GJA1 and breast cancer: Brain metastases, on the other hand, were reportedly promoted by Cx43-based gap junctions forming between MDA-MB-231 BrM2 cancer cells, a brain metastatic variant of MDA-MB-231 cells generated by Massagué and his group [48], and astrocytes in a mouse model where MDA-MB-231 BrM2 cells were injected in the left cardiac ventricle of mice [49]; thus proposing a brain-protective role for pharmacological inhibition of gap junction formation in the brain of patients with advanced breast cancer.