Abstract 3921: Amplification of the TFAP2B gene and upregulation of its gene products promote human bronchial epithelial cell (HBEC) transformation and carcinogenesis

Abstract

Abstract We previously showed that the transcription factor AP2B (TFAP2B) protein could specifically bind to the promoter of human telomerase reverse transcriptase (hTERT) and selectively activate hTERT in lung cancer cells but not in normal cells. The common 5p15.33 and 6p21.33 chromosomal variants that harbor the hTERT and TFAP2B genes, have been identified as susceptibility loci for lung cancer and show a significant autosomal copy number gain in lung adenocarcinoma. We tested the hypothesis that amplification of the TFAP2B gene and up-regulation of its gene products can transform lung cells and promote tumorigenesis. We first analyzed levels of TFAP2B gene expression in human lung cancer cell lines, small-airway epithelial cells (SAECs),primary normal HBEC and in immortalized or transformed HBECs by gene expression profiling on gene microarrays. Levels of TFAP2B gene expression varied significantly between different cell lines but on average were greater than those of primary normal HBECs and SAECs. A linkage distance cluster analysis of the TFAP2B pathway-associated genes showed a significant classification of lung cancer cell types, distinguishing tumor cells from normal ones. Differential expression of the TFAP2B gene in normal lung and cancer cells was confirmed by qRT-PCR. We analyzed copy number variations (CNVs) specifically linked to hTERT and TFAP2B loci by mining the published genome-wide SNP data set from 370 NSCLC tumor samples and confirmed a significant copy number gain for both hTERT and TFAP2B with average copy numbers of 4.5 and 3.5, respectively. We performed immunohistochemical (IHC) analysis of TFAP2B protein expression in 30 paired human lung tumors and normal lung tissues that are immediately (<1.0 cm) adjacent or distal (2-3 cm) to the tumor sites. Significantly up-regulated TFAP2B protein expression was detected in almost all the adenocarcinomas and squamous carcinomas and significantly reduced expression was observed in the immediately adjacent normal lung and HBECs and the distal normal lung and HBECs. The differential TGFAP2B protein expression patterns shown by the IHC analysis were confirmed by Western blot analysis. We performed immuno-fluorescence imaging analysis of the endogenous TFAP2B expression and detected distinctive subcellular and nuclear localization in normal HBECs compared to tumor cells. Ectopic activation of TFAP2B by wt-TFAP2B gene transfer significantly altered the cellular and nuclear compartmentalization and architecture. Activation of TFAP2B in stable clones of normal HBECs induced clonogenecity of these cells compared to the parent cells. Our results suggest an important role of TFAP2B in lung cancer carcinogenesis and potential translational applications using TFAP2B as a novel biomarker for lung cancer and as a therapeutic target. (Supported by NIH SPORE P50CA70907 and RO1CA116322 grants) 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 3921.