Study On Biological Function And Molecular Mechanism Of CLOCK Genes In Thyroid Cancer Occurrence And Progression

Background: Thyroid cancer is one of the most common malignant tumor in endocrine system. It has become one of the fastest growing solid tumor in the world.The serum tumor marker for diagnosis of thyroid cancer is extremely limited, so it is an urgent to explore new ones. Increasing evidences have indicated that circadian rhythm genes play important role in the occurrence and progression of colorectal cancer, breast cancer and so on. The CLOCK, BMAL1, and NPAS2 protein make of the positive regulatory elements, driving the production of circadian rhythm. It can also control the expression of many clock-controlled genes(CCGs), such as c-Myc, P53, and P21. In this way, these circadian genes play important role in tumor cell proliferation, invasion,metastasis and other important functions. But little study has been focused on its role in thyroid cancer. Our earlier study has found that CLOCK protein was up-regulated in thyroid papillary cancer tissue compared with normal thyroid tissue.These results suggest that the CLOCK gene may play an important role in the occurrence and progression of thyroid cancer, but the biological function and molecular mechanism has not yet been studied.Objective: In this study, we used si RNA technology to interfere the expressionlevel of the CLOCK gene in thyroid cancer cells. Then we analyzed the effect onbiological activity of thyroid cancer cells. We also analyzed the changes of P21, P53,and Cyclin D1. In this way, we want to study the biological function and molecularmechanism of CLOCK genes in thyroid cancer occurrence and progression.Methds:We used thyroid cancer cell BCPAP in this study. We designed si RNAbased on CLOCK gene, and transfected it into BCPAP cells with lipofecter 2000. Thecells was divided into 5 groups, including blank control group(KD group), single lipgroup(ZD group), single mock-si RNA group(SD group), negative control group(YDgroup), and interfere group(GS group). These groups were treated with different ways.Then we tested the efficiency of interference by Western Blot. Cell proliferation wereassessed by cell counting kit-8(CCK-8) assay. Cell adhesion was measured byfibronectin(FN). Cell apoptosis was measured by fluorescent activated cell sorter. Cellinvasion and migration were measured by Transwell assay. We also tested the changesof P21, P53, and Cyclin D1 proteins after interference by Western Blot.Results:1.Cell proliferation is lower in GS group than in GD group(P<0.05). There are no significant changes between ZD group, SD group, YD group and GD group(P>0.05).2. Cell apoptosis is higher in GS group than in GD group(P<0.05). There are no significant changes between ZD group, SD group, YD group and GD group(P>0.05).3. Cell adhesion is lower in GS group than in GD group(P<0.05). There are no significant changes between ZD group, SD group, YD group and GD group(P>0.05).4. Cell invasion and migration is lower in GS group than in GD group(P<0.05).There are no significant changes between ZD group, SD group, YD group and GD group(P>0.05).5. The expression level of P21 and P53 was higher in GS group than in GD group(P<0.05). The expression level of Cyclin D1 was lower in GS group than GD group(P<0.05).Conclusions:1. CLOCK gene can promote the apotosis of thyroid cancer cell, while it can inhibits the proliferation, invasion and metastasis of thyroid cancer cell.2. CLOCK gene can control the expression level of P21, P53 and Cyclin D1, and play important role in thyroid cancer occurrence and progression.