IGF-I Receptor mRNA Research Articles

Effects of IGF1R siRNA on chemosensitivity to gemcitabine in human pancreatic cancer cells

Objective To construct the lentiviral expression vector for RNA interference of insulin like growth factor-1 receptor (IGF1R) gene in human pancreatic cancer cells and to evaluate its effect on chemosensitivity to gemcitabine.Methods Three sequences of RNA interference targeting IGF1R gene were designed, synthesized and cloned into the pFU-GW-RNAi vector. After transfection of 293T cells with lentiviral vector, the lentivirus was produced and the titer of virus was tested. Panc-1 cells were infected with the lentivirus and the expression of IGF1R mRNA in Panc-1 cells was detected by real-time quantitative polymerase chain reaction (PCR). The changes of gemcitabine sensitivity after RNA interference were examined by methyl thiazol tetrazolium (MTT) assay. In vivo nude mice tumorigenicity model was used to determine the effect of RNA interference targeting IGF1R gene combined with or without gemcitabine on growth inhibition of xenograft tumors.Results A recombinant lentiviral vector expressing shRNA against IGF1R gene was obtained. After RNA interference, the median inhibition concentration (IC50) of gemcitabine against Panc-1 cells was reduced from (0.774±0.001) mg/L to (0.330±0.003) mg/L, indicating that the sensitivity to gemcitabine was increased by 2.35 times after interference. In vivo xenograft formation assay resulted in a significant growth-inhibiting effect by IGF1R RNA interference. Furthermore, the RNA interference targeting IGF1R gene enhanced the antiproliferative effect of gemcitabine on nude mice xenografts.Conclusion The sensitivity of Panc-1 cells to gemcitabine could be enhanced by RNA interference targeting IGF1R gene. Key words: Insulin like growth factor-1 receptor; Gemcitabine; Pancreatic carcinoma; Lentivirus

Expression of insulin-like growth factor I receptors at mRNA and protein levels during metamorphosis of Japanese flounder ( Paralichthys olivaceus)

Insulin-like growth factor I (IGF-I) is an important regulator of fish growth and development, and its biological actions are initiated by binding to IGF-I receptor (IGF-IR). Our previous study has revealed that IGF-I could play an important role during metamorphosis of Japanese flounder, Paralichthys olivaceus. The analysis of IGF-IR expression thus helps further elucidate the IGF-I regulation of metamorphic processes. In this study, the spatial–temporal expression of two distinct IGF-IR mRNAs was investigated by real-time RT-PCR. The spatial distribution of two IGF-IR mRNAs in adult tissues is largely overlapped, but they exhibit distinct temporal expression patterns during larval development. A remarkable decrease in IGF-IR-2 mRNA was detected during metamorphosis. In contrast, a significant increase in IGF-IR-1 mRNA was determined from pre-metamorphosis to metamorphic completion. These indicate that they may play different function roles during the flounder metamorphosis. The levels and localization of IGF-IR proteins during larval development were further studied by Western blotting and immunohistochemistry. Immunoreactive IGF-IRs were detected throughout larval development, and the IGF-IR proteins displayed a relatively abundant expression during metamorphosis. Moreover, the IGF-IR proteins appeared in key tissues, such as thickened skin beneath the migrating eye, developing intestine, gills and kidney during metamorphosis. These results further suggest that the IGF-I system may be involved in metamorphic development of Japanese flounder.

Abstract 1104: Insulin-like growth factor-1 is elevated in viscerally obese oesophageal adenocarcinoma patients and expression of its receptor correlates with tumor invasiveness

