Published online Feb 28, 2014. doi: 10.3748/wjg.v20.i8.1986
Revised: January 6, 2014
Accepted: January 20, 2014
Published online: February 28, 2014
Clock genes create a complicated molecular time-keeping system consisting of multiple positive and negative feedback loops at transcriptional and translational levels. This circadian system coordinates and regulates multiple cellular procedures implicated in cancer development such as metabolism, cell cycle and DNA damage response. Recent data support that molecules such as CLOCK1, BMAL1 and PER and CRY proteins have various effects on c-Myc/p21 and Wnt/β-catenin pathways and influence multiple steps of DNA damage response playing a critical role in the preservation of genomic integrity in normal and cancer cells. Notably, all these events have already been related to the development and progression of colorectal cancer (CRC). Recent data highlight critical correlations between clock genes’ expression and pathogenesis, progression, aggressiveness and prognosis of CRC. Increased expression of positive regulators of this circadian system such as BMAL1 has been related to decrease overall survival while decreased expression of negative regulators such as PER2 and PER3 is connected with poorer differentiation, increased aggressiveness and worse prognosis. The implications of these molecules in DNA repair systems explain their involvement in the development of CRC but at the same time provide us with novel targets for modern therapeutic approaches for patients with advanced CRC.
Core tip: Clock genes are involved in numerous cellular activities such as cell cycle and DNA repair with various implications in the development of colorectal cancer. Multiple clinical and epidemiological data support these correlations and suggest that altered expression of these genes may be critical for the initiation and progression of this disease while their levels may predict bad response to traditional therapeutic approaches and poor clinical outcome. Finally, the defective circadian system may represent an attractive and currently unknown pathway which can be targeted by novel agents in aggressive colorectal cancers.