Characterization of the mouse epidermal growth factor promoter and 5'-flanking region. Role for an atypical TATA sequence

Association between epidermal growth factor (EGF) and EGF receptor gene polymorphisms and end-stage renal disease and acute renal allograft rejection in a Korean population

Purpose

Epidermal growth factor (EGF) has been found to be associated with the development and repair mechanisms of several renal diseases. In this study, we hypothesized that single nucleotide polymorphisms (SNPs) in EGF or its receptor genes might have an association with end-stage renal disease (ESRD) or acute renal allograft rejection (AR) in a Korean population.

Methods

Three-hundred and forty seven recipients of the first renal transplants for ESRD, including 63 AR patients along with 289 healthy adults were included in the study. Five EGF gene SNPs (rs11568835, rs11568943, rs2237051, rs11569017, and rs3756261) and four EGFR gene SNPs (rs1140475, rs2293347, rs1050171, and rs6965469) were analyzed. The genotypes of these SNPs were analyzed using the AxiomTM genome-wide human assay. Statistical analysis was performed using SNPStats and Haploview version 4.2 software. Multiple logistic regression models (codominant, dominant, recessive, and Log-additive) were used to estimate the odds ratio (OR), 95% confidence interval (CI), and P value.

Results

One SNP (rs11569017) in the EGF gene showed significant association with ESRD but not with AR. Another SNP (rs11568835) in the EGF gene showed significant association with susceptibility to AR but not with ESRD. One SNP (rs1050171) in the EGFR gene showed significant association with susceptibility to AR but not with ESRD.

Conclusion

Our findings suggest that SNPs in the EGF and EGFR gene may be associated with the risk of ESRD and AR development in the Korean population.

EGF rs11568835 G/A polymorphism is associated with increased risk of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune rheumatological disease thought to have substantial genetic contributions. Epidermal growth factor (EGF) can activate DNA synthesis and cellular proliferation. Early RA synovial fluid was characterized by significantly elevated levels stromal cell and macrophage-related cytokines including EGF. We therefore hypothesized that EGF polymorphisms may contribute to RA susceptibility in the Chinese population. We studied EGF rs11568835 G/A and EGF rs3756261 T/C polymorphisms in 520 patients with RA and 520 controls in a Chinese population. When the EGF rs11568835 GG homozygote genotype was used as the reference group, the AA genotype was associated with an increased risk for RA (AA versus GG, odds ratio [OR] = 3.64, 95% confidence interval [CI] = 1.19-11.17, p = 0.024), the GA or GA/AA genotype was not associated with the risk for RA (GA versus GG, OR = 0.99, 95% CI = 0.75-1.31, p = 0.931; GA + AA versus GG, OR = 1.06, 95% CI = 0.81-1.40, p = 0.659). EGF rs3756261 T/C was not associated with susceptibility to RA. These results provide the first positive evidence for an association between EGF rs11568835 G/A polymorphism and RA.

Leukotriene B4 type-1 receptor signaling promotes liver repair after hepatic ischemia/reperfusion injury through the enhancement of macrophage recruitment

Recruited macrophages play a critical role in liver repair after acute liver injury. Leukotriene B4 (LTB4) is a potent chemoattractant for macrophages. In this study, we investigated the role of LTB4 receptor type 1 (BLT1) in liver repair during hepatic ischemia/reperfusion (I/R) injury. BLT1-knockout mice (BLT1(-/-)) or their wild-type counterparts (WT) were subjected to partial hepatic I/R. Compared with WT, BLT1(-/-) exhibited delayed liver repair and hepatocyte proliferation accompanied by a 70% reduction in the recruitment of macrophages and a 70-80% attenuation in hepatic expression of epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1). Disruption of BLT1 signaling also reduced the expression of EGF by 67% on recruited macrophages expressing VEGFR1 in the injured liver. Treatment of WT mice with an EGF-neutralizing antibody delayed liver repair and reduced macrophage recruitment, compared with control immunoglobulin G (IgG). BLT1 signaling enhanced the expression of VEGF, VEGFR1, and EGF in isolated peritoneal macrophages in vitro. These results indicate that BLT1 signaling plays a role in liver repair after hepatic I/R through enhanced expression of EGF in recruited macrophages and that the development of a specific agonist for BLT1 could be useful for liver recovery from acute liver injury.

