Neveu M J, Sattler C A, Sattler G L, Hully J R, Hertzberg E L, Paul D L, Nicholson B J, Pitot H C
McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.
Mol Carcinog. 1994 Nov;11(3):145-54. doi: 10.1002/mc.2940110305.
Gap-junctional intercellular communication (GJIC) in normal rat liver cells involves at least three different connexins (Cxs)--Cx32, Cx26, Cx43--depending on the cell type, position in the lobule, or both. Whereas rat hepatocyte primary cultures expressed Cx32 and Cx26 as observed in vivo, cell lines derived from normal rat liver (WB-F344, Clone 9, RLEC, and BRL) expressed Cx43 and to a lesser extent Cx26. Hepatoma cells propagated in vitro were either deficient in GJIC and Cx expression (7777, 8994, H4IIE-C3) or communicated via gap junctions composed of Cx43 protein (N1S1-67, 9618A). Analysis of neoplasms that resulted from injection of hepatoma cells into rat femoral muscle showed differences in Cx expression when compared with cells grown in vitro. Whereas hepatoma cells 7777 and H4IIE-C3 failed to express Cx mRNAs in culture, these cells transplanted in vivo expressed levels of Cx32 mRNA comparable to those in normal liver. However, detectable Cx32 immunostaining was observed in less than 5% of the neoplastic cells in vivo. These results indicate that Cx32 protein was posttranscriptionally downregulated in 7777 and H4IIE-C3 tumor cells. Unexpectedly, 9618A cells expressed Cx43 mRNA and protein in cell culture but expressed Cx32 mRNA in vivo. In contrast, N1S1 transplants continued to express Cx43 mRNA and protein in vivo. Unlike the punctate Cx43 staining observed in suspension cultures of N1S1 cells, diffuse intracellular Cx43 staining was observed in N1S1-derived neoplasms in vivo, although the electrophoretic pattern of Cx43 isolated from N1S1 tumors grown in vivo (43 kDa) was different from that observed in suspension cell cultures (43 and 45 kDa). Thus, the findings reported here demonstrate that Cx expression in hepatoma cells depends on the environment, whether in vivo or in vitro, in which the cells are propagated.
正常大鼠肝细胞中的间隙连接细胞间通讯（GJIC）至少涉及三种不同的连接蛋白（Cx）——Cx32、Cx26、Cx43——这取决于细胞类型、在肝小叶中的位置或两者。与体内观察到的情况一样，大鼠肝细胞原代培养物表达Cx32和Cx26，而源自正常大鼠肝脏的细胞系（WB-F344、Clone 9、RLEC和BRL）表达Cx43，且Cx26表达程度较低。体外培养的肝癌细胞要么间隙连接细胞间通讯和连接蛋白表达缺陷（7777、8994、H4IIE-C3），要么通过由Cx43蛋白组成的间隙连接进行通讯（N1S1-67、9618A）。对将肝癌细胞注射到大鼠股四头肌中所形成肿瘤的分析表明，与体外培养的细胞相比，其连接蛋白表达存在差异。虽然肝癌细胞7777和H4IIE-C3在培养物中不表达连接蛋白mRNA，但这些细胞移植到体内后，其Cx32 mRNA表达水平与正常肝脏中的相当。然而，在体内不到5%的肿瘤细胞中观察到可检测到的Cx32免疫染色。这些结果表明，7777和H4IIE-C3肿瘤细胞中Cx32蛋白在转录后被下调。出乎意料的是，9618A细胞在细胞培养中表达Cx43 mRNA和蛋白，但在体内表达Cx32 mRNA。相反，N1S1移植瘤在体内继续表达Cx43 mRNA和蛋白。与在N1S1细胞悬浮培养物中观察到的点状Cx43染色不同，在体内源自N1S1的肿瘤中观察到弥漫性细胞内Cx43染色，尽管从体内生长的N1S1肿瘤中分离出的Cx43的电泳图谱（43 kDa）与在悬浮细胞培养物中观察到的不同（43和45 kDa）。因此，此处报道的研究结果表明，肝癌细胞中的连接蛋白表达取决于细胞生长的环境，无论是体内还是体外。
