Insulin-like Growth Factor Binding Protein-3 mRNA Levels Research Articles

Serum IGFBP-1 as a promising diagnostic and prognostic biomarker for colorectal cancer

Our previous study showed that levels of circulating insulin-like growth factor binding protein-1 (IGFBP-1) has potential diagnostic value for early-stage upper gastrointestinal cancers. This study aimed to assess whether serum IGFBP-1 is a potential diagnostic and prognostic biomarker for CRC patients. IGFBP-1 mRNA expression profile data of peripheral blood in colorectal cancer (CRC) patients were downloaded and analyzed from Gene Expression Omnibus database. We detected serum IGFBP-1 in 138 CRC patients and 190 normal controls using enzyme-linked immunosorbent assay. Blood IGFBP-1 mRNA levels were higher in CRC patients than those in normal controls (P = 0.027). In addition, serum IGFBP-1 protein levels in the CRC group were significantly higher than those in normal control group (P < 0.0001). Serum IGFBP-1 demonstrated better diagnostic accuracy for all CRC and early-stage CRC, respectively, when compared with carcinoembryonic antigen (CEA), carbohydrate antigen19-9 (CA 19-9) or the combination of CEA and CA19-9. Furthermore, Cox multivariate analysis revealed that serum IGFBP-1 was an independent prognostic factor for OS (HR = 2.043, P = 0.045). Our study demonstrated that serum IGFBP-1 might be a potential biomarker for the diagnosis and prognosis of CRC. In addition, the nomogram might be helpful to predict the prognosis of CRC.

Dysregulated expression of GATA2 and GATA6 transcription factors in adenomyosis: implications for impaired endometrial receptivity

To study the effect of adenomyosis on the localized expression of the GATA binding proteins 2 and 6 (GATA2 and GATA6) zinc-finger transcription factors that are involved in proliferation of hematopoietic and endocrine cell lineages, cell differentiation, and organogenesis, potentially leading to impaired endometrial implantation. Laboratory based experimental study. Academic hospital and laboratory. Human endometrial stromal cells (HESCs) of reproductive age patients, 18-45 years of age, with adenomyosis were compared with patients with no pathology and leiomyomatous uteri as controls (n = 4 in each group, respectively). Additionally, midsecretory phase endometrial sections were obtained from patients with adenomyosis and control patients with leiomyoma (n = 8 in each group, respectively). GATA2 and GATA6 immunohistochemistry and H-SCORE were performed on the midsecretory phase endometrial sections from adenomyosis and leiomyoma control patients (n = 8 each, respectively). Control and adenomyosis patient HESC cultures were treated with placebo or 10-8 M estradiol (E2), or decidualization media (EMC) containing 10-8 M E2, 10-7 M medroxyprogesterone acetate, and 5 × 10-5 M cAMP for 6 and 10 days. Additionally, control HESC cultures (n = 4) were transfected with scrambled small interfering RNA (siRNA) (control) or GATA2-specific siRNAs for 6 days while adenomyosis HESC cultures (n = 4) were transfected with human GATA2 expression vectors to silence or induce GATA2 overexpression. Immunohistochemistry was performed to obtain GATA2 and GATA6 H-SCORES in adenomyosis vs. control patient endometrial tissue. Expression of GATA2, GATA6, insulin-like growth factor-binding protein 1 (IGFBP1), prolactin (PRL), progesterone receptor (PGR), estrogen receptor 1 (ESR1), leukemia inhibitory factor (LIF), and Interleukin receptor 11 (IL11R) messenger RNA (mRNA) levels were analyzed using by qPCR with normalization to ACTB. Silencing and overexpression experiments also had the corresponding mRNA levels of the above factors analyzed. Western blot analysis was performed on isolated proteins from transfection experiments. Immunohistochemistry revealed an overall fourfold lower GATA2 and fourfold higher GATA6 H-SCORE level in the endometrial stromal cells of patients with adenomyosis vs. controls. Decidual induction with EMC resulted in significantly lower GATA2, PGR, PRL and IGFBP1 mRNA levels in HESC cultures from patients with adenomyosis patient vs. controls. Leukemia inhibitory factor and IL11R mRNA levels were also significantly dysregulated in adenomyosis HESCs compared with controls. . Silencing of GATA2 expression in control HESCs induced an adenomyosis-like state with significant reductions in GATA2, increases in GATA6 and accompanying aberrations in PGR, PRL, ESR1 and LIF levels. Conversely, GATA2 overexpression via vector in adenomyosis HESCs caused partial restoration of the defective decidual response with significant increases in GATA2, PGR, PRL and LIF expression. In-vivo and in-vitro experiment results demonstrate that there is an overall inverse relationship between endometrial GATA2 and GATA6 levels in patients with adenomyosis who have diminished GATA2 levels and concurrently elevated GATA6 levels. Additionally, lower GATA2 and higher GATA6 levels, together with aberrant levels of important receptors and implantation factors, such as ESR1, PGR, IGFBP1, PRL, LIF, and IL11R mRNA in HESCs from patients with adenomyosis or GATA2-silenced control HESCs, support impaired decidualization. These effects were partially restored with GATA2 overexpression in adenomyosis HESCs, demonstrating a potential therapeutic target.

