Insulin growth factor-2 binding protein 3 (IGF2BP3) is a glioblastoma-specific marker that activates phosphatidylinositol 3-kinase/mitogen-activated protein kinase (PI3K/MAPK) pathways by modulating IGF-2

miR-1275: A single microRNA that targets the three IGF2-mRNA-binding proteins hindering tumor growth in hepatocellular carcinoma

This study aimed to identify a single miRNA or miR (microRNA) which regulates the three insulin-like growth factor-2-mRNA-binding proteins (IGF2BP1, 2 and 3). Bioinformatics predicted miR-1275 to simultaneously target the three IGF2BPs, and screening revealed miR-1275 to be underexpressed in hepatocellular carcinoma (HCC) tissues. Transfection of HuH-7 cells with miR-1275 suppressed IGF2BPs expression and all three IGF2BPs were confirmed as targets of miR-1275. Ectopic expression of miR-1275 and knockdown of IGF2BPs inhibited malignant cell behaviors, and also reduced IGF1R protein and mRNA. Finally IGF1R was validated as a direct target of miR-1275. These findings indicate that the tumor-suppressor miR-1275 can control HCC tumor growth partially through simultaneously regulating the oncogenic IGF2BPs and IGF1R.

IGF2BP3-mediated translation in cell protrusions promotes cell invasiveness and metastasis of pancreatic cancer

Pancreatic cancers are aggressive because they are highly invasive and highly metastatic; moreover, effective treatments for aggressive pancreatic cancers are lacking. Here, we report that IGF2BP3 promoted the invasiveness and metastasis of pancreatic cancers through locally translated IGF2BP3-bound transcripts. In neural cells, transcripts sorted into cytoplasmic RNA granules are transported to dendrites and translated in these dendrites, thereby mediating long-term synaptic plasticity; however, such cytoplasmic RNA granules are not known to contribute to the progression of pancreatic cancer. We show evidence that IGF2BP3 and IGF2BP3-bound transcripts are localized in cytoplasmic RNA granules that accumulate in membrane protrusions of pancreatic cancer cells. Specific IGF2BP3-bound transcripts—ARF6 and ARHGEF4—that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis. Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers. New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

The involvement of insulin-like growth factor 2 binding protein 3 (IMP3) in pancreatic cancer cell migration, invasion, and adhesion

Background

Over-expression of insulin-like growth factor 2 mRNA binding protein 3 (IMP3) is correlated with poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Previous studies examining other cancer types have implicated IMP3 in the regulation of several cellular functions that are characteristic of tumour cells. However, the role of this oncofetal protein in PDAC progression remained unclear.

Methods

Using siRNA, we examined the effect of IMP3 inhibition on the motility, invasive ability, and matrix adhesion of PDAC cells. In addition, we also evaluated the expression of cytoskeleton-associated genes following IMP depletion.

Results

Knockdown of IMP3 significantly decreased the motility, invasion, and extracellular matrix adhesion of select PDAC cells in vitro. In addition, IMP3-depleted cells exhibited lower levels of CD44 protein and KIF11 mRNA. Moreover, we also observed a reduction in downstream RhoA signaling following IMP3 knockdown, indicating that IMP3 modulates the levels of proteins involved in cytoskeletal organization.

Conclusions

These results suggest that IMP3 facilitates PDAC progression by enhancing the pro-metastatic behaviour of tumour cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1251-8) contains supplementary material, which is available to authorized users.

IMP-3 promotes migration and invasion of melanoma cells by modulating the expression of HMGA2 and predicts poor prognosis in melanoma

IGF II mRNA-binding protein 3 (IMP-3) has been reported to be a marker of melanoma progression. However, the mechanisms by which it impacts melanoma are incompletely understood. In this study, we investigate the clinical significance of IMP-3 in melanoma progression and also its underlying mechanisms. We found that IMP-3 expression was much higher in advanced-stage/metastatic melanomas and that it was associated with a poor prognosis (P=0.001). Univariate analysis showed that IMP-3 expression was associated with stage III/IV melanomas (odds ratio=5.40, P=0.031) and the acral lentiginous subtype (odds ratio=3.93, P=0.0034). MeWo cells with overexpression of IMP-3 showed enhanced proliferation and migration and significantly increased tumorigenesis and metastatic ability in nude mice. We further demonstrated that IMP-3 could bind and enhance the stability of the mRNA of high mobility group AT-hook 2 (HMGA2). It was also confirmed that IMP-3 had an important role in melanoma invasion and metastasis through regulating HMGA2 mRNA expression. IMP-3 expression was positively correlated with HMGA2 expression in melanoma cells and also in melanoma tissues. Our results show that IMP-3 expression is a strong prognostic factor for melanoma, especially acral lentiginous melanoma.

