 11:12 am

Posted in Science Blog

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