Which of the following is essential for tumor metastasis

Ref Harrison 17/e p 509; Robbins 9/e p305_306 Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other pas of the body ,the bloodstream or the lympatic system ,to do so malignant cells break away from the primary tumor and degrade protein of the extacellular matrix .one of the critical events required for metastasis is the growth of a new network of blood vessels called tumor angiogenesis Vacularisation is promoted by VEGF and bFGF and inhibited by angiostatin ,endostatin and tumstatin it has been found that angiogenesis inhibitors would therefore prevent growth of metastasis