MiR-216b is involved in pathogenesis and progression of hepatocellular carcinoma through HBx-miR-216b-IGF2BP2 signaling pathway

This study aims to investigate the expression status of miRNA-216b in familial hepatocellular carcinoma (HCC) and the correlation between miRNA-216b expression and pathogenesis, as well as the progression of HCC. The expression profile of miRNAs in plasma of peripheral blood between HCC patients with HCC family history and healthy volunteers without HCC family history was determined by microarray. Using real-time quantitative PCR to detect the expression in paired tissues from 150 patients with HCC, miR-216b was selected as its expression value in HCC patients was significantly lower compared with healthy volunteers. Next, miR-216b expression and the clinicopathological features of HCC were evaluated. The effect of miR-216b expression on tumor cells was investigated by regulating miR-216b expression in SMMC-7721 and HepG2 in vitro and in vivo. Finally, we explored mRNA targets of miR-216b. In 150 HCC, 37 (75%) tumors showed reduced miR-216b expression comparing with their adjacent liver tissues. The decreased expression of miR-216b was significantly correlated with tumor volume (P=0.044), HBV infection (P=0.026), HBV DNA quantitative (P=0.001) and vascular invasion (P=0.032). The 5-year disease-free survival and overall rates after liver resection in low expression and high expression groups of miR-216b are 62% and 54%, 25% and 20%, respectively. MiR-216b overexpression inhibited cell proliferation, migration and invasion, and miR-216b inhibition did the opposite. The expression of hepatitis B virus x protein (HBx) has tight correlation with downregulation of miR-216b. Furthermore, miR-216b downregulated the expression of insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and exerted its tumor-suppressor function through inhibition of protein kinase B and extracellular signal-regulated kinase signaling downstream of IGF2. MiR-216b inhibits cell proliferation, migration and invasion of HCC by regulating IGF2BP2 and it is regulated by HBx.

Expression of IMP3 and IGF2 in giant cell tumor of spine is associated with tumor recurrence and angiogenesis

PURPOSE

Giant cell tumor (GCT) of bone is a vessel-rich and infiltrative tumor, but the fundamental knowledge of its biological behavior remains unknown now.

METHODS

In this study, we evaluated the expression levels of Insulin-like growth factor 2 mRNA-binding protein 3 (IMP3), Insulin-like growth factor 2 (IGF2) and CD105 in 38 patients with GCT of spine by Immunohistochemical staining. Additionally, we also analyzed their correlations with clinicopathological factors of giant cell tumor of spine.

RESULTS

The results showed that positive expression of IMP3 and IGF2 was tightly related to the tumor extension and local recurrence of GCT (P < 0.05), but it did not indicate any association with patients' age, gender, tumor location and size. The mean microvessel densities (MVDs) of IMP3 and IGF2 were significantly higher in positive group than negative group (P < 0.05). Moreover, a significant correlation was found between IMP3 and IGF2 expression (r = 0.355, P = 0.029). The log-rank test revealed that local recurrence-free survival time was significantly shorter in the IMP3 positive group (P = 0.004), and the difference in the IGF2 positive group and negative group was also statistically significant (P = 0.008).

CONCLUSION

IMP3 and IGF2 might be potential biomarkers for GCT of spine in regulating the angiogenesis of giant cell tumor of bone and predicting the patients' prognosis.

Imp2 regulates GBM progression by activating IGF2/PI3K/Akt pathway

Glioblastomas multiforme (GBM) are the most frequently occurring malignant brain cancers. Treatment for GBM consists of surgical resection and subsequent adjuvant radiation therapy and chemotherapy. Despite this, GBM patient survival is limited to 12-15 months, and researchers are continually trying to develop improved therapy options. Insulin-like growth factor 2 mRNA-binding protein 2 (Imp2) is known to be upregulated in many cancers and is known to regulate the signaling activity of insulin-like growth factor 2 (IGF2). However, relatively little is known about its role in malignant development of GBM. In this study, we first found Imp2 is upregulated in GBM tissues by using clinical samples and public database search. Studies with loss and gain of Imp2 expression in in vitro GBM cell culture system demonstrated the role of Imp2 in promoting GBM cell proliferation, migration, invasion and epithelial-to-mesenchymal transition (EMT). Additionally, our results show that Imp2 regulates the activity of IGF2, which further activates PI3K/Akt signaling, thereby to promote GBM malignancy. Inhibition of Imp2 was also found to sensitize GBM to temozolomide treatment. These observations add to the current knowledge of GBM biology, and may prove useful in development of more effective GBM therapy.

IGF2 signaling and regulation in cancer

Upregulation of IGF2 occurs in both childhood and adult malignancies. Its overexpression is associated with resistance to chemotherapy and worse prognosis. IGF2 promoter usage is developmentally regulated; however, malignant tissues are characterized by re-activation of the fetal IGF2 promoters, especially P3. In this review, we describe the mechanisms of IGF2 signaling and regulation in normal and malignant tissues and their clinical implications.

The oncofetal protein IMP3: a novel grading tool and predictor of poor clinical outcome in human gliomas

Morphologic criteria illustrated in WHO guidelines are the most significant prognostic factor in human gliomas, but novel biomarkers are needed to identify patients with a poorer outcome. The present study examined the expression of the oncofetal protein IMP3 in a series of 135 patients affected by high-grade (grade III and IV) gliomas, correlating the results with proliferative activity, molecular parameters, and clinical and follow-up data. Overall, IMP3 expression was higher in glioblastomas (68%) than in grade III tumors (20%, P < 0.0001), and IMP3-positive high-grade gliomas showed a shorter overall and disease-free survival than negative ones (P = 0.0002 and P = 0.006, resp.). IMP3 expression was significantly associated with the absence of mutations of IDH1 gene (P = 0.0001) and with the unmethylated phenotype of MGMT in high-grade gliomas (P = 0.004). High Ki67 levels were correlated with better prognosis in glioblastomas but IMP3 expression was not correlated with the proliferation index. These findings confirm the role of IMP3 as a marker of poor outcome, also in consideration of its association with IDH1 wild-type phenotype and MGMT unmethylated status. The data suggest that IMP3 staining could identify a subgroup of patients with poor prognosis and at risk of recurrence in high-grade gliomas.

