SUMO-modified insulin-like growth factor 1 receptor (IGF-1R) increases cell cycle progression and cell proliferation

IGF-1R targeting in cancer - does sub-cellular localization matter?

The insulin-like growth factor receptor (IGF-1R) was among the most intensively pursued kinase targets in oncology. However, even after a slew of small-molecule and antibody therapeutics reached clinical trials for a range of solid tumors, the initial promise remains unfulfilled. Mechanisms of resistance to, and toxicities resulting from, IGF-1R-targeted drugs are well-catalogued, and there is general appreciation of the fact that a lack of biomarker-based patient stratification was a limitation of previous clinical trials. But no next-generation therapeutic strategies have yet successfully exploited this understanding in the clinic.Currently there is emerging interest in re-visiting IGF-1R targeted therapeutics in combination-treatment protocols with predictive biomarker-driven patient-stratification. One such biomarker that emerged from early clinical trials is the sub-cellular localization of IGF-1R. After providing some background on IGF-1R, its drugging history, and the trials that led to the termination of drug development for this target, we look more deeply into the correlation between sub-cellular localization of IGF-1R and susceptibility to various classes of IGF-1R - targeted agents.

Secretome from myoblasts statically loaded at low intensity promotes tenocyte proliferation via the IGF-1 receptor pathway

Exercise is widely recognized as beneficial for tendon healing. Recently, it has been described that muscle-derived molecules secreted in response to static exercise influence tendon healing. In this study, the optimal static loading intensity for tendon healing and the composition of secretome released by myoblasts in response to different intensities of static strain were investigated. In an in vitro coculture model, myoblasts were mechanically loaded using a Flexcell Tension System. Tenocytes were seeded on transwell inserts that allowed communication between the tenocytes and myoblasts without direct contact. Proliferation and migration assays, together with RNA sequencing, were used to determine potential cellular signaling pathways. The secretome from myoblasts exposed to 2% static loading increased the proliferation and migration of the cocultured tenocytes. RNA-seq analysis revealed that this loading condition upregulated the expression of numerous genes encoding secretory proteins, including insulin-like growth factor-1 (IGF-1). Confirmation of IGF-1 expression and secretion was carried out using qPCR and enzyme-linked immunosorbt assay (ELISA), revealing a statistically significant upregulation in response to 2% static loading in comparison to both control conditions and higher loading intensities of 5% and 10%. Addition of an inhibitor of the IGF-1 receptor (PQ401) to the tenocytes significantly reduced myoblast secretome-induced tenocyte proliferation. In conclusion, IGF-1 may be an important molecule in the statically loaded myoblast secretome, which is responsible for influencing tenocytes during exercise-induced healing.

Emerging Role of IGF-1 in Prostate Cancer: A Promising Biomarker and Therapeutic Target

Prostate cancer (PCa) is a highly heterogeneous disease driven by gene alterations and microenvironmental influences. Not only enhanced serum IGF-1 but also the activation of IGF-1R and its downstream signaling components has been increasingly recognized to have a vital driving role in the development of PCa. A better understanding of IGF-1/IGF-1R activity and regulation has therefore emerged as an important subject of PCa research. IGF-1/IGF-1R signaling affects diverse biological processes in cancer cells, including promoting survival and renewal, inducing migration and spread, and promoting resistance to radiation and castration. Consequently, inhibitory reagents targeting IGF-1/IGF-1R have been developed to limit cancer development. Multiple agents targeting IGF-1/IGF-1R signaling have shown effects against tumor growth in tumor xenograft models, but further verification of their effectiveness in PCa patients in clinical trials is still needed. Combining androgen deprivation therapy or cytotoxic chemotherapeutics with IGF-1R antagonists based on reliable predictive biomarkers and developing and applying novel agents may provide more desirable outcomes. This review will summarize the contribution of IGF-1 signaling to the development of PCa and highlight the relevance of this signaling axis in potential strategies for cancer therapy.

Molecularly Defined Subsets of Ewing Sarcoma Tumors Differ in Their Responses to IGF1R and WEE1 Inhibition

PURPOSE

Targeted cancer therapeutics have not significantly benefited patients with Ewing sarcoma with metastatic or relapsed disease. Understanding the molecular underpinnings of drug resistance can lead to biomarker-driven treatment selection.

EXPERIMENTAL DESIGN

Receptor tyrosine kinase (RTK) pathway activation was analyzed in tumor cells derived from a panel of Ewing sarcoma tumors, including primary and metastatic tumors from the same patient. Phospho-RTK arrays, Western blots, and IHC were used. Protein localization and the levels of key markers were determined using immunofluorescence. DNA damage tolerance was measured through PCNA ubiquitination levels and the DNA fiber assay. Effects of pharmacologic inhibition were assessed in vitro and key results validated in vivo using patient-derived xenografts.

RESULTS

Ewing sarcoma tumors fell into two groups. In one, IGF1R was predominantly nuclear (nIGF1R), DNA damage tolerance pathway was upregulated, and cells had low replication stress and RRM2B levels and high levels of WEE1 and RAD21. These tumors were relatively insensitive to IGF1R inhibition. The second group had high replication stress and RRM2B, low levels of WEE1 and RAD21, membrane-associated IGF1R (mIGF1R) signaling, and sensitivity to IGF1R or WEE1-targeted inhibitors. Moreover, the matched primary and metastatic tumors differed in IGF1R localization, levels of replication stress, and inhibitor sensitivity. In all instances, combined IGF1R and WEE1 inhibition led to tumor regression.

CONCLUSIONS

IGF1R signaling mechanisms and replication stress levels can vary among Ewing sarcoma tumors (including in the same patient), influencing the effects of IGF1R and WEE1 treatment. These findings make the case for using biopsy-derived predictive biomarkers at multiple stages of Ewing sarcoma disease management.

