The role and regulation of IGFBP-1 phosphorylation in fetal growth restriction. J Cell Commun Signal. 2015;9:111-123. [PMID: 25682045 DOI: 10.1007/s12079-015-0266-x]

Expression of the IGF‑1Ea isoform in human placentas from third trimester normal and idiopathic intrauterine growth restriction singleton pregnancies: Correlations with clinical and histopathological parameters

Intrauterine growth restriction (IUGR) is the second most common obstetric complication after preterm labor. Appropriate trophoblast differentiation and placental structure, growth and function are key for the maintenance of pregnancy and normal fetal growth, development and survival. Extravillous trophoblast cell proliferation, migration and invasion are regulated by molecules produced by the fetomaternal interface, including autocrine factors produced by the trophoblast, such as insulin‑like growth factor (IGF)‑1. The aim of the present study was to investigate expression patterns of IGF‑1Ea isoform in IUGR placenta compared with appropriate for gestational age (AGA) pregnancies. Placental frozen tissues were collected from 13 AGA and 15 IUGR third trimester pregnancies for detection of IGF‑1Ea mRNA expression using reverse transcription‑quantitative PCR. Formalin‑fixed paraffin‑embedded samples from 15 AGA and 47 IUGR pregnancies were analyzed immunohistochemically for the identification and localization of the IGF‑1Ea peptide and comparison of clinical and histopathological parameters. To the best of our knowledge, the present study is the first to show IGF‑1Ea expression in third trimester human placenta. The results indicated that similar IGF‑1Ea mRNA expression levels were present in placental specimens from both groups. Cytoplasmic IGF‑1Ea expression was localized in the perivillous syncytiotrophoblast, extravillous trophoblast and endothelium of the villous and decidual vessels in both groups. No significant difference in the scores and intensity of IGF‑1Ea expression in perivillous syncytiotrophoblasts were noted in the IUGR vs. AGA pregnancies. Most IUGR cases showed negative IGF‑1Ea expression in the extravillous trophoblast, whereas AGA pregnancies showed predominantly positive immunostaining. A sex‑specific expression pattern was noted in the extravillous trophoblast, with negative IGF‑1Ea expression in the placentas of female IUGR cases. Additionally, positive immunostaining for IGF‑1Ea peptide in fetal villous and maternal decidual vessels, was more frequently observed in the IUGR group compared with AGA. In conclusion, no difference in total IGF‑1Ea mRNA placental expression was observed between IUGR and AGA pregnancies, likely due to heterogeneity of histological structures expressing this isoform. Negative IGF‑1Ea immunohistological expression in the extravillous trophoblast from IUGR placentas, associated with histological changes of maternal malperfusion, may reflect the involvement of this isoform in defective placentation. The presence of IGF‑1Ea peptide in the endothelium of the villous vessels in IUGR placentas may indicate a reactive autocrine regulation to compensate for malperfused villi in IUGR pregnancy by regulating angiogenesis and vasodilation. The observed sex differences in IGF‑1Ea expression between IUGR and AGA placentas may indicate interactions between sex hormones and selective IGF‑1 binding proteins in regulating IGF‑1Ea synthesis; however, this requires further elucidation.

Developmentally dynamic changes in DNA methylation in the human pancreas

Development of the human pancreas requires the precise temporal control of gene expression via epigenetic mechanisms and the binding of key transcription factors. We quantified genome-wide patterns of DNA methylation in human fetal pancreatic samples from donors aged 6 to 21 post-conception weeks. We found dramatic changes in DNA methylation across pancreas development, with > 21% of sites characterized as developmental differentially methylated positions (dDMPs) including many annotated to genes associated with monogenic diabetes. An analysis of DNA methylation in postnatal pancreas tissue showed that the dramatic temporal changes in DNA methylation occurring in the developing pancreas are largely limited to the prenatal period. Significant differences in DNA methylation were observed between males and females at a number of autosomal sites, with a small proportion of sites showing sex-specific DNA methylation trajectories across pancreas development. Pancreas dDMPs were not distributed equally across the genome and were depleted in regulatory domains characterized by open chromatin and the binding of known pancreatic development transcription factors. Finally, we compared our pancreas dDMPs to previous findings from the human brain, identifying evidence for tissue-specific developmental changes in DNA methylation. This study represents the first systematic exploration of DNA methylation patterns during human fetal pancreas development and confirms the prenatal period as a time of major epigenomic plasticity.

Unraveling the unfolded protein response signature: implications for tumor immune microenvironment heterogeneity and clinical prognosis in stomach cancer

BACKGROUND

Stomach cancer is a leading cause of cancer-related deaths globally due to its high grade and poor response to treatment. Understanding the molecular network driving the rapid progression of stomach cancer is crucial for improving patient outcomes.

METHODS

This study aimed to investigate the role of unfolded protein response (UPR) related genes in stomach cancer and their potential as prognostic biomarkers. RNA expression data and clinical follow-up information were obtained from the TCGA and GEO databases. An unsupervised clustering algorithm was used to identify UPR genomic subtypes in stomach cancer. Functional enrichment analysis, immune landscape analysis, and chemotherapy benefit prediction were conducted for each subtype. A prognostic model based on UPR-related genes was developed and validated using LASSO-Cox regression, and a multivariate nomogram was created. Key gene expression analyses in pan-cancer and in vitro experiments were performed to further investigate the role of the identified genes in cancer progression.

RESULTS

A total of 375 stomach cancer patients were included in this study. Analysis of 113 UPR-related genes revealed their close functional correlation and significant enrichment in protein modification, transport, and RNA degradation pathways. Unsupervised clustering identified two molecular subtypes with significant differences in prognosis and gene expression profiles. Immune landscape analysis showed that UPR may influence the composition of the tumor immune microenvironment. Chemotherapy sensitivity analysis indicated that patients in the C2 molecular subtype were more responsive to chemotherapy compared to those in the C1 molecular subtype. A prognostic signature consisting of seven UPR-related genes was constructed and validated, and an independent prognostic nomogram was developed. The gene IGFBP1, which had the highest weight coefficient in the prognostic signature, was found to promote the malignant phenotype of stomach cancer cells, suggesting its potential as a therapeutic target.

