This time I am sharing some thoughts on this interesting article with you:

Darwinian medicine: a case of cancer. Nature Reviews Cancer Vol 7, March 2007, pp 213-221.

The author, Mel Greaves (a researcher at The Institute of Cancer Research in the UK) is not a clinician and the journal, Nature Reviews Cancer, while prestigious, is not The Lancet so there’s a chance that Greaves might be preaching to the converts. That would be unfortunate as the message in the paper is one that should become familiar to practicing physicians, that susceptibility to malfunction and disease must in part reflect historical or evolutionary legacies. In my words, that cancer is a disease whose strength (and weakness) has evolutionary roots.

The implications of having an evolutionary perspective on medicine in general and cancer specifically are:

• That evolution rarely if ever achieves perfection (my own view is that evolution is more a satisfier than an optimiser as it is often claimed to be).
• That as we have been evolved to evolve efficiently (relatively of course), mutations must occur. A species with a perfectly functioning replication mechanism in which the offspring is always a perfect copy of the parent will be unable to evolve.
• That the mechanisms that allow for development can be co-opted by cancer (which Gatenby and Vicent proved mathematically in a Cancer Research paper a few years ago).
• That despite the existence of mechanisms that diminish the risk of cancer progression (like limiting the numbers of cells capable of unlimited replication and self-renewal, eg, stem cells), mistakes in the replication do happen.
• That we have been evolved for an environment that is not the one most readers of this blog inhabit. The Savannah has little in common with London or Tampa.
• That natural selection is inevitable given competition. Given diversity of phenotypes and limited resources, a test of fitness will determine which individuals will be strong enough to survive. And as this is true for us, it is also true for tumours made of different phenotypes.
• That cancers are moving targets. Most tumours never emerge through all the bottlenecks but those that doare likely to be more robust as well as genetically unstable. This would mean that some therapies may select against some phenotypes and potentially put the tumour in position to progress towards malignancy. It also means that tackling the microenvironment could be a potentially successful route to fight cancers.

Greaves, M. (2007). Darwinian medicine: a case for cancer Nature Reviews Cancer, 7 (3), 213-221 DOI: 10.1038/nrc2071