Enhanced sensitivity to IGF-II signaling links loss of imprinting of IGF2 to increased cell proliferation and tumor risk. Proc Natl Acad Sci U S A. 2007;104:20926-20931. [PMID: 18087038 DOI: 10.1073/pnas.0710359105]

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

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

The oncogenic function of PLAGL2 is mediated via ASCL2 and IGF2 and a Wnt-independent mechanism in colorectal cancer

Colorectal cancer (CRC) tumorigenesis and progression are linked to common oncogenic mutations, especially in the tumor suppressor APC, whose loss triggers the deregulation of TCF4/β-Catenin activity. CRC tumorigenesis is also driven by multiple epimutational modifiers such as transcriptional regulators. We describe the common (and near-universal) activation of the zinc finger transcription factor and Let-7 target PLAGL2 in CRC and find that it is a key driver of intestinal epithelial transformation. PLAGL2 drives proliferation, cell cycle progression, and anchorage-independent growth in CRC cell lines and nontransformed intestinal cells. Investigating effects of PLAGL2 on downstream pathways revealed very modest effects on canonical Wnt signaling. Alternatively, we find pronounced effects on the direct PLAGL2 target genes IGF2, a fetal growth factor, and ASCL2, an intestinal stem cell-specific bHLH transcription factor. Inactivation of PLAGL2 in CRC cell lines has pronounced effects on ASCL2 reporter activity. Furthermore, ASCL2 expression can partially rescue deficits of proliferation and cell cycle progression caused by depletion of PLAGL2 in CRC cell lines. Thus, the oncogenic effects of PLAGL2 appear to be mediated via core stem cell and onco-fetal pathways, with minimal effects on downstream Wnt signaling.NEW & NOTEWORTHY A Let-7 target called PLAGL2 drives oncogenic transformation via Wnt-independent pathways. This work illustrates the robust effects of this zinc finger transcription factor in colorectal cancer (CRC) cell lines and nontransformed intestinal epithelium, with effects mediated, in part, via the direct target genes ASCL2 and IGF2. This has implications for the role of PLAGL2 in activation of onco-fetal and onco-stem cell pathways, contributing to immature and highly proliferative phenotypes in CRC.

Insulin‐like growth factor‐2 is a promising candidate for the treatment and prevention of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Current AD treatments slow the rate of cognitive decline, but do not restore lost function. One reason for the low efficacy of current treatments is that they fail to target neurotrophic processes, which are thought to be essential for functional recovery. Bolstering neurotrophic processes may also be a viable strategy for preventative treatment, since structural losses are thought to underlie cognitive decline in AD. The challenge of identifying presymptomatic patients who might benefit from preventative treatment means that any such treatment must meet a high standard of safety and tolerability. The neurotrophic peptide insulin-like growth factor-2 (IGF2) is a promising candidate for both treating and preventing AD-induced cognitive decline. Brain IGF2 expression declines in AD patients. In rodent models of AD, exogenous IGF2 modulates multiple aspects of AD pathology, resulting in (1) improved cognitive function; (2) stimulation of neurogenesis and synaptogenesis; and, (3) neuroprotection against cholinergic dysfunction and beta amyloid-induced neurotoxicity. Preclinical evidence suggests that IGF2 is likely to be safe and tolerable at therapeutic doses. In the preventative treatment context, the intranasal route of administration is likely to be the preferred method for achieving the therapeutic effect without risking adverse side effects. For patients already experiencing AD dementia, routes of administration that deliver IGF2 directly access the CNS may be necessary. Finally, we discuss several strategies for improving the translational validity of animal models used to study the therapeutic potential of IGF2.

Cell cycle control by the insulin-like growth factor signal: at the crossroad between cell growth and mitotic regulation

In proliferating cells and tissues a number of checkpoints (G1/S and G2/M) preceding cell division (M-phase) require the signal provided by growth factors present in serum. IGFs (I and II) have been demonstrated to constitute key intrinsic components of the peptidic active fraction of mammalian serum. In vivo genetic ablation studies have shown that the cellular signal triggered by the IGFs through their cellular receptors represents a non-replaceable requirement for cell growth and cell cycle progression. Retroactive and current evaluation of published literature sheds light on the intracellular circuitry activated by these factors providing us with a better picture of the pleiotropic mechanistic actions by which IGFs regulate both cell size and mitogenesis under developmental growth as well as in malignant proliferation. The present work aims to summarize the cumulative knowledge learned from the IGF ligands/receptors and their intracellular signaling transducers towards control of cell size and cell-cycle with particular focus to their actionable circuits in human cancer. Furthermore, we bring novel perspectives on key functional discriminants of the IGF growth-mitogenic pathway allowing re-evaluation on some of its signal components based upon established evidences.

Integrative genome-wide analyses reveal the transcriptional aberrations in Japanese esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a malignant disease. At present, the genomic profiles of ESCC are known to a considerable extent, and DNA methylation and gene expression profiles have been mainly used for the classification of ESCC subtypes, but integrative genomic, transcriptomic, and epigenomic analyses remain insufficient. Therefore, we performed integrative analyses using whole-exome sequencing, DNA methylation, and RNA sequencing (RNA-seq) analyses of Japanese patients with ESCC. In cancer-related genes, such as NOTCH family genes, RTK/PI3K pathway genes, and NFE2L2 pathway genes, variants and copy number amplification were detected frequently. Japanese ESCC cases were clustered into two mutational signatures: an APOBEC-associated signature and an age-related signature. In imprinted genes, DNA methylation was aberrant in gene promoter regions and correlated well with gene expression profiles. Nonsynonymous single-nucleotide variants and allelic expression imbalance were detected frequently in FAT family genes. Our integrative genome-wide analyses, including DNA methylation and allele-specific gene expression profiles, revealed altered gene regulation of imprinted genes and FAT family genes in ESCC.

Diversity of insulin and IGF signaling in breast cancer: Implications for therapy

This review highlights the significance of the insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF-1R) signaling pathway in cancer and assesses its potential as a therapeutic target. Our emphasis is on breast cancer, but this pathway is central to the behavior of many cancers. An understanding of how IR/IGF-1R signaling contributes to the function of the normal mammary gland provides a foundation for understanding its aberrations in breast cancer. Specifically, dysregulation of the expression and function of ligands (insulin, IGF-1 and IGF-2), receptors and their downstream signaling effectors drive breast cancer initiation and progression, often in a subtype-dependent manner. Efforts to target this pathway for the treatment of cancer have been hindered by several factors including a lack of biomarkers to select patients that could respond to targeted therapy and adverse effects on normal metabolism. To this end, we discuss ongoing efforts aimed at overcoming such obstacles.

