Gene Summary

Gene:IGF2-AS; IGF2 antisense RNA
Aliases: PEG8, IGF2AS, IGF2-AS1
Summary:This gene is expressed in antisense to the insulin-like growth factor 2 (IGF2) gene and is imprinted and paternally expressed. It is thought to be non-coding because the putative protein is not conserved and translation is predicted to trigger nonsense mediated decay (NMD). Transcripts from this gene are produced in tumors and may function to suppress cell growth. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2015]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 31 August, 2019

Cancer Overview

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Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: IGF2-AS (cancer-related)

Tian W, Jiang C, Huang Z, et al.
Comprehensive analysis of dysregulated lncRNAs, miRNAs and mRNAs with associated ceRNA network in esophageal squamous cell carcinoma.
Gene. 2019; 696:206-218 [PubMed] Related Publications
Mounting evidence suggests that long noncoding RNAs (lncRNAs) play an important role in tumor biology. To date, some lncRNAs have been found to be involved in competitive binding of miRNAs, a major group of competitive endogenous RNAs (ceRNAs), through participation in a regulatory network of protein-coding gene expression. However, the functional roles of lncRNA-mediated ceRNAs in esophageal squamous cell carcinoma (ESCC) have rarely been reported. Here, we construct a hypothetical ceRNA network by analyzing differential expression of lncRNAs, miRNAs and mRNAs obtained from 96 ESCC tissues and 13 normal tissues in the Cancer Genome Atlas. Ultimately, 95 lncRNAs, 9 miRNAs, and 40 mRNAs were identified (fold change >1.5, P < .05) and included in the ceRNA network for ESCC. Moreover, three lncRNAs (IGF2-AS, MUC2 and SOX2-OT) were found to be significantly associated with overall survival (log-rank test, P < .05), and further experiments revealed that lncRNA DLX6-AS1 knockdown inhibited the proliferation and invasion of esophageal cancer cells by enhancing the endogenous function of mTOR. We believe that the identified ceRNA network can facilitate a better understanding of lncRNA-related mechanisms in ESCC.

Liang Y, Zhang C, Ma MH, Dai DQ
Identification and prediction of novel non-coding and coding RNA-associated competing endogenous RNA networks in colorectal cancer.
World J Gastroenterol. 2018; 24(46):5259-5270 [PubMed] Free Access to Full Article Related Publications
AIM: To identify and predict the competing endogenous RNA (ceRNA) networks in colorectal cancer (CRC) by bioinformatics analysis.
METHODS: In the present study, we obtained CRC tissue and normal tissue gene expression profiles from The Cancer Genome Atlas project. Differentially expressed (DE) genes (DEGs) were identified. Then, upregulated and downregulated miRNA-centered ceRNA networks were constructed by analyzing the DEGs using multiple bioinformatics approaches. DEmRNAs in the ceRNA networks were identified in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using KEGG Orthology Based Annotation System 3.0. The interactions between proteins were analyzed using the STRING database. Kaplan-Meier survival analysis was conducted for DEGs and real time quantitative polymerase chain reaction (RT-qPCR) was also performed to validate the prognosis-associated lncRNAs in CRC cell lines.
RESULTS: Eighty-one DElncRNAs, 20 DEmiRNAs, and 54 DEmRNAs were identified to construct the ceRNA networks of CRC. The KEGG pathway analysis indicated that nine out of top ten pathways were related with cancer and the most significant pathway was "colorectal cancer". Kaplan-Meier survival analysis showed that the overall survival was positively associated with five DEGs (IGF2-AS, POU6F2-AS2, hsa-miR-32, hsa-miR-141, and SERPINE1) and it was negatively related to three DEGs (LINC00488, hsa-miR-375, and PHLPP2). Based on the STRING protein database, it was found that SERPINE1 and PHLPP2 interact with AKT1. Besides, SERPINE1 can interact with VEGFA, VTN, TGFB1, PLAU, PLAUR, PLG, and PLAT. PHLPP2 can interact with AKT2 and AKT3. RT-qPCR revealed that the expression of IGF2-AS, POU6F2-AS2, and LINC00488 in CRC cell lines was consistent with the
CONCLUSION: CeRNA networks play an important role in CRC. Multiple DEGs are related with clinical prognosis, suggesting that they may be potential targets in tumor diagnosis and treatment.

Chen Q, Sun T, Wang F, et al.
Long Noncoding RNA IGF2AS is Acting as an Epigenetic Tumor Suppressor in Human Prostate Cancer.
Urology. 2019; 124:310.e1-310.e8 [PubMed] Related Publications
OBJECTIVE: To assess the expression profile and functional mechanism of long noncoding RNA (lncRNA) insulin growth factor 2 antisense (IGF2AS) in human prostate cancer (PCa).
METHODS: Quantitative reverse transcriptase-polymerase chain reaction was applied to assess IGF2AS expression in immortal PCa cell lines and in situ human PCa tumors. IGF2AS was overexpressed in VCaP and PC3 cells to assess its effect on PCa cell proliferation and invasion in vitro, and xenograft in vivo. The effect of IGF2AS overexpression on IGF2 was also assessed in PCa cells. Then, IGF2 was upregulated in IGF2AS-overexpressed PCa cells to assess the functional involvement of IGF2 in IGF2AS-mediated PCa cell development.
RESULTS: IGF2AS was downregulated in both PCa cell lines and human PCa tumors. In VCaP and PC3 cells, lentivirus-induced IGF2AS overexpression suppressed cancer cell proliferation and invasion in vitro, and xenograft development in vivo. IGF2 was downregulated by IGF2AS overexpression. Conversely, IGF2 upregulation revered the suppressing function of IGF2AS on PCa proliferation and invasion.
CONCLUSION: LncRNA IGF2AS is acting as an epigenetic tumor suppressor in human PCa, likely through inverse regulation on IGF2. IGF2AS/IGF2 axis may be a future therapeutic target for PCa treatment.

