Insulin-like growth factor 1 (IGF-1)-induced twist expression is involved in the anti-apoptotic effects of the IGF-1 receptor

Twist is required for muscle development of the adult legs in Henosepilachna vigintioctopunctata

Although muscle development has been widely studied in Drosophila melanogaster, it was a great challenge to apply to developmental processes of other insect muscles. This study was focused on the functional characterization of a basic helix-loop-helix transcription factor gene twist in an herbivorous ladybird Henosepilachna vigintioctopunctata. Its transcript (Hvtwist) levels were detected in all developmental stages. RNA interference (RNAi)-aided knockdown of Hvtwist at the penultimate larval instar stage impaired pupation, and caused a deformed adult in the legs. The tarsi were malformed and did not support the bodies in an upright position. The climbing ability was impaired. Moreover, around 50% of the impaired adults had a malformed elytrum. In addition, they consumed less foliage and did not lay eggs. A hematoxylin-eosin staining of the leg demonstrated that the tibial extensor (TE) and the tibial flexor (TF) muscles were originated from the femurs while levator and depressor muscles of the tarsus (TL and TD) were located in the tibia in the control adults, in which tarsal segments were devoid of muscles. RNAi treatment specific to Hvtwist expression markedly impaired TE and TF muscles in the femurs, and prevented the development of TL and TD muscles in the tibia. Therefore, our findings demonstrate Twist plays a vital role in the myogenesis in H. vigintioctopunctata adult legs.

Long non-coding RNAs as the critical regulators of PI3K/AKT, TGF-β, and MAPK signaling pathways during breast tumor progression

Breast cancer (BC) as one of the most common causes of human deaths among women, is always considered one of the global health challenges. Despite various advances in diagnostic and therapeutic methods, a significant percentage of BC patients have a poor prognosis due to the lack of therapeutic response. Therefore, investigating the molecular mechanisms involved in BC progression can improve the therapeutic and diagnostic strategies in these patients. Cytokine and growth factor-dependent signaling pathways play a key role during BC progression. In addition to cytokines and growth factors, long non-coding RNAs (lncRNAs) have also important roles in regulation of such signaling pathways. Therefore, in the present review we discussed the role of lncRNAs in regulation of PI3K/AKT, MAPK, and TGF-β signaling pathways in breast tumor cells. It has been shown that lncRNAs mainly have an oncogenic role through the promotion of these signaling pathways in BC. This review can be an effective step in introducing the lncRNAs inhibition as a probable therapeutic strategy to reduce tumor growth by suppression of PI3K/AKT, MAPK, and TGF-β signaling pathways in BC patients. In addition, considering the oncogenic role and increased levels of lncRNAs expressions in majority of the breast tumors, lncRNAs can be also considered as the reliable diagnostic markers in BC patients.

Potential Pathogenic Impact of Cow’s Milk Consumption and Bovine Milk-Derived Exosomal MicroRNAs in Diffuse Large B-Cell Lymphoma

Epidemiological evidence supports an association between cow’s milk consumption and the risk of diffuse large B-cell lymphoma (DLBCL), the most common non-Hodgkin lymphoma worldwide. This narrative review intends to elucidate the potential impact of milk-related agents, predominantly milk-derived exosomes (MDEs) and their microRNAs (miRs) in lymphomagenesis. Upregulation of PI3K-AKT-mTORC1 signaling is a common feature of DLBCL. Increased expression of B cell lymphoma 6 (BCL6) and suppression of B lymphocyte-induced maturation protein 1 (BLIMP1)/PR domain-containing protein 1 (PRDM1) are crucial pathological deviations in DLBCL. Translational evidence indicates that during the breastfeeding period, human MDE miRs support B cell proliferation via epigenetic upregulation of BCL6 (via miR-148a-3p-mediated suppression of DNA methyltransferase 1 (DNMT1) and miR-155-5p/miR-29b-5p-mediated suppression of activation-induced cytidine deaminase (AICDA) and suppression of BLIMP1 (via MDE let-7-5p/miR-125b-5p-targeting of PRDM1). After weaning with the physiological termination of MDE miR signaling, the infant’s BCL6 expression and B cell proliferation declines, whereas BLIMP1-mediated B cell maturation for adequate own antibody production rises. Because human and bovine MDE miRs share identical nucleotide sequences, the consumption of pasteurized cow’s milk in adults with the continued transfer of bioactive bovine MDE miRs may de-differentiate B cells back to the neonatal “proliferation-dominated” B cell phenotype maintaining an increased BLC6/BLIMP1 ratio. Persistent milk-induced epigenetic dysregulation of BCL6 and BLIMP1 expression may thus represent a novel driving mechanism in B cell lymphomagenesis. Bovine MDEs and their miR cargo have to be considered potential pathogens that should be removed from the human food chain.

Anoikis in phenotypic reprogramming of the prostate tumor microenvironment

Prostate cancer is one of the most common malignancies in males wherein 1 in 8 men are diagnosed with this disease in their lifetime. The urgency to find novel therapeutic interventions is associated with high treatment resistance and mortality rates associated with castration-resistant prostate cancer. Anoikis is an apoptotic phenomenon for normal epithelial or endothelial cells that have lost their attachment to the extracellular matrix (ECM). Tumor cells that lose their connection to the ECM can die via apoptosis or survive via anoikis resistance and thus escaping to distant organs for metastatic progression. This review discusses the recent advances made in our understanding of the signaling effectors of anoikis in prostate cancer and the approaches to translate these mechanistic insights into therapeutic benefits for reducing lethal disease outcomes (by overcoming anoikis resistance). The prostate tumor microenvironment is a highly dynamic landscape wherein the balance between androgen signaling, cell lineage changes, epithelial-mesenchymal transition (EMT), extracellular matrix interactions, actin cytoskeleton remodeling as well as metabolic changes, confer anoikis resistance and metastatic spread. Thus, these mechanisms also offer unique molecular treatment signatures, exploitation of which can prime prostate tumors to anoikis induction with a high translational significance.

IGF-Binding Proteins and Their Proteolysis as a Mechanism of Regulated IGF Release in the Nervous Tissue

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) play a key role in the maintenance of the nervous tissue viability. IGF-1 and IGF-2 exhibit the neuroprotective effects by stimulating migration and proliferation of nervous cells, activating cellular metabolism, inducing regeneration of damaged cells, and regulating various stages of prenatal and postnatal development of the nervous system. The availability of IGFs for the cells is controlled via their interaction with the IGF-binding proteins (IGFBPs) that inhibit their activity. On the contrary, the cleavage of IGFBPs by specific proteases leads to the IGF release and activation of its cellular effects. The viability of neurons in the nervous tissue is controlled by a complex system of trophic factors secreted by auxiliary glial cells. The main source of IGF for the neurons are astrocytes. IGFs can accumulate as an extracellular free ligand near the neuronal membranes as a result of proteolytic degradation of IGFBPs by proteases secreted by astrocytes. This mechanism promotes interaction of IGFs with their genuine receptors and triggers intracellular signaling cascades. Therefore, the release of IGF by proteolytic cleavage of IGFBPs is an important mechanism of neuronal protection. This review summarizes the published data on the role of IGFs and IGFBPs as the key players in the neuroprotective regulation with a special focus on the specific proteolysis of IGFBPs as a mechanism for the regulation of IGF bioavailability and viability of neurons.