Regulation of tumor cell migration and invasion by the H19/let-7 axis is antagonized by metformin-induced DNA methylation

The imprinted, developmentally regulated H19 long noncoding RNA has been implicated in the pathogenesis of diverse human cancers, but the underlying mechanisms have remained poorly understood. Here, we report that H19 promotes tumor cell migration and invasion by inhibiting let-7, a potent tumor suppressor microRNA that functions to posttranscriptionally suppress the expression of oncogenes that regulate cell growth and motility. We show that H19 depletion impairs, whereas its overexpression enhances the motility and invasiveness of tumor cells. These phenomena occur, at least in part through affecting let-7-mediated regulation of metastasis-promoting genes, including Hmga2, c-Myc and Igf2bp3. This H19/let-7-dependent regulation is recapitulated in vivo where co-expressions of oncogenes and H19 exist in both primary human ovarian and endometrial cancers. Furthermore, we provide evidence that the anti-diabetic drug metformin inhibits tumor cell migration and invasion, partly by downregulating H19 via DNA methylation. Our results reveal a novel mechanism underpinning H19-mediated regulation in metastasis and may explain why in some cases increased let-7 expression unexpectedly correlates with poor prognosis, given the widely accepted role for let-7 as a tumor suppressor. Targeting this newly identified pathway might offer therapeutic opportunities.

CNS-PNETs with C19MC amplification and/or LIN28 expression comprise a distinct histogenetic diagnostic and therapeutic entity

Amplification of the C19MC oncogenic miRNA cluster and high LIN28 expression has been linked to a distinctly aggressive group of cerebral CNS-PNETs (group 1 CNS-PNETs) arising in young children. In this study, we sought to evaluate the diagnostic specificity of C19MC and LIN28, and the clinical and biological spectra of C19MC amplified and/or LIN28+ CNS-PNETs. We interrogated 450 pediatric brain tumors using FISH and IHC analyses and demonstrate that C19MC alteration is restricted to a sub-group of CNS-PNETs with high LIN28 expression; however, LIN28 immunopositivity was not exclusive to CNS-PNETs but was also detected in a proportion of other malignant pediatric brain tumors including rhabdoid brain tumors and malignant gliomas. C19MC amplified/LIN28+ group 1 CNS-PNETs arose predominantly in children <4 years old; a majority arose in the cerebrum but 24 % (13/54) of tumors had extra-cerebral origins. Notably, group 1 CNS-PNETs encompassed several histologic classes including embryonal tumor with abundant neuropil and true rosettes (ETANTR), medulloepithelioma, ependymoblastoma and CNS-PNETs with variable differentiation. Strikingly, gene expression and methylation profiling analyses revealed a common molecular signature enriched for primitive neural features, high LIN28/LIN28B and DNMT3B expression for all group 1 CNS-PNETs regardless of location or tumor histology. Our collective findings suggest that current known histologic categories of CNS-PNETs which include ETANTRs, medulloepitheliomas, ependymoblastomas in various CNS locations, comprise a common molecular and diagnostic entity and identify inhibitors of the LIN28/let7/PI3K/mTOR axis and DNMT3B as promising therapeutics for this distinct histogenetic entity.

The role of the oncofetal IGF2 mRNA-binding protein 3 (IGF2BP3) in cancer

The post-transcriptional control of gene expression mediated by RNA-binding proteins (RBPs), long non-coding RNAs (lncRNAs) as well as miRNAs is essential to determine tumor cell fate and thus is a major determinant in cancerogenesis. The IGF2 mRNA binding protein family (IGF2BPs) comprises three RBPs. Two members of the family, IGF2BP1 and IGF2BP3, are bona fide oncofetal proteins, which are de novo synthesized in various human cancers. In vitro studies revealed that IGF2BPs serve as post-transcriptional fine-tuners modulating the expression of genes implicated in the control of tumor cell proliferation, survival, chemo-resistance and metastasis. Consistently, the expression of both IGF2BP family members was reported to correlate with an overall poor prognosis and metastasis in various human cancers. Due to the fact that most reports used a pan-IGF2BP antibody for studying IGF2BP expression in cancer, paralogue-specific functions can barely be evaluated at present. Nonetheless, the accordance of IGF2BPs' role in promoting an aggressive phenotype of tumor-derived cells in vitro and their upregulated expression in aggressive malignancies provides strong evidence that IGF2BPs are powerful post-transcriptional oncogenes enhancing tumor growth, drug-resistance and metastasis. This suggests IGF2BPs as powerful biomarkers and candidate targets for cancer therapy.

