ERBB2 and cancer: Sema4D has been shown to activate Erb-B2/ HER2 (through Plexin-B1) to promote breast cancer metastasis [48], and although TNBC would probably fail to respond similarly, it's blockade would be worth investigating in these malignancies as a supplemental treatment along with more conventional approaches, if not to block cancer growth then to inhibit skeletal metastasis.