IGF research 2016-2018

The role of IGF/IGF-1R signaling in the regulation of cancer stem cells

Cancer stem cells (CSCs) are a group of tumor cells with high tumorigenic ability and self-renewal potential similar to those of normal stem cells. CSCs are the key "seeds" for tumor development, metastasis, and recurrence. A better insight into the key mechanisms underlying CSC survival improves the efficiency of cancer therapy via specific targeting of CSCs. Insulin-like growth factor (IGF)/IGF-1 receptor (IGF-1R) signaling plays an important role in the maintenance of cancer stemness. However, the effect of IGF/IGF-1R signaling on stemness and CSCs and the underlying mechanisms are still controversial. Based on the similarity between CSCs and normal stem cells, this review discusses emerging data on the functions of IGF/IGF-1R signaling in normal stem cells and CSCs and dissects the underlying mechanisms by which IGF/IGF-1R signaling is involved in CSCs. On the other hand, this review highlighted the role of IGF/IGF-1R signaling blockade in multiple CSCs as a potential strategy to improve CSC-based therapy.

Extracellular Interactors of the IGF System: Impact on Cancer Hallmarks and Therapeutic Approaches

Dysregulation of the insulin-like growth factor (IGF) system determines the onset of various pathological conditions, including cancer. Accordingly, therapeutic strategies have been developed to block this system in tumor cells, but the results of clinical trials have been disappointing. After decades of research in the field, it is safe to say that one of the major reasons underlying the poor efficacy of anti-IGF-targeting agents is derived from an underestimation of the molecular complexity of this axis. Genetic, transcriptional, post-transcriptional and functional interactors interfere with the activity of canonical components of this axis, supporting the need for combinatorial approaches to effectively block this system. In addition, cancer cells interface with a multiplicity of factors from the extracellular compartment, which strongly affect cell destiny. In this review, we will cover novel extracellular mechanisms contributing to IGF system dysregulation and the implications of such dangerous liaisons for cancer hallmarks and responses to known and new anti-IGF drugs. A deeper understanding of both the intracellular and extracellular microenvironments might provide new impetus to better decipher the complexity of the IGF axis in cancer and provide new clues for designing novel therapeutic approaches.

Beneficial effect and mechanism of natural resourced polysaccharides on regulating bone metabolism through intestinal flora: A review

Bone metabolism is an important biological process for maintaining bone health. Polysaccharides of natural origin exert beneficial effects on bone metabolism. Polysaccharide molecules often have difficulty passing through the intestinal cell membrane and are directly absorbed in the gastrointestinal tract. Therefore, polysaccharides may affect intestinal flora and play a role in disease treatment. We performed a comprehensive review of the relevant literature published from 2003 to 2023. We found that several polysaccharides from traditional Chinese medicines, including Astragalus, Achyranthes bidentata and Eucommia ulmoides, and the polysaccharides from several dietary fibers mainly composed of inulin, resistant starch, and dextran could enrich the intestinal microbiota group to regulate bone metabolism. The promotion of polysaccharide decomposition by regulating the Bacteroides phylum is particularly critical. Studies on the structure-activity relationship showed that molecular weight, glycosidic bonds, and monosaccharide composition may affect the ability of polysaccharides. The mechanism by which polysaccharides regulate intestinal flora to enhance bone metabolism may be related to the regulation of short-chain fatty acids, immunity, and hormones, involving some signaling pathways, such as TGF-β, Wnt/β-catenin, BMP/Smads, and RANKL. This paper provides a useful reference for the study of polysaccharides and suggests their potential application in the treatment of bone metabolic disorders.

Insulin-like Growth Factor 2 Promotes Tissue-Specific Cell Growth, Proliferation and Survival during Development of Helicoverpa armigera

During development, cells constantly undergo fate choices by differentiating, proliferating, and dying as part of tissue remodeling. However, we only begin to understand the mechanisms of these different fate choices. Here, we took the lepidopteran insect Helicoverpa armigera, the cotton bollworm, as a model to reveal that insulin-like growth factor 2 (IGF-2-like) prevented cell death by promoting cell growth and proliferation. Tissue remodeling occurs during insect metamorphosis from larva to adult under regulation by 20-hydroxyecdysone (20E), a steroid hormone. An unknown insulin-like peptide in the genome of H. armigera was identified as IGF-2-like by sequence analysis using human IGFs. The expression of Igf-2-like was upregulated by 20E. IGF-2-like was localized in the imaginal midgut during tissue remodeling, but not in larval midgut that located nearby. IGF-2-like spread through the fat body during fat body remodeling. Cell proliferation was detected in the imaginal midgut and some fat body cells expressing IGF-2-like. Apoptosis was detected in the larval midgut and some fat body cells that did not express IGF-2-like, suggesting the IGF-2-like was required for cell survival, and IGF-2-like and apoptosis were exclusive, pointing to a survival requirement. Knockdown of Igf-2-like resulted in repression of growth and proliferation of the imaginal midgut and fat body. Our results suggested that IGF-2-like promotes cell growth and proliferation in imaginal tissues, promoting cell death avoidance and survival of imaginal cells during tissue remodeling. It will be interesting to determine whether the mechanism of action of steroid hormones on insulin growth factors is conserved in other species.

