Chapter 15

Chapter 15 - Chapter 15 Regulation of Cell Number: Normal...

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Chapter 15 Regulation of Cell Number: Normal and Cancer Cells Regulated and unregulated cell proliferation •In higher eukaryotes, cell survival and proliferation are highly regulated by integrated controls that continually evaluate the state of the cell and its environment. •Normal cell proliferation is modulated by regulation of the cell cycle. •Apoptosis eliminates damaged cells and cells needed only temporarily during development. •The accumulation of mutations in cancer cells allows them to escape apoptosis and proliferation controls. Cell proliferation •Required for both development and homeostasis •Stem cells proliferate and differentiate in response to local signals to replace dead cells •Apoptosis eliminates cells as a consequence of internal and external signals •Cancers develop through accumulation of mutations in a clone of somatic cells •Hundreds of mutational events leading to neoplasia (cancer formation) have been identified Cell proliferation and elimination •Proliferation is controlled by cell cycle checkpoints •Protein kinases and protein phosphatases modulate activities of proteins regulating the cell cycle •In multicellular organisms, somatic cells may be eliminated by apoptosis •In apoptosis, a cascade of caspase enzyme activity destroys the cell •Proliferation and apoptosis pathways are linked at various points involving protein phosphorylation, allosteric interactions, and interaction between protein subunits
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Chapter 15 - Chapter 15 Regulation of Cell Number: Normal...

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