CONCLUSIONS

The study developed a UPR-related gene classifier and risk signature for predicting survival in stomach cancer, identifying IGFBP1 as a key factor promoting the disease's malignancy and a potential therapeutic target. IGFBP1's role in enhancing cancer cell adaptation to endoplasmic reticulum stress suggests its importance in stomach cancer prognosis and treatment.

AMPK-mTORC1 pathway mediates hepatic IGFBP-1 phosphorylation in glucose deprivation: a potential molecular mechanism of hypoglycemia-induced impaired fetal growth

Mechanisms underlying limitations in glucose supply that restrict fetal growth are not well established. IGF-1 is an important regulator of fetal growth and IGF-1 bioavailability is markedly inhibited by IGFBP-1 especially when the binding protein is hyperphosphorylated. We hypothesized that the AMPK-mTORC1 pathway increases IGFBP-1 phosphorylation in response to glucose deprivation. Glucose deprivation in HepG2 cells activated AMPK and TSC2, inhibited mTORC1 and increased IGFBP-1 secretion and site-specific phosphorylation. Glucose deprivation also decreased IGF-1 bioavailability and IGF-dependent activation of IGF-1R. AICAR (an AMPK activator) activated TSC2, inhibited mTORC1, and increased IGFBP-1 secretion/phosphorylation. Further, siRNA silencing of either AMPK or TSC2 prevented mTORC1 inhibition and IGFBP-1 secretion and phosphorylation in glucose deprivation. Our data suggest that the increase in IGFBP-1 phosphorylation in response to glucose deprivation is mediated by the activation of AMPK/TSC2 and inhibition of mTORC1, providing a possible mechanistic link between glucose deprivation and restricted fetal growth.

Effects of melamine and cyanuric acid on placental and fetal development in rats

Melamine or cyanuric acid alone has low toxicity, but combined exposure to melamine and cyanuric acid was reported to cause unexpected toxicological effects. This study investigated the potential effects and toxic mechanism of combined exposure to melamine and cyanuric acid on placental and fetal development in rats. Exposure to melamine and cyanuric acid caused maternal toxicity manifested by increased abnormal symptoms and decreased body weight gain. Developmental toxic effects included a decrease in placental and fetal weights with increased fetal deaths and post-implantation loss. Melamine and cyanuric acid induced oxidative stress in the developing placenta and fetus. The placentas from rats treated with melamine and cyanuric acid showed shortening of the placental layers with histological changes, decreased cell proliferation, increased apoptotic changes, and decreased insulin-like growth factor (IGF)/IGF-binding proteins (IGFBPs) and placental lactogen (PL) expression levels. Fetuses from melamine- and cyanuric acid-treated dams showed increased apoptotic changes and suppressed cellular proliferation in their livers and vertebrae. Consequently, combined exposure to melamine and cyanuric acid resulted in high levels of oxidative stress and impaired placental development associated with impairment of the IGF/IGFBP and PL systems, resulting in increased apoptotic changes and reduced fetal cell proliferation.

Blood Biomarkers in the Fetally Growth Restricted and Small for Gestational Age Neonate: Associations with Brain Injury

Fetal growth restriction (FGR) and small for gestational age (SGA) infants have increased risk of mortality and morbidity. Although both FGR and SGA infants have low birthweights for gestational age, a diagnosis of FGR also requires assessments of umbilical artery Doppler, physiological determinants, neonatal features of malnutrition, and in utero growth retardation. Both FGR and SGA are associated with adverse neurodevelopmental outcomes ranging from learning and behavioral difficulties to cerebral palsy. Up to 50% of FGR, newborns are not diagnosed until around the time of birth, yet this diagnosis lacks further indication of the risk of brain injury or adverse neurodevelopmental outcomes. Blood biomarkers may be a promising tool. Defining blood biomarkers indicating an infant's risk of brain injury would provide the opportunity for early detection and therefore earlier support. The aim of this review was to summarize the current literature to assist in guiding the future direction for the early detection of adverse brain outcomes in FGR and SGA neonates. The studies investigated potential diagnostic blood biomarkers from cord and neonatal blood or serum from FGR and SGA human neonates. Results were often conflicting with heterogeneity common in the biomarkers examined, timepoints, gestational age, and definitions of FGR and SGA used. Due to these variations, it was difficult to draw strong conclusions from the results. The search for blood biomarkers of brain injury in FGR and SGA neonates should continue as early detection and intervention is critical to improve outcomes for these neonates.

Placental Remote Control of Fetal Metabolism: Trophoblast mTOR Signaling Regulates Liver IGFBP-1 Phosphorylation and IGF-1 Bioavailability

The mechanisms mediating the restricted growth in intrauterine growth restriction (IUGR) remain to be fully established. Mechanistic target of rapamycin (mTOR) signaling functions as a placental nutrient sensor, indirectly influencing fetal growth by regulating placental function. Increased secretion and the phosphorylation of fetal liver IGFBP-1 are known to markedly decrease the bioavailability of IGF-1, a major fetal growth factor. We hypothesized that an inhibition of trophoblast mTOR increases liver IGFBP-1 secretion and phosphorylation. We collected conditioned media (CM) from cultured primary human trophoblast (PHT) cells with a silenced RAPTOR (specific inhibition of mTOR Complex 1), RICTOR (inhibition of mTOR Complex 2), or DEPTOR (activates both mTOR Complexes). Subsequently, HepG2 cells, a well-established model for human fetal hepatocytes, were cultured in CM from PHT cells, and IGFBP-1 secretion and phosphorylation were determined. CM from PHT cells with either mTORC1 or mTORC2 inhibition caused the marked hyperphosphorylation of IGFBP-1 in HepG2 cells as determined by 2D-immunoblotting while Parallel Reaction Monitoring-Mass Spectrometry (PRM-MS) identified increased dually phosphorylated Ser169 + Ser174. Furthermore, using the same samples, PRM-MS identified multiple CK2 peptides coimmunoprecipitated with IGFBP-1 and greater CK2 autophosphorylation, indicating the activation of CK2, a key enzyme mediating IGFBP-1 phosphorylation. Increased IGFBP-1 phosphorylation inhibited IGF-1 function, as determined by the reduced IGF-1R autophosphorylation. Conversely, CM from PHT cells with mTOR activation decreased IGFBP-1 phosphorylation. CM from non-trophoblast cells with mTORC1 or mTORC2 inhibition had no effect on HepG2 IGFBP-1 phosphorylation. Placental mTOR signaling may regulate fetal growth by the remote control of fetal liver IGFBP-1 phosphorylation.

