Differential insulin-like growth factor II (IGF-II) expression: A potential role for breast cancer survival disparity

Landscape of PCOS co-expression gene and its role in predicting prognosis and assisting immunotherapy in endometrial cancer

BACKGROUND

Endometrial carcinoma (EC) is the sixth most frequent malignancy in women and is often linked to high estrogen exposure. Polycystic ovarian syndrome (PCOS) is a known risk factor for EC, but the underlying mechanisms remain unclear.

METHODS

We investigated shared gene signals and potential biological pathways to identify effective therapy options for PCOS- and EC-related malignancies. Weighted gene expression network analysis (WGCNA) was used to identify genes associated with PCOS and EC using gene expression data from the Gene Expression Omnibus (GEO) and Cancer Genome Atlas (TCGA) datasets. Enrichment analysis using Cluego software revealed that the steroid hormone biosynthetic process was a critical feature in both PCOS and EC. A predictive signature encompassing genes involved in steroid hormone production was developed using multivariate and least absolute shrinkage and selection operator (LASSO) regression analysis to predict the prognosis of EC. Then, we conducted further experimental verification.

RESULTS

Patients in the TCGA cohort with high predictive scores had poorer outcomes than those with low scores. We also investigated the relationship between tumor microenvironment (TME) features and predictive risk rating and found that patients with low-risk scores had higher levels of inflammatory and inhibitory immune cells. Also, we found that immunotherapy against anti-CTLA4 and anti-PD-1/PD-L1 was successful in treating individuals with low risk. Low-risk individuals were more responsive to crizotinib therapy, according to further research performed using the "pRRophetic" R package. We further confirmed that IGF2 expression was associated with tumor cell migration, proliferation, and invasion in EC cells.

CONCLUTIONS

By uncovering the pathways and genes linking PCOS and EC, our findings may provide new therapeutic strategies for patients with PCOS-related EC.

The insulin and IGF signaling pathway sustains breast cancer stem cells by IRS2/PI3K-mediated regulation of MYC

Despite the strong association of the insulin/insulin-like growth factor (IGF) signaling (IIS) pathway with tumor initiation, recurrence, and metastasis, the mechanism by which this pathway regulates cancer progression is not well understood. Here, we report that IIS supports breast cancer stem cell (CSC) self-renewal in an IRS2-phosphatidylinositol 3-kinase (PI3K)-dependent manner that involves the activation and stabilization of MYC. IRS2-PI3K signaling enhances MYC expression through the inhibition of GSK3β activity and suppression of MYC phosphorylation on threonine 58, thus reducing proteasome-mediated degradation of MYC and sustaining active pS62-MYC function. A stable T58A-Myc mutant rescues CSC function in Irs2^-/- cells, supporting the role of this MYC stabilization in IRS2-dependent CSC regulation. These findings establish a mechanistic connection between the IIS pathway and MYC and highlight a role for IRS2-dependent signaling in breast cancer progression.

The Insulin-like Growth Factor Signaling Pathway in Breast Cancer: An Elusive Therapeutic Target

In this review, we provide an overview of the role of the insulin-like growth factor (IGF) signaling pathway in breast cancer and discuss its potential as a therapeutic target. The IGF pathway ligands, IGF-1 and IGF-2, and their receptors, primarily IGF-1R, are important for normal mammary gland biology, and dysregulation of their expression and function drives breast cancer risk and progression through activation of downstream signaling effectors, often in a subtype-dependent manner. The IGF signaling pathway has also been implicated in resistance to current therapeutic strategies, including ER and HER2 targeting drugs. Unfortunately, efforts to target IGF signaling for the treatment of breast cancer have been unsuccessful, due to a number of factors, most significantly the adverse effects of disrupting IGF signaling on normal glucose metabolism. We highlight here the recent discoveries that provide enthusiasm for continuing efforts to target IGF signaling for the treatment of breast cancer patients.

Quantitative assessment of the immune microenvironment in African American Triple Negative Breast Cancer: a case-control study

PURPOSE

Triple negative breast cancer (TNBC) is more common in African American (AA) than Non-AA (NAA) population. We hypothesize that tumor microenvironment (TME) contributes to this disparity. Here, we use multiplex quantitative immunofluorescence to characterize the expression of immunologic biomarkers in the TME in both populations.