The Epigenetic Progenitor Origin of Cancer Reassessed: DNA Methylation Brings Balance to the Stem Force

Cancer initiation and progression toward malignant stages occur as the results of accumulating genetic alterations and epigenetic dysregulation. During the last decade, the development of next generation sequencing (NGS) technologies and the increasing pan-genomic knowledge have revolutionized how we consider the evolving epigenetic landscapes during homeostasis and tumor progression. DNA methylation represents the best studied mark and is considered as a common mechanism of epigenetic regulation in normal homeostasis and cancer. A remarkable amount of work has recently started clarifying the central role played by DNA methylation dynamics on the maintenance of cell identity and on cell fate decisions during the different steps of normal development and tumor evolution. Importantly, a growing number of studies show that DNA methylation is key in the maintenance of adult stemness and in orchestrating commitment in multiple ways. Perturbations of the normal DNA methylation patterns impair the homeostatic balance and can lead to tumor initiation. Therefore, DNA methylation represents an interesting therapeutic target to recover homeostasis in tumor stem cells.

The IGF-II-Insulin Receptor Isoform-A Autocrine Signal in Cancer: Actionable Perspectives

Insulin receptor overexpression is a common event in human cancer. Its overexpression is associated with a relative increase in the expression of its isoform A (IR^A), a shorter variant lacking 11 aa in the extracellular domain, conferring high affinity for the binding of IGF-II along with added intracellular signaling specificity for this ligand. Since IGF-II is secreted by the vast majority of malignant solid cancers, where it establishes autocrine stimuli, the co-expression of IGF-II and IR^A in cancer provides specific advantages such as apoptosis escape, growth, and proliferation to those cancers bearing such a co-expression pattern. However, little is known about the exact role of this autocrine ligand–receptor system in sustaining cancer malignant features such as angiogenesis, invasion, and metastasis. The recent finding that the overexpression of angiogenic receptor kinase EphB4 along with VEGF-A is tightly dependent on the IGF-II/IR^A autocrine system independently of IGFIR provided new perspectives for all malignant IGF2omas (those aggressive solid cancers secreting IGF-II). The present review provides an updated view of the IGF system in cancer, focusing on the biology of the autocrine IGF-II/IR^A ligand–receptor axis and supporting its underscored role as a malignant-switch checkpoint target.

A Loss of Epigenetic Control Can Promote Cell Death through Reversing the Balance of Pathways in a Signaling Network

Epigenetic control of regulatory networks is only partially understood. Expression of Insulin-like growth factor-II (IGF2) is controlled by genomic imprinting, mediated by silencing of the maternal allele. Loss of imprinting of IGF2 (LOI) is linked to intestinal and colorectal cancers, causally in murine models and epidemiologically in humans. However, the molecular underpinnings of the LOI phenotype are not clear. Surprisingly, in LOI cells, we find a reversal of the relative activities of two canonical signaling pathways triggered by IGF2, causing further rebalancing between pro- and anti-apoptotic signaling. A predictive mathematical model shows that this network rebalancing quantitatively accounts for the effect of receptor tyrosine kinase inhibition in both WT and LOI cells. This mechanism also quantitatively explains both the stable LOI phenotype and the therapeutic window for selective killing of LOI cells, and thus prevention of epigenetically controlled cancers. These findings suggest a framework for understanding epigenetically modified cell signaling.

Inhibition of insulin-like growth factor II (IGF-II)-dependent cell growth by multidentate pentamannosyl 6-phosphate-based ligands targeting the mannose 6-phosphate/IGF-II receptor

The mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) binds M6P-capped ligands and IGF-II at different binding sites within the ectodomain and mediates ligand internalization and trafficking to the lysosome. Multivalent M6P-based ligands can cross-bridge the M6P/IGF2R, which increases the rate of receptor internalization, permitting IGF-II binding as a passenger ligand and subsequent trafficking to the lysosome, where the IGF-II is degraded. This unique feature of the receptor may be exploited to design novel therapeutic agents against IGF-II-dependent cancers that will lead to decreased bioavailable IGF-II within the tumor microenvironment. We have designed a panel of M6P-based ligands that bind to the M6P/IGF2R with high affinity in a bivalent manner and cause decreased cell viability. We present evidence that our ligands bind through the M6P-binding sites of the receptor and facilitate internalization and degradation of IGF-II from conditioned medium to mediate this cellular response. To our knowledge, this is the first panel of synthetic bivalent ligands for the M6P/IGF2R that can take advantage of the ligand-receptor interactions of the M6P/IGF2R to provide proof-of-principle evidence for the feasibility of novel chemotherapeutic agents that decrease IGF-II-dependent growth of cancer cells.

Associations of IGF2 and DRD2 polymorphisms with laying traits in Muscovy duck

Insulin-like growth factor 2 (IGF2) and dopamine receptor 2 (DRD2) play important roles in ovarian follicular development. In this study, we analyzed tissue-specific expression of the Muscovy duck IGF2 and DRD2 genes and cloned those genes transcripts. Polymorphisms in these genes were tightly linked with egg production traits and both genes were highly expressed in the ovary. Moreover, we identified five single nucleotide polymorphisms (SNPs) for IGF1 and 28 for DRD2. Mutations A-1864G and C-1704G of IGF2 were positively correlated with increased egg laying at 59 weeks (E59W) (P < 0.05). The C+7T and C+364G mutations of DRD2 were highly and significantly associated with first-egg age (FEA) and egg numbers at 300 days (E300D) (P < 0.01). Moreover, C+3301G and C+3545G of DRD2 were highly significantly associated with FEA, E59W and E300D (P < 0.01). Other mutations were positively associated with FEA or E300D or E59W (P < 0.05). These data suggest specific roles for IGF1 and DRD2 polymorphisms in egg production in Muscovy ducks.

Identification of Clinical and Biologic Correlates Associated With Outcome in Children With Adrenocortical Tumors Without Germline TP53 Mutations: A St Jude Adrenocortical Tumor Registry and Children's Oncology Group Study

Purpose The clinical features, pathogenesis, and outcomes in children with adrenocortical tumors (ACTs) without germline TP53 mutations have not been systematically studied. Herein, we describe these correlates and analyze their association with outcome. Patients and Methods Genomic DNA was analyzed for TP53, CTNNB1, CDKN1C, ATRX, and chromosome 11p15 abnormalities. β-catenin expression and Ki-67 labeling index (LI) were evaluated by immunostaining. Primary end points were progression-free (PFS) and overall survival. Results Median age of 42 girls and 18 boys was 3.3 years (range, 0.25 to 21.7 years). Complete resection (stages I and II) was achieved in 32 patients, and 28 patients had stage III or IV disease. Constitutional abnormalities of chromosome 11p15 occurred in nine of 40 patients, with six patients not showing phenotype of Beckwith-Wiedemann syndrome. Three-year PFS and overall survival for all patients were 71.4% and 80.5%, respectively. In single-predictor Cox regression analysis, age, disease stage, tumor weight, somatic TP53 mutations, and Ki-67 LI were associated with prognosis. Ki-67 LI and age remained significantly associated with PFS after adjusting for stage and tumor weight. Three-year PFS for 27 patients with Ki-67 LI ≥ 15% was 48.5% compared with 96.2% for 29 patients with Ki-67 LI < 15% (log-rank P = .002), and the rate of relapse increased by 24% with each 1-year increase in age at diagnosis (hazard ratio, 1.24; P = .0057). Conclusion Clinicopathologic features and outcomes of children with ACTs without germline TP53 mutations overlapped those reported for children with germline TP53 mutations. Our findings highlight the central role of genetic or epigenetic alterations on chromosome 11p15 in pediatric ACTs. Ki-67 LI is a strong prognostic indicator and should be investigated to improve the histologic classification of pediatric ACTs.