Abstract The insulin-like growth factor (IGF) pathway and visceral obesity have been independently linked with esophageal cancer development. This study aimed to delineate the differential and interlinked role of visceral obesity and the IGF-1 system in esophageal adenocarcinoma and squamous cell carcinoma (SCC) progression. IGF-1 receptor (IGF-1R) mRNA and protein were examined in esophageal SCC (KYSE410, OE21) and adenocarcinoma (OE19, OE33) cell lines by Western Blotting. Tumor cell proliferation in response to IGF-1 was assessed by BrdU incorporation assay. Circulating levels of IGF-1 were measured in 99 serum samples by ELISA and IGF-1R expression was assessed in 50 resected tumor specimens by immunohistochemistry. Results were related to tumor type, gender and visceral adiposity. Higher IGF-1R mRNA and protein expression were observed in SCC cells, however only adenocarcinoma cell lines showed significantly increased cell proliferation in response to IGF-1 (p<0.01). Significantly higher circulating levels of IGF-1 were detected in patients who had adenocarcinoma (p<0.05) and who were viscerally obese (p<0.05). In resected esophageal adenocarcinoma, IGF-1R expression significantly increased as the tissue progressed along the malignant sequence, with the highest expression observed at the invasive leading edge of the tumor. Uniform IGF-1R expression was observed in SCC tumors. This novel study is the first of its kind to examine both the differential role of the IGF system in esophageal adenocarcinoma and SCC, and also its association with visceral obesity. These data indicate that in esophageal adenocarcinoma, the IGF-1 axis plays a key role in malignant progression and represents a plausible mechanism by which visceral obesity increases esophageal adenocarcinoma risk. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1104. doi:10.1158/1538-7445.AM2011-1104

Expression Profiles of Somatotropic Axis Genes in Lines of Chickens Divergently Selected for 56-Day Body Weight

The objective of this study was to evaluate mRNA expression of somatotropic axis genes in chickens divergently selected for high (HWS) or low (LWS) body weight at 56 days of age. Gene expression was measured on days 16, 18, and 20 of incubation, day of hatch, and days 3, 7, 28, and 56 posthatch. Pituitary growth hormone mRNA raised from prehatch to posthatch, with a similar profile in both lines. Liver growth hormone receptor (GHR) mRNA was high during embryogenesis, declined to low levels at day 3 posthatch, and then increased to day 56. Expression of liver insulin-like growth factor 1 (IGF-1) mRNA increased sharply by day 28 in line HWS and day 56 in line LWS. Pectoralis major muscle GHR mRNA was greater in line LWS than HWS. Muscle IGF-1 mRNA declined during embryogenesis, increased posthatch, and declined after day 7. IGF-1 mRNA was 1,000-fold greater in embryonic muscle than embryonic liver. Muscle IGF-1 receptor mRNA was greater in line LWS than HWS posthatch. These results demonstrate that genetic selection for high or low body weight has altered the expression profiles of somatotropic axis genes in a line-, age-, and tissue-specific manner.

Calcium and osteoprotegerin regulate IGF1R expression to inhibit vascular calcification

Osteoprotegerin (OPG) inhibits vascular calcification in vitro, and OPG(-/-) mice develop vascular calcification. Insulin-like growth factor-1 (IGF1) signalling has been implicated in vascular smooth muscle cell (VSMC) survival; however, the role of IGF1-receptor (IGF1R) expression in calcification is unclear. We sought to determine whether the protective effects of OPG in vascular calcification were mediated by IGF1R. Calcium-induced mineralization of VSMCs was blocked in cells expressing the IGF1R and by treatment with OPG. OPG induced IGF1R mRNA, protein, and transcription optimally at 1 ng/mL. Calcium also positively regulated both OPG and IGF1R, and siRNA targeting of OPG inhibited calcium-inducible IGF1R mRNA. Addition of calcium to VSMCs reduced camptothecin-stimulated apoptosis and increased expression of survival genes Bcl2 and nuclear factor-kappa B without altering levels of proliferation. Calcium's induction of IGF1R and OPG was dose and time dependent but was blunted at higher calcium doses. Calcium- and OPG-inducible IGF1R transcription occurred between -446 and -188 bp of the IGF1R promoter, and inducible-IGF1R expression was blocked by specificity protein-1 (Sp1) silencing studies. Furthermore, elevated IGF1R and OPG protein levels were present in calcified atherosclerotic tissue. We have shown for the first time that IGF1R expression and activity via OPG can modulate VSMC calcification in vitro. We suggest a feedback mechanism: moderate calcium levels increase OPG, which then increases IGF1R to enhance VSMC survival and block calcification induced by calcium. In contrast, high calcium leads to inhibition of IGF1R expression and activity to stimulate VSMC calcification further.

