A few monoclonal or polyclonal antibodies that recognize the extracellular domain of Cx43 have been generated (Meyer et al., 1992; Hofer and Dermietzel, 1998; Siller-Jackson et al., 2008; Baklaushev et al., 2009, 2011) and used in diverse contexts to address biological questions regarding gap junction assembly and hemichannel function [reviewed in Riquelme et al. (2013)], as well as for the potential treatment of cancer and inflammatory states (Jiang et al., 2018). This evidence concerns the gene GJA1 and cancer.