Abstract 2966: Amplification and activation ofGATA6sustain oncogenic lineage-survival in esophageal adenocarcinoma

Abstract

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Objective: To investigate the genomic amplification at chromosomal 18q11.2 in esophageal adenocarcinoma (EAC), to identify the selected-gene(s) in this amplicon and to define the potential oncogenic mechanism of the amplified gene(s). Background: Gene amplification is a tumor-specific event occurring during malignant transformation. Recent studies have proposed a lineage-dependency (lineage-addiction) model of human cancer whereby amplification of certain lineage transcription factors predispose a survival mechanism in the lineage-related tumor cells. Experiment designs: We utilized an integrative genomic strategy including arrayCGH, SNP arrays, expression and tumor tissue arrays to identify and investigate a recurrent gene amplification event at 18q11.2. We assayed the roles of the identified target gene GATA6 using colony formation assays and tumor cell implantation in SCID mice. The nature of GATA6 as a lineage-survival oncogene was investigated using ectopically expressed GATA6 in EAC cells and EAC cells with siRNA-mediated GATA6 knockdown. Assays of BrdU incorporation, BrdU/TUNEL, WST-1 proliferation, cell morphology, caspase 3/7 activity, PARP cleavage, Affymetrix expression arrays, antibody arrays, and western blot were all employed to determine the possible mechanisms for cell apoptosis upon GATA6 silencing in EAC cells. Results: We show that recurrent amplification at 18q11.2 occurs in 21% of EAC. Utilization of an integrative genomic strategy reveals a single gene, the embryonic endoderm transcription factor GATA6, as the selected target of the amplification. Overexpression of GATA6 is found in EACs that contain gene amplification. We find that EAC patients whose tumors carry GATA6 amplification have a poorer survival. We show that ectopic expression of GATA6 together with FGFR2 isoform IIIb increases anchorage-independent growth in immortalized Barrett's esophageal cells. Conversely, siRNA-mediated silencing of GATA6 significantly reduces both cell proliferation and anchorage-independent growth in EAC cells. We further demonstrate that induction of apoptotic/anoikis pathways is triggered upon silencing of GATA6 in EAC cells but not in esophageal squamous cells. We show that activation of p38α signaling and up-regulation of TRAIL death ligand are detected in apoptotic EAC cells upon GATA6 deprivation. Conclusion: Our studies indicate that selective gene amplification of GATA6 during EAC development and progression sustains oncogenic lineage-survival of esophageal adenocarcinoma. In light of the lineage-addiction model of human cancer, our present study suggests that therapeutic deprivation of GATA6 in GATA6-amplified EAC may improve patient survival. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2966. doi:1538-7445.AM2012-2966