Cell cycle control by the insulin-like growth factor signal: at the crossroad between cell growth and mitotic regulation

In proliferating cells and tissues a number of checkpoints (G1/S and G2/M) preceding cell division (M-phase) require the signal provided by growth factors present in serum. IGFs (I and II) have been demonstrated to constitute key intrinsic components of the peptidic active fraction of mammalian serum. In vivo genetic ablation studies have shown that the cellular signal triggered by the IGFs through their cellular receptors represents a non-replaceable requirement for cell growth and cell cycle progression. Retroactive and current evaluation of published literature sheds light on the intracellular circuitry activated by these factors providing us with a better picture of the pleiotropic mechanistic actions by which IGFs regulate both cell size and mitogenesis under developmental growth as well as in malignant proliferation. The present work aims to summarize the cumulative knowledge learned from the IGF ligands/receptors and their intracellular signaling transducers towards control of cell size and cell-cycle with particular focus to their actionable circuits in human cancer. Furthermore, we bring novel perspectives on key functional discriminants of the IGF growth-mitogenic pathway allowing re-evaluation on some of its signal components based upon established evidences.

Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep

IGF-1 is a critical fetal growth-promoting hormone. Experimental infusion of an IGF-1 analog, human recombinant LR3 IGF-1, into late gestation fetal sheep increased fetal organ growth and skeletal muscle myoblast proliferation. However, LR3 IGF-1 has a low affinity for IGF binding proteins (IGFBP), thus reducing physiologic regulation of IGF-1 bioavailability. The peptide sequences for LR3 IGF-1 and sheep IGF-1 also differ. To overcome these limitations with LR3 IGF-1, we developed an ovine (sheep) specific recombinant IGF-1 (oIGF-1) and tested its effect on growth in fetal sheep. First, we measured in vitro myoblast proliferation in response to oIGF-1. Second, we examined anabolic signaling pathways from serial skeletal muscle biopsies in fetal sheep that received oIGF-1 or saline infusion for 2 hours. Finally, we measured the effect of fetal oIGF-1 infusion versus saline infusion (SAL) for 1 week on fetal body and organ growth, in vivo myoblast proliferation, skeletal muscle fractional protein synthetic rate, IGFBP expression in skeletal muscle and liver, and IGF-1 signaling pathways in skeletal muscle. Using this approach, we showed that oIGF-1 stimulated myoblast proliferation in vitro. When infused for 1 week, oIGF-1 increased organ growth of the heart, kidney, spleen, and adrenal glands and stimulated skeletal myoblast proliferation compared to SAL without increasing muscle fractional synthetic rate or hindlimb muscle mass. Hepatic and muscular gene expression of IGFBPs one to three was similar between oIGF-1 and SAL. We conclude that oIGF-1 promotes tissue and organ-specific growth in the normal sheep fetus.

Components of the insulin-like growth factor system in in vivo - and in vitro-derived fetuses of cattle, and the association with growth and development

This experiment was designed to study mechanisms affecting growth of in vivo-derived (IVD) and in vitro-produced (IVP) fetuses of cattle. Day-7 IVD or IVP cattle blastocysts were transferred to recipients, with pregnant females being slaughtered on Days 90 or 180 of gestation or allowed to undergo parturition. Uteri and contents were dissected and physically measured, and maternal and fetal plasma and amniotic and allantoic fluids were collected for IGF-1 and IGF-2 determinations, and IGFBP profile characterization. Transcripts for IGF-1 and IGF-2 mRNA in placental and fetal tissues, and IGF-1r and IGF-2r in placentomes were determined. There was a greater fetal weight in the IVP group, which was associated with greater IGF-1 and IGF-2 concentrations in maternal circulation, and changes in IGFBP profiles within fetal fluids. Day-90 IVP-derived fetuses were longer, had greater organ weights, larger placentomes, less placentome IGF-2r mRNA transcript, and greater maternal IGF-1 and IGF-2 concentrations than controls. On Day 180 and at parturition tissues from IVP-derived fetuses/calves were from larger uteri, with larger placentomes/fetal membranes, fetuses/calves weighed more, had greater fetal hepatic IGF-2 mRNA transcript, had less fetal plasma IGF-1 and greater allantoic IGF-2 concentrations, greater and lesser IGFBP activities in the allantoic and amniotic fluids, respectively, and greater glucose and fructose accumulation in fetal fluids. Components of the IGF system were differentially regulated not only according to the gestation period (Days 90 or 180) and fluid type (maternal or fetal plasma, amniotic or allantoic fluids), but also based on conceptus origin (IVP or IVD) in cattle.

Significance of highly phosphorylated insulin-like growth factor binding protein-1 and cervical length for prediction of preterm delivery in twin pregnancies

BACKGROUND

A twin pregnancy can carry greater risks than singleton pregnancies. About 60 in 100 twin pregnancies result in spontaneous birth before 37 wk, which is associated with several complications in the premature babies. Clinical detection of biomarkers may help to predict the possibility of premature birth so that corresponding interventions can be given to the pregnant women in a timely manner, in order to reduce the risk of preterm birth and improve the outcomes of the newborn infants.

AIM

To explore the clinical value of transvaginal ultrasound measurement of cervical length combined with insulin-like growth factor binding protein-1 (IGFBP-1) hyperphosphorylation in cervical secretions as predictors of preterm delivery in twin pregnancies.

