Lung cancer is a leading cause of death in both men and women, accounting for approximately 160,000 deaths annually in the United States with over 1,000,000 new cases of lung cancer worldwide. Despite a number of clinical trials testing various compounds as chemopreventive agents, none were effective in reducing the risk of lung cancer. However, treatment of hypertensive patients with angiotensin converting enzyme (ACE) inhibitors reduced the risk of cancer, especially lung cancer. Inhibition of ACE activity decreases angiotensin II (Ang II) and increases the levels of both bradykinin and angiotensin-(1-7) [Ang-(1-7)]. We showed that Ang-(1-7) reduces vascular growth in vitro and prevents neointimal formation in vivo. More importantly, our preliminary studies showed that Ang-(1-7) markedly inhibits the growth of human lung cancer cells and reduces tumor growth in vivo. Thus, we propose that the antiproliferative response to Ang-(1-7) extends beyond its effects on vascular cells and that Ang-(1-7) inhibits the growth of cancer cells. The studies outlined in this application are designed to determine whether Ang-(1-7) inhibits the proliferation of human lung cancer cells and identify the molecular mechanisms involved in this regulation. Established cell lines of human lung carcinomas will be examined for growth inhibition following treatment with various doses of Ang-(1-7). Attenuation of cell growth will be assessed by 3H-thymidine incorporation into proliferating cells, reductions in cell number using the modified MTT assay, and cell cycle analysis by flow cytometry. The specificity of the antiproliferative response to Ang-(1-7) will be determined using other angiotensin peptides and receptor antagonists. The attenuation of lung cancer cell growth by Ang-(1-7) will be examined in mice with chemically-induced lung tumors, to demonstrate that Ang-(1-7) prevents or reduces lung tumor formation in vivo. Gene array analysis identified candidate genes regulated by Ang-(1-7) following mitogen stimulation of human lung cancer cells, including up-regulation of genes encoding tumor suppressors and cell death signals and downregulation of genes encoding signaling pathways stimulating cell growth. Regulation of specific genes and proteins by Ang-(1-7) will be assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) assays and Western blot hybridization, to determine their role in Ang-(1-7)-mediated lung cancer cell growth inhibition. The results of these studies will determine whether Ang-(1-7) effectively attenuates the proliferation of human lung cancer cells and identify the cellular pathways involved in the inhibitory response. The ultimate goal of this work is to determine whether administration of Ang-(1-7) or agents, which increase circulating Ang-(1-7) is an effective chemopreventive treatment for lung cancers.

R03CA103098

2003-07-01

2006-06-30