Identification of ZYG11A as a candidate IGF1-dependent proto-oncogene in endometrial cancer

Identification of UDP-Glucuronosyltransferase 2B15 (UGT2B15) as a Target for IGF1 and Insulin Action

Normal growth and development in mammals are tightly controlled by numerous genetic factors and metabolic conditions. The growth hormone (GH)-insulin-like growth factor-1 (IGF1) hormonal axis is a key player in the regulation of these processes. Dysregulation of the GH-IGF1 endocrine system is linked to a number of pathologies, ranging from growth deficits to cancer. Laron syndrome (LS) is a type of dwarfism that results from mutation of the GH receptor (GHR) gene, leading to GH resistance and short stature as well as a number of metabolic abnormalities. Of major clinical relevance, epidemiological studies have shown that LS patients do not develop cancer. While the mechanisms associated with cancer protection in LS have not yet been elucidated, genomic analyses have identified a series of metabolic genes that are over-represented in LS patients. We hypothesized that these genes might constitute novel targets for IGF1 action. With a fold-change of 11.09, UDP-glucuronosyltransferase 2B15 (UGT2B15) was the top up-regulated gene in LS. The UGT2B15 gene codes for an enzyme that converts xenobiotic substances into lipophilic compounds and thereby facilitates their clearance from the body. We investigated the regulation of UGT2B15 gene expression by IGF1 and insulin. Both hormones inhibited UGT2B15 mRNA levels in endometrial and breast cancer cell lines. Regulation of UGT2B15 protein levels by IGF1/insulin, however, was more complex and not always correlated with mRNA levels. Furthermore, UGT2B15 expression was dependent on p53 status. Thus, UGT2B15 mRNA levels were higher in cell lines expressing a wild-type p53 compared to cells containing a mutated p53. Animal studies confirmed an inverse correlation between UGT2B15 and p53 levels. In summary, increased UGT2B15 levels in LS might confer upon patient’s protection from genotoxic damage.

microRNA-206 Regulates Pancreatic-β-Cell Function via Targeting Insulin-Like Growth Factor 1

Background: Diabetes mellitus (DM), a common metabolic disease, is featured with chronic hyperglycemia and dysfunction of pancreatic β-cells. Various evidences suggested that microRNAs (miR-NAs) were tightly related to the occurrence of DM and can be regulated in pancreatic-β-cells. However, whether or not microRNA-206 (miR-206) affects the development of DM and the specific mechanisms remains elusive. We designed this study to clarify the function and associated potential mechanism of miR-206 in pancreatic β-cells via the insulin-like growth factor 1 reporter (IGF1R)/phosphatidylinositide 3-kinase (PI3 K)/protein kinase B (AKT) signaling pathway, which may provide novel diagnostic or therapies for DM. Methods: In this research, the levels of miR-206 and insulin-like growth factor 1 (IGF1) were assessed using quantitative reverse transcription PCR (qRT-PCR) and/or Western bolt assay. Bioinformatics and dual luciferase reporter assays were adopted to illustrate the relationship between miR-206 and IGF1. INS-1 cells were stimulated with stimulatory glucose (16.7 mM) or basal glucose (3.3 mM) for 1 h, and the insulin content was examined by enzyme linked immunosorbent assay (ELISA). Besides, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry (FCM) analysis were conducted to determine the INS1 cell viability and apoptosis. Furthermore, the related proteins in IGF1R/PI3 K/AKT pathway (IGF1R, p-AKT and AKT) were tested using Western blot assay, respectively. Results: Our data suggested that miR-206 level in the blood samples of DM patients was higher than that in healthy donors. IGF1 was identified as a direct target of miR-206. Moreover, we found that miR-206 negatively regulated IGF1 expression in INS-1 cells. It was also confirmed that miR-206 inhibitor led to an increase of total insulin content, an increase of INS-1 cell viability and a decrease of cell apoptosis. Accordingly, miR-206 inhibitor significantly enhanced IGF1R and p-AKT protein expression in INS-1 cells. All these findings were reversed by IGF1-siRNA co-transfection. Conclusion: Our observations clearly demonstrated that miR-206 could regulate the IGF1R/PI3K/AKT pathway by targeting IGF1, thereby regulating the cell viability of pancreatic β cells and the ability of pancreatic β cells to secrete insulin.