Loss of Igf2 Gene Imprinting in Murine Prostate Promotes Widespread Neoplastic Growth

Loss of imprinting (LOI) is an epigenetic event that relaxes an allele-specific restriction on gene expression. One gene that experiences LOI is the paracrine insulin-like growth factor IGF2, which occurs commonly in human prostate tissues during aging and tumorigenesis. However, the relationship between IGF2 LOI and prostate tumorigenesis has not been established functionally. In this study, we created a mouse model with CTCF-binding site mutations at the Igf2-H19 imprint control region that abolishes CTCF insulator activity, resulting in biallelic Igf2 expression that mimics increased levels seen with aging-induced LOI. We found that Igf2 LOI increased the prevalence and severity of prostatic intraepithelial neoplasia (PIN), a premalignant lesion. Engineering Nkx3.1 deficiency into our model increased the frequency of PIN lesions in an additive fashion. Prostates harboring LOI displayed increased MAPK signaling and epithelial proliferation. In human prostate tissue arrays, we documented a positive correlation in benign tissues of IGF2 levels with phospho-ERK and phospho-AKT levels. Overall, our results establish that Igf2 LOI is sufficient on its own to increase rates of neoplastic development in the prostate by upregulating critical cancer-associated signaling pathways. Cancer Res; 77(19); 5236-47. ©2017 AACR.

The IGF axis in HPV associated cancers

Human papillomaviruses (HPV) infect and replicate in stratified epithelium at cutaneous and mucosal surfaces. The proliferation and maintenance of keratinocytes, the cells which make up this epithelium, are controlled by a number of growth factor receptors such as the keratinocyte growth factor receptor (KGFR, also called fibroblast growth factor receptor 2b (FGFR2b)), the epithelial growth factor receptor (EGFR) and the insulin-like growth factor receptors 1 and 2 (IGF1R and IGF2R). In this review, we will delineate the mutation, gene transcription, translation and processing of the IGF axis within HPV associated cancers. The IGFs are key for developmental and postnatal growth of almost all tissues; we explore whether this crucial axis has been hijacked by HPV.

Carcinoma of the colon and rectum with deregulation of insulin-like growth factor 2 signaling: clinical and molecular implications

BACKGROUND

Loss of imprinting (LOI) of the insulin-like growth factor 2 (IGF2) is an early event in the development of colorectal cancer (CRC). Whether LOI of IGF2 denotes a molecular or clinical cancer subgroup is currently unknown.

METHODS

Tumor biopsies and paired normal mucosa from 399 patients with extensive clinical annotations were analyzed for LOI and IGF2 expression. LOI status in 140 informative cases was correlated with clinicopathologic parameters and outcome.

RESULTS

LOI was frequent in normal mucosa and tumors and occurred throughout the large intestine. LOI was unrelated to microsatellite instability, KRAS mutation status, stage, and survival. However, CRC with LOI showed increased IGF2 protein levels and activation of AKT1. Gene expression analysis of tumors with and without LOI and knockdown of IGF2 in cell lines revealed that IGF2 induced distinct sets of activated and repressed genes, including Wnt5a, CEACAM6, IGF2BP3, KPN2A, BRCA2, and CDK1. Inhibition of AKT1 in IGF2-stimulated cells showed that the downstream effects of IGF2 on cell proliferation and gene expression were strictly AKT1-dependent.

CONCLUSIONS

LOI of IGF2 is a frequent and early event in CRC that occurs both in the adenomatous polyposis coli (APC) gene-mutated and serrated route of carcinogenesis. LOI leads to overexpression of IGF2, activates IGF1R and AKT1, and is a powerful driver of cell proliferation. Moreover, our results suggest that IGF2 via AKT1 also contributes to non-canonical wnt signaling. Although LOI had no significant impact on major clinical parameters and outcome, its potential as a target for preventive and therapeutic interventions merits further investigation.

Epigenetic alteration to activate Bmp2-Smad signaling in Raf-induced senescence

AIM: To investigate epigenomic and gene expression alterations during cellular senescence induced by oncogenic Raf.

METHODS: Cellular senescence was induced into mouse embryonic fibroblasts (MEFs) by infecting retrovirus to express oncogenic Raf (RafV600E). RNA was collected from RafV600E cells as well as MEFs without infection and MEFs with mock infection, and a genome-wide gene expression analysis was performed using microarray. The epigenomic status for active H3K4me3 and repressive H3K27me3 histone marks was analyzed by chromatin immunoprecipitation-sequencing for RafV600E cells on day 7 and for MEFs without infection. These data for Raf-induced senescence were compared with data for Ras-induced senescence that were obtained in our previous study. Gene knockdown and overexpression were done by retrovirus infection.

RESULTS: Although the expression of some genes including secreted factors was specifically altered in either Ras- or Raf-induced senescence, many genes showed similar alteration pattern in Raf- and Ras-induced senescence. A total of 841 commonly upregulated 841 genes and 573 commonly downregulated genes showed a significant enrichment of genes related to signal and secreted proteins, suggesting the importance of alterations in secreted factors. Bmp2, a secreted protein to activate Bmp2-Smad signaling, was highly upregulated with gain of H3K4me3 and loss of H3K27me3 during Raf-induced senescence, as previously detected in Ras-induced senescence, and the knockdown of Bmp2 by shRNA lead to escape from Raf-induced senescence. Bmp2-Smad inhibitor Smad6 was strongly repressed with H3K4me3 loss in Raf-induced senescence, as detected in Ras-induced senescence, and senescence was also bypassed by Smad6 induction in Raf-activated cells. Different from Ras-induced senescence, however, gain of H3K27me3 did not occur in the Smad6 promoter region during Raf-induced senescence. When comparing genome-wide alteration between Ras- and Raf-induced senescence, genes showing loss of H3K27me3 during senescence significantly overlapped; genes showing H3K4me3 gain, or those showing H3K4me3 loss, also well-overlapped between Ras- and Raf-induced senescence. However, genes with gain of H3K27me3 overlapped significantly rarely, compared with those with H3K27me3 loss, with H3K4me3 gain, or with H3K4me3 loss.

CONCLUSION: Although epigenetic alterations are partly different, Bmp2 upregulation and Smad6 repression occur and contribute to Raf-induced senescence, as detected in Ras-induced senescence.

