CXCL8 and breast carcinoma: To investigate mechanism and to determine the effects of breast cancer-derived Sema4D on production of IL-8 by osteoblasts, we grew HOB in media conditioned by control MDA-MB-231 or cells with silenced Sema4D, with and without the Clostridium botulinum toxin C3, which inhibits activation of Rho signaling pathways, and examined IL-8 production by ELISA.