Sorbic acid improves growth performance and regulates insulin-like growth factor system gene expression in swine1

Sorbic acid (SA) is a PUFA with a conjugated double bond. The conjugated fatty acids, including CLA, are multifunctional bioactive fatty acids with the ability to improve growth performance. The effect of SA on pig growth performance was examined to determine its mechanism of action. The ADG, ADFI, and serum IGF-I concentration were examined, as were IGF-I secretion and IGF system gene expression in hepatocytes. Two hundred forty 21-d-old Duroc × Landrace × Yorkshire weaned piglets (6.86 ± 0.02 kg) were randomly divided into 4 groups, each consisting of 3 pens of 20 piglets (10 female and 10 male). The 4 groups of piglets were kept in a temperature-controlled room (26 to 28 °C), and feed and water were provided to the pigs ad libitum. Weanling piglets were fed diets that included 0, 0.5, 2, or 4 g of SA/kg for 42 d. The diet supplemented with 0.5 g/kg of SA improved (P < 0.05) ADG, BW, and G:F, whereas supplementation with all 3 SA doses increased (P < 0.05) ADG and G:F at 21 to 42 d of age. The greatest concentration of plasma triglycerides was observed (P < 0.05) in the 4 g/kg of SA group. The SA increased (0.5 g of SA/kg, P > 0.05; 1 g of SA/kg, P < 0.05; and 2 g of SA/kg, P < 0.05, respectively) plasma total serum protein and globulin concentrations in a dose-dependent manner. It was noted that the smallest SA treatment dose (0.5 g/kg) dramatically increased (P < 0.05) serum IGF-I concentration but decreased (P < 0.05) the concentrations of blood urea N and cortisol. The SA increased (P < 0.05) IGF-I, IGF-II, IGF-I receptor (IGF-IR), and PPARα gene mRNA expression and IGF-I secretion, but not (P > 0.05) IGFBP or PPARγ mRNA expression, in pig primary hepatocytes. These results indicate that SA improves growth performance by regulating IGF system gene expression and hormone secretion.

727 ANTISENSE OLIGONUCLEOTIDE TARGETING INSULIN-LIKE GROWTH FACTOR-1 RECEPTOR ENHANCES PACLITAXEL SENSITIVITY IN A PACLITAXEL- RESISTANT PROSTATE CANCER MODEL

You have accessJournal of UrologyProstate Cancer: Basic Research1 Apr 2011727 ANTISENSE OLIGONUCLEOTIDE TARGETING INSULIN-LIKE GROWTH FACTOR-1 RECEPTOR ENHANCES PACLITAXEL SENSITIVITY IN A PACLITAXEL- RESISTANT PROSTATE CANCER MODEL Junya Furukawa, Hideaki Miyake, Masato Fujisawa, Christopher Wraight, Brett Monia, Martin Gleave, and Michael Cox Junya FurukawaJunya Furukawa Kobe, Japan More articles by this author , Hideaki MiyakeHideaki Miyake Kobe, Japan More articles by this author , Masato FujisawaMasato Fujisawa Kobe, Japan More articles by this author , Christopher WraightChristopher Wraight Victoria, Australia More articles by this author , Brett MoniaBrett Monia Carlsbad, CA More articles by this author , Martin GleaveMartin Gleave Vancouver, Canada More articles by this author , and Michael CoxMichael Cox Vancouver, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1696AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Altered expression of insulin-like growth factor (IGF) axis components have been consistently found in prostate cancer (PCa) and associated with adaptive growth and survival signaling implicated in castrate-resistant disease (CRPC) progression. These activities are mediated by activation of the IGF-I receptor (IGF-IR). While CRPC patients treated with taxanes alone or in combination with estramustine phosphate or predonisone show a survival benefit, development of chemotherapeutic resistance eventually occurs. Therefore novel strategies targeting the molecular basis of androgen deprivation therapy and chemotherapy resistance are required. In this study, we establish paclitaxel-resistant androgen-independent PCa cells (PtxR PC3) and assess the potency and anti-cancer activity of a 2 EMOE-modified antisense oligonucleotide (ASO) targeting human IGF-IR, ATL1101, on PtxR PC3 cells in vitro and in vivo. METHODS PtxR PC3 cells were established by culturing in step-wise increased drug concentrations. IGF-IR mRNA and protein expression in ATL1101- and control oligonucleotides (ODN)-treated PtxR PC3 cells were measured by QT-PCR and immunoblotting. The effect of IGF-1R ASO and paclitaxel combination therapy on PtxR PC3 cell growth and apoptosis in vitro was examined by crystal violet assay and flow cytometry. In vitro combination index (CI) was calculated by Calcusyn® softoware. For in vivo xenograft studies, PtxR PC-3 cells were inoculated s.c. in the flanks of athymic nude mice and tumor volume kinetics were compared for mice treated with paclitaxel injected i.v. and either ATL1101 or control ODN injected i.p. RESULTS The IC50 for paclitaxel in PtxR PC3 was 15-fold higher than that in parental cells. PtxR PC3 also shows cross-resistance to docetaxel and mitoxantrone. We observed dose- and sequence-specific suppression of IGF-IR mRNA and protein expression in ATL1101-treated PtxR PC3 cells in vitro which correlated with decreased proliferation and increased apoptosis of PtxR PC3 cells. Combination of ATL1101 with paclitaxel showed CI values below 1 at the IC50, IC75, suggesting the drug interactions resulted in synergy. Compared to control ODN, ATL1101 significantly suppressed PtxR PC3 tumor growth as a combination therapy with paclitaxel in murine xenografts. CONCLUSIONS This study reports the first preclinical proof-of-principle data that this novel IGF-IR ASO suppresses growth of paclitaxel resistant PC tumors, synergistically enhancing paclitaxel sensitivity in vitro and in vivo. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e292 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Junya Furukawa Kobe, Japan More articles by this author Hideaki Miyake Kobe, Japan More articles by this author Masato Fujisawa Kobe, Japan More articles by this author Christopher Wraight Victoria, Australia More articles by this author Brett Monia Carlsbad, CA More articles by this author Martin Gleave Vancouver, Canada More articles by this author Michael Cox Vancouver, Canada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