Epigenomic Regulation of Smad1 Signaling During Cellular Senescence Induced by Ras Activation

Epigenomic modification plays important roles in regulating gene expression during development, differentiation, and cellular senescence. When oncogenes are activated, cells fall into stable growth arrest to block cellular proliferation, which is called oncogene-induced senescence. We recently identified through genome-wide analyses that Bmp2-Smad1 signal and its regulation by harmonized epigenomic alteration play an important role in Ras-induced senescence of mouse embryonic fibroblasts. We describe in this chapter the methods for analyses of epigenomic alteration and Smad1 targets on genome-wide scale.

Loss of imprinting of IGF2 in fibroadenomas and phyllodes tumors of the breast

Loss of imprinting (LOI) of insulin-like growth factor 2 (IGF2) is thought to be implicated in the pathogenesis of some tumors by upregulating IGF2 mRNA but its role in the pathogenesis of fibroadenomas (FAs) and phyllodes tumors (PTs) of the breast is yet to be studied. LOI of IGF2 was investigated in 25 FAs and 17 PTs which were heterozygous for Apa I polymorphism, and was found to be present in 13 FAs and 12 PTs. IGF2 mRNA expression was more upregulated in FAs and PTs than in paired surrounding normal tissues and laser microdissection showed that IGF2 mRNA expression was significantly higher in the stromal than the epithelial cells. LOI was not associated with upregulation of IGF2 mRNA, nor were MED12 mutations and methylation status of the differentially methylated region 0 (DMR0) of IGF2. These results demonstrate that IGF2 mRNA expression is more upregulated in FAs and PTs than in normal tissues, especially in their stromal cells, but such an upregulation is not related to LOI of IGF2, and that hypomethylation of DMR0 is unlikely to be involved in induction of LOI.

Insulin and IGFs in renal cancer risk and progression

Insulin and IGFs play a significant role in cancer development and progression, including renal cell carcinoma (RCC). RCC is the most frequent type of kidney cancer in adults and the tenth most common malignancy worldwide. Insulin is normally associated with metabolism control, whereas IGFs are defined as proliferation regulators. Today, there is convincing evidence of an association between obesity and the risk of RCC. Indicated risk factors together with type 2 diabetes are irreversibly connected with circulating insulin and IGF levels. The interplay between these molecules, their receptors, and IGF-binding proteins might be crucial for RCC cell biology and RCC progression. Given the potent activity IGF/IGF receptor 1 (IGF1R) inhibitors demonstrate against RCC in basic research, some type of combination therapy may prove to be beneficial clinically in the management of RCC. This review addresses not only molecular but also clinical associations between insulin and IGF1 signaling pathways and both RCC biology and clinical course. Revealing these interactions may improve our understanding of basic molecular oncology processes in RCC and improve treatment strategies.

Epigenetics of colorectal cancer

Colorectal cancer (CRC) is one of most common malignancies and a leading cause of cancer related deaths worldwide. Epigenetic change is an important mechanism of colorectal carcinogenesis. Accumulation of epigenetic changes was found in colorectal cancer and other tumors. Aberrant changes in DNA methylation, histone modification, imprinting, and noncoding RNAs were frequently found in human colorectal cancer. Epigenetic changes may serve as a diagnostic, prognostic, and chemo-sensitive marker. It also becomes a cancer preventive or therapeutic target in some circumstances.

Distinct allelic expression patterns of imprinted IGF2 in adenocarcinoma and squamous cell carcinoma of the lung

The insulin-like growth factor 2 gene (IGF2) is an imprinting gene, which mediates cell growth and apoptosis. The loss of imprinting (LOI) of IGF2 has been associated with the development of cancer. In the present study, loss LOI of IGF2 in lung cancer was analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in combination with DNA sequencing of samples collected by laser capture microdissection. The status of each sample was assigned as imprinting when PCR-RFLP revealed only one band or sequence with a single peak; otherwise, the case was classified as LOI. LOI was identified in eight out of 13 adenocarcinoma cases (62%), but was not detected in any of the nine squamous cell carcinoma cases (0%). These results suggest that IGF2 LOI is involved in the molecular pathogenesis of lung adenocarcinoma, but not squamous cell carcinoma, and that LOI may be detected through increased IGF2 expression levels.

IGF2 promotes growth of adrenocortical carcinoma cells, but its overexpression does not modify phenotypic and molecular features of adrenocortical carcinoma

Insulin-like growth factor 2 (IGF2) overexpression is an important molecular marker of adrenocortical carcinoma (ACC), which is a rare but devastating endocrine cancer. It is not clear whether IGF2 overexpression modifies the biology and growth of this cancer, thus more studies are required before IGF2 can be considered as a major therapeutic target. We compared the phenotypical, clinical, biological, and molecular characteristics of ACC with or without the overexpression of IGF2, to address these issues. We also carried out a similar analysis in an ACC cell line (H295R) in which IGF2 expression was knocked down with si- or shRNA. We found no significant differences in the clinical, biological and molecular (transcriptomic) traits between IGF2-high and IGF2-low ACC. The absence of IGF2 overexpression had little influence on the activation of tyrosine kinase pathways both in tumors and in H295 cells that express low levels of IGF2. In IGF2-low tumors, other growth factors (FGF9, PDGFA) are more expressed than in IGF2-high tumors, suggesting that they play a compensatory role in tumor progression. In addition, IGF2 knock-down in H295R cells substantially impaired growth (>50% inhibition), blocked cells in G1 phase, and promoted apoptosis (>2-fold). Finally, analysis of the 11p15 locus showed a paternal uniparental disomy in both IGF2-high and IGF2-low tumors, but low IGF2 expression could be explained in most IGF2-low ACC by an additional epigenetic modification at the 11p15 locus. Altogether, these observations confirm the active role of IGF2 in adrenocortical tumor growth, but also suggest that other growth promoting pathways may be involved in a subset of ACC with low IGF2 expression, which creates opportunities for the use of other targeted therapies.

IGF2 DMR0 methylation, loss of imprinting, and patient prognosis in esophageal squamous cell carcinoma

BACKGROUND

Insulin like growth factor 2 gene (IGF2) is normally imprinted. Loss of imprinting (LOI) of IGF2 in humans is associated with an increased risk of cancer and is controlled by CpG-rich regions known as differentially methylated regions (DMRs). Specifically, the methylation level at IGF2 DMR0 is correlated with IGF2 LOI and is a suggested surrogate marker for IGF2 LOI. A relationship between IGF2 DMR0 hypomethylation and poor prognosis has been shown in colorectal cancer. However, to our knowledge, no study has examined the relationships among the IGF2 DMR0 methylation level, LOI, and clinical outcome in esophageal squamous cell carcinoma (ESCC).

METHODS

The IGF2 imprinting status was screened using ApaI polymorphism, and IGF2 protein expression was evaluated by immunohistochemistry with 30 ESCC tissue specimens. For survival analysis, IGF2 DMR0 methylation was measured using a bisulfite pyrosequencing assay with 216 ESCC tissue specimens.