BONE MORPHOGENETIC PROTEIN 2 PROMOTES HUMAN TROPHOBLAST CELL INVASION AND ENDOTHELIAL-LIKE TUBE FORMATION THROUGH ID1-MEDIATED UP-REGULATION OF IGF BINDING PROTEIN-3

Objective: Extravillous cytotrophoblasts (EVTs) invade into the uterine wall and remodel spiral arteries for proper placentation. Insufficient EVTs invasion and poor spiral arterial remodeling are associated with preeclampsia occurrence. Studies from us and others have demonstrated that the transforming growth factor-beta superfamily member bone morphogenetic protein 2 (BMP2) plays important roles in endometrial decidualization and trophoblast cell invasion. However, BMP2 has also been shown to regulate endothelial cell migration and capillary-like tube formation, as has its downstream signaling molecule inhibitor of DNA binding 1 (ID1). Interestingly, insulin-like growth factor binding protein 3 (IGFBP3) also promotes endothelial precursor cell migration and angiogenesis. Moreover, Id1 shows regulatory effect on Igfbp3 expression in rat prostate epithelial cells. However, whether ID1 and IGFBP3 are integrated in BMP2 signaling and involved in the regulation of trophoblast invasive and endovascular differentiation remains unknown. The objective of our study was to examine the effects of BMP2 on ID1 and IGFBP3 expression and their roles in BMP2-regulated human trophoblast invasion and endothelial-like tube formation. Design and method: Primary and immortalized (HTR8/SVneo) cultures of human trophoblast cells were employed as study models. RT-PCR and Western blot assay were used to study mRNA and protein levels. Small interfering RNA (siRNA) was used to check the roles of key molecules. Matrigel-coated transwell assay and endothelial-like tube formation assay were used to examine cell invasiveness and angiogenesis respectively. Results: BMP2 treatment increased ID1 and IGFBP3 mRNA and protein levels in HTR8/SVneo and primary human EVT cells. Intriguingly, ID1 was essential for BMP2-induced IGFBP3 up-regulation in both study models, and BMP2-induced trophoblast invasion was attenuated by knockdown of either ID1 or IGFBP3. In addition, BMP2 significantly increased endothelial-like tube formation and knockdown of ID1 and IGFBP3 reduced basal and BMP2-induced tube formation in HTR8/SVneo cells. Similarly, BMP2 increased placenta growth factor (PlGF) production in HTR8/SVneo cells and these effects were attenuated by knockdown of ID1 or IGFBP3. Conclusions: Our results reveal that BMP2 promotes trophoblast cell invasion and endothelial-like tube formation by ID1-mediated IGFBP3 up-regulation.

The Regulatory Role of Apelin on the Appetite and Growth of Common Carp (Cyprinus Carpio L.).

Simple SummaryFood intake and growth are two interrelated physiological processes. Fish obtain energy from the outside to meet their own growth and development through food intake. Apelin, as a new endocrine factor, plays a wide range of biological roles. Among them, apelin’s role in regulating appetite and growth has attracted the attention of researchers. Based on our investigations, in vitro and in vivo experiments showed that Pyr-apelin-13 could induce significant changes in mRNA levels of appetite-related and growth-related genes, suggesting that Pyr-apelin-13 may regulate the appetite and growth of common carp by regulating the expression of these key genes.Apelin, a kind of active polypeptide, has many biological functions, such as promoting food intake, enhancing immunity, and regulating energy balance. In mammals, studies have indicated that apelin is involved in regulating food intake. However, there are relatively few studies about the regulatory effect of apelin on fish feeding, and the specific mechanism is not clear. Therefore, the purpose of this study was to preliminarily investigate the regulatory effects of apelin on key genes of feeding and growth in common carp (Cyprinus Carpio L.) through in vitro and in vivo experiments. In the present study, after incubation with different concentrations of Pyr-apelin-13 (0, 10, 100, and 1000 nM) in hypothalamic fragments, the expressions of Neuropeptide Y (NPY) and Agouti related peptide (AgRP) mRNA were significantly up-regulated at 12 and 3 h, respectively, and the significant down-regulation of Cocaine and amphetamine-related transcript (CART) mRNA expression was observed at 1 and 3 h. In vivo, after Pyr-apelin-13 oral administration (0, 1, 10, and 100 pmol/g), the orexin mRNA level in the hypothalamus of common carp was significantly increased at 1, 6, and 12 h, while CART/(Proopiomelanocortin) POMC mRNA levels in the hypothalamus of common carp were significantly down-regulated. Following incubation with different concentrations of Pyr-apelin-13 (0, 10, 100, and 1000 nM) in primary hepatocytes, GHR (Growth hormone receptor), IGF2 (Insulin-like growth factor 2), IGFBP2 (Insulin like growth factor binding protein 2), and IGFBP3 (Insulin like growth factor binding protein 3) mRNA levels were significantly increased at 3 h. In vivo, the levels of IGF1 (Insulin-like growth factor 1), IGF2, IGFBP2 (Insulin like growth factor binding protein 2), and IGFBP3 mRNA were significantly increased after the oral administration of Pyr-apelin-13 in the hepatopancreas, in a time and dose-dependent manner. These results support the hypothesis that Pyr-apelin-13 might regulate the feeding and growth of common carp through mediating the expressions of appetite- and growth-related genes. Overall, apelin, which is an orexigenic peptide, improves food intake and is involved in the growth of common carp.