Functional epidermal growth factor gene polymorphisms and risk of gastric cancer

Epidermal growth factor (EGF) is critical in cancer progression and various genotypes of the EGF gene have been reported to be correlated with susceptibility to gastric cancer; however, the results are unclear. The aim of this study was to explore the associations of functional EGF gene polymorphisms and risk of gastric cancer in a Chinese population. We genotyped seven functional single-nucleotide polymorphisms (SNPs) of the EGF gene [rs3756261, rs11568835 and rs4444903 in the promoter region; rs11568943, rs2237051 and rs11569017 in the non-synonymous exon region and rs3733625 in the 3′ untranslated region (UTR)] in a hospital-based case-control study, including 387 gastric cancer cases and 392 healthy controls by polymerase chain reaction-ligation detection reaction (PCR-LDR) methods. We found that individuals carrying the AG/GG genotype of rs2237051 (Ile to Met) in the exon region had an increased risk of gastric cancer (adjusted OR=1.577; 95% CI=1.163–2.138), compared with the wild-type homozygous AA genotype. The heterozygous AG/GG genotype of rs3733625 in the 3′UTR demonstrated a protective effect (adjusted OR=0.690; 95% CI=0.501–0.951), compared with the homozygous AA genotype. In addition, the effects of the two SNPs were more evident in intestinal gastric cancer (P<0.05); however, this was not case for the diffuse type (P>0.05). These findings indicate that a change in amino acids from isoleucine to methionine of rs2237051 and rs3733625 in the 3′UTR may contribute to the etiology of intestinal gastric cancer in the Chinese population.

Activation of HER family signaling as a mechanism of acquired resistance to ALK inhibitors in EML4-ALK-positive non-small cell lung cancer

PURPOSE

Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKI) such as crizotinib show marked efficacy in patients with non-small cell lung cancer positive for the echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion protein. However, acquired resistance to these agents has already been described in treated patients, and the mechanisms of such resistance remain largely unknown.

EXPERIMENTAL DESIGN

We established lines of EML4-ALK-positive H3122 lung cancer cells that are resistant to the ALK inhibitor TAE684 (H3122/TR cells) and investigated their resistance mechanism with the use of immunoblot analysis, ELISA, reverse transcription and real-time PCR analysis, and an annexin V binding assay. We isolated EML4-ALK-positive lung cancer cells (K-3) from a patient who developed resistance to crizotinib and investigated their characteristics.

RESULTS

The expression of EML4-ALK was reduced at the transcriptional level, whereas phosphorylation of epidermal growth factor receptor (EGFR), HER2, and HER3 was upregulated, in H3122/TR cells compared with those in H3122 cells. This activation of HER family proteins was accompanied by increased secretion of EGF. Treatment with an EGFR-TKI induced apoptosis in H3122/TR cells, but not in H3122 cells. The TAE684-induced inhibition of extracellular signal-regulated kinase (ERK) and STAT3 phosphorylation observed in parental cells was prevented by exposure of these cells to exogenous EGF, resulting in a reduced sensitivity of cell growth to TAE684. K-3 cells also manifested HER family activation accompanied by increased EGF secretion.

CONCLUSIONS

EGF-mediated activation of HER family signaling is associated with ALK-TKI resistance in lung cancer positive for EML4-ALK.