RESULTS

Twelve (40 %) of 30 cases were informative (i.e., heterozygous for ApaI), and 5 (42 %) of 12 informative cases displayed IGF2 LOI. IGF2 LOI cases exhibited lower DMR0 methylation levels (mean 23 %) than IGF2 non-LOI cases (37 %). The IGF2 DMR0 methylation level was significantly associated with IGF2 protein expression. Among 202 patients eligible for survival analysis, IGF2 DMR0 hypomethylation was significantly associated with higher cancer-specific mortality.

CONCLUSIONS

The IGF2 DMR0 methylation level in ESCC was associated with IGF2 LOI and IGF2 protein expression. In addition, IGF2 DMR0 hypomethylation was associated with a shorter survival time, suggesting its potential role as a prognostic biomarker.

Epithelial cancers in the post-genomic era: should we reconsider our lifestyle?

The age-related epithelial cancers of the breast, colorectum and prostate are the most prevalent and are increasing in our aging populations. Epithelial cells turnover rapidly and mutations naturally accumulate throughout life. Most epithelial cancers arise from this normal mutation rate. All elderly individuals will harbour many cells with the requisite mutations and most will develop occult neoplastic lesions. Although essential for initiation, these mutations are not sufficient for the progression of cancer to a life-threatening disease. This progression appears to be dependent on context: the tissue ecosystem within individuals and lifestyle exposures across populations of individuals. Together, this implies that the seeds may be plentiful but they only germinate in the right soil. The incidence of these cancers is much lower in Eastern countries but is increasing with Westernisation and increases more acutely in migrants to the West. A Western lifestyle is strongly associated with perturbed metabolism, as evidenced by the epidemics of obesity and diabetes: this may also provide the setting enabling the progression of epithelial cancers. Epidemiology has indicated that metabolic biomarkers are prospectively associated with cancer incidence and prognosis. Furthermore, within cancer research, there has been a rediscovery that a switch in cell metabolism is critical for cancer progression but this is set within the metabolic status of the host. The seed may only germinate if the soil is fertile. This perspective brings together the different avenues of investigation implicating the role that metabolism may play within the context of post-genomic concepts of cancer.

IGF2 and cancer

Insulin-like growth factor 2 (IGF2) is a 7.5  kDa mitogenic peptide hormone expressed by liver and many other tissues. It is three times more abundant in serum than IGF1, but our understanding of its physiological and pathological roles has lagged behind that of IGF1. Expression of the IGF2 gene is strictly regulated. Over-expression occurs in many cancers and is associated with a poor prognosis. Elevated serum IGF2 is also associated with increased risk of developing various cancers including colorectal, breast, prostate and lung. There is established clinical utility for IGF2 measurement in the diagnosis of non-islet cell tumour hypoglycaemia, a condition characterised by a molar IGF2:IGF1 ratio >10. Recent advances in understanding of the pathophysiology of IGF2 in cancer have suggested much novel clinical utility for its measurement. Measurement of IGF2 in blood and genetic and epigenetic tests of the IGF2 gene may help assess cancer risk and prognosis. Further studies will determine whether these tests enter clinical practice. New therapeutic approaches are being developed to target IGF2 action. This review provides a clinical perspective on IGF2 and an update on recent research findings.

Cancer as a dysregulated epigenome allowing cellular growth advantage at the expense of the host

Although at the genetic level cancer is caused by diverse mutations, epigenetic modifications are characteristic of all cancers, from apparently normal precursor tissue to advanced metastatic disease, and these epigenetic modifications drive tumour cell heterogeneity. We propose a unifying model of cancer in which epigenetic dysregulation allows rapid selection for tumour cell survival at the expense of the host. Mechanisms involve both genetic mutations and epigenetic modifications that disrupt the function of genes that regulate the epigenome itself. Several exciting recent discoveries also point to a genome-scale disruption of the epigenome that involves large blocks of DNA hypomethylation, mutations of epigenetic modifier genes and alterations of heterochromatin in cancer (including large organized chromatin lysine modifications (LOCKs) and lamin-associated domains (LADs)), all of which increase epigenetic and gene expression plasticity. Our model suggests a new approach to cancer diagnosis and therapy that focuses on epigenetic dysregulation and has great potential for risk detection and chemoprevention.

IGF-2 mediates intestinal mucosal hyperplasia in retinoblastoma protein (Rb)-deficient mice

PURPOSE

We have previously demonstrated a hyperplastic phenotype when Rb expression was disrupted within the intestinal epithelium. These findings mimic resection-induced adaptation suggesting a possible mechanistic role for Rb during adaptation. The purpose of the present study was to elucidate a mechanism for how Rb deficiency induces intestinal hyperplasia.

METHODS

Enterocytes isolated from intestine-specific Rb knockout mice (Rb-IKO) underwent a microarray to elucidate their gene expression profile. IGF2 expression was significantly elevated, which was subsequently confirmed by RT-PCR and in situ mRNA hybridization. Mice with deficient expression of IGF2 or its receptor IGF1R were therefore crossed with Rb-IKO mice to determine the significance of IGF2 in mediating the Rb-IKO intestinal phenotype.

RESULTS

Expression of IGF2 was significantly elevated in villus enterocytes of Rb-IKO mice. The mucosal hyperplasia in Rb-IKO mice was reversed when either IGF2 or IGF1R expression was genetically disrupted in Rb-IKO mice.

CONCLUSION

IGF-2 expression is significantly elevated in villus enterocytes and is required for the hyperplastic intestinal mucosal phenotype of Rb-IKO mice. The trophic effects of IGF2 require intact IGF1R signaling within the intestinal epithelium. These findings reveal novel regulatory roles for Rb in expanding intestinal mucosal surface area.

Dynamic chromatin loops bridge health and disease in the nuclear landscape

The genome is dynamically organized in the nuclear space in a manner that reflects and influences nuclear functions. Developmental processes that govern the formation and maintenance of epigenetic memories are also tightly linked to adaptive changes in the physical and functional landscape of the nuclear architecture. Biological and biophysical principles governing the three-dimensional folding of chromatin are therefore central to our understanding of epigenetic regulation during adaptive responses and in complex diseases, such as cancer. Accumulating evidence points to the direction that global alterations in nuclear architecture and chromatin folding conspire with unstable epigenetic states of the primary chromatin fiber to drive the phenotypic plasticity of cancer cells.

Epigenetic aspects on therapy development for gastroenteropancreatic neuroendocrine tumors

The understanding of epigenetic modifications in gastroenteropancreatic neuroendocrine tumors is a novel and still small field. Activation of the insulin-like growth factor 2 gene locus by loss of imprinting is a classical epigenetic alteration frequently observed in insulinoma. Inactivation of the MEN1 gene, commonly involved in endocrine pancreatic tumors, impairs the association with mixed lineage leukemia involved in histone H3K4me3 methylation. In addition, promising effects on tumor phenotypes such as growth, apoptosis, cell cycle arrest, and expression of neuroendocrine markers have been obtained in vitro for inhibitors of DNA methyltransferase (azacytidine) and histone deacetylation (butyrate, valproic acid, trichostatin A and MS-275). The frequent need for complementary treatments in addition to surgery in this tumor entity supports further efforts in the development and application of drugs acting at general as well as more specific epigenetic alterations.