HULC targets the IGF1R-PI3K-AKT axis in trans to promote breast cancer metastasis and cisplatin resistance

Insulin-like growth factor I receptor (IGF1R) is frequently upregulated in breast cancer. Due to its intrinsic tyrosine kinase activity, aberrant activation of the IGF1R signaling axis may enhance tumor cell proliferation and cancer stemness, causing tumor relapse, metastasis and resistance to chemotherapy. We utilized a chromatin RNA in situ reverse transcription (CRIST) approach to characterize molecular factors that regulate the IGF1R network. We identified lncRNA HULC (Highly Upregulated in Liver Cancer) as a key trans-regulator of IGF1R in breast cancer cells. Loss of HULC suppressed the expression of IGF1R and the activation of its downstream PI3K/AKT pathway, while HULC overexpression activated the axis in breast cancer cells. Using a transcription-associated trap (RAT) assay, we demonstrated that HULC functioned as a nuclear lncRNA and epigenetically activated IGF1R by directly binding to the intragenic regulatory elements of the gene, orchestrating intrachromosomal interactions, and promoting histone H3K9 acetylation. The activated HULC-IGF1R/PI3K/AKT pathway mediated tumor resistance to cisplatin through the increased expression of cancer stemness markers, including NANOG, SOX2, OCT4, CD44 and ALDH1A1. In immunodeficient mice, stimulation of the HULC-IGF1R pathway promoted tumor metastasis. These data suggest that HULC may be a new epigenetic target for IGF1R axis-targeted therapeutic intervention.

Bisphenol A-induced DNA damages promote to lymphoma progression in human lymphoblastoid cells through aberrant CTNNB1 signaling pathway

Lymphoma is a group of blood cancers that develop from the immune system, and one of the main risk factors is associated with exposure to environmental chemicals. Bisphenol A (BPA) is a common chemical used in the manufacture of materials in polycarbonate and epoxy plastic products and can interfere with the immune system. BPA is considered to possibly induce lymphoma development by affecting the immune system, but its potential mechanisms have not been well established. This study performed a gene-network analysis of microarray data sets in human lymphoma tissues as well as in human cells with BPA exposure to explore module genes and construct the potential pathway for lymphomagenesis in response to BPA. This study provided evidence that BPA exposure resulted in disrupted cell cycle and DNA damage by activating CTNNB1, the initiator of the aberrant constructed CTNNB1-NFKB1-AR-IGF1-TWIST1 pathway, which may potentially lead to lymphomagenesis.

MAML1 promotes ESCC aggressiveness through upregulation of EMT marker TWIST1

BACKGROUND

Mastermind-like 1 (MAML1) is the main transcriptional co-activator of Notch signaling pathway. It plays essential roles in several pathways including MEF2C, p53, Nf-кB and Wnt/β-catenin. TWIST1 is known as a regulator of epithelial mesenchymal transition (EMT), which is considered as a primary step in promotion of tumor cell metastasis. Since concomitant expression of these genes was observed in tumors, our aim in this study was to elucidate the linkage between MAML1 and TWIST1 co-overexpression in esophageal squamous cell carcinoma (ESCC).

RESULTS

While MAML1 silencing significantly down-regulated TWIST1, its ectopic expression up-regulated TWIST1 expression in both mRNA and protein levels in KYSE-30 cells. Expression of mesenchymal markers was increased significantly after MAML1 and TWIST1 ectopic expression, while epithelial markers expression was significantly decreased after silencing of both genes. Concomitant protein expression of MAML1 and TWIST1 was significantly observed in ESCC patients. Enforced expression of TWIST1 had no impact on MAML1 gene expression in KYSE-30 cells.

CONCLUSION

The results clearly suggest transcriptional regulation of TWIST1 by MAML1 transcription factor in ESCC cells KYSE-30. Since TWIST1 is known as an EMT inducing marker, our results may revealed the mastermind behind TWIST1 function and introduced MAML1 as an upstream master regulator of TWIST1 and EMT in KYSE-30 cells.

Molecular Insights Into the Relationship Between Autoimmune Thyroid Diseases and Breast Cancer: A Critical Perspective on Autoimmunity and ER Stress

The etiopathologies behind autoimmune thyroid diseases (AITDs) unravel misbehavior of immune components leading to the corruption of immune homeostasis where thyroid autoantigens turn foe to the self. In AITDs lymphocytic infiltration in the thyroid shows up a deranged immune system charging the follicular cells of the thyroid gland (thyrocytes) leading to the condition of either hyperthyroidism or hypothyroidism. The inflammation in AITDs consistently associate with ER function due to which disturbances in the ER protein homeostasis leads to unfolded protein response (UPR) that promotes pathogenesis of autoimmunity. The roles of ER stress in the instantaneous downregulation of MHC class I molecules on thyrocytes and the relevance of IFN γ in the pathogenesis of AITD has been well-documented. Thyroglobulin being the major target of autoantibodies in most of the AITDs is because of its unusual processing in the ER. Autoimmune disorders display a conglomeration of ER stress-induced UPR activated molecules. Several epidemiological data highlight the preponderance of AITDs in women as well as its concurrence with breast cancer. Both being an active glandular system displaying endocrine activity, thyroid as well as breast tissue show various commonalities in the expression pattern of heterogenous molecules that not only participate in the normal functioning but at the same time share the blame during disease establishment. Studies on the development and progression of breast carcinoma display a deranged and uncontrolled immune response, which is meticulously exploited during tumor metastasis. The molecular crosstalks between AITDs and breast tumor microenvironment rely on active participation of immune cells. The induction of ER stress by Tunicamycin advocates to provide a model for cancer therapy by intervening glycosylation. Therefore, this review attempts to showcase the molecules that are involved in feeding up the relationship between breast carcinoma and AITDs.

Nanoparticle Delivery of TWIST Small Interfering RNA and Anticancer Drugs: A Therapeutic Approach for Combating Cancer

