The Cell Cycle in Cancer: Molecular Pathways, Checkpoint Aberrations, and Therapeutic Opportunities

The eukaryotic cell cycle is a finely orchestrated sequence of events ensuring accurate DNA replication and equal segregation of chromosomes. Dysregulation of this system lies at the heart of malignant transformation and cancer progression. Here, we provide an in-depth synthesis of the genetic, epigenetic, and biochemical alterations that affect cell cycle regulation in cancer, emphasising oncogene activation, tumour suppressor inactivation, and disruption of checkpoint fidelity. We explore the molecular mechanisms by which these perturbations foster replication stress, genomic instability, and aneuploidy. Furthermore, we review emerging therapeutic strategies that target these vulnerabilities, including inhibitors of cell cycle kinases, replication stress response mediators, and chromosomal segregation checkpoints. By integrating foundational discoveries with contemporary insights, this review elucidates the central role of cell cycle dynamics in oncogenesis and its therapeutic exploitation.