Thyroid-Specific Transcription Factors and Their Roles in Thyroid Cancer

Homeodomain, forkhead domain, and paired domain-containing transcription factors play a major role in development, tissue-specific gene expression, and tissue homeostasis in organs where they are expressed. Recently, their roles in stem cell and cancer biology are emerging. In the thyroid, NKX2-1, FOXE1, and PAX8 transcription factors are responsible for thyroid organogenesis and expression of thyroid-specific genes critical for thyroid hormone synthesis. In contrast to their known roles in gene regulation, thyroid development and homeostasis, their involvement in stem cell, and/or cancer biology are still elusive. In order to further understand the nature of thyroid cancer, it is critical to determine their roles in thyroid cancer

Regulation of mouse Scgb3a1 gene expression by NF-Y and association of CpG methylation with its tissue-specific expression

<p>Abstract</p> <p>Background</p> <p>Secretoglobin (SCGB) 3A1 is a secretory protein of small molecular weight with tumor suppressor function. It is highly expressed in lung and trachea in both human and mouse, with additional tissues expressing the protein that differ depending on the species. However, little is known about the function and transcriptional regulation of this gene in normal mouse tissues.</p> <p>Results</p> <p>By reporter gene transfection and gel mobility shift analyses, we demonstrated that expression of the mouse <it>Scgb3a1 </it>gene is regulated by a PU-box binding protein and a ubiquitous transcription factor NF-Y that respectively binds to the PU-boxes located at -99 to -105 bp and -158 to -164 bp, and the "CCAAT" binding sites located at -425 to -429 bp and -498 to -502 bp from the transcription start site of the gene. However, the effect of PU-box binding protein on transcriptional activation is minimal as compared to NF-Y, suggesting that NF-Y is a more critical transcription factor for mouse <it>Scgb3a1 </it>gene transcription. Despite that NF-Y is a ubiquitous factor, <it>Scgb3a1 </it>is highly expressed only in mouse lung and mtCC cells that are derived from SV40 transformed mouse Clara cells, but not in ten other mouse tissues/cells examined. Gene methylation analysis revealed that within 600 bp of the <it>Scgb3a1 </it>gene promoter region, there are nine CpG methylation sites present, of which two CpGs closest to the transcription start site of the gene are unmethylated in the tissues/cells expressing SCGB3A1.</p> <p>Conclusion</p> <p>A ubiquitous transcription factor NF-Y binds to and activates expression of the mouse <it>Scgb3a1 </it>gene and tissue-specific expression of the gene is associated with CpG methylation of the promoter.</p

Induction of uteroglobin-related protein 2 (Ugrp2) expression by EGF and TGFα

AbstractUteroglobin-related protein 2 (UGRP2) is thought to play a role in inflammation and/or epithelial cell differentiation in the lung. Induction of Ugrp2 mRNA expression by epidermal growth factor (EGF) and transforming growth factor α was examined using mouse transformed lung Clara cell-derived mtCC cells. The EGF-induced increase of Ugrp2 occurred at the transcriptional level that required the EGF receptor and the activation of the ERK-MAPK and phosphoinositide-3 kinase pathways