Breast and ovarian cancer are the leading cause of cancer-related deaths in women in the United States with over 232,000 new Breast Cancer (BC) diagnoses expected in 2018 and almost 40,000 deaths and an estimated 239,000 new ovarian cancer (OC) cases and 152,000 deaths worldwide annually. OC is the most lethal gynecologic malignancy. This high mortality rate is due to tumor recurrence and metastasis, primarily caused by chemoresistant cancer stem-like cells (CSCs). Triple Negative Breast Cancer (TNBC) patients also become resistant to chemotherapy due to recurrence of CSCs. Currently, no ovarian or breast cancer therapies target CSC specifically. TWIST is overexpressed in the majority of chemoresistant cancers resulting in a low survival rate. Our long-term goal is to develop novel treatments for women with ovarian and breast cancer, specifically treatments that sensitize chemoresistant tumors. Despite successful initial surgery and chemotherapy, over 70% of advanced EOC will recur, and only 15-30% of recurrent disease will respond to chemotherapy (Cortez et al., 2017; Berezhnaya, 2010; Jackson et al., 2015). Moreover, drug resistance causes treatment failure in over 90% of patients with metastatic disease (Solmaz et al., 2015). Thus, recurrent metastatic disease is a major clinical challenge without effective therapy. One of the major challenges in the treatment of breast cancer is the presence of a subpopulation of cancer cells that are chemoresistant (CRC) and metastatic. Given that metastasis is the driving force behind mortality for breast and ovarian cancer patients, it is essential to identify the characteristics of these aberrant cancer cells that allow them to spread to distant sites in the body and develop into metastatic tumors. Understanding the metastatic mechanisms driving cancer cell dispersal will open the door to developing novel therapies that prevent metastasis and improve long-term outcomes for patients. In this chapter we assess the feasibility of targeting the Twist and EMT signaling pathways in breast and ovarian cancer. Additional discussions of the pathways that mediate epithelial-mesenchymal transition (EMT), a process that can give rise to chemoresistance. We review potential treatment strategies for targeting EMT and drug resistance as well as the problems that may arise with these targeted delivery therapeutic approaches. Finally, we examine recent advances in the field, including cancer stem cell targeted nanoparticle delivery and small interference RNA (siRNA) technology, and discuss the impact that these approaches may have on translating much needed therapeutic approaches into the clinic, for the benefit of patients battling this devastating disease.

Challenges in Orphan Drug Development: Identification of Effective Therapy for Thyroid-Associated Ophthalmopathy

Thyroid-associated ophthalmopathy (TAO), the ocular manifestation of Graves' disease, is a process in which orbital connective tissues and extraocular muscles undergo inflammation and remodeling. The condition seems to result from autoimmune responses to antigens shared by the thyroid and orbit. The thyrotropin receptor (TSHR), expressed at low levels in orbital tissues, is a leading candidate antigen. Recent evidence suggests that another protein, the insulin-like growth factor-I receptor (IGF-IR), is overexpressed in TAO, and antibodies against IGF-IR have been detected in patients with the disease. Furthermore, TSHR and IGF-IR form a physical and functional complex, and signaling initiated at TSHR requires IGF-IR activity. Identification of therapy for this rare disease has proven challenging and currently relies on nonspecific and inadequate agents, thus representing an important unmet need. A recently completed therapeutic trial suggests that inhibiting IGF-IR activity with a monoclonal antibody may be an effective and safe treatment for active TAO.

Gamma synuclein is a novel Twist1 target that promotes TGF-β-induced cancer cell migration and invasion

Transforming growth factor β (TGF-β) is critical for embryonic development, adult tissue homeostasis, and tumor progression. TGF-β suppresses tumors at early stage, but promotes metastasis at later stage through oncogenes such as Twist1. Gamma-synuclein (SNCG) is overexpressed in a variety of invasive and metastatic cancer. Here, we show that TGF-β induces SNCG expression by Smad-Twist1 axis, thus promoting TGF-β- and Twist1-induced cancer cell migration and invasion. We identify multiple Twist1-binding sites (E-boxes) in SNCG promoter. Chromatin immunoprecipitation and luciferase assays confirm the binding of Twist1 to the E-boxes of SNCG promoter sequence (−129/−1026 bp). Importantly, the Twist1-binding site close to the transcription initiation site is critical for the upregulation of SNCG expression by TGF-β and Twist1. Mutations of Twist1 motif on the SNCG promoter constructs markedly reduces the promoter activity. We further show that TGF-β induces Twist1 expression through Smad thereby enhancing the binding of Twist1 to SNCG promoter, upregulating SNCG promoter activity and increasing SNCG expression. SNCG knockdown abrogates TGF-β- or Twist1-induced cancer cell migration and invasion. Finally, SNCG knockdown inhibits the promotion of cancer metastasis by Twist1. Together, our data demonstrate that SNCG is a novel target of TGF-β-Smad-Twist1 axis and a mediator of Twist1-induced cancer metastasis.

IGF-IR signaling in epithelial to mesenchymal transition and targeting IGF-IR therapy: overview and new insights

The insulin-like growth factor-I (IGF-I) signaling induces epithelial to mesenchymal transition (EMT) program and contributes to metastasis and drug resistance in several subtypes of tumors. In preclinical studies, targeting of the insulin-like growth factor-I receptor (IGF-IR) showed promising anti-tumor effects. Unfortunately, high expectations for anti-IGF-IR therapy encountered challenge and disappointment in numerous clinical trials. This review summarizes the regulation of EMT by IGF-I/IGF-IR signaling pathway and drug resistance mechanisms of targeting IGF-IR therapy. Most importantly, we address several factors in the regulation of IGF-I/IGF-IR-associated EMT progression that may be potential predictive biomarkers in targeted therapy.

Adeno-associated virus gene therapy vector scAAVIGF-I for transduction of equine articular chondrocytes and RNA-seq analysis

OBJECTIVE

IGF-I is one of several anabolic factors being investigated for the treatment of osteoarthritis (OA). Due to the short biological half-life, extended administration is required for more robust cartilage healing. Here we create a self-complimentary adeno-associated virus (AAV) gene therapy vector utilizing the transgene for IGF-I.

DESIGN

Various biochemical assays were performed to investigate the cellular response to scAAVIGF-I treatment vs an scAAVGFP positive transduction control and a negative for transduction control culture. RNA-sequencing analysis was also performed to establish a differential regulation profile of scAAVIGF-I transduced chondrocytes.

RESULTS

Biochemical analyses indicated an average media IGF-I concentration of 608 ng/ml in the scAAVIGF-I transduced chondrocytes. This increase in IGF-I led to increased expression of collagen type II and aggrecan and increased protein concentrations of cellular collagen type II and media glycosaminoglycan vs both controls. RNA-seq revealed a global regulatory pattern consisting of 113 differentially regulated GO categories including those for chondrocyte and cartilage development and regulation of apoptosis.

CONCLUSIONS

This research substantiates that scAAVIGF-I gene therapy vector increased production of IGF-I to clinically relevant levels with a biological response by chondrocytes conducive to increased cartilage healing. The RNA-seq further established a set of differentially expressed genes and gene ontologies induced by the scAAVIGF-I vector while controlling for AAV infection. This dataset provides a static representation of the cellular transcriptome that, while only consisting of one time point, will allow for further gene expression analyses to compare additional cartilage healing therapeutics or a transient cellular response.

MyoD transcription factor induces myogenesis by inhibiting Twist-1 through miR-206

Twist-1 is mostly expressed during development and has been previously shown to control myogenesis. Because its regulation in muscle has not been fully exploited, the aim of this project was to identify micro (mi)RNAs in muscle that regulate Twist-1. miR-206, one of the most important muscle-specific miRNAs (myomiRs), was identified as a possible regulator of Twist-1 mRNA. Luciferase assays and transfections in human foetal myoblasts showed that Twist-1 is a direct target of miR-206 and that through this pathway muscle cell differentiation is promoted. We next investigated whether MyoD, a major myogenic transcription factor, regulates Twist-1 because it is known that MyoD induces expression of the miR-206 gene. We found that forced MyoD expression induced miR-206 upregulation and Twist-1 downregulation through binding to the miR-206 promoter, followed by increased muscle cell differentiation. Finally, experiments were performed in muscle cells from subjects with congenital myotonic dystrophy type 1, in which myoblasts fail to differentiate into myotubes. MyoD overexpression inhibited Twist-1 through miR-206 induction, which was followed by an increase in muscle cell differentiation. These results reveal a previously unidentified mechanism of myogenesis that might also play an important role in muscle disease.

