Angiostatin and endostatin: endothelial cell-specific endogenous inhibitors of angiogenesis and tumor growth.

Angiostatin and Endostatin are potent inhibitors of angiogenesis. These proteins are endogenously produced and specifically target endothelial cells resulting in angiogenesis inhibition. Recombinant preparations of these proteins inhibit the growth of metastases and regress primary tumors to dormant microscopic lesions. A variety of murine tumors as well as human breast, prostate and colon tumors in human xenograft models regress when treated with Angiostatin or Endostatin. Regression of tumors upon systemic treatment with these proteins is in part due to increased tumor cell apoptosis. Repeated cycles of Endostatin therapy lead to prolonged tumor dormancy without further treatment and are not associated with any apparent toxicity or acquired drug resistance.