Somatic evolution of Cancer: A new synthesis

Abstract

Cancers have been interpreted either as somatic evolution of cheater cells that escape replication regulation or alternatively as non-healing wounds. Both the interpretations have substantial support as well as glaring anomalies but the two have not been put together to make a coherent synthesis. We argue here that mechanisms and pathways to escape the normal regulation of cell proliferation do not need to evolve de novo. Mechanisms to override the normal regulation have already evolved for wound healing and tissue regeneration. Almost all of the hallmarks of cancer are also seen in the wound healing process. This suggests that cancer develops not by any de novo gain of function but by exaptation of pre-evolved wound healing functions. Somatic evolution that makes the wound healing triggers constitutive is not mutation limited but selection limited and the selective forces are dependent on the tissue microenvironment. Some mechanisms for such selection have been suggested. Many more need to be investigated. A series of mechanisms have evolved to minimize the risk of cancers which may fail in an altered lifestyle context. We support our synthesis with multiple lines of evidence and also make differential testable predictions. This evolutionary perspective challenges multiple prevalent ideas, suggests novel lines of research and also has translatable implications for cancer prevention.