In brain metastases of breast and lung cancer, PCDH7 promotes Cx43-mediated gap junctions between cancer cells and astrocytes, facilitating cGAMP transfer, which induces IFNα and TNFα production in astrocytes and, thereby, activates STAT1 and NF-κB pathways in cancer cells by a paracrine mechanism, driving tumor growth and conferring chemotherapy resistance (12). Here, IFNA1 is linked to cancer.