Dj. Fitzgerald et al., GAP JUNCTIONAL INTERCELLULAR COMMUNICATION AND CONNEXIN EXPRESSION INNORMAL AND SV 40-TRANSFORMED HUMAN LIVER-CELLS IN-VITRO, Cancer letters, 71(1-3), 1993, pp. 157-165
The gap junction intercellular communication (GJIC) capacity of two no
rmal human liver-derived epithelial cell strains and their SV40 large
T oncogene-transformed counterparts was examined. In homologous cultur
es the GJIC capacity of the transformed cells was considerably less th
an the parental cells. In heterologous cultures, transformed cells app
eared to be able to form GJIC channels with normal cells. Only non-tra
nsformed cells expressed connexin (cx) 43 gene and cx 26 or cx 32 tran
scripts were not detectable in any cell strains tested. When GJIC was
assayed in the presence of the phorbol ester tumour promoter 12-O-tetr
adecanoylphorbol-13-acetate (TPA), all four strains showed a marked se
nsitivity to TPA in inhibitory activity at 1-10 ng/ml. In contrast to
a rat liver epithelial cell line, this effect of TPA did not appear to
become refractory even after 24 h exposure. These studies demonstrate
that GJIC of human liver cells in culture can be decreased by viral o
ncogene and tumour promoter action. Such disturbance may be an importa
nt component of the carcinogenic activity of these agents.