The targeting of endoglin on vascular endothelial cells affects the infiltration of M2 macrophages into the breast cancer microenvironment by modulating the interleukin-6 (IL-6) level

Breast cancer is the most common malignancy in women and the second leading cause of death in the world. The American Cancer Society estimates that 167,114 cases of breast cancer were newly diagnosed and 521,907 patients died of breast cancer in the US in 2012 (1). Most patients diagnosed early with breast cancer can achieve long-term survival, and some patients can achieve disease-free survival. However, advanced breast cancer is very difficult to treat. Chemotherapy plus anti-angiogenic therapy is an effective option for advanced breast cancer that improves the disease-free survival but not the long-term survival of patients (2-4). Many studies have discovered angiogenesis-related signalling pathways in tumours and have revealed that the blockade of a certain signalling pathway might activate other signalling pathways, and thereby enhance angiogenesis in a tumour, leading to failure of anti-angiogenic therapies (5,6). Recent studies have shown that anti-angiogenic therapies modulate the tumour microenvironment