The Role of Insulin-Like Growth Factor 2 and Its Receptors in Human Tumors

Identification of Candidate Biomarkers and Prognostic Analysis in Colorectal Cancer Liver Metastases

Background

Colorectal cancer (CRC), one of the most common malignant tumors worldwide, has a high mortality rate, especially for patients with CRC liver metastasis (CLM). However, CLM pathogenesis remains unclear.

Methods

We integrated multiple cohort datasets and databases to clarify and verify potential key candidate biomarkers and signal transduction pathways in CLM. GEO2R, DAVID 6.8, ImageGP, STRING, UALCAN, ONCOMINE, THE HUMAN PROTEIN ATLAS, GEPIA 2.0, cBioPortal, TIMER 2.0, DRUGSURV, CRN, GSEA 4.0.3, FUNRICH 3.1.3 and R 4.0.3 were utilized in this study.

Results

Sixty-three pairs of matched colorectal primary cancer and liver metastatic gene expression profiles were screened from three gene expression profiles (GSE6988, GSE14297 and GSE81558). Thirty-one up-regulated genes and four down-regulated genes were identified from these three gene expression profiles and verified by another gene expression profiles (GSE 49355) and TCGA database. Two pathways (IGFBP-IGF signaling pathway and complement-coagulation cascade), eighteen key differentially expressed genes (DEGs), six hub genes (SPARCL1, CDH2, CP, HP, TF and SERPINA5) and two biomarkers (CDH2 and SPARCL1) with significantly prognostic values were screened by multi-omics data analysis and verified by Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) cohort.

Conclusions

In this study, we identified a robust set of potential candidate biomarkers in CLM, which would provide potential value for early diagnosis and prognosis, and would promote molecular targeting therapy for CRC and CLM.

Insulin-Like Growth Factor 2 (IGF2) Signaling in Colorectal Cancer-From Basic Research to Potential Clinical Applications

Colorectal cancer (CRC) is one of the most common cancers in men and women worldwide as well as is the leading cause of death in the western world. Almost a third of the patients has or will develop liver metastases. While genetic as well as epigenetic mechanisms are important in CRC pathogenesis, the basis of the most cases of cancer is unknown. High spatial and inter-patient variability of the molecular alterations qualifies this cancer in the group of highly heterogeneous tumors, which makes it harder to elucidate the mechanisms underlying CRC progression. Determination of highly sensitive and specific early diagnosis markers and understanding the cellular and molecular mechanism(s) of cancer progression are still a challenge of the current era in oncology of solid tumors. One of the accepted risk factors for CRC development is overexpression of insulin-like growth factor 2 (IGF2), a 7.5-kDa peptide produced by liver and many other tissues. IGF2 is the first gene discovered to be parentally imprinted. Loss of imprinting (LOI) or aberrant imprinting of IGF2 could lead to IGF2 overexpression, increased cell proliferation, and CRC development. IGF2 as a mitogen is associated with increased risk of developing colorectal neoplasia. Higher serum IGF2 concentration as well as its tissue overexpression in CRC compared to control are associated with metastasis. IGF2 protein was one of the three candidates for a selective marker of CRC progression and staging. Recent research indicates dysregulation of different micro- and long non-coding RNAs (miRNAs and lncRNAs, respectively) embedded within the IGF2 gene in CRC carcinogenesis, with some of them indicated as potential diagnostic and prognostic CRC biomarkers. This review systematises the knowledge on the role of genetic and epigenetic instabilities of IGF2 gene, free (active form of IGF2) and IGF-binding protein (IGFBP) bound (inactive form), paracrine/autocrine secretion of IGF2, as well as mechanisms of inducing dysplasia in vitro and tumorigenicity in vivo. We have tried to answer which molecular changes of the IGF2 gene and its regulatory mechanisms have the most significance in initiation, progression (including liver metastasis), prognosis, and potential anti-IGF2 therapy in CRC patients.

Analysis of porcine IGF2 gene expression in adipose tissue and its effect on fatty acid composition

