The Role of Circadian Rhythm Disruption in Cancer Progression: Molecular Mechanisms, Impact on Tumor Biology, and Therapeutic Insights

The circadian clock is an innate oscillator that synchronizes a number of biological processes into an approximately 24-hour cycle. Circadian rhythm disruption significantly affects the cancer progression by interfering with cellular processes such as angiogenesis, metabolism, immune surveillance, DNA repair, and cell cycle regulation. CLOCK, BMAL1, PER, and CRY are essential clock genes that are involved in interlocked transcription–translation feedback loops that sustain the circadian clock at the molecular level. When these processes are disrupted by environmental factors, lifestyle modifications, or genetic changes, they lead to immune evasion, unchecked cell growth, and metabolic and vascular remodeling that supports tumors. Furthermore, by altering the chromatin remodeling and gene expression, disturbance of the circadian rhythm might change the epigenetic landscape and further promote carcinogenesis. The molecular connections between cancer biology and circadian disruption are summarized in this review, which also focuses on new chronotherapeutic approaches that try to maximize effectiveness by coordinating cancer therapy with the body’s natural biological clock.