Zhang Z, Qian W, Wang S, et al.
Analysis of lncRNA-Associated ceRNA Network Reveals Potential lncRNA Biomarkers in Human Colon Adenocarcinoma.
Cell Physiol Biochem. 2018; 49(5):1778-1791 [PubMed] Related Publications
BACKGROUND/AIMS: Long non-coding RNAs (lncRNAs) acting as competing endogenous RNAs (ceRNAs) play significant roles in the development of tumors, but the functions of specific lncRNAs and lncRNA-related ceRNA networks have not been fully elucidated for colon adenocarcinoma (COAD). In this study, we aimed to clarify the lncRNA-microRNA (miRNA)-mRNA ceRNA network and potential lncRNA biomarkers in COAD.
METHODS: We extracted data from The Cancer Genome Atlas (TCGA) and identified COAD-specific mRNAs, miRNAs, and lncRNAs. The biological processes in Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were analyzed for COAD-specific mRNAs. We then constructed a ceRNA network of COAD-specific mRNAs, miRNAs and lncRNAs and analyzed the correlation between expression patterns and clinical features of the lncRNAs involved. After identifying potential mRNA targets of 4 lncRNAs related to overall survival (OS), we conducted stepwise analysis of these targets through GO and KEGG. Using tissue samples from our own patients, we also verified certain analytical results using quantitative real-time PCR (qRT-PCR).
RESULTS: Data from 521 samples (480 tumor tissue and 41 adjacent non-tumor tissue samples) were extracted from TCGA. A total of 258 specific lncRNAs, 206 specific miRNAs, and 1467 specific mRNAs were identified (absolute log2 [fold change] > 2, false discovery rate < 0.01). Analysis of KEGG revealed that specific mRNAs were enriched in cancer-related pathways. The ceRNA network was constructed with 64 lncRNAs, 18 miRNAs, and 42 mRNAs. Among these lncRNAs involved in the network, 3 lncRNAs (LINC00355, HULC, and IGF2-AS) were confirmed to be associated with certain clinical features and 4 lncRNAs (HOTAIR, LINC00355, KCNQ1OT1, and TSSC1-IT1) were found to be negatively linked to OS (log-rank p < 0.05). KEGG showed that the potential mRNA targets of these 4 lncRNAs may be concentrated in the MAPK pathway. Certain results were validated by qRT-PCR.
CONCLUSION: This study providing novel insights into the lncRNA-miRNA-mRNA ceRNA network and reveals potential lncRNA biomarkers in COAD.

Himes BE, Obraztsova K, Lian L, et al.
Rapamycin-independent IGF2 expression in Tsc2-null mouse embryo fibroblasts and human lymphangioleiomyomatosis cells.
PLoS One. 2018; 13(5):e0197105 [PubMed] Free Access to Full Article Related Publications
Lymphangioleiomyomatosis (LAM) is a rare, almost exclusively female lung disease linked to inactivating mutations in tuberous sclerosis complex 2 (TSC2), a tumor suppressor gene that controls cell metabolic state and growth via regulation of the mechanistic target of rapamycin (mTORC1) signaling. mTORC1 is frequently activated in human cancers and, although the mTORC1 inhibitor rapamycin has a cytostatic effect, it is, in general, unable to elicit a robust curative effect or tumor regression. Using RNA-Seq, we identified (1) Insulin-like Growth Factor (IGF2) as one of the genes with the highest fold-change difference between human TSC2-null and TSC2-expressing angiomyolipoma cells from a patient with LAM, and (2) the mouse IGF2 homolog Igf2, as a top-ranking gene according to fold change between Tsc2-/- and Tsc2+/+ mouse embryo fibroblasts (MEFs). We extended transcript-level findings to protein level, observing increased Igf2 protein expression and Igf2 secretion by Tsc2-/- MEFs. Increased Igf2 expression was not due to epigenetic imprinting, but was partially mediated through the Stat3 pathway and was completely insensitive to rapamycin treatment. An siRNA-mediated decrease of Igf2 resulted in decreased Stat3 phosphorylation, suggesting presence of an autocrine Igf2/Stat3 amplification cycle in Tsc2-/- MEFs. In human pulmonary LAM lesions and metastatic cell clusters, high levels of IGF2 were associated with mTORC1 activation. In addition, treatment of three primary IGF2-expressing LAM lung cell lines with rapamycin did not result in IGF2 level changes. Thus, targeting of IGF2 signaling may be of therapeutic value to LAM patients, particularly those who are unresponsive to rapamycin.

Gomih A, Smith JS, North KE, et al.
DNA methylation of imprinted gene control regions in the regression of low-grade cervical lesions.
Int J Cancer. 2018; 143(3):552-560 [PubMed] Free Access to Full Article Related Publications
The role of host epigenetic mechanisms in the natural history of low-grade cervical intraepithelial neoplasia (CIN1) is not well characterized. We explored differential methylation of imprinted gene regulatory regions as predictors of the risk of CIN1 regression. A total of 164 patients with CIN1 were recruited from 10 Duke University clinics for the CIN Cohort Study. Participants had colposcopies at enrollment and up to five follow-up visits over 3 years. DNA was extracted from exfoliated cervical cells for methylation quantitation at CpG (cytosine-phosphate-guanine) sites and human papillomavirus (HPV) genotyping. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression to quantify the effect of methylation on CIN1 regression over two consecutive visits, compared to non-regression (persistent CIN1; progression to CIN2+; or CIN1 regression at a single time-point), adjusting for age, race, high-risk HPV (hrHPV), parity, oral contraceptive and smoking status. Median participant age was 26.6 years (range: 21.0-64.4 years), 39% were African-American, and 11% were current smokers. Most participants were hrHPV-positive at enrollment (80.5%). Over one-third of cases regressed (n = 53, 35.1%). Median time-to-regression was 12.6 months (range: 4.5-24.0 months). Probability of CIN1 regression was negatively correlated with methylation at IGF2AS CpG 5 (HR = 0.41; 95% CI = 0.23-0.77) and PEG10 DMR (HR = 0.80; 95% CI = 0.65-0.98). Altered methylation of imprinted IGF2AS and PEG10 DMRs may play a role in the natural history of CIN1. If confirmed in larger studies, further research on imprinted gene DMR methylation is warranted to determine its efficacy as a biomarker for cervical cancer screening.