Genetic variation in insulin pathway genes and distal colorectal adenoma risk

BACKGROUND

Insulin, glucose, and other insulin-related proteins that mediate insulin signaling are associated with colorectal neoplasia risk, but associations with common genetic variation in insulin axis genes are less clear. In this study, we used a comprehensive tag single-nucleotide polymorphisms (SNPs) approach to define genetic variation in six insulin axis genes (IGF1, IGF2, IGFBP1, IGFBP3, IRS1, and IRS2) and three genes associated with estrogen signaling (ESR1, ESR2, and PGR).

METHODS

We assessed associations between SNPs and distal colorectal adenoma (CRA) risk in a case-control study of 1,351 subjects. Cases were individuals with one or more adenomas diagnosed during sigmoidoscopy, and controls were individuals with no adenomas at the sigmoidoscopy exam. We used unconditional logistic regression assuming an additive model to assess SNP-specific risks adjusting for multiple comparisons with P (act).

RESULTS

Distal adenoma risk was significantly increased for one SNP in IGF2 [per minor allele OR = 1.41; 95 % confidence interval (CI) = 1.16, 1.67; P (act) = 0.005] and decreased for an ESR2 SNP (per minor allele OR = 0.78; 95 % CI = 0.66, 0.91; P (act) = 0.041). There was no statistically significant heterogeneity of these associations by race, sex, BMI, physical activity, or, in women, hormone replacement therapy use. Risk estimates did not differ in the colon versus rectum or for smaller (<1 cm) versus larger (>1 cm) adenomas.

CONCLUSIONS

These data suggest that selected genetic variability in IGF2 and ESR2 may be modifiers of CRA risk.

Nutrition, epigenetics, and metabolic syndrome

SIGNIFICANCE

Epidemiological and animal studies have demonstrated a close link between maternal nutrition and chronic metabolic disease in children and adults. Compelling experimental results also indicate that adverse effects of intrauterine growth restriction on offspring can be carried forward to subsequent generations through covalent modifications of DNA and core histones.

RECENT ADVANCES

DNA methylation is catalyzed by S-adenosylmethionine-dependent DNA methyltransferases. Methylation, demethylation, acetylation, and deacetylation of histone proteins are performed by histone methyltransferase, histone demethylase, histone acetyltransferase, and histone deacetyltransferase, respectively. Histone activities are also influenced by phosphorylation, ubiquitination, ADP-ribosylation, sumoylation, and glycosylation. Metabolism of amino acids (glycine, histidine, methionine, and serine) and vitamins (B6, B12, and folate) plays a key role in provision of methyl donors for DNA and protein methylation.

CRITICAL ISSUES

Disruption of epigenetic mechanisms can result in oxidative stress, obesity, insulin resistance, diabetes, and vascular dysfunction in animals and humans. Despite a recognized role for epigenetics in fetal programming of metabolic syndrome, research on therapies is still in its infancy. Possible interventions include: 1) inhibition of DNA methylation, histone deacetylation, and microRNA expression; 2) targeting epigenetically disturbed metabolic pathways; and 3) dietary supplementation with functional amino acids, vitamins, and phytochemicals.

FUTURE DIRECTIONS

Much work is needed with animal models to understand the basic mechanisms responsible for the roles of specific nutrients in fetal and neonatal programming. Such new knowledge is crucial to design effective therapeutic strategies for preventing and treating metabolic abnormalities in offspring born to mothers with a previous experience of malnutrition.

Dissection of the maternal effects on puberty onset by embryo transplantation in mouse

Puberty onset in mammals is affected by multiple genetic and environmental factors. Among which, the maternal effect could have played a considerable role. In our previous study, we found that the F1 offspring from reciprocal crosses between C3H/HeJ (C3H) and C57BL/6J (B6) mice differed significantly in the timing of puberty in both sexes, though they had identical genomic background. In order to dissect the causative factors to such phenomenon of maternal effect, embryos from reciprocal crosses of C3H/HeJ and C57BL/6J mice were collected and transplanted to the uterus of either strain of mothers, and the puberty onset of pups were compared between different recipient mothers and egg origins. The results showed that the male pups from C3H recipient mothers attained puberty onset earlier than those from B6 recipients significantly, while the female pups did not show such difference. On the other hand, the egg origin made no difference in the puberty onset of either sex, yet it influenced the birth weight of female pups significantly (p<0.05). The manipulation of embryo transplantation delayed the puberty onset of pups dramatically. A mitochondria substitution strain between B6 and C3H (BmC), which had the genome background of B6 and a mitochondrial hyplotype of C3H, had the same phenotype of puberty onset as B6. The integrated results indicated that the uterine environment was the major causative factors to the maternal effect on the differential puberty onset in reciprocal crosses of F1 hybrids between B6 and C3H mice.

Microfluidic technologies for studying synthetic circuits

Advances in synthetic biology have augmented the available toolkit of biomolecular modules, allowing engineering and manipulation of signaling in a variety of organisms, ranging in complexity from single bacteria and eukaryotic cells to multi-cellular systems. The richness of synthetic circuit outputs can be dramatically enhanced by sophisticated environmental control systems designed to precisely pattern spatial-temporally heterogeneous environmental stimuli controlling these circuits. Moreover, the performance of the synthetic modules and 'blocks' needed to assemble more complicated networks requires more complete characterization as a function of arbitrarily complex environmental inputs. Microfluidic technologies are poised to meet these needs through a variety of innovative designs capitalizing on the unique benefits of manipulating fluids on the micro-scales and nano-scales. This review discusses the utility of microfluidics for the study of synthetic circuits and highlights recent work in the area.

Specific hypomethylated CpGs at the IGF2 locus act as an epigenetic biomarker for familial adenomatous polyposis colorectal cancer

AIMS

The identification of specific biomarkers for colorectal cancer is of primary importance for early diagnosis. The aim of this study was to evaluate if methylation changes at the IGF2/H19 locus could be predictive for individuals at high risk for developing sporadic or hereditary colorectal cancer.

MATERIALS & METHODS

Quantitative methylation analysis using pyrosequencing was performed on three differentially methylated regions (DMRs): IGF2 DMR0 and DMR2 and the H19 DMR in DNA samples from sporadic colorectal cancer (n = 26), familial adenomatous polyposis (n = 35) and hereditary nonpolyposis colorectal cancer (n = 19) patients.

RESULTS

We report in this article for the first time, that in sporadic colorectal cancer tumor DNA both the IGF2 DMR0 and DMR2 are hypomethylated, while the H19 DMR retains its monoallelic methylation pattern. In lymphocyte DNA, a striking hypomethylation of nine contiguous correlated CpGs was found in the IGF2 DMR2 but only in familial adenomatous polyposis patients.

CONCLUSION

Methylation alterations at the IGF2 locus are more extensive than previously reported and DMR2 hypomethylation in lymphocyte DNA might be a specific epigenetic biomarker for familial adenomatous polyposis patients.

