Regeneration, Stem Cells, and the Evolution ofTumor Suppression

摘要

All multicellular organisms have requirements for tumor suppression to regulate cellular proliferation during either embryonicdevelopment or adult life. However, different organisms have vastly different requirements. Adult tumor suppression is proba-bly not crucial to organisms possessing both short life spans and largely postmitotic soma. In contrast, animals with lifelongtissue turnover or those capable of regenerating body parts lost to injury must possess evolutionarily selected mechanisms tocontrol rates of cell proliferation such that tissue homeostasis can be maintained or restored after injury. We hypothesize thatthese biological differences may help to explain why the lists of tumor suppressor genes in humans and Drosophila are largelynonoverlapping. Here, we address this disparity by examining the tumor suppressor gene content of two outgroups to the ver-tebrates and flies/nematodes: the freshwater planarian and the single-celled choanoflagellate. Both of these organisms haverecently had their genomes sequenced, giving us a first glimpse of which known tumor suppressor genes have been maintainedduring evolution. In addition, we attempt to resolve which genes may have had ancestral tumor suppressor function and whichmay have acquired this function de novo.