Expression of clock genes in patients with colorectal cancer

Recent studies have demonstrated the influence of clock genes in cell cycle regulation, cell proliferation, apoptosis and DNA damage recognition and repair. There is evidence suggesting the implication of clock genes in colorectal cancer (CRC) development and progression. The aim of this study is to evaluate the expression levels of clock genes in CRC and correlate them with patients' prognosis. Forty-two CRC samples (from 24 males and 18 females), their paired noncancerous tissues and 8 biopsies from healthy individuals were included. Quantitative real-time PCR was used to examine the expression levels of CLOCK1, BMAL1, PER1, PER2 and PER3 genes in all the samples. In the cancerous tissues CLOCK1 (p<0.0001) and BMAL1 (p<0.0001) expression levels were higher, while PER1 (p<0.0024) and PER3 (p<0.0001) expression levels were lower compared to matched healthy tissues. No difference was observed in the expression levels of PER2 (p=0.99). No correlation was found between clock gene expression and patients' clinicopathological characteristics or prognosis. The results suggest abnormal expression of CLOCK1, BMAL1, PER1 and PER3 genes in CRC but no correlation with patients' prognosis.