IGF2:g.3072G>A polymorphism has been described as the causal mutation of a maternally imprinted QTL for muscle growth and fat deposition in pigs. The objective of the current work was to study the association between the IGF2:g.3072G>A polymorphism and the IGF2 gene expression and its effect on fatty acid composition in adipose tissue in different pig genetic backgrounds. A cis-eQTL region associated with the IGF2 mRNA expression in adipose tissue was identified in an eGWAS with 355 animals. The IGF2 gene was located in this genomic interval and IGF2g.3072G>A was the most significant SNP, explaining a 25% of the gene expression variance. Significant associations between IGF2:g.3072G>A polymorphism and oleic (C18:1(n-9); p-value = 4.18x10^-07), hexadecanoic (C16:1(n-9); p-value = 4.04x10^-07), linoleic (C18:2(n-6); p-value = 6.44x10^-09), α-linoleic (C18:3(n-3); p-value = 3.30x10^-06), arachidonic (C20:4(n-6); p-value = 9.82x10^-08) FAs and the MUFA/PUFA ratio (p-value = 2.51x10^-9) measured in backfat were identified. Animals carrying the A allele showed an increase in IGF2 gene expression and higher PUFA and lower MUFA content. However, in additional studies was observed that there could be other proximal genetic variants affecting FA composition in adipose tissue. Finally, no differences in the IGF2 gene expression in adipose tissue were found between heterozygous animals classified according to the IGF2:g.3072G>A allele inherited from the father (A^PG^M or A^MG^P). However, pyrosequencing analysis revealed that there is imprinting of the IGF2 gene in muscle and adipose tissues, with stronger differences among the paternally and maternally inherited alleles in muscle. Our results suggested that IGF2:g.3072G>A polymorphism plays an important role in the regulation of IGF2 gene expression and can be involved in the fatty acid composition in adipose tissue. In both cases, further studies are still needed to deepen the mechanism of regulation of IGF2 gene expression in adipose tissue and the IGF2 role in FA composition.

Decreased IDE and IGF2 expression but increased Aβ40 in the cerebral cortex of mouse pups by early life lead exposure

As the abbreviation of plumbum and a chemical symbol for lead, Pb produces neurotoxic effects, which result into an impairment of learning and memory and other neurological dysfunctions. However, the mechanism of neurotoxicity of Pb exposure is unclear. The present study was undertaken to investigate the effects of maternal lead exposure on expression of insulin-degrading enzyme (IDE),insulin-like growth factor 2 (IGF2) and beta amyloid protein 40 (Aβ40) in the cerebral cortex of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.2% and 0.5% groups respectively. On the 21st postnatal day, On the PND21, the learning and memory ability were tested by water maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IDE, IGF2 and Aβ40 in cerebral cortex was examined by immunohistochemistry, immunofluorescence and western blotting. The lead levels in blood and cerebral cortex of all lead exposure groups were significantly higher than that of the control group (P<0.05). In water maze test, the performances of 0.5% and 1% lead exposure groups were worse than that of the control group (P<0.05).The expression of IDE and IGF2 was decreased, but Aβ40 was increased in lead exposed groups than that of the control group (P<0.05). The decreased expression of IDE and IGF2 and increased expression of Aβ40 in the cerebral cortex of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Genetic association study between INSULIN pathway related genes and high myopia in a Han Chinese population

To investigate the association between insulin (INS) pathway related genes, including INS, insulin receptor (INSR), insulin receptor substrate 1 (IRS1), insulin-like growth factor 2 (IGF2), IGF2 receptor (IGF2R) and IGF binding protein 1 (IGFBP1), and high myopia (HM) in a Han Chinese population, we have genotyped 24 single nucleotide polymorphisms (SNPs) of these genes in this cohort by Sequenom MassARRAY method. The genotyping data was analyzed by χ(2) test and the linkage disequilibrium block structure was examined by Haploview software. SNPs in the INS-IGF2 region (rs2070762 and rs1003483), and the INSR gene (rs3745551 and rs2229429) showed significant association with HM (allelic P = 0.0085, 0.0494, 0.0171 and 0.0238, respectively). Under the model of risk genotype combination of INSR and IRS1, carrying the variant allele (A) of the IRS1 Gly972Arg SNP (rs1801278) further increased the risk among the rs2229429T allele carriers (odds ratio 6.865, 95 % confidence interval 1.533-30.745). None of the SNPs in the IGF2R and IGFBP1 genes were found to be significantly associated with HM. Genetic variants in the insulin signaling pathway genes may increase the susceptibility of high myopia in Han Chinese.

Role of receptor tyrosine kinases and their ligands in glioblastoma

Glioblastoma multiforme is the most frequent, aggressive and fatal type of brain tumor. Glioblastomas are characterized by their infiltrating nature, high proliferation rate and resistance to chemotherapy and radiation. Recently, oncologic therapy experienced a rapid evolution towards “targeted therapy,” which is the employment of drugs directed against particular targets that play essential roles in proliferation, survival and invasiveness of cancer cells. A number of molecules involved in signal transduction pathways are used as molecular targets for the treatment of various tumors. In fact, inhibitors of these molecules have already entered the clinic or are undergoing clinical trials. Cellular receptors are clear examples of such targets and in the case of glioblastoma multiforme, some of these receptors and their ligands have become relevant. In this review, the importance of glioblastoma multiforme in signaling pathways initiated by extracellular tyrosine kinase receptors such as EGFR, PDGFR and IGF-1R will be discussed. We will describe their ligands, family members, structure, activation mechanism, downstream molecules, as well as the interaction among these pathways. Lastly, we will provide an up-to-date review of the current targeted therapies in cancer, in particular glioblastoma that employ inhibitors of these pathways and their benefits.