Association between EGF promoter polymorphisms and cancer risk: a meta-analysis

EGF promoter polymorphisms are observed to modulate EGF levels and thought to have effect on susceptibility to various carcinomas but the results are inconsistent. In this meta-analysis, we assessed published studies of the association between three EGF polymorphisms and cancer risk from 21 studies with 14,609 subjects for EGF G61A, from two studies with 2,535 subjects for G-1380A and A-1744G, respectively. For EGF G61A, the contrast of homozygote (OR=0.80, 95% CI=0.65-0.98), allele (OR=0.90, 95% CI=0.81-0.99) and dominant model (OR=0.86, 95% CI=0.74-0.99) produced significant association among 21 studies with relatively large heterogeneity (Pheterogeneity<0.001). Through the stratified analysis, heterogeneity decreased significantly. In the stratified analysis by racial descent, the significant risks were found among Asians for homozygote contrast (OR=0.83, 95% CI=0.69-0.99, Pheterogeneity=0.506) and Americans for the contrast of homozygote (OR=0.50, 95% CI=0.30-0.84, Pheterogeneity=0.051), allele (OR=0.70, 95% CI=0.51-0.96, Pheterogeneity=0.008) and dominant model (OR=0.57, 95% CI=0.42-0.77, Pheterogeneity=0.28). No significant associations were found in all Caucasians genetic models. In the subgroup analyses by cancer types, for gastric cancer and esophageal cancer significant associations were found in all genetic models without heterogeneity. Significant risk was also found in the contrast of homozygote (OR=0.41, 95% CI=0.20-0.81, Pheterogeneity=0.184) and recessive model (OR=0.53, 95% CI=0.33-0.85, Pheterogeneity=0.384) for hepatoma and recessive model (OR=0.72, 95% CI=0.53-0.99, Pheterogeneity=0.474) for glioma. For EGF G-1380A and A-1744G, no significant associations were found in all genetic models. This meta-analysis suggests that the EGF G61A polymorphism most likely contributes to decreased susceptibility to cancers among Asians and Americans, and A allele may be a protective factor for gastric cancer, esophageal cancer, hepatoma and glioma. Both EGF G-1380A and A-1744G is marginally associated with cancer susceptibility.

Implantation-related expression of epidermal growth factor family molecules and their regulation by progesterone in the pregnant rat

The uterine expressions of epidermal growth factor(EGF) family are examined to elucidate their exact role(s) in rat pregnancy. EGF and its receptors' (EGF-R) mRNA levels increased significantly at implantation after which their expression gradually decreased. Heparin-binding EGF (HB-EGF) and transforming growth factor-alpha (TGF-alpha) showed a modest expression at gestation day (GD), GD4 and GD3, respectively, but were much strongly expressed at mid-pregnancy.Amphiregulin (Areg) was strongly expressed around implantation (GD4) and at mid-pregnancy (GD12).Treatment of pregnant rats with RU486 at GD5 or GD8 blocked the expression of all the genes, and administration of immature rats with progesterone (P4) induced the uterine expression of all the genes except HB-EGF. In addition, HB-EGF,TGF-alpha, and Areg proteins in the uterine and glandular epitheliums may participate in mid-pregnancy. Taken together, all of these activities are likely to be controlled by P4 in the uterus of pregnant rats.

The c-Jun NH2-terminal kinase is essential for epidermal growth factor expression during epidermal morphogenesis

The c-Jun NH(2)-terminal kinase (JNK) group of mitogen-activated protein kinases is activated in response to a wide array of cellular stresses and proinflammatory cytokines. Roles for JNK in the developing nervous system and T-cell-mediated immunity have been established by detailed studies of mice with compound mutations in the Jnk genes. However, little is known concerning the roles of JNK in other mammalian tissues. Mice lacking both of the ubiquitously expressed isoforms (JNK1 and -2) die during midgestation with neural tube closure defects and brain abnormalities. Here we show that JNK-deficient mice exhibit delayed epithelial development in the epidermis, intestines, and lungs. In addition, JNK-deficient mice exhibit an eyelid closure defect associated with markedly reduced epidermal growth factor (EGF) receptor function, and loss of expression of the ligand EGF. We further demonstrate that adult mice lacking either JNK1 or -2 display striking differences in epidermal proliferation and differentiation, indicative of distinct roles for these kinases in the skin. We conclude that JNK is necessary for epithelial morphogenesis and is an essential regulator of signal transduction by the EGF receptor in the epidermis.

