Cooperation of bcl-2 and myc in the neoplastic transformation of normal rat liver epithelial cells is related to the down-regulation of gap junction-mediated intercellular communication

The objectives of this study were to isolate several rat liver epithelial c ell clones containing the human bcl-2 and myc/ bcl-2 genes in order to stud y their potential cooperative effect on neoplastic transformation and gap j unction-mediated intercellular communication (GJIC) and to test the hypothe sis that the loss of GJIC leads to tumorigenesis, Using anchorage-independe nt growth as a surrogate marker for neoplastic transformation, we transfect ed both normal rat liver epithelial cells, WB-F344, and a WB-F344 cell line overexpressing v-myc with human bcl-2 cDNA, Those cell lines that only exp ressed v-myc or human bcl-2 were unable to form colonies in soft agar. Howe ver, those cell lines that overexpressed both v-myc and human bcl-2 showed varying ability to form colonies in soft agar, which did not correlate with their human bcl-2 expression level. In order to test if there was a correl ation between cell line growth in soft agar and the ability to communicate through gap junctions, we performed scrape load dye transfer and fluorescen ce recovery after photobleaching assays. Our results show that v-myc and hu man bcl-2 can cooperate in the transformation of normal cells, but the degr ee to which the cells are transformed is dependent on the cells' ability to communicate through gap junctions.