Epithelial-to-mesenchymal transition in breast cancer: a role for insulin-like growth factor I and insulin-like growth factor-binding protein 3?

Evidence indicates that for most human cancers the problem is not that gene mutations occur but is more dependent upon how the body deals with damaged cells. It has been estimated that only about 1% of human cancers can be accounted for by unmistakable hereditary cancer syndromes, only up to 5% can be accounted for due to high-penetrance, single-gene mutations, and in total only 5%-15% of all cancers may have a major genetic component. The predominant contribution to the causation of most sporadic cancers is considered to be environmental factors contributing between 58% and 82% toward different cancers. A nutritionally poor lifestyle is associated with increased risk of many cancers, including those of the breast. As nutrition, energy balance, macronutrient composition of the diet, and physical activity levels are major determinants of insulin-like growth factor (IGF-I) bioactivity, it has been proposed that, at least in part, these increases in cancer risk and progression may be mediated by alterations in the IGF axis, related to nutritional lifestyle. Localized breast cancer is a manageable disease, and death from breast cancer predominantly occurs due to the development of metastatic disease as treatment becomes more complicated with poorer outcomes. In recent years, epithelial-to-mesenchymal transition has emerged as an important contributor to breast cancer progression and malignant transformation resulting in tumor cells with increased potential for migration and invasion. Furthermore, accumulating evidence suggests a strong link between components of the IGF pathway, epithelial-to-mesenchymal transition, and breast cancer mortality. Here, we highlight some recent studies highlighting the relationship between IGFs, IGF-binding protein 3, and epithelial-to-mesenchymal transition.

Role of IGF1R in Breast Cancer Subtypes, Stemness, and Lineage Differentiation

Insulin-like growth factor (IGF) signaling is fundamental for growth and survival. A large body of evidence (laboratory, epidemiological, and clinical) implicates the exploitation of this pathway in cancer. Up to 50% of breast tumors express the activated form of the type 1 insulin-like growth factor receptor (IGF1R). Breast cancers are categorized into subtypes based upon hormone and ERRB2 receptor expression and/or gene expression profiling. Even though IGF1R influences tumorigenic phenotypes and drug resistance across all breast cancer subtypes, it has specific expression and function in each. In some subtypes, IGF1R levels correlate with a favorable prognosis, while in others it is associated with recurrence and poor prognosis, suggesting different actions based upon cellular and molecular contexts. In this review, we examine IGF1R expression and function as it relates to breast cancer subtype and therapy-acquired resistance. Additionally, we discuss the role of IGF1R in stem cell maintenance and lineage differentiation and how these cell fate influences may alter the differentiation potential and cellular composition of breast tumors.

Insulin-like growth factor-I induces CLU expression through Twist1 to promote prostate cancer growth

Clusterin (CLU) is cytoprotective molecular chaperone that is highly expressed in castrate-resistant prostate cancer (CRPC). CRPC is also characterized by increased insulin-like growth factor (IGF)-I responsiveness which induces prostate cancer survival and CLU expression. However, how IGF-I induces CLU expression and whether CLU is required for IGF-mediated growth signaling remain unknown. Here we show that IGF-I induced CLU via STAT3-Twist1 signaling pathway. In response to IGF-I, STAT3 was phosphorylated, translocated to the nucleus and bound to the Twist1 promoter to activate Twist1 transcription. In turn, Twist1 bound to E-boxes on the CLU promoter and activated CLU transcription. Inversely, we demonstrated that knocking down Twist1 abrogated IGF-I induced CLU expression, indicating that Twist1 mediated IGF-I-induced CLU expression. When PTEN knockout mice were crossed with lit/lit mice, the resultant IGF-I deficiency suppressed Twist1 as well as CLU gene expression in mouse prostate glands. Moreover, both Twist1 and CLU knockdown suppressed prostate cancer growth accelerated by IGF-I, suggesting the relevance of this signaling not only in an in vitro, but also in an in vivo. Collectively, this study indicates that IGF-I induces CLU expression through sequential activation of STAT3 and Twist1, and suggests that this signaling cascade plays a critical role in prostate cancer pathogenesis.

The emerging role of insulin and insulin-like growth factor signaling in cancer stem cells

Cancer cells frequently exploit the IGF signaling, a fundamental pathway mediating development, cell growth, and survival. As a consequence, several components of the IGF signaling are deregulated in cancer and sustain cancer progression. However, specific targeting of IGF-IR in humans has resulted efficacious only in small subsets of cancers, making researches wondering whether IGF system targeting is still worth pursuing in the clinical setting. Although no definite answer is yet available, it has become increasingly clear that other components of the IGF signaling pathway, such as IR-A, may substitute for the lack of IGF-IR, and induce cancer resistance and/or clonal selection. Moreover, accumulating evidence now indicates that IGF signaling is a central player in the induction/maintenance of epithelial mesenchymal transition (EMT) and cell stemness, two strictly related programs, which play a key role in metastatic spread and resistance to cancer treatments. Here we review the evidences indicating that IGF signaling enhances the expression of transcription factors implicated in the EMT program and has extensive cross-talk with specific pathways involved in cell pluripotency and stemness maintenance. In turn, EMT and cell stemness activate positive feed-back mechanisms causing up-regulation of various IGF signaling components. These findings may have novel translational implications.

Unraveling the role of FOXQ1 in colorectal cancer metastasis

Malignant cell transformation, invasion, and metastasis are dependent on the coordinated rewiring of gene expression. A major component in the scaffold of these reprogramming events is one in which epithelial cells lose intercellular connections and polarity to adopt a more motile mesenchymal phenotype, which is largely supported by a robust transcriptional machinery consisting mostly of developmental transcription factors. This study demonstrates that the winged helix transcription factor, FOXQ1, contributes to this rewiring process, in part by directly modulating the transcription of TWIST1, itself a key mediator of metastasis that transcriptionally regulates the expression of important molecules involved in epithelial-to-mesenchymal transition. Forced expression and RNA-mediated silencing of FOXQ1 led to enhanced and suppressed mRNA and protein levels of TWIST1, respectively. Mechanistically, FOXQ1 enhanced the reporter activity of TWIST1 and directly interacted with its promoter. Furthermore, enhanced expression of FOXQ1 resulted in increased migration and invasion in colorectal cancer cell lines, whereas knockdown studies showed the opposite effect. Moreover, using the in vivo chicken chorioallantoic membrane metastasis assay model, FOXQ1 significantly enhanced distant metastasis with minimal effects on tumor growth.

IMPLICATIONS

These findings reveal FOXQ1 as a modulator of TWIST1-mediated metastatic phenotypes and support its potential as a biomarker of metastasis.

