INCREASED GAP JUNCTIONAL INTERCELLULAR COMMUNICATION CAPACITY AND CONNEXIN 43 AND 26 EXPRESSION IN RAT BLADDER CARCINOGENESIS

Many reports have suggested that gap junctional intercellular communic ation or gap junction proteins (connexins) could have tumor suppressio n characteristics. We investigated gap junctional intercellular commun ication capacity and connexin 26, 32 and 43 mRNA expression in four ra t bladder cell lines and the results were compared to their tumorigeni city. We also examined connexin expression in rat bladder carcinomas i nduced by 3,2'-dimethyl-4-aminobiphenyl or N-ethyl-N-(4-hydroxybutyl)n itrosamine (EHBN) and in normal bladders. There was clear tendency tha t cell lines with greater communication had stronger tumorigenicity an d more expression of connexin 26 or 43. We could not detect connexin 3 2 in these cell lines. In normal bladder tissue, connexin 43 expressio n was barely detectable and there was no detectable connexin 26. Howev er, in rat bladder carcinomas, especially the EHBN-induced carcinomas, abundant expression of both connexins was observed. These results ind icate that increased gap junctional intercellular communication capaci ty or increased connexin(s) expression may give a growth advantage in rat bladder carcinogenesis.