Withania somnifera (L.) Dunal (Ashwagandha); current understanding and future prospect as a potential drug candidate

Cancer and Neurodegenerative diseases are one of the most dreadful diseases to cure and chemotherapy has found a prime place in cancerous treatments while as different strategies have been tested in neurodegenerative diseases as well. However, due to adverse shortcomings like the resistance of cancerous cells and inefficiency in neurodegenerative disease, plant sources have always found a prime importance in medicinal use for decades, Withania somnifera (L.) Dunal (W. somnifera) is a well-known plant with medicinal use reported for centuries. It is commonly known as winter cherry or ashwagandha and is a prime source of pharmaceutically active compounds withanolides. In recent years research is being carried in understanding the extensive role of W. somnifera in cancer and neurological disorders. W. somnifera has been reported to be beneficial in DNA repair mechanisms; it is known for its cellular repairing properties and helps to prevent the apoptosis of normal cells. This review summarizes the potential properties and medicinal benefits of W. somnifera especially in cancer and neurodegenerative diseases. Available data suggest that W. somnifera is effective in controlling disease progressions and could be a potential therapeutic target benefiting human health status. The current review also discusses the traditional medicinal applications of W. somnifera, the experimental evidence supporting its therapeutical potential as well as obstacles that necessitate being overcome for W. somnifera to be evaluated as a curative agent in humans.

Overview of the regulation of the class IA PI3K/AKT pathway by SUMO

The phosphatidylinositol-3-kinase (PI3K)/AKT pathway is a major regulator of metabolism, migration, survival, proliferation, and antiviral immunity. Both an overactivation and an inhibition of the PI3K/AKT pathway are related to different pathologies. Activation of this signaling pathway is tightly controlled through a multistep process and its deregulation can be associated with aberrant post-translational modifications including SUMOylation. Here, we review the complex modulation of the PI3K/AKT pathway by SUMOylation and we discuss its putative incvolvement in human disease.

Smoothened (SMO) regulates insulin-like growth factor 1 receptor (IGF1R) levels and protein kinase B (AKT) localization and signaling

The oncoprotein Smoothened (SMO), a Frizzled-class-G-protein-coupled receptor, is the central transducer of hedgehog (Hh) signaling. While canonical SMO signaling is best understood in the context of cilia, evidence suggests that SMO has other functions in cancer biology that are unrelated to canonical Hh signaling. Herein, we provided evidence that elevated levels of human SMO show a strong correlation with elevated levels of insulin-like growth factor 1 receptor (IGF1R) and reduced survival in diffuse large B-cell lymphoma (DLBCL). As an integral component of raft microdomains, SMO plays a fundamental role in maintaining the levels of IGF1R in lymphoma and breast cancer cells as well IGF1R-associated activation of protein kinase B (AKT). Silencing of SMO increases lysosomal degradation and favors a localization of IGF1R to late endosomal compartments instead of early endosomal compartments from which much of the receptor would normally recycle. In addition, loss of SMO interferes with the lipid raft localization and retention of the remaining IGF1R and AKT, thereby disrupting the primary signaling context for IGF1R/AKT. This activity of SMO is independent of its canonical signaling and represents a novel and clinically relevant contribution to signaling by the highly oncogenic IGF1R/AKT signaling axis.

A Novel miRNA Y-56 Targeting IGF-1R Mediates the Proliferation of Porcine Skeletal Muscle Satellite Cells Through AKT and ERK Pathways

As a key regulator of gene transcription and post-transcriptional modification, miRNAs play a wide range of roles in skeletal muscle development. Skeletal muscle satellite cells contribute to postnatal growing muscle fibers. Thus, the goal of this study was to explore the effects of novel miRNA Y-56 on porcine skeletal muscle satellite cells (PSCs). We found that Y-56 was highly expressed in porcine muscle tissues, and its expression was higher in Bama Xiang pigs than in Landrace pigs. The EdU assay, cell counting kit-8, and flow cytometry results showed that Y-56 overexpression suppressed cell proliferation and cell cycle, whereas Y-56 inhibition resulted in the opposite consequences. The results of qRT-PCR and Western blot showed that Y-56 remarkably inhibited the expression levels of cyclin-dependent kinase 4 (CDK4), proliferating cell nuclear antigen (PCNA), and cyclin D1. We identified that IGF-1R was a direct target of Y-56 by dual-luciferase reporter assay. Moreover, IGF-1R overexpression promoted the proliferation and cell cycle process of PSCs and upregulated the expression of CDK4, PCNA, and cyclin D1. Conversely, IGF-1R knockdown had the opposite effect. Furthermore, IGF-1R overexpression partially reversed the inhibition of the cell proliferation and cell cycle process of PSCs and the downregulation of the expression of CDK4, PCNA, and Cyclin D1 caused by Y-56 overexpression. Finally, Y-56 inhibited the protein expression levels of p-AKT and p-ERK. Collectively, our findings suggested that Y-56 represses the proliferation and cell cycle process of PSCs by targeting IGF-1R-mediated AKT and ERK pathways.

Integrative Functional Genomic Analysis of Molecular Signatures and Mechanistic Pathways in the Cell Cycle Underlying Alzheimer's Disease

Objective

Alzheimer's disease (AD) is associated with cell cycle reentry of mature neurons that subsequently undergo degeneration. This study is aimed to identify key regulators of the cell cycle and their underlying pathways for developing optimal treatment of AD.

Methods

RNA sequencing data were profiled to screen for differentially expressed genes in the cell cycle. Correlation of created modules with AD phenotype was computed by weight gene correlation network analysis (WGCNA). Signature genes for trophic factor receptors were determined using Pearson correlation coefficient (PCC) analysis.

Results

Among the 13,679 background genes, 775 cell cycle genes and 77 trophic factor receptors were differentially expressed in AD versus nondementia controls. Four coexpression modules were constructed by WGCNA, among which the turquoise module had the strongest correlation with AD. According to PCC analysis, 10 signature trophic receptors most strongly interacting with cell cycle genes were filtered and subsequently displayed in the global regulatory network. Further cross-talking pathways of signature receptors, such as glutamatergic synapse, long-term potentiation, PI3K-Akt, and MAPK signaling pathways, were identified.

Conclusions

Our findings highlighted the mechanistic pathways of signature trophic receptors in cell cycle perturbation underlying AD pathogenesis, thereby providing new molecular targets for therapeutic intervention in AD.