Structure and expression of the ovine Hoxc-13 gene

HOXC-13 has an important role in controlling hair formation through regulating keratin differentiation-specific genes. In this study, we describe the isolation and characterisation of the Hoxc-13 gene from sheep wool follicles and its expression in the skin. We show that the gene organisation of ovine Hoxc-13 is similar to other homeobox genes of the Abd-B type I Homeobox class with two exons split by an intron next to the homeobox. The gene spans 7.5 kilobases (kb) and has a relatively large intron, which divides an open reading frame of 2361 nucleotides. The predicted ovine Hoxc-13 protein of 330 amino acids has over 97% sequence identity with the human and mouse proteins. A second novel transcript was identified, which could produce a truncated Hoxc-13 protein lacking 15 amino acids from the N-terminus. A positionally conserved Hoxc-13 binding site in the Hoxc-13 proximal promoters of sheep, human, mouse and newt suggests that Hoxc-13 expression is autoregulatory. Positionally conserved motifs for LEF-1 and Whn/Foxn1 suggest that Hoxc-13 may be a downstream target of these transcription factors known to regulate hair growth. In addition to expression in the follicle, we detected Hoxc-13 in cells of the blood sinus surrounding vibrissal follicles and in scattered cells in the upper dermis of the skin. Thus, in addition to a role in controlling transcription of hair keratins, Hoxc-13 may have other roles in skin function.

Specific protein-1 is a universal regulator of UDP-glucose dehydrogenase expression: its positive involvement in transforming growth factor-beta signaling and inhibition in hypoxia

UDP-glucose dehydrogenase (UGDH) is a key enzyme of the unique pathway for the synthesis of UDP-glucuronate, the substrate for the numerous glucuronosyl transferases, which act on the synthesis of glycosaminoglycans and glucuronidation reaction of xeno- and endobiotics. Using the bacterial artificial chromosome approach, we have cloned and characterized the human UGDH promoter. The core promoter of -644 nucleotides conferred reporter gene activity in transient transfection assay of a variety of cell types, including MRC5 fibroblasts and the HepG2 hepatoma cell line. The minimal promoter of -100 nucleotides contains a functional inverted TATA box. No consensus CAAT sequence was found up to -2133 nucleotides. The expression of UGDH was up- and down-regulated by transforming growth factor (TGF)-beta and hypoxia, respectively. TGF-beta enhanced the activity of all the deletion constructs, except the minimal promoter. Hypoxia slightly increased the activity of the short promoter-containing constructs but decreased that of the -374 nucleotides and core promoter constructs. The core promoter contained numerous GC-rich sequences for the binding of Sp1 transcription factor. Bisanthracycline, an anti-Sp1 compound, decreased UGDH mRNA expression and inhibited the core promoter constructs activity. Gel mobility shift and supershift assays after TGF-beta stimulation demonstrated an increased DNA binding of the nuclear extract proteins to the two Sp1 sequences located in the -374-bp promoter. By contrast, nuclear extract proteins from hypoxia-treated cells demonstrated a decreased binding of the consensus Sp1 sequence. These results indicate that numerous Sp1 cis-acting sequences of the UGDH core promoter are responsible for up- and down-regulation of the gene after TGF-beta stimulation and in hypoxic conditions, respectively.

Involvement of two NF-kappa B binding elements in tumor necrosis factor alpha -, CD40-, and epstein-barr virus latent membrane protein 1-mediated induction of the cellular inhibitor of apoptosis protein 2 gene