Isobe T, Seki M, Yoshida K, et al.
Integrated Molecular Characterization of the Lethal Pediatric Cancer Pancreatoblastoma.
Cancer Res. 2018; 78(4):865-876 [PubMed] Related Publications
Pancreatoblastoma is a rare pediatric pancreatic malignancy for which the molecular pathogenesis is not understood. In this study, we report the findings of an integrated multiomics study of whole-exome and RNA sequencing as well as genome-wide copy number and methylation analyses of ten pancreatoblastoma cases. The pancreatoblastoma genome was characterized by a high frequency of aberrant activation of the Wnt signaling pathway, either via somatic mutations of

Unger C, Kramer N, Unterleuthner D, et al.
Stromal-derived IGF2 promotes colon cancer progression via paracrine and autocrine mechanisms.
Oncogene. 2017; 36(38):5341-5355 [PubMed] Related Publications
The insulin-like growth factor (IGF)2/IGF1 receptor (IGF1R) signaling axis has an important role in intestinal carcinogenesis and overexpression of IGF2 is an accepted risk factor for colorectal cancer (CRC) development. Genetic amplifications and loss of imprinting contribute to the upregulation of IGF2, but insufficiently explain the extent of IGF2 expression in a subset of patients. Here, we show that IGF2 was specifically induced in the tumor stroma of CRC and identified cancer-associated fibroblasts (CAFs) as the major source. Further, we provide functional evidence that stromal IGF2, via the paracrine IGF1R/insulin receptor axis, activated pro-survival AKT signaling in CRC cell lines. In addition to its effects on malignant cells, autocrine IGF2/IGF1R signaling in CAFs induced myofibroblast differentiation in terms of alpha-smooth muscle actin expression and contractility in floating collagen gels. This was further augmented in concert with transforming growth factor-β (TGFβ) signaling suggesting a cooperative mechanism. However, we demonstrated that IGF2 neither induced TGFβ/smooth muscle actin/mothers against decapentaplegic (SMAD) signaling nor synergized with TGFβ to hyperactivate this pathway in two dimensional and three dimensional cultures. IGF2-mediated physical matrix remodeling by CAFs, but not changes in extracellular matrix-modifying proteases or other secreted factors acting in a paracrine manner on/in cancer cells, facilitated subsequent tumor cell invasion in organotypic co-cultures. Consistently, colon cancer cells co-inoculated with CAFs expressing endogenous IGF2 in mouse xenograft models exhibited elevated invasiveness and dissemination capacity, as well as increased local tumor regrowth after primary tumor resection compared with conditions with IGF2-deficient CAFs. In line, expression of IGF2 correlated with elevated relapse rates and poor survival in CRC patients. In agreement with our results, high-level coexpression of IGF2 and TGFβ was predicting adverse outcome with higher accuracy than increased expression of the individual genes alone. Taken together, we demonstrate that stroma-induced IGF2 promotes colon cancer progression in a paracrine and autocrine manner and propose IGF2 as potential target for tumor stroma cotargeting strategies.

Lee J, Jung JH, Chae YS, et al.
Long Noncoding RNA snaR Regulates Proliferation, Migration and Invasion of Triple-negative Breast Cancer Cells.
Anticancer Res. 2016; 36(12):6289-6295 [PubMed] Related Publications
AIM: We evaluated the role of long noncoding ribonucleic acid (lncRNA) in breast cancer cell lines by quantitative reverse transcription-polymerase change reaction.
MATERIALS AND METHODS: The effects of small NF90-associated RNA (snaR) with RNA interference on proliferation, migration and invasion of MDA-MB-231 cells were observed by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide, wound healing and transwell assay.
RESULTS: Among 90 lncRNAs, E2F transcription factor 4, p107/p130-binding (E2F4) antisense, insulin-like growth factor 2 antisense (IGF2AS), snaR, and small nucleolar RNA host gene 5 (SNHG5) were up-regulated in MDA-MB-231 and 7SK, antisense noncoding RNA in the INK4 locus (ANRIL), IGF2AS, Nespas, p53 mRNA, and snaR were up-regulated in MCF-7 cells. Down-regulation of snaR inhibited the proliferation, migration, and invasion of MDA-MD-231 breast cancer cells.
CONCLUSION: LncRNA snaR was found to be up-regulated in breast cancer cells, and the cancer progression of MDA-MB-231 cells was significantly suppressed by down-regulation of snaR. Therefore, snaR knockdown has potential as a treatment modality for triple-negative breast cancer.

Weischenfeldt J, Dubash T, Drainas AP, et al.
Pan-cancer analysis of somatic copy-number alterations implicates IRS4 and IGF2 in enhancer hijacking.
Nat Genet. 2017; 49(1):65-74 [PubMed] Free Access to Full Article Related Publications
Extensive prior research focused on somatic copy-number alterations (SCNAs) affecting cancer genes, yet the extent to which recurrent SCNAs exert their influence through rearrangement of cis-regulatory elements (CREs) remains unclear. Here we present a framework for inferring cancer-related gene overexpression resulting from CRE reorganization (e.g., enhancer hijacking) by integrating SCNAs, gene expression data and information on topologically associating domains (TADs). Analysis of 7,416 cancer genomes uncovered several pan-cancer candidate genes, including IRS4, SMARCA1 and TERT. We demonstrate that IRS4 overexpression in lung cancer is associated with recurrent deletions in cis, and we present evidence supporting a tumor-promoting role. We additionally pursued cancer-type-specific analyses and uncovered IGF2 as a target for enhancer hijacking in colorectal cancer. Recurrent tandem duplications intersecting with a TAD boundary mediate de novo formation of a 3D contact domain comprising IGF2 and a lineage-specific super-enhancer, resulting in high-level gene activation. Our framework enables systematic inference of CRE rearrangements mediating dysregulation in cancer.

