Cancer Ecology and Evolution: Positive interactions and system vulnerability

Abstract

Parallels of cancer with ecology and evolution have provided new insights into the initiation and spread of cancer, and new approaches to therapy. This review describes those parallels while emphasizing some key contrasts. We argue that cancers are less like invasive species than like native species or even crops that have escaped control, and that ecological control and homeo-static control differ fundamentally through both their ends and their means. From our focus on the role of positive interactions in control processes, we introduce a novel mathematical modeling framework that tracks how individual cell lineages arise, and how the many layers of control break down in the emergence of cancer. The next generation of therapies must continue to look beyond cancers as being created by individual renegade cells and address not only the network of interactions those cells inhabit, but the evolutionary logic that created those interactions and their intrinsic vulnerability.

Keywords: cancer; ecology; evolution; invasive species; mathematical model.

Figure 1:

Strategic diagram of cancer interactions. Arrows indicate activation and flat-headed segments inhibition.

Figure 2:

Model populations of all cell lineages showing high degrees of cell turnover but constant overall population with strong control (A) and steadily increasing population with weak control (B). The dark green line shows the population of unaltered cells, the bright green lines cells altered in aspects that do not directly affect fitness, and darker gray lines cells with traits increasingly different from the original type.

Figure 3:

Populations of all model elements in the conditions of strong control (A) and weak control (B) as in Figure 2. Model elements as in Figure 1 with N representing normal or unaltered cells.