KrasG12D and Nkx2-1 haploinsufficiency induce mucinous adenocarcinoma of the lung

Abstract

Mucinous adenocarcinoma of the lung is a subtype of highly invasive pulmonary tumors and is associated with decreased or absent expression of the transcription factor NK2 homeobox 1 (NKX2-1; also known as TTF-1). Here, we show that haploinsufficiency of Nkx2-1 in combination with oncogenic Kras G12D , but not with oncogenic EGFR L858R , caused pulmonary tumors in transgenic mice that were phenotypically similar to human mucinous adenocarcinomas. Gene expression patterns distinguished tumor goblet (mucous) cells from nontumorigenic airway and intestinal goblet cells. Expression of NKX2-1 inhibited urethane and oncogenic Kras G12D -induced tumorigenesis in vivo. Haploinsufficiency of Nkx2-1 enhanced Kras G12D -mediated tumor progression, but reduced EGFR L858R -mediated progression. Genome-wide analysis of gene expression demonstrated that a set of genes induced in mucinous tumors was shared with genes induced in a nontumorigenic chronic lung disease, while a distinct subset of genes was specific to mucinous tumors. ChIP with massively parallel DNA sequencing identified a direct association of NKX2-1 with the genes induced in mucinous tumors. NKX2-1 associated with the AP-1 binding element as well as the canonical NKX2-1 binding element. NKX2-1 inhibited both AP-1 activity and tumor colony formation in vitro. These data demonstrate that NKX2-1 functions in a context-dependent manner in lung tumorigenesis and inhibits Kras G12D -driven mucinous pulmonary adenocarcinoma. IntroductionMucinous adenocarcinoma of the lung (formerly known as mucinous bronchioalveolar cancer) is pathologically classified as tumor cells with goblet cell morphology containing abundant intracytoplasmic mucin (1). Invasive mucinous adenocarcinoma of the lung has a higher malignant potential than do the more common types of lung adenocarcinoma, such as acinar or papillary adenocarcinoma. Mucinous adenocarcinoma of the lung is associated with decreased or absent expression of the transcription factor NK2 homeobox 1 (NKX2-1; also known as TTF-1) and the expression of mucins, including mucin 5AC, oligomeric mucus/gel-forming (MUC5AC). Genetically, approximately 76% of mucinous adenocarcinomas of the lung have KRAS mutations, a frequent mutation in lung adenocarcinoma associated with tobacco use (2), but mucinous adenocarcinoma of the lung is rarely associated with EGFR mutations. In contrast, nonmucinous lung adenocarcinoma is frequently associated with EGFR mutations (∼45%), but less frequently with KRAS mutations (∼13%; ref. 1).NKX2-1 plays a critical role in lung morphogenesis and respiratory epithelial-specific gene expression, including activation of surfactant proteins and repression of mucins (3, 4). The potential oncogenic role of NKX2-1 in the pathogenesis of adenocarcinoma of the lung was proposed by findings that a region of 14q13.3 containing NKX2-1, NKX2-8, and PAX9 was amplified in approximately 10% of human lung adenocarcinoma (5-7). Loss-offunction and gain-of-function studies in human lung carcinoma and transformed cells supporte...

CD74–NRG1 Fusions in Lung Adenocarcinoma

“…17, 18 ) in lung adenocarcinomas, for which our cohort was negative, and the fact that we found 4 positive cases in our validation cohort of 102 pan-negative lung adenocarcinomas, we estimate that the frequency of CD74-NRG1 in lung adenocarcinomas is approximately 1.7%; however, it is of note that our validation cohort was from an Asian population, so this frequency might be different in Caucasians. CD74-NRG1 occurred specifi cally in invasive mucinous lung adenocarcinomas of never smokers, a tumor type that is otherwise associated with KRAS mutations ( 14 ). In our cohort of limited size ( n = 15), CD74-NRG1 fusions accounted for 27% of invasive mucinous lung adenocarcinomas; together, KRAS mutations and CD74-NRG1 may therefore be considered the causative oncogenes in more than 60% of the cases.…”

“…2A ). Invasive mucinous lung adenocarcinoma is highly associated with KRAS mutations ( 14 ). Indeed, out of 15 invasive mucinous lung adenocarcinoma specimens (all derived from an East Asian population), six carried a KRAS mutation (40%), and four carried the CD74-NRG1 fusion (27%; Fig.…”

RhoB Determines Tumor Aggressiveness in a Murine EGFRL858R-Induced Adenocarcinoma Model and Is a Potential Prognostic Biomarker for Lepidic Lung Cancer

“…However, this apparent haplo insufficiency must not be generalized as other studies using Rhob KO and heterozygous mice did not report this effect (36) that may be restricted to some types of cancer and/or oncogenic stimuli. Interestingly, a recent study using a similar mouse model showed that the Nkx2-1 murine gene haplo insufficiency induced pulmonary tumors in an oncogenic Kras G12D context, but not in combination with oncogenic EGFR L858R (37). This observation confirms that partial loss of a specific gene does not have the same effect according to the oncogenic background, and then strengthens the close relationship between RhoB and EGFR.…”

Development and plasticity of alveolar type 1 cells

“…4G, Fig. S8A), reminiscent of the gene expression changes associated with the formation of mucinous adenocarcinomas upon loss of NKX2.1 (Winslow et al, 2011;Maeda et al, 2012;Snyder et al, 2013). These gene expression changes were confirmed by transcriptome profiling of FACS-purified control and mutant AT1 cells, which identified additional SOX2-suppressed AT1 cell markers (Fig.…”