METHODS

A total of 254 pregnant women with twin pregnancies, who were admitted to Hainan General Hospital and underwent maternity examination, were selected as the study subjects from January 2015 to December 2018. All participants received transvaginal ultrasound measurement of cervical length and phosphorylated IGFBP-1 (phIGFBP-1) test between 24 and 34 wk gestation. The pregnancy outcomes were analyzed.

RESULTS

Of the women with a positive phIGFBP-1 test result, preterm birth rate was higher in those with a cervical length ≤ 25 mm than those with a cervical length > 25 mm (all P < 0.05). Similarly, in women with a negative phIGFBP-1 test result, preterm birth rate was higher in those with a cervical length ≤ 25 mm than those with a cervical length > 25 mm (all P < 0.05). The sensitivity, specificity, and positive and negative predictive values of the phIGFBP-1 test combined with the cervical length test were 95.71%, 91.21%, 95.12% and 92.22%, respectively, for the prediction of preterm birth.

CONCLUSION

Cervical length combined with phIGFBP-1 tests is of value for the prediction of outcomes of preterm delivery in twin pregnancies.

IGFBP-1 in cancer: expression, molecular mechanisms, and potential clinical implications

Insulin-like growth factor binding protein-1 (IGFBP-1) belongs to the insulin-like growth factor (IGF) system, which plays an indispensable role in normal growth and development, and in the pathophysiology of various tumors. IGFBP-1 has been shown to be associated with the risk of various tumors, and has a vital function in regulating tumor behaviors such as proliferation, migration, invasion and adhesion through different molecular mechanisms. The biological actions of IGFBP-1 in cancer are found to be related to its phosphorylation state, and the IGF-dependent and -independent mechanisms. In this review, we provided an overview of IGFBP-1 in normal physiology, and its aberrantly expression and the underlying molecular mechanisms in a range of common tumors, as well as discussed the potential clinical implications of IGFBP-1 as diagnostic or prognostic biomarkers in cancer.

MMP9 and IGFBP1 Regulate Tumor Immune and Drive Tumor Progression in Clear Cell Renal Cell Carcinoma

Immunotherapy is a novel approach and has been used in various diseases, especially in cancers. Recently, immunotherapy has gradually been used to treat advanced clear cell renal cell carcinoma (ccRCC) or metastatic ccRCC. However, the efficacy of immunotherapy is not satisfying due to the influence of the tumor microenvironment. In this study, we mainly focused on the abundance and function of tumor-infiltrating immune cells (TIICs). Monocyte and TNM stage were identified as independent prognostic factors via CIBERSORT and Cox regression analysis. Then, ccRCC patients were divided into high risk/TNMhighMonocyteslow cluster and low risk/TNMlowMonocyteshigh cluster. Further differential gene analysis, protein-protein interaction (PPI) network, and survival analysis screened nine hub genes between the above two clusters. MMP9 and IGFBP1 were selected for further study through sample validation. Moreover, gene set enrichment analysis revealed that MMP9 and IGFBP1 were involved in tumor immune via mediating cell surface receptor signal pathway, cytokine production pathway, or monocyte signal pathway. In conclusion, these findings suggested that monocyte acted as a protective factor and MMP9/IGFBP1 played a vital role in tumor immune, which might become potential novel biomarkers and therapeutic targets for immunotherapy in ccRCC.

Hyperphosphorylation of fetal liver IGFBP-1 precedes slowing of fetal growth in nutrient-restricted baboons and may be a mechanism underlying IUGR

In cultured fetal liver cells, insulin-like growth factor (IGF) binding protein (IGFBP)-1 hyperphosphorylation in response to hypoxia and amino acid deprivation is mediated by inhibition of mechanistic target of rapamycin (mTOR) and activation of amino acid response (AAR) signaling and casein kinase (CK)2. We hypothesized that fetal liver mTOR inhibition, activation of AAR and CK2, and IGFBP-1 hyperphosphorylation occur before development of intrauterine growth restriction (IUGR). Pregnant baboons were fed a control (C) or a maternal nutrient restriction (MNR; 70% calories of control) diet starting at gestational day (GD) 30 (term GD 185). Umbilical blood and fetal liver tissue were obtained at GD 120 (C, n = 7; MNR, n = 10) and 165 (C, n = 7; MNR, n = 8). Fetal weights were unchanged at GD 120 but decreased at GD 165 in the MNR group (-13%, P = 0.03). IGFBP-1 phosphorylation, as determined by parallel reaction monitoring mass spectrometry (PRM-MS), immunohistochemistry, and/or Western blot, was enhanced in MNR fetal liver and umbilical plasma at GD 120 and 165. IGF-I receptor autophosphorylation^Tyr1135 (-64%, P = 0.05) was reduced in MNR fetal liver at GD 120. Furthermore, fetal liver CK2 (α/α'/β) expression, CK2β colocalization, proximity with IGFBP-1, and CK2 autophosphorylation^Tyr182 were greater at GD 120 and 165 in MNR vs. C. Additionally, mTOR complex (mTORC)1 (p-P70S6K^Thr389, -52%, P = 0.05) and mTORC2 (p-Akt^Ser473, -56%, P < 0.001) activity were decreased and AAR was activated (p-GCN2^Thr898, +117%, P = 0.02; p-eIF2α^Ser51, +294%, P = 0.002; p-ERK^Thr202, +111%, P = 0.03) in MNR liver at GD 120. Our data suggest that fetal liver IGFBP-1 hyperphosphorylation, mediated by mTOR inhibition and both AAR and CK2 activation, is a key link between restricted nutrient and oxygen availability and the development of IUGR.

