The role of E-cadherin in the differentiation of gallbladder cancer cells

Cell adhesion molecules are essential for development and maintenance of ep ithelial architecture. To clarify the role of these molecules in the morpho logy of gallbladder cancers, four human gallbladder cancer cell lines (GB-d 1, KMG-C, GBK-1, and G-415) were examined in vitro. They showed noticeably different morphologies in our standard gel cultures (SC). GB-d1 and KMG-C f ormed cystic and spheroid structures, respectively, which seemed to represe nt well-differentiated and moderately differentiated cancers, respectively. GBK-1 and G-415 showed branching and "pseudoglandular" structures, respect ively, both of which seemed to indicate original dedifferentiated cancers. In floating gel culture (FC), only GB-d1 showed a highly increased tendency toward cyst formation. Expression of E-cadherin and alpha -catenin in the gallbladder cancer cell lines was investigated by Western-blotting analysis . Expression was detected in GB-dl and KMG-C, but not in GBK-1 and G-415 ce lls. Furthermore, E-cadherin expression in GB-d1 was 1.82 times greater in FC than in SC, while E-cadherin expression levels of KMG-C did not change. Neither GB-d1 nor KMG-C showed any difference in alpha -catenin expression between SC and FC. Immunostaining of GB-d1 revealed that these proteins wer e localized to the cell membrane. In contrast, heterogeneous localization o f these proteins was detected in the spheroid structures of KMG-C, in both SC and FC. Electronmicroscopic examination revealed that reestablishment of the junctional complex occurred only in GB-d1 cells cultured in FC. The fo rmation of cystic structures in GB-d1 was completely inhibited by an antibo dy against human E-cadherin. Both expression of E-cadherin and its membrano us localization are required for well-differentiated-type morphogenesis in gallbladder cancer cells.