Nuclear IGF1R interacts with NuMA and regulates 53BP1‑dependent DNA double‑strand break repair in colorectal cancer

Nuclear insulin-like growth factor 1 receptor (nIGF1R) has been associated with poor overall survival and chemotherapy resistance in various types of cancer; however, the underlying mechanism remains unclear. In the present study, immunoprecipitation-coupled mass spectrometry was performed in an IGF1R-overexpressing SW480-OE colorectal cancer cell line to identify the nIGF1R interactome. Network analysis revealed 197 proteins of interest which were involved in several biological pathways, including RNA processing, DNA double-strand break (DSB) repair and SUMOylation pathways. Nuclear mitotic apparatus protein (NuMA) was identified as one of nIGF1R's colocalizing partners. Proximity ligation assay (PLA) revealed different levels of p53-binding protein 1 (53BP1)-NuMA colocalization between IGF1R-positive (R⁺) and IGF1R-negative (R⁻) mouse embryonic fibroblasts following exposure to ionizing radiation (IR). 53BP1 was retained by NuMA in the R⁻ cells during IR-induced DNA damage. By contrast, the level of NuMA-53BP1 was markedly lower in R⁺ cells compared with R⁻ cells. The present data suggested a regulatory role of nIGF1R in 53BP1-dependent DSB repair through its interaction with NuMA. Bright-field PLA analysis on a paraffin-embedded tissue microarray from patients with colorectal cancer revealed a significant association between increased nuclear colocalizing signals of NuMA-53BP1 and a shorter overall survival. These results indicate that nIGF1R plays a role in facilitating 53BP1-dependent DDR by regulating the NuMA-53BP1 interaction, which in turn might affect the clinical outcome of patients with colorectal cancer.

The Role of IGF/IGF-IR-Signaling and Extracellular Matrix Effectors in Bone Sarcoma Pathogenesis

Simple Summary

Bone sarcomas are mesenchymal origin tumors. Bone sarcoma patients show a variable response or do not respond to chemotherapy. Notably, improving efficient chemotherapy approaches, dealing with chemoresistance, and preventing metastasis pose unmet challenges in sarcoma therapy. Insulin-like growth factors 1 and 2 (IGF-1 and -2) and their respective receptors are a multifactorial system that significantly contributes to bone sarcoma pathogenesis. Most clinical trials aiming at the IGF pathway have had limited success. Developing combinatorial strategies to enhance antitumor responses and better classify the patients that could best benefit from IGF-axis targeting therapies is in order. A plausible approach for developing a combinatorial strategy is to focus on the tumor microenvironment (TME) and processes executed therein. Herewith, we will discuss how the interplay between IGF-signaling and the TME constituents affects bone sarcomas’ basal functions and their response to therapy. Potential direct and adjunct therapeutical implications of the extracellular matrix (ECM) effectors will also be summarized.

Abstract

Bone sarcomas, mesenchymal origin tumors, represent a substantial group of varying neoplasms of a distinct entity. Bone sarcoma patients show a limited response or do not respond to chemotherapy. Notably, developing efficient chemotherapy approaches, dealing with chemoresistance, and preventing metastasis pose unmet challenges in sarcoma therapy. Insulin-like growth factors 1 and 2 (IGF-1 and -2) and their respective receptors are a multifactorial system that significantly contributes to bone sarcoma pathogenesis. Whereas failures have been registered in creating novel targeted therapeutics aiming at the IGF pathway, new agent development should continue, evaluating combinatorial strategies for enhancing antitumor responses and better classifying the patients that could best benefit from these therapies. A plausible approach for developing a combinatorial strategy is to focus on the tumor microenvironment (TME) and processes executed therein. Herewith, we will discuss how the interplay between IGF-signaling and the TME constituents affects sarcomas’ basal functions and their response to therapy. This review highlights key studies focusing on IGF signaling in bone sarcomas, specifically studies underscoring novel properties that make this system an attractive therapeutic target and identifies new relationships that may be exploited. Potential direct and adjunct therapeutical implications of the extracellular matrix (ECM) effectors will also be summarized.

Lessons to Learn for Adequate Targeted Therapy Development in Metastatic Colorectal Cancer Patients

Insulin-like growth factor 1 receptor (IGF1R) is a receptor tyrosine kinase that regulates cell growth and proliferation. Upregulation of the IGF1R pathway constitutes a common paradigm shared with other receptor tyrosine kinases such as EGFR, HER2, and MET in different cancer types, including colon cancer. The main IGF1R signaling pathways are PI3K-AKT and MAPK-MEK. However, different processes, such as post-translational modification (SUMOylation), epithelial-to-mesenchymal transition (EMT), and microenvironment complexity, can also contribute to intrinsic and acquired resistance. Here, we discuss new strategies for adequate drug development in metastatic colorectal cancer patients.

The Role of Nuclear Insulin and IGF1 Receptors in Metabolism and Cancer

Insulin (InsR) and insulin-like growth factor-1 (IGF1R) receptors mediate the metabolic and growth-promoting actions of insulin and IGF1/IGF2, respectively. Evidence accumulated in recent years indicates that, in addition to their typical cell-surface localization pattern and ligand-activated mechanism of action, InsR and IGF1R are present in the cell nucleus of both normal and transformed cells. Nuclear translocation seems to involve interaction with a small, ubiquitin-like modifier protein (SUMO-1), although this modification is not always a prerequisite. Nuclear InsR and IGF1R exhibit a number of biological activities that classically fit within the definition of transcription factors. These nuclear activities include, among others, sequence-specific DNA binding and transcriptional control. Of particular interest, nuclear IGF1R was capable of binding and stimulating its cognate gene promoter. The physiological relevance of this autoregulatory mechanism needs to be further investigated. In addition to its nuclear localization, studies have identified IGF1R in the Golgi apparatus, and this particular distribution correlated with a migratory phenotype. In summary, the newly described roles of InsR and IGF1R as gene regulators, in concert with their atypical pattern of subcellular distribution, add a further layer of complexity to traditional models of cell signaling. Furthermore, and in view of the emerging role of IGF1R as a potential therapeutic target, a better understanding of the mechanisms responsible for nuclear IGF1R transport and identification of IGF1R interactors might help optimize target directed therapies in oncology.