IGFBP-1 Expression Promotes Tamoxifen Resistance in Breast Cancer Cells via Erk Pathway Activation

Insulin-like growth factor (IGF) system plays a significant role in many cellular processes, including proliferation, and survival. In estrogen receptor positive breast cancer, the level of circulating IGF-1 is positively associated with the incidence and at least 50% of cases have elevated IGF-1R signaling. Tamoxifen, a selective estrogen receptor modulator and antagonist for estrogen receptor alpha (ERα) in breast tissue, is a commonly prescribed adjuvant treatment for patients presenting with ERα-positive breast cancer. Unfortunately, tamoxifen resistance is a frequent occurrence in patients receiving treatment and the molecular mechanisms that underlie tamoxifen resistance not adequately defined. It has recently been reported that the inhibition of IGF-1R activation and the proliferation of breast cancer cells upon tamoxifen treatment is mediated by the accumulation of extracellular insulin-like growth factor binding protein 1 (IGFBP-1). Elevated IGFBP-1 expression was observed in tamoxifen-resistant (Tam^R) MCF-7 and T-47D cells lines suggesting that the tamoxifen-resistant state is associated with IGFBP-1 accumulation. MCF-7 and T-47D breast cancer cells stably transfected with and IGFBP-1 expression vector were generated (MCF7-BP1 and T47D-BP1) to determine the impact of breast cancer cell culture in the presence of increased IGFBP-1 expression. In these cells, the expression of IGF-1R was significantly reduced compared to controls and was similar to our observations in tamoxifen-resistant MCF-7 and T-47D cells. Also similar to Tam^R breast cancer cells, MCF7-BP1 and T47D-BP1 were resistant to tamoxifen treatment, had elevated epidermal growth factor receptor (EGFR) expression, increased phospho-EGFR (pEGFR), and phospho-Erk (pErk). Furthermore, tamoxifen sensitivity was restored in the MCF7-BP1 and T47D-BP1 upon inhibition of Erk phosphorylation. Lastly, the transient knockdown of IGFBP-1 in MCF7-BP1 and T47D-BP1 inhibited pErk accumulation and increased tamoxifen sensitivity. Taken together, these data support the conclusion that IGFBP-1 is a key component of the development of tamoxifen resistance in breast cancer cells.

Molecular cloning and expression pattern of IGFBP-2a in black porgy (Acanthopagrus schlegelii) and evolutionary analysis of IGFBP-2s in the species of Perciformes

Insulin-like growth factor-binding protein-2 (IGFBP-2) plays a key role in regulating growth and development by its affinity with insulin-like growth factors (IGFs). In this study, we cloned the coding sequence (CDS) of IGFBP-2a from the black porgy (Acanthopagrus schlegelii) muscle and identified that the full-length CDS of IGFBP-2a was 882 bp. Real-time quantitative PCR revealed that IGFBP-2a was most abundant in the liver of the black porgy and backcross breed (F1♀×black porgy♂) but remained lower in each tested tissue in self-cross breed (F1♀×F1♂). In addition, the IGFBP-2a expression in the liver of three breeds showed a negative correlation with their growth rates, indicating that the IGFBP-2a played a growth-inhibiting role in the three breeds. We further identified 810 bp IGFBP-2b gene from the draft genome of black porgy. Finally, we examined the IGFBP-2a and IGFBP-2b genes by scanning the genomes of the species of Perciformes and found the IGFBP-2 gene duplication took place earlier than the divergence of perciform species. Interestingly, six positively selected sites were detected in both Perciformes IGFBP-2 genes, although both genes were identified to be under purifying selection. Specially, these positively selected sites were located in the functional domains, suggesting these sites played key roles in the growth of Perciformes. Our study partially explains the molecular basis for the prepotency in black porgy hybrids, which will provide guidance for their cultivation in the future.

Prenatal vitamin D and cord blood insulin-like growth factors in Dhaka, Bangladesh

Fetal growth restriction is linked to adverse health outcomes and is prevalent in low- and middle-income countries; however, determinants of fetal growth are still poorly understood. The objectives were to determine the effect of prenatal vitamin D supplementation on the insulin-like growth factor (IGF) axis at birth, to compare the concentrations of IGF-I in newborns in Bangladesh to a European reference population and to estimate the associations between IGF protein concentrations and birth size. In a randomized controlled trial in Dhaka, Bangladesh, pregnant women enrolled at 17-24 weeks of gestation were assigned to weekly oral vitamin D3 supplementation from enrolment to delivery at doses of 4200 IU/week, 16,800 IU/week, 28,000 IU/week or placebo. In this sub-study, 559 woman-infant pairs were included for analysis and cord blood IGF protein concentrations were quantified at birth. There were no significant effects of vitamin D supplementation on cord blood concentrations of IGF-I (P = 0.398), IGF-II (P = 0.525), binding proteins (BPs) IGFBP-1 (P = 0.170), IGFBP-3 (P = 0.203) or the molar ratio of IGF-I/IGFBP-3 (P = 0.941). In comparison to a European reference population, 6% of girls and 23% of boys had IGF-I concentrations below the 2.5th percentile of the reference population. IGF-I, IGF-II, IGFBP-3 and the IGF-I/IGFBP-3 ratio were positively associated with at least one anthropometric parameter, whereas IGFBP-1 was negatively associated with birth anthropometry. In conclusion, prenatal vitamin D supplementation does not alter or enhance fetal IGF pathways.

Novel roles of mechanistic target of rapamycin signaling in regulating fetal growth†

Mechanistic target of rapamycin (mTOR) signaling functions as a central regulator of cellular metabolism, growth, and survival in response to hormones, growth factors, nutrients, energy, and stress signals. Mechanistic TOR is therefore critical for the growth of most fetal organs, and global mTOR deletion is embryonic lethal. This review discusses emerging evidence suggesting that mTOR signaling also has a role as a critical hub in the overall homeostatic control of fetal growth, adjusting the fetal growth trajectory according to the ability of the maternal supply line to support fetal growth. In the fetus, liver mTOR governs the secretion and phosphorylation of insulin-like growth factor binding protein 1 (IGFBP-1) thereby controlling the bioavailability of insulin-like growth factors (IGF-I and IGF-II), which function as important growth hormones during fetal life. In the placenta, mTOR responds to a large number of growth-related signals, including amino acids, glucose, oxygen, folate, and growth factors, to regulate trophoblast mitochondrial respiration, nutrient transport, and protein synthesis, thereby influencing fetal growth. In the maternal compartment, mTOR is an integral part of a decidual nutrient sensor which links oxygen and nutrient availability to the phosphorylation of IGFBP-1 with preferential effects on the bioavailability of IGF-I in the maternal-fetal interface and in the maternal circulation. These new roles of mTOR signaling in the regulation fetal growth will help us better understand the molecular underpinnings of abnormal fetal growth, such as intrauterine growth restriction and fetal overgrowth, and may represent novel avenues for diagnostics and intervention in important pregnancy complications.