Bone morphogenetic protein 2 promotes human trophoblast cell invasion and endothelial-like tube formation through ID1-mediated upregulation of IGF binding protein-3.

Extravillous cytotrophoblasts (EVTs) invade into the uterine wall and remodel spiral arteries for proper placentation. Studies from us and others have demonstrated that the transforming growth factor-β superfamily member bone morphogenetic protein 2 (BMP2) plays important roles in endometrial decidualization and trophoblast cell invasion. However, BMP2 has also been shown to regulate endothelial cell migration and capillary-like tube formation, as has its downstream signaling molecule inhibitor of DNA binding 1 (ID1). Interestingly, insulin-like growth factor binding protein 3 (IGFBP3) also promotes cell migration and angiogenesis in endothelial precursor cell. Moreover, Id1 has a regulatory effect on Igfbp3 expression in rat prostate epithelial cells. However, whether ID1 and IGFBP3 are integrated in BMP2 signaling and involved in the regulation of trophoblast invasive and endovascular differentiation remains unknown. The objective of our study was to examine the effects of BMP2 on ID1 and IGFBP3 expression and their roles in BMP2-regulated human trophoblast invasion and endothelial-like tube formation. Primary and immortalized (HTR8/SVneo) cultures of human trophoblast cells were employed as study models. BMP2 treatment increased ID1 and IGFBP3 mRNA and protein levels in HTR8/SVneo and primary human EVT cells. Intriguingly, ID1 was essential for BMP2-induced IGFBP3 upregulation in both study models, and BMP2-induced trophoblast invasion was attenuated by knockdown of either ID1 or IGFBP3. In addition, BMP2 significantly increased endothelial-like tube formation and knockdown of ID1 and IGFBP3 reduced basal and BMP2-induced tube formation in HTR8/SVneo cells. Similarly, BMP2 increased placenta growth factor (PlGF) production in HTR8/SVneo cells and these effects were attenuated by knockdown of ID1 or IGFBP3. Our results reveal that BMP2 promotes trophoblast cell invasion and endothelial-like tube formation by ID1-mediated IGFBP3 upregulation.

Effects of insulin-like growth factor binding protein 3 on cell growth and tumorigenesis in oral squamous cell carcinoma

Background: This study was performed to investigate the effect of insulin-like growth factor binding protein 3 (IGFBP3) on the biological behavior of tumor cells and tumorigenesis of oral squamous cell carcinoma (OSCC). Methods: OSCC HB96, CAL27, and Tca8113 cells were transfected with the following plasmids: siRNA-IGFBP3, pcDNA-0-IGFBP3, or siRNA-NC (negative control). The effect of aberrant IGFBP3 on cell viability, apoptosis, and colony formation was assessed. Quantitative real-time PCR (qRT-PCR) and western blot analysis were used to measure IGFBP3 mRNA and protein levels, respectively. HB96 and CAL27 cells were transfected with IGFBP3-expressing lentiviral plasmids and then transplanted into nude mice to monitor xenograft tumor formation. Results: An optimal transfection efficiency was obtained with 50 pmol siRNA-IGFBP3. Transient silencing of IGFBP3 significantly reduced cell viability, and increased apoptosis in comparison with the non-targeting negative control (NC). Overexpressing IGFBP3 promoted cell viability. Additionally, in comparison with the NC group, both cell growth and colony formation were reduced, while apoptosis was elevated in stably transfected cells. Moreover, silencing IGFBP3 inhibited cell viability and tumor formation in nude mice after 3 weeks, and colony formation, diminished tumorigenesis in nude mice, but promoted cell apoptosis in OSCC cells. Conclusions: Collectively, our study revealed a protumorigenic role for IGFBP3 in OSCC cancer cells, and demonstrated a potential mechanism for the dysregulation of IGFBP3 in cell growth. Therefore, IGFBP3 may be a potential therapeutic target for the treatment of OSCC.

