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Cancers 2013, 5(1), 205-217;

Blood Outgrowth Endothelial Cells Increase Tumor Growth Rates and Modify Tumor Physiology: Relevance for Therapeutic Targeting

Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA
Vascular Biology Center and Division of Hematology-Oncology Transplantation, Department of Medicine, University of Minnesota Medical School, MN 72223, USA
Author to whom correspondence should be addressed.
Received: 26 January 2013 / Revised: 26 January 2013 / Accepted: 6 February 2013 / Published: 18 February 2013
(This article belongs to the Special Issue Tumor Stroma)
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Endothelial cell precursors from human peripheral blood have been shown to home to areas of neovascularization and may assist tumor growth by increasing or fortifying blood vessel growth. In the present study, the influence of these cells on tumor growth and physiology was investigated and the role of these cells as a therapeutic target or in determining treatment sensitivity was tested. After isolation from human blood and expansion in vitro, actively growing cells with verified endothelial phenotype (Blood Outgrowth Endothelial Cell, BOEC) were injected i.v. into tumor bearing mice for three consecutive days. The growth rate was significantly enhanced in relatively small RERF human lung tumors (i.e., less than 150 mm3) grown in immunocompromised mice by an average of 1.5-fold while it had no effect when injections were given to animals bearing larger tumors. There were no signs of toxicity or unwanted systemic effects. We also observed evidence of increased perfusion, vessel number, response to 15 Gy radiation and oxygenation in RERF tumors of animals injected with BOECs compared to control tumors. In addition, FSaII murine fibrosarcoma tumors were found to grow faster upon injection of BOECs. When FSaII tumors were subjected to a partial thermal ablation treatment using high intensity focused ultrasound (HIFU) there was consistently elevated detection of fluorescently labeled and i.v. injected endothelial precursors in the tumor when analyzed with optical imaging and/or histological preparations. Importantly, we also observed that BOECs treated with the novel anti-angiogenic peptide anginex in-vitro, show decreased proliferation and increased sensitivity to radiation. In vivo, the normal increase in FSaII tumor growth induced by injected BOECs was blunted by the addition of anginex treatment. It appears that endothelial precursors may significantly contribute to tumor vessel growth, tumor progression and/or repair of tumor damage and may improve the oxygenation and subsequent radiation response of tumors. We surmise that these cells are preferentially stimulated to divide in the tumor microenvironment, thereby inducing the significant increase in tumor growth observed and that the use of injected BOECs could be a viable approach to modulate the tumor microenvironment for therapeutic gain. Conversely, agents or approaches to block their recruitment and integration of BOECs into primary or metastatic lesions may be an effective way to restrain cancer progression before or after other treatments are applied. View Full-Text
Keywords: endothelial precursor cells; HIFU; BOEC; tumor oxygenation; radiation response endothelial precursor cells; HIFU; BOEC; tumor oxygenation; radiation response

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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Pagan, J.; Przybyla, B.; Jamshidi-Parsian, A.; Gupta, K.; Griffin, R.J. Blood Outgrowth Endothelial Cells Increase Tumor Growth Rates and Modify Tumor Physiology: Relevance for Therapeutic Targeting. Cancers 2013, 5, 205-217.

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