Embryonic arsenic exposure reduces intestinal cell proliferation and alters hepatic IGF mRNA expression in killifish (Fundulus heteroclitus)

Arsenic (As) is a toxicant found in food and water throughout the world, and studies suggested that exposure early in life reduces growth. Thus, the goal of this study was to examine mechanisms by which As impacted organismal growth. Killifish (Fundulus heteroclitus) were exposed to 0, 10, 50, or 200 ppb As as embryos and, after hatching, were reared in clean water for up to 40 weeks. Metabolism studies revealed that killifish biotransform As such that monomethylated and dimethylated arsenicals account for 15-17% and 45-61%, respectively, of the total metal. Growth, as measured by condition factor (CF), was significantly and dose-dependently reduced at 8 weeks of age but was similar to controls by 40 weeks. To determine mechanisms underlying the observed initial decrease, intestinal proliferation and morphology were examined. Arsenic-exposed fish exhibited significant 1.3- to 1.5-fold reduction in intestinal villus height and 1.4- to 1.6-fold decrease in proliferating cell nuclear antigen (PCNA+) intestinal cells at all weeks examined. In addition, there were significant correlations between CF, PCNA+ cells, and intestinal villus height. Upon examining whether fish might compensate for the intestinal changes, it was found that hepatic mRNA expression of insulin-like growth factor 1 (IGF-1) and its binding protein (IGFBP-1) were dose-dependently increased. These results indicate that embryonic exposure initially diminished growth, and while intestinal cell proliferation remained reduced, fish appear to compensate by enhancing transcript levels of hepatic IGF-1 and IGFBP-1.

The role of fetal growth restriction in the association between Down syndrome and perinatal mortality

Objective: Down syndrome (DS) is associated with significant risk of perinatal mortality. We hypothesize that this association is primarily mediated through the effects of fetal growth restriction (FGR).Methods: This was a retrospective cohort analysis using the US Natality Database from 2011 to 2013. Analysis was limited to singleton nonanomalous pregnancies or confirmed DS pregnancies without severe structural anomalies between 24 and 42 w in gestation. The risk of stillbirth (SB) associated with DS was estimated using both Cox proportional Hazard (HR) regression and accelerated failure time (AFT) methods. The risk of neonatal mortality was estimated using logistic regression analyses. Mediation analysis was then performed to estimate the effect of small for gestational age (SGA), defined as birthweight ≤10th percentile for gestational age, on perinatal mortality associated with DS. All regression models were selected using backward stepwise elimination method. The final regression models included adjustment for maternal age, hypertension, and diabetes.Results: The final cohort included 2446 DS cases among 9,804,718 births. The overall SB rate was 223.6/1000 births in DS group and 4.7/1000 births without DS (p < .001, adjusted hazard ratio (aHR): 58.25; 95% CI [53.44,63.49]). Based on the AFT model, DS survival-to-delivery rate is 4.3 times lower (TR: 0.23; 95% CI [0.22,0.24]). Thirty-five percentage of the effect of DS on stillbirth was mediated through SGA (% mediation:35.1%; 95% CI [33.7,36.4]). The rate of neonatal mortality among DS was 69.0/1000 births compared with 2.8/1000 births without DS (p < .001, adjusted odds ratio (aOR): 27.16; 95% CI: [22.63,32.60]). Only 11.6% of the effect of DS on neonatal deaths was mediated through SGA (%mediation:11.6%; 95% CI [8.4,10.6]).Conclusion: Over one-third of overall stillbirths were mediated through SGA. Routine surveillance of fetal growth and standard SGA surveillance protocols may reduce the risk of perinatal mortality in DS pregnancies. Conversely, it is important to point out that these surveillance strategies may not be effective two-third of the cases not affected by growth restriction.

IGF-binding proteins

Insulin-like growth factor-binding proteins (IGFBPs) 1-6 bind IGFs but not insulin with high affinity. They were initially identified as serum carriers and passive inhibitors of IGF actions. However, subsequent studies showed that, although IGFBPs inhibit IGF actions in many circumstances, they may also potentiate these actions. IGFBPs are widely expressed in most tissues, and they are flexible endocrine and autocrine/paracrine regulators of IGF activity, which is essential for this important physiological system. More recently, individual IGFBPs have been shown to have IGF-independent actions. Mechanisms underlying these actions include (i) interaction with non-IGF proteins in compartments including the extracellular space and matrix, the cell surface and intracellular space, (ii) interaction with and modulation of other growth factor pathways including EGF, TGF-β and VEGF, and (iii) direct or indirect transcriptional effects following nuclear entry of IGFBPs. Through these IGF-dependent and IGF-independent actions, IGFBPs modulate essential cellular processes including proliferation, survival, migration, senescence, autophagy and angiogenesis. They have been implicated in a range of disorders including malignant, metabolic, neurological and immune diseases. A more complete understanding of their cellular roles may lead to the development of novel IGFBP-based therapeutic opportunities.

