W. Jiao et al., Exogenous expression of E-cadherin in gallbladder carcinoma cell line G-415 restores its cellular polarity and differentiation, INT J ONCOL, 19(6), 2001, pp. 1099-1107
E-cadherin (E-cad) is critical for the development and maintenance of polar
ity and differentiation of epithelial cells. Our previous study revealed ga
llbladder (GB) cancer cell lines expressing E-cadherin could form cystic or
spheroid-like structures in a 3-D matrix. This differentiated phenotype wa
s disrupted by addition of anti-E-cad antibody. By extrapolation, we postul
ated that E-cad might directly regulate epithelial morphogenesis in GB carc
inoma. In the present study, we introduced an expression plasmid harboring
mouse E-cad cDNA (pBATEM2) into an undifferentiated GB cancer cell line (G-
415) which did not express E-cad. We systemically compared differences incl
uding cell phenotype, morphogenesis, and ultrastructure between the parenta
l G-415 cells (parental-cells) and E-cad transfected cells (E-cad-cells) un
der various conditions such as monolayer culture, 3-D gel culture as well a
s inoculation of nude mice. In contrast to parental-cells, E-cadcells prese
nted a typical epithelial shape with tight intercellular connections in mon
olayer culture. They developed round multicellular cystic structures in 3-D
gel. The cysts secreted mucous substances via the apical surface into the
cystic lumen, in which the substances were positively stained by alcian blu
e (pH 2.5). Ultrastructural sections of gel/xenograft tumor revealed reesta
blishment of adherens junctions and restoration of cell polarization. Immun
ohistochemical and immunofluorescent staining showed exogenous E-cad primar
ily accumulated at the extended cell-cell contact sites. Moreover, the memb
ranous translocation of alpha-, and beta -catenin from cytoplasm was also f
ound in 3-D matrix and xenograft tumor sections. Histopathologic examinatio
n revealed papillary adenocarcinoma features in the central region of the x
enograft tumors. Our results demonstrate that exogenous expression of E-cad
in undifferentiated GB cancer G-415 cells reverses differentiated characte
ristics in spatial growth conditions. Simultaneous translocation of alpha-,
beta -catenin to membrane following functional E-cad expression may be a c
ritical event for this process.