Expression of circadian clock genes in gastric cancer (GC) determined by real-time quantitative RT-PCR. Expression of the eight circadian clock genes in paired cancerous and noncancerous tissues from 29 GC patients. The y-axis represents the relative messenger RNA (mRNA) expression level. The value of mRNA expression in noncancerous tissue is designated 1, and the level of mRNA expression in cancerous tissues is calibrated to obtain the fold change in cancerous tissues. Statistical significance (p < 0.005) was evaluated with a t-test.