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

LncRNA THOR promotes human renal cell carcinoma cell growth

BACKGROUND

Recent studies have characterized a novel but extremely conserved long non-coding RNA (LncRNA) THOR. THOR directly associates with insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) to promote mRNA stabilization of key pro-cancerous genes.

RESULTS

Here, we show that THOR is expressed in human renal cell carcinoma (RCC) tissues and established/primary human RCC cells. It was not detected in normal renal tissues nor in HK-2 and primary human renal epithelial cells. THOR silencing (by targeted siRNAs) or CRISPR/Cas9 knockout inhibited RCC cell growth, viability and proliferation in vitro. Reversely, forced over-expression of THOR promoted RCC cell survival and proliferation. IGF2BP1-regulated genes, including IGF2, GLI1 and Myc, were downregulated by THOR silencing or knockout, but they were upregulated after THOR over-expression. In vivo, THOR-knockout 786-O tumors grew significantly slower than the control tumors in nude mice.

CONCLUSION

THOR expression promotes RCC cell growth in vitro and in vivo. THOR could be a novel and important therapeutic target for human RCC.

Increased IGF2BP3 expression promotes the aggressive phenotypes of colorectal cancer cells in vitro and vivo

Previous literatures reported insulin-like growth factor-2 messenger RNA-binding protein 3 (IGF2BP3) is a poor prognostic marker for colorectal cancer (CRC) patients. However, basic research on the effect and biological role of IGF2BP3 in CRC was still scare. Real-time quantitative polymerase chain reaction and western blot analysis were used to examine IGF2BP3 expression level in tumors and paired normal tissues from CRC patients. Tissue microarrays with 192 CRC patients were subjected to immunohistochemical staining to analyze the prognostic value of IGF2BP3. Proliferation assays, migration assays, and xenograft tumor formation in nude mice were performed to assess the biological role of IGF2BP3 in CRC cells. IGF2BP3 expression was significantly upregulated in tumor tissues compared with the matched normal tissues both in messenger RNA and protein level and was associated with worse prognosis. IGF2BP3 knockdown made cell cycle arrest to impair the proliferation ability of CRC cells and further inhibited the xenograft tumor growth in nude mice, also inhibited the migration ability of CRC cells via inducing epithelial-mesenchymal transition. Therefore, the research demonstrated that increased IGF2BP3 expression promoted the aggressive phenotypes of CRC cells. Targeted IGF2BP3 could be a novel and effective gene therapy for CRC patients to make a better prognosis.

IGF2BP1 promotes SRF-dependent transcription in cancer in a m6A- and miRNA-dependent manner

The oncofetal mRNA-binding protein IGF2BP1 and the transcriptional regulator SRF modulate gene expression in cancer. In cancer cells, we demonstrate that IGF2BP1 promotes the expression of SRF in a conserved and N6-methyladenosine (m6A)-dependent manner by impairing the miRNA-directed decay of the SRF mRNA. This results in enhanced SRF-dependent transcriptional activity and promotes tumor cell growth and invasion. At the post-transcriptional level, IGF2BP1 sustains the expression of various SRF-target genes. The majority of these SRF/IGF2BP1-enhanced genes, including PDLIM7 and FOXK1, show conserved upregulation with SRF and IGF2BP1 synthesis in cancer. PDLIM7 and FOXK1 promote tumor cell growth and were reported to enhance cell invasion. Consistently, 35 SRF/IGF2BP1-dependent genes showing conserved association with SRF and IGF2BP1 expression indicate a poor overall survival probability in ovarian, liver and lung cancer. In conclusion, these findings identify the SRF/IGF2BP1-, miRNome- and m6A-dependent control of gene expression as a conserved oncogenic driver network in cancer.

Biological functions, regulatory mechanisms, and disease relevance of RNA localization pathways

The asymmetric subcellular distribution of RNA molecules from their sites of transcription to specific compartments of the cell is an important aspect of post-transcriptional gene regulation. This involves the interplay of intrinsic cis-regulatory elements within the RNA molecules with trans-acting RNA-binding proteins and associated factors. Together, these interactions dictate the intracellular localization route of RNAs, whose downstream impacts have wide-ranging implications in cellular physiology. In this review, we examine the mechanisms underlying RNA localization and discuss their biological significance. We also review the growing body of evidence pointing to aberrant RNA localization pathways in the development and progression of diseases.

Insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) in cancer

The insulin-like growth factor-2 mRNA-binding protein 1 (IGF2BP1) plays essential roles in embryogenesis and carcinogenesis. IGF2BP1 serves as a post-transcriptional fine-tuner regulating the expression of some essential mRNA targets required for the control of tumor cell proliferation and growth, invasion, and chemo-resistance, associating with a poor overall survival and metastasis in various types of human cancers. Therefore, IGF2BP1 has been traditionally regarded as an oncogene and potential therapeutic target for cancers. Nevertheless, a few studies have also demonstrated its tumor-suppressive role. However, the details about the contradictory functions of IGF2BP1 are unclear. The growing numbers of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) have been identified as its direct regulators, during tumor cell proliferation, growth, and invasion in multiple cancers. Thus, the mechanisms of post-transcriptional modulation of gene expression mediated by IGF2BP1, miRNAs, and lncRNAs in determining the fate of the development of tissues and organs, as well as tumorigenesis, need to be elucidated. In this review, we summarized the tissue distribution, expression, and roles of IGF2BP1 in embryogenesis and tumorigenesis, and focused on modulation of the interconnectivity between IGF2BP1 and its targeted mRNAs or non-coding RNAs (ncRNAs). The potential use of inhibitors of IGF2BP1 and its related pathways in cancer therapy was also discussed.

The LINC01138 drives malignancies via activating arginine methyltransferase 5 in hepatocellular carcinoma

Recurrent chromosomal aberrations have led to the discovery of oncogenes or tumour suppressors involved in carcinogenesis. Here we characterized an oncogenic long intergenic non-coding RNA in the frequent DNA-gain regions in hepatocellular carcinoma (HCC), LINC01138 (long intergenic non-coding RNA located on 1q21.2). The LINC01138 locus is frequently amplified in HCC; the LINC01138 transcript is stabilized by insulin like growth factor-2 mRNA-binding proteins 1/3 (IGF2BP1/IGF2BP3) and is associated with the malignant features and poor outcomes of HCC patients. LINC01138 acts as an oncogenic driver that promotes cell proliferation, tumorigenicity, tumour invasion and metastasis by physically interacting with arginine methyltransferase 5 (PRMT5) and enhancing its protein stability by blocking ubiquitin/proteasome-dependent degradation in HCC. The discovery of LINC01138, a promising prognostic indicator, provides insight into the molecular pathogenesis of HCC, and the LINC01138/PRMT5 axis is an ideal therapeutic target for HCC treatment.

The asymmetrically segregating lncRNA cherub is required for transforming stem cells into malignant cells

Tumor cells display features that are not found in healthy cells. How they become immortal and how their specific features can be exploited to combat tumorigenesis are key questions in tumor biology. Here we describe the long non-coding RNA cherub that is critically required for the development of brain tumors in Drosophila but is dispensable for normal development. In mitotic Drosophila neural stem cells, cherub localizes to the cell periphery and segregates into the differentiating daughter cell. During tumorigenesis, de-differentiation of cherub-high cells leads to the formation of tumorigenic stem cells that accumulate abnormally high cherub levels. We show that cherub establishes a molecular link between the RNA-binding proteins Staufen and Syncrip. As Syncrip is part of the molecular machinery specifying temporal identity in neural stem cells, we propose that tumor cells proliferate indefinitely, because cherub accumulation no longer allows them to complete their temporal neurogenesis program.

Many biological signals control how cells grow and divide. However, cancer cells do not obey these growth-restricting signals, and as a result large tumors may develop.

Recent experiments have suggested that stem cells – the precursors to the different types of specialized cells found in the body – are particularly important for generating tumors. A stem cell normally divides unequally to form a self-renewing cell and a more specialized cell (often a progenitor cell that will give rise to increasingly specialized cell types). The timing of when the specialization occurs can be key to guiding the ultimately produced cell progenies to their final identity. However, in a tumor cells can retain the ability to self-renew. Ultimately, the resulting ‘tumor stem cells’ become immortal and proliferate indefinitely. It is not fully understood why this uncontrolled proliferation occurs.

Just like mammals (including humans), fruit flies can develop tumors. Some of the DNA mutations responsible for tumor development were already identified in flies as early as in the 1970s. This has made fruit flies a well-studied model system for uncovering the principle defects that cause tumors to form.

