Physics (Internal)

Ecology and evolution of cancer tumors and expanding populations

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: Species expand their geographic ranges following an environmental change, long range dispersal, or a new adaptation. For species like the influenza virus, range expansions are the way of life. When species spread to new territories, they not only alter the affected ecosystems, but also change the course of their own evolution. I will show that range expansions enhance the role of demographic fluctuations and create nontrivial spatial patterns of genetic diversity, which can be easily visualized in growing microbial colonies. The buildup of spatio-genetic correlations profoundly alters evolutionary dynamics and could destroy genetic diversity even when it is favored by natural selection. I will also formulate a theory of evolutionary innovations that lead to population growth and apply it to cancer progression. Interestingly, tumor development is not a straightforward progression to malignancy because evolution is severely constrained by initial population size, mutation rate, and the effect of deleterious mutations. Below a critical population size, tumors are overwhelmed by deleterious mutations and tend to regress, while larger tumors accumulate beneficial mutations and grow. Progression to cancer is then akin to crossing an energy barrier in chemical kinetics. This theory explains some paradoxes in cancer research and is consistent with recent sequencing data. More important, the theory is also useful in designing treatment strategies based on the accumulated deleterious mutations, a potential Achilles' heel of cancer.