The structure and function of intercellular junctions in cancer

Intercellular junctions are a set of structurally complex membrane components that are incorporated into the general plasma membrane at the sites of close cell-to-cell apposition. The primary function of some types of junctions, such as gap junctions, remains obscure; this is unfortunate because a considerable body of information on the occurrence, biochemical ultrastructure, and physical properties of junctions suggests that they probably do play a central role in important biological phenomena. The quantitative evaluations of the occurrence of junctions are subjective in most of the reports, although there are a few reports in which the data were obtained by quantitative electron microscopy techniques. There are a number of ways in which genes of neoplastic transformation may influence intercellular junction structure and function. Additional research is required to define the contribution of tumor gene products to the pathogenesis of junctional abnormalities in tumors and to elucidate the roles, if any, of these cell membrane defects in malignant growth.