Identification of biomarkers to distinguish clear cell sarcoma from malignant melanoma

Clear cell sarcoma is a rare and malignant soft tissue tumor that shows phenotypic and immunohistochemical overlap with cutaneous malignant melanoma; identification of biomarkers that differentiate clear cell sarcoma from malignant melanoma is therefore needed. In this study, we performed mutation analysis of BRAF and NRAS, investigated the EWSR1 gene rearrangement and evaluated the protein expression of insulin-like growth factor 2 and insulin-like growth factor 1R in 31 cases of malignant melanoma and 16 cases of clear cell sarcoma. By direct sequencing and high-resolution melting analysis, we identified BRAF and NRAS mutations in 51.6% and 12.9% of malignant melanoma cases, respectively, while none of clear cell sarcoma harbored BRAF or NRAS mutations. Fluorescence in situ hybridization showed that 78.6% of clear cell sarcoma exhibited the t(12;22)(q13;q12) translocation. The presence of type 1, 2, and 3 EWSR1/ATF1 fusion gene transcripts was confirmed by reverse transcriptase polymerase chain reaction analysis, but type 4 and EWSR1/CREB1 fusion gene transcripts were not found. No fusion transcript could be detected in any of the malignant melanoma cases. Additionally, immunohistochemistry showed that the majority of clear cell sarcoma and malignant melanoma had insulin-like growth factor 2 and insulin-like growth factor receptor 1 expression; however the expression of insulin-like growth factor 1R was significantly higher in clear cell sarcoma compared to melanoma (p = .006). Our results suggest that the combination of BRAF and NRAS mutation analysis with fusion gene detection contributes to diagnosis of malignant melanoma and clear cell sarcoma, and that insulin-like growth factor 1R might be a novel target for the treatment of these two malignancies.

Specific changes in the expression of imprinted genes in prostate cancer--implications for cancer progression and epigenetic regulation

Epigenetic dysregulation comprising DNA hypermethylation and hypomethylation, enhancer of zeste homologue 2 (EZH2) overexpression and altered patterns of histone modifications is associated with the progression of prostate cancer. DNA methylation, EZH2 and histone modifications also ensure the parental-specific monoallelic expression of at least 62 imprinted genes. Although it is therefore tempting to speculate that epigenetic dysregulation may extend to imprinted genes, expression changes in cancerous prostates are only well documented for insulin-like growth factor 2 (IGF2). A literature and database survey on imprinted genes in prostate cancer suggests that the expression of most imprinted genes remains unchanged despite global disturbances in epigenetic mechanisms. Instead, selective genetic and epigenetic changes appear to lead to the inactivation of a sub-network of imprinted genes, which might function in the prostate to limit cell growth induced via the PI3K/Akt pathway, modulate androgen responses and regulate differentiation. Whereas dysregulation of IGF2 may constitute an early change in prostate carcinogenesis, inactivation of this imprinted gene network is rather associated with cancer progression.

Biology and significance of signalling pathways activated by IGF-II

Insulin-like growth factor-II (IGF-II) affects many aspects of cellular function through its ability to activate several different receptors and, consequently, numerous intracellular signalling molecules. Thus, IGF-II is a key regulator of normal foetal development and growth. However, abnormalities in IGF-II function are associated with cardiovascular disease and cancer. Here, we review the cellular mechanisms by which IGF-II's physiological and pathophysiological actions are exerted by discussing the involvement of the type 1 and type 2 IGF receptors (IGF1R and IGF2R), the insulin receptor and the downstream MAP kinase, PI-3 kinase and G-protein-coupled signalling pathways in mediating IGF-II stimulated cellular proliferation, survival, differentiation and migration.

Activation of Bmp2-Smad1 signal and its regulation by coordinated alteration of H3K27 trimethylation in Ras-induced senescence

Cellular senescence involves epigenetic alteration, e.g. loss of H3K27me3 in Ink4a-Arf locus. Using mouse embryonic fibroblast (MEF), we here analyzed transcription and epigenetic alteration during Ras-induced senescence on genome-wide scale by chromatin immunoprecipitation (ChIP)-sequencing and microarray. Bmp2 was the most activated secreted factor with H3K4me3 gain and H3K27me3 loss, whereas H3K4me3 loss and de novo formation of H3K27me3 occurred inversely in repression of nine genes, including two BMP-SMAD inhibitors Smad6 and Noggin. DNA methylation alteration unlikely occurred. Ras-activated cells senesced with nuclear accumulation of phosphorylated SMAD1/5/8. Senescence was bypassed in Ras-activated cells when Bmp2/Smad1 signal was blocked by Bmp2 knockdown, Smad6 induction, or Noggin induction. Senescence was induced when recombinant BMP2 protein was added to Bmp2-knocked-down Ras-activated cells. Downstream Bmp2-Smad1 target genes were then analyzed genome-wide by ChIP-sequencing using anti-Smad1 antibody in MEF that was exposed to BMP2. Smad1 target sites were enriched nearby transcription start sites of genes, which significantly correlated to upregulation by BMP2 stimulation. While Smad6 was one of Smad1 target genes to be upregulated by BMP2 exposure, Smad6 repression in Ras-activated cells with increased enrichment of Ezh2 and gain of H3K27me3 suggested epigenetic disruption of negative feedback by Polycomb. Among Smad1 target genes that were upregulated in Ras-activated cells without increased repressive mark, Parvb was found to contribute to growth inhibition as Parvb knockdown lead to escape from senescence. It was revealed through genome-wide analyses in this study that Bmp2-Smad1 signal and its regulation by harmonized epigenomic alteration play an important role in Ras-induced senescence.

To avoid becoming cancer cells, cells have a barrier system to block cellular proliferation by falling into irreversible growth arrest, so-called cellular senescence. For future strategy of cancer treatment, it is important to understand how cancer occurs, and investigation of underlying mechanism in senescence can lead to clarification of carcinogenesis mechanism. Epigenetic mechanism including DNA methylation and histone modification may be important to regulate gene expressions properly in senescence. Here, taking advantage of recent technical and methodological advance of genome-wide analyses, we examine epigenome and gene expression alteration in senescence induced by Ras oncogene. We identify that Bmp2-Smad1 signal is critical. We further examine downstream target genes of this critical signal on a genome-wide scale. We show dynamic and coordinated H3K27me3 alteration, e.g. activation of Bmp2 by loss of H3K27me3, repression of the signal inhibitors and the negative feedback loop by gain of H3K27me3, and selective activation of downstream target genes that may contribute to growth arrest. Our findings are helpful in understanding the importance of epigenetic regulation and a critical signal in the physiological barrier system against oncogenic transformation and the importance of disruption of BMP-SMAD signal in cancer, and they may provide an idea how cancer with Ras mutation occurs.