741 PROLIFERATION AND GLUCOSE METABOLISM IS INFLUENCED DIFFERENTLY BY THE INSULIN-LIKE-GROWTH-FACTOR (IGF)/INSULIN AXIS IN PROSTATE CANCER & BENIGN PROSTATE CELLS

You have accessJournal of UrologyProstate Cancer: Basic Research1 Apr 2011741 PROLIFERATION AND GLUCOSE METABOLISM IS INFLUENCED DIFFERENTLY BY THE INSULIN-LIKE-GROWTH-FACTOR (IGF)/INSULIN AXIS IN PROSTATE CANCER & BENIGN PROSTATE CELLS Isabel Heidegger, Petra Massoner, and Helmut Klocker Isabel HeideggerIsabel Heidegger Innsbruck, Austria More articles by this author , Petra MassonerPetra Massoner Innsbruck, Austria More articles by this author , and Helmut KlockerHelmut Klocker Innsbruck, Austria More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1710AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Dysregulation and changes in the insulin-like growth factor (IGF) signaling have been related to the pathogenesis and progression of cancer. The IGF1 receptor (IGF1R) is recognized as an attractive target for anticancer therapy (∼65 clinical studies are ongoing). IGF receptors are closely related to insulin receptors (INSRs) and the Metabolic Syndrome represents an important risk factor for prostate cancer (PCa) development and progression. We analyzed the regulation of IGF and insulin receptors upon ligand stimulation and measured the effect on glucose consumption. METHODS mRNA expression levels were analysed using conventional PCR followed by gel electrophoresis(3% Agarose) or by Real Time PCR. Protein levels were determined by Western blot and immunofluorescent staining. Cell proliferation was assessed using 3H-thymidine incorporation assay and cell number counting. Glucose levels were determinated by Gluc Cell Monitoring System™. RESULTS PCa cells (DU 145 and PC3) stimulated by IGF and INS significantly up-regulated both IGF1R and INSR mRNA expression and proteins levels in a reciprocal manner, whereas no change was observed in benign prostate epithelial cells (EP156T, RWPE1). Hence cell proliferation was increased in cancer cell lines upon IGF and INS stimulation, but not in the benign control cell lines. Moreover, we observed that both the IGF1R and the INSR undergo a trans-membrane to nuclear translocation upon growth factor stimulation in cancer cells. Insulin treatment decreased glucose levels in cancer cells, suggesting a negative feedback mechanism. In addition, our experiments show that Actaprid, an insulin analogue commonly used in diabetes therapy, dose dependently increased the IGF1R and INSR levels in PCa cells. CONCLUSIONS This is one of the first projects investigating that both IGF1R and INSR are tightly regulated in prostate cancer. Their expression is influenced by growth factors, culture conditions and reciprocal regulations. Our preliminary data suggest a link between PCa and glucose metabolism. Possibly, for the future glucose measurements in PCa patients may be used as biomarkers for PCa detection or for responsiveness to IGF targeting therapies. In summary, our data provide new insights into the biology of the IGF/INS axis and in the use of IGF1R inhibitors in cancer therapy. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e297-e298 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Isabel Heidegger Innsbruck, Austria More articles by this author Petra Massoner Innsbruck, Austria More articles by this author Helmut Klocker Innsbruck, Austria More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

