Abstract
It has long been a common knowledge that gap junctional intercellular communication (GJIC) functions in a tumor–suppressive manner. Once a tumor has developed, the formation of gap junction (GJ) is severely impaired or abolished both among tumor cells and between a tumor cell and its normal counterpart, thus indicating that GJIC– mediated tumor–suppressive effects are produced not in developed tumors but during the early phase of carcinogenesis such as tumor promotion process, where precancerous cells are assumed to be normalized by GJIC with their surrounding non–cancerous cells in terms of cell proliferation. On the other hand, homologous GJIC between tumor cells plays tumor–suppressive roles in developed tumors resulting from carcinogenesis. To the contrary, recent studies are further unraveling the pro–oncogenic roles of GJ–independent connexin (Cx) proteins in tumor progression such as invasion and metastasis. In this review article, multi–directional functions of GJ and Cx are described and discussed.