MicroRNA 132-3p Is Upregulated in Laron Syndrome Patients and Controls Longevity Gene Expression

The growth hormone (GH)–insulin-like growth factor-1 (IGF1) endocrine axis is a central player in normal growth and metabolism as well as in a number of pathologies, including cancer. The GH–IGF1 hormonal system, in addition, has emerged as a major determinant of lifespan and healthspan. Laron syndrome (LS), the best characterized entity under the spectrum of the congenital IGF1 deficiencies, results from mutation of the GH receptor (GHR) gene, leading to dwarfism, obesity and other defects. Consistent with the key role of IGF1 in cellular proliferation, epidemiological studies have shown that LS patients are protected from cancer development. While reduced expression of components of the GH-IGF1 axis is associated with enhanced longevity in animal models, it is still unknown whether LS is associated with an increased lifespan. MicroRNAs (miRs) are endogenous short non-coding RNAs that regulate the expression of complementary mRNAs. While a number of miRs involved in the regulation of IGF components have been identified, no previous studies have investigated the differential expression of miRs in congenital IGF1 deficiencies. The present study was aimed at identifying miRs that are differentially expressed in LS and that might account for the phenotypic features of LS patients, including longevity. Our genomic analyses provide evidence that miR-132-3p was highly expressed in LS. In addition, we identified SIRT1, a member of the sirtuin family of histone deacetylases, as a target for negative regulation by miR-132-3p. The data was consistent with the notion that low concentrations of IGF1 in LS lead to elevated miR-132-3p levels, with ensuing reduction in SIRT1 gene expression. The impact of the IGF1-miR-132-3p-SIRT1 loop on aging merits further investigation.

ZYG11A Is Expressed in Epithelial Ovarian Cancer and Correlates With Low Grade Disease

The insulin-like growth factors (IGF) are important players in the development of gynecological malignancies, including epithelial ovarian cancer (EOC). The identification of biomarkers that can help in the diagnosis and scoring of EOC patients is of fundamental importance in clinical oncology. We have recently identified the ZYG11A gene as a new candidate target of IGF1 action. The aim of the present study was to evaluate the expression of ZYG11A in EOC patients and to correlate its pattern of expression with histological grade and pathological stage. Furthermore, and in view of previous analyses showing an interplay between ZYG11A, p53 and the IGF1 receptor (IGF1R), we assessed a potential coordinated expression of these proteins in EOC. In addition, zyg11a expression was assessed in ovaries and uteri of growth hormone receptor (GHR) knock-out mice. Tissue microarray analysis was conducted on 36 patients with EOC and expression of ZYG11A, IGF1R and p53 was assessed by immunohistochemistry. Expression levels were correlated with clinical parameters. qPCR was employed to assess zyg11a mRNA levels in mice tissues. Our analyses provide evidence of reduced ZYG11A expression in high grade tumors, consistent with a putative tumor suppressor role. In addition, an inverse correlation between ZYG11A and p53 levels in individual tumors was noticed. Taken together, our data justify further exploration of the role of ZYG11A as a novel biomarker in EOC.

Autosomal dominant diabetes associated with a novel ZYG11A mutation resulting in cell cycle arrest in beta-cells

Diabetes is a genetically heterogeneous disease, for which we are aiming to identify causative genes. Here, we report a missense mutation (c.T1424C:p.L475P) in ZYG11A identified by exome sequencing as segregating with hyperglycemia in a Thai family with autosomal dominant diabetes. ZYG11A functions as a target recruitment subunit of an E3 ubiquitin ligase complex that plays an important role in the regulation of cell cycle. We demonstrate an increase in cells arrested at G₂/mitotic phase among beta-cells deficient for ZYG11A or overexpressing L475P-ZYG11A, which is associated with a decreased growth rate. This is the first evidence linking a ZYG11A mutation to hyperglycemia, and suggesting ZYG11A as a cell cycle regulator required for beta-cell growth. Since most family members were either overweight or obese, but only mutation carriers developed hyperglycemia, our data also suggests the ZYG11A mutation as a genetic factor predisposing obese individuals to beta-cell failure in maintenance of glucose homeostasis.

