GJB2 and neoplasm: To further test the hypothesis that GJC plays a role in oncogene-mediated tumorigenesis, we scored tumor incidence in embryos injected with Cx26, a short connexin protein which lacks most of the intracellular regulatory region, and thus facilitates GJC by forming constitutively permeable gap junctions (Mesnil et al., 1997; Levin and Mercola, 1998).