Angiogenesis plays a fundamental role in human breast tumor progression. In fact, recent findings indicate that vascular density is a prognostic indicator of breast cancer disease status. Evidence is presented that the integrin αvβ3 is not only a marker of human breast tumor-associated blood vessels, but that it plays a significant role in human angiogenesis and breast tumor growth. To assess the role αvβ3-dependent angiogenesis in the progression of human breast cancer, we examined a SCID mouse/human chimeric model with transplanted full thickness human skin containing αvβ3-negative human breast tumor cells. This tumor induced a human angiogenic response as measured by vascular cell immunoreactivity with monoclonal antibodies LM609 and P2B1 directed to human αvβ3 and CD31, respectively. Intravenous administration of LM609 either prevented tumor growth or markedly reduced tumor cell proliferation within the microenvironment of the human skin. These LM609-treated tumors not only contained significantly fewer human blood vessels but also appeared considerably less invasive than tumors in control animals. These findings demonstrate that αvβ3 antagonists may provide an effective antiangiogenic approach for the treatment of human breast cancer.
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