IMP3 expression is associated with epithelial-mesenchymal transition in breast cancer

IMP3 plays an important role in tumor invasion and metastasis, to which epithelial to mesenchymal transition (EMT) also contributes. The purpose of this study was to investigate whether IMP3 can regulate invasion and metastasis through EMT in breast cancers. The protein expression levels of IMP3 and EMT markers were analyzed by immunohistochemistry in 180 paraffin-embedded human breast tissue samples. There was an inverse correlation of IMP3 with E-cadherin protein expression (P = 0.042). IMP3 expression directly correlated with both Slug (P = 0.004) and vimentin (P < 0.001). Changes in E-cadherin, vimentin, and Slug mRNA and protein levels were examined by quantitative real-time reverse polymerase chain reaction (qRT-PCR) and western blotting. Overexpression of IMP3 reduced the expression of E-cadherin and upregulated Slug and vimentin in transfected cells. In contrast, knocking down IMP3 had the opposite expression of the three proteins. Ribo-immunoprecipitation qPCR revealed that IMP3 binds Slug mRNA directly. In a transwell assay, overexpression of Slug rescued the cell migration and invasion caused by silencing IMP3 in MDA-MB-231 cells. On the other hand, knockdown of Slug in T47D-IMP3 cells could also have the opposite change. Our results strengthen the association of IMP3 with the regulation of EMT. Slug is a functional target of IMP3. IMP3 could therefore promote invasion and migration through the EMT in breast cancer cells.

Role of 3’-untranslated region translational control in cancer development, diagnostics and treatment

The messenger RNA 3’-untranslated region (3’UTR) plays an important role in regulation of gene expression on the posttranscriptional level. The 3’UTR controls gene expression via orchestrated interaction between the structural components of mRNAs (cis-element) and the specific trans-acting factors (RNA binding proteins and non-coding RNAs). The crosstalk of these factors is based on the binding sequences and/or direct protein-protein interaction, or just functional interaction. Much new evidence that has accumulated supports the idea that several RNA binding factors can bind to common mRNA targets: to the non-overlapping binding sites or to common sites in a competitive fashion. Various factors capable of binding to the same RNA can cooperate or be antagonistic in their actions. The outcome of the collective function of all factors bound to the same mRNA 3’UTR depends on many circumstances, such as their expression levels, affinity to the binding sites, and localization in the cell, which can be controlled by various physiological conditions. Moreover, the functional and/or physical interactions of the factors binding to 3’UTR can change the character of their actions. These interactions vary during the cell cycle and in response to changing physiological conditions. Abnormal functioning of the factors can lead to disease. In this review we will discuss how alterations of these factors or their interaction can affect cancer development and promote or enhance the malignant phenotype of cancer cells. Understanding these alterations and their impact on 3’UTR-directed posttranscriptional gene regulation will uncover promising new targets for therapeutic intervention and diagnostics. We will also discuss emerging new tools in cancer diagnostics and therapy based on 3’UTR binding factors and approaches to improve them.

Role of IGF2BP3 in trophoblast cell invasion and migration

The insulin-like growth factor-2 mRNA-binding protein 3 (IGF2BP3) is a member of a highly conserved protein family that is expressed specifically in placenta, testis and various cancers, but is hardly detectable in normal adult tissues. IGF2BP3 has important roles in RNA stabilization and translation, especially during early stages of both human and mouse embryogenesis. Placenta is an indispensable organ in mammalian reproduction that connects developing fetus to the uterine wall, and is responsible for nutrient uptake, waste elimination and gas exchange. Fetus development in the maternal uterine cavity depends on the specialized functional trophoblast. Whether IGF2BP3 plays a role in trophoblast differentiation during placental development has never been examined. The data obtained in this study revealed that IGF2BP3 was highly expressed in human placental villi during early pregnancy, especially in cytotrophoblast cells (CTBs) and trophoblast column, but a much lower level of IGF2BP3 was detected in the third trimester placental villi. Furthermore, the expression level of IGF2BP3 in pre-eclamptic (PE) placentas was significantly lower than the gestational age-matched normal placentas. The role of IGF2BP3 in human trophoblast differentiation was shown by in vitro cell invasion and migration assays and an ex vivo explant culture model. Our data support a role of IGF2BP3 in promoting trophoblast invasion and suggest that abnormal expression of IGF2BP3 might be associated with the etiology of PE.

Systematic review of protein biomarkers of invasive behavior in glioblastoma

Glioblastoma (GBM) is an aggressive and incurable brain tumor with a grave prognosis. Recurrence is inevitable even with maximal surgical resection, in large part because GBM is a highly invasive tumor. Invasiveness also contributes to the failure of multiple cornerstones of GBM therapy, including radiotherapy, temozolomide chemotherapy, and vascular endothelial growth factor blockade. In recent years there has been significant progress in the identification of protein biomarkers of invasive phenotype in GBM. In this article, we comprehensively review the literature and survey a broad spectrum of biomarkers, including proteolytic enzymes, extracellular matrix proteins, cell adhesion molecules, neurodevelopmental factors, cell signaling and transcription factors, angiogenic effectors, metabolic proteins, membrane channels, and cytokines and chemokines. In light of the marked variation seen in outcomes in GBM patients, the systematic use of these biomarkers could be used to form a framework for better prediction, prognostication, and treatment selection, as well as the identification of molecular targets for further laboratory investigation and development of nascent, directed therapies.