A steric blocker of translation elongation inhibits IGF‐1R expression and cell transformation

The insulin-like growth factor 1 receptor (IGF-1R) is involved in transformation, survival, mitogenesis and differentiation. It is overexpressed in many tumors and a validated target for anticancer therapy. In cell-free systems, polypyrimidic peptide nucleic acids (PNAs) can form triplex-like structures with messenger RNAs and halt the ribosomal machinery during the translation elongation. A 17-mer PNA that formed a PNA(2):mRNA complex with a purine-rich sequence located in the coding region of IGF-1R mRNA induced the synthesis of a truncated IGF-1R in vitro. This PNA down-regulated expression of the receptor by 70-80% in prostate cancer cells without affecting insulin receptor expression that exhibits high homology with IGF-1R. Inhibition occurs at the translational level, since the IGF-1R mRNA level measured by quantitative RT-PCR was not affected by PNA treatment. In addition, IGF-1R knockdown by PNA led to an attenuation of phosphorylation of downstream signaling pathways, PI3K/AKT and MAPK, involved in survival and mitogenesis and also to a decrease in cell transformation. Of the steric blockers tested, which included phosphorodiamidate morpholino oligomers and locked nucleic acids, PNA was unique in its ability to form triplex structures with mRNA and to arrest translation elongation.

Oestradiol Enhances Plasma Growth Hormone and Insulin‐like Growth Factor‐I Concentrations and Increased the Expression of their Receptors mRNAs in the Liver of Ovariectomized Cows

Many metabolic hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and insulin affect ovarian functions. However, whether ovarian steroid hormones affect metabolic hormones in cattle remains unknown. This study aimed to determine the effect of sex steroids on the plasma profiles of GH, IGF-I and insulin and their receptors in the liver and adipose tissues of dairy cows. Ovariectomized cows (n = 14) were randomly divided into four groups: control group (n = 3) was treated with saline on Day 0; oestradiol (E2) group (n = 3), with saline and 1 mg oestradiol benzoate (EB) on Day 0 and 5, respectively; progesterone (P4) group (n = 4) with two CIDRs (Pfizer Inc., Tokyo, Japan) from Day 0; and E2 + P4 group (n = 4) with two CIDRs on Day 0 that were removed on Day 6 and were immediately injected with 1 mg EB. The animals were euthanized after the experiment, and liver and adipose tissues samples were quantitatively analysed using real-time PCR for the expression of mRNA for the GH (GHR), IGF-I (IGFR-I) and insulin (IR) receptor mRNAs. Oestradiol benzoate significantly increased the number of peaks (p < 0.05), pulse amplitude (p < 0.05) and area under the curve (AUC; p < 0.01) for plasma GH; moreover, it increased plasma IGF-I concentration (p < 0.05), but it had no effect on the plasma insulin profile. P4 significantly decreased the AUC (p < 0.01), compared with the control group, whereas it did not affect the number of peaks and the amplitude of GH pulses. P4 + E2 did not affect the GH pulse profile. E2 increased the mRNA expression of GHR, IGFR-I and IR in the liver (p < 0.05), whereas both P4 and E2 + P4 did not change their expressions. Our results provide evidence that the metabolic and reproductive endocrine axes may regulate each other to ensure optimal reproductive and metabolic function.

Increased insulin-like growth factor-1 receptor mRNA expression predicts poor survival in immunophenotypes of early breast carcinoma

