Nkx2-1 Represses a Latent Gastric Differentiation Program in Lung Adenocarcinoma

Abstract

SUMMARY Tissue-specific differentiation programs become dysregulated during cancer evolution. 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 determine how the identity of lung epithelial cells changes 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 conversion to a gastric lineage. Nkx2-1 is likely to maintain pulmonary identity by recruiting transcription factors Foxa1 and Foxa2 to lung-specific loci thus preventing them from binding gastrointestinal targets. Nkx2-1-negative murine lung tumors mimic mucinous human lung adenocarcinomas, which express gastric markers. Loss of the gastrointestinal transcription factor Hnf4α leads to de-repression of the embryonal protoncogene Hmga2 in Nkx2-1-negative tumors. These observations suggest that loss of both active and latent differentiation programs is required for tumors to reach a primitive, poorly differentiated state.

Foxa2 and Cdx2 cooperate with Nkx2-1 to inhibit lung adenocarcinoma metastasis

“…Subsequent loss of both the pulmonary and intestinal differentiation programs upon silencing of Nkx2-1, Foxa2, and Cdx2 expression is required for full progression to a cellular state of more primitive differentiation and higher metastatic potential. This hypothesis about redundancy is further corroborated by the results from a previous study in our laboratory, which showed that deletion of Nkx2-1 alone in the KP model of lung adenocarcinoma was not sufficient to promote metastasis (Snyder et al 2013). In fact, loss of Nkx2-1 expression early at tumor initiation led to activation of a gastric differentiation program driven by Hnf4α, Foxa1, and Foxa2 in these cancer cells.…”

“…First, knockdown of Nkx2-1 in nonmetastatic lung adenocarcinoma cells does not recapitulate all of the gene expression changes that occur during the transition from a nonmetastatic to a metastatic state (Winslow et al 2011). Moreover, Nkx2-1 deletion in KP lung adenocarcinomas was not sufficient to induce the metastasis program but instead unmasked a latent gastric differentiation state of the tumor cells (Snyder et al 2013). These observations indicate that, in addition to Nkx2-1, additional regulatory factors likely exist that govern the program necessary for full acquisition of metastatic potential.…”

YAP inhibits squamous transdifferentiation of Lkb1-deficient lung adenocarcinoma through ZEB2-dependent DNp63 repression

“…Glioblastoma stem cells could give rise to endothelial cells to facilitate tumour angiogenesis 32,33 . Nkx2-1 deletion promotes lung ADC to transdifferentiate towards gastric lineage 34 . Consistently, clinical studies have found convergent mutations in both ADC and SCC components from a single lesion of human Ad-SCC [35][36][37][38][39] , leading to the hypothesis that there exists dynamic cell lineage conversion between these two pathologically and morphologically distinct tumour subtypes.…”

Quantitative proteomics identify Tenascin-C as a promoter of lung cancer progression and contributor to a signature prognostic of patient survival

“…Whether the same relationship is true in humans remains to be proven, although it is likely, given that the human and mouse Nkx2-1 proteins share 98% identity, and that two of the Nkx2-1 binding sites that we identified in the murine Tnc promoter are conserved in the human Tnc promoter (peak 2, 75% identify; peak 3, 80% identify). Moreover, Tnc might not be the sole ECM factor regulated by Nkx2-1; analysis of existing Nkx2-1 ChIP-Seq data (20) identified potential Nkx2-1 binding sites within 4 kb of the transcriptional start sites of 14 of the 36 matrisomal proteins detected in differential abundance in KP lung tumors (Agrn, Col12a1, Col16a1, Ctsd, Fbln5, Hspg2, Lgals3, Ltbp2, Nid1, Nid2, Npnt, S100a11, Sftpb, Sftpd, Tnc). Further work is needed to confirm whether these genes are also transcriptionally regulated by Nkx2-1, and whether they affect metastasis.…”

“…5A), we hypothesized that Tnc also might be subject to Nkx2-1 repression. To examine this possibility, we analyzed Nkx2-1 chromatin immunoprecipitation sequencing (ChIP-seq) data (20) that identified Nkx2-1 binding sites in Kras-driven lung tumors, and discovered that Nkx2-1 binds the murine Tnc locus at four distinct regions near the transcription start site (Fig. 5B).…”