Ginkgoic acid impedes gastric cancer cell proliferation, migration and EMT through inhibiting the SUMOylation of IGF-1R

The imbalance of SUMOylation is related to different cancers, including gastric cancer (GC). Ginkgolic acid (GA) inhibits the growth and invasion of many cancer cells, and it has been reported to restrain SUMOylation. However, the role of GA in GC and whether it functions through SUMOylation remains to be clarified. Our research revealed that GA (15:1) inhibited cell proliferation, migration, epithelial-mesenchymal transition (EMT) and overall protein SUMOylation in BGC823 and HGC27 cells. In addition, knockdown of SUMO1 (small ubiquitin-like modifier) instead of SUMO2/3 played a similar role to GA in cell behaviors. Besides, nuclear IGF-1R (insulin-like growth factor 1 receptor) expression was markedly upregulated in GC cells compared to normal gastric epithelial cells. GA prevented IGF-1R from binding to SUMO1, thereby suppressing its nuclear accumulation. Further research found that IGF-1R directly bound to SNAI2 (snail family zinc finger 2) promoter. The interference of IGF-1R downregulated the mRNA and protein levels of SNAI2, while the overexpression of SUMO1, IGF-1R and UBC9 (SUMO-conjugating enzyme) played the opposite role. Furthermore, the co-transfection of SUMO1, UBC9 and IGF-1R vectors or the overexpression of SNAI2 reversed the inhibitory effects of GA on cell proliferation, migration and EMT. Finally, GA impeded the growth of GC xenografts and decreased the expression of nuclear IGF-1R and SNAI2 in vivo. In conclusion, these findings demonstrated that GA hindered the progression of GC by inhibiting the SUMOylation of IGF-1R. Thus, GA might be a promising therapeutic for GC.

Niche Modulation of IGF-1R Signaling: Its Role in Stem Cell Pluripotency, Cancer Reprogramming, and Therapeutic Applications

Stem cells work with their niches harmoniously during development. This concept has been extended to cancer pathology for cancer stem cells (CSCs) or cancer reprogramming. IGF-1R, a classical survival signaling, has been shown to regulate stem cell pluripotency, CSCs, or cancer reprogramming. The mechanism underlying such cell fate determination is unclear. We propose the determination is due to different niches in embryo development and tumor malignancy which modulate the consequences of IGF-1R signaling. Here we highlight the modulations of these niche parameters (hypoxia, inflammation, extracellular matrix), and the targeted stem cells (embryonic stem cells, germline stem cells, and mesenchymal stem cells) and CSCs, with relevance to cancer reprogramming. We organize known interaction between IGF-1R signaling and distinct niches in the double-sided cell fate with emerging trends highlighted. Based on these new insights, we propose that, through targeting IGF-1R signaling modulation, stem cell therapy and cancer stemness treatment can be further explored.

Screening of immune-related differentially expressed genes from primary lymphatic organs of broilers fed with probiotic bacillus cereus PAS38 based on suppression subtractive hybridization

To explore the molecular mechanism of the effect of Bacillus cereus PAS38 on the immunity of broilers, sixty 7-day-old broilers were divided into two groups with three replicates. The control group was fed with basal diet, and the treatment group was fed with basal diet containing Bacillus cereus PAS38 1×10⁶ CFU/g. Thymus and bursa of fabricius were taken from two groups of broilers at the age of 42 days, total RNA was extracted, differential gene library was constructed by SSH technology, and immune-related differential genes were screened. Then, we used siRNA to interfere with the expression of some differential genes in the original generation lymphocytes of broiler blood to detect the change of cytokines mRNA expression level. A total of 42 immune-related differentially expressed genes were screened, including 22 up-regulated genes and 20 down-regulated genes. When 7 differentially up-regulated genes associated with enhanced immune function were interfered with in lymphocytes, some immune-promoting cytokines were down-regulated. These results showed that Bacillus cereus PAS38 might up-regulate the expression of JCHAIN, PRDX1, CD3E, CDK6 and other genes in immune organs of broilers, thereby affecting the development of immune organs, the expression of various cytokines and the transduction of immune signals, improving the immune capacity of broilers.

Disc1 Carrier Mice Exhibit Alterations in Neural pIGF-1Rβ and Related Kinase Expression

Mutation of the disc1 gene underlies a broad range of developmental neuropsychiatric defects, including schizophrenia, depression, and bipolar disorder. The pathophysiological phenotypes linked with disc1 mutation are due to the truncation of the DISC1 primary protein structure. This leads to a defective post-synaptic scaffolding and kinase—GSK3β and Erk1/2—signaling. As a result, synaptic function and maintenance are significantly impaired in the disc1 mutant brain. Among several other pathways, GSK3β and Erk1/2 are involved in insulin-like growth factor 1 receptor (IGF-1Rβ) kinase signaling. Although disc1 mutation alters these kinases, it is unclear if the mutation impacts IGF-1R expression and activity in the brain. Here, we demonstrate that the expression of active IGF-1Rβ (pIGF-1Rβ) is altered in the hippocampus and prefrontal cortex (PFC) of disc1 mutant mice and vary with the dose of the mutation (homozygous and heterozygous). The expression of pIGF-1Rβ decreased significantly in 129S (hom, disc1^−/−) brains. In contrast, 129S:B6 (het, disc1^+/−) brains were characterized by an increase in pIGF-1Rβ when compared with the C57BL/6 (disc1^+/+) level. The decrease in pIGF-1Rβ level for the 129S brains was accompanied by the loss of Akt activity (S473 pAkt) and decreased Ser9 phosphorylation of GSK3β (increased basal GSK3β). Additionally, hippocampal and cortical pErk1/2 activity increased in the 129S hippocampus and cortex. Although 129S:B6 recorded alterations in pIGF-1Rβ-pAkt-GSK3β (like 129S), there was no observable change in pErk1/2 activity for the heterozygote (disc1^+/−) mutant. In addition to GSK3β inhibition, we conclude that pIGF-1R, pAkt, and pErk1/2 are potential targets in disc1^−/− mutant brain. On the other hand, pIGF-1R and pAkt can be further explored in disc1^+/− brain.

