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The deregulation of several cell cycle-related genes participates in neoplastic transformation. Cell cycle progression is driven by cyclin-dependent kinases, which are positively regulated by association with cyclins and negatively regulated by binding to inhibitory subunits. The activity of cyclin-dependent kinases is also regulated by the phosphorylation status, which is controlled by the antagonistic action of weel kinase and CDC25 phosphatases. Three CDC25 genes are present in human cells: CDC25A, CDC25B, and CDC25C. These three genes function at different phases of the cell cycle. Whereas CDC25A and CDC25B are expressed throughout the cell cycle, with peak expression in G₁ for CDC25A and in both G₁-S-phase and G₂ for CDC25B, CDC25C is predominantly expressed in G₂. Several lines of evidence suggest a role for CDC25s as oncogenes. CDC25A and CDC25B cooperate with Ha-ras or loss …