The biology of breast carcinoma shows a great variation, reflected by the recent classification of phenotypes based on DNA microarrays or immunohistochemistry. The aim of this study was to determine the prevalence of insulin-like growth factor-1 receptor (IGF1R) in breast carcinoma subtypes and the impact on the outcome. We studied 197 consecutive breast carcinoma patients in stage I–II treated conservatively. Phenotypes were assessed on the basis of the expressions of ER/PR, HER2, Ki67, p53, Bcl2, CK5/6 and EGFR. Moreover, IGF1R expression (α-subunit and β-phosphorylated/active form) was evaluated by immunohistochemistry, IGF1R mRNA levels by quantitative RT-PCR and IGF1R mutations by direct DNA sequencing. Overall, 40% (78/197) of tumors were luminal A, 24% (48/197) luminal B, 19% (37/197) HER2-positive and 17% (34/197) basal/triple-negative. Luminal A tumors were predominantly of low grade, without necrosis, presenting in older patients as a ≤2-cm unilateral mass (all P≤0.046). α-IGF1R overexpression was observed more frequently in luminal A (49%) cases, followed by luminal B (20%), HER2-positive area under the curve (22%) and basal/triple-negative cases (9%) (P=0.01) with similar results for mRNA levels (53, 24, 13 and 10%, respectively) (P=0.038), but without differences for mutations (P=NS). High IGF1R mRNA correlated with poor patient survival among subtypes (P=0.004) (Kaplan–Meier; log-rank test). For overall survival, only histological grade and IGF1R mRNA emerged as significant predictors (P≤0.034; Cox regression). Increased IGF1R mRNA implies poorer patient prognosis among the different subtypes, and that may be associated with the lack of responsiveness to tamoxifen in cases with a positive hormone receptor status. Our results highlight the biological and clinical relevance of IGF1R in early breast carcinoma subtypes, and provide knowledge to assist in treatment decision.

AKT Inhibition Relieves Feedback Suppression of Receptor Tyrosine Kinase Expression and Activity

Activation of the PI3K-AKT pathway in tumors is modulated by negative feedback, including mTORC1-mediated inhibition of upstream signaling. We now show that AKT inhibition induces the expression and phosphorylation of multiple receptor tyrosine kinases (RTKs). In a wide spectrum of tumor types, inhibition of AKT induces a conserved set of RTKs, including HER3, IGF-1R, and insulin receptor. This is in part due to mTORC1 inhibition and in part secondary to a FOXO-dependent activation of receptor expression. PI3K-AKT inhibitors relieve this feedback and activate RTK signaling; this may attenuate their antitumor activity. Consistent with this model, we find that, in tumors in which AKT suppresses HER3 expression, combined inhibition of AKT and HER kinase activity is more effective than either alone.

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.

Propionibacterium acnes Activates the IGF-1/IGF-1R System in the Epidermis and Induces Keratinocyte Proliferation

Propionibacterium acnes has a major role in the development of acne lesions. IGF-1 stimulates the proliferation of keratinocytes via an activation of the IGF-1 receptor (IGF-1R). Zinc has been proven to work efficiently against inflammatory acne and to modulate the IGF-1 system. Our objectives were to study the modulation of IGF-1 and IGF-1R expression by P. acnes extracts and to determine their modulation by zinc gluconate. In vivo, we analyzed biopsies of acne lesions and healthy skin, and in vitro we used skin explants incubated with two P. acnes extracts--membrane fraction (MF) and cytosolic proteins--with or without zinc. IGF-1 and IGF-1R expression was evaluated using immunohistochemistry, and the IGF-1 production in supernatants was measured by ELISA. Then, IGF-1 and IGF-1R mRNA levels were analyzed using quantitative PCR on normal human epidermal keratinocytes (NHEKs). IGF-1 and IGF-1R were overexpressed in acne lesions. MF increased IGF-1 and IGF-1R expression in the epidermis of explants and was associated with an overexpression of both Ki-67 and filaggrin. Zinc had the effect of downregulating IGF-1 and IGF-1R levels. These observations were confirmed at the mRNA level for IGF-1R in NHEKs. These results demonstrate that P. acnes can induce the formation of comedones by stimulating the IGF/IGF-1R system. Moreover, zinc downregulates this pathway.

Insulin-Like Growth Factor System and Sporadic Malignant Melanoma

Insulin and insulin-like growth factors (IGFs) are important regulators of energy metabolism and growth. Several findings have outlined an important role played by this family of molecules in both tumor maintenance and development. Despite the established contribution of the IGF system in carcinogenesis, little and contrasting data have been reported concerning the intertwined relationships between melanoma and this family of molecules. The present minireview aims to summarize the main topics and evidence concerning this malignant skin cancer, with a focus on the following: i) melanoma and cell proliferation effects induced by the IGF system, ii) in vitro and in vivo experimental data, and iii) targeting studies. Because of consistent findings regarding the role of the IGF-1 receptor in the modulation of IGF-1 activity, possible therapeutic strategies combining the use of antisense oligonucleotides against IGF-1 receptor mRNA could be applied in the future.

