Abstract
PURPOSE: Tumor hypoxia reduces the efficacy of radiation and chemotherapy as well as altering gene expression that promotes cell survival and metastasis. The growth factor receptor, Her2/neu, is overexpressed in 25-30% of breast tumors. Tumors that are Her2(+) may have an altered state of oxygenation, relative to Her2(-) tumors, due to differences in tumor growth rate and angiogenesis. METHODS: Her2 blockade was accomplished using an antibody to the receptor (trastuzumab; Herceptin). This study examined the effects of Her2 blockade on tumor angiogenesis, vascular architecture, and hypoxia in Her2(+) and Her2(-) MCF7 xenograft tumors. RESULTS: Treatment with trastuzumab in Her2(+) tumors significantly improved tumor oxygenation, increased microvessel density, and improved vascular architecture compared with the control-treated Her2(+) tumors. The Her2(+) xenografts treated with trastuzumab also demonstrated decreased proliferation indices when compared with control-treated xenografts. These results indicate that Her2 blockade can improve tumor oxygenation by decreasing oxygen consumption (reducing tumor cell proliferation and inducing necrosis) and increasing oxygen delivery (vascular density and architecture). CONCLUSIONS: These results support the use of trastuzumab as an adjunct in the treatment of breast tumors with chemotherapy or radiotherapy, as improvements in tumor oxygenation should translate into improved treatment response.