New Insights from IGF-IR Stimulating Activity Analyses: Pathological Considerations

Insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II) play a crucial factor in the growth, differentiation and survival of cells in health and disease. IGF-I and IGF-II primarily activate the IGF-I receptor (IGF-IR), which is present on the cell surface. Activation of the IGF-IR stimulates multiple pathways which finally results in multiple biological effects in a variety of tissues and cells. In addition, activation of the IGF-IR has been found to be essential for the growth of cancers. The conventional view in the past was that the IGF-IR was exclusively a tyrosine kinase receptor and that phosphorylation of tyrosine residues, after binding of IGF-I to the IGF-IR, started a cascade of post-receptor events. Recent research has shown that this view was too simplistic. It has been found that the IGF-IR also has kinase-independent functions and may even emit signals in the unoccupied state through some yet-to-be-defined non-canonical pathways. The IGF-IR may further form hybrids with the insulin receptors but also with receptor tyrosine kinases (RTKs) outside the insulin-IGF system. In addition, the IGF-IR has extensive cross-talk with many other receptor tyrosine kinases and their downstream effectors. Moreover, there is now emerging evidence that the IGF-IR utilizes parts of the G-protein coupled receptor (GPCR) pathways: the IGF-IR can be considered as a functional RTK/GPCR hybrid, which integrates the kinase signaling with some IGF-IR mediated canonical GPCR characteristics. Like the classical GPCRs the IGF-IR can also show homologous and heterologous desensitization. Recently, it has been found that after activation by a ligand, the IGF-IR may be translocated into the nucleus and function as a transcriptional cofactor. Thus, in recent years, it has become clear that the IGF-IR signaling pathways are much more complex than first thought. Therefore a big challenge for the (near) future will be how all the new knowledge about IGF-IR signaling can be translated into the clinical practice and improve diagnosis and treatment of diseases.

Nuclear localization and actions of the insulin-like growth factor 1 (IGF-1) system components: Transcriptional regulation and DNA damage response

Insulin-like growth factor (IGF) system stimulates growth, proliferation, and regulates differentiation of cells in a tissue-specific manner. It is composed of two insulin-like growth factors (IGF-1 and IGF-2), six insulin-like growth factor-binding proteins (IGFBPs), and two insulin-like growth factor receptors (IGF-1R and IGF-2R). IGF actions take place mostly through the activation of the plasma membrane-bound IGF-Rs by the circulating ligands (IGFs) released from the IGFBPs that stabilize their levels in the serum. This review focuses on the IGF-1 part of the system. The IGF-1 gene, which is expressed mainly in the liver as well as in other tissues, comprises six alternatively spliced exons that code for three protein isoforms (pro-IGF-1A, pro-IGF-1B, and pro-IGF-1C), which are processed to mature IGF-1 and E-peptides. The IGF-1R undergoes autophosphorylation, resulting in a signaling cascade involving numerous cytoplasmic proteins such as AKT and MAPKs, which regulate the expression of target genes. However, a more complex picture of the axis has recently emerged with all its components being translocated to the nuclear compartment. IGF-1R takes part in the regulation of gene expression by forming transcription complexes, modifying the activity of chromatin remodeling proteins, and participating in DNA damage tolerance mechanisms. Four IGFBPs contain a nuclear localization signal (NLS), which targets them to the nucleus, where they regulate gene expression (IGFBP-2, IGFBP-3, IGFBP-5, IGFBP-6) and DNA damage repair (IGFBP-3 and IGFBP-6). Last but not least, the IGF-1B isoform has been reported to be localized in the nuclear compartment. However, no specific molecular actions have been assigned to the nuclear pro-IGF-1B or its derivative EB peptide. Therefore, further studies are needed to shed light on their nuclear activity. These recently uncovered nuclear actions of different components of the IGF-1 axis are relevant in cancer cell biology and are discussed in this review.

Controlled Signaling-Insulin-Like Growth Factor Receptor Endocytosis and Presence at Intracellular Compartments

Ligand-induced activation of the IGF-1 receptor triggers plasma-membrane-derived signal transduction but also triggers receptor endocytosis, which was previously thought to limit signaling. However, it is becoming ever more clear that IGF-1R endocytosis and trafficking to specific subcellular locations can define specific signaling responses that are important for key biological processes in normal cells and cancer cells. In different cell types, specific cell adhesion receptors and associated proteins can regulate IGF-1R endocytosis and trafficking. Once internalized, the IGF-1R may be recycled, degraded or translocated to the intracellular membrane compartments of the Golgi apparatus or the nucleus. The IGF-1R is present in the Golgi apparatus of migratory cancer cells where its signaling contributes to aggressive cancer behaviors including cell migration. The IGF-1R is also found in the nucleus of certain cancer cells where it can regulate gene expression. Nuclear IGF-1R is associated with poor clinical outcomes. IGF-1R signaling has also been shown to support mitochondrial biogenesis and function, and IGF-1R inhibition causes mitochondrial dysfunction. How IGF-1R intracellular trafficking and compartmentalized signaling is controlled is still unknown. This is an important area for further study, particularly in cancer.

The nuclear translocation of insulin-like growth factor receptor and its significance in cancer cell survival

The nuclear translocation of insulin-like growth factor receptor type 1 (IGF-1R) has been documented in a variety of previous studies. The exact mechanism of this translocation, however, is still poorly understood. Furthermore, the functional role of IGF-1R in the nucleus shows promise of transcriptional control. This function is particularly important in cancer cells. Understanding this role may also give insights into cancer biology and treatment methods. Processes including SUMOylation and clathrin-mediated endocytosis are necessary for IGF-1R nuclear translocation to occur. The antiapoptotic qualities of IGF-1R likely contribute to its function in cancer cells. This review aims to synthesize the work on IGF-1R in order to propose a mechanism of translocation. Using this mechanism, new therapeutic targets can be proposed that hinder the role of IGF-1R in cancer metastasis.

