THE ROLE OF GAP JUNCTIONAL INTERCELLULAR COMMUNICATION IN NEOPLASIA

Gap junctions are comprised of proteinaceous, plasma membrane channels that link the interiors of adjacent cells and permit cells to directl y exchange small (<1,000 Daltons) molecules and ions. This exchange, t ermed gap junctional intercellular communication (GJIC), appears to be involved in growth regulation. Growth controlling factors may pass be tween cells through the junctions. The loss of gap junctions or impair ment of their permeability has been observed in many neoplastic cells and cells treated with growth promoting carcinogens and other agents. The loss of GJIG appears to be an important event in the conversion of a normal cell into a neoplastic one. On the other hand, the restorati on of GJIC in neoplastic cells by transfection with gap junction prote in (connexin) cyclic deoxyribonucleic acids (cDNAs) or by stimulating endogenous connexin gene expression has led to the reversal of the neo plastic phenotype. The biology of gap junctions and their role in grow th regulation and neoplasia are reviewed.