Abstract 1032: Impact of HOXC9 recapitulation on cancer biology and clinical outcome in gastric cancer

Abstract

Abstract The HOX genes encode transcription factors and may be implicated in the growth and the progression of many types of tumors. There are growing lines of evidence that dysregulation of HOX gene expression plays important roles in cancer. The aim of this study is to determine the level of HOXC9 expression during gastric cancer progression and the impact of its alteration on cancer biology and clinical outcome. HOXC9 expression was evaluated in normal mucosa, malignant legions, gastric cancer tissues by RT-PCR, western blot and immunohistochemistry. We established AGS gastric cancer cell in which HOXC9 was knock-down by shRNA and conditionally knock-down the HOXC9 expression by tetracycline-regulated gene expression (Tet-Off) system. The effect of HOXC9 knock-down on cell proliferation and apoptosis in AGS gastric cancer line were analyzed by tetrazolium salt-based proliferation assay (WST assay) and FACScan. Knockdown of HOXC9 by specific shRNA (67.3%) increased apoptosis, compared to scambled (7.3%) after 48 hours treatment of doxycycline, and increased active form of cellular apoptosis-related enzyme capsae-9, caspase-3 and poly (ADP-ribose) polymerase, whereas decreased expression of Bcl-xL, a mitochondria dependent anti-apoptosis factor. There was a gain or substantial increase of HOXC9 protein expression according to gastric cancer progression. Kaplan-Meier survival curves showed that HOXC9 overexpression is correlated with inferior disease-specific survival (P<0.001). multivariate Cox repression analysis revealed HOXC9 expression was an independent poor prognostic factor (Hazard ratio, 1.74; 95% CI, 1.01 to 2.99; P=0.047). We then demonstrated that HOXC9 directly regulated Bcl-xL transcription by binding to a HOXC9-responsive element in the Bcl-xL promoter by reporter gene assay, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA). In conclusion, these results suggest that HOXC9 overexpressed in advanced gastric cancer setting and its expression should be useful as a prognostic marker in gastric cancer patients. HOXC9 dependent Bcl-xL overexpresion may be an important mechanism by which HOXC9 protects gastric cancer cells from apoptosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1032.