This model suggests that metastatic breast cancer cells form functional heterocellular GJs composed of Cx43 with astrocytes, and transfer of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) from tumor cells to astrocytes through these GJs stimulates the production of inflammatory cytokines by the astrocytes [166]. This evidence concerns the gene GJA1 and breast carcinoma.