Tocilizumab inhibits IL-8 and the proangiogenic potential of triple negative breast cancer cells.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of the disease with lack of recognized molecular targets for therapy. TNBC cells are known to secrete high levels of the proinflammatory cytokines interleukin-6 (IL-6) and IL-8, which promote angiogenesis and favor the growth and spread of the disease. In the present study, we have shown that the humanized anti-IL-6 receptor tocilizumab (Actemra) is also a potent inhibitor of IL-8 in TNBC cells. Similar effect was also obtained by specific IL-6 inhibition either by small interfering RNA or by neutralizing antibody. Likewise, neutralizing IL-8 with specific antibody downregulated IL-8 and inhibited the IL-6/signal transducer and activator of transcription 3 and nuclear factor-κB pathways. Interestingly, simultaneous co-inhibition of IL-6 and IL-8 did not increase the effects of the single inhibitors. Additionally, we present clear evidence that tocilizumab has potent antiangiogenic effect. Indeed, tocilizumab abolished the ability of TNBC cells to induce the differentiation of endothelial cells into network-like tubular structures in vitro and impaired neovascularization in humanized breast orthotopic tumor xenografts. This was associated with tocilizumab-dependent downregulation of the main proangiogenic factor vascular endothelial growth factor A and its coactivator hypoxia-inducible factor 1 both in vitro and in vivo. Therefore, tocilizumab could be of great therapeutic value for TNBC patients through targeting angiogenesis.