Effects of insulin-like growth factor binding protein 3 on cell growth and tumorigenesis in oral squamous cell carcinoma.

BackgroundThis study was performed to investigate the effect of insulin-like growth factor binding protein 3 (IGFBP3) on the biological behavior of tumor cells and tumorigenesis of oral squamous cell carcinoma (OSCC).MethodsOSCC HB96, CAL27, and Tca8113 cells were transfected with the following plasmids: siRNA-IGFBP3, pcDNA-0-IGFBP3, or siRNA-NC (negative control). The effect of aberrant IGFBP3 on cell viability, apoptosis, and colony formation was assessed. Quantitative real-time PCR (qRT-PCR) and western blot analysis were used to measure IGFBP3 mRNA and protein levels, respectively. HB96 and CAL27 cells were transfected with IGFBP3-expressing lentiviral plasmids and then transplanted into nude mice to monitor xenograft tumor formation.ResultsAn optimal transfection efficiency was obtained with 50 pmol siRNA-IGFBP3. Transient silencing of IGFBP3 significantly reduced cell viability, and increased apoptosis in comparison with the non-targeting negative control (NC). Overexpressing IGFBP3 promoted cell viability. Additionally, in comparison with the NC group, both cell growth and colony formation were reduced, while apoptosis was elevated in stably transfected cells. Moreover, silencing IGFBP3 inhibited cell viability and tumor formation in nude mice after 3 weeks, and colony formation, diminished tumorigenesis in nude mice, but promoted cell apoptosis in OSCC cells.ConclusionsCollectively, our study revealed a protumorigenic role for IGFBP3 in OSCC cancer cells, and demonstrated a potential mechanism for the dysregulation of IGFBP3 in cell growth. Therefore, IGFBP3 may be a potential therapeutic target for the treatment of OSCC.

A single systemic injection of AAV9-hIGFBP2 prevents left ventricular hypertrophy and dysfunction in metabolic syndrome

Metabolic syndrome (MetS) is a known risk factor for cardiovascular events. It is characterized by central obesity plus any two of dyslipidemia, insulin resistance, and hypertension. Obese and diabetic patients with MetS have low plasma insulin-like growth factor binding protein 2 (IGFBP2). Our first aim was to investigate IGFBP2 cardiac expression in MetS patients and in a mice model of MetS. The second aim was to assess if gene therapy with adeno-associated virus 9 carrying human IGFBP2 (AAV9-hIGFBP2) could reduce MetS associated left ventricular hypertrophy in mice. We measured plasma IGFBP2 by ELISA and cardiac mRNA IGFBP2 expression in MetS patients by RT-qPCR. Both plasma levels and heart expression of IGFBP2 were decreased in patients with MetS vs. control patients. Further, in a C57BL/6J mouse model of diet-induced MetS, found similar left ventricular mRNA IGFBP2 expression. Finally, we demonstrated for the first time that in MetS mice with decreased cardiac IGFBP2 mRNA levels, human IGFBP2 can be induced by a single AAV9-hIGFBP2 injection, and that the increased IGFBP2 prevents left ventricle wall thickening, hypertrophy and dysfunction. Human plasma and cardiac IGFBP2 are decreased in MetS patients. In mice, restoration of cardiac IGFBP2 expression level prevents MetS associated left ventricular dysfunction and hypertrophy. These clinical and animal data suggest that IGFBP2 is a new cardiac marker and therapeutic target in MetS to prevent heart remodeling consistent with heart failure.

TXNDC5 contributes to rheumatoid arthritis by down-regulating IGFBP1 expression.