Dong Y, Li J, Han F, et al.
High IGF2 expression is associated with poor clinical outcome in human ovarian cancer.
Oncol Rep. 2015; 34(2):936-42 [PubMed] Related Publications
Ovarian cancer is one of the most common types of cancer in females and is the leading cause of death among gynaecological cancers in women worldwide. In the present study, we identified insulin-like growth factor 2 (IGF2) as a differentially expressed gene between cancerous and non-cancerous ovarian tissues. IGF2 was frequently increased in the human ovarian cancers when compared to the frequency in the non-cancerous ovarian tissues both at the mRNA (30/35) and protein level (61/72). The mean level of IGF2 in the tumor tissues was markedly higher than that in the non-cancerous tissues (nearly 3-fold change) (P=0.000). There was a significant correlation of IGF2 expression with histological grade (P=0.047). Kaplan-Meier analysis indicated that the ovarian cancer patients with high IGF2 expression showed a poorer prognosis both in regards to overall survival (OS) and progression-free survival (PFS) (n=1,648, P=0.000). Further analysis revealed that high expression of IGF2 was an unfavorable factor for the prognosis of the ovarian cancer patients at clinical stage I + II, stage III, histological grade 2, grade 3 or those treated with chemotherapy containing platin and Taxol. Our data provide evidence that IGF2 expression is frequently increased in ovarian cancer tissues, and high expression of IGF2 may be a significant prognostic factor for poor survival in ovarian cancer patients.

Nunes M, Vrignaud P, Vacher S, et al.
Evaluating patient-derived colorectal cancer xenografts as preclinical models by comparison with patient clinical data.
Cancer Res. 2015; 75(8):1560-6 [PubMed] Related Publications
Development of targeted therapeutics required translationally relevant preclinical models with well-characterized cancer genome alterations. Here, by studying 52 colorectal patient-derived tumor xenografts (PDX), we examined key molecular alterations of the IGF2-PI3K and ERBB-RAS pathways and response to cetuximab. PDX molecular data were compared with that published for patient colorectal tumors in The Cancer Genome Atlas. We demonstrated a significant pattern of mutual exclusivity of genomic abnormalities in the IGF2-PI3K and ERBB-RAS pathways. The genomic anomaly frequencies observed in microsatellite stable PDX reproduce those detected in nonhypermutated patient tumors. We found frequent IGF2 upregulation (16%), which was mutually exclusive with IRS2, PIK3CA, PTEN, and INPP4B alterations, supporting IGF2 as a potential drug target. In addition to maintaining the genomic and histologic diversity, correct preclinical models need to reproduce drug response observed in patients. Responses of PDXs to cetuximab recapitulate also clinical data in patients, with partial or complete response in 15% (8 of 52) of PDXs and response strictly restricted to KRAS wild-type models. The response rate reaches 53% (8 of 15) when KRAS, BRAF, and NRAS mutations are concomitantly excluded, proving a functional cross-validation of predictive biomarkers obtained retrospectively in patients. Collectively, these results show that, because of their clinical relevance, colorectal PDXs are appropriate tools to identify both new targets, like IGF2, and predictive biomarkers of response/resistance to targeted therapies.

Zanella ER, Galimi F, Sassi F, et al.
IGF2 is an actionable target that identifies a distinct subpopulation of colorectal cancer patients with marginal response to anti-EGFR therapies.
Sci Transl Med. 2015; 7(272):272ra12 [PubMed] Related Publications
Among patients with colorectal cancer who benefit from therapy targeted to the epidermal growth factor receptor (EGFR), stable disease (SD) occurs more frequently than massive regressions. Exploring the mechanisms of this incomplete sensitivity to devise more efficacious treatments will likely improve patients' outcomes. We tested therapies tailored around hypothesis-generating molecular features in patient-derived xenografts ("xenopatients"), which originated from 125 independent samples that did not harbor established resistance-conferring mutations. Samples from xenopatients that responded to cetuximab, an anti-EGFR agent, with disease stabilization displayed high levels of EGFR family ligands and receptors, indicating high EGFR pathway activity. Five of 21 SD models (23.8%) characterized by particularly high expression of EGFR and EGFR family members regressed after intensified EGFR blockade by cetuximab and a small-molecule inhibitor. In addition, a subset of cases in which enhanced EGFR inhibition was unproductive (6 of 16, 37.5%) exhibited marked overexpression of insulin-like growth factor 2 (IGF2). Enrichment of IGF2 overexpressors among cases with SD was demonstrated in the entire xenopatient collection and was confirmed in patients by mining clinical gene expression data sets. In functional studies, IGF2 overproduction attenuated the efficacy of cetuximab. Conversely, interception of IGF2-dependent signaling in IGF2-overexpressing xenopatients potentiated the effects of cetuximab. The clinical implementation of IGF inhibitors awaits reliable predictors of response, but the results of this study suggest rational combination therapies for colorectal cancer and provide evidence for IGF2 as a biomarker of reduced tumor sensitivity to anti-EGFR therapy and a determinant of response to combined IGF2/EGFR targeting.

Cao Y, Lindström S, Schumacher F, et al.
Insulin-like growth factor pathway genetic polymorphisms, circulating IGF1 and IGFBP3, and prostate cancer survival.
J Natl Cancer Inst. 2014; 106(6):dju085 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The insulin-like growth factor (IGF) signaling pathway has been implicated in prostate cancer (PCa) initiation, but its role in progression remains unknown.
METHODS: Among 5887 PCa patients (704 PCa deaths) of European ancestry from seven cohorts in the National Cancer Institute Breast and Prostate Cancer Cohort Consortium, we conducted Cox kernel machine pathway analysis to evaluate whether 530 tagging single nucleotide polymorphisms (SNPs) in 26 IGF pathway-related genes were collectively associated with PCa mortality. We also conducted SNP-specific analysis using stratified Cox models adjusting for multiple testing. In 2424 patients (313 PCa deaths), we evaluated the association of prediagnostic circulating IGF1 and IGFBP3 levels and PCa mortality. All statistical tests were two-sided.
RESULTS: The IGF signaling pathway was associated with PCa mortality (P = .03), and IGF2-AS and SSTR2 were the main contributors (both P = .04). In SNP-specific analysis, 36 SNPs were associated with PCa mortality with P trend less than .05, but only three SNPs in the IGF2-AS remained statistically significant after gene-based corrections. Two were in linkage disequilibrium (r 2 = 1 for rs1004446 and rs3741211), whereas the third, rs4366464, was independent (r 2 = 0.03). The hazard ratios (HRs) per each additional risk allele were 1.19 (95% confidence interval [CI] = 1.06 to 1.34; P trend = .003) for rs3741211 and 1.44 (95% CI = 1.20 to 1.73; P trend < .001) for rs4366464. rs4366464 remained statistically significant after correction for all SNPs (P trend.corr = .04). Prediagnostic IGF1 (HRhighest vs lowest quartile = 0.71; 95% CI = 0.48 to 1.04) and IGFBP3 (HR = 0.93; 95% CI = 0.65 to 1.34) levels were not associated with PCa mortality.
CONCLUSIONS: The IGF signaling pathway, primarily IGF2-AS and SSTR2 genes, may be important in PCa survival.