Molecular mechanisms of muscle plasticity with exercise

The skeletal muscle phenotype is subject to considerable malleability depending on use. Low-intensity endurance type exercise leads to qualitative changes of muscle tissue characterized mainly by an increase in structures supporting oxygen delivery and consumption. High-load strength-type exercise leads to growth of muscle fibers dominated by an increase in contractile proteins. In low-intensity exercise, stress-induced signaling leads to transcriptional upregulation of a multitude of genes with Ca(2+) signaling and the energy status of the muscle cells sensed through AMPK being major input determinants. Several parallel signaling pathways converge on the transcriptional co-activator PGC-1α, perceived as being the coordinator of much of the transcriptional and posttranscriptional processes. High-load training is dominated by a translational upregulation controlled by mTOR mainly influenced by an insulin/growth factor-dependent signaling cascade as well as mechanical and nutritional cues. Exercise-induced muscle growth is further supported by DNA recruitment through activation and incorporation of satellite cells. Crucial nodes of strength and endurance exercise signaling networks are shared making these training modes interdependent. Robustness of exercise-related signaling is the consequence of signaling being multiple parallel with feed-back and feed-forward control over single and multiple signaling levels. We currently have a good descriptive understanding of the molecular mechanisms controlling muscle phenotypic plasticity. We lack understanding of the precise interactions among partners of signaling networks and accordingly models to predict signaling outcome of entire networks. A major current challenge is to verify and apply available knowledge gained in model systems to predict human phenotypic plasticity.

A genetical genomics approach reveals new candidates and confirms known candidate genes for drip loss in a porcine resource population

In this study lean meat water-holding capacity (WHC) of a Duroc × Pietrain (DuPi) resource population with corresponding genotypes and transcriptomes was investigated using genetical genomics. WHC was characterized by drip loss measured in M. longissimus dorsi. The 60K Illumina SNP chips identified genotypes of 169 F2 DuPi animals. Whole-genome transcriptomes of muscle samples were available for 132 F2 animals using the Affymetrix 24K GeneChip® Porcine Genome Array. Performing genome-wide association studies of transcriptional profiles, which are correlated with phenotypes, allows elucidation of cis- and trans-regulation. Expression levels of 1,228 genes were significantly correlated with drip loss and were further analyzed for enrichment of functional annotation groups as defined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. A hypergeometric gene set enrichment test was performed and revealed glycolysis/glyconeogenesis, pentose phosphate pathway, and pyruvate metabolism as the most promising pathways. For 267 selected transcripts, expression quantitative trait loci (eQTL) analysis was performed and revealed a total of 1,541 significant associations. Because of positional accordance of the gene underlying transcript and the eQTL location, it was possible to identify eight eQTL that can be assumed to be cis-regulated. Comparing the results of gene set enrichment and the eQTL detection tests, molecular networks and potential candidate genes, which seemed to play key roles in the expression of WHC, were detected. The α-1-microglobulin/bikunin precursor (AMBP) gene was assumed to be cis-regulated and was part of the glycolysis pathway. This approach supports the identification of trait-associated SNPs and the further biological understanding of complex traits.

Insulin growth factor receptor (IGF-1R) antibody cixutumumab combined with the mTOR inhibitor temsirolimus in patients with metastatic adrenocortical carcinoma

Background:

Adrenocortical carcinoma (ACC) is a rare and aggressive endocrine malignancy without an available effective systemic chemotherapy. Insulin growth factor 2 (IGF-2) overexpression leading to the activation of the IGF-1 receptor (IGF-1R)/mammalian target of rapamycin (mTOR) pathway is well described in ACC. Cixutumumab, a fully human IgG1 monoclonal antibody directed at IGF-1R was combined with temsirolimus on the basis of preclinical data.

Methods:

Patients received cixutumumab, 3–6 mg kg⁻¹ intravenously (IV) weekly, and temsirolimus, 25–37.5 mg IV weekly (4-week cycles), with restaging after 8 weeks.

Results:

Twenty-six patients were enrolled (13 (50%) men); median age, 47 years; median number of prior therapies, 4. Five patients previously received an IGF-1R inhibitor and one, temsirolimus. The most frequent toxicities, at least possibly drug related, were grade 1–2 thrombocytopenia (38%), mucositis (58%), hypercholesterolaemia (31%), hypertriglyceridemia (35%), and hyperglycaemia (31%). In all, 11 of 26 patients (42%) achieved stable disease (SD) >6 months (duration range=6–21 months) with 3 of the 11 having received a prior IGF-1R inhibitor.

