Factors affecting morphogenesis of normal gallbladder epithelial cells and those regulationg differentiation in gallbladder cancer cells.

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Rabbit gallbladder epithelial cells (RGEC) suspended in collagen gels form spherical cysts with morphologic polarity. EGF, HGF, epimorphin, and FCM promoted cyst maturation by accelerating the proliferation and aggregation of clear, polarized vesicles. In contrast, TGF-β1 markedly inhibited DNA synthesisin both monolayer and collagen gel cultures an promoted formation of branching structures in collagen gels. Furthermore, in the presence of EGF, TGF-β1 induced a drastic change in morphogenesis, with the formation of branching networks that showed cell-cell contact only at sites where branches touched. RGEC-forming multicellular cysts did not express vimentin but expressed significant amounts of cytoskeratin and regained junctional complexes. In contrast, TGF-β1 treated cells strongly expressed vimentin along with branching structures and showed decreases in cytokeratin expression and junctional complexes. Thus TGF-β1 induces a mesenchyme-like cell shape accompanied by cytoskeletal mole … More cular changes, with loss of both epithelial polarization and junctional complexes. These results suggest that the morphogenetic program of RGEC is likely tobe determined by the interaction of these peptides and the timing of their presence.To clarify the role of cell adhesion molecules in the morphology of gallbladder cancers, four human gallbladder cancer cell lines (GB-d1, KMG-C, GBK-1 and G-415) were eximined in vitro. They showed noticeably different morphologics in our standard gel cultures (SC). GB-dl and KMG-C formed cystic and spheroid structures, respectively, which seemed to represent well- and moderately-differentiated cancers, respectively. GBK-1 and G-415 showed branching and "pseudo-glandular" structures, respectively, 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 α-catenin was detected in GB-d1 and KMG-C, but not in GBK-1 and G-415 cells. 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 α-catenin expression between SC and FC.Immunostaining of GB-d1 revealed that these proteins were localized to the cell membrane. In contrast, heterogeneous localization of these proteins was detected in the spheroid structures of KMG-C, in both SC and FC.Electromicroscopic examination revealed that reestablishment of junctional complex was occurred only in GB-d1 cells cultured in FC.The formation of cystic structures in GB-d1 was completely inhibited by an antibody against human E-cadherin. Both expression of E-cadherin and its membranous localization are required for well-differentiated-type morphogenesis in gallbladder cancer cells. Less