Role of the GH-IGF1 system in progression of cancer

Emerging evidence links the growth hormone (GH)-insulin-like growth factor-1 (IGF1) endocrine axis to cancer development. While this putative correlation is of major translational relevance, most clinical and epidemiological reports to date found no causal linkage between GH therapy and enhanced cancer risk. Thus, it is generally agreed that GH therapy constitutes a safe pharmacological intervention. The present review focuses on a number of issues in the area of GH-IGF1 action in cancer development. Emphasis is given to the idea that GH and IGF1 do not conform to the definition of oncogenic factors. Specifically, these hormones, even at high pharmacological doses, are unable to induce malignant transformation. However, the GH-IGF1 axis is capable of 'pushing' already transformed cells through the various phases of the cell cycle. Viral and cellular oncogenes require an intact IGF1 signaling pathway in order to elicit transformation; in other words, oncogenic agents adopt the IGF1 pathway. This universal mechanism of action of oncogenes has broad implications in oncology. Our review provides an in-depth analysis of the interplay between the GH-IGF1 axis and cancer genes, including tumor suppressors p53 and BRCA1. Finally, the safety of GH therapy in both children and adults needs further long-term follow-up studies.

Laron Syndrome Research Paves the Way for New Insights in Oncological Investigation

Laron syndrome (LS) is a rare genetic endocrinopathy that results from mutation of the growth hormone receptor (GH-R) gene and is typically associated with dwarfism and obesity. LS is the best characterized entity under the spectrum of the congenital insulin-like growth factor-1 (IGF1) deficiencies. Epidemiological analyses have shown that LS patients do not develop cancer, whereas heterozygous family members have a cancer prevalence similar to the general population. To identify genes and signaling pathways differentially represented in LS that may help delineate a biochemical and molecular basis for cancer protection, we have recently conducted a genome-wide profiling of LS patients. Studies were based on our collection of Epstein–Barr virus (EBV)-immortalized lymphoblastoid cell lines derived from LS patients, relatives and healthy controls. Bioinformatic analyses identified differences in gene expression in several pathways, including apoptosis, metabolic control, cytokine biology, Jak-STAT and PI3K-AKT signaling, etc. Genes involved in the control of cell cycle, motility, growth and oncogenic transformation are, in general, down-regulated in LS. These genetic events seem to have a major impact on the biological properties of LS cells, including proliferation, apoptosis, response to oxidative stress, etc. Furthermore, genomic analyses allowed us to identify novel IGF1 downstream target genes that have not been previously linked to the IGF1 signaling pathway. In summary, by ‘mining’ genomic data from LS patients, we were able to generate clinically-relevant information in oncology and, potentially, related disciplines.

Below the Surface: IGF-1R Therapeutic Targeting and Its Endocytic Journey

Ligand-activated plasma membrane receptors follow pathways of endocytosis through the endosomal sorting apparatus. Receptors cluster in clathrin-coated pits that bud inwards and enter the cell as clathrin-coated vesicles. These vesicles travel through the acidic endosome whereby receptors and ligands are sorted to be either recycled or degraded. The traditional paradigm postulated that the endocytosis role lay in signal termination through the removal of the receptor from the cell surface. It is now becoming clear that the internalization process governs more than receptor signal cessation and instead reigns over the entire spatial and temporal wiring of receptor signaling. Governing the localization, the post-translational modifications, and the scaffolding of receptors and downstream signal components established the endosomal platform as the master regulator of receptor function. Confinement of components within or between distinct organelles means that the endosome instructs the cell on how to interpret and translate the signal emanating from any given receptor complex into biological effects. This review explores this emerging paradigm with respect to the cancer-relevant insulin-like growth factor type 1 receptor (IGF-1R) and discusses how this perspective could inform future targeting strategies.