PATIENTS AND METHODS

TNBC tumor resection specimen tissues from a 100-patient case: control cohort including 49 AA and 51 NAA were collected. TME markers including CD45, CD14, CD68, CD206, CD4, CD8, CD20, CD3, Ki67, GzB, Thy1, FAP, aSMA, CD34, Col4, VWF and PD-L1 we quantitatively assessed in every field of view. Mean expression levels were compared between cases and controls.

RESULTS

Although no significant differences were detected in individual lymphoid and myeloid markers, we found that infiltration with CD45+ immune cells (p = 0.0102) was higher in TNBC in AA population. AA TNBC tumors also had significantly higher level of lymphocytic infiltration defined as CD45+ CD14- cells (p = 0.0081). CD3+ T-cells in AA tumors expressed significantly higher levels of Ki67 (0.0066) compared to NAAs, indicating that a higher percentage of AA tumors contained activated T-cells. All other biomarkers showed no significant differences between the AA and NAA group.

CONCLUSIONS

While the TME in TNBC is rich in immune cells in both racial groups, there is a numerical increase in lymphoid infiltration in AA compared to NAA TNBC. Significantly, higher activated T cells seen in AA patients raises the possibility that there may be a subset of AA patients with improved response to immunotherapy.

Targeting Adipokines in Obesity-Related Tumors

Obesity, a global epidemic, is an independent risk factor for the occurrence and development of a variety of tumors, such as breast cancer, pancreatic cancer, ovarian cancer and colorectal cancer. Adipocytes are important endocrine cells in the tumor microenvironment of obesity-related tumors, which can secrete a variety of adipokines (such as leptin, adiponectin, estrogen, resistin, MIF and MCP-1, etc.), among which leptin, adiponectin and estrogen are the most in-depth and valuable ones. These adipokines are closely related to tumorigenesis and the progression of tumors. In recent years, more and more studies have shown that under chronic inflammatory conditions such as obesity, adipocytes secrete more adipokines to promote the tumorigenesis and development of tumors. However, it is worth noting that although adiponectin is also secreted by adipocytes, it has an anti-tumor effect, and can cross-talk with other adipokines (such as leptin and estrogen) and insulin to play an anti-tumor effect together. In addition, obesity is the main cause of insulin resistance, which can lead to the increase of the expression levels of insulin and insulin-like growth factor (IGF). As important regulators of blood glucose and lipid metabolism, insulin and IGF also play an important role in the progress of obesity related tumors. In view of the important role of adipokines secreted by adipocytes and insulin/IGF in tumors, this article not only elaborates leptin, adiponectin and estrogen secreted by adipocytes and their mechanism of action in the development of obesity- related tumors, but also introduces the relationship between insulin/IGF, a regulator of lipid metabolism, and obesity related tumors. At the same time, it briefly describes the cancer-promoting mechanism of resistin, MIF and MCP-1 in obesity-related tumors, and finally summarizes the specific treatment opinions and measures for various adipokines and insulin/insulin-like growth factors in recent years.

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.

Spatiotemporal strategies to identify aggressive biology in precancerous breast biopsies

Over 90% of breast cancer is cured; yet there remain highly aggressive breast cancers that develop rapidly and are extremely difficult to treat, much less prevent. Breast cancers that rapidly develop between breast image screening are called "interval cancers." The efforts of our team focus on identifying multiscale integrated strategies to identify biologically aggressive precancerous breast lesions. Our goal is to identify spatiotemporal changes that occur prior to development of interval breast cancers. To accomplish this requires integration of new technology. Our team has the ability to perform single cell in situ transcriptional profiling, noncontrast biological imaging, mathematical analysis, and nanoscale evaluation of receptor organization and signaling. These technological innovations allow us to start to identify multidimensional spatial and temporal relationships that drive the transition from biologically aggressive precancer to biologically aggressive interval breast cancer. This article is categorized under: Cancer > Computational Models Cancer > Molecular and Cellular Physiology Cancer > Genetics/Genomics/Epigenetics.