Posttranscriptional regulation of insulin family ligands and receptors

Insulin system including ligands (insulin and IGFs) and their shared receptors (IR and IGFR) are critical regulators of insulin signaling and glucose homeostasis. Altered insulin system is associated with major pathological conditions like diabetes and cancer. The mRNAs encoding for these ligands and their receptors are posttranscriptionally controlled by three major groups of regulators; (i) alternative splicing regulatory factors; (ii) turnover and translation regulator RNA-binding proteins (TTR-RBPs); and (iii) non-coding RNAs including miRNAs and long non-coding RNAs (lncRNAs). In this review, we discuss the influence of these regulators on alternative splicing, mRNA stability and translation. Due to the pathological impacts of insulin system, we also discussed the possibilities of discovering new potential regulators which will improve understanding of insulin system and associated diseases.

Stimulation of MMP-1 and CCL2 by NAMPT in PDL cells

Periodontitis is an inflammatory disease caused by pathogenic microorganisms and characterized by the destruction of the periodontium. Obese individuals have an increased risk of periodontitis, and elevated circulating levels of adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), may be a pathomechanistic link between both diseases. The aim of this in vitro study was to examine the regulation of periodontal ligament (PDL) cells by NAMPT and its production under inflammatory and infectious conditions. NAMPT caused a significant upregulation of 9 genes and downregulation of 3 genes, as analyzed by microarray analysis. Eight of these genes could be confirmed by real-time PCR: NAMPT induced a significant upregulation of EGR1, MMP-1, SYT7, ITPKA, CCL2, NTM, IGF2BP3, and NRP1. NAMPT also increased significantly the MMP-1 and CCL2 protein synthesis. NAMPT was significantly induced by interleukin-1β and the periodontal microorganism P. gingivalis. NAMPT may contribute to periodontitis through upregulation of MMP-1 and CCL2 in PDL cells. Increased NAMPT levels, as found in obesity, may therefore represent a mechanism whereby obesity could confer an increased risk of periodontitis. Furthermore, microbial and inflammatory signals may enhance the NAMPT synthesis in PDL cells and thereby contribute to the increased gingival and serum levels of this adipokine, as found in periodontitis.

Insulin-like growth factor 2 mRNA binding protein 3 expression is an independent prognostic factor in pediatric pilocytic and pilomyxoid astrocytoma

Prognostic factors in pilocytic astrocytomas (PAs) and pilomyxoid astrocytomas (PMAs) include extent of resection, location, and age, but no molecular markers have been established. Insulin-like growth factor 2 mRNA binding protein 3 (IMP3, IGF2BP3) is predictive of an unfavorable prognosis in other tumors, including high-grade astrocytomas, but its role in PA/PMA is unknown. This study aimed to determine the expression and prognostic value of IMP3 in pediatric PA/PMAs. Insulin-like growth factor 2 mRNA binding protein 3 protein expression was examined by immunohistochemistry in 77 pediatric PAs (n = 70) and PMAs (n = 7) and scored on a subjective scale. Strong diffuse staining for IMP3 was observed in 31% (24 of 77) of tumors and associated with a shorter progression-free survival (hazard ratio, 2.63; p = 0.008). This cohort confirmed previously identified prognostic factors, including extent of resection, age, and tumor location. Currently, only clinical factors are weighed to stratify risk for patients and to identify those who should receive further therapy. Multivariate analyses identified IMP3 expression as an independent prognostic factor when combined with high-/low-risk stratification (hazard ratio, 2.45; p = 0.016). High IMP3, as assessed by immunohistochemistry, has potential use as an additional predictor of poor prognosis in pediatric PA/PMAs and warrants evaluation in larger cohorts.

IR/IGF1R signaling as potential target for treatment of high-grade osteosarcoma

BACKGROUND

High-grade osteosarcoma is an aggressive tumor most often developing in the long bones of adolescents, with a second peak in the 5th decade of life. Better knowledge on cellular signaling in this tumor may identify new possibilities for targeted treatment.

METHODS

We performed gene set analysis on previously published genome-wide gene expression data of osteosarcoma cell lines (n=19) and pretreatment biopsies (n=84). We characterized overexpression of the insulin-like growth factor receptor (IGF1R) signaling pathways in human osteosarcoma as compared with osteoblasts and with the hypothesized progenitor cells of osteosarcoma - mesenchymal stem cells. This pathway plays a key role in the growth and development of bone. Since most profound differences in mRNA expression were found at and upstream of the receptor of this pathway, we set out to inhibit IR/IGF1R using OSI-906, a dual inhibitor for IR/IGF1R, on four osteosarcoma cell lines. Inhibitory effects of this drug were measured by Western blotting and cell proliferation assays.

RESULTS

OSI-906 had a strong inhibitory effect on proliferation of 3 of 4 osteosarcoma cell lines, with IC₅₀s below 100 nM at 72 hrs of treatment. Phosphorylation of IRS-1, a direct downstream target of IGF1R signaling, was inhibited in the responsive osteosarcoma cell lines.

