COMMENTARY Gap Junction Intercellular Communication Should Be

The paper by S. Ito and colleagues raises an important issue of increasing interest to scientists working in chem-ical carcinogenesis. Since the early report by Trosko and colleagues (2), alterations in intercellular communication, including some communication proteins such as the con-nexins, have received and continue to receive increasing study as a biochemical-molecular index of the promotion step in the carcinogenic process. The inhibition of gap-junctional intercellular communication (GJIC) is devel-oping into a pseudovalid assay for chemicals with pro-moting activity. Despite its popularity, there are at least 3 aspects of promotion that warrant the need for great reserve in re-lating GJIC to promotion. These concern (a) the presence of cell proliferation, (b) the striking increase in cell-to