Effect Of KAI1/CD82 On Laminin Receptor-Mediated Invasion And Metastasis Of Cholangiocarcinoma

Purpose: Tumor invasion and metastasis is a multistage process, involving adherence, movement and proliferation of tumor cells, degradation of extracellular matrix (ECM) and tumor angiogenesis. Laminin receptor (LNR) is a critical cellular adhesion molecule receptor, which plays an important role in mediation of tumor cells′adhesion with ECM. Although many efforts have been made to elucidate the role of LNR in many kinds of carcinoma, there are little reports concerning the mechanism of its up-regulation in metastasis carcinoma. KAI1/CD82, as the tumor metastasis suppressor, is involved in cell migration, adhesion, and synapse formation and is decreased in various tumors. Several studies have shown that KAI1/CD82 can reduceα6 andβ1 integrin cell surface expression, leading to the attenuation of cell-ECM adhesion. Previous reports have also illustrated that there was co-regulation and interaction between LNR andα6 integrin. Therefore, we hypothesize that the overexpression of LNR in carcinoma might due to the down-regulated expression of KAI1/CD82.Experimental Design: In the first part of the experiment, we examined the expression of KAI1/CD82 in surgical resection cholangiocarcinoma and normal tissues by immuno- histochemistry and assessed its correlation and clinic pathological significance. In the second part of the experiment, we examined the different expression of LNR in KAI1/CD82 cholangiocarcinoma by immunohistochemistry, and assessed the correlation of KAI1/CD82 and LNR. In the third part of the experiment, we transfected a recombinant plasmid vector containing KAI1/CD82 gene into QBC939 cell. The expression of KAI1/CD82 and LNR proteins were determined by immunocytochemistry and Western blot.Results:1. The positive rate of KAI1/CD82 protein in cholangiocarcinoma was 31.3%(15/48), which was lower than that of normal tissue (P<0.01). The positive rate of LNR protein in cholangiocarcinoma was 54.2%(26/48). In highly differentiated cholangiocarcinoma, the positive expression of KAI1/CD82 was high (P<0.05), while that of the LNR protein was low(P < 0.05). The positive expression of KAI1/CD82 in cholangiocarcinoma with metastasis was significantly lower than that in cholangiocarcinoma without metastasis (P<0.05), while the positive rate of LNR protein in cholangiocarcinoma with metastasis was significantly higher than that in cholangiocarcinoma without metastasis (P<0.05).2. The expression level of KAI1/CD82 protein in cholangiocarcinoma was negatively correlated with that of LNR protein (γ=-0.462, P<0.01).3. Eukaryotic expression plasmid vector of pIRES2-EGFP-KAI1/CD82 was designed and generated by molecular biological technology. Its quality was ensured by sequencing and identification.4. The plasmid vectors were transfected into QBC939 cells by cation liposomes. The high expression of KAI1/CD82 protein was observed by immunocytochemistry and Western blot (P<0.05).5. After pIRES2-EGFP-KAI1/CD82 transfected into QBC939 cell, the decreased expression of LNR protein was determined by immunocytochemistry and Western blot (P<0.05).Conclusions: The results demonstrate that KAI1/CD82 down-expression is a critical molecular marker of cholangiocarcinoma and is strongly associated with the invasion and metastasis of this tumor. The up-regulated expression of LNR protein in cholangio- caicinoma correlates with the decreased expression of KAI1/CD82 protein. It seems that the overexpression of LNR is regulated by down-regulated KAI1/CD82 in cholangiocarcinoma.