The thioredoxin domain-containing 5 (TXNDC5) gene is associated with susceptibility to rheumatoid arthritis (RA) and exhibits increased expression in the synovial tissues. TXNDC5 is also associated strongly with diabetes, a metabolic disease characterized by interrupted insulin signalling. This study investigated whether TXNDC5 contributes to RA via the insulin signalling pathway. In this study, RA synovial fibroblast-like cells (RASFs) transfected with an anti-TXNDC5 small interfering RNA (siRNA) were analysed with an insulin signaling pathway RT2 profiler polymerase chain reaction (PCR) array and an insulin resistance RT2 profiler PCR array. The PCR arrays detected significantly increased expression of insulin-like growth factor binding protein 1 (IGFBP1) in RASFs with suppressed TXNDC5 expression. The result was verified using real-time PCR and Western blot analyses. Significantly elevated IGFBP1 expression and decreased interleukin (IL)-6 secretion were also detected in culture medium of transfected RASFs. Furthermore, decreased IGFBP1 mRNA and protein expression levels were detected in RA synovial tissues. Additionally, significantly increased apoptosis and decreased cell proliferation and cell migration were observed in RASFs transfected with the anti-TXNDC5 siRNA, whereas transfection with the anti-IGFBP1 siRNA or a mixture of the anti-IGFBP1 and anti-TXNDC5 siRNAs restored normal cell proliferation, migration and IL-6 level in RASFs. Insulin-like growth factor (IGF) has potent prosurvival and anti-apoptotic functions, and IGFBP1 can suppress IGF activity. Based on the results of the present study, we suggest that TXNDC5 contributes to abnormal RASF proliferation, migration and IL-6 production by inhibiting IGFBP1 expression.

Icaritin inhibits decidualization of endometrial stromal cells.

The aim of the present study was to investigate the effects of Icaritin on the proliferation and decidualization of endometrial stromal cells (ESCs). A total of 20 specimens of endometrium were collected during hysterectomy at the Gynecology Department of Shenzhen Nanshan People's Hospital (Shenzhen, China) between August 2014 and December 2015. The endometrium was digested with high concentrations of collagenase and DNase and filtered with meshes, and then the glandular epithelial and stromal cells were separated by the adhesion purification method. The purity of stromal cells was identified by vimetin and cytokeratin 7 immunostaining. The estradiol + progesterone (E2+P4) and/or cyclic adenosine monophosphate (cAMP) were added to induce an in vitro decidualization model, which was used to analyze the effect of Icaritin on the decidualization ability of the human ESCs. The decidualization markers of human ESCs, prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP-1), was analyzed by reverse-transcription quantitative polymerase chain reaction measurements of the mRNA levels, PRL immunostaining and ELISA analysis of the IGFBP-1 protein levels in the cells or cell culture supernatant separately. The results demonstrated that treatment with E2+P4 and/or cAMP for 96 h was able to induce decidualization in ESCs, and that the cells demonstrated polygon-shaped epithelioid changes. The cell nuclei revealed multinuclear changes, and the cells were also observed to be large and round in shape. The PRL expression and upregulated IGFBP-1 mRNA and protein levels in the E2+P4+cAMP treatment group indicated successful decidualization of the in vitro model. However, the addition of Icaritin inhibited the expression of PRL and IGFBP-1 mRNA, as well as IGFBP-1 protein in the induced ESCs compared with groups without Icaritin. These results suggest that Icaritin was able to inhibit the expression of decidualization-related genes in ESCs in vitro. However, the exact mechanisms require further investigation.

Direct regulation of IGF-binding protein 1 promoter by interleukin-1β via an insulin- and FoxO-1-independent mechanism.

The level of insulin-like growth factor-binding protein 1 (IGFBP1), a liver-produced serum protein that regulates insulin-like growth factor-I bioactivity, glucose homeostasis, and tissue regeneration, increases during inflammation. This manuscript describes a novel pathway for the regulation of hepatic IGFBP1 mRNA and protein levels by interleukin (IL)-1β. Experiments with the luciferase reporter system show that IL-1β stimulates transcriptional activity from the 1-kb promoter region of IGFBP1. Although IL-1β stimulation suppresses the insulin activation of protein kinase B, the major upstream regulator of IGFBP1 mRNA transcription, the induction of IGFBP1 by IL-1β did not require an intact insulin response element. Furthermore, neither overexpression nor silencing of FoxO-1 had any effect on the IL-1β-induced increase in IGFBP1 mRNA levels and promoter activity. However, inhibition of the ERK MAP kinases effectively prevented the IL-1β effects. Inhibition of neutral sphingomyelinase, a key player in the IL-1β signaling cascade that acts upstream of ERK, also suppressed the IL-1β effects, while increasing the ceramide, through the addition of C2-ceramide or via treatment with exogenous sphingomyelinase, was sufficient to induce IGFBP1 promoter-driven luciferase activity. Studies in primary rat hepatocytes where the levels of neutral sphingomyelinase were either elevated or suppressed using adenoviral constructs affirmed the key role of neutral sphingomyelinase and ceramide (exerted likely through ERK activation) in the IL-1β-induced IGFBP1 production. Finally, the IL-1β effects on IGFBP1 mRNA production and protein secretion could be abolished by the addition of insulin, either at very late time points or at very high doses.

