Based at the Moffitt Cancer Center, Florida, Cancer Ecology is a small research group led by David Basanta. We are mathematical modellers who work with biologists and clinicians, trying to understand the ecology of tumors and the evolutionary dynamics of cancer progression and resistance to treatment.

Karl Sigmund's talk at ECCS

This week, Dresden is hosting the European Conference in Complex Systems (ECCS’07) which I am attending.

ECCS07.jpg

I was particularly interested in the keynote of Karl Sigmund at the University of Vienna, about the evolution of cooperation. As some of you know, the evolution of cooperation is something that is normally studied using game theory. GT can be used to explain the situations in which genetically related and (sometimes unrelated) individuals cooperate. Evolution of cooperation could potentially be used to explain how is it that tumour cells acquire all the capabilities required to progress to malignancy overcoming the anti cancer mechanisms of our bodies (already discussed here).

Since tumour cells are not necessarily so genetically related (at least compared to non tumour cells), the cooperation has meaning only when both cooperating cells receive a benefit. Without referring to cancer, Prof. Sigmund talked about the ways in which cooperation can emerge in populations in which individuals may chose to cooperate or not. Of those that chose to cooperate some of them might actually do so or alternatively can cheat, playing to be cooperators and receiving the benefits without actually contributing to the common good. In order to enforce cooperation, cooperating individuals might chose to punish defectors (thus making cheat more costly than cooperation) or non punishers. It is assumed that punishers do have to pay a bit (although not as much as the punished).This solution is not entirely satisfactory: in this way punishing enforces cooperation that benefits all cooperators, be it punishers or not, but with costs that are shouldered only by punishers. Thus punishing is a second level of cooperating that should need the same kind of reinforcement to work.

Prof. Sigmund showed some simulations (that can be found in this site) in which the
dynamics change depending on how many types of players we put in the game. In games with only cooperators, punishers (also cooperators) and cheaters, the cheaters tend to take over the population. Interestingly enough when non cheating non cooperators (they just never benefit from other people’s work but they do not contribute either) are allowed then it is punishers who thrive.

Interesting fact about this conference is that the keynotes and talks are being videorecorded and will be put online at Videolectures.net site.

Stem cells and breast cancer

Evolution in the individual