Gao W, Gu Y, Li Z, et al.
miR-615-5p is epigenetically inactivated and functions as a tumor suppressor in pancreatic ductal adenocarcinoma.
Oncogene. 2015; 34(13):1629-40 [PubMed] Related Publications
Pancreatic ductal adenocarcinoma (PDAC) is a highly invasive cancer with a poor prognosis. Although microRNA (miRNA) transcripts have a crucial role in carcinogenesis and development, little information is known regarding the aberrant DNA methylation of miRNAs in PDAC. Using methylated DNA immunoprecipitation-chip analysis, we found that miR-615-5p was hypermethylated in its putative promoter region, which silenced its expression in PDAC cell lines. In addition, the overexpression of miR-615-5p in pancreatic cancer cells suppressed cell proliferation, migration and invasion. Insulin-like growth factor 2 (IGF2) is an imprinted gene, and its abnormal expression contributes to tumor growth. Here, we identified IGF2 as a target of miR-615-5p using a luciferase reporter assay. IGF2 upregulation in PDAC tissues was not correlated with a loss of imprinting but was inversely correlated with miR-615-5p downregulation. In addition, miR-615-5p suppressed pancreatic cancer cell proliferation, migration and invasion by directly targeting IGF2, and this effect could be reversed by co-transfection with IGF2. Furthermore, the stable overexpression of miR-615-5p inhibited tumor growth in vivo and was correlated with IGF2 expression. Using RNA sequencing, we further identified miR-615-5p as potentially targeting other genes, such as the proto-oncogene JUNB, and interfering with the insulin signaling pathway. Taken together, our results demonstrate that miR-615-5p was abnormally downregulated in PDAC cells due to promoter hypermethylation, which limited its inhibition of IGF2 and other target genes, thereby contributing to tumor growth, invasion and migration. These data demonstrate a novel and important role of miR-615-5p as a tumor suppressor in PDAC.

Jacobs DI, Hansen J, Fu A, et al.
Methylation alterations at imprinted genes detected among long-term shiftworkers.
Environ Mol Mutagen. 2013; 54(2):141-6 [PubMed] Free Access to Full Article Related Publications
Exposure to light at night through shiftwork has been linked to alterations in DNA methylation and increased risk of cancer development. Using an Illumina Infinium Methylation Assay, we analyzed methylation levels of 397 CpG sites in the promoter regions of 56 normally imprinted genes to investigate whether shiftwork is associated with alteration of methylation patterns. Methylation was significantly higher at 20 CpG sites and significantly lower at 30 CpG sites (P < 0.05) in 10 female long-term shiftworkers as compared to 10 female age- and folate intake-matched day workers. The strongest evidence for altered methylation patterns in shiftworkers was observed for DLX5, IGF2AS, and TP73 based on the magnitude of methylation change and consistency in the direction of change across multiple CpG sites, and consistent results were observed using quantitative DNA methylation analysis. We conclude that long-term shiftwork may alter methylation patterns at imprinted genes, which may be an important mechanism by which shiftwork has carcinogenic potential and warrants further investigation.

Simon DP, Hammer GD
Adrenocortical stem and progenitor cells: implications for adrenocortical carcinoma.
Mol Cell Endocrinol. 2012; 351(1):2-11 [PubMed] Free Access to Full Article Related Publications
The continuous centripetal repopulation of the adrenal cortex is consistent with a population of cells endowed with the stem/progenitor cell properties of self-renewal and pluripotency. The adrenocortical capsule and underlying undifferentiated cortical cells are emerging as critical components of the stem/progenitor cell niche. Recent genetic analysis has identified various signaling pathways including Sonic Hedgehog (Shh) and Wnt as crucial mediators of adrenocortical lineage and organ homeostasis. Shh expression is restricted to the peripheral cortical cells that express a paucity of steroidogenic genes but give rise to the underlying differentiated cells of the cortex. Wnt/β-catenin signaling maintains the undifferentiated state and adrenal fate of adrenocortical stem/progenitor cells, in part through induction of its target genes Dax1 and inhibin-α, respectively. The pathogenesis of ACC, a rare yet highly aggressive cancer with an extremely poor prognosis, is slowly emerging from studies of the stem/progenitor cells of the adrenal cortex coupled with the genetics of familial syndromes in which ACC occurs. The frequent observation of constitutive activation of Wnt signaling due to loss-of-function mutations in the tumor suppressor gene APC or gain-of-function mutation in β-catenin in both adenomas and carcinomas, suggests perhaps that the Wnt pathway serves an early or initiating insult in the oncogenic process. Loss of p53 might be predicted to cooperate with additional genetic insults such as IGF2 as both are the most common genetic abnormalities in malignant versus benign adrenocortical neoplasms. It is unclear whether other factors such as Pod1 and Pref1, which are implicated in stem/progenitor cell biology in the adrenal and/or other organs, are also implicated in the etiology of adrenocortical carcinoma. The rarity and heterogeneous presentation of ACC makes it difficult to identify the cellular origin and the molecular progression to cancer. A more complete understanding of adrenocortical stem/progenitor cell biology will invariably aid in characterization of the molecular details of ACC tumorigenesis and may offer new options for therapeutic intervention.

