THE MUTATION-RATE AND CANCER

The selection of advantageous mutations underlies tumorigenesis. The g rowth of a tumor is therefore a form of evolution at the somatic level , in which the population is comprised of individual cells within the tumor, Models of tumorigenesis have considered the relative importance of mutation and selection, We show that selection is more important t han an increased mutation rate in the growth of a tumor. Some cancers may acquire a ''mutator phenotype.'' probably leading to faster growth , but mutator phenotypes are not necessary for carcinogenesis.