ST6GALNAC5 and breast carcinoma: Other gene signatures expressed in breast cancer cells that metastasize to the brain include COX2, HBEGF, and ST6GALNAC5, which mediate BBB migration [43]; PCDH7, involved in linkage and interaction of tumor cells with astrocytes [44]; and GRIN2B, particularly increased in triple-negative breast cancers and involved in coding the GluN2 subunit of the NMDAR [45].