Hoshida Y
Molecular signatures and prognosis of hepatocellular carcinoma.
Minerva Gastroenterol Dietol. 2011; 57(3):311-22 [PubMed] Related Publications
Prognostic prediction is a vital component in clinical management of hepatocellular carcinoma (HCC) patients. Rapidly evolving genomic assays serve as flexible sources to discover molecular signatures that sensitively and specifically predict clinical outcome of the patients. Studies have identified molecular signatures of HCC tumors that depict biological aggressiveness yielded through activation of specific genes and molecular pathways such as MYC, AKT, TGF-beta, and IGF2 as well as inactivation of TP53 pathway. Despite the promise for tumor-derived signatures' role in therapeutic target discovery, their value as prognostic marker seems to be limited especially in early-stage HCC, which has been increasing as a result of successful implementation HCC surveillance for patients with liver cirrhosis. In contrast, non-tumor, diseased liver tissues turn out to be a rich source of molecular information to capture propensity to hepatocarcinogenesis and metastasis through dyregulation of growth signaling and inflammatory/oxidative stress/immune response. In addition, the liver-derived signatures hold prognostic relevance irrespective of HCC stage, suggesting their role as prognostic markers. Furthermore, they may also be utilized for development of HCC chemoprevention therapy.

Chava S, Mohan V, Shetty PJ, et al.
Immunohistochemical evaluation of p53, FHIT, and IGF2 gene expression in esophageal cancer.
Dis Esophagus. 2012; 25(1):81-7 [PubMed] Related Publications
The aim of the study was to evaluate the expression of tumor suppressor genes p53, fragile histidine triad gene (FHIT), and an oncogene insulin-like growth factor 2 (IGF2) as prognostic markers in the etiology of esophageal cancer. Immunohistochemistry (IHC) was performed in 39 archival tissue samples of different esophageal pathologies for the three genes. Abnormal p53 expression was maximum in all the cases of squamous cell carcinoma, while IGF2 expression was enhanced in squamous cell carcinoma (81%), adenocarcinoma (100%), and dysplasia of squamous epithelium (75%) samples when compared with normals (50%). To our surprise, 75% of normal tissues did not show FHIT expression, which was also not seen in 40% of dysplasias of squamous epithelium, 33.3% of adenocarcinoma, and 41% of squamous cell carcinoma. To the best of our knowledge, this is the first study evaluating IGF2 by IHC, as well as, correlating it with the expression of the two tumor suppressor genes, p53 and FHIT, in esophageal tissue. p53 expression was threefold higher than normal in dysplasias of squamous epithelium and adenocarcinoma, while it was eightfold higher in squamous cell carcinoma. IGF2 expression was low in normal and dysplasia tissue but was increased 1.97-fold in both types of malignancy. FHIT and p53 expression were well correlated in squamous cell carcinoma, supporting the observation that FHIT regulates and stabilizes p53. Altered/lowered FHIT levels may be a result of exposure to various exogenous agents; however, this could not be assessed in the present study as it was carried out on archival samples. A larger prospective study is warranted to establish the role of exogenous factors in FHIT expression.

Meyer-Rochow GY, Jackson NE, Conaglen JV, et al.
MicroRNA profiling of benign and malignant pheochromocytomas identifies novel diagnostic and therapeutic targets.
Endocr Relat Cancer. 2010; 17(3):835-46 [PubMed] Related Publications
MicroRNAs (miRNAs) are small RNAs ( approximately 22 bp) that post-transcriptionally regulate protein expression and are found to be differentially expressed in a number of human cancers. There is increasing evidence to suggest that miRNAs could be useful in cancer diagnosis, prognosis, and therapy. We performed miRNA microarray expression profiling on a cohort of 12 benign and 12 malignant pheochromocytomas and identified a number of differentially expressed miRNAs. These results were validated in a separate cohort of ten benign and ten malignant samples using real-time quantitative RT-PCR; benign samples had a minimum follow-up of at least 2 years. It was found that IGF2 as well as its intronic miR-483-5p was over-expressed, while miR-15a and miR-16 were under-expressed in malignant tumours compared with benign tumours. These miRNAs were found to be diagnostic and prognostic markers for malignant pheochromocytoma. The functional role of miR-15a and miR-16 was investigated in vitro in the rat PC12 pheochromocytoma cell line, and these miRNAs were found to regulate cell proliferation via their effect on cyclin D1 and apoptosis. These data indicate that miRNAs play a pivotal role in the biology of malignant pheochromocytoma, and represent an important class of diagnostic and prognostic biomarkers and therapeutic targets warranting further investigation.

Mutskov V, Felsenfeld G
The human insulin gene is part of a large open chromatin domain specific for human islets.
Proc Natl Acad Sci U S A. 2009; 106(41):17419-24 [PubMed] Free Access to Full Article Related Publications
Knowledge of how insulin (INS) gene expression is regulated will lead to better understanding of normal and abnormal pancreatic beta cell function. We have mapped histone modifications over the INS region, coupled with an expression profile, in freshly isolated islets from multiple human donors. Unlike many other human genes, in which active modifications tend to be concentrated within 1 kb around the transcription start site, these marks are distributed over the entire coding region of INS as well. Moreover, a region of approximately 80 kb around the INS gene, which contains the {tyrosine hydroxylase (TH)-(INS)-insulin-like growth factor 2 antisense (IGF2AS)-insulin-like growth factor 2 (IGF2)} gene cluster, unusually is marked by almost uniformly elevated levels of histone acetylation and H3K4 dimethylation, extending both downstream into IGF2 and upstream beyond the TH gene. This is accompanied by islet specific coordinate expression with INS of the neighboring TH and IGF2 genes. The presence of islet specific intergenic transcripts suggests their possible function in the maintenance of this unusual large open chromatin domain.

Dejeux E, Olaso R, Dousset B, et al.
Hypermethylation of the IGF2 differentially methylated region 2 is a specific event in insulinomas leading to loss-of-imprinting and overexpression.
Endocr Relat Cancer. 2009; 16(3):939-52 [PubMed] Related Publications
Prediction of the evolution of endocrine pancreatic tumors remains difficult based on histological criteria alone. We have previously demonstrated that epigenetic changes are an early event in a mouse model developing insulinomas. Particularly, overexpression of the imprinted IGF2 was caused by the hypermethylation of CpGs in the differentially methylated region 2 (DMR2). Here, we investigated whether IGF2 hypermethylation is also observed in human insulinomas and whether this alteration is common to other human endocrine tumors of the pancreas and the digestive tract. We analyzed the methylation status of 40 CpGs located in the DMR0 and DMR2 of the IGF2 as well as in the H19 DMR by pyrosequencing in a cohort of 62 patients with pancreatic or small intestine endocrine tumors. Altered methylation patterns were observed in all tumor types for the different regions of IGF2, but not for H19. However, hypermethylation of the IGF2 DMR2 was specific for insulinomas and did not occur in any of the other types of tumors which were characterized by a loss of methylation in this region. Gain of methylation in the IGF2 DMR2 in insulinomas correlated with loss-of-imprinting and promoter 4 mediated overexpression of IGF2 at the RNA and protein level. Furthermore, a decreasing degree of methylation in the different regions of IGF2 correlated well with increasing degree of malignancy according to the WHO classification of pancreatic endocrine tumors (PETs), suggesting that methylation of IGF2 might be a useful biomarker for classification and staging of PETs.

