Cancerous tumors might be our oldest evolutionary ancestors

Illustration for article titled Cancerous tumors might be our oldest evolutionary ancestors

Cancer is one of the most difficult foes medical science has ever faced, but a controversial new idea might just show a way to victory. A group of scientists have evidence that cancer might be an evolutionary throwback to our most distant animal ancestor.

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Astrobiologists Charles Lineweaver of the Australian National University and Paul Davies of Arizona State have proposed that cancerous cells are a so-called "living fossil", the last remnant of a crucial evolutionary juncture some 600 million years ago. It's been proposed before that cancer dates back to the beginning of multi-cellular animals, an evolutionary innovation that required cells to stop replicating whenever they wanted and start coordinating with the rest of the organism.

Cancer is what happens when these very ancient controls on cell replication break down, causing runaway cellular replication. But here's where Lineweaver and Davies take the idea a step further - they suggest cancer actually is our earliest animal ancestor. They suggest these organisms were the first to figure out some measure of control over cell replication, but they lacked more precise control over cell growth.

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This hypothesis, they argue, fits known tumor behavior better than the view that all cancer cells act independently. They point to angiogenesis, in which cancer cells built blood vessel networks to bring nutrients into the tumor, which suggests cooperation amongst the cells. Indeed, the very act of metastasizing, in which cancerous cells move to other tissue areas, is hard to explain if all the cells are acting independently.

Now, not all of Lineweaver and Davies's peers accept their new hypothesis. While their framework and predictions have received some praise, the idea that cancer is actually a living fossil for the earliest animal life has been met with controversy. It may be that their hypothesis ends up being more of a useful metaphor for understanding how cancer cells work together than as an actual literal explanation.

Still, assuming this idea is correct, how does it help any of us? Well, Lineweaver and Davies suggest that, if cancer really is our evolutionary ancestor, then its genetic toolkit has been locked in place for 600 million years, and its repertoire of survival methods is infinitely more limited than that of, say, bacteria, which has the capacity to evolve resistance to practically any therapy.

By comparison, cancer may have a relatively limited set of ways to resist therapies, and its methods shouldn't be anything that its evolutionary descendants - such as ourselves - are capable of. Lineweaver is hopeful genetic profiling will offer experimental support for his and Weaver's hypothesisObviously, even a limited survival toolkit has served cancer well in the decades medical science has spent trying to stop it, but in the long run, it should mean that cancer will run out of places to hide.

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Physical Biology via New Scientist. Image via.

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DISCUSSION

Dr Emilio Lizardo

I don't see how anybody takes this seriously. Cancer is a disease of the genome. Over thousands of replications in trillions of cells mistakes occur - mutations. The vast majority are either benign or not compatible with the cells survival and are harmless. Most of the remaining mutations are destroyed by the bodies immune and surveillance systems such as p53 which has been reported on here at io9. Sometimes a mutation occurs that gives the cell a growth advantage and avoids all the fail safes. That is only potentially a cancerous cell. Actually, it usually takes more mutations in order for the cell to survive, thrive and harm a person. usually it takes many more mutations. Not only are these mutations different for each disease but there are often many different mutations that lead to the same disease. While correct ideas have been laughed at before when first presented, this one does not seem to work for me. Each one of these mutations (literally thousands that we know of and maybe millions that we don't) are causing de-evolution to a more primitive state? How?

I will try to simplify this model, although I don't have access to the article. The authors are saying the following where "A" is a cancer cell and "C" is a normal cell.

A-B-C-A

Over generations the cancer cell has become normal and now in one lifetime has reverted. How did it take millions of years to evolve but only decodes to de-evolve? It seems more likely that it would be

A-B-C-D

Where D is the malignant cell. Only add in a few million letters to both sequences. This study seems like nothing more than a nice soundbite.

One other very important point. "Cancer" is not one disease so when somebody asks what causes cancer or when will there be a cure for cancer they are asking hundreds if not thousands of questions. Breast cancer is different than lung cancer is different than lymphoma. The starting point is a different cell and the mutations that occur are different. In fact, two cancers (of any type) that start from the same tissue and look exactly the same under the microscope may have entirely different genetic mutations, different behaviors and respond differently to therapies. That's why some people with metastatic breast cancer live a few months and others live more than a decade. So if anybody ever says he knows what causes all cancer or has a cure for cancer, be suspicious. There are known unknowns and unknown unknowns (apologies to Rumsfeld, and all who despise him) but personally I think that we only know a small fraction of the mutations that occur. Learning more helps us to treat people better and develop knew therapies. I have even been asked if I am worried cancer will be cured and I will be out of work. I worry about getting paid adequately for what I do but not being unemployed.