Study On Expression Of Kai1/CD82 And Possible Mechanisms Of Its Down-regulation In Colorectal Carcinoma Cell Lines

The metastasis of human colorectal carcinoma (HCC) is a complicated process involving the interaction between carcinoma cells and the host. Kail gene,cloned in 1995,has been approved to related to the progress of many kinds of neoplasms. Its protein product,CD82,belongs to TM4SF (transmembrane four superfamily) or TST (terra span transmembrane) superfamily. The protein has four highly conserved hydrophobic domains spanning the liquid bilayer. Then two extracellular domains are formed,a smaller one named EC1 between TM1 and TM2,the other called EC2 between TM3 and TM4 with three potential N-glycosylation sites. The short N- and C- terminus lies in cytoplasm. According to the specialty of the structure,it may be predicted that the function of Kail gene come down to cell-cell adherence and cell-matrix connection. Previous studies also showed that the Kail contributed to increasing the carcinoma cells aggregation,decreasing the phagokinetic activity and invasive ability,but no influence of the cell proliferation.Although many efforts have been made to elucidate the role of Kail gene in many kinds of carcinoma,there are little reports concerning the role of Kail in human colorectal carcinoma,especially regarding the mechanism of its down-regulation in metastasis carcinoma. In present study,the expression of Kail was detected by in situ hybridization,immumohistochemistry and Western Blot in four cell lines of HCC with different metastatic potential. The results indicated that Kail/CD82 is higher expressed in HT29 and SW480 than in LoVo and HCT116 whatever in mRNA or protein level.The possible mechanism of down regulation of Kail was also analyzed. By PCR-SSCP,8 exons of Kail,exon 3 to exon 10,were screened in LoVo and HCT116 cell lines. The methylation of CpG islands in promoter region was analyzed,and the expression level of p53 was detected by IH and Western Blot. The results showed that mutation of the Kail gene,methylation of CpG islands and the abnormity of p53 are not related to low expression of Kail.In conclusion,this research has gotten some significant results:firstly Kail gene is highly related with the metastasis potential of colorectal carcinoma cells,secondly mutation of Kail gene,methylation of CpG islands in the promoter and abnormal expression of p53 have no important effects in the down-regulation of Kail gene.