The present invention relates to methods for treating brain metastasis by inhibiting gap junction functionality. It is based, at least in part, on the discovery that cancer cells expressing Protocadherin 7 and Connexin 43 form gap junctions with astrocytes that promote the growth of brain metastases, and that inhibition of Protocadherin 7 and/or Connexin 43 expression in cancer cells reduce progression of brain metastases. It is further based on the discovery that treatment with gap junction inhibitors tonabersat and meclofenamate inhibited progression of brain metastatic lesions and enhanced the anti-cancer activity of the conventional chemotherapeutic agent, carboplatin.