Notch2 controls prolactin and insulin-like growth factor binding protein-1 expression in decidualizing human stromal cells of early pregnancy.

Decidualization, the transformation of the human uterine mucosa into the endometrium of pregnancy, is critical for successful implantation and embryonic development. However, key regulatory factors controlling differentiation of uterine stromal cells into hormone-secreting decidual cells have not been fully elucidated. Hence, we herein investigated the role of the Notch signaling pathway in human decidual stromal cells (HDSC) isolated from early pregnancy samples. Immunofluorescence of first trimester decidual tissues revealed expression of Notch2 receptor and its putative, membrane-anchored interaction partners Jagged1, Delta-like (DLL) 1 and DLL4 in stromal cells whereas other Notch receptors and ligands were absent from these cells. During in vitro differentiation with estrogen/progesterone (E2P4) and/or cyclic adenosine monophosphate (cAMP) HDSC constitutively expressed Notch2 and weakly downregulated Jagged1 mRNA and protein, measured by quantitative PCR (qPCR) and Western blotting, respectively. However, increased levels of DLL1 and DLL4 were observed in the decidualizing cultures. Transfection of a Notch luciferase reporter and qPCR of the Notch target gene hairy and enhancer of split 1 (HES1) revealed an induction of canonical Notch activity during in vitro differentiation. In contrast, treatment of HDSC with a chemical Notch/γ-secretase inhibitor decreased cAMP/E2P4-stimulated Notch luciferase activity, HES1 transcript levels and mRNA expression of the decidual marker genes prolactin (PRL) and insulin-like growth factor binding protein 1 (IGFBP1). Similarly, siRNA-mediated gene silencing or antibody-mediated blocking of Notch2 diminished HES1, PRL and IGFBP1 mRNA levels as well as secreted PRL protein. In summary, the data suggest that canonical, Notch2-dependent signaling plays a role in human decidualization.

Transcriptional and posttranslational regulation of insulin-like growth factor binding protein-3 by Akt3.

Insulin-like growth factor (IGF)-dependent and -independent antitumor activities of insulin-like growth factor binding protein-3 (IGFBP-3) have been proposed in human non-small cell lung cancer (NSCLC) cells. However, the mechanism underlying regulation of IGFBP-3 expression in NSCLC cells is not well understood. In this study, we show that activation of Akt, especially Akt3, plays a major role in the mRNA expression and protein stability of IGFBP-3 and thus antitumor activities of IGFBP-3 in NSCLC cells. When Akt was activated by genomic or pharmacologic approaches, IGFBP-3 transcription and protein stability were decreased. Conversely, suppression of Akt increased IGFBP-3 mRNA levels and protein stability in NSCLC cell lines. Characterization of the effects of constitutively active form of each Akt subtype (HA-Akt-DD) on IGFBP-3 expression in NSCLC cells and a xenograft model indicated that Akt3 plays a major role in the Akt-mediated regulation of IGFBP-3 expression and thus suppression of Akt effectively enhances the antitumor activities of IGFBP-3 in NSCLC cells with Akt3 overactivation. Collectively, these data suggest a novel function of Akt3 as a negative regulator of IGFBP-3, indicating the possible benefit of a combined inhibition of IGFBP-3 and Akt3 for the treatment of patients with NSCLC.

Molecular characterization and expression pattern of insulin-like growth factor binding protein-3 (IGFBP-3) in common carp, Cyprinus carpio

A full-length cDNA encoding the insulin-like growth factor binding protein-3 (IGFBP-3) was cloned from the liver of common carp (Cyprinus carpio) by RT-PCR. The IGFBP-3 cDNA sequence is 1,680 bp long and has an open reading frame of 882 bp encoding a predicted polypeptide of 293 amino acid residues. The deduced amino acid sequence contains a putative signal peptide of 25 amino acid residues resulting in a mature protein of 268 amino acids. A single band of approximate 1.9 kb was found in liver by Northern blot analysis. IGFBP-3 mRNA was observed in all regions of brain with high levels. In peripheral tissues, high levels of IGFBP-3 mRNA were found in retina, red muscle, liver, heart, posterior intestine, spleen, and testis. Relatively lower levels were found in white muscle, kidney, thymus gland, and ovary, while in head kidney, blood, skin, gill, middle intestine, and anterior intestine, the IGFBP-3 mRNA levels were much lower. IGFBP-3 mRNA was first detected in the blastula stage with significantly high level. The level sharply decreased in gastrula stage, and it became to increase in the following stages. During the reproductive cycle, the abundance of IGFBP-3 mRNA significantly decreased between the recrudescing stage and the matured stage in ovary, although in testis, IGFBP-3 mRNA expression level did not exhibit a significant change. The mRNA expression profiles in the present study imply that the IGFBP-3 may play important physiological functions in common carp development and reproduction.