Conclusion:

Cixutumumab combined with temsirolimus was well tolerated and >40% of patients achieved prolonged SD.

R1507, an anti-insulin-like growth factor-1 receptor (IGF-1R) antibody, and EWS/FLI-1 siRNA in Ewing's sarcoma: convergence at the IGF/IGFR/Akt axis

A subset of patients with Ewing's sarcoma responds to anti-insulin-like growth factor-1 receptor (IGF-1R) antibodies. Mechanisms of sensitivity and resistance are unknown. We investigated whether an anti-IGF-1R antibody acts via a pathway that could also be suppressed by small interfering (si) RNA against the EWS/FLI-1 fusion protein, the hallmark of Ewing's sarcoma. The growth of two Ewing's sarcoma cell lines (TC-32 and TC-71) was inhibited by the fully human anti-IGF-1R antibody, R1507 (clonogenic and MTT assays). TC-32 and TC-71 cells express high levels of IGF-2, while RD-ES and A4573 Ewing's cell lines, which were less responsive to R1507 in our assays, express low or undetectable IGF-2, respectively. TC-71 cells also expressed high levels of IGF-1R, and R1507 decreased steady-state levels of this receptor by internalization/degradation, an effect which was associated with a decrease in p-IGF-1R, p-IRS-1, and p-Akt. EWS/FLI-1 siRNA also decreased p-Akt, due to its ability to increase IGF-BP3 levels and subsequently decrease IGF-1 and IGF-2 levels, thus inhibiting signaling through p-IGF-1R. This inhibition correlated with growth suppression and apoptosis. The attenuation of Akt activation was confirmed in TC-71 and HEK-293 (human embryonic kidney) cells by transfecting them with IGF-1R siRNA. We conclude that antibodies and siRNA to IGF-1R, as well as siRNA to EWS/FLI-1, act via intersecting IGF/IGF-1R signals that suppress a common point in this pathway, namely the phosphorylation of Akt.

Variation in the IGF2 gene promoter region is associated with intramuscular fat content in porcine skeletal muscle

Intramuscular fat (IMF) and subcutaneous fat (back fat-BF) are two of the major fat depots in livestock. A QTN located in the insulin-like growth factor 2 gene (IGF2) has been associated with a desirable reduction in BF depth in pigs. Given that the lipid metabolism of intramuscular adipocytes differs from that of subcutaneous fat adipocytes, this study aimed to search for genetic variation in the IGF2 gene that may be associated with IMF, as well as BF, in diverse pig breeds. Four proximal promoter regions of the IGF2 gene were characterised and the association of IGF2 genetic variation with IMF and BF was assessed. Six promoter SNPs were identified in four promoter regions (P1-P4; sequence coverage 945, 866, 784 and 864 bp, respectively) in phenotypically diverse F1 cross populations. Three promoter SNPs were subsequently genotyped in three pure breeds (Pietrain = 98, Duroc = 99 and Large White = 98). All three SNPs were >95% monomorphic in the Pietrain and Duroc breeds but minor alleles were at moderate frequencies in the Large White breed. These SNPs were linked and one was located in a putative transcription factor binding site. Five haplotypes were inferred and three combined diplotypes tested for association with IMF and BF in the Large White. As expected haplotype 1 (likely in LD with the beneficial QTN allele) was superior for BF level. In contrast, the heterozygote diplotype of the most common haplotypes (1 and 2) was associated with higher IMF and marbling scores compared to either homozygote. Gene expression analysis of divergent animals showed that IGF2 was 1.89 fold up-regulated in muscle with higher compared to lower IMF content. These findings suggest that genetic variation in the promoter region of the IGF2 gene is associated with IMF content in porcine skeletal muscle and that greater expression of the IGF2 gene is associated with higher IMF content.

Targeted drug therapies and cancer

With the progress of research in molecular biology and greater understanding of cell signalling systems emerge an increasing array of potential targets for the therapy of cancer. While traditional chemotherapy aims to elicit tumour cell death, it also produces undesirable side effects on physiologically proliferating cells. By isolating cell surface receptors which link specific intracellular secondary messenger pathways, researchers are increasingly able to define the biological network which drives cellular function. Of importance are routes involved in malignant transformation, proliferation, survival and angiogenesis. Thus targeted therapy is directed to specific differential growth processes particular to malignant tumours. The principle mode of action generally involves the "lock-and-key" mechanism and identifying the "Achilles' heel" for drug action. Various targeted agents have been studied and many have translated into significant clinical benefit. This chapter will describe some examples which illustrate the role of this approach in gastrointestinal cancers.

