Homologous and heterologous gap-junctional intercellular communication (IC) was characterized in a panel of cell lines derived from selected stages of SENCAR mouse skin carcinogenesis. This panel included a “carcinogen-altered” cell line, 3PC, obtained from Ca2+-resistant primary adult keratinocytes after exposure to dimethylbenz(a)anthracene as well as cell lines obtained from early and late-stage papillomas and a squamous cell carcinoma (CA3/7) generated during standard in vivo initiation/promotion protocols (dimethylbenz(a)anthracene/12-O-tetradecanoyl-phorbol-13-acetate). Also studied was a cell line (B66BA) obtained from a metastatic lesion following benzo(a)pyrene-induced skin tumorigenesis. Intercellular communication was measured in low-calcium (0.05 mm) medium by quantitation of cell-cell transfer of microinjected fluorescent dye Lucifer Yellow CH. Homologous IC ability diminished progressively from 68 dye-coupled cells per injection for 3PC cultures, to between 21 and 54 dye-coupled cells per injection for three papilloma-derived cell lines, to six and three dye-coupled cells per injection for CA3/7 and B66BA cells, respectively. To test communication of these cells with their normal counterparts, heterologous IC was examined in cocultures with primary adult keratinocytes. Under the conditions used, normal cells established functional communication channels with each cell line tested, showing no selectivity. These results suggest that progressive loss of homologous but not heterologous IC capacity accompanies neoplastic development in mouse skin carcinogenesis.
This research was supported in part by Grant R01-CA-40534, National Cancer Institute, USPHS. Preliminary results of the work were presented at the 38th Annual Meeting of the Tissue Culture Association, Washington, DC, 1987 (see Ref. 56).