Abstract 349: Molecular pathogenesis of mucinous adenocarcinoma of the lung.

Abstract

Abstract Human mucinous adenocarcinoma of the lung is a subtype of highly invasive pulmonary tumors and is associated with decreased or absent expression of the respiratory epithelium transcription factor NKX2-1 (NK2 homeobox 1, also known as TTF-1). Here, we show that haploinsufficiency of Nkx2-1 in combination with oncogenic Kras.G12D (hereafter; Kras.G12D;Nkx2-1+/-), but not with oncogenic EGFR.L858R, causes pulmonary tumors in transgenic mice that are phenotypically similar to human mucinous adenocarcinomas. Expression of both CK7 and CK20, biomarkers for human mucinous adenocarcinoma of the lung, were confirmed in lungs of the Kras.G12D;Nkx2-1+/- mice. Expression of mucins, such as MUC5AC, and mucin/metastasis-related protein AGR2 was observed in tumorigenic mucous cells in the Kras.G12D;Nkx2-1+/- mice as well as non-tumorigenic airway mucous cells induced by allergen; however, mucous cell master regulators, such as SPDEF and FOXA3, were seen only in the non-tumorigenic airway mucous cells but not in the tumorigenic mucous cells, indicating a distinct mucous gene regulation in the tumorigenic mucous cells. NKX2-1 cell-autonomously inhibited mRNA expression of MUC5AC and AGR2 in A549 human lung carcinoma cells that harbor a KRAS mutation. Chromatin immunoprecipitation with massively parallel DNA sequencing (ChIP-seq) analysis identified a direct association of NKX2-1 with the promoter and intron of MUC5AC and AGR2 genes in A549 cells, indicating that NKX2-1 functions as a transcriptional repressor for the mucous gene expression. The ChIP-seq analysis further revealed that NKX2-1 associated with the AP-1 binding element (TGAnTCA) as well as the canonical NKX2-1 binding element (CTTG). NKX2-1 inhibited AP-1-mediated activity and tumor colony formation in vitro, suggesting that NKX2-1 suppresses mutant KRAS-driven lung tumorigenesis in part by inhibiting AP-1 activity. These results demonstrate that NKX2-1 suppresses mutant KRAS-driven mucinous pulmonary adenocarcinoma in part by directly inhibiting expression of genes induced in mucinous tumors. Citation Format: Yutaka Maeda, Jeffrey Whitsett. Molecular pathogenesis of mucinous adenocarcinoma of the lung. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 349. doi:10.1158/1538-7445.AM2013-349