CacyBP/SIP Through CDK8 Regulates Cell Cycle Of Colon Cancer

Objective The incidence of colon cancer has increased yearly,but the pathogenesis is unknown.Calcyclin-binding-protein/Siah-1 Interacting Protein(CacyBP/SIP)which is involved in the development of various tumors and associated with metastatic prognosis plays an important role in cell proliferation of colon cancer.Gene chip screening found that CacyBP/SIP may be associated with Cyclin-dependent kinase 8(CDK8)in colon cancer.In this study,to study the mechanism of colon cancer and develop new drugs for colon cancer,we examined the relationship between CacyBP/SIP and CDK8 in colon cancer and explored that CacyBP/SIP controls the cell cycle of colon cancer through CDK8.Methods Gene chip screening found that CacyBP/SIP may be associated with CDK8 in colon cancer.The expression of CacyBP/SIP and CDK8 in normal tissues and colon cancer tissues was verified by Oncomine database search and immunohistochemistry(IHC).Construction of a SW480 colon cancer stable cell line with low expression of CacyBP/SIP,which also could be called SW480-CacyBPsh-1 cells.The mRNA and protein expressions of CacyBP/SIP,CDK8 and ?-catenin in SW480,SW480-NC and SW480-CacyBPsh-1 cell lines were detected by q-PCR and Western blot,respectively,detecting the cell cycle of each group of cells by flow.Then,the above three groups cells were treated with PBS(control group)and MG132(E3 enzyme inhibitor),and the amount of CDK8 protein in each group was detected by Western blot.Finally,the SW480 cell line with low expression of Skp2 was constructed(SW480-Skp2sh-2),the mRNA and protein expressions of Skp2 and CDK8 inSW480,SW480-NC and SW480-Skp2sh-2 cell lines were detected by q-PCR and Western blot,respectively.Results In the Oncomine database,CacyBP/SIP is highly expressed in colon cancer,liver cancer,breast cancer and other cancer tissues.The differential expression ratio between colon cancer and normal colon tissue is 2.184;CDK8 is highly expressed in colon cancer,and the differential expression ratio between colon cancer and normal colon tissue is 2.585.Compared with colon cancer tissues,the expression of CacyBP/SIP is low in normal colon tissues of colon cancer patients,and the difference in histological scores is statistically significant(P<0.05)(1.71±0.49)VS.(0.91±0.48);the expression of CDK8 is low in normal colon tissues of colon cancer patients,and the difference in histological scores is statistically significant(P<0.05)(1.99 ± 0.36)VS.(0.65 ±0.62).Compared with SW480 cell line,the mRNA relative expression of CDK8 in SW480-CacyBPsh-1 cell line is low,and the difference is statistically significant(P<0.05)(4.90±0.55)VS.(1.04±0.13).The expression of its protein is also low;the mRNA relative expression of ?-catenin in SW480-CacyBPsh-1cell line is low,and the difference is statistically significant(P<0.05)(3.73±0.85)VS.(1.06±0.19),its protein expression is also low;the percentage of cells in the G0-1 phase increased in the SW480-CacyBPsh-1 cell line,and the difference was statistically significant(P<0.05)(46.79±2.56)% VS.(63.80±2.56)%.Compared to the PBS group,the amount of CDK8 protein is high in the SW480 cell line and the SW480-CacyBPsh-1 cell line in the MG132 group.Compared with SW480 cell line,the mRNA relative expression of CDK8 in SW480-Skp2sh-2 cell line is low,and the difference was statistically significant(P<0.05)(6.10±0.74)VS.(1.01±0.11);the amount of protein expressed is also low.Conclusion In colon cancer,CacyBP/SIP and CDK8 are highly expressed and CacyBP/SIP through CDK8 regulates cell cycle of colon cancer.Moreover,CacyBP/SIP can through E3 ubiquitin ligase-mediated regulation of CDK8 expression in colon cancer.