Unraveling the IGF System Interactome in Sarcomas Exploits Novel Therapeutic Options

Aberrant bioactivity of the insulin-like growth factor (IGF) system results in the development and progression of several pathologic conditions including cancer. Preclinical studies have shown promising anti-cancer therapeutic potentials for anti-IGF targeted therapies. However, a clear but limited clinical benefit was observed only in a minority of patients with sarcomas. The molecular complexity of the IGF system, which comprises multiple regulators and interactions with other cancer-related pathways, poses a major limitation in the use of anti-IGF agents and supports the need of combinatorial therapeutic strategies to better tackle this axis. In this review, we will initially highlight multiple mechanisms underlying IGF dysregulation in cancer and then focus on the impact of the IGF system and its complexity in sarcoma development and progression as well as response to anti-IGF therapies. We will also discuss the role of Ephrin receptors, Hippo pathway, BET proteins and CXCR4 signaling, as mediators of sarcoma malignancy and relevant interactors with the IGF system in tumor cells. A deeper understanding of these molecular interactions might provide the rationale for novel and more effective therapeutic combinations to treat sarcomas.

WITHDRAWN: Growth hormone improves insulin-like growth factor 1 and steroid hormone levels in follicle fluid, expression of hormone receptors in granulosa cells, and in vitro fertilization outcomes of poor ovarian responders

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Novel Regulators of the IGF System in Cancer

The insulin-like growth factor (IGF) system is a dynamic network of proteins, which includes cognate ligands, membrane receptors, ligand binding proteins and functional downstream effectors. It plays a critical role in regulating several important physiological processes including cell growth, metabolism and differentiation. Importantly, alterations in expression levels or activation of components of the IGF network are implicated in many pathological conditions including diabetes, obesity and cancer initiation and progression. In this review we will initially cover some general aspects of IGF action and regulation in cancer and then focus in particular on the role of transcriptional regulators and novel interacting proteins, which functionally contribute in fine tuning IGF1R signaling in several cancer models. A deeper understanding of the biological relevance of this network of IGF1R modulators might provide novel therapeutic opportunities to block this system in neoplasia.

Osteogenesis and bone remodeling: A focus on growth factors and bioactive peptides

Bone is one of the most frequently transplanted tissues. The bone structure and its physiological function and stem cells biology were known to be closely related to each other for many years. Bone is considered a home to the well-known systems of postnatal mesenchymal stem cells (MSCs). These bone resident MSCs provide a range of growth factors (GF) and cytokines to support cell growth following injury. These GFs include a group of proteins and peptides produced by different cells which are regulators of important cell functions such as division, migration, and differentiation. GF signaling controls the formation and development of the MSCs condensation and plays a critical role in regulating osteogenesis, chondrogenesis, and bone/mineral homeostasis. Thus, a combination of both MSCs and GFs receives high expectations in regenerative medicine, particularly in bone repair applications. It is known that the delivery of exogenous GFs to the non-union bone fracture site remarkably improves healing results. Here we present updated information on bone tissue engineering with a specific focus on GF characteristics and their application in cellular functions and tissue healing. Moreover, the interrelation of GFs with the damaged bone microenvironment and their mechanistic functions are discussed.

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.

Insulin-like growth factor-binding proteins play a significant role in the molecular response to imatinib in chronic myeloid leukemia patients

Imatinib (IM) is successfully used in the majority of patients with chronic myeloid leukemia (CML), but some patients develop resistance to drug treatment. Insufficient apoptosis results in uncontrolled cell proliferation, which is closely associated with the occurrence of drug resistance. Therefore, it is crucial to identify new biomarkers related to drug resistance. This aim of the present study was to investigate the profile of apoptosis-related proteins in K562 and K562/G (IM-resistant K562 cells) cells, in order to identify new biomarkers. A human apoptosis antibody array was used to screen 46 proteins in the two cells lines, among which 20 proteins were found to be differentially expressed between K562 and K562/G cells. The major proteins included secreted caspase-8, insulin-like growth factor-binding protein (IGFBP)-1, IGFBP-2, IGFBP-3, caspase-3 and p27. IGFBP-1 IGFBP-2 and IGFBP-3 were selected for the follow-up study. Subsequently, reverse transcription-quantitative PCR analysis and western blotting were used to detect the expression levels of the IGFBPs. The results revealed that the expression levels of IGFBP-2 and IGFBP-3 in K562/G cells were significantly decreased compared with those in K562 cells, whereas the IGFBP-1 level was higher. Moreover, no significant correlation was observed between IGFBP-1 or IGFBP-2 and the level of the BCR-ABL fusion protein, whereas decreasing IGFBP-3 levels were associated with increasing BCR-ABL levels. These results suggested that IGFBP-1, IGFBP-2 and IGFBP-3 could be useful novel biomarkers for IM resistance in CML.