Prognostic significance of twist and N-cadherin expression in NSCLC

BACKGROUND

Metastasis is the most common cause of disease failure and mortality for non-small cell lung cancer after surgical resection. Twist has been recently identified as a putative oncogene and a key regulator of carcinoma metastasis. N-cadherin is associated with a more aggressive behavior of cell lines and tumors. The aim of this study was to evaluate the clinical relevance of Twist and N-cadherin expression in NSCLC, and the effects of Twist1 knockdown on lung cancer cells.

METHODS

We examined the expressions of Twist and N-cadherin by immunohistochemistry in 120 cases of non-small cell lung cancer (including 68 cases with follow-up records). We also analyzed Twist1 and N-cadherin mRNA expression in 30 non-small cell lung cancer tissues using quantitative reverse transcription polymerase chain reaction. The functional roles of Twist1 in lung cancer cell lines were evaluated by small interfering RNA-mediated depletion of the protein followed by analyses of cell apoptosis and invasion.

RESULTS

In lung cancer tissues, the overexpression rate of Twist was 38.3% in lung cancer tissues. Overexpression of N-cadherin was shown in 40.83% of primary tumors. Moreover, Twist1 mRNA expression levels correlated with N-cadherin mRNA levels. Furthermore, overexpression of Twist1 or N-cadherin in primary non-small cell lung cancers was associated with a shorter overall survival (P<0.01, P<0.01, respectively). Depleting Twist expression inhibited cell invasion and increased apoptosis in lung cancer cell lines.

CONCLUSIONS

The overexpression of Twist and N-cadherin could be considered as useful biomarkers for predicting the prognosis of NSCLC. Twist1 could inhibit apoptosis and promote the invasion of lung cancer cells, and depletion of Twist1 in lung cancer cells led to inhibition of N-cadherin expression.

Orally efficacious novel small molecule 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-α-D-glucopyranose selectively and potently stimulates insulin receptor and alleviates diabetes

Type 2 diabetes (T2D) has become an epidemic worldwide while T1D remains a great medical challenge. Insulin receptor (IR) signaling activators could alleviate hyperglycemia, reduce the burden on the pancreas, and contribute to prevention and treatment of both types of diabetes. Previously, we reported the synthesis and identification of a natural antidiabetic compound α-penta-galloyl-glucose (α-PGG). Subsequent studies led to the identification of an α-P6GG derivative, 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-α-D-glucopyranose (6Cl-TGQ). Here, we report that 6Cl-TGQ not only induced rapid and long-lasting glucose uptake comparable to insulin in adipocytes but also reduced high blood glucose levels to near normal and significantly decreased plasma insulin levels and improved glucose tolerance performance in high-fat diet-induced T2D mice when administered orally at 5 mg/kg once every other day. Moreover, a single gavage of 6Cl-TGQ at 10 mg/kg induced rapid and sharp decline of blood glucose in streptozotocin-induced T1D mice. Our studies further indicated that 6Cl-TGQ activated IR signaling in cell models and insulin-responsive tissues of mice. 6Cl-TGQ-induced Akt phosphorylation was completely blocked by IR and PI3K inhibitors, while the induced glucose uptake was blocked by the same compounds and a Glut4 inhibitor. Receptor binding studies indicated that 6Cl-TGQ bound to IR with a higher affinity than α-PGG. Importantly, 6Cl-TGQ, unlike insulin, selectively induced phosphorylation of IR without activating IGF1R or its signaling and did not increase cancer cell proliferation. These results indicate that 6Cl-TGQ is a potent orally efficacious compound with low carcinogenic potential and may contribute to the prevention and treatment of T1D and T2D.

Hepatic and plasma sex differences in saturated and monounsaturated fatty acids are associated with differences in expression of elongase 6, but not stearoyl-CoA desaturase in Sprague-Dawley rats

Monounsaturated fatty acids (MUFA) have been viewed as either beneficial or neutral with respect to health; however, recent evidence suggests that MUFA may be associated with obesity and cardiovascular disease. Sex differences in MUFA composition have been reported in both rats and humans, but the basis for this sexual dimorphism is unknown. In the current study, enzymes involved in MUFA biosynthesis are examined in rat and cell culture models. Male and female rats were maintained on an AIN-93G diet prior to killing at 14 weeks of age after an overnight fast. Concentrations of 16:0 (2,757 ± 616 vs. 3,515 ± 196 μg fatty acid/g liver in males), 18:1n-7 (293 ± 66 vs. 527 ± 49 μg/g) and 18:1n-9 (390 ± 80 vs. 546 ± 47 μg/g) were lower, and concentrations of 18:0 (5,943 ± 1,429 vs. 3,987 ± 325 μg/g) were higher in phospholipids in livers from female rats compared with males. Hepatic elongase 6 mRNA and protein were 5.9- and 2.0-fold higher, respectively, in females compared with males. Stearoyl-CoA desaturase expression did not differ. Specific hormonal effects were examined in HepG2 cells cultured with varying concentrations of 17β-estradiol, progesterone and testosterone (0, 10, 30 and 100 nM) for 72 h. Progesterone and 17β-estradiol treatments increased, while testosterone decreased, elongase 6 protein. Sex differences in MUFA composition were associated with increased expression of hepatic elongase 6 in females relative to male rats, which appears to be mediated by sex hormones based on observations of hormonal treatments of HepG2 cells.

Nuclear targeting of IGF-1 receptor in orbital fibroblasts from Graves' disease: apparent role of ADAM17

Insulin-like growth factor-1 receptor (IGF-1R) comprises two subunits, including a ligand binding domain on extra- cellular IGF-1Rα and a tyrosine phosphorylation site located on IGF-1Rβ. IGF-1R is over-expressed by orbital fibroblasts in the autoimmune syndrome, Graves' disease (GD). When activated by IGF-1 or GD-derived IgG (GD-IgG), these fibroblasts produce RANTES and IL-16, while those from healthy donors do not. We now report that IGF-1 and GD-IgG provoke IGF-1R accumulation in the cell nucleus of GD fibroblasts where it co-localizes with chromatin. Nuclear IGF-1R is detected with anti-IGF-1Rα-specific mAb and migrates to approximately 110 kDa, consistent with its identity as an IGF-1R fragment. Nuclear IGF-1R migrating as a 200 kDa protein and consistent with an intact receptor was undetectable when probed with either anti-IGF-1Rα or anti-IGF-1Rβ mAbs. Nuclear redistribution of IGF-1R is absent in control orbital fibroblasts. In GD fibroblasts, it can be abolished by an IGF-1R-blocking mAb, 1H7 and by physiological concentrations of glucocorticoids. When cell-surface IGF-1R is cross-linked with ¹²⁵I IGF-1, ¹²⁵I-IGF-1/IGF-1R complexes accumulate in the nuclei of GD fibroblasts. This requires active ADAM17, a membrane associated metalloproteinase, and the phosphorylation of IGF-1R. In contrast, virally encoded IGF-1Rα/GFP fusion protein localizes equivalently in nuclei in both control and GD fibroblasts. This result suggests that generation of IGF-1R fragments may limit the accumulation of nuclear IGF-1R. We thus identify a heretofore-unrecognized behavior of IGF-1R that appears limited to GD-derived fibroblasts. Nuclear IGF-1R may play a role in disease pathogenesis.