CONCLUSIONS

This study provides an in vitro rationale for using IR/IGF1R inhibitors in preclinical studies of osteosarcoma.

miR-219-5p inhibits receptor tyrosine kinase pathway by targeting EGFR in glioblastoma

Glioblastoma is one of the common types of primary brain tumors with a median survival of 12–15 months. The receptor tyrosine kinase (RTK) pathway is known to be deregulated in 88% of the patients with glioblastoma. 45% of GBM patients show amplifications and activating mutations in EGFR gene leading to the upregulation of the pathway. In the present study, we demonstrate that a brain specific miRNA, miR-219-5p, repressed EGFR by directly binding to its 3′-UTR. The expression of miR-219-5p was downregulated in glioblastoma and the overexpression of miR-219-5p in glioma cell lines inhibited the proliferation, anchorage independent growth and migration. In addition, miR-219-5p inhibited MAPK and PI3K pathways in glioma cell lines in concordance with its ability to target EGFR. The inhibitory effect of miR-219-5p on MAPK and PI3K pathways and glioma cell migration could be rescued by the overexpression of wild type EGFR and vIII mutant of EGFR (both lacking 3′-UTR and thus being insensitive to miR-219-5p) suggesting that the inhibitory effects of miR-219-5p were indeed because of its ability to target EGFR. We also found significant negative correlation between miR-219-5p levels and total as well as phosphorylated forms of EGFR in glioblastoma patient samples. This indicated that the downregulation of miR-219-5p in glioblastoma patients contribute to the increased activity of the RTK pathway by the upregulation of EGFR. Thus, we have identified and characterized miR-219-5p as the RTK regulating novel tumor suppressor miRNA in glioblastoma.

Insulin-Like growth factor-II (IGF-II) prevents proinflammatory cytokine-induced apoptosis and significantly improves islet survival after transplantation

BACKGROUND

The early loss of functional islet mass (50-70%) due to apoptosis after clinical transplantation contributes to islet allograft failure. Insulin-like growth factor (IGF)-II is an antiapoptotic protein that is highly expressed in β-cells during development but rapidly decreases in postnatal life.

METHODS

We used an adenoviral (Ad) vector to overexpress IGF-II in isolated rat islets and investigated its antiapoptotic action against exogenous cytokines interleukin-1β- and interferon-γ-induced islet cell death in vitro. Using an immunocompromised marginal mass islet transplant model, the ability of Ad-IGF-II-transduced rat islets to restore euglycemia in nonobese diabetic/severe combined immunodeficient diabetic recipients was assessed.

RESULTS

Ad-IGF-II transduction did not affect islet viability or function. Ad-IGF-II cytokine-treated islets exhibited decreased cell death (40% ± 2.8%) versus Ad-GFP and untransduced control islets (63.2% ± 2.5% and 53.6% ± 2.3%, respectively). Ad-IGF-II overexpression during cytokine treatment resulted in a marked reduction in terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive apoptotic cells (8.3% ± 1.4%) versus Ad-GFP control (41% ± 4.2%) and untransduced control islets (46.5% ± 6.2%). Western blot analysis confirmed that IGF-II inhibits apoptosis via activation of the phosphatidylinositol 3-kinase/Akt signaling pathway. Transplantation of IGF-II overexpressing islets under the kidney capsule of diabetic mice restored euglycemia in 77.8% of recipients compared with 18.2% and 47.5% of Ad-GFP and untransduced control islet recipients, respectively (P<0.05, log-rank [Mantel-Cox] test).

CONCLUSIONS

Antiapoptotic IGF-II decreases apoptosis in vitro and significantly improved islet transplant outcomes in vivo. Antiapoptotic gene transfer is a potentially powerful tool to improve islet survival after transplantation.

Expression of the oncofetal protein IGF2BP3 in endometrial clear cell carcinoma: assessment of frequency and significance

Insulin-like growth factor-II messenger RNA-binding protein 3 (IGF2BP3 or IMP3) is a biomarker whose expression has been found to be a negative prognostic factor in several neoplasms including ovarian clear cell carcinoma (CCC). In this study, we analyzed the frequency and clinicopathologic significance of IMP3 expression, as assessed by immunohistochemistry and as scored using a modified H-score system, in a cohort of 50 endometrial CCCs. Cases with scores of 0 to 100, 101 to 200, and 201 to 300 were classified as negative/mildly positive (n = 17), moderately positive (n = 20), and strongly positive (n = 13), respectively. A distinctive pattern of increased staining at the myoinvasive front (relative to the main tumor) was evident in 46% of the cases with evaluable foci of myometrial invasion. Moderate/strong IMP3 staining was associated with a tumor architectural pattern that has been reported to be of poor prognostic significance: at least 10% of the tumor composed of solid architecture or individual infiltrating tumor cells (P = .01). Increasing levels of IMP3 expression showed a trend toward decreasing relapse-free survival (RFS; median survival, 75.6, 81.3, and 48.4 months for the negative/mildly, moderately, and strongly positive groups, respectively [P = .09]). However, IMP3 expression was not significantly associated with reduced overall survival or RFS in a multivariate analytic model. The finding in a subset of our cases of increased IMP3 expression at the tumoral myoinvasive front is consistent with a role for IMP3 in invasiveness, as is the trend toward reduced RFS in cases expressing IMP3 at high levels. These preliminary findings suggest that IMP3 expression may be involved in the pathogenesis of CCC and is worthy of further exploration.

