Unknown,Transcriptomics,Genomics,Proteomics

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Nkx2.1 represses a latent gastric differentiation program in lung adenocarcinoma

ABSTRACT: During cancer evolution, cellular differentiation programs become dysregulated. The transcription factor Nkx2-1 is a master regulator of pulmonary differentiation that is downregulated in poorly differentiated lung adenocarcinoma. Here we use conditional murine genetics to study the fate of lung epithelial cells upon loss of their master cell fate regulator. Nkx2-1 deletion in normal and neoplastic lung causes not only loss of pulmonary identity but also gastric transdifferentiation. Nkx2-1 maintains pulmonary identity by sequestering the Foxa1 transcription factor at lung-specific loci and inhibiting Foxa1 binding to gastrointestinal targets. Murine Nkx2-1-negative lung tumors mimic the mucinous subtype of human lung adenocarcinoma, which also exhibits gastric transdifferentiation. Nkx2-1-negative lung adenocarcinomas are dependent on the gastrointestinal gene Hnf4a for efficient initiation. Thus, loss of Nkx2-1 results in transdifferentiation rather than stable dedifferentiation in vivo, suggesting that inactivation of both active and latent differentiation programs may be required for tumors to reach a primitive, dedifferentiated state. The study was designed to compare the expression profiles of Nkx2-1-positive lung adenocarcinomas with tumors in which Nkx2-1 was deleted at the time of initiation or 6-7 months after initiation.

ORGANISM(S): Mus musculus

SUBMITTER: Charles Whittaker

PROVIDER: E-GEOD-36473 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Despite the high prevalence and poor outcome of patients with metastatic lung cancer, the mechanisms of tumour progression and metastasis remain largely uncharacterized. We modelled human lung adenocarcinoma, which frequently harbours activating point mutations in KRAS1 and inactivation of the p53-pathway2, using conditional alleles in mice3-5. Lentiviral-mediated somatic activation of oncogenic Kras and deletion of p53 in the lung epithelial cells of KrasLSL-G12D/+;p53flox/flox mice initiates lung adenocarcinoma development4. Although tumours are initiated synchronously by defined genetic alterations, only a subset become malignant, suggesting that disease progression requires additional alterations. Identification of the lentiviral integration sites allowed us to distinguish metastatic from non-metastatic tumours and determine the gene expression alterations that distinguish these tumour types. Cross-species analysis identified the NK-2 related homeobox transcription factor Nkx2-1 (Ttf-1/Titf1) as a candidate suppressor of malignant progression. In this mouse model, Nkx2-1-negativity is pathognomonic of high-grade poorly differentiated tumours. Gain- and loss-of-function experiments in cells derived from metastatic and non-metastatic tumours demonstrated that Nkx2-1 controls tumour differentiation and limits metastatic potential in vivo. Interrogation of Nkx2-1 regulated genes, analysis of tumours at defined developmental stages, and functional complementation experiments indicate that Nkx2-1 constrains tumours in part by repressing the embryonically-restricted chromatin regulator Hmga2. While focal amplification of NKX2-1 in a fraction of human lung adenocarcinomas has focused attention on its oncogenic function6-9, our data specifically link Nkx2-1 downregulation to loss of differentiation, enhanced tumour seeding ability, and increased metastatic proclivity. Thus, the oncogenic and suppressive functions of Nkx2-1 in the same tumour type substantiate its role as a dual function lineage factor. 23 cell lines derived from primary tumor or metastasis. 6 samples analyzed to determine the effect of Nkx2-1 knockdown on gene expression

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Nkx2.1 represses a latent gastric differentiation program in lung adenocarcinoma

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