Landskron et al. have now studied the neural stem cells found in brain tumors in fruit flies. Additional DNA mutations were not responsible for these cells becoming immortal. Instead, certain RNA molecules – products that are ‘transcribed’ from the DNA – were present in different amounts in tumor cells. The RNA that showed the greatest increase in tumor cells is a so-called long non-coding RNA named cherub. This RNA molecule has no important role in normal fruit flies, but is critical for tumor formation.

Landskron et al. found that during cell division cherub segregates from the neural stem cells to the newly formed progenitor cells, where it breaks down over time. Progenitor cells that contain high levels of cherub give rise to tumor-generating neural stem cells. At the molecular level, cherubhelps two proteins to interact with each other: one called Syncrip that makes the neural stem cells take on a older identity, and another one (Staufen) that tethers it to the cell membrane. By restricting Syncrip to a particular location in the cell, cherub alters the timing of stem cell specialization, which contributes to tumor formation.

Overall, the results presented by Landskron et al. reveal a new role for long non-coding RNAs: controlling the localization of the proteins that determine the fate of the cell. They also highlight a critical link between the timing of stem cell development and the proliferation of the cells. Further work is now needed to test whether the same control mechanism works in species other than fruit flies.

Mantle cell lymphoma in the era of precision medicine-diagnosis, biomarkers and therapeutic agents

Despite advances in the development of clinical agents for treating Mantle Cell Lymphoma (MCL), treatment of MCL remains a challenge due to complexity and frequent relapse associated with MCL. The incorporation of conventional and novel diagnostic approaches such as genomic sequencing have helped improve understanding of the pathogenesis of MCL, and have led to development of specific agents targeting signaling pathways that have recently been shown to be involved in MCL. In this review, we first provide a general overview of MCL and then discuss about the role of biomarkers in the pathogenesis, diagnosis, prognosis, and treatment for MCL. We attempt to discuss major biomarkers for MCL and highlight published and ongoing clinical trials in an effort to evaluate the dominant signaling pathways as drugable targets for treating MCL so as to determine the potential combination of drugs for both untreated and relapse/refractory cases. Our analysis indicates that incorporation of biomarkers is crucial for patient stratification and improve diagnosis and predictability of disease outcome thus help us in designing future precision therapies. The evidence indicates that a combination of conventional chemotherapeutic agents and novel drugs designed to target specific dysregulated signaling pathways can provide the effective therapeutic options for both untreated and relapse/refractory MCL.

Insulin-Like Growth Factor 2 mRNA-Binding Protein 3 Influences Sensitivity to Anti-IGF System Agents Through the Translational Regulation of IGF1R

Insulin-like growth factor 2 (IGF2) mRNA-binding protein 3 (IGF2BP3) is an oncofetal protein that binds RNA, thereby influencing the fate of target transcripts. IGF2BP3 is synthesized de novo in cancer, where it promotes proliferation, drug resistance, and metastasis via both IGF2-dependent and IGF2-independent mechanisms. Ewing sarcoma (ES) is a rare bone and soft tissue tumor in which the IGF system plays a pivotal role. This study aimed to investigate the effect of IGF2BP3 on the regulation of the IGF system in ES. Among the components of the IGF axis, a direct significant correlation was identified between IGF2BP3 and IGF1R at mRNA and protein levels in two independent series of clinical specimens from patients with localized ES. After the formal demonstration of a direct association between IGF2BP3 and IGF1R mRNA using ribo-immunoprecipitation assay, we performed in vitro studies using A673 and TC-71 ES cell lines to demonstrate that IGF2BP3 loss promotes the downregulation of IGF1R and a decreased biological response to IGF1, represented by reduced migration and cell growth. Additionally, the compensatory activation of insulin receptor (IR) and its mitogenic ligand IGF2 is triggered in some but not all cell lines in response to IGF2BP3-mediated IGF1R loss. These findings have therapeutic implications because cells with a decreased expression of IGF2BP3/IGF1R axis but an increased expression of the IR/IGF2 loop display higher sensitivity to the dual inhibitor OSI-906 than do control cells. Therefore, studies on IGF2BP3, which was confirmed as a post-transcriptional regulator of IGF1R, provide a step forward in the identification of new mechanisms regulating the IGF system. In addition, our results demonstrate that the detection of IGF2BP3 expression should be combined with the assessment of the IGF1R/IR ratio to predict cell responses to anti-IGF1R/IR agents.

