Oncogenes, inhibited intercellular communication and tumor promotion.

Homeostatic control of proliferation and differentiation is characteristic of normal, but not malignant, cells. Gap junction-mediated intercellular communication provides one mode of this homeostatic control for cells in physical juxtaposition. Many chemicals, both natural and human-made, can modulate the function of gap-junctional communication and by doing so, alter the control of proliferation and differentiation of cells. Many of these chemicals are known tumor promoters. Oncogenes appear to be highly conserved genes influencing proliferation and differentiation of cells. We have speculated that certain oncogenes might play a role in tumor promotion by their influence on the regulation of gap-junctional intercellular communication. If this hypothesis is correct, a mechanism would exist to unify radiation, chemical and viral carcinogenesis.