GJA1 and neoplasm: Because Cx43 can influence HIF-1α protein expression and thereby abrogate HIF-1α-mediated transcriptional activity [16], we examined whether the difference in the HIF-1α protein expression and HIF-1α transcriptional activity between Cx43 shRNA-transfected and control vector-transfected tumor cells could influence HIF-1α transcriptional activity.