Methylation of a newly identified region of the INS-IGF2 gene determines IGF2 expression in breast cancer tumors and in breast cancer cells

IGF2 is essential in breast differentiation, lactation, tumor growth, and in breast cancer (BC) development and progression. This growth factor also inhibits apoptosis and promotes metastasis and chemoresistance, contributing to more aggressive tumors. We previously demonstrated that IGF2 protein levels are higher in BC tissues from African American women than in Caucasian women. We also showed that high IGF2 protein levels are expressed in normal breast tissues of African American women while little or no IGF2 was detected in tissues from Caucasian women. Others showed that decreased DNA methylation of the IGF2 gene leads to different BC clinical features. Thus, we designed this study to determine if differentially methylated regions of the IGF2 gene correspond to IGF2 protein expression in paired (Normal/Tumor) breast tissues and in BC cell lines. Methylation analysis was performed using Sodium Bisulphite Analysis and Methylation Sensitive Restriction Enzyme digestion methods. Our results show that a unique site in the INS-IGF2 region is hypermethylated in normal breast and hypomethylated in breast cancer. We designated this region the DVDMR. Furthermore, the methylation levels in the DVDMR significantly correlated with IGF2 protein levels. This novel DMR consists of 257bp localized in the INS-IGF2 gene. We propose that methylation of DVDMR represents a novel epigenetic biomarker that determines the levels of IGF2 protein expression in breast cancer. Since IGF2 promotes metastasis and chemoresistance, we propose that IGF2 levels contribute to BC aggressiveness. Validation of IGF2 as a biomarker will improve diagnosis and treatment of BC patients.

IGF2-derived miR-483-3p associated with Hirschsprung's disease by targeting FHL1

HSCR (Hirschsprung's disease) is a serious congenital defect, and the aetiology of it remains unclear. Many studies have highlighted the significant roles of intronic miRNAs and their host genes in various disease, few was mentioned in HSCR although. In this study, miR-483-3p along with its host gene IGF2 (Insulin-like growth factor 2) was found down-regulated in 60 HSCR aganglionic colon tissues compared with 60 normal controls. FHL1 (Four and a half LIM domains 1) was determined as a target gene of miR-483-3p via dual-luciferase reporter assay, and its expression was at a higher level in HSCR tissues. Here, we study cell migration and proliferation in human 293T and SH-SY5Y cell lines by performing Transwell and CCK8 assays. In conclusion, the knockdown of miR-483-3p and IGF2 both suppressed cell migration and proliferation, while the loss of FHL1 leads to opposite outcome. Furthermore, miR-483-3p mimics could rescue the negative effects on cell proliferation and migration caused by silencing IGF2, while the FHL1 siRNA may inverse the function of miR-483-3p inhibitor. This study revealed that miR-483-3p derived from IGF2 was associated with Hirschsprung's disease by targeting FHL1 and may provide a new pathway to understand the aetiology of HSCR.

Racial disparity in breast cancer: can it be mattered for prognosis and therapy

Breast cancer (BC) has emerged as a deadly disease that affects the lives of millions of women worldwide. It is the second leading cause of cancer-related deaths in the United States. Advancements in BC screening, preventive measures and treatment have resulted in significant decline in BC related deaths. However, unacceptable levels of racial disparity have been consistently reported, especially in African-American (AA) women compared to European American (EA). AA women go through worse prognosis, shorter survival time and higher mortality rates, despite higher cancer incidence reported in EA. These disparities are independent of socioeconomic status, access to healthcare or age, or even the stage of BC. Recent race-specific genetic and epigenetic studies have reported biological causes, which form the crux of this review. However, the developments are just the tip of the iceberg. Prioritizing primary research towards studying race-specific tumor microenvironment and biological composition of the host system in delineating the cause of these disparities is utmost necessary to ameliorate the disparity and design appropriate diagnosis/treatment regimen for AA women suffering from BC. In this review article, we discuss emerging trends and exciting discoveries that reveal how genetic/epigenetic circuitry contributed to racial disparity and discussed the strategies that may help in future therapeutic development.