Defects in Tracheoesophageal and Lung Morphogenesis inNkx2.1(−/−) Mouse Embryos

AbstractNKX2.1 is a homeodomain transcriptional factor expressed in thyroid, lung, and parts of the brain. We demonstrate that septation of the anterior foregut along the dorsoventral axis, into distinct tracheal and esophageal structures, is blocked in mouse embryos carrying a homozygous targeted disruption of theNkx2.1locus. This is consistent with the loss ofNkx2.1expression, which defines the dorsoventral boundary within the anterior foregut in wild-type E9 embryos. Failure in septation between the trachea and the esophagus inNkx2.1(−/−) mice leads to the formation of a common lumen that connects the pharynx to the stomach, serving both as trachea and as esophagus, similar in phenotype to a human pathologic condition termed tracheoesophageal fistula. The main-stem bronchi bifurcate from this common structure and connect to profoundly hypoplastic lungs. The mutant lungs fail to undergo normal branching embryogenesis, consist of highly dilated sacs that are not capable of sustaining normal gas exchange functions, and lead to immediate postnatal death.In situhybridization suggests reducedBmp-4expression in the mutant lung epithelium, providing a possible mechanistic clue for impaired branching. Functional deletion ofNkx2.1blocks pulmonary-specific epithelial cell differentiation marked by the absence of pulmonary surfactant protein gene expression. Altered expression of temporally regulated genes such asVegfdemonstrates that the lung inNkx2.1(−/−) mutant embryos is arrested at early pseudoglandular (E11–E15) stage. These results demonstrate a critical role forNkx2.1in morphogenesis of the anterior foregut and the lung as well as in differentiation of pulmonary epithelial cells

Regulation of Mouse Hepatic ␣-Amino-␤-Carboxymuconate-- Semialdehyde Decarboxylase, a Key Enzyme in the Tryptophan-Nicotinamide Adenine Dinucleotide Pathway, by Hepatocyte Nuclear Factor 4␣ and Peroxisome Proliferator- Activated Receptor ␣

ABSTRACT Nicotinamide adenine dinucleotide (NAD) plays a critical role in the maintenance of cellular energy homeostasis. ␣-Amino-␤-carboxymuconate--semialdehyde decarboxylase (ACMSD) is the key enzyme regulating de novo synthesis of NAD from L-tryptophan (Trp), designated the Trp-NAD pathway. Acmsd gene expression was found to be under the control of both hepatocyte nuclear factor 4␣ (HNF4␣) and peroxisome proliferator-activated receptor ␣ (PPAR␣). Constitutive expression of ACMSD mRNA levels were governed by HNF4␣ and downregulated by activation of PPAR␣ by the ligand Wy-14,643 ([4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid]), as revealed by studies with hepatic HNF4␣-null mice and PPAR␣-null mice, respectively. Transient transfection and electrophoretic mobility shift analyses showed an HNF4␣ binding site in the Acmsd gene promoter that directed transactivation of reporter gene constructs by HNF4␣. The Acmsd promoter was not responsive to PPAR␣ in transactivation assays. Wy-14,643 treatment decreased HNF4␣ protein levels in wild-type, but not PPAR␣-null, mouse livers, with no changes in HNF4␣ mRNA. These results show that Wy-14,643, through PPAR␣, posttranscriptionally down-regulates HNF4␣ protein levels, leading to reduced expression of the HNF4␣ target gene Acmsd

Activation of Intestinal Human Pregnane X Receptor Protects against Azoxymethane/Dextran Sulfate Sodium-Induced Colon Cancer s

ABSTRACT The role of intestinal human pregnane X receptor (PXR) in colon cancer was determined through investigation of the chemopreventive role of rifaximin, a specific agonist of intestinal human PXR, toward azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon cancer. Rifaximin treatment significantly decreased the number of colon tumors induced by AOM/DSS treatment in PXR-humanized mice, but not wild-type or Pxr-null mice. Additionally, rifaximin treatment markedly increased the survival rate of PXR-humanized mice, but not wild-type or Pxr-null mice. These data indicated a human PXR-dependent therapeutic chemoprevention of rifaximin toward AOM/DSS-induced colon cancer. Nuclear factor k-light-chain-enhancer of activated B cells-mediated inflammatory signaling was upregulated in AOM/DSS-treated mice, and inhibited by rifaximin in PXRhumanized mice. Cell proliferation and apoptosis were also modulated by rifaximin treatment in the AOM/DSS model. In vitro cell-based assays further revealed that rifaximin regulated cell apoptosis and cell cycle in a human PXR-dependent manner. These results suggested that specific activation of intestinal human PXR exhibited a chemopreventive role toward AOM/DSS-induced colon cancer by mediating anti-inflammation, antiproliferation, and proapoptotic events

