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. Author manuscript; available in PMC: 2021 Dec 1.
Published in final edited form as: Semin Cancer Biol. 2020 Jan 30;67(Pt 2):159–170. doi: 10.1016/j.semcancer.2020.01.012

Figure 1. Schematic illustration of cell cycle regulation.

Figure 1

Cell cycle is divided into four phases: G1 (gap phase 1), S (DNA synthesis), G2 (gap phase 2), and M (mitosis). Cell cycle progression is regulated by cyclins and their cognate CDKs. As the important regulator of G1 phase, CDK4/6 inhibitors have been developed, for example, PD-0332991 (palbociclib), LY2835219 (abemaciclib), and LEE011 (ribociclib) that are approved by U.S. Food and Drug Administration to treat human tumors.