Increased Insulin-like Growth Factor Binding Protein-1 Phosphorylation in Decidualized Stromal Mesenchymal Cells in Human Intrauterine Growth Restriction Placentas

Intrauterine growth restriction (IUGR) is often caused by placental insufficiency, which is believed to be associated with decreased delivery of oxygen and nutrients to the placental barrier. We recently reported that hypoxia and/or leucine deprivation triggered hyperphosphorylation of insulin-like growth factor binding protein-1 (IGFBP-1) in decidualized human immortalized endometrial stromal cells (HIESCs), resulting in decreased insulin-like growth factor-1 (IGF-1) bioactivity. To test the hypothesis that human IUGR is associated with increased decidual IGFBP-1 phosphorylation at discrete sites, we used IUGR and gestational age matched appropriate for gestational age (AGA) placentas ( n=5 each). We performed dual immunofluorescence immunohistochemistry (IHC) using IGFBP-1 and vimentin as decidual and mesenchymal markers, respectively. Employing a unique strategy with imaging software, we extracted signal intensity of IGFBP-1 expressed specifically from truly decidualized cells of the placenta. Relative IGFBP-1 was increased (85%; p=0.0001) and using custom phospho-site-specific antibodies, we found that IGFBP-1 phosphorylation (pSer101; +40%, p=0.0677/pSer119; +60%, p=0.0064/pSer169; +100%, p=0.0021) was markedly enhanced in IUGR. Together, our data links for the first time, increased decidual IGFBP-1 phosphorylation at discrete sites with human IUGR. These novel findings suggest that hyperphosphorylation of IGFBP-1 in decidualized stromal mesenchymal decidua basalis contributes to potentially elevated levels of phosphorylated IGFBP-1 in maternal circulation in IUGR pregnancies.

Co-Localization of Insulin-Like Growth Factor Binding Protein-1, Casein Kinase-2β, and Mechanistic Target of Rapamycin in Human Hepatocellular Carcinoma Cells as Demonstrated by Dual Immunofluorescence and in Situ Proximity Ligation Assay

Insulin-like growth factor binding protein (IGFBP)-1 influences fetal growth by modifying insulin-like growth factor-I (IGF-I) bioavailability. IGFBP-1 phosphorylation, which markedly increases its affinity for IGF-I, is regulated by mechanistic target of rapamycin (mTOR) and casein kinase (CSNK)-2. However, the underlying molecular mechanisms remain unknown. We examined the cellular localization and potential interactions of IGFBP-1, CSNK-2β, and mTOR as a prerequisite for protein-protein interaction. Analysis of dual immunofluorescence images indicated a potential perinuclear co-localization between IGFBP-1 and CSNK-2β and a nuclear co-localization between CSNK-2β and mTOR. Proximity ligation assay (PLA) indicated proximity between IGFBP-1 and CSNK-2β as well as mTOR and CSNK-2β but not between mTOR and IGFBP-1. Three-dimensional rendering of the PLA images validated that IGFBP-1 and CSNK-2β interactions were in the perinuclear region and mTOR and CSNK-2β interactions were also predominantly perinuclear rather than nuclear as indicated by mTOR and CSNK-2β co-localization. Compared with control, hypoxia and rapamycin treatment showed markedly amplified PLA signals for IGFBP-1 and CSNK-2β (approximately 18-fold, P = 0.0002). Stable isotope labeling with multiple reaction monitoring-mass spectrometry demonstrated that hypoxia and rapamycin treatment increased IGFBP-1 phosphorylation at Ser98/Ser101/Ser119/Ser174 but most considerably (106-fold) at Ser169. We report interactions between CSNK-2β and IGFBP-1 as well as mTOR and CSNK-2β, providing strong evidence of a mechanistic link between mTOR and IGF-I signaling, two critical regulators of cell growth via CSNK-2.

Regulation of Placental Development and Its Impact on Fetal Growth-New Insights From Mouse Models

The placenta is the chief regulator of nutrient supply to the growing embryo during gestation. As such, adequate placental function is instrumental for developmental progression throughout intrauterine development. One of the most common complications during pregnancy is insufficient growth of the fetus, a problem termed intrauterine growth restriction (IUGR) that is most frequently rooted in a malfunctional placenta. Together with conventional gene targeting approaches, recent advances in screening mouse mutants for placental defects, combined with the ability to rapidly induce mutations in vitro and in vivo by CRISPR-Cas9 technology, has provided new insights into the contribution of the genome to normal placental development. Most importantly, these data have demonstrated that far more genes are required for normal placentation than previously appreciated. Here, we provide a summary of common types of placental defects in established mouse mutants, which will help us gain a better understanding of the genes impacting on human placentation. Based on a recent mouse mutant screen, we then provide examples on how these data can be mined to identify novel molecular hubs that may be critical for placental development. Given the close association between placental defects and abnormal cardiovascular and brain development, these functional nodes may also shed light onto the etiology of birth defects that co-occur with placental malformations. Taken together, recent insights into the regulation of mouse placental development have opened up new avenues for research that will promote the study of human pregnancy conditions, notably those based on defects in placentation that underlie the most common pregnancy pathologies such as IUGR and pre-eclampsia.

Blood-based biomarkers of adverse perinatal outcomes in maternal obesity

OBJECTIVE

Increasing maternal weight has been shown to predict adverse perinatal outcome, including increases in the relative risk of fetal death, stillbirth, neonatal death, perinatal death and infant death. In order to better understand the pathophysiological factors associated with obesity during pregnancy, the role of biomarkers associated with adverse outcomes in obese pregnant women is under investigation. The purpose of this review study was to examine potential biomarkers that could serve as effective screening strategies in obese pregnant women to reduce fetal and neonatal morbidity, as well as maternal morbidity.

METHODS

Electronic databases (Pubmed, Embase) were searched for previously published research studies that investigated biomarkers associated with perinatal outcomes in obese pregnant women and the putative mechanisms underlying biomarker effects on pregnancy outcomes.

RESULTS

It is evident that while several biomarkers predict perinatal complications in obese pregnant women, none fulfilled the criteria to be considered clinically useful.

CONCLUSION

There is a critical need for reliable blood-based biomarkers associated with an increased risk of adverse perinatal outcomes in obese pregnant women.

Expression and localization of ARTEMIN in the bovine uterus and embryos

Artemin a member of the glial cell line-derived neurotrophic factor (GDNF) family is present in mice and human preimplantation embryos, and reproductive tract, during early pregnancy promoting embryo development in vitro. The presence of artemin in cattle embryos and reproductive tract, however, is unknown. In the present work we identified for first time artemin in bovine uterine fluid (UF) (Western blot), endometrium (RT-PCR, Western blot and immunohistochemistry) and embryos (RT-PCR and immunohistochemistry) during early preimplantation development. In addition, GFRalpha3, a component of the artemin receptor was localized in blastocysts produced in vitro. Individually developing embryos released ARTEMIN in culture medium and triggered ARTEMIN mRNA down-regulation in epithelial cells from endometrial cell cultures. Our results suggest that ARTEMIN derived from early embryos and maternal reproductive tract may exert important roles during early development in cattle.

