Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 215

When somatic cells replicate and divide, both point and chromosomal mutations accumulate with each additional generation of daughter cells because the replicative machinery commits errors and because of exposure to mutagenic agents. These mutations can have significant influences on cellular birth and death rates depending on the nature of the mutation. When comparing normal somatic cells with mutated somatic cells, it is important to realize that normal somatic cells grow, replicate, and die only when they receive specific signals. However, point or chromosomal mutations can allow somatic stem cells to create their own growth signals, to respond to signals destined to other cells, or to escape signals that cause normal cells to die by a process called apoptosis.

Mutations that increase the growth rate of somatic cells or that allow them to escape normal regulatory signals give them a selective advantage that allows them to outcompete their normal counterparts. As more genetic mutations occur, more functions in the cells can be affected. These malfunctions include disregulation of proto-oncogenes that stimulate cell growth, tumor-suppressor genes that suppress cell growth, and apoptosis genes that control cell death. The cumulative effect of these malfunctions leads to initial tumor formation.