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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Trends Ecol Evol. 2011 Apr;26(4):175–182. doi: 10.1016/j.tree.2011.01.002

Figure 1. Alternative pathways to cancer hallmarks.

Figure 1

(a) Assume that the ancestor of a large, long-lived organism has two pathways initiated by cytokines (triangles) such that if either one is disrupted the result is a hallmark of cancer. We illustrate this concept with cell proliferation; however this could be replaced with any of the hallmarks. A large organism could decrease its risk of cancer by evolving redundant copies of tumor suppressor genes (squares) (b) or by removing proto-oncogenes (circles) and tumor suppressor genes to eliminate an entire pathway (c) so that there are fewer carcinogenic loci in the genome that are vulnerable to mutation. This option might be constrained by selective pressures on the remaining pathways to produce the adaptive phenotypes that had been encoded in the deleted pathway.