Development of targeted therapy for bladder cancer mediated by a double promoter plasmid expressing diphtheria toxin under the control of H19 and IGF2-P4 regulatory sequences

BACKGROUND

The human IGF2-P4 and H19 promoters are highly active in a variety of human cancers (including bladder cancer), while existing at a nearly undetectable level in the surrounding normal tissue.Single promoter vectors expressing diphtheria toxin A-fragment (DTA) under the control regulation of IGF2-P4 or H19 regulatory sequences (IGF2-P4-DTA and H19-DTA) were previously successfully used in cell lines, animal models and recently in human patients with superficial cell carcinoma of the bladder (treated with H19-DTA). However this targeted medicine approach could be limited, as not all cancer patients express high levels of H19. Hence, a double promoter DTA-expressing vector was created, carrying on a single construct two separate genes expressing the diphtheria toxin A-fragment (DTA), from two different regulatory sequences, selected from the cancer-specific promoters H19 and IGF2-P4.

METHODS

H19 and IGF2-P4 gene expression was tested in samples of Transitional Cell Carcinoma (TCC) of the bladder by in-situ hybridization (ISH) and by quantitative Real-Time PCR (qRT-PCR). The therapeutic potential of the double promoter toxin vector H19-DTA-IGF2-P4-DTA was tested in TCC cell lines and in heterotopic and orthotopic animal models of bladder cancer.

RESULTS

Nearly 100% of TCC patients highly expressed IGF2-P4 and H19, as determined by ISH and by qRT-PCR. The double promoter vector exhibited superior tumor growth inhibition activity compared to the single promoter expression vectors, in cell lines and in heterotopic and orthotopic bladder tumors.

CONCLUSIONS

Our findings show that bladder tumors may be successfully treated by intravesical instillation of the double promoter vector H19-DTA-P4-DTA.Overall, the double promoter vector exhibited enhanced anti-cancer activity relative to single promoter expression vectors carrying either gene alone.

Dietary factors, genetic and epigenetic influences in colorectal cancer

Genetic influences, together with epigenetic components and dietary factors, play a fundamental role in the initiation and progression of cancer by causing a number of deregulations. Colorectal cancer (CRC) is a disease influenced by dietary factors, for which established genetic and epigenetic alterations have been identified. Within CRC, there are hereditary syndromes that present mutations in the germ-line hMLH1, and also alterations in the methylation of the promoters. Epigenetics has also been established as a pathway of carcinogenesis. In the present review, we analyzed studies conducted to discern the different pathways leading to established CRC, stressing the importance of identifying factors that may predict CRC at an early stage, since it is mostly a silent disease observed at the clinical level in advanced stages.

Hypoglycemia from IGF2 overexpression associated with activation of fetal promoters and loss of imprinting in a metastatic hemangiopericytoma

CONTEXT

The mechanism of IGF2 overexpression in non-islet-cell tumor hypoglycemia is not understood.

OBJECTIVE

We investigated the imprinting control and promoter usage for IGF2 expression to identify a mechanism for increased IGF-II production in non-islet-cell tumor hypoglycemia.

PATIENT AND METHODS

A patient with metastatic hemangiopericytoma was studied. Tissue from the original hemangiopericytoma, metastatic tumor, and uninvolved liver was analyzed for IGF-II immunohistochemistry. IGF2, a paternally imprinted gene, shares a control region with maternally imprinted H19, a putative tumor suppressor. IGF-II and H19 mRNA expression was compared in metastatic tumor and uninvolved liver by quantitative RT-PCR. Imprinting of IGF2/H19 genes and IGF2 promoter usage in metastatic tumor was investigated by RT-PCR and sequence analysis, and the methylation pattern in the IGF2/H19 imprinting control region was analyzed.

RESULTS

IGF-II protein expression was increased in metastatic tumor vs. uninvolved liver and original tumor. In the metastatic tumor, IGF-II mRNA was increased 60-fold, but H19 mRNA was comparable to uninvolved liver; loss of imprinting of IGF2, but not H19, was identified; no major change in methylation of the IGF2/H19 imprinting control regions was observed; and transcripts from four different IGF2 promoters were detected, compared to two in uninvolved liver.

CONCLUSIONS

IGF-2 overexpression, newly acquired in the metastatic tumor, was associated with loss of IGF2 gene imprinting and different promoter usage. The imprinting control mechanism governing the IGF2/H19 locus was intact, as evidenced by normal levels of H19, maintenance of H19 imprinting, and no major change in methylation of the imprinting control regions.

Recurrence of urothelial carcinoma of the bladder: a role for insulin-like growth factor-II loss of imprinting and cytoplasmic E-cadherin immunolocalization

PURPOSE

This study documents the frequency of insulin-like growth factor-II (IGF-II) loss of imprinting (LOI) in a series of 87 bladder tissues. E-cadherin (CDH1) immunolocalization was also investigated due to the known redistribution of this adherence protein to the cytoplasm following exogenous exposure to IGF-II.

