Anti-angiogenic mechanisms and efficacy of the low molecular weight heparin, tinzaparin: Anti-cancer efficacy

Inhibitors of angiogenesis are potential anti-cancer agents in that they deprive tumors of the blood necessary for growth and metastasis. The anti-angiogenic efficacy of tinzaparin, a known anticoagulant low molecular weight heparin (LMWH), was examined in vitro in endothelial cell tube formation assay and in vivo in the chick chorioallantoic membrane model. The observed anti-angiogenic effects of tinzaparin were shown to be dose-related and dependent on the relatively higher molecular weight tinzaparin fragments. These experiments demonstrated that tinzaparin is a potent inhibitor of angiogenesis (ED90-100 range, 0.05-0.1 mg) regardless of the angiogenic factor and suggest that its effect is mediated via cellular release of tissue factor pathway inhibitor (TFPI). This was evident by the reversal of either tinzaparin or r-TFPI anti-angiogenesis efficacy by a specific monoclonal TFPI antibody. The ED90-100 for the inhibition of angiogenesis for r-TFPI ranged from 0.01 to 0.03 mg in the chorioallantoic membrane model regardless of the proangiogenic factor. In addition, either tinzaparin or r-TFPI inhibited the growth of colon carcinoma tumors, human fibrosarcoma tumors, and human lung carcinoma in the chorioallantoic membrane tumor implant model. Thus, the LMWH tinzaparin, in addition to its anticoagulant effects, may offer important benefits in treatment of cancer and other disorders supported by pathologic angiogenesis.