Critical role for TWIST1 in the induction of human uterine decidualization

The importance of the transcription factor TWIST1 for uterine decidualization was examined in human uterine fibroblast (HUF) cells decidualized in vitro with medroxyprogesterone, estradiol (E2), and prostaglandin E2. TWIST1 mRNA levels increased by 6.0- to 6.8-fold during the first 1-2 d of decidualization and remained above predecidualization levels for up to 15 d. Pretreatment of HUF cells with a TWIST1 small interfering RNA (siRNA) for 3 d before the induction of decidualization resulted in less morphologic differentiation than HUF cells pretreated with a nonsilencing control RNA. In addition, the cells pretreated with TWIST1 siRNA expressed 75-95% less IGF binding protein 1, LEFTY2, fibromodulin, laminin, and several other mRNA during decidualization, including the mRNA for the transcription factors forkhead box protein O1 and v-ets-erythroblastosis virus E26, both of which were previously shown to be critical for the induction of decidualization. The HUF cells pretreated with the TWIST1 siRNA also underwent less apoptosis during decidualization than the control cells, as evidenced by a 20% decrease in DNA fragmentation (terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling assay) and a 43-48% decrease in caspase 3, BCL2-associated X protein, and TNF receptor superfamily member 6 mRNA levels. Although the knockdown of TWIST1 expression markedly attenuated the induction of decidualization, overexpression of TWIST1 alone was insufficient to induce the decidualization of HUF cells. Taken together, these findings strongly implicate an essential role for TWIST1 in the initiation of human decidualization and uterine stromal cell apoptosis that occurs upstream of the induction of forkhead box protein O1 and v-ets-erythroblastosis virus E26 mRNA.

A novel domain of caveolin-2 that controls nuclear targeting: regulation of insulin-specific ERK activation and nuclear translocation by caveolin-2

Herein, we report that insulin-activated extracellular signal-regulated kinase (ERK) is translocated to the nuclear envelope by caveolin-2 (cav-2) and associates with lamin A/C in the inner nuclear membrane in response to insulin. We identified that the Ser¹⁵⁴ -Val¹⁵⁵ -Ser¹⁵⁶ domain on the C-terminal of cav-2 is essential for insulin-induced phosphorylation and nuclear targeting of ERK and cav-2. In human embryonic kidney 293T cells, ERK was not activated and translocated to the nucleus by insulin in comparison to insulin-like growth factor-1 (IGF-1). However, insulin-stimulated activation of ERK was induced by exogenous addition of cav-2. The activated ERK associated and translocated with the cav-2 to the nucleus. In turn, cav-2 promoted phospho-ERK interaction with lamin A/C in the inner nuclear membrane. In contrast, ERK, but not cav-2, was phosphorylated and translocated to the nucleus by IGF-1. The nuclear targeted phospho-ERK failed to localize in the nuclear envelope in response to IGF-1. Together, our data demonstrate that translocation of phospho-ERK to the nuclear envelope is mediated by Ser¹⁵⁴ -Val¹⁵⁵ -Ser¹⁵⁶ domain of cav-2 and this event is an insulin-specific action.

mRNA expression signatures of human skeletal muscle atrophy identify a natural compound that increases muscle mass

Skeletal muscle atrophy is a common and debilitating condition that lacks a pharmacologic therapy. To develop a potential therapy, we identified 63 mRNAs that were regulated by fasting in both human and mouse muscle, and 29 mRNAs that were regulated by both fasting and spinal cord injury in human muscle. We used these two unbiased mRNA expression signatures of muscle atrophy to query the Connectivity Map, which singled out ursolic acid as a compound whose signature was opposite to those of atrophy-inducing stresses. A natural compound enriched in apples, ursolic acid reduced muscle atrophy and stimulated muscle hypertrophy in mice. It did so by enhancing skeletal muscle insulin/IGF-I signaling and inhibiting atrophy-associated skeletal muscle mRNA expression. Importantly, ursolic acid's effects on muscle were accompanied by reductions in adiposity, fasting blood glucose, and plasma cholesterol and triglycerides. These findings identify a potential therapy for muscle atrophy and perhaps other metabolic diseases.

The insulin receptor: a new target for cancer therapy

A large body of evidences have shown that both the IGF-I receptor (IGF-IR) and the insulin receptor (IR) play a role in cancer development and progression. In particular, IR overactivation by IGF-II is common in cancer cells, especially in dedifferentiated/stem-like cells. In spite of these findings, until very recently, only IGF-IR but not IR has been considered a target in cancer therapy. Although several preclinical studies have showed a good anti-cancer activity of selective anti-IGF-IR drugs, the results of the clinical first trials have been disappointing. In fact, only a small subset of malignant tumors has shown an objective response to these therapies. Development of resistance to anti-IGF-IR drugs may include upregulation of IR isoform A (IR-A) in cancer cells and its overactivation by increased secretion of autocrine IGF-II. These findings have led to the concept that co-targeting IR together with IGF-IR may increase therapy efficacy and prevent adaptive resistance to selective anti-IGF-IR drugs. IR blockade should be especially considered in tumors with high IR-A:IGF-IR ratio and high levels of autocrine IGF-II. Conversely, insulin sensitizers, which ameliorate insulin resistance associated with metabolic disorders and cancer treatments, may have important implications for cancer prevention and management. Only few drugs co-targeting the IR and IGF-IR are currently available. Ideally, future IR targeting strategies should be able to selectively inhibit the tumor promoting effects of IR without impairing its metabolic effects.

Oncogenic KRas suppresses inflammation-associated senescence of pancreatic ductal cells

Mutational activation of KRas is the first and most frequently detected genetic lesion in pancreatic ductal adenocarcinoma (PDAC). However, the precise role of oncogenic KRas in the pathogenesis of PDAC is not fully understood. Here, we report that the endogenous expression of oncogenic KRas suppresses premature senescence in primary pancreatic duct epithelial cells (PDEC). Oncogenic KRas-mediated senescence bypass is conferred by the upregulation of the basic helix-loop-helix transcription factor Twist that in turn abrogates p16(INK4A) induction. Moreover, the KRas-Twist-p16(INK4A) senescence bypass pathway is employed in vivo to prevent inflammation-associated senescence of pancreatic ductal epithelium. Our findings indicate that oncogenic KRas could contribute to PDAC initiation by protecting cells from entering a state of permanent growth arrest.

Bypass mechanisms of the androgen receptor pathway in therapy-resistant prostate cancer cell models

BACKGROUND

Prostate cancer is initially dependent on androgens for survival and growth, making hormonal therapy the cornerstone treatment for late-stage tumors. However, despite initial remission, the cancer will inevitably recur. The present study was designed to investigate how androgen-dependent prostate cancer cells eventually survive and resume growth under androgen-deprived and antiandrogen supplemented conditions. As model system, we used the androgen-responsive PC346C cell line and its therapy-resistant sublines: PC346DCC, PC346Flu1 and PC346Flu2.

