肝癌细胞67kDa层粘连蛋白受体的表达

Expression of 67kD Laminin Receptor in Human Hepatocellular Carcinoma Cells

背景与目的:本实验室最近发现人肝癌细胞SMMC-7721表达的67kDa层粘连蛋白受体(67kDaLamininreceptor,67LR)与层粘连蛋白的结合能力明显高于正常肝细胞L-02表达的67LR,而67LR在肝癌细胞和正常肝细胞中的表达水平尚不清楚。本研究旨在探讨67LR在肝癌细胞中的表达,及其与层粘连蛋白结合能力的关系。方法:以人肝癌细胞SMMC-7721、HepG2和正常肝细胞L-02为材料,采用131I标记的层粘连蛋白测定其与细胞的结合能力;采用流式细胞术和RT-PCR分析67LR蛋白和mRNA的表达水平。结果:(1)相同条件下SMMC-7721、HepG2细胞与层粘连蛋白特异结合量分别为(17.54±0.49)ng/105cell、(11.18±0.53)ng/105cell,而L-02细胞的特异结合量为(8.36±0.48)ng/105cell,表明肝癌细胞与层粘连蛋白的结合能力明显高于正常肝细胞(P<0.01);(2)流式细胞术分析,SMMC-7721细胞的67LR阳性表达率为34.7%,L-02细胞的67LR阳性表达率为55.3%,而HepG2细胞则几乎不表达67LR;(3)RT-PCR产物进行半定量分析发现,两株肝癌细胞的67LRmRNA表达水平明显高于L-02细胞。结论:肝癌细胞与层粘连蛋白的结合能力明显高于正常肝细胞L-02,而细胞膜表面的67LR水平却低于L-02细胞,提示SMMC-7721细胞67LR的亲和力可能高于L-02细胞,而且还涉及其它层粘连蛋白受体。

BACKGROUND &OBJECTIVE: Previous study of our laboratory showed that 67kD laminin receptor (67LR) from SMMC 7721 hepatocellular carcinoma (HCC) cells had higher binding affinity with laminin than that from L 02 normal hepatic cells; however, the expression level of 67LR in HCC cells and normal hepatic cells was still unknown. The aim of this study was to investigate the relationship between laminin binding activity and the expression of mRNA and protein of 67kD laminin receptor in SMMC 7721,HepG2 HCC cells, and L 02 hepatic cells. METHODS:(1) The binding of laminin with three kinds of cells was quantified by 131I labeled laminin. (2)The expression of 67kD laminin receptor was determined by the reverse transcription polymerase chain reaction (RT PCR) and flow cytometry. RESULTS:(1) Under the same condition, the amount of radiolabelled laminin bound to SMMC 7721, HepG2 HCC cells was 17.54±0.49 ng per 105 cells and 11.18±0.53 ng per 105 cells, respectively, which were significantly higher than that to L 02 hepatic cells (8.36±0.48 ng per 105 cells). The binding of laminin with HCC cells is specific and saturable, and the cells bound exogenous laminin with high affinity. (2) 67 LR showed notably increased expression on the surface of L 02 hepatic cells (55.3%), compared with SMMC 7721 HCC cells (34.7%) by flow cytometry. HepG2 did not express membrance 67 LR. (3) The expression of 67LR mRNA in SMMC 7721 and HepG2 HCC cells was higher than that in L 02 cells. CONCLUSION: The conflict of laminin binding activity and the expression of 67 LR in the three cell lines suggested SMMC 7721 HCC cells may express 67 LR with higher laminin affinity than L 02 hepatic cells, and other laminin receptors were involved in laminin binding.