Connexin Species Specificity Negative Growth Control of HeLa Cells by Connexin Genes: Updated Version

In order to examine whether different connexin gene species exert different degrees of tumor-suppressing activity, we characterized growth characteristics of a gap junction-deficient human cancer cell line, HeLa cells, before and after transfection with cDNA for three different connexins, connexin (ex) 26, ex 40, and ex 43. All transfected cell lines (3 clones transfected with the ex 26 gene, 2 clones with ex 40, and 1 with ex 43) showed establishment of gap junctional intercellular communication (GJIC). Two of the ex 26-transfected clones showed significantly slower growth compared with the parental HeLa cells. When transfectants were grown in soft agar, the three ex 26-transfected clones grew much less than the other transfectants and parent HeLa cells. When injected into nude mice, the two ex 26 clones which exhibited the highest amount of ex 26 transcript induced almost no tumors, whereas other transfectants, includ ing the ex 26 clone which exhibited the lowest amount of ex 26 transcript, were tumorigenic. Among transfectants of various connexin genes, there was no good inverse correlation between their GJIC and tumorigenicity. GJIC levels were significantly higher in tumors induced in nude mice by clone ex 26 A and E transfectants. These results suggest that all of the connexin genes examined could induce recovery of GJIC of HeLa cells, but only the ex 26 gene exerts strong negative growth control on HeLa cells; thus, this connexin gene may have different functions from other connexin genes.