Aberrant expression, function and localization of connexins in human esophageal carcinoma cell lines with different degrees of tumorigenicity

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Abstract
We have analyzed the level of mRNA expression and protein localization of the gap-junction protein connexins (Cx) 26, 32, and 43, as well as gap-junctional intercellular communication (GJIC) in seven human esophageal careinoma cell lines (TE series). These cell lines exhibited various degrees of tumorigenicity in nude mice; two (TE-1 and TE-8) formed progressively growing tumors, four (TE-2. TE-3, TE-9, and TE-13) developed non-progressing tumors and one (TE-10) showed no tumorigenicity. We found that normal human esophageal tissue expressed both Cx26 and Cx43 and that most of the cell lines expressed lower amounts of Cx26 and Cx43 mRNAs than normal human esophageal tissues or none at all. The co-expression of Cx26 and Cx43 mRNAs and proteins was observed only in two cell lines (TE-3 and TE-9) that showed a high level of GJIC and non-progressive tumor development. However, the non-tumorigenic cell line TE-10 did not express either connexin. A possible regulator of GJIC, E-cadherin, was expressed in all cell lines. These results suggest that aberrant expression and function of connexins are common among human esophageal carcinoma cell lines, but there is no quantitative relationship between connexin expression and tumorigenic properties of these cell lines.