The antiapoptotic function of NF-kappaB is believed to be mediated through the induction of antiapoptotic genes. Among the antiapoptotic genes, cellular inhibitor of apoptosis protein 2 (c-IAP2/HIAP-1/MIHC) is originally identified as a molecule recruited to the tumor necrosis factor (TNF) receptor complex, and its expression is preferentially up-regulated by TNF and other stimuli activating NF-kappaB. However, direct evidence of transcriptional regulation of NF-kappaB on the c-IAP2 gene is still missing. Here, we have cloned and characterized the promoter region required for NF-kappaB-dependent transcription of the c-IAP2 gene. Sequencing of a 3.5-kilobase fragment of the 5'-flanking region of the c-IAP2 gene has identified a TATA-like sequence and potential binding sites for nuclear factor of activated T cells, interferon regulatory factor 1, activator protein 1, glucocorticoid response element, and three putative NF-kappaB binding elements. Deletion and mutational analysis of the 5'-flanking region linked to the luciferase gene revealed that transcriptional activation by TNF or interleukin 1 is mediated cooperatively by two NF-kappaB binding sites. Electrophoretic mobility shift assays characterized that the two NF-kappaB sites can be recognized and bound by the NF-kappaB p50/p65 heterodimer. In addition, the transcription of c-IAP2 promoter was strongly up-regulated when CD40 or Epstein-Barr virus latent membrane protein 1 was overexpressed.

DNA sequence and functional characterization of the human and rat epidermal growth factor promoter: regulation by cell growth

Epidermal growth factor (EGF) regulates cell growth and differentiation through intracellular transduction networks activated by its tyrosine kinase receptor, EGFR. In this report we describe the structure and DNA sequence of transcriptional control regions from both human and Wistar-rat single copy EGF genes and their functional analysis in epithelial cell cultures. By sequence comparison we show these proximal gene regions have remained conserved in evolution to -640 (relative to the rodent mRNA initiation site), where similarity is interrupted by a rodent interspersed-repeat element (SINE). Transcript mapping reveals complexity in EGF initiation site selection: whereas a single rat liver initiation site (+1) appears 30bp 3' to the TTTAA element, an additional upstream site is detected in kidney RNA at -14. In contrast, in human RNA a single initiation is observed, which is displaced 12bp 3' to the rodent RNA terminus. Both promoters were defined in transient expression assays. Our results show the human promoter to be at least 20-fold more active than the equivalent rodent sequence, although both are activated during cell proliferation and negatively regulated in contact inhibited and quiescent cultures. The results indicate EGF gene expression and cell division are temporally linked, suggesting its promoter comprises a growth responsive regulatory domain.

Testosterone and dihydrotestosterone regulate AUF1 isoforms in a tissue-specific fashion in the mouse

The sex difference in the metabolism of certain mRNAs in the murine submaxillary gland (SMG) prompted us to determine whether androgens regulate the expression of any of the four isoforms of AUF1, proteins that bind differentially to AU-rich RNA. We found that cytosol from female SMGs contains two major isoforms (p45 and p40), whereas cytosol from male SMGs contains a prominent p37 and a weaker p42. Injecting female mice with testosterone decreases p45 levels by 81% after 7 days (P < 0.05, n = 4), whereas p42 and p37 increase 74 and 449% at 7 days (P < 0.05, n = 4, for both). Orchiectomy, conversely, decreases p37 levels in the male SMG by 91% (P < 0.006) while increasing p45 5-fold and p40 2.5-fold (P < 0.05, n = 5 for both). Both male and female kidney cytosol contains a prominent p37 and a faint band of approximately 42 kDa, but neither shows a significant change when circulating androgen levels are altered. Dihydrotestosterone (DHT) changes the pattern of AUF1 isoforms in female SMG cytosol more rapidly than does testosterone. Nuclear extracts from female SMG contain predominantly p45, and DHT decreases its level slightly (35%, P < 0.05 at 24 h). Polysomal extracts from female SMG contain p45 and p42, and DHT increases p45 levels 58% (P < 0.02, n = 6) at 24 h. In certain nonreproductive tissues, androgens may differentially regulate AUF1 isoform levels to modulate the metabolism of AU-rich mRNAs posttranscriptionally.

