Expression of gap junction protein Cx43 in cultured human normal and malignant lung cells

Gap junctional intercellular communication-exchange of small molecules and ions between contiguous cells through membranous gap junctional channels-is essential for growth control and tissue homeostasis. This work concerns the functional expression of gap junction protein connexin 43 (Cx43) in normal human lung cells and the changes in lung carcinoma cells. By using Northern blot hybridization analysis and Cx43 immunocytochemical methods, it was observed that cultured normal human embryonic lung cells expressed a high level of Cx43 in both mRNA and protein levels. The Cx43 immunofluorescence was localized at cell membrane regions corresponding to the location of gap junctions. These normal lung cells were competent of intercellular communication function as detected by Lucifer yellow dye transfer. In contrast to normal cells, Cx43 mRNA and protein was not detectable in the carcinoma PG cell line. These tumor cells were defective of intercellular communication function. These results demonstrate that Cx43 is expressed in normal cultured human embryonic lung cells but not in lung tumor cells. The lack of intercellular communication in the lung tumor cell line correlates with dysfunctional intercellular communication. The suggestive role of Cx as a tumor suppersor gene is discussed.