Insulin stimulates IGFBP-2 expression in 3T3-L1 adipocytes through the PI3K/mTOR pathway

Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the etiology of several diseases, including the metabolic syndrome. Although IGFBP-2 derives mostly from the liver, recent evidence in mice and humans indicate that aging and obesity are associated with altered IGFBP-2 levels in white adipocytes. The present study was aimed at determining the mechanisms that control IGFBP-2 expression in mature adipocytes. IGFBP-2 mRNA and protein expression in serum-deprived 3T3-L1 adipocytes were twofold increased by acute insulin treatment. Co-treatments with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the mammalian target of rapamycin (mTOR) inhibitor rapamycin blunted the effects of insulin. Coherently, IGFBP-2 mRNA levels were robustly increased in adipocytes lacking either TSC2 or 4E-BP1. Insulin triggered the recruitment of CAAT/enhancer binding protein α (C/EBPα) to the IGFBP-2 proximal promoter. These findings suggest that insulin upregulates IGFBP-2 expression through a PI3K/mTOR/C/EBPα pathway in white adipocytes.

Abstract P253: Transcriptional Regulation of the IGFBP-1 Gene by RTEF-1 in Endothelial Cells

Background and Objective: Cardiovascular disease is the most important complication of type 2 diabetes, however, its underlying mechanism(s) are poorly understood. Our lab previously reported that RTEF-1 is a transcription factor that promotes angiogenesis via up-regulating HIF-1α and VEGF. In addition to these studies, we recently determined that RTEF-1 upregulates insulin-like growth factor binding protein-1 (IGFBP-1) expression in endothelial cells in vitro and in vivo. IGFBPs are key regulators of insulin-like growth factor (IGF) type 1 and 2 bioavailability at the cellular level. In addition, IGFBP-1 is implicated in cardiovascular health, in terms of blood pressure and glucose tolerance. Methods and Results: RTEF-1 upregulates IGFBP-1 expression in endothelial cells in vitro and in vivo through selectively binding and promoting transcription from the insulin response element (IRE) site on the IGFBP-1 promoter, demonstrated by ChIP assays. In addition to insulin inhibition of IGFBP-1 levels, insulin also dose-dependently inhibits RTEF-1 promoter activity (-2.4 ± 0.3-fold) and expression. In vivo data suggest that Tie2-Cre:RTEF-1 flox/flox transgenic mice, RTEF-1 EC-specific knockout mice, show a significant decrease decrease in IGFBP-1 mRNA levels compared with controls (0.21 ± 0.09 vs. 1.0, respectively), while VE-Cadherin/RTEF-1 overexpressing transgenic mice have increased IGFBP-1 mRNA levels (25.4 ± 0.02-fold). Increased IGFBP-1 levels relate physiologically in our RTEF-1 EC-specific knockout by showing decreased blood glucose tolerance as well as increased insulin resistance as calculated by HOMA-IR compared with littermate controls, (4.1 ± 0.5 vs. 1.1 ± 0.2, respectively). Furthermore, the RTEF-1 EC-specific knockout mice showed a significant increase in systolic blood pressure (10mmHg ± 6mmHg) compared with littermate controls. Conclusion: These results demonstrate that RTEF-1-stimulated IGFBP-1 expression may be central to the mechanism by which RTEF-1 attenuates blood glucose levels and potential cardiovascular function. These findings provide the basis for novel insights into transcriptional regulation of IGFBP-1 and contribute to understanding the role of vascular endothelial cells in metabolism.

Oncogenic Fusion Protein EWS/FLI1 Down-regulates Gene Expression by Both Transcriptional and Posttranscriptional Mechanisms

Ewing family tumors are characterized by a translocation between the RNA binding protein EWS and one of five ETS transcription factors, most commonly FLI1. The fusion protein produced by the translocation has been thought to act as an aberrant transcription factor, leading to changes in gene expression and cellular transformation. In this study, we investigated the specific processes EWS/FLI1 utilizes to alter gene expression. Using both heterologous NIH 3T3 and human Ewing Family Tumor cell lines, we have demonstrated by quantitative pre-mRNA analysis that EWS/FLI1 repressed the expression of previously validated direct target genes at the level of transcript synthesis. ChIP experiments showed that EWS/FLI1 decreases the amount of Pol II at the promoter of down-regulated genes in both murine and human model systems. However, in down-regulated target genes, there was a significant disparity between the modulation of cognate mRNA and pre-mRNAs, suggesting that these genes could also be regulated at a posttranscriptional level. Confirming this, we found that EWS/FLI1 decreased the transcript half-life of insulin-like growth factor binding protein 3, a down-regulated direct target gene in human tumor-derived Ewing's sarcoma cell lines. Additionally, we have shown through reexpression experiments that full EWS/FLI1-mediated transcriptional repression requires intact EWS and ETS domains. Together these data demonstrate that EWS/FLI1 can dictate steady-state target gene expression by modulating both transcript synthesis and degradation.