EXPERIMENTAL DESIGN

Informative IGF-II cases were identified following DNA-PCR amplification and subsequent sequencing of the transcribable ApaI RFLP in exon 9 of IGF-II. Similar approaches using primer-specific cDNA templates identified the imprinting status of IGF-II in these informative cases. CDH1 cellular localization was assessed on a tissue microarray platform of 114 urothelial carcinoma of the bladder (UCB) cases (70 pT(a) noninvasive and 44 pT(1) lamina propria invasive) using the commercially available Novocastra antibody.

RESULTS

IGF-II LOI was evident in 7 of 17 (41%) UCB tumors and 4 of 11 (36%) tumor-associated normal urothelial samples. Two of four pT(1) grade 3 tumors, the subject of much debate concerning their suitability for radical cystectomy, showed LOI at the IGF-II locus. In those tumors showing IGF-II LOI, 4 of 7 (57%) displayed concomitant CDH1 cytoplasmic staining. In contrast, only 3 of 10 (30%) IGF-II maintenance of imprinting tumors had concomitant CDH1 cytoplasmic localization. UCB cell lines displaying cytoplasmic CDH1 immunolocalization expressed significantly higher levels of IGF-II (CAL29, HT1376, and RT112) compared with RT4, a cell line displaying crisp membranous CDH1 staining. Finally, cytoplasmic CDH1 staining was an independent predictor of a shorter time to recurrence independent of tumor grade and stage.

CONCLUSIONS

We suggest that CDH1 cytoplasmic immunolocalization as a result of increased IGF-II levels identifies those nonmuscle invasive presentations most likely to recur and therefore might benefit from more radical nonconserving bladder surgery.

Transgenic overexpression of insulin receptor substrate 1 in hepatocytes enhances hepatocellular proliferation in young mice only

AIM

The insulin receptor substrate-1 (IRS-1) is a multisite docking protein which plays a central role in the signal transduction of growth factors such as insulin and insulin-like growth factors (IGF-1 and IGF-2). It is found to be frequently overexpressed in human hepatocellular carcinoma (HCC).

METHODS

To study IRS-1 overexpression in hepatocytes in vivo, transgenic mice overexpressing IRS-1 exclusively in hepatocytes were created, showing enhanced hepatocyte proliferation in young animals. In the present study, the phenotype of IRS-1 transgenic animals was characterized over a period of two years. The livers of transgenic and control mice were analyzed for IRS-1 expression and phosphorylation, activation of the downstream mitogen-activated protein kinase (MAPK) cascade and phosphatidylinositol 3' kinase (PI3'K) and macroscopical and histological abnormalities.

RESULTS

The enhanced hepatocyte proliferation observed in young IRS-1 transgenic animals was no longer detectable in adult mice. Despite constitutive overexpression and phosphorylation of IRS-1, MAPK- and IRS-1-associated PI3'K activity were significantly reduced in older transgenic mice. Furthermore, no premalignant lesions or HCC were detected in IRS-1 transgenic animals up to the age of 24 months.

CONCLUSIONS

Therefore, additional mechanisms such as enhanced growth factor expression or impaired negative feedback control mechanisms may augment IRS-1 overexpression in human hepatocarcinogenesis.

Urinary insulin-like growth factor 2 identifies the presence of urothelial carcinoma of the bladder

OBJECTIVE

To examine urinary insulin-like growth factor 2 (IGF-2) levels in patient urine samples and determine the potential of IGF-2 as a marker for the presence of urothelial carcinoma of the bladder (UCB).

PATIENTS AND METHODS

The current gold standard for diagnosis of UCB is cystoscopy and cytological analysis. The identification of an accurate urine marker for UCB with the potential to replace unnecessary cystoscopy would benefit patients with UCB and others investigated after detecting haematuria. In the present study, we analysed 65 urine samples, and optimized an enzyme-linked immunosorbent assay-based approach to measure urinary levels of IGF-2.

RESULTS

Based on a threshold of 5.4 ng/mL, patients with UCB have significantly elevated levels of urinary IGF-2 (P = 0.009) and this difference remained significant after adjustment for age and sex (P = 0.04). Sensitivity and specificity values of 80% and 52%, respectively, were determined for urinary IGF-2 alone and when combined with nuclear matrix protein 22 (NMP22; an approved biomarker for detection of UCB). There was a positive correlation between urinary IGF-2 levels and NMP22 levels in patient urine samples and the combined assay improved the detection of UCB (sensitivity 85% and specificity 52%).

CONCLUSION

Substantiated evidence has identified IGF-2 as a valuable marker for UCB. In addition, the novel observations of the present study have shown that aberrant levels of IGF-2 occurring in the presence of UCB, can now be determined through a simple and inexpensive urine assay.

