The Circadian Clock as a Potential Biomarker and Therapeutic Target in Gastrointestinal Cancers

The circadian clock consists of a hierarchical multi-oscillator network of intracellular and intercellular mechanisms throughout the body that contributes to anticipating metabolic activity and maintaining system homeostasis in response to environmental cues and intrinsic stimuli. Over the past few years, genetic variations of core clock genes have been associated with cancer risk in several epidemiological studies. A growing number of epidemiological research studies have demonstrated a direct correlation between the disturbance of circadian rhythms and the growth of tumors, indicating that shift workers are more susceptible to malignancies of the colon, prostate, ovarian, breast, lung, and liver. One of the most related cancers with circadian rhythm is Gastrointestinal (GI) cancer, which is a leading cause of cancer-related mortality nowadays. The aim of this review was to demonstrate the effect of the clock gene network on the growth of GI cancer, providing molecular targets for GI cancer treatment, possible prognostic biomarkers, and guidance for treatment choices.