Thiazolidinediones Up-regulate Insulin-like Growth Factor-1 Receptor via a Peroxisome Proliferator-activated Receptor γ-Independent Pathway

There is increasing evidence that thiazolidinediones (TZDs), antidiabetic compounds that are synthetic ligands for the peroxisome proliferator-activated receptor γ (PPARγ), have cardiovascular effects through as yet poorly defined mechanisms. We tested the effect of two TZD class drugs, rosiglitazone and pioglitazone, on human aortic smooth muscle cell (SMC) expression of insulin-like growth factor-1 receptor (IGF-1R). Both TZDs dose dependently up-regulated IGF-1R protein levels (rosiglitazone, 10 μmol/liter, 67% increase, n = 4, p < 0.01; pioglitazone, 10 μmol/liter, 41% increase, n = 4, p < 0.01) and increased IGF-1R signaling activity (36% increase in Akt phosphorylation). However, the endogenous PPARγ ligand, 15-deoxy-Δ(12,14)-prostaglandin J(2), dose dependently reduced IGF-1R (10 μmol/liter, 80% decrease, n = 4, p < 0.01), and overexpression of PPARγ using an adenovirus likewise reduced IGF-1R (50% decrease versus SMC infected with control adenovirus), suggesting a PPARγ-independent action of TZDs. All three PPARγ ligands (rosiglitazone, pioglitazone, and 15-deoxy-Δ(12,14)-prostaglandin J(2)), however, did not change IGF-1R mRNA levels, indicating that their effects were posttranscriptional. Use of bicistronic constructs revealed that TZD induction of IGF-1R translation occurred via internal ribosomal entry. To examine the potential physiological relevance of TZD up-regulation of IGF-1R, we determined the effect of rosiglitazone on oxidized LDL (oxLDL)-induced apoptosis. 20 μmol/liter of rosiglitazone reduced oxidized LDL-induced apoptosis by 40% and neutralizing antibody to IGF-1R (αIR3) counteracted this rescue, suggesting the rosiglitazone survival effect was, at least in part, mediated by IGF-1R. In conclusion, TZDs markedly up-regulate SMC IGF-1R expression and signaling, likely via a PPARγ-independent mechanism. This novel action of TZDs may play an important role in their cardiovascular effects.

MicroRNA-7 targets IGF1R (insulin-like growth factor 1 receptor) in tongue squamous cell carcinoma cells

miR-7 (microRNA-7) has been characterized as a tumour suppressor in several human cancers. It targets a number of proto-oncogenes that contribute to cell proliferation and survival. However, the mechanism(s) by which miR-7 suppresses tumorigenesis in TSCC (tongue squamous cell carcinoma) is unknown. The present bioinformatics analysis revealed that IGF1R (insulin-like growth factor 1 receptor) mRNA is a potential target for miR-7. Ectopic transfection of miR-7 led to a significant reduction in IGF1R at both the mRNA and protein levels in TSCC cells. Knockdown of miR-7 in TSCC cells enhanced IGF1R expression. Direct targeting of miR-7 to three candidate binding sequences located in the 3'-untranslated region of IGF1R mRNA was confirmed using luciferase-reporter-gene assays. The miR-7-mediated down-regulation of IGF1R expression attenuated the IGF1 (insulin-like growth factor 1)-induced activation of Akt (protein kinase B) in TSCC cell lines, which in turn resulted in a reduction in cell proliferation and cell-cycle arrest, and an enhanced apoptotic rate. Taken together, the present results demonstrated that miR-7 regulates the IGF1R/Akt signalling pathway by post-transcriptional regulation of IGF1R. Our results indicate that miR-7 plays an important role in TSCC and may serve as a novel therapeutic target for TSCC patients.

High levels of glucose induce apoptosis in cardiomyocyte via epigenetic regulation of the insulin-like growth factor receptor

