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Angiotensin-(1-7) Inhibits Growth of Human Lung Adenocarcinoma Xenografts in Nude Mice through a Reduction in Cyclooxygenase-2

¹ Hypertension and Vascular Research Center and Departments of ² Physiology and Pharmacology and ³ Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina

Requests for reprints: Patricia E. Gallagher, The Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1032. Phone: 336-716-4455; Fax: 336-716-2456; E-mail: pgallagh{at}wfubmc.edu.

Angiotensin-(1-7) [Ang-(1-7)] is an endogenous peptide of the renin-angiotensin system with vasodilator and antiproliferative properties. Our previous studies showed that Ang-(1-7) reduced serum-stimulated growth of human lung cancer cells in vitro through activation of a unique AT_(1-7) receptor. The current study investigates the effect of Ang-(1-7) on lung tumor growth in vivo, using a human lung tumor xenograft model. Athymic mice with tumors resulting from injection of A549 human lung cancer cells were treated for 28 days with either i.v. saline or Ang-(1-7), delivered by implanted osmotic mini-pumps. Treatment with Ang-(1-7) reduced tumor volume by 30% compared with the size before treatment; in contrast, tumor size in the saline-treated animals increased 2.5-fold. These results correlate with a reduction in the proliferation marker Ki67 in the Ang-(1-7)–infused tumors when compared with the saline-infused tumor tissues. Treatment with Ang-(1-7) significantly reduced cyclooxygenase-2 (COX-2) mRNA and protein in tumors of Ang-(1-7)–infused mice when compared with mice treated with saline as well as in the parent A549 human lung cancer cells in tissue culture. These results suggest that Ang-(1-7) may decrease COX-2 activity and proinflammatory prostaglandins to inhibit lung tumor growth. In contrast, the heptapeptide had no effect on COX-1 mRNA in xenograft tumors or A549 cells. Because Ang-(1-7), a peptide with antithrombotic properties, reduces growth through activation of a selective AT_(1-7) receptor, our results suggest that the heptapeptide represents a novel treatment for lung cancer by reducing COX-2. [Cancer Res 2007;67(6):2809–15]

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