Fig. 1

Mechanisms of tumor blood supply in supporting tumor growth, metastasis, and drug resistance. Angiogenesis, vasculogenesis, and intussusception contribute to tumor neovascularization and tumor growth. Tumors may also use alternative mechanisms, including vascular mimicry, by which tumor cells but not endothelial cells form vessel-like structures. These tumor cell-constituted vessel-like structures can be perfused with blood to form blood lakes that support tumor growth. Alternatively, tumor cells can also adopt pre-existing vasculatures in their surrounding tissues—a process called co-option—for growth and metastasis. It has been suggested that both vascular mimicry and co-option contribute to the development of anti-angiogenic drug resistance