Nevertheless, it is not easy to sum up the role of gap junctions in cancer in a single sentence: For many tumors, malignancy was associated with downregulated connexin expression (Cx43 in prostate [21], pancreatic [22] and breast cancers [23]; Cx26 in colorectal [24] and some gastric cancers [25]). This evidence concerns the gene GJA1 and breast carcinoma.