Neuroepithelial Body Microenvironment Is a Niche for a Distinct Subset of Clara-Like Precursors in the Developing Airways

Clara cells of mammalian airways have multiple functions and are morphologically heterogeneous. Although Notch signaling is essential for the development of these cells, it is unclear how Notch influences Clara cell specification and if diversity is established among Clara cell precursors. Here we identify expression of the secretoglobin Scgb3a2 and Notch activation as early events in a program of secretory cell fate determination in developing murine airways. We show that Scgb3a2 expression in vivo is Notch-dependent at early stages and ectopically induced by constitutive Notch1 activation, and also that in vitro Notch signaling together with the pan-airway transcription factor Ttf1 (Nkx2.1) synergistically regulate secretoglobin gene transcription. Furthermore, we identified a subpopulation of secretory precursors juxtaposed to presumptive neuroepithelial bodies (NEBs), distinguished by their strong Scgb3a2 and uroplakin 3a (Upk3a) signals and reduced Ccsp (Scgb1a1) expression. Genetic ablation of Ascl1 prevented NEB formation and selectively interfered with the formation of this subpopulation of cells. Lineage labeling of Upk3a-expressing cells during development showed that these cells remain largely uncommitted during embryonic development and contribute to Clara and ciliated cells in the adult lung. Together, our findings suggest a role for Notch in the induction of a Clara cell-specific program of gene expression, and reveals that the NEB microenvironment in the developing airways is a niche for a distinct subset of Clara-like precursors.Molecular and Cellular Biolog

Activation of intestinal human pregnane X receptor protects against azoxymethane/dextran sulfate sodium-induced colon cancer

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Fat-Specific Protein 27/CIDEC Promotes Development of Alcoholic Steatohepatitis in Mice and Humans

Alcoholic steatohepatitis (ASH) is the progressive form of alcoholic liver disease and may lead to cirrhosis and hepatocellular carcinoma. We studied mouse models and human tissues to identify molecules associated with ASH progression, and focused on mouse fat-specific protein 27 (FSP-27)/human cell death-inducing DFF45-like effector C (CIDEC) protein, which is expressed in white adipose tissues and promotes formation of fat droplets

Wnt/β-Catenin Signaling Pathway Is a Direct Enhancer of Thyroid Transcription Factor-1 in Human Papillary Thyroid Carcinoma Cells

The Wnt/β-catenin signaling pathway is involved in the normal development of thyroid gland, but its disregulation provokes the appearance of several types of cancers, including papillary thyroid carcinomas (PTC) which are the most common thyroid tumours. The follow-up of PTC patients is based on the monitoring of serum thyroglobulin levels which is regulated by the thyroid transcription factor 1 (TTF-1): a tissue-specific transcription factor essential for the differentiation of the thyroid. We investigated whether the Wnt/β-catenin pathway might regulate TTF-1 expression in a human PTC model and examined the molecular mechanisms underlying this regulation. Immunofluorescence analysis, real time RT-PCR and Western blot studies revealed that TTF-1 as well as the major Wnt pathway components are co-expressed in TPC-1 cells and human PTC tumours. Knocking-down the Wnt/β-catenin components by siRNAs inhibited both TTF-1 transcript and protein expression, while mimicking the activation of Wnt signaling by lithium chloride induced TTF-1 gene and protein expression. Functional promoter studies and ChIP analysis showed that the Wnt/β-catenin pathway exerts its effect by means of the binding of β-catenin to TCF/LEF transcription factors on the level of an active TCF/LEF response element at [−798, −792 bp] in TTF-1 promoter. In conclusion, we demonstrated that the Wnt/β-catenin pathway is a direct and forward driver of the TTF-1 expression. The localization of TCF-4 and TTF-1 in the same area of PTC tissues might be of clinical relevance, and justifies further examination of these factors in the papillary thyroid cancers follow-up