Transcriptome Analysis Reveals New Insights into MdBAK1-Mediated Plant Growth in Malus domestica

BAK1 effects on plant stress responses have been well documented, but little is known regarding its effects on plant growth. In this study, we functionally characterized MdBAK1. Overexpressing MdBAK1 in Arabidopsis thaliana and apple trees promoted growth. Longitudinal stem cells were longer in transgenic plants than in wild-type plants. The size and number of cells and the area of the transverse stem were greater in the transgenic lines than in the wild-type plants. Moreover, transgenic A. thaliana and apple plants were more sensitive to an exogenous brassinosteroid. A transcriptome analysis of wild-type and transgenic apple revealed that MdBAK1 overexpression activated the brassinosteroid and ethylene signals, xylem production, and stress responses. Trend and Venn analyses indicated that carbohydrate, energy, and hormone metabolic activities were greater in transgenic plants during different periods. Moreover, a weighted gene coexpression network analysis proved that carbohydrate, hormone, and xylem metabolism as well as cell growth may be critical for MdBAK1-mediated apple tree growth and development. Compared with the corresponding levels in wild-type plants, the endogenous brassinosteroid, cytokinin, starch, sucrose, trehalose, glucose, fructose, and total sugar contents were considerably different in transgenic plants. Our results imply that MdBAK1 helps to regulate the growth of apple tree through the above-mentioned pathways. These findings provide new information regarding the effects of MdBAK1 onplant growth and development.

Melatonin disturbs SUMOylation-mediated crosstalk between c-Myc and nestin via MT1 activation and promotes the sensitivity of paclitaxel in brain cancer stem cells

Here the underlying antitumor mechanism of melatonin and its potency as a sensitizer of paclitaxel was investigated in X02 cancer stem cells. Melatonin suppressed sphere formation and induced G2/M arrest in X02 cells expressing nestin, CD133, CXCR4, and SOX-2 as biomarkers of stemness. Furthermore, melatonin reduced the expression of CDK2, CDK4, cyclin D1, cyclin E, and c-Myc and upregulated cyclin B1 in X02 cells. Notably, genes of c-Myc related mRNAs were differentially expressed in melatonin-treated X02 cells by microarray analysis. Consistently, melatonin reduced the expression of c-Myc at mRNA and protein levels, which was blocked by MG132. Of note, overexpression of c-Myc increased the expression of nestin, while overexpression of nestin enhanced c-Myc through crosstalk despite different locations, nucleus, and cytoplasm. Interestingly, melatonin attenuated small ubiquitin-related modifier-1 (SUMO-1) more than SUMO-2 or SUMO-3 and disturbed nuclear translocation of nestin for direct binding to c-Myc by SUMOylation of SUMO-1 protein by immunofluorescence and immunoprecipitation. Also, melatonin reduced trimethylated histone H3K4me3 and H3K36me3 more than dimethylation in X02 cells by Western blotting and chromatin immunoprecipitation assay. Notably, melatonin upregulated MT1, not MT2, in X02 cells and melatonin receptor inhibitor luzindole blocked the ability of melatonin to decrease the expression of nestin, p-c-Myc(S62), and c-Myc. Furthermore, melatonin promoted cytotoxicity, sub-G1 accumulation, and apoptotic body formation by Paclitaxcel in X02 cells. Taken together, these findings suggest that melatonin inhibits stemness via suppression of c-Myc, nestin, and histone methylation via MT1 activation and promotes anticancer effect of Paclitaxcel in brain cancer stem cells.

Mutual regulation between IGF-1R and IGFBP-3 in human corneal epithelial cells

The insulin-like growth factor type 1 receptor (IGF-1R) is part of the receptor tyrosine kinase superfamily. The activation of IGF-1R regulates several key signaling pathways responsible for maintaining cellular homeostasis, including survival, growth, and proliferation. In addition to mediating signal transduction at the plasma membrane, in serum-based models, IGF-1R undergoes SUMOylation by SUMO 1 and translocates to the nucleus in response to IGF-1. In corneal epithelial cells grown in serum-free culture, however, IGF-1R has been shown to accumulate in the nucleus independent of IGF-1. In this study, we report that the insulin-like growth factor binding protein-3 (IGFBP-3) mediates nuclear translocation of IGF-1R in response to growth factor withdrawal. This occurs via SUMOylation by SUMO 2/3. Further, IGF-1R and IGFBP-3 undergo reciprocal regulation independent of PI3k/Akt signaling. Thus, under healthy growth conditions, IGFBP-3 functions as a gatekeeper to arrest the cell cycle in G0/G1, but does not alter mitochondrial respiration in cultured cells. When stressed, IGFBP-3 functions as a caretaker to maintain levels of IGF-1R in the nucleus. These results demonstrate mutual regulation between IGF-1R and IGFBP-3 to maintain cell survival under stress. This is the first study to show a direct relationship between IGF-1R and IGFBP-3 in the maintenance of corneal epithelial homeostasis.

Characterization of an activating R1353H insulin-like growth factor 1 receptor variant in a male with extreme tall height

OBJECTIVE

The insulin-like growth factor1 receptor (IGF1R) is important in growth and development, and inactivating IGF1R mutations cause short stature and relatively high levels of serum IGF-I. We identified an unclassified IGF1R^R1353H variant in a male with extreme tall height, very low levels of serum IGF-I and delayed and prolonged growth spurt. The index case's mother and three sons all carried the variant, but so far only the eldest son (age 18 years) presented with tall height. We hypothesized that the variant could constitute an activating mutation.

DESIGN

The IGF1R^R1353H variant was investigated in Igf1r^-/- mouse embryonic fibroblasts (R-cells) by cell cycle, colony formation and transcriptome analyses.

RESULTS

The IGF1R^R1353H (R-1353) exhibited significantly increased cell proliferation, G1-S progression and colony formation in soft agar. RNA sequencing identified 195 differentially expressed genes between R-WT and R-1353 (adjusted P < 1E-100). Most genes were upregulated in R-1353, including the gene encoding the androgen receptor (AR). Gene expression profiling showed the most significant enrichment in extracellular matrix organization (P = 2.76E-7), collagen biosynthesis (P = 1.21E-5) and cell adhesion (P = 7.38E-5). Retrospective biochemical analysis of the index case revealed decreased testosterone and sex hormone-binding globulin levels, whereas LH and FSH were within normal ranges. This profile suggests an increased sensitivity to androgen, which is compatible with the enhanced expression of Ar in R-1353 cells.