MiR-483-5p promotes IGF-II transcription and is associated with poor prognosis of hepatocellular carcinoma

The human insulin-like growth factor-II (IGF-II) gene transcribes four mRNAs (P1 mRNA-P4 mRNA), and P3 mRNA overexpression contributes to hepatocarcinogenesis. IGF-II-derived miR-483-5p is implicated in the development of cancers. Here, we investigated the involvement of miR-483-5p in P3 mRNA overexpression regulation and its role in hepatocellular carcinoma. Our results showed that miR-483-5p up-regulated P3 mRNA transcription by targeting the 5′-untranslated region (5′UTR) of P3 mRNA in hepatocellular carcinoma. The mechanism was involved in recruiting of an argonaute 1(Ago1)-argonaute 2 (Ago2) complex to the P3 mRNA 5′UTR and the P3 promoter of IGF-II gene by miR-483-5p, accompanied by increased enrichment of RNA polymerase II and activating histone marks histone 3 lysine 4 trimethylation (H3K4me3), histone 3 lysine 27 acetylation (H3K27ac), and histone 4 lysine 5/8/12/16 acetylation (H4Kac) at the P3 promoter. High miR-483-5p expression was an independent predictor for shorter survival of HCC patients. The findings suggest that miR-483-5p promotes P3 mRNA transcription by recruiting the Ago1-Ago2 complex to the P3 mRNA 5′UTR and is associated with poor prognosis of HCC. Our results display a potential new model for miRNAs to up-regulate gene expression.

Insulin-like growth factor (IGF) axis in cancerogenesis

Determination of the role of insulin-like growth factor (IGF) family components in carcinogenesis of several human tumors is based on numerous epidemiological and pre-clinical studies, experiments in vivo and in vitro and on attempts at application of drugs affecting the IGF axis. Investigative hypotheses in original studies were based on biological functions manifested by the entire family of IGF (ligands, receptors, linking proteins, adaptor molecules). In the context of carcinogenesis the most important functions of IGF family involve intensification of proliferation and inhibition of cell apoptosis and effect on cell transformation through synthesis of several regulatory proteins. IGF axis controls survival and influences on metastases of cells. Interactions of IGF axis components may be of a direct or indirect nature. The direct effects are linked to activation of PI3K/Akt signaling pathway, in which the initiating role is first of all played by IGF-1 and IGF-1R. Activity of this signaling pathway leads to an increased mitogenesis, cell cycle progression, and protection against different apoptotic stresses. Indirect effects of the axis depend on interactions between IGF and other molecules important for cancer etiology (e.g. sex hormones, products of suppressor genes, viruses, and other GFs) and the style of life (nutrition, physical activity). From the clinical point of view, components of IGF system are first of all considered as diagnostic serous and/or tissue biomarkers of a given cancer, prognostic factors and attractive target of modern anti-tumor therapies. Several mechanisms in which IGF system components act in the process of carcinogenesis need to be clarified, mainly due to multifactorial etiology of the neoplasms. Pin-pointing of the role played in carcinogenesis by any single signaling pathway remains particularly difficult. The aim of this review is to summarize the current data of several epidemiological studies, experiments in vitro and on animal models, to increase our understanding of the complex role of IGF family components in the most common human cancers.

IGF2 knockdown in two colorectal cancer cell lines decreases survival, adhesion and modulates survival-associated genes

Increased expression of insulin-like growth factor 2 (IGF2) is found in tumors of colorectal cancer (CRC) patients exhibiting a gained region on chromosome 11q15 and is implicated in poor patient survival. This study analyzes in vitro phenotypic- and gene expression changes associated with IGF2 shRNA-mediated knockdown. Initially, doxycycline inducible IGF2 knockdown cell lines were generated in the CRC cell lines SW480 and LS174T. The cells were analyzed for changes in proliferation, cell cycle, apoptosis, adhesion, and invasion. Expression profiling analysis was performed, and, for a subset of the identified genes, expression was validated by qRT-PCR and Western blot. IGF2 knockdown inhibited cell proliferation in both cell lines induced G1 cell cycle blockade and decreased adhesion to several extracellular matrix proteins. Knockdown of IGF2 did not alter invasiveness in SW480 cells, while a slight increase in apoptosis was seen only in the LS174T cell line. Knockdown of IGF2 in SW480 deregulated 58 genes, several of which were associated with proliferation and cell-cell/cell-ECM contacts. A subset of these genes, including CDK2, YAP1, and BIRC5 (Survivin), are members of a common network. This study supports the concept of direct autocrine/paracrine tumor cell activation through IGF2 and a shows role of IGF2 in CRC proliferation, adhesion and, to a limited extent, apoptosis.