Characterization of the murine A1 adenosine receptor promoter, potent regulation by GATA-4 and Nkx2.5

Adenosine acts via A1 adenosine receptors (A1ARs) in the heart and brain to potently influence mammalian physiology. A1ARs are expressed very early in embryonic development, and A1ARs are among the earliest expressed G protein coupled receptors in the heart and brain. To understand the biologic basis of A1AR expression, a genomic fragment containing the murine A1AR promoter was cloned. Reporter assay studies using DDT1 MF2 cells that express A1ARs revealed that 500 base pairs of the proximal A1AR promoter contained essential elements for A1AR gene expression. Transgenic mice with A1AR proximal promoter coupled with the beta-galactosidase reporter gene had heavy labeling of the brain and atria, consistent with normal patterns of A1AR expression. Within the proximal A1AR promoter, putative binding sites for cardiac transcription factors GATA and Nkx2.5 were identified. Co-expression studies revealed that GATA-4 and Nkx2.5 could individually drive A1AR promoter activity and act synergistically to activate A1AR expression. These observations suggest that embryonic A1AR expression involves activation of the A1AR promoter by GATA-4 and Nkx2.5.

Hepatocyte nuclear factor-4 controls transcription from a TATA-less human sex hormone-binding globulin gene promoter

Hepatocytes are the major source of sex hormone-binding globulin (SHBG), a glycoprotein that transports sex steroids in the blood and regulates their access to target tissues. The human SHBG proximal promoter was analyzed by DNase I footprinting, and the functional significance of 6 footprinted regions (FP1-FP6) within the proximal promoter was studied in human HepG2 hepatoblastoma cells. Two footprinted regions (FP1 and FP3) contain binding sites for the chicken ovalbumin upstream promoter-transcription factor (COUP-TF) and hepatocyte nuclear factor-4 (HNF-4). In experiments where SHBG promoter-luciferase reporter gene constructs were co-transfected into HepG2 cells with COUP-TF and/or HNF-4 expression vectors, HNF-4 markedly increased transcription, whereas COUP-TF suppressed this probably by displacing HNF-4 from their common FP1-binding site. This COUP-TF/HNF-4-binding site within FP1 includes a TTTAA sequence, located at nucleotides -30/-26 upstream of the transcription start site, which fails to interact with human TFIID, TATA-binding protein in vitro. When this sequence was replaced with an idealized HNF-4-binding site, the transcriptional activity of the promoter increased in HepG2 cells. Taken together, these data imply that an interplay between COUP-TF and HNF-4 at a site within FP1 regulates human SHBG expression and that HNF-4 controls transcription from this TATA-less promoter by somehow substituting for TATA-binding protein in the recruitment of a transcription preinitiation complex.

Characterization of the alpha1B-adrenergic receptor gene promoter region and hypoxia regulatory elements in vascular smooth muscle

We previously demonstrated that alpha1B-adrenergic receptor (AR) gene transcription, mRNA, and functionally coupled receptors increase during 3% O2 exposure in aorta, but not in vena cava smooth muscle cells (SMC). We report here that alpha1BAR mRNA also increases during hypoxia in liver and lung, but not heart and kidney. A single 2.7-kb alpha1BAR mRNA was detected in aorta and vena cava during normoxia and hypoxia. The alpha1BAR 5' flanking region was sequenced to -2,460 (relative to ATG +1). Transient transfection experiments identify the minimal promoter region between -270 and -143 and sequence between -270 and -248 that are required for transcription of the alpha1BAR gene in aorta and vena cava SMC during normoxia and hypoxia. An ATTAAA motif within this sequence specifically binds aorta, vena cava, and DDT1MF-2 nuclear proteins, and transcription primarily initiates downstream of this motif at approximately -160 in aorta SMC. Sequence between -837 and -273 conferred strong hypoxic induction of transcription in aorta, but not in vena cava SMC, whereas the cis-element for the transcription factor, hypoxia-inducible factor 1, conferred hypoxia-induced transcription in both aorta and vena cava SMC. These data identify sequence required for transcription of the alpha1BAR gene in vascular SMC and suggest the atypical TATA-box, ATTAAA, may mediate this transcription. Hypoxia-sensitive regions of the alpha1BAR gene also were identified that may confer the differential hypoxic increase in alpha1BAR gene transcription in aorta, but not in vena cava SMC.