CONCLUSIONS

Our findings suggest that R1353H constitutes an activating IGF1R variant. The possible deregulation of collagen turnover and increased androgen sensitivity implicates an association to tall phenotype in male carriers.

MiR-99b-5p and miR-203a-3p Function as Tumor Suppressors by Targeting IGF-1R in Gastric Cancer

MicroRNAs (miRNAs) have been explored in many critical cellular processes, including proliferation and apoptosis. The purpose of this study was to detect the biological function and regulation of miR-99b-5p and miR-203a-3p in gastric cancer (GC). Here, we demonstrated that miR-99b-5p/203a-3p were downregulated in both GC tissues and cell lines. MiR-99b-5p/203a-3p overexpression reduced GC cell proliferation and cell cycle progression in vitro. Notably, we combined bioinformatics tools with biological validation assays to demonstrate that insulin-like growth factor 1 receptor (IGF-1R) is a direct co-target and functional mediator of miR-99b-5p/203a-3p in GC cells. Mechanistically, the AKT pathway, which is downstream of IGF-1R, is essential for the functional roles of miR-99b-5p/203a-3p in GC cells. Taken together, our data revealed that IGF-1R is a direct co-target of miR-99b-5p/203a-3p, and miR-99b-5p/203a-3p may function as tumor suppressive miRNAs by negatively regulating IGF-1R expression in GC cells.

Nuclear IGF1R Interacts with Regulatory Regions of Chromatin to Promote RNA Polymerase II Recruitment and Gene Expression Associated with Advanced Tumor Stage

Internalization of ligand-activated type I IGF receptor (IGF1R) is followed by recycling to the plasma membrane, degradation or nuclear translocation. Nuclear IGF1R reportedly associates with clinical response to IGF1R inhibitory drugs, yet its role in the nucleus is poorly characterized. Here, we investigated the significance of nuclear IGF1R in clinical cancers and cell line models. In prostate cancers, IGF1R was predominantly membrane localized in benign glands, while malignant epithelium contained prominent internalized (nuclear/cytoplasmic) IGF1R, and nuclear IGF1R associated significantly with advanced tumor stage. Using ChIP-seq to assess global chromatin occupancy, we identified IGF1R-binding sites at or near transcription start sites of genes including JUN and FAM21, most sites coinciding with occupancy by RNA polymerase II (RNAPol2) and histone marks of active enhancers/promoters. IGF1R was inducibly recruited to chromatin, directly binding DNA and interacting with RNAPol2 to upregulate expression of JUN and FAM21, shown to mediate tumor cell survival and IGF-induced migration. IGF1 also enriched RNAPol2 on promoters containing IGF1R-binding sites. These functions were inhibited by IGF1/II-neutralizing antibody xentuzumab (BI 836845), or by blocking receptor internalization. We detected IGF1R on JUN and FAM21 promoters in fresh prostate cancers that contained abundant nuclear IGF1R, with evidence of correlation between nuclear IGF1R content and JUN expression in malignant prostatic epithelium. Taken together, these data reveal previously unrecognized molecular mechanisms through which IGFs promote tumorigenesis, with implications for therapeutic evaluation of anti-IGF drugs.Significance: These findings reveal a noncanonical nuclear role for IGF1R in tumorigenesis, with implications for therapeutic evaluation of IGF inhibitory drugs. Cancer Res; 78(13); 3497-509. ©2018 AACR.

Nuclear translocation of IGF1R by intracellular amphiregulin contributes to the resistance of lung tumour cells to EGFR-TKI

Many Receptor Tyrosine Kinases translocate from the cell surface to the nucleus in normal and pathological conditions, including cancer. Here we report the nuclear expression of insulin-like growth factor-1 receptor (IGF1R) in primary human lung tumours. Using lung cancer cell lines and lung tumour xenografts, we demonstrate that the epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) gefitinib induces the nuclear accumulation of IGF1R in mucinous lung adenocarcinoma by a mechanism involving the intracellular re-localization of the growth factor amphiregulin. Amphiregulin allows the binding of IGF1R to importin-β1 and promotes its nuclear transport. The nuclear accumulation of IGF1R by amphiregulin induces cell cycle arrest through p21^WAF1/CIP1 upregulation, and prevents the induction of apoptosis in response to gefitinib. These results identify amphiregulin as the first nuclear localization signal-containing protein that interacts with IGF1R and allows its nuclear translocation. Furthermore they indicate that nuclear expression of IGF1R contributes to EGFR-TKI resistance in lung cancer.

The interaction of IGF-1/IGF-1R and hydrogen sulfide on the proliferation of mouse primary vascular smooth muscle cells

Hydrogen sulfide (H₂S) is mostly produced by cystathionine-gamma-lyase (CSE) in vascular system and it inhibits the proliferation of vascular smooth muscle cells (SMCs). Insulin-like growth factor-1 (IGF-1), via its receptor (IGF-1R), exerts multiple physiological and pathophysiological effects on the vasculature, including stimulating SMC proliferation and migration, and inhibiting SMC apoptosis. Since H₂S and IGF-1/IGF-1R have opposite effects on SMC proliferation, it becomes imperative to better understand the interaction of these two signaling mechanisms on SMC proliferation. SMCs isolated from small mesenteric arteries of CSE knockout (KO) and wild-type (WT) mice were used in the present study. The effects of IGF-1 and H₂S on SMC proliferation were evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and bromodeoxyuridine (BrdU) assays. Protein expression was determined by western blot, and H₂S-induced protein S-sulfhydration was assessed with a modified biotin switch assay. We found that IGF-1 dose-dependently increased the proliferation of both WT-SMCs and KO-SMCs, and this effect was more significant in KO-SMCs. Supplement of sodium hydrosulfide (NaHS) inhibited IGF-1-induced cell proliferation, while this effect was abolished by blocking IGF-1/IGF-1R signaling with picropodophyllin (PPP) or knocking out of the expression of IGF-1R. H₂S significantly down-regulates the expression of IGF-1R, stimulates IGF-1R S-sulfhydration, and attenuates the binding of IGF-1 with IGF-1R. This study provides novel insight on the involvement of IGF-1/IGF-1R in H₂S-inhibited SMC proliferation and suggests H₂S-based innovative treatment strategies for proliferative cardiovascular diseases such as atherosclerosis.

