In addition to the full-length Cx43 protein, endogenous GJA1-20k (see cartoon in Figure S1A) is highly expressed in primary cardiomyocytes and astrocytes, as well as many cell lines including cancer models (Smyth and Shaw, 2013; Salat-Canela et al., 2014; Ul-Hussain et al., 2014). This evidence concerns the gene GJA1 and cancer.