Broken Body Clocks Drive Liver Cancer Growth and Cut Treatment Response

**Why This Matters** HCC kills more than 800,000 people annually and its incidence is projected to rise ~50% over the next two decades, driven largely by obesity and metabolic liver disease. Lifestyle-related circadian disruption—classified as a Group 2A carcinogen by IARC—may be a modifiable contributor to this trend, yet it is rarely addressed in clinical oncology practice.

**What Was Studied** This comprehensive narrative review, authored by a gastroenterologist and hepato-oncologist at the University of Lisbon, synthesizes the full breadth of circadian–HCC research: the molecular physiology of the circadian clock (CLOCK/BMAL1 transcription loops, PER/CRY repressor cycles, post-translational modifications); preclinical mouse models of chronic jet lag and mutant circadian genes; population epidemiology across time zones and sleep cohorts; tumor-level circadian gene expression studies; circadian-based prognostic signatures; and chronotherapy trials.

**Key Results** At the molecular level, circadian disruption activates the constitutive androstane receptor (CAR) via sympathetic dysregulation and bile acid accumulation, which in turn upregulates Wnt/β-catenin—one of the earliest oncogenic alterations in human HCC. BMAL1 knockdown enhances Hedgehog pathway signaling, present in most HCC tumors. The PI3K/AKT/mTOR axis, which drives the Warburg effect and epithelial–mesenchymal transition, is bidirectionally coupled to the clock. Loss of PER1 impairs ATM-mediated DNA repair and p53-dependent apoptosis, increasing genomic instability. Epidemiologically, a U-shaped association between sleep duration and HCC risk is consistently reported: sleeping ≤5 h raises risk ~25%, sleeping ≥9 h raises it 25–200% (up to 3-fold in obese individuals), and daytime napping >1 h raises risk ~50%. Approximately 15% of liver cancers may be preventable through healthy sleep habits. Tumor transcriptomic analyses show widespread downregulation of circadian genes (PER1–3, CRY2, TIM, NPAS2) driven primarily by epigenetic silencing (EZH2-mediated promoter methylation, histone deacetylase overexpression) rather than gene mutation. Circadian gene expression signatures accurately stratify HCC prognosis. Chronotherapy data suggest that administering immune checkpoint inhibitors in the morning—when immune effector cells are more active—may improve response rates.

**Implications** Circadian realignment strategies (light hygiene, consistent sleep scheduling, time-restricted eating) represent low-cost, scalable population-level interventions that could reduce HCC incidence. At the individual level, circadian molecular profiling may refine prognostication. Chronotherapy—timing drug delivery to circadian pharmacokinetic/pharmacodynamic peaks—offers a potential avenue to improve the efficacy of existing HCC treatments without additional toxicity.

**Caveats** Most mechanistic data derive from mouse models that may not fully recapitulate human HCC biology. Epidemiological studies are limited by self-reported sleep data, residual confounding, and possible reverse causality (liver disease itself disrupts sleep). Chronotherapy evidence in HCC specifically remains early-stage and requires prospective validation.