Localization and upregulation of survivin in cancer health disparities: a clinical perspective

Survivin is one of the most important members of the inhibitors of apoptosis protein family, as it is expressed in most human cancers but is absent in normal, differentiated tissues. Lending to its importance, survivin has proven associations with apoptosis and cell cycle control, and has more recently been shown to modulate the tumor microenvironment and immune evasion as a result of its extracellular localization. Upregulation of survivin has been found in many cancers including breast, prostate, pancreatic, and hematological malignancies, and it may prove to be associated with the advanced presentation, poorer prognosis, and lower survival rates observed in ethnically diverse populations.

High IGF2 expression is associated with poor clinical outcome in human ovarian cancer

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

Epigenetic modulation of insulin-like growth factor-II overexpression by hepatitis B virus X protein in hepatocellular carcinoma

Hepatitis B virus X protein (HBx) is involved in the pathogenesis of hepatocellular carcinoma (HCC). Overexpression of the transcripts from the P3 and P4 promoters of the insulin-like growth factor-II (IGF-II) gene is observed in HCC. The present study investigated the involvement of HBx in IGF-II overexpression and its epigenetic regulation. Firstly, the effects of HBx on P3 and P4 mRNA expression, the methylation status of the P3 and P4 promoters, and MBD2 expression were analyzed in human HCC cells and HCC samples. Next, interaction between HBx and MBD2 or CBP/p300 was assessed by co-immunoprecipitation, and HBx-mediated binding of MBD2 and CBP/p300 to the P3 and P4 promoters and the acetylation of the corresponding histones H3 and H4 were evaluated by quantitative chromatin immunoprecipitation. Finally, using siRNA knockdown, we investigated the roles of MBD2 and CBP/p300 in IGF-II overexpression and its epigenetic regulation. Our results showed that HBx promotes IGF-II expression via inducing the hypomethylation of the P3 and P4 promoters, and that HBx increases MBD2 expression, directly interacts with MBD2 and CBP/p300, and elevates their recruitment to the hypomethylated P3 and P4 promoters with increased acetylation levels of the corresponding histones H3 and H4. Further results showed that endogenous MBD2 and CBP/p300 are necessary for HBx-induced IGF-II overexpression and that CBP/p300 presence and CBP/p300-mediated acetylation of histones H3 and H4 are partially required for MBD2 binding and its demethylase activity. These data suggest that HBx induces MBD2-HBx-CBP/p300 complex formation via interaction with MBD2 and CBP/p300, which contributes to the hypomethylation and transcriptional activation of the IGF-II-P3 and P4 promoters and that CBP/p300-mediated acetylation of histones H3 and H4 may be a rate-limiting step for the hypomethylation and activation of these two promoters. This study provides an alternative mechanism for understanding the pathogenesis of HBx-mediated HCC.

Hepatitis B virus X protein promotes P3 transcript expression of the insulin-like growth factor 2 gene via inducing hypomethylation of P3 promoter in hepatocellular carcinoma

BACKGROUND & AIMS

Hepatitis B virus (HBV) X protein (HBx) contributes to hepatocarcinogenesis. The overexpression of transcripts from P3 and P4 promoters of the insulin-like growth factor 2 (IGF2) gene is observed in hepatocellular carcinoma (HCC). Here, we aimed to explore the involvement of HBx in P3-driven mRNA overexpression and underlying epigenetic mechanism.

METHODS

P3 mRNA, P3 methylation status, HBx mRNA and HBx protein were analysed in human HCC samples with and without HBV infection using quantitative RT-PCR, bisulphite sequencing and Western blotting. The effects of HBx on P3 mRNA expression, and P3 transcriptional activity and methylation were further evaluated in HCC cell lines.

RESULTS

P3 mRNA level was higher and P3 methylation level was lower in HBV-positive HCC specimens compared with those of HBV-negative HCC specimens. P3 transcript abundance was positively correlated with HBx expression and negatively correlated with P3 methylation in HCC specimens. The stable expression of HBx upregulated P3 mRNA expression and reduced P3 methylation level in HepG2-HBx cells. The transient expression of HBx stimulated P3 promoter activity and decreased P3 methylation level of P3 promoter-luciferase construct in a dose-dependent manner in HepG2 and Huh-7 cells. Furthermore, HBx mRNA expression was found to be independent predictive factors for both shorter disease-free survival time and shorter overall survival time of HCC patients.