Linhart HG, Lin H, Yamada Y, et al.
Dnmt3b promotes tumorigenesis in vivo by gene-specific de novo methylation and transcriptional silencing.
Genes Dev. 2007; 21(23):3110-22 [PubMed] Free Access to Full Article Related Publications
Increased methylation of CpG islands and silencing of affected target genes is frequently found in human cancer; however, in vivo the question of causality has only been addressed by loss-of-function studies. To directly evaluate the role and mechanism of de novo methylation in tumor development, we overexpressed the de novo DNA methyltransferases Dnmt3a1 and Dnmt3b1 in Apc Min/+ mice. We found that Dnmt3b1 enhanced the number of colon tumors in Apc Min/+ mice approximately twofold and increased the average size of colonic microadenomas, whereas Dnmt3a1 had no effect. The overexpression of Dnmt3b1 caused loss of imprinting and increased expression of Igf2 as well as methylation and transcriptional silencing of the tumor suppressor genes Sfrp2, Sfrp4, and Sfrp5. Importantly, we found that Dnmt3b1 but not Dnmt3a1 efficiently methylates the same set of genes in tumors and in nontumor tissues, demonstrating that de novo methyltransferases can initiate methylation and silencing of specific genes in phenotypically normal cells. This suggests that DNA methylation patterns in cancer are the result of specific targeting of at least some tumor suppressor genes rather than of random, stochastic methylation followed by clonal selection due to a proliferative advantage caused by tumor suppressor gene silencing.

Soroceanu L, Kharbanda S, Chen R, et al.
Identification of IGF2 signaling through phosphoinositide-3-kinase regulatory subunit 3 as a growth-promoting axis in glioblastoma.
Proc Natl Acad Sci U S A. 2007; 104(9):3466-71 [PubMed] Free Access to Full Article Related Publications
Amplification or overexpression of growth factor receptors is a frequent occurrence in malignant gliomas. Using both expression profiling and in situ hybridization, we identified insulin-like growth factor 2 (IGF2) as a marker for a subset of glioblastomas (GBMs) that lack amplification or overexpression of EGF receptor. Among 165 primary high-grade astrocytomas, 13% of grade IV tumors and 2% of grade III tumors expressed IGF2 mRNA levels >50-fold the sample population median. IGF2-overexpressing tumors frequently displayed PTEN loss, were highly proliferative, exhibited strong staining for phospho-Akt, and belonged to a subclass of GBMs characterized by poor survival. Using a serum-free culture system, we discovered that IGF2 can substitute for EGF to support the growth of GBM-derived neurospheres. The growth-promoting effects of IGF2 were mediated by the insulin-like growth factor receptor 1 and phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3), a regulatory subunit of phosphoinositide 3-kinase that shows genomic gains in some highly proliferative GBM cases. PIK3R3 knockdown inhibited IGF2-induced growth of GBM-derived neurospheres. The current results provide evidence that the IGF2-PIK3R3 signaling axis is involved in promoting the growth of a subclass of highly aggressive human GBMs that lack EGF receptor amplification. Our data underscore the importance of the phosphoinositide 3-kinase/Akt pathway for growth of high-grade gliomas and suggest that multiple molecular alterations that activate this signaling cascade may promote tumorigenesis. Further, these findings highlight the parallels between growth factors or receptors that are overexpressed in GBMs and those that support in vitro growth of tumor-derived stem-like cells.

Cui H
Loss of imprinting of IGF2 as an epigenetic marker for the risk of human cancer.
Dis Markers. 2007; 23(1-2):105-12 [PubMed] Free Access to Full Article Related Publications
IGF2 is the first gene discovered to be imprinted and expressed exclusively from the paternal allele in both human and mouse. IGF2 is also the first imprinted gene displaying loss of imprinting (LOI) or aberrant imprinting in human cancers. Evidently, LOI or reactivation of the maternal allele of IGF2 is associated with an increase of IGF2 expression that may subsequently play an important role in the onset of human cancers. The most important discovery was the association of LOI of IGF2 with the risk of developing human colorectal cancer. LOI occurs not only in colon cancer tissues, but also in matched normal tissues and peripheral blood cells. A pilot study indicated a significant relationship between LOI of IGF2 and family history as well as personal history of colorectal cancer, suggesting that LOI of IGF2 might be a valuable biomolecular marker of predicting an individual's risk for colon cancer. A recent epigenetic progenitor model suggested that human cancers might have a common basis that involves an epigenetic disruption of progenitor cells mediated by "tumor progenitor genes" and proposed that non-neoplastic but epigenetically disrupted progenitor cells might be an important target for cancer risk assessment and prevention.

Gallagher E, Mc Goldrick A, Chung WY, et al.
Gain of imprinting of SLC22A18 sense and antisense transcripts in human breast cancer.
Genomics. 2006; 88(1):12-7 [PubMed] Related Publications
The 11p15.5 region harbors three imprinted sense/antisense transcript pairs, SLC22A18/SLC22A18AS, IGF2/IGF2AS (PEG8), and KCNQ1/KCNQ1OT1 (LIT1). SLC22A18 (solute carrier family 22 (organic cation transporter) member 18) and its antisense transcript SLC22A18AS are paternally suppressed in fetal samples. In adult tissue, SLC22A18 displays polymorphic imprinting, but the imprinting status of SLC22A18AS remains elusive. SLC22AI8 DNA-PCR-RFLP analysis using NlaIII restriction digestion identified SLC22A18 heterozygotes within this breast tissue cohort (n = 89). Commercial sequencing identified informative SLC22A18AS samples. Random hexamer-primed cDNA synthesis, SLC22A18/SLC22A18AS-specific PCR, and imprinting evaluation by commercial sequencing demonstrated that SLC22A18AS displays a nonimprinted profile in reduction mastectomies (n = 6). However, SLC22A18 showed a gain of imprinting (GOI) in 1/4 of these normal cases. In the malignant cohort, GOI was also demonstrated in 18% for SLC22A18 and 14% for SLC22A18AS, occurring concomitantly in one case. This study reports the imprinting status of SLC22A18AS in adult tissue, and shows that GOI affects both the sense, and antisense transcripts at this locus in human breast tissue.

