Growing evidence shows that deregulation of the circadian clock plays an important role in the developmentof malignant tumors, including gliomas. However, the molecular mechanisms of gene chnages controllingcircadian rhythm in glioma cells have not been explored. Using real time polymerase chain reaction andimmunohistochemistry techniques, we examined the expression of two important clock genes, cry1 and cry2,in 69 gliomas. In this study, out of 69 gliomas, 38 were cry1-positive, and 51 were cry2-positive. The expressionlevels of cry1 and cry2 in glioma cells were significantly different from the surrounding non-glioma cells (P<0.01).The difference in the expression rate of cry1 and cry 2 in high-grade (grade III and IV) and low-grade (grade 1and II) gliomas was non-significant (P>0.05) but there was a difference in the intensity of immunoactivity forcry 2 between high-grade gliomas and low-grade gliomas (r=-0.384, P=0.021). In this study, we found that theexpression of cry1 and cry2 in glioma cells was much lower than in the surrounding non-glioma cells. Therefore,we suggest that disturbances in cry1 and cry2 expression may result in the disruption of the control of normalcircadian rhythm, thus benefiting the survival of glioma cells. Differential expression of circadian clock genesin glioma and non-glioma cells may provide a molecular basis for the chemotherapy of gliomas.
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