CONCLUSION

HBx may promote IGF2-P3 transcript expression by inducing hypomethylation of P3 promoter and may be associated with an inferior clinical outcome of HBV-related HCC patients. This study provides useful information for understanding the mechanism of HBx-mediated HCC.

Expression of Intratumoral IGF-II Is Regulated by the Gene Imprinting Status in Triple Negative Breast Cancer from Vietnamese Patients

African American women suffer higher incidence and mortality of triple negative breast cancer (TNBC) than Caucasian women. TNBC is very aggressive, causing the worst clinical outcome. We previously demonstrated that tumors from these patients express high IGF-II and exhibit high activation of the IGF signaling pathways. IGF-II gene expression is imprinted (monoallelic), promotes tumor progression, and metastasis and regulates Survivin, a TNBC prognostic marker. Since BC mortality has increased among young Vietnamese women, we analyzed 48 (paired) TNBC samples from Vietnamese patients to assess IGF-II expression. We analyzed all samples by qrtPCR for identification of IGF-II heterozygosity and to determine allelic expression of the IGF-II gene. We also analyzed the tissues for proIGF-II and Survivin by RT-PCR and Western blotting. A total of 28 samples displayed IGF-II heterozygosity of which 78% were biallelic. Tumors with biallelic IGF-II gene expression exhibited the highest levels of proIGF-II and Survivin. Although 100% of these tissues corresponding normal samples were biallelic, they expressed significantly lower levels of or no proIGF-II and Survivin. Thus, IGF-II biallelic gene expression is differentially regulated in normal versus tumor tissues. We propose that intratumoral proIGF-II is dependent on the IGF-II gene imprinting status and it will promote a more aggressive TNBC.

Estrogen Receptor-β and the Insulin-Like Growth Factor Axis as Potential Therapeutic Targets for Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBCs) lack estrogen receptor-α (ERα), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) amplification and account for almost half of all breast cancer deaths. This breast cancer subtype largely affects women who are premenopausal, African-American, or have BRCA1/2 mutations. Women with TNBC are plagued with higher rates of distant metastasis that significantly diminish their overall survival and quality of life. Due to their poor response to chemotherapy, patients with TNBC would significantly benefit from development of new targeted therapeutics. Research suggests that the insulin-like growth factor (IGF) family and estrogen receptor beta-1 (ERβ1), due to their roles in metabolism and cellular regulation, might be attractive targets to pursue for TNBC management. Here, we review the current state of the science addressing the roles of ERβ1 and the IGF family in TNBC. Further, the potential benefit of metformin treatment in patients with TNBC as well as areas of therapeutic potential in the IGF-ERβ1 pathway are highlighted.

Insulin-like growth factor-II: its role in metabolic and endocrine disease

Insulin-like growth factor-II (IGF-II) is a widely expressed 7·5 kDa mitogenic peptide hormone. Although it is abundant in serum, understanding of its physiological role is limited compared with that of IGF-I. IGF-II regulates foetal development and differentiation, but its role in adults is less well understood. Evidence suggests roles in a number of tissues including skeletal muscle, adipose tissue, bone and ovary. Altered IGF-II expression has been observed in metabolic conditions, notably obesity, diabetes and the polycystic ovary syndrome. This article summarizes what is known about the actions of IGF-II and its dysregulation in metabolic and endocrine diseases. The possible causes and consequences of dysregulation are discussed along with the implications for diagnostic tests and future research.

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.

IGF-II and IGFBP-6 regulate cellular contractility and proliferation in Dupuytren's disease