METHODOLOGY/PRINCIPAL FINDINGS

Microarray technology was used to analyze differences in gene expression between the androgen-responsive and therapy-resistant PC346 cell lines. Microarray analysis revealed 487 transcripts differentially-expressed between the androgen-responsive and the therapy-resistant cell lines. Most of these genes were common to all three therapy-resistant sublines and only a minority (∼5%) was androgen-regulated. Pathway analysis revealed enrichment in functions involving cellular movement, cell growth and cell death, as well as association with cancer and reproductive system disease. PC346DCC expressed residual levels of androgen receptor (AR) and showed significant down-regulation of androgen-regulated genes (p-value = 10(-7)). Up-regulation of VAV3 and TWIST1 oncogenes and repression of the DKK3 tumor-suppressor was observed in PC346DCC, suggesting a potential AR bypass mechanism. Subsequent validation of these three genes in patient samples confirmed that expression was deregulated during prostate cancer progression.

CONCLUSIONS/SIGNIFICANCE

Therapy-resistant growth may result from adaptations in the AR pathway, but androgen-independence may also be achieved by alternative survival mechanisms. Here we identified TWIST1, VAV3 and DKK3 as potential players in the bypassing of the AR pathway, making them good candidates as biomarkers and novel therapeutical targets.

Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1

In a previous study it was found that the therapeutic effects of QLT0267, a small molecule inhibitor of integrin-linked kinase (ILK), were influenced by Her2/neu expression. To understand how inhibition or silencing of ILK influences Her2/neu expression, Her2/neu signaling was evaluated in six Her2/neu-positive breast cancer cell lines (LCC6^Her2, MCF7^Her2, SKBR3, BT474, JIMT-1 and KPL-4). Treatment with QLT0267 engendered suppression (32–87%) of total Her2/neu protein in these cells. Suppression of Her2/neu was also observed following small interfering RNA-mediated silencing of ILK expression. Time course studies suggest that ILK inhibition or silencing caused transient decreases in P-AKT^ser473, which were not temporally related to Her2/neu downregulation. Attenuation of ILK activity or expression was, however, associated with decreases in YB-1 (Y-box binding protein-1) protein and transcript levels. YB-1 is a known transcriptional regulator of Her2/neu expression, and in this study it is demonstrated that inhibition of ILK activity using QLT0267 decreased YB-1 promoter activity by 50.6%. ILK inhibition was associated with changes in YB-1 localization, as reflected by localization of cytoplasmic YB-1 into stress granules. ILK inhibition also suppressed TWIST (a regulator of YB-1 expression) protein expression. To confirm the role of ILK on YB-1 and TWIST, cells were engineered to overexpress ILK. This was associated with a fourfold increase in the level of YB-1 in the nucleus, and a 2- and 1.5-fold increase in TWIST and Her2/neu protein levels, respectively. Taken together, these data indicate that ILK regulates the expression of Her2/neu through TWIST and YB-1, lending support to the use of ILK inhibitors in the treatment of aggressive Her2/neu-positive tumors.

MYC in oncogenesis and as a target for cancer therapies

MYC proteins (c-MYC, MYCN, and MYCL) regulate processes involved in many if not all aspects of cell fate. Therefore, it is not surprising that the MYC genes are deregulated in several human neoplasias as a result from genetic and epigenetic alterations. The near "omnipotency" together with the many levels of regulation makes MYC an attractive target for tumor intervention therapy. Here, we summarize some of the current understanding of MYC function and provide an overview of different cancer forms with MYC deregulation. We also describe available treatments and highlight novel approaches in the pursuit for MYC-targeting therapies. These efforts, at different stages of development, constitute a promising platform for novel, more specific treatments with fewer side effects. If successful a MYC-targeting therapy has the potential for tailored treatment of a large number of different tumors.

Twist2 regulates CD7 expression and galectin-1-induced apoptosis in mature T-cells

In the periphery, a galectin-1 receptor, CD7, plays crucial roles in galectin-1-mediated apoptosis of activated T-cells as well as progression of T-lymphoma. Previously, we demonstrated that NF-kappaB downregulated CD7 gene expression through the p38 MAPK pathway in developing immature thymocytes. However, its regulatory pathway is not well understood in functional mature T-cells. Here, we show that CD7 expression was downregulated by Twist2 in Jurkat cells, a human acute T-cell lymphoma cell line, and in EL4 cells, a mature murine T-cell lymphoma cell line. Furthermore, ectopic expression of Twist2 in Jurkat cells reduced galectin-1-induced apoptosis. While full-length Twist2 decreased CD7 promoter activity, a C-terminal deletion form of Twist2 reversed its inhibition, suggesting an important role of the C-terminus in CD7 regulation. In addition, CD7 expression was enhanced by histone deacetylase inhibitors such as trichostatin A and sodium butyrate, which indicates that Twist2 might be one of candidate factors involved in histone deacetylation. Based on these results, we conclude that upregulation of Twist2 increases the resistance to galectin-1-mediated-apoptosis, which may have significant implications for the progression of some T-cells into tumors such as Sezary cells.

Gene expression profiling of pulmonary fibrosis identifies Twist1 as an antiapoptotic molecular "rectifier" of growth factor signaling

Idiopathic pulmonary fibrosis (IPF) is a progressive and typically fatal lung disease. To gain insight into IPF pathogenesis, we performed gene expression profiling of IPF lungs. Twist1, a basic helix-loop-helix protein, was found among the most consistently and highly up-regulated genes and was expressed in nuclei of type II epithelial cells, macrophages, and fibroblasts in IPF lungs. We studied the function of Twist1 in fibroblasts further, because they are the major effector cells in this disease and persist despite an ambient proapoptotic environment. Twist1 was induced by the profibrotic growth factors (GFs) basic fibroblast growth factor, platelet-derived growth factor, and epidermal growth factor in primary rat lung fibroblasts (RLFs). Suppression of Twist1 expression resulted in decreased RLF accumulation due to increased apoptosis, whereas Twist1 overexpression protected RLFs against several apoptotic stimuli. Addition of platelet-derived growth factor in combination with other GFs led to an increase in proliferation. When Twist1 was depleted, GFs continued to act as mitogens but caused a marked increase in cell death. The increase in apoptosis under basal or growth factor-stimulated conditions was partly mediated by up-regulation of the proapoptotic Bcl-2 family members, Bim and PUMA. These findings indicate that Twist1 promotes survival and accumulation of fibroblasts by shaping their responsiveness to growth factor stimulation. We propose that Twist1 represents one of the factors that promotes pathogenic accumulation of fibroblasts in fibrotic lung disease.

