NEOPLASTIC PHENOTYPE OF GAP-JUNCTIONAL INTERCELLULAR COMMUNICATION-DEFICIENT WB RAT-LIVER EPITHELIAL-CELLS AND ITS REVERSAL BY FORCED EXPRESSION OF CONNEXIN-32

Gap-junctional intercellular communication (CJIC) is involved in cellu lar growth control and is often reduced in neoplastic cells. In this s tudy, four GJIC-deficient rat liver epithelial cell lines (WB-aB1,WB-b A2, WB-cDG, and WB-dA2) were examined for altered growth and tumorigen icity in comparison with their GJIC-competent parental cell line, WB-F 344. WB-aB1 cells were also forced to express connexin 32 (Cx32) by tr ansduction with a Cx32 cDNA retroviral expression vector to help deter mine whether the restoration of GJIC could reverse their neoplastic ph enotype. WB-aB1 and WB-bA2 cells had faster population doubling times (PDTs) and higher saturation densities (SDs) than did WB-F344 cells. I n contrast, the growth of VVB-cD6 and WB-dA2 cells was not significant ly different from that of WB-F344 cells. WB-aB1 and WB-bA2 cells forme d tumors in male F344 rats, but WB-cDG and WB-dA2 cells did not. After transduction of WB-aB1 cells with Cx32, four stable clones (WB-a/32-3 , -8, -9, and -10) were isolated that had GJIC levels of 5.2%, 44.5%, 69.8%, and 90.5%, respectively. The growth of poorly coupled clones 3 and 8 was similar to that of parental WB-aB1 cells, but the growth of well-coupled clones 9 and 10 was similar to that of WB-F344 cells. The tumorigenicity of WB-a/32-9 and WB-a/32-10 cells was also significant ly lower than that of WB-aB1 cells. Our results suggest that reduced G JIC contributes to neoplastic transformation of WE cells, that additio nal changes are necessary, and that restoration of GJIC by forced Cx32 protein expression can suppress the neoplastic phenotype of these cel ls. Mel. Carcinog. 22:120-127, 1998. (C) 1998 Wiley-Liss, Inc.