IMP2 regulates differentiation potentials of mouse neocortical neural precursor cells

Neural precursor cells (NPCs) in the mammalian neocortex generate various neuronal and glial cell types in a developmental stage-dependent manner. Most neocortical NPCs lose their neurogenic potential after birth. We have previously shown that high-mobility group A (HMGA) proteins confer the neurogenic potential on early-stage NPCs during the midgestation period, although the underlying mechanisms are not fully understood. In this study, we found that HMGA2 promotes the expression of insulin-like growth factor 2 mRNA-binding protein 2 (IMP2, Igf2bp2) in neocortical NPCs. The level of IMP2 was indeed high in early-stage NPCs compared with that in late-stage NPCs. Importantly, over-expression of IMP2 increased the neurogenic potential and suppressed astrocytic differentiation of late-stage NPCs, whereas knockdown of IMP2 promoted astrocytic differentiation and reduced the neurogenic potential of early-stage neocortical NPCs without overtly affecting cell proliferation. Our results thus identified IMP2 as a developmental stage-dependent regulator of the differentiation potentials of NPCs in the mouse neocortex.

Up-regulation of Imp3 confers in vivo tumorigenicity on murine osteosarcoma cells

Osteosarcoma is a high-grade malignant bone tumor that manifests ingravescent clinical behavior. The intrinsic events that confer malignant properties on osteosarcoma cells have remained unclear, however. We previously established two lines of mouse osteosarcoma cells: AX cells, which are able to form tumors in syngeneic mice, and AXT cells, which were derived from such tumors and acquired an increased tumorigenic capacity during tumor development. We have now identified Igf2 mRNA-binding protein3 (Imp3) as a key molecule responsible for this increased tumorigenicity of AXT cells in vivo. Imp3 is consistently up-regulated in tumors formed by AX cells, and its expression in these cells was found to confer malignant properties such as anchorage-independent growth, loss of contact inhibition, and escape from anoikis in vitro. The expression level of Imp3 also appeared directly related to tumorigenic ability in vivo which is the critical determination for tumor-initiating cells. The effect of Imp3 on tumorigenicity of osteosarcoma cells did not appear to be mediated through Igf2-dependent mechanism. Our results implicate Imp3 as a key regulator of stem-like tumorigenic characteristics in osteosarcoma cells and as a potential therapeutic target for this malignancy.

Insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs): post-transcriptional drivers of cancer progression?

The insulin-like growth factor-2 mRNA-binding proteins 1, 2, and 3 (IGF2BP1, IGF2BP2, IGF2BP3) belong to a conserved family of RNA-binding, oncofetal proteins. Several studies have shown that these proteins act in various important aspects of cell function, such as cell polarization, migration, morphology, metabolism, proliferation and differentiation. In this review, we discuss the IGF2BP family’s role in cancer biology and how this correlates with their proposed functions during embryogenesis. IGF2BPs are mainly expressed in the embryo, in contrast with comparatively lower or negotiable levels in adult tissues. IGF2BP1 and IGF2BP3 have been found to be re-expressed in several aggressive cancer types. Control of IGF2BPs’ expression is not well understood; however, let-7 microRNAs, β-catenin (CTNNB1) and MYC have been proposed to be involved in their regulation. In contrast to many other RNA-binding proteins, IGF2BPs are almost exclusively observed in the cytoplasm where they associate with target mRNAs in cytoplasmic ribonucleoprotein complexes (mRNPs). During development, IGF2BPs are required for proper nerve cell migration and morphological development, presumably involving the control of cytoskeletal remodeling and dynamics, respectively. Likewise, IGF2BPs modulate cell polarization, adhesion and migration in tumor-derived cells. Moreover, they are highly associated with cancer metastasis and the expression of oncogenic factors (KRAS, MYC and MDR1). However, a pro-metastatic role of IGF2BPs remains controversial due to the lack of ‘classical’ in vivo studies. Nonetheless, IGF2BPs could provide valuable targets in cancer treatment with many of their in vivo roles to be fully elucidated.

Insulin-like growth factor 2 messenger RNA binding protein 3 (IGF2BP3) is a marker of unfavourable prognosis in colorectal cancer

BACKGROUND

Evidence suggests that insulin-like growth factor 2 messenger RNA binding protein 3 (IGF2BP3, also known as IMP3) represents a promising cancer biomarker. However, the clinical, pathological, molecular and prognostic features of IGF2BP3-positive colorectal cancers remain uncertain.

MATERIALS AND METHODS

We evaluated IGF2BP3 expression by immunohistochemistry in 671 rectal and colon cancer cases that form part of a molecular pathological epidemiology database. Cox proportional hazards regression models were used to compute mortality hazard ratio (HR), adjusting for clinical, pathological and molecular features, including microsatellite instability, the CpG island methylator phenotype, LINE-1 methylation and KRAS, BRAF and PIK3CA mutations.

RESULTS

Among 671 colorectal cancers, 234 (35%) tumours were positive for IGF2BP3. In contrast, normal colorectal epithelium was negative for IGF2BP3 in all 403 specimens of normal mucosa adjacent to carcinoma. IGF2BP3 positivity was associated with poor differentiation (p=0.0003), stage III-IV disease (p=0.0081), BRAF mutation (p=0.031), and LINE-1 hypomethylation (p=0.020). IGF2BP3 positivity was significantly associated with shorter colorectal cancer-specific [log-rank p<0.0001; multivariate HR, 1.37; 95% confidence interval (CI), 1.02-1.84] and overall survival (log-rank p=0.0004; multivariate HR, 1.32; 95% CI, 1.05-1.66).