Dupuytren's disease (DD) is a common and heritable fibrosis of the palmar fascia that typically manifests as permanent finger contractures. The molecular interactions that induce the development of hyper-contractile fibroblasts, or myofibroblasts, in DD are poorly understood. We have identified IGF2 and IGFBP6, encoding insulin-like growth factor (IGF)-II and IGF binding protein (IGFBP)-6 respectively, as reciprocally dysregulated genes and proteins in primary cells derived from contracture tissues (DD cells). Recombinant IGFBP-6 inhibited the proliferation of DD cells, patient-matched control (PF) cells and normal palmar fascia (CT) cells. Co-treatments with IGF-II, a high affinity IGFBP-6 ligand, were unable to rescue these effects. A non-IGF-II binding analog of IGFBP-6 also inhibited cellular proliferation, implicating IGF-II-independent roles for IGFBP-6 in this process. IGF-II enhanced the proliferation of CT cells, but not DD or PF cells, and significantly enhanced DD and PF cell contractility in stressed collagen lattices. While IGFBP-6 treatment did not affect cellular contractility, it abrogated the IGF-II-induced contractility of DD and PF cells in stressed collagen lattices. IGF-II also significantly increased the contraction of DD cells in relaxed lattices, however this effect was not evident in relaxed collagen lattices containing PF cells. The disparate effects of IGF-II on DD and PF cells in relaxed and stressed contraction models suggest that IGF-II can enhance lattice contractility through more than one mechanism. This is the first report to implicate IGFBP-6 as a suppressor of cellular proliferation and IGF-II as an inducer of cellular contractility in this connective tissue disease.

Differential expression and signaling activation of insulin receptor isoforms A and B: A link between breast cancer and diabetes

We showed that when insulin-like growth factor II (IGF-II) is highly expressed in breast tissues and cell lines, the IGF-I receptor signaling pathway is highly activated. Since IGF-II activates the insulin receptor (INSR), we propose that the INSR signaling is also activated in this system. We examined the expression of both INSR isoforms, insulin receptor A (INSR-A) and insulin receptor B (INSR-B), and the downstream signaling pathways in breast cancer (BC) cells and in paired (normal/tumor) breast tissues from 100 patients. Analysis was performed by real-time PCR, Western blot, immunohistochemistry, and phospho-ELISA techniques. Tumor tissues and cell lines from African-American patients expressed higher levels of INSR-A, but lower levels of INSR-B. Accordingly, insulin receptor substrate 1 and focal adhesion kinase activation were significantly increased in these women. We conclude that higher INSR-A and lower INSR-B contribute to higher proliferation and lower metabolic response. Thus, differential expression of INSR isoforms represents a potential biological link between BC and diabetes.

Minireview: IGF, Insulin, and Cancer

In recent years, the influence of the IGF system and insulin on cancer growth has been widely studied. Observational human studies have reported increased cancer mortality in those with obesity and type 2 diabetes, which may be attributable to hyperinsulinemia, elevated IGF-I, or potentially both factors. Conversely, those with low insulin, IGF-I and IGF-II levels appear to be relatively protected from cancer development. Initial attention focused on the role of IGF-I in tumor development. The results of these investigations allowed for the development of therapies targeting the IGF-I receptor signaling pathway. However, after in vitro and in vivo studies demonstrating that insulin may also play a significant and independent role in tumorigenesis, insulin is now receiving more attention in this regard. Some studies suggest that targeting insulin receptor signaling may be an important alternative or adjunct to targeting IGF-I receptor signaling. In this minireview, we discuss some of the recent in vitro, animal, and clinical studies that have elaborated our understanding of the influence of IGF and insulin on tumorigenesis. These studies have shed more light on the interaction between insulin and IGF signaling in cancer cells. They have made possible the development of novel targeted therapies and highlighted some of the potential future directions for research and therapeutics.

Differential expression of peroxiredoxins in prostate cancer: consistent upregulation of PRDX3 and PRDX4

BACKGROUND

The peroxiredoxins (PRDXs) are emerging as regulators of antioxidant defense, apoptosis, and therapy resistance in cancer. Because their significance in prostate cancer (PCa) is unclear, we investigated their expression and clinical associations in PCa.

METHODS

Transcript expression of PRDX1-6 in PCa was evaluated in cancer gene microarray datasets, whereas protein expression was evaluated by immunoblotting in prostate cell lines, and by immunohistochemistry (IHC) in prostate tissue microarrays (TMAs) containing tumor (n = 80) and control (n = 17) tissues. PRDX3 was also analyzed in TMAs containing PCa tissues from African-American and Caucasian patients (n = 150 per group). PRDX expression was correlated with patients' clinicopathologic characteristics.