Cancer-associated antigens and antigen arrays in serological diagnostics of malignant tumors

The appearance of antibodies to cancer-associated antigens in biological fluids (particularly, in blood sera) of cancer patients is now a well-established fact, and their detection by immunochemical methods is a promising approach to diagnostics of malignant neoplasms. In this review, we consider some immunobiological aspects of the most extensively studied cancer-associated B-cell antigens, various applications of autoantibodies as cancer biomarkers, and prospects for the use of antigen arrays for improving diagnostic sensitivity.

IGF-I protects human oral buccal mucosal epithelial cells from sodium nitroprusside-induced apoptosis via PI3-kinase

OBJECTIVE

Cancers of the head and neck account for the vast majority of all malignancies of the oral cavity. The insulin-like growth factor (IGF) family of proteins is well documented to have an important role in rescuing cells from apoptosis. While it is known the IGF proteins are present in normal oral epithelial and cancer cells its role is not fully understood. Our aim was to study the ability of IGFs to rescue sodium nitroprusside (SNP)-induced apoptotic normal oral epithelial cells in vitro.

DESIGN

Cultured normal human oral keratinocytes (NOKs) or epithelial cells were used. Apoptosis was induced by SNP then cells were exposed to IGF-I or IGF-II to rescue them. Cell viability was assessed by ELISA (for cell death and caspase 3) and FACS analysis; post receptor effects of IGF-I or IGF-II were assessed by [(3)H] thymidine incorporation. Cell signaling events were measured by western blotting using antibodies against phosphorylated Akt or p42/p44 MAPK, and measuring PI3-K activity by ELISA.

RESULTS

SNP induced apoptosis of NOKs and activated the PI3-K/Akt survival pathway. Exposing cells to IGF proteins prevented their apoptosis. IGF-I and -II caused significant increases in PI3-K, but not MAPK, activity. SNP and LY294002, a PI3-K inhibitor, both caused a significant rise in caspase 3 release from NOKs which was reduced in the presence of IGFs.

CONCLUSIONS

The data establishes the importance of IGF-activated PI3-K in rescuing cells from apoptosis. It lends further evidence to the significance of IGF proteins in the possible development of oral cancer.

Insulin-like growth factor 2 and its receptors (IGF 1R and IGF 2R/mannose 6-phosphate) in endometrial adenocarcinoma

OBJECTIVE

To investigate the consequences of IGF proteins dysfunction in development of endometrial adenocarcinomas.

METHODS

The expression of IGF 2 and IGF 1R was correlated with the expression of IGF 2R and apoptosis rate in 59 human endometrial adenocarcinomas, 10 endometrial hyperplasias and 7 normal tissues. The presence of mutations in the IGF 2R gene was followed in 46 adenocarcinomas. We also examined the effect of IGF 1 receptor blockage on cancer cell proliferation. In groups of either IGF 2-positive or IGF 2-negative tumors (stages III and IV) the expression of IGF 1 and IGF 1R was correlated with cell proliferation index and telomerase activity.

RESULTS

The expression of IGF 2 and IGF 1R was much higher in malignant tissue of stages III and IV than in tumors of stages I and II and normal or hyperplastic endometrium. This correlated with a decreased apoptosis rate and IGF 2R expression. Eight adenocarcinomas expressed biallelic mutation of the IGF 2R gene. The specific inhibition of IGF 1R and IGF 2 decreased tumor cell proliferation in IGF 2/IGF 1R-positive tumors. Furthermore, the positive correlation between increased expression of IGF 1 and IGF 1R proteins and increased telomerase activity and cell proliferation index was found in both IGF 2-negative and IGF 2-positive tumors.

CONCLUSION

Our data suggest that IGF 1, IGF 2 and their receptors are involved in the progression of endometrial adenocarcinomas. As cancer cell proliferation can be abrogated by blocking mRNA or protein products of these genes, tumors with extensive involvement of the IGF 2 pathway would be candidates for the therapeutics strategies aimed at interference with this pathway.

Insulin-like growth factors and their binding proteins in prostate cancer: Cause or consequence?☆

Insulin-like growth factors (IGFs) promote growth and survival of many types of tumor cells. Epidemiologic studies have implicated carcinogenesis with high levels of IGFs in circulation or in tissues. The levels of IGF binding proteins (IGFBPs) have been associated with reduced risk for prostate and other cancers. Experimental studies have implicated high levels of IGF-I directly and IGFBP-3 inversely in prostate cancer growth, survival, and progression. However, recent evidence suggests a much weaker association of IGF-I with prostate cancer development and a stronger antagonistic association of IGFBP-3 with prostate cancer progression. Considering the clonal heterogeneity and unpredictable progression pattern of prostate cancer, the role of any single growth factor or its regulator (IGFBP) as a single determining factor is limited. This review is a critical appraisal of the role of IGFs, IGFBP, and IGF-I receptor (the IGF axis) in both experimental and clinical prostate cancer genesis and progression.

