Theoretical evolutionary biologist Athena Aktipis, a co-founder of the Center for Evolution and Cancer at UCSF, talks to David Sloan Wilson about how cancer is evolution that’s taking place inside an organism, but a perversely adaptive form of it, since it ends in the death of both the organism and the cancer.
Aktipis explains the selection pressures on cancer cells:
Let’s say that a tumor has evolved and grown so much that the interior is totally absent of nutrients, like you see in some cities, where the slums are totally absent of resources and filled with garbage. There is intense selection for cells to survive better in those conditions, which we call hypoxic conditions. These cells become pre-adapted to live in regions that are far away from blood vessels, so when you give chemotherapy, they are able to hide out, a phenomenon called “refugia” in cancer treatment. There are some really important aspects of the environment, ecology, and diversity of ecological niches that get created in the course of cancer progression and changed during treatment that haven’t been fully considered from an evolutionary perspective. There’s a lot of opportunities.
A particular cancer therapy can make sense — that is, until it’s viewed from an evolutionary perspective. Aktipis gives the example of the medical bias toward going with the most aggressive treatment possible:
For a long time it was almost a moral imperative to use the highest dose and most aggressive treatment possible, but now that’s being reexamined and many top cancer treatment hospitals in the country and the world are backing off from that. Not all of them are backing off because of an explicitly evolutionary framework, but some of the work that has been done over the last decade has helped to show why an overly aggressive approach can be problematic. As for drug-resistant infectious agents and resistance to pesticides in agriculture, high doses in cancer treatment imposes the highest selective-pressure on a population of cancer cells. If you have a small population that’s not very diverse, then using a high dose can make sense. But if you have a large and diverse population of cancer cells then the higher the dose, then the greater the selection pressure for resistant cells. That’s one of the really important insights that comes from taking an evolutionary approach to treatment. We shouldn’t just think about killing cells; we should be more strategic about what we want to select for and against.
Dr. Aktipis is also the author of the forthcoming book from Princeton University Press, “Evolution in the flesh: Cancer and the transformation of life.”