Evidence for an association between thyroid-stimulating hormone and insulin-like growth factor 1 receptors: a tale of two antigens implicated in Graves' disease

Thyroid-stimulating hormone receptor (TSHR) plays a central role in regulating thyroid function and is targeted by IgGs in Graves' disease (GD-IgG). Whether TSHR is involved in the pathogenesis of thyroid-associated ophthalmopathy (TAO), the orbital manifestation of GD, remains uncertain. TSHR signaling overlaps with that of insulin-like grow factor 1 receptor (IGF-1R). GD-IgG can activate fibroblasts derived from donors with GD to synthesize T cell chemoattractants and hyaluronan, actions mediated through IGF-1R. In this study, we compare levels of IGF-1R and TSHR on the surfaces of TAO and control orbital fibroblasts and thyrocytes and explore the physical and functional relationship between the two receptors. TSHR levels are 11-fold higher on thyrocytes than on TAO or control fibroblasts. In contrast, IGF-1R levels are 3-fold higher on TAO vs control fibroblasts. In pull-down studies using fibroblasts, thyrocytes, and thyroid tissue, Abs directed specifically against either IGF-1Rbeta or TSHR bring both proteins out of solution. Moreover, IGF-1Rbeta and TSHR colocalize to the perinuclear and cytoplasmic compartments in fibroblasts and thyrocytes by confocal microscopy. Examination of orbital tissue from patients with TAO reveals similar colocalization to cell membranes. Treatment of primary thyrocytes with recombinant human TSH results in rapid ERK phosphorylation which can be blocked by an IGF-1R-blocking mAb. Our findings suggest that IGF-1R might mediate some TSH-provoked signaling. Furthermore, they indicate that TSHR levels on orbital fibroblasts are considerably lower than those on thyrocytes and that this receptor associates with IGF-1R in situ and together may comprise a functional complex in thyroid and orbital tissue.

Anoikis: a necessary death program for anchorage-dependent cells

Cell to matrix adhesion is a key factor for cellular homeostasis and disruption of such interaction has adverse effects on cell survival. It leads to a specific type of apoptosis known as "anoikis" in most non-transformed cell types. This kind of apoptosis following loss of cell anchorage is important for development, tissue homeostasis and several diseases. Integrins sense mechanical forces arising from the matrix, thereby converting these stimuli to downstream signals modulating cell viability. Anchorage-independent growth is a crucial step during tumorigenesis and in particular during the metastatic spreading of cancer cells. The disruption of the tight control leading an "homeless" cell to death is therefore able to violate the cell defences against transformation. This review analyses the recent investigations into the molecular mechanisms governing anoikis, discussing the different ways in which adhesion can influence this process and addressing the relevance of this unique apoptosis mode in the development of metastatic cancers, as well as in other diseases.

Insulin-like growth factor-I-dependent up-regulation of ZEB1 drives epithelial-to-mesenchymal transition in human prostate cancer cells

The epithelial-to-mesenchymal transition (EMT) is crucial for the migration and invasion of many epithelial tumors, including prostate cancer. Although it is known that ZEB1 overexpression promotes EMT primarily through down-regulation of E-cadherin in a variety of cancers, the soluble ligands responsible for the activation of ZEB1 have yet to be identified. In the present study, we investigated the role of insulin-like growth factor-I (IGF-I) in the regulation of ZEB1 during EMT associated with prostate tumor cell migration. We found that ZEB1 is expressed in highly aggressive prostate cancer cells and that its expression correlates directly with Gleason grade in human prostate tumors (P < 0.001). IGF-I up-regulates ZEB1 expression in prostate cancer cells exhibiting an epithelial phenotype. In prostate cancer cells displaying a mesenchymal phenotype, ZEB1 inhibition reverses the suppression of E-cadherin protein and down-regulates the expression of the mesenchymal markers N-cadherin and fibronectin. Furthermore, ZEB1 blockade decreases migratory and invasive potential in ARCaP(M) compared with the control. These results identify ZEB1 as a key transcriptional regulator of EMT in prostate cancer and suggest that the aberrant expression of ZEB1 in prostate cancer cells occurs in part in response to IGF-I stimulation.

Twist1 homodimers enhance FGF responsiveness of the cranial sutures and promote suture closure

Haploinsufficiency of the transcription factor TWIST1 is associated with Saethre-Chotzen Syndrome and is manifested by craniosynostosis, which is the premature closure of the calvaria sutures. Previously, we found that Twist1 forms functional homodimers and heterodimers that have opposing activities. Our data supported a model that within the calvaria sutures Twist1 homodimers (T/T) reside in the osteogenic fronts while Twist1/E protein heterodimers (T/E) are in the mid-sutures. Twist1 haploinsufficiency alters the balance between these dimers, favoring an increase in homodimer formation throughout the sutures. The data we present here further supports this model and extends it to integrate the Twist1 dimers with the pathways that are known to regulate cranial suture patency. This data provides the first evidence of a functional link between Twist1 and the FGF pathway, and indicates that differential regulation of FGF signaling by T/T and T/E dimers plays a central role in governing cranial suture patency. Furthermore, we show that inhibition of FGF signaling prevents craniosynostosis in Twist1(+/-) mice, demonstrating that inhibition of a signaling pathway that is not part of the initiating mutation can prevent suture fusion in a relevant genetic model of craniosynostosis.

Insulin-like growth factor-i regulates Kruppel-like factor-6 gene expression in a p53-dependent manner

High-circulating IGF-I concentrations are associated with an increased risk for breast, prostate, and colorectal cancer. Krüppel-like factor-6 (KLF6) is a zinc finger tumor suppressor inactivated in prostate and other types of cancer. We have previously demonstrated that KLF6 is a potent transactivator of the IGF-I receptor promoter. The aim of the present study was to examine the potential regulation of KLF6 gene expression by IGF-I. The human colon cancer cell lines HCT116 +/+ and -/- (with normal and disrupted p53, respectively) were treated with IGF-I. Western blots, quantitative RT-PCR, and transfection assays were used to evaluate the effect of IGF-I on KLF-6 production. Signaling pathway inhibitors were used to identify the mechanisms responsible for regulation of KLF6 expression. Small interfering RNA against p53 and KLF6 was used to assess the role of p53 in regulation of KLF6 expression by IGF-I and to evaluate KLF6 involvement in cell cycle control. Results obtained showed that IGF-I stimulated KLF-6 transcription in cells with normal, but not disrupted, p53, suggesting that KLF6 is a downstream target for IGF-I action. Stimulation of KLF6 expression by IGF-I in a p53-dependent manner may constitute a novel mechanism of action of IGF-I, with implications in normal cell cycle progression and cancer biology.

Twist induces reversal of myotube formation

Mammals possess reduced ability to regenerate lost tissue, compared with other vertebrates, which can regenerate through differentiation of precursor cells or de-differentiation. Mammalian multinucleated myotube formation is a differentiation process, which arises from the fusion of mononucleated myoblasts and is thought to be an irreversible process toward muscle formation. By overexpressing the Twist gene in terminally differentiated myotubes, we managed to induce reversal of cell differentiation. More specifically, following expression of the Twist gene, myotubes underwent morphological changes that caused them to cleave. This was accompanied by a reduction in the expression of certain myogenic markers. Interestingly, Twist overexpression also caused a reduction in the muscle transcription factor MyoD. Further experiments showed an increase in the cell cycle entry molecule, cyclin D1 and initiation of DNA synthesis, due to Twist overexpression. The exploitation of Twist-mediated reversal of differentiation and the study of its specific mechanism would be important in order to study mammalian cellular de-differentiation and determine its potential in muscle regeneration.