Vu TH, Chuyen NV, Li T, Hoffman AR
Loss of imprinting of IGF2 sense and antisense transcripts in Wilms' tumor.
Cancer Res. 2003; 63(8):1900-5 [PubMed] Related Publications
Human insulin-like growth factor II gene (IGF2) is overexpressed, and its imprinting is disrupted in many tumors, including Wilms' tumor. A transcript that is antisense to IGF2, IGF2-antisense (IGF2-AS), is transcribed from within IGF2 in a reverse orientation. This transcript is also maternally imprinted and overexpressed in Wilms' tumor. IGF2-AS was detected as a 2.2 kb mRNA in Hep 3B cells by Northern blotting, and it encodes a putative 168 amino acid peptide. An alternative splicing mRNA observed predominantly in adult liver encodes an additional putative 199 amino acid peptide. We have examined the expression of IGF2 and IGF2-AS in normal tissue, breast and ovarian tumors, and 25 informative, well-characterized Wilms' tumors and determined the relationship between IGF2 and IGF2-AS imprinting. IGF2-AS was expressed at levels comparable with IGF2 sense expression derived from promoters P1 and P2 in normal tissue and in breast, ovarian, and Wilms' tumor tissues. In Wilms' tumors that demonstrate maintenance of imprinting of IGF2, IGF2-AS was imprinted. In contrast, in tumors which demonstrate LOI of IGF2, only two of six tumors showed loss of imprinting of IGF2-AS, whereas four of six tumors demonstrated maintenance of imprinting for IGF2-AS. The discrepancy between IGF2 and IGF2-AS loss of imprinting in some tumors demonstrates the control complexity of the imprinting status of the various transcripts derived from the IGF2 gene.

Nishihara S, Hayashida T, Mitsuya K, et al.
Multipoint imprinting analysis in sporadic colorectal cancers with and without microsatellite instability.
Int J Oncol. 2000; 17(2):317-22 [PubMed] Related Publications
Disrupted imprinting is implicated in certain tumorigenesis. Since aberrant methylation has been described for a majority of microsatellite instability (MSI)-positive sporadic colorectal cancers, we have investigated alteration to the imprinting in 55 sporadic colorectal cancers with or without MSI. Loss of imprinting (LOI) of IGF2 and PEG1/MEST was observed in 42% and 35% of informative cancers, respectively. H19 expression was not detected in 24% of informative cancers. SNRPN and NDN retained monoallelic expression in all the cancers examined. These findings indicate no simultaneous disruption of the imprinted genes. LOI of IGF2 and PEG1/MEST was also observed in colorectal mucosa from almost all the patients with LOI in tumor tissue. Moreover, MSI-positive colorectal cancers exhibit LOI of IGF2 with a high frequency compared to MSI-negative cancers (P=0.013). These observations, consistent with a previous report, establish an association between LOI of IGF2 and MSI in colorectal cancers and provide insight into susceptibility of tumor development.

Okutsu T, Kuroiwa Y, Kagitani F, et al.
Expression and imprinting status of human PEG8/IGF2AS, a paternally expressed antisense transcript from the IGF2 locus, in Wilms' tumors.
J Biochem. 2000; 127(3):475-83 [PubMed] Related Publications
A large imprinted gene cluster in human chromosome 11p15.5 has been implicated in Beckwith-Wiedemann syndrome and Wilms' tumor. We have identified a paternally expressed imprinted gene, PEG8/IGF2AS, in this locus. It is transcribed in the opposite direction to the IGF2 transcripts and some genomic regions are shared with the IGF2 gene, as in the case of the mouse imprinted Igf2as gene reported previously by T. Moore et al. As to the relationship between these genomic regions, the human and mouse genes are very similar but there is no homology in their middle parts. Interestingly, PEG8/IGF2AS and IGF2 were found to be overexpressed in Wilms' tumor samples, at levels over ten and a hundred times higher than that in normal kidney tissues neighboring the tumors, respectively. These findings indicate that PEG8/IGF2AS is a good marker of Wilms' tumor and also suggest the possibility of PEG8/IGF2AS being one of the candidate Wilms' tumor genes.

Li X, Nong Z, Ekström C, et al.
Disrupted IGF2 promoter control by silencing of promoter P1 in human hepatocellular carcinoma.
Cancer Res. 1997; 57(10):2048-54 [PubMed] Related Publications
Previous investigations have supported or indicated a stimulatory role of the insulin-like growth factor II gene (IGF2) in hepatocarcinogenesis. We have studied the transcript levels, promoter usage, and imprinting status of the ICF2 gene and its relationship to H19 in human hepatocellular carcinomas (HCCs) and liver tumor cell lines. The activity of the IGF2 promoter P1 was lost in about 70% of the cases (18 of 25). This is the most prominent abnormality regarding the IGF2 regulation in this study. Total IGF2 as well as promoter P3 transcription were up-regulated in a small group of the tumors. Twenty genetically informative cases were obtained from 26 cases, thus excluding the probability of loss of heterozygosity of the IGF2 gene. Among these, nine showed abnormal monoallelic expression of IGF2. One HCC and one HCC cell line proved loss of functional imprinting of IGF2. H19 and IGF2 were regulated in parallel, and expression levels were variable. Taken together, the disruption of the IGF2 promoter regulation, particularly the loss of P1 activity, is a common feature of human HCCs. The loss of P1 activity explains the frequent loss of biallelic IGF2 expression and may potentially be used as a diagnostic or monitoring marker for human HCC.

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