Diabetic hyperglycemia result in cardiovascular complications, but the mechanisms by which high levels of glucose (HG) cause diabetic cardiomyopathy are not known. We investigate whether HG-induced repression of insulin-like growth factor 1 receptor (IGF-1R) mediated by epigenetic modifications is one potential mechanism. We found that HG resulted in decreased IGF-1 receptor (IGF-1R) mRNA levels, and IGF-1R protein when compared with H9C2 rat cardiomyocyte cells incubated in normal glucose. HG also induced apoptosis of H9C2 cells. The effects of HG on reduced expression of IGF-1R and increased apoptosis were blocked by silencing p53 with small interference RNA but not by non-targeting scrambled siRNA. Moreover, HG negatively regulated IGF-1R promoter activity as determined by ChIP analysis, which was dependent on p53 since siRNA-p53 attenuated the effects of HG on IGF-1R promoter activity. HG also increased the association of p53 with histone deacetylase 1 (HDAC1), and decreased the association of acetylated histone-4 with the IGF-1R promoter. Furthermore, HDAC inhibitor relieved the repression of IGF-1R following HG state. These results suggest that HG-induced repression of IGF-1R is mediated by the association of p53 with the IGF-1R promoter, and by the subsequent enhanced recruitment of chromatin-modifying proteins, such as HDAC1, to the IGF-1R promoter–p53 complex. In conclusion, our data demonstrate that HG decreases expression of IGF-1R and decreases the association of acetylated histone-4 with the IGF-1R promoter. These studies may help delineate the complex pathways regulating diabetic cardiomyopathy, and have implications for the development of novel therapeutic strategies to prevent diabetic cardiomyopathy by epigenetic regulation of IGF-1R.

Dexamethasone administration inhibits skeletal muscle expression of the androgen receptor and IGF‐1 – implications for steroid‐induced myopathy

Glucocorticoids are a well-recognized cause of muscle weakness. The early effects of glucocorticoids on skeletal muscle (SkM) androgen and IGF-1 pathways have not been previously investigated in human subjects. To determine if administration of the potent glucocorticoid dexamethasone down-regulates SkM androgen receptor and the IGF-1 signalling pathway. Twenty-four subjects (12 men and 12 women), including 12 with type 2 diabetes and 12 nondiabetics were enrolled. Venous blood sampling and biopsy of vastus lateralis were performed before and after administration of oral dexamethasone 4 mg/day for 4 days. Changes in plasma testosterone and IGF-1, SkM androgen receptor mRNA, SkM IGF-1mRNA and SkM IGF-1 receptor mRNA by quantitative RT-PCR after dexamethasone. Relative expression of SkM androgen receptor was similar in male (1.63 +/- 0.37) vs. female (1.57 +/- 0.30) subjects, despite the significant difference in plasma testosterone levels. Plasma IGF-1 and SkM expression of IGF-1 and IGF-1 receptor were also similar between males and females. Following dexamethasone, there was a significant down-regulation of SkM androgen receptor (1.60 +/- 0.23 vs. 1.11 +/- 0.16, P < 0.05) and IGF-1 (1.72 +/- 0.29 vs. 1.06 +/- 0.14, P < 0.05) mRNA, but no change in expression of the IGF-1 receptor. Plasma testosterone fell significantly in both sexes (male: 15.0 +/- 1.3 vs. 11.3 +/- 1.2 nmol/l, P < 0.01, female: 1.8 +/- 0.5 vs. 0.5 +/- 0.1 nmol/l, P < 0.05). Exogenous steroid excess results in relative androgen deficiency at two levels, reduced circulating testosterone and SkM androgen receptor mRNA, along with reduced SkM IGF-1 mRNA. These defects may contribute to the development of steroid-induced myopathy.

Seawater and freshwater challenges affect the insulin-like growth factors IGF-I and IGF-II in liver and osmoregulatory organs of the tilapia

Contradictory studies suggest IGF-I in fish liver and gills is involved in osmoregulation, but nothing is known about the kidney and intestine's role nor about IGF-II's role in any organ. Tilapia were transferred from freshwater (FW) to seawater (SW) for 1 week (wk) and retransferred to FW for another week. At 4 h, 1 d, 2 d, 3 d and 1 wk after SW-transfer and FW-retransfer IGF-I, IGF-II and growth hormone receptor (GHR1) mRNA were measured by real-time PCR. Hepatic IGF-I, IGF-II and GHR1 mRNA were downregulated in parallel after SW-transfer, recovered and were again downregulated after FW-retransfer. In gills, IGF-I, IGF-II and GHR1 were upregulated synchronously after SW-transfer and, partially also after FW-retransfer. The renal genes were downregulated after SW-transfer and partially upregulated after FW-retransfer. Persisting upregulation in intestinal IGF-I mRNA occurred after FW-retransfer. Thus, endocrine and auto/paracrine IGF-I and IGF-II seem to be involved in fish osmoregulation in an organ-specific manner.