Fig. 6.

Diagramatic illustrations of the relationship between tumor blood vessels, pro-angiogenic and anti-angiogenic factors. a Blood vessels with regularity and completeness depend on dynamic balance of pro-factors and anti- factors in normal tissues. b Abnormal vessels with chaos, leakage and feeble blood circulation are caused by imbalance of mediators in tumor tissue. c Blood vessels are repaired through neutralizing abundant pro-factors or increasing anti-factors under the guidance of angiogenic inhibitors. d Blood vessels in tumor tissue are destroyed by excessive inhibitors, which aggravates hypoxia within tumor tissue and hinders drug transportation