The role of the growth hormone/insulin-like growth factor axis in tumor growth and progression: Lessons from animal models

Over the past two decades it has become widely appreciated that a relationship exists between the insulin-like growth factors (IGFs) and cancer. Many cancers have been shown to overexpress the IGF-I receptor and produce the ligands (IGF-I or IGF-II) and some combinations of the six IGF-binding proteins. With the recent demonstration by epidemiological studies that an elevated serum IGF-I level is associated with an increased relative risk of developing a number of epithelial cancers, interest has been sparked in this area of research with the possibility of targeting the IGF-I receptor in cancer treatment protocols. This review highlights many of the most relevant studies in this exciting area of research, focusing in particular on lessons learned from animal models of cancer.

Polymorphism in IGF-2 as a Surrogate Marker for Predisposition towards Tobacco Chewing-Mediated Oral Cancer

Insulin and insulin-like growth factors (IGFs) are major determinants of proliferation and apoptosis, thereby playing a significant role in carcinogenesis. Epidemiological evidence associates high levels of INS and IGFs with an increased risk of cancer. Polymorphism of the genes involved in insulin-signaling pathways has been associated with a variable risk for neoplasms in different ethnic and environmental backgrounds. In this study, using PCR-RFLP-based assays, we investigated the distribution of genetic polymorphism in INS and IGF-2 genes in tobacco chewing-mediated oral cancer patients (n = 60) and healthy controls (n = 45) of Indian ethnic origin. The genotyping was performed for +1127 INS-Pst1 in INS and +3580 IGF-2-Msp1 in IGF-2. The frequencies of the IGF-2 genotypes AG, GG and AA found in oral cancer patients were 0.68, 0.2 and 0.12, respectively, whereas in noncancer controls these frequencies were 0.27, 0.71 and 0.02. Frequencies of each allele, i.e. CT, TT and CC of INS gene, were found to be nearly equal in the tumor (0.22, 0.75 and 0.03) as well as the normal (0.27, 0.67 and 0.06) population. A significant difference was observed in genotypic frequencies of IGF-2 and INS in the Indian ethnic population as compared to the Caucasian, African and Hispanic populations. Polymorphism at +1127 INS-Pst1 locus of INS gene does not show an implication in oral cancer, whereas the genotype AG or AA at +3580 IGF-2-Msp1 locus of IGF-2 is associated with progression and increased risk of oral cancer. From our study we can conclude that single nucleotide polymorphisms in the IGF-2 gene can be used as a marker for prediction of the risk of oral carcinogenesis.

Gastric cancer: the role of insulin-like growth factor 2 (IGF 2) and its receptors (IGF 1R and M6-P/IGF 2R)

Insulin-like growth factor 2 (IGF 2) appears to be involved in the progression of many tumours. It binds to at least two different types of receptor: IGF type 1 (IGF 1R) and mannose 6-phosphate/IGF type 2 (M6-P/IGF 2R). Ligand binding to IGF 1R provokes mitogenic and anti-apoptotic effects. M6-P/IGF 2R has a tumour suppressor function--it mediates IGF 2 degradation. Mutation of M6-P/IGF 2R causes both diminished growth suppression and augmented growth stimulation. The aim of this study was to investigate the role of IGF 2 and its receptors (IGF 1R and IGF 2R) in human gastric cancer. The expression of IGF 2 and its receptors was measured in order to analyse the possible correlation between the activity of these genes and cell proliferation in two different gastric tumour types: diffuse and intestinal. The effect of IGF 1 receptor blockage on cell proliferation and anchorage-independent cell growth was also examined. Increased expression of IGF 2 and IGF 1R genes (at the mRNA and protein level) was found in gastric cancer when compared with non-tumour tissue. Furthermore, there was a significant difference between IGF 2 expression in the more aggressive diffuse type and that in the intestinal type of gastric cancer. Moreover, the IGF 2 peptide level in the culture media obtained from the diffuse type of cancer cells was significantly higher when compared with the intestinal type. The level of IGF 2 peptide in the conditioned media strongly correlated with [3H]thymidine incorporation and cell proliferation. On the contrary, IGF 2R mRNA expression was much higher in the intestinal type of cancer than in the diffuse type. In addition, IGF 2R protein expression was substantially lower with progression of the diffuse cancer type to a higher stage. The alphaIR3 monoclonal antibody strongly inhibited [3H]thymidine incorporation and decreased the number of colonies in soft agar of cells overexpressing IGF 2. These findings suggest that members of the IGF family are involved in the pathogenesis of gastric cancer, probably by autocrine/paracrine stimulation of cell growth. Such tumours might be excellent candidates for therapeutic strategies aimed at interference with this pathway.