Diagnosis, prognosis and bioinformatics analysis of lncRNAs in hepatocellular carcinoma

This study aims to comprehensively analyze the diagnosis and prognosis of lncRNAs in hepatocellular carcinoma (HCC). From the Gene Expression Omnibus database, we screened out and analyzed the differently expressed lncRNAs and related mRNAs using bioinformatics methods. The expressions of lncRNAs were validated in tumor tissues, cell lines and the Cancer Genome Atlas database. At the same time, we also conducted an exploratory analysis on the diagnostic and prognostic ability of lncRNAs in HCC. In this study, we found that most of the targeted mRNAs promote the biological process of cell division, cellular component of nucleoplasm, molecular function of protein binding, which were significantly associated with 12 KEGG pathways. LncRNA CRNDE and LINC01419 also had significant diagnostic value in HCC. In particular, the sensitivity, specificity and area under the curve of CRNDE were 71.0%, 87.1% and 0.701 (95% CI: 0.543-0.860), respectively. In addition, the high expression of CRNDE and GBAP1 predicated poor prognosis, while the high expression of LINC01093 suggested the opposite outcome. Through the comprehensive analysis of lncRNAs, it provided an important reference for the early diagnosis, prognosis evaluation, pathogenesis and targeted therapy of HCC.

Nuclear insulin-like growth factor-1 receptor (IGF1R) displays proliferative and regulatory activities in non-malignant cells

The insulin-like growth factor-1 receptor (IGF1R) mediates the biological actions of IGF1 and IGF2. The IGF1R is involved in both physiological and pathological activities and is usually overexpressed in most types of cancer. In addition to its classical mechanism of action, recent evidence has shown a nuclear presence of IGF1R, associated with novel genomic/transcriptional types of activities. The present study was aimed at evaluating the hypothesis that nuclear IGF1R localization is not restricted to cancer cells and might constitute a novel physiologically relevant regulatory mechanism. Our data shows that nuclear translocation takes place in a wide array of cells, including normal diploid fibroblasts. In addition, we provide evidence for a synergistic effect of a nuclear translocation blocker along with selective IGF1R inhibitors in terms of decreasing cell proliferation. Given the important role of the IGF1R in mitogenesis, the present results may be of translational relevance in cancer research. In conclusion, results are consistent with the concept that nuclear IGF1R fulfills important physiological and pathological roles.

Nuclear insulin-like growth factor 1 receptor phosphorylates proliferating cell nuclear antigen and rescues stalled replication forks after DNA damage

We have previously shown that the insulin-like growth factor 1 receptor (IGF-1R) translocates to the cell nucleus, where it binds to enhancer-like regions and increases gene transcription. Further studies have demonstrated that nuclear IGF-1R (nIGF-1R) physically and functionally interacts with some nuclear proteins, i.e. the lymphoid enhancer-binding factor 1 (Lef1), histone H3, and Brahma-related gene-1 proteins. In this study, we identified the proliferating cell nuclear antigen (PCNA) as a nIGF-1R-binding partner. PCNA is a pivotal component of the replication fork machinery and a main regulator of the DNA damage tolerance (DDT) pathway. We found that IGF-1R interacts with and phosphorylates PCNA in human embryonic stem cells and other cell lines. In vitro MS analysis of PCNA co-incubated with the IGF-1R kinase indicated tyrosine residues 60, 133, and 250 in PCNA as IGF-1R targets, and PCNA phosphorylation was followed by mono- and polyubiquitination. Co-immunoprecipitation experiments suggested that these ubiquitination events may be mediated by DDT-dependent E2/E3 ligases (e.g. RAD18 and SHPRH/HLTF). Absence of IGF-1R or mutation of Tyr-60, Tyr-133, or Tyr-250 in PCNA abrogated its ubiquitination. Unlike in cells expressing IGF-1R, externally induced DNA damage in IGF-1R-negative cells caused G₁ cell cycle arrest and S phase fork stalling. Taken together, our results suggest a role of IGF-1R in DDT.

SUMO-modified insulin-like growth factor 1 receptor (IGF-1R) increases cell cycle progression and cell proliferation

Increasing number of studies have shown nuclear localization of the insulin‐like growth factor 1 receptor (nIGF‐1R) in tumor cells and its links to adverse clinical outcome in various cancers. Any obvious cell physiological roles of nIGF‐1R have, however, still not been disclosed. Previously, we reported that IGF‐1R translocates to cell nucleus and modulates gene expression by binding to enhancers, provided that the receptor is SUMOylated. In this study, we constructed stable transfectants of wild type IGF1R (WT) and triple‐SUMO‐site‐mutated IGF1R (TSM) using igf1r knockout mouse fibroblasts (R‐). Cell clones (R‐WT and R‐TSM) expressing equal amounts of IGF‐1R were selected for experiments. Phosphorylation of IGF‐1R, Akt, and Erk upon IGF‐1 stimulation was equal in R‐WT and R‐TSM. WT was confirmed to enter nuclei. TSM did also undergo nuclear translocation, although to a lesser extent. This may be explained by that TSM heterodimerizes with insulin receptor, which is known to translocate to cell nuclei. R‐WT proliferated substantially faster than R‐TSM, which did not differ significantly from the empty vector control. Upon IGF‐1 stimulation G1‐S‐phase progression of R‐WT increased from 12 to 38%, compared to 13 to 20% of R‐TSM. The G1‐S progression of R‐WT correlated with increased expression of cyclin D1, A, and CDK2, as well as downregulation of p27. This suggests that SUMO‐IGF‐1R affects upstream mechanisms that control and coordinate expression of cell cycle regulators. Further studies to identify such SUMO‐IGF‐1R dependent mechanisms seem important.