The passage of a cell through the cell cycle is regulated by various proteins. Cyclin dependent kinases (CDKs) phosphorylate several substrates such as transcription factors and cytoskeletal proteins, which leads to the transition of the cell into the next cell cycle phase. CDKs are activated by cyclins, which are expressed in distinct phases during the cell cycle. Importantly, CDKs are inhibited by specific cyclin dependent kinase inhibitors. In many types of cancer, proteins that regulate the cell cycle are deregulated by genetic or epigenetic changes in the corresponding genes. For example, CDK4 is mutated in melanoma and is amplified or overexpressed in several other malignancies, including sarcoma, glioma, breast tumors, lymphoma and melanoma.

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The cell cycle – Part 1: Phases and checkpoints