Loss of the pregnancy-induced rise in cortisol concentrations in the ewe impairs the fetal insulin-like growth factor axis

Maternal cortisol levels increase during pregnancy. Although this change is important for optimal fetal growth, the mechanisms of the changes in growth remain unclear. The hypothesis examined was that alterations in maternal plasma cortisol concentrations are associated with changes in the fetal insulin-like growth factor (IGF) axis. Pregnant ewes in late gestation (115 ± 0.4 days) were studied: six control animals, five ewes given 1 mg kg(-1) day(-1) cortisol (high cortisol) and five adrenalectomised ewes given 0.5-0.6 mg kg(-1) day(-1) cortisol (low cortisol). Blood samples were taken throughout the experiment and at necropsy (130 ± 0.2 days) and fetal liver was frozen for mRNA analysis. Fetal IGF-I and insulin plasma concentrations were lower and insulin-like growth factor-binding protein-1 (IGFBP-1) concentrations were higher in the low cortisol group compared with those in the control group (P < 0.05). Fetal liver IGF-II and IGFBP-3 mRNA were decreased in low cortisol animals compared with controls (P < 0.05). There were no significant changes in these parameters in the high cortisol group, and there were no changes in fetal liver IGF-I, growth hormone receptor, IGF-I receptor, IGF-II receptor, IGFBP-1 or IGFBP-2 mRNA levels between the groups. These data suggest that reduced fetal IGF availability contributes to reduced fetal growth when maternal cortisol secretion is impaired, but not during exposure to moderate increases in cortisol.

Modulation of IGFBP2 mRNA Expression in White Adipose Tissue upon Aging and Obesity

The insulin/IGF-1 signaling pathway is a determinant of aging and age-related diseases. IGF-binding protein 2 (IGFBP2) is secreted by white adipocytes and contributes to the prevention of diet-induced obesity and age-related insulin resistance in mice. However, the expression levels of IGFBP2 in insulin resistance disorders have not been evaluated. The present study was aimed at determining IGFBP2 mRNA levels in adipose tissue in conditions of insulin resistance such as aging and obesity. In visceral white adipose tissue (WAT), but not in subcutaneous WAT, IGFBP2 mRNA levels were significantly lower in obese OB/OB, DB/DB and high fat-fed mice compared with those of their respective lean and chow-fed littermates. IGFBP2 mRNA levels were also decreased in visceral WAT of 12 and 24 months old mice compared with those of their 4 months old counterparts. Visceral WAT IGFBP2 expression was significantly associated with IGFBP2 circulating levels in mice, suggesting an important contribution from this tissue. The negative effect of aging on IGFBP2 mRNA levels in visceral WAT was confirmed in obese men. These findings demonstrate that the transcription of the IGFBP2 gene is modulated in a depot-specific fashion in obesity and aging in mice and men. Because IGFBP2 is an adipokine, an altered production from visceral WAT depots could impact on IGF-1 signaling and its downstream targets. This supports the need for further molecular and clinical studies to determine the factors regulating IGFBP2 expression and its relevance to metabolic diseases.

IGFBP-2 expression in MCF-7 cells is regulated by the PI3K/AKT/mTOR pathway through Sp1-induced increase in transcription

Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the pathophysiology of neoplasia. The PI3K/AKT/mTOR pathway has recently been shown to be a predominant regulator of IGFBP-2 at the protein level in MCF-7 breast cancer cells. However, there are gaps in knowledge with respect to the molecular mechanisms that underlie this regulation. Here, we show that the PI3K/AKT/mTOR pathway regulates IGFBP-2 protein levels by modulating IGFBP-2 mRNA abundance in MCF-7 cells. This change is achieved by regulating transcription through a critical region present in the first 200 bp upstream of the transcription initiation site where Sp1 transcription factor binds and drives transcription. IGF-1 treatment leads to increased nuclear abundance of Sp1 and increased IGFBP-2 mRNA and protein levels. Rapamycin and LY294002 induce a decline in Sp1 nuclear abundance and IGFBP-2 mRNA and protein levels. This work provides a mechanistic explanation for the observed effects of the PI3K/AKT/mTOR pathway on IGFBP-2 levels in MCF-7 cells.