One of the potentially most interesting, yet untapped, area of study in population biology is that of intra-individual variation. One thing we do know, however, is that this variation can contribute to cancers. When cells accumulate mutations, some of these cell lines become cancer cells due to changes to genes involved in regulating the cell cycle. It would be especially interesting to apply the theory from population biology to this somatic variation within individuals.
If any of that stuff sounds interesting, you should check out this paper from Nature Reviews Cancer. The authors summarize applications of evolutionary biology and ecology toward understanding the growth of cancers. See here for a summary. Dan has a good wrap-up on Migrations here.
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Looks like it may be time for me to add an installation to my Medicine and Evolution series. ;-)
It seems to me that this opens up a much more interesting line of inquiry: Anti-cancer drugs from cancers themselves.
Think about it. If individual genetically-distinct cancer cells are competing for limited resources, one thing that may happen is that they will evolve strategies to reduce their opponents' reproductive chances. IANAEB (evol. biol.), nor do I work in any medical field, but I think this sounds like an interesting thing to look for.
Craig,
I'm not sure that's feasible - yes, tumors consist of phenotypically-diverse populations of cells, but any acquired traits that a cell might gain would be accessible to the majority of the other neoplastic cells in the tumor. Certainly some cannibalism amongst cancer cells may occur, but I think that most of the time it's in the form of endocytosis of apoptotic cells, and not predation or production of toxins.
As Hanahan and Weinberg describe in their 2000 Cell review, most cancers are instead characterized by the acquisition of a series of specific traits that allow the success of the dysfunctional cells individually, at the cost of the entire organism. As H&W describe them, they are evasion of apoptosis, self-sufficiency Re:growth signals, insensitivity to anti-growth signals, sustained angiogenesis, limitless reproductive potential, and invasion/metastasis. And this makes sense, I think, because the primary selective force against neoplastic cells is not competing cells, but the elimination and inhibition of such cells by the healthy cells of the body.
It's this predisposition of cells in the early stages of cancer to survive just about everything that we throw at them (even though only 0.1% of cells in a tumor may survive some treatments), that allow the cancer threat to survive dormant for years, only to come back stronger. Just like a highly adaptive microbe, it can evolve and come back regardless of how innovative the therapy - natural selection is smarter than humans.
At least that's my take on cancer progression as an evolving process...