IGF

IGF
Name	Insulin-like growth factor
Uniprot	P05019
Organism	Homo sapiens
Length	~70–120 amino acids

IGF

Insulin-like growth factors are peptide hormones central to growth, development, and metabolism across vertebrates. They mediate cellular proliferation, differentiation, and survival through endocrine, paracrine, and autocrine signaling and interact with multiple receptors and binding proteins to produce tissue-specific effects. Research on IGF spans molecular biology, clinical medicine, biotechnology, and public health and intersects with work by institutions and investigators worldwide.

Introduction

Insulin-like growth factors comprise a family including IGF-I and IGF-II, produced primarily by the Liver, Placenta, and diverse tissues such as Skeletal muscle, Bone marrow, and Adipose tissue. Circulating IGFs are bound to a family of six high-affinity IGF binding proteins (IGFBP-1 through IGFBP-6) synthesized by the Liver and local cells. The IGF axis signals via the Insulin receptor family, notably the IGF1 receptor and hybrid receptors, integrating inputs from hormones such as Growth hormone, nutrients sensed by mTOR, and factors regulated in the Hypothalamus. Evolutionary conservation is evident from comparative studies in Drosophila melanogaster, Caenorhabditis elegans, and Xenopus laevis.

Biological Function and Mechanism

IGF peptides bind to tyrosine kinase receptors, principally the IGF1 receptor, activating receptor autophosphorylation and downstream cascades such as the PI3K/AKT pathway and the MAPK/ERK pathway. These pathways control cell size, proliferation, apoptosis resistance, and metabolism in tissues including Cardiac muscle, Chondrocytes, and Neurons of the Cerebral cortex. IGF-II plays critical roles in fetal development and is regulated by imprinting at the H19/IGF2 locus on chromosome 11, with epigenetic control studied in contexts involving Imprinting disorders and imprinting mechanisms described by researchers at institutions like Harvard Medical School and Cold Spring Harbor Laboratory. Interactions with Insulin receptor substrate 1 and IGF-binding protein 3 modulate bioavailability and receptor activation, while proteases such as Pregnancy-associated plasma protein-A cleave IGFBPs to increase local IGF action. Cross-talk occurs with signaling modules studied by groups at the National Institutes of Health and European Molecular Biology Laboratory.

Clinical Significance and Disorders

Alterations in IGF signaling are implicated in growth disorders, metabolic syndromes, and oncogenesis. Deficient IGF-I or receptor mutations manifest as short stature syndromes described in cohorts at Great Ormond Street Hospital and genetic centers at University College London. Overexpression or elevated circulating levels correlate with increased risk of cancers including Breast cancer, Colorectal cancer, Prostate cancer, and hepatocellular carcinoma investigated by teams at MD Anderson Cancer Center and Institut Curie. Loss of imprinting at the H19/IGF2 locus associates with Beckwith-Wiedemann syndrome and tumor predisposition studied by pediatric oncologists at St Jude Children’s Research Hospital. IGF axis perturbations are also linked to aging research at Salk Institute and metabolic research at Joslin Diabetes Center.

Measurement and Diagnostic Use

Clinical measurement of IGF involves serum IGF-I assays standardized against age- and sex-specific reference ranges established by clinical laboratories at institutions such as Mayo Clinic and Cleveland Clinic. Immunoassays, liquid chromatography–mass spectrometry, and IGFBP proteolysis tests are used in endocrinology services at Karolinska Institutet and University of California, San Francisco. IGF-I levels aid diagnosis and monitoring of Growth hormone deficiency, Acromegaly treated at centers like Royal Free Hospital and Mount Sinai Hospital, and are incorporated into pediatric growth charts used by public health agencies including World Health Organization. Preanalytical variables and binding protein interference necessitate careful interpretation following guidelines from societies such as the Endocrine Society.

Therapeutic Applications and Research

Recombinant IGF-I and analogs have been developed for treatment of severe growth failure and cachexia; clinical trials and translational programs have been conducted at National Cancer Institute and biotechnology firms in collaboration with university hospitals like Johns Hopkins Hospital. Antagonists targeting the IGF1 receptor and monoclonal antibodies have undergone oncology trials at Gustave Roussy and Dana-Farber Cancer Institute to inhibit tumor growth in Sarcoma and epithelial malignancies. Gene therapy approaches using viral vectors to modulate IGF signaling are under investigation at University of Pennsylvania and Shanghai Jiao Tong University. Research on IGFBP modulation, small-molecule inhibitors of downstream kinases, and combination regimens with EGFR inhibitors or mTOR inhibitors is active across consortia including European Organisation for Research and Treatment of Cancer and pharmaceutical companies.

History and Discovery

The IGF family emerged from biochemical work linking peptide factors in serum to growth-promoting activity described in the mid-20th century by investigators at Royal Society-affiliated laboratories and the Rockefeller University. Identification of IGF-I (originally called somatomedin C) and IGF-II followed receptor and binding protein characterization in studies at University of Chicago and Yale University. Cloning of IGF genes, elucidation of imprinting at the H19/IGF2 locus, and structural studies of receptors were advanced by researchers at Cold Spring Harbor Laboratory, Max Planck Institute, and Massachusetts Institute of Technology. Subsequent decades saw translation into clinical assays and therapeutics through collaborations among academic centers, regulatory agencies such as the Food and Drug Administration, and pharmaceutical developers.

Category:Peptide hormones