Abstract
Most human tumors harbor mutations that misregulate the early phases of the cell cycle. Here, we summarize genetic evidence, mostly obtained in our laboratory using strains of gene-targeted mice, that provides direct experimental support for a role of Cdk4 in tumor development. Moreover, these genetic studies challenge some well-established concepts regarding the role of Cdks during the early phases of the cell cycle. For instance, they have illustrated that Cdk4 and Cdk6 are not essential for cell division during embryonic development except in the hematopoietic system. More surprisingly, mice lacking Cdk2 survive for over 2 years without detectable abnormalities except in their germ cells, indicating that Cdk2 is essential for meiosis but dispensable for the normal mitotic cell cycle. Cdk2 is also dispensable for cell cycle inhibition and tumor suppression by the Cip/Kip inhibitors, p21(Cip1) and p27(Kip1). These observations have important implications not only to understand cell cycle regulation, but also to validate Cdks as potential targets for the development of therapeutic strategies to block proliferation of tumor cells.
MeSH terms
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Animals
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Cell Cycle / genetics*
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Cell Cycle / physiology*
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Cyclin-Dependent Kinase 2 / deficiency
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Cyclin-Dependent Kinase 2 / genetics
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Cyclin-Dependent Kinase 2 / physiology
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Cyclin-Dependent Kinase 4 / deficiency
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Cyclin-Dependent Kinase 4 / genetics
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Cyclin-Dependent Kinase 4 / physiology
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Cyclin-Dependent Kinase 6 / deficiency
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Cyclin-Dependent Kinase 6 / genetics
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Cyclin-Dependent Kinase 6 / physiology
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Cyclin-Dependent Kinase Inhibitor p21 / physiology
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Cyclin-Dependent Kinase Inhibitor p27 / physiology
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Cyclin-Dependent Kinases / deficiency
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Cyclin-Dependent Kinases / genetics*
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Cyclin-Dependent Kinases / physiology
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Female
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Fetal Death / genetics
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Genes, Lethal
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Humans
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Meiosis
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Melanoma, Experimental / enzymology
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Melanoma, Experimental / genetics
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Melanoma, Experimental / pathology
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Mice
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Mice, Knockout
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Mitosis
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Mutation*
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Neoplasms / enzymology*
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Neoplasms / genetics*
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Neoplasms / pathology
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Pregnancy
Substances
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Cdkn1a protein, mouse
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Cdkn1b protein, mouse
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclin-Dependent Kinase Inhibitor p27
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Cdk2 protein, mouse
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Cdk4 protein, mouse
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Cdk6 protein, mouse
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinase 4
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Cyclin-Dependent Kinase 6
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Cyclin-Dependent Kinases