CONCLUSIONS

IGF2BP3 expression in colorectal cancer is associated with adverse clinical outcome. Our findings support a role for IGF2BP3 as a diagnostic and/or prognostic biomarker in colorectal cancer.

Unique sex-based approach identifies transcriptomic biomarkers associated with non-syndromic craniosynostosis

BACKGROUND

The premature fusion of one cranial suture, also referred to as non-syndromic craniosynostosis, most commonly involves premature fusion of the sagittal, coronal, or metopic sutures, in that order. Population-based epidemiological studies have found that the birth prevalence of single-suture craniosynostosis is both suture- and sex-dependent.

METHODS

Transcriptomic data from 199 individuals with isolated sagittal (n = 100), unilateral coronal (n = 50), and metopic (n = 49) synostosis were compared against a control population (n = 50) to identify transcripts accounting for the different sex-based frequencies observed in this disease.

RESULTS

Differential sex-based gene expression was classified as either gained (divergent) or lost (convergent) in affected individuals to identify transcripts related to disease predilection. Divergent expression was dependent on synostosis sub-type, and was extensive in metopic craniosynostosis specifically. Convergent microarray-based expression was independent of synostosis sub-type, with convergent expression of FBN2, IGF2BP3, PDE1C and TINAGL1 being the most robust across all synostosis sub-types.

CONCLUSIONS

Analysis of sex-based gene expression followed by validation by qRT-PCR identified that concurrent upregulation of FBN2 and IGF2BP3, and downregulation of TINAGL1 in craniosynostosis cases were all associated with increased RUNX2 expression and may represent a transcriptomic signature that can be used to characterize a subset of single-suture craniosynostosis cases.

The zinc finger transcription factor ZKSCAN3 promotes prostate cancer cell migration

In our previous studies, ZKSCAN3 was demonstrated to be over-expressed in invasive colonic tumor cells and their liver metastases, but minimally expressed in adjacent non-transformed tissues. Further preliminary data showed that ZKSCAN3 was expressed in a majority of prostate cancer patient samples, but not in normal prostate tissues. Moreover, the ZKSCAN3 protein is highly expressed in the PC3 prostate cancer cell line, which has high metastatic potential, but little expression was observed in non-metastatic prostate cancer cell lines. Thus, we hypothesized that ZKSCAN3 could participate in tumor metastasis by regulating tumor cell migration. To test this hypothesis, ZKSCAN3 mRNA was knocked down by ZKSCAN3 specific shRNA in PC3 cells and a significant decrease in cell motility was observed. In contrast, when ZKSCAN3 cDNA was overexpressed in PC3 cells, cell detachment was observed and suspension culture induced apoptosis was greatly decreased, suggesting that ZKSCAN3 is able to enhance PC3 cell survival under anoikis stress. Additional wound healing and invasion assays showed that cell migration was enhanced by ZKSCAN3 expression. Interestingly, the ZKSCAN3 gene was amplified in 26% (5/19) of metastatic prostate cancers and 20% (1/5) of lymph node metastases, but there was no amplification found in primary prostate cancers, further supporting the role of ZKSCAN3 in tumor cell migration. In vivo studies using orthotopic tumor models indicated that overexpression of ZKSCAN3 significantly enhanced tumorigenicity. Taken together, we provide evidence that ZKSCAN3, a zinc finger transcription factor, plays a critical role in promoting prostate cancer cell migration.

Regulation of IMP3 by EGFR signaling and repression by ERβ: implications for triple-negative breast cancer

Insulin-like growth factor II (IGF-II) mRNA binding protein 3 (IMP3) is emerging as a useful indicator of the progression and outcome of several cancers. IMP3 expression is associated with triple-negative breast carcinomas (TNBCs), which are aggressive tumors associated with poor outcome. In this study, we addressed the hypothesis that signaling pathways, which are characteristic of TNBCs, impact the expression of IMP3 and that IMP3 contributes to the function of TNBCs. The data obtained reveal that IMP3 expression is repressed specifically by estrogen receptor β (ERβ) and its ligand 3βA-diol but not by ERα. EGF receptor (EGFR) signaling and consequent activation of the MAP kinase pathway induce IMP3 transcription and expression. Interestingly, we discovered that the EGFR promoter contains an imperfect estrogen response element and that ERβ represses EGFR transcription. These data support a mechanism in which ERβ inhibits IMP3 expression indirectly by repressing the EGFR. This mechanism relates to the biology of TNBC, which is characterized by diminished ERβ and increased EGFR expression. We also demonstrate that IMP3 contributes to the migration and invasion of breast carcinoma cells. Given that IMP3 is an mRNA binding protein, we determined that it binds several key mRNAs that could contribute to migration and invasion including CD164 (endolyn) and MMP9. Moreover, expression of these mRNAs is repressed by ERβ and enhanced by EGFR signaling, consistent with our proposed mechanism for the regulation of IMP3 expression in breast cancer cells. Our findings show that IMP3 is an effector of EGFR-mediated migration and invasion and they provide the first indication of how this important mRNA binding protein is regulated in cancer.