Loss of imprinting of IGF2 and the epigenetic progenitor model of cancer

Among the hypotheses discussing cancer formation, the cancer stem cell (CSC) theory is one receiving widespread support. One version of this theory states that changes in otherwise healthy cells can cause formation of tumor- initiating cells (TICs), which have the potential to create precancerous stem cells that can lead to CSC formation. These CSCs can be rare, in contrast to their differentiated progeny, which give rise to the vast majority of the tumor mass in most cancers. Loss of imprinting (LOI) of the insulin-like growth factor-2 (IGF2) gene is one change that can produce these TICs via an epigenetic progenitor model of tumorigenesis. While IGF2 usually supports normal cellular growth, LOI of IGF2 may lead to overexpression of the gene and moreover global chromatin instability. This modification has been observed in many forms of cancer, and given the effect of LOI of IGF2 and its role in cancer, detecting a loss of imprinting in this gene could serve as a valuable diagnostic tool. Preclinical data has shown some progress in identifying therapeutic approaches seeking to exploit this relationship. Thus, further research surrounding LOI of IGF2 could lead to increased understanding of several cancer types and enhance therapies against these diseases.

Involvement of the IGF system in fetal growth and childhood cancer: an overview of potential mechanisms

Fetal growth is determined by a complex interplay of genetic, nutritional, environmental, and hormonal factors. Greater than expected fetal growth has been positively associated with the risk of the development of some cancers in childhood, particularly acute lymphoblastic leukemia, and the biological mechanisms underlying such associations are thought to involve insulin-like growth factors (IGFs). Circulating IGF levels are highly correlated with fetal growth, and IGFs are believed to play an important role in carcinogenesis; however, these two bodies of evidence have not been well integrated and, as a result, the potential underlying biological mechanisms linking the IGF system with the development of specific childhood cancers have not been elucidated. This review aims to draw together and summarize the literature linking the IGF system, rapidity of fetal growth, and risk of some specific childhood cancers; suggest explanations for some of the inconsistencies observed in previous studies of these associations; and propose an integrated framework for the putative involvement of the IGF system in the development of at least some childhood cancers. If the challenges involved in studying the complex IGF system can be overcome, this field presents an exciting opportunity to elucidate etiological pathways to childhood malignancies.

Pathology from evolutionary conflict, with a theory of X chromosome versus autosome conflict over sexually antagonistic traits

Evolutionary conflicts cause opponents to push increasingly hard and in opposite directions on the regulation of traits. One can see only the intermediate outcome from the balance of the exaggerated and opposed forces. Intermediate expression hides the underlying conflict, potentially misleading one to conclude that trait regulation is designed to achieve efficient and robust expression, rather than arising by the precarious resolution of conflict. Perturbation often reveals the underlying nature of evolutionary conflict. Upon mutation or knockout of one side in the conflict, the other previously hidden and exaggerated push on the trait may cause extreme, pathological expression. In this regard, pathology reveals hidden evolutionary design. We first review several evolutionary conflicts between males and females, including conflicts over mating, fertilization, and the growth rate of offspring. Perturbations of these conflicts lead to infertility, misregulated growth, cancer, behavioral abnormalities, and psychiatric diseases. We then turn to antagonism between the sexes over traits present in both males and females. For many traits, the different sexes favor different phenotypic values, and constraints prevent completely distinct expression in the sexes. In this case of sexual antagonism, we present a theory of conflict between X-linked genes and autosomal genes. We suggest that dysregulation of the exaggerated conflicting forces between the X chromosome and the autosomes may be associated with various pathologies caused by extreme expression along the male-female axis. Rapid evolution of conflicting X-linked and autosomal genes may cause divergence between populations and speciation.

Recent advances in understanding the role of diet and obesity in the development of colorectal cancer

Colorectal cancer (CRC) is a major cause of premature death in the UK and many developed countries. However, the risk of developing CRC is well recognised to be associated not only with diet but also with obesity and lack of exercise. While epidemiological evidence shows an association with factors such as high red meat intake and low intake of vegetables, fibre and fish, the mechanisms underlying these effects are only now being elucidated. CRC develops over many years and is typically characterised by an accumulation of mutations, which may arise as a consequence of inherited polymorphisms in key genes, but more commonly as a result of spontaneously arising mutations affecting genes controlling cell proliferation, differentiation, apoptosis and DNA repair. Epigenetic changes are observed throughout the progress from normal morphology through formation of adenoma, and the subsequent development of carcinoma. The reasons why this accumulation of loss of homoeostatic controls arises are unclear but chronic inflammation has been proposed to play a central role. Obesity is associated with increased plasma levels of chemokines and adipokines characteristic of chronic systemic inflammation, and dietary factors such as fish oils and phytochemicals have been shown to have anti-inflammatory properties as well as modulating established risk factors such as apoptosis and cell proliferation. There is also some evidence that diet can modify epigenetic changes. This paper briefly reviews the current state of knowledge in relation to CRC development and considers evidence for potential mechanisms by which diet may modify risk.

Wilms' tumours: about tumour suppressor genes, an oncogene and a chameleon gene

Genes identified as being mutated in Wilms' tumour include TP53, a classic tumour suppressor gene (TSG); CTNNB1 (encoding β-catenin), a classic oncogene; WTX, which accumulating data indicate is a TSG; and WT1, which is inactivated in some Wilms' tumours, similar to a TSG. However, WT1 does not always conform to the TSG label, and some data indicate that WT1 enhances cell survival and proliferation, like an oncogene. Is WT1 a chameleon, functioning as either a TSG or an oncogene, depending on cellular context? Are these labels even appropriate for describing and understanding the function of WT1?

Two groups of DNA methylation markers to classify colorectal cancer into three epigenotypes

A subgroup of colorectal cancer (CRC) shows non-random accumulation of aberrant DNA methylation, so-called CpG island methylator phenotype (CIMP), which was associated with microsatellite instability and BRAF mutation. As just one group of methylation markers was suitable to extract CIMP+/CIMP-high, and had been commonly used in the "one-panel method", it had been unclear whether another cluster of CRC with DNA methylation accumulation exists in microsatellite-stable CRC. We therefore epigenotyped CRC by a comprehensive approach, that is, the two-way unsupervised hierarchical clustering method using highly quantitative methylation data by a single detection method, MALDI-TOF mass spectrometry, on novel regions selected genome-widely through methylated DNA immunoprecipitation on array analysis. CRC was clearly clustered into three DNA methylation epigenotypes, high-, intermediate- and low-methylation epigenotypes (HME, IME, and LME, respectively). Methylation markers are clustered into two distinct groups: Group-1 methylated specifically in HME and including most reported CIMP-related markers; and Group-2 methylated both in HME and IME. While suitable markers to detect a subgroup of CRC with intermediate methylation and correlation to KRAS mutation have been expected to be developed, our data indicated that a "two-panel method" is necessary to properly classify CRC into three epigenotypes, the first panel to extract HME using Group-1 markers, and the second panel to divide the remaining into IME and LME using Group-2 markers. Here we review and compare our recent study and reported CRC classification methods by DNA methylation information, and propose the use of two panels of methylation markers as CRC classifiers.