Knockout maternal adiponectin increases fetal growth in mice: potential role for trophoblast IGFBP-1

AIMS/HYPOTHESIS

The main objective of this study was to investigate whether maternal adiponectin regulates fetal growth through the endocrine system in the fetal compartment.

METHODS

Adiponectin knockout (Adipoq (-/-) ) mice and in vivo adenovirus-mediated reconstitution were used to study the regulatory effect of maternal adiponectin on fetal growth. Primary human trophoblast cells were treated with adiponectin and a specific peroxisome proliferator-activated receptor α (PPARα) agonist or antagonist to study the underlying mechanism through which adiponectin regulates fetal growth.

RESULTS

The body weight of fetuses from Adipoq (-/-) dams was significantly greater than that of wild-type dams at both embryonic day (E)14.5 and E18.5. Adenoviral vector-mediated maternal adiponectin reconstitution attenuated the increased fetal body weight induced by maternal adiponectin deficiency. Significantly increased blood glucose, triacylglycerol and NEFA levels were observed in Adipoq (-/-) dams, suggesting that nutrient supply contributes to maternal adiponectin-regulated fetal growth. Although fetal blood IGF-1 concentrations were comparable in fetuses from Adipoq (-/-) and wild-type dams, remarkably low levels of IGF-binding protein 1 (IGFBP-1) were observed in the serum of fetuses from Adipoq (-/-) dams. IGFBP-1 was identified in the trophoblast cells of human and mouse placentas. Maternal fasting robustly increased IGFBP-1 levels in mouse placentas, while reducing fetal weight. Significantly low IGFBP-1 levels were found in placentas of Adipoq (-/-) dams. Adiponectin treatment increased IGFBP-1 levels in primary cultured human trophoblast cells, while the PPARα antagonist, MK886, abolished this stimulatory effect.

CONCLUSIONS/INTERPRETATION

These results indicate that, in addition to nutrient supply, maternal adiponectin inhibits fetal growth by increasing IGFBP-1 expression in trophoblast cells.

Increased IGFBP-1 phosphorylation in response to leucine deprivation is mediated by CK2 and PKC

Insulin-like growth factor binding protein-1 (IGFBP-1), secreted by fetal liver, is a key regulator of IGF-I bioavailability and fetal growth. IGFBP-1 phosphorylation decreases IGF-I bioavailability and diminishes its growth-promoting effects. Growth-restricted fetuses have decreased levels of circulating essential amino acids. We recently showed that IGFBP-1 hyperphosphorylation (pSer101/119/169) in response to leucine deprivation is regulated via activation of the amino acid response (AAR) in HepG2 cells. Here we investigated nutrient-sensitive protein kinases CK2/PKC/PKA in mediating IGFBP-1 phosphorylation in leucine deprivation. We demonstrated that leucine deprivation stimulated CK2 activity (enzymatic assay) and induced IGFBP-1 phosphorylation (immunoblotting/MRM-MS). Inhibition (pharmacological/siRNA) of CK2/PKC, but not PKA, prevented IGFBP-1 hyperphosphorylation in leucine deprivation. PKC inhibition also prevented leucine deprivation-stimulated CK2 activity. Functionally, leucine deprivation decreased IGF-I-induced-IGF-1R autophosphorylation when CK2/PKC were not inhibited. Our data strongly support that PKC promotes leucine deprivation-induced IGFBP-1 hyperphosphorylation via CK2 activation, mechanistically linking decreased amino acid availability and reduced fetal growth.

Hypoxia Increases IGFBP-1 Phosphorylation Mediated by mTOR Inhibition

In fetal growth restriction (FGR), fetal growth is limited by reduced nutrient and oxygen supply. Insulin-like growth factor I (IGF-I) is a key regulator of fetal growth and IGF binding protein -1(IGFBP-1) is the principal regulator of fetal IGF-I bioavailability. Phosphorylation enhances IGFBP-1's affinity for IGF-I. Hypoxia induces IGFBP-1 hyperphosphorylation, markedly decreasing IGF-I bioavailability. We recently reported that fetal liver IGFBP-1 hyperphosphorylation is associated with inhibition of the mechanistic target of rapamycin (mTOR) in a nonhuman primate model of FGR. Here, we test the hypothesis that IGFBP-1 hyperphosphorylation in response to hypoxia is mediated by mTOR inhibition. We inhibited mTOR either by rapamycin or small interfering RNA (siRNA) targeting raptor (mTOR complex [mTORC]1) and/or rictor (mTORC2) in HepG2 cells cultured under hypoxia (1% O2) or basal (20% O2) conditions. Conversely, we activated mTORC1 or mTORC1+mTORC2 by silencing endogenous mTOR inhibitors (tuberous sclerosis complex 2/DEP-domain-containing and mTOR-interacting protein). Immunoblot analysis demonstrated that both hypoxia and inhibition of mTORC1 and/or mTORC2 induced similar degrees of IGFBP-1 phosphorylation at Ser101/119/169 and reduced IGF-I receptor autophosphorylation. Activation of mTORC1+mTORC2 or mTORC1 alone prevented IGFBP-1 hyperphosphorylation in response to hypoxia. Multiple reaction monitoring-mass spectrometry showed that rapamycin and/or hypoxia increased phosphorylation also at Ser98 and at a novel site Ser174. In silico structural analysis indicated that Ser174 was in close proximity to the IGF-binding site. Together, we demonstrate that signaling through the mTORC1 or mTORC2 pathway is sufficient to induce IGFBP-1 hyperphosphorylation in response to hypoxia. This study provides novel understanding of the cellular mechanism that controls fetal IGFBP-1 phosphorylation in hypoxia, and we propose that mTOR inhibition constitutes a mechanistic link between hypoxia, reduced IGF-I bioavailability and FGR.