RESULTS

Analysis of PRDX expression in cancer microarray datasets revealed consistent upregulation (tumor vs. normal) of PRDX3 and 4. All PRDXs exhibited elevated protein expression in PCa cell lines, compared with non-tumor cells. IHC revealed significant overexpression of PRDX3 and 4 in PCa, associated with age, increased prostate specific antigen (PSA), tumor stage, or Gleason score. High PRDX3 staining was associated with early age and elevated Gleason score at time of radical prostatectomy in African-American but not in Caucasian patients with PCa. PSA recurrence free survival in patients with low PRDX3 tumor expression was significantly longer in Caucasians compared to African-Americans, but no difference was detected for high expression.

CONCLUSIONS

PRDXs exhibit differential expression in prostate tumors, with PRDX3 and 4 consistently upregulated. Their role in PCa development, and their potential as biological determinants of PCa health disparities and novel therapeutic targets, deserve further investigation.

The correlation between IGF-II and Bcl-2 expression in colorectal adenocarcinoma

Our aim for this study was to investigate the correlation and clinical significance between the expression of IGF-II and Bcl-2 in colorectal adenocarcinoma, especially in terms of the metastasis of colorectal adenocarcinoma. Sixty paraffin embedded samples of colorectal adenocarcinoma were selected, and fifteen normal colorectal tissues were used as controls. IGF-II mRNA was detected using in situ hybridization, and the expression of Bcl-2 along with the proliferating cell nuclear antigen (PCNA) protein was detected through immunohistochemistry. The TUNEL assay was used to detect apoptosis. Specimens with a positive cell ratio less than 30% were defined as negative. The levels of IGF-II mRNA and the Bcl-2 protein were significantly higher in colorectal adenocarcinoma (39.64 ± 7.38% and 30.74 ± 7.22%, respectively) than in normal colorectal tissues (22.56 ± 4.21% and 12.17 ± 1.94%, respectively) (P < 0.01). The levels were related to Dukes' stage and lymph node metastases, but were unrelated to patient age, gender, tumor site, tumor size, and tumor differentiation. Also, a negative correlation was observed between IGF-II mRNA and Bcl-2 protein (P < 0.05) during Dukes' stages. In addition, a positive correlation between IGF-II mRNA and PCNA or apoptosis, as well as a negative correlation between Bcl-2 and apoptosis were observed (P < 0.01). There was no correlation between Bcl-2 and PCNA (P > 0.05). The patients detected as IGF-II mRNA (+) and Bcl-2 (-) showed the worst prognosis. The expression of IGF-II and Bcl-2 was correlated with the clinical manifestation of colorectal adenocarcinoma; thus, the assessment of both IGF-II and Bcl-2's status will provide important information regarding the diagnosis and prognosis of colorectal adenocarcinoma.

Insulin-like growth factors I and II receptors in the breast cancer survival disparity among African-American women

OBJECTIVE

African-American (AA) women with breast cancer are more likely to have advanced disease at diagnosis, higher risk of recurrence and poorer prognosis than Caucasian (CA) women. We have recently shown higher insulin-like growth factor II (IGF-II) expression in paired breast tissue samples from AA women as compared to CA women. IGF-II is a potent mitogen that induces cell proliferation and survival signals through activation of the IGF-I and Insulin receptors (IGF-IR, IR) while IGF-II circulating levels are regulated by cellular uptake through the IGF2 receptor. We hypothesize that differential expression of the IGF1R and IGF2R among AA and CA women potentiates IGF-II mitogenic effects, thus contributing to the health disparity observed between these ethnic groups.

DESIGN

We examined IGF-IR and IGF2R mRNA, protein expression and IGF1R phosphorylation in paired breast tissue samples from AA and CA women by Real Time-PCR, Western blot analysis, immunohistochemistry and ELISA techniques.

RESULTS

Our results showed significantly increased expression of IGF1R in AA normal tissues as compared to CA normal tissues. IGF1R expression was similar between AA normal and malignant tissues, while IGF1R, IRS-1 and Shc phosphorylation was significantly higher in AA tumor samples. Significantly higher levels of IGF2R were found in CA tumor samples as compared to AA tumor samples.

CONCLUSIONS

We conclude that IGF1R and IGF2R differential expression may contribute to the increased risk of malignant transformation in young AA women and to the more aggressive breast cancer phenotype observed among AA breast cancer patients and represent, along with IGF-II, potential therapeutic targets in breast cancer.