In an insightful plenary presentation this morning, Dr. Larry Norton offered an explanation of cancer evolution in the individual patient based on the principles of Darwinian evolution and “natural selection .”
Norton put forward the idea that the critical capability of cancer cells is not so much their ability to divide and grow but their ability to travel from their site of origin to new sites within the body (metastasis) and then survive in the next environment they reach. He argued that the defining characteristic of an aggressive form of cancer is the speed with which it can metastasize, as cells spread through the differing biological milieus. Although Dr. Norton is a breast cancer specialist by training, he exemplified his talk by demonstrating how this hypothesis explains many factors that are relevant to the develpment of prostate cancer, as well as breast cancer.
As a comparator, Dr. Norton reminded the audience of Darwin’s studies on the evolution and spread of differing species of bird in initially isolated communities. The species with the ability to fly from one island to the next were able to spread and populate across multiple islands in a chain, whereas the species that could not fly far enough to travel away from their island of origin were inevitably restricted to a population on that island, however successful they might be at breeding on that island. As a second analogy he asked the audience to think about the way that crabgrass and weeds like dandelions can spread through a field or a lawn. Each individual plant is small, and may not be that deeply rooted, but each plant seeds “offspring” aggressively, so that when each plant does spread the next generation of seeds, it can expand its environment a thousand-fold.
“Evolution,” Dr. Norton reminded the audience, “is all about relatively random changes. … a species that can survive changing environmental conditions, even internal climate change” will have an evolutionary and biological advantage over a species that does not have the capability to adapt to its environment.
Seen from this point of view, any form of cancer is simply a biological organism seeking to survive in a potentially hostile environment. The ability to metastasize and to evolve so that the individual calls can grow within and then “seed” the widest possible range of biological environments within the human body will optimize the survival of the cancer as a whole (at least until the host organism ceases to survive).
Dr. Norton’s presentation focused largely on the complex scientific detail underlying this hypothesis, but the base premise is captured in the above summary.
The “New” Prostate Cancer InfoLink believes that Dr. Norton’s analogic thinking does, in fact, offer us an interesting new way to look at the underlying biology of cancers in general and prostate cancer in particular. If we were able to arrest (or even to significantly delay) the process of prostate cancer metastasis by targeting the biological processes that drive cancer cells to metastasize out from the prostate, then there is little doubt we could profoundly impact disease progression even in those patients with the most aggressive forms of prostate cancer.