Studies on the expression, induction and mutation of connexin genes in human gastric cancer

OBJECTIVE: To study: (i) the expression of connexin (Cx) genes; (ii) the effects of inducers on Cx expression; and (iii) the effects of mutations in Cx coding sequences in human gastric cancer. METHODS: Northern blots, reverse transcription– polymerase chain reaction and polymerase chain reaction–single strand conformational polymorphism were the techniques used. RESULTS: There were regular expression patterns of the Cx genes in normal human gastric epithelium, paracancerous tissues and gastric cancers. Retinoic acid (RA) and dimethyl sulfoxide induced the expression of Cx43 in gastric cancer but Cx46 expression was reduced when induced by RA and 12-O-tetradecanoylphorbol-13-acetate (TPA). There were no mutations found in the Cx43 coding region. CONCLUSIONS: The Cx32 gene might specifically maintain intercellular communication via gap junctions in the gastric epithelium. Cx43 is an inducible gene in gastric cancer cells. The reduced expression of Cx43 is not caused by mutation of the Cx coding region. A hypothesis explaining the variation in Cx gene expression in human gastric cancer is proposed.