For example, brain metastatic melanoma cells are surrounded by reactive astrocytes with morphological changes and expressing high GFAP levels in the brain tissue of either human patients or cancer mouse models [29] (Figure 1, Pathway 1); and direct contact with astrocytes confers the drug resistance on melanoma cells, which is inhibited by the treatment of CBX or Cx43-specific siRNA for astrocytes. Here, GJA1 is linked to melanoma.