Epithelial‑mesenchymal transition in colorectal carcinoma cells is mediated by DEK/IMP3

To investigate the inhibitory effects of DEK/insulin‑like growth factor II mRNA binding protein 3 (IMP3) on epithelial‑mesenchymal transition (EMT) in colorectal carcinoma cells. SW620 and SW480 cell lines were selected. DEK‑interfering lentivirus was transfected to knockdown DEK expression. Subsequently, MTT assays and flow cytometry were utilized to measure cell viability, and apoptosis, respectively. Cell invasion was detected using a Transwell assay. Quantitative polymerase chain reaction and western blot analysis were used to detect the expression of E‑cadherin, vimentin, and matrix metalloproteinase (MMP)‑9. Compared with the blank control, cells transfected with DEK‑interfering lentivirus demonstrated a remarkable reduction in cell viability (P<0.05). The apoptotic rate in the DEK‑interfering lentivirus group was significantly enhanced compared with the blank control group (P<0.05). In the DEK‑interfering lentivirus group, the expression of E‑cadherin was significantly elevated (P<0.05), while the expression of vimentin and MMP‑9 were significantly reduced in both cell lines (P<0.05). The results of the present study demonstrated that EMT of colorectal carcinoma cells was partially mediated by DEK, which likely affected the invasive ability of colorectal carcinoma cells. In addition, cell proliferation and apoptosis were susceptible to DEK silencing. The current study has provided experimental evidence for the treatment of colorectal carcinoma using DEK silencing.

IGF2 mRNA binding protein 3 (IMP3) mediated regulation of transcriptome and translatome in glioma cells

RNA binding proteins mediate global regulation at the level of transcriptome and translatome of a cell. We studied the global level expression changes regulated by IMP3 in transcriptome and translatome by performing microarray using total cellular RNA and heavy polysome derived RNA of IMP3 silenced glioma cells respectively. Differentially regulated transcripts at the transcriptome level (n = 2388) and at the level of translatome (n = 479) were identified. Further, these transcripts were classified as direct and indirect targets on the basis of presence of IMP3 binding site. Additional investigation revealed that direct targets at transcriptome level were found to be associated with processes related to cell cycle, whereas direct targets at the translatome level participated in apoptosis related pathways. Probable mechanism of indirect regulation at both the levels is also investigated. Collectively, our study reveals multi-level gene expression regulation imposed by IMP3 in glioma cells.

Clearance of a persistent picornavirus infection is associated with enhanced pro-apoptotic and cellular immune responses

Long-term persistent viral infections cause substantial morbidity and associated economic losses in human and veterinary contexts. Yet, the mechanisms associated with establishment of persistent infections are poorly elucidated. We investigated immunomodulatory mechanisms associated with clearance versus persistence of foot-and-mouth disease virus (FMDV) in micro-dissected compartments of the bovine nasopharynx by microarray. The use of laser-capture microdissection allowed elucidation of differential gene regulation within distinct anatomic compartments critical to FMDV infection. Analysis of samples from transitional and persistent phases of infection demonstrated significant differences in transcriptome profiles of animals that cleared infection versus those that became persistently infected carriers. Specifically, it was demonstrated that clearance of FMDV from the nasopharyngeal mucosa was associated with upregulation of targets associated with activation of T cell-mediated immunity. Contrastingly, gene regulation in FMDV carriers suggested inhibition of T cell activation and promotion of Th2 polarization. These findings were corroborated by immunofluorescence microscopy which demonstrated relative abundance of CD8⁺ T cells in the nasopharyngeal mucosa in association with clearance of FMDV. The findings presented herein emphasize that a critical balance between Th1 and Th2 -mediated immunity is essential for successful clearance of FMDV infection and should be considered for development of next-generation vaccines and antiviral products.

IMP2 and IMP3 cooperate to promote the metastasis of triple-negative breast cancer through destabilization of progesterone receptor

Triple-negative breast cancer (TNBC) is one of the most aggressive malignancies and is associated with high mortality rates due to the lack of effective therapeutic targets. In this study, we demonstrated that insulin-like growth factor-II mRNA-binding protein 2 and 3 (IMP2 and IMP3) are specifically overexpressed in TNBC and cooperate to promote cell migration and invasion. Downregulation of both IMP2 and IMP3 in TNBC cells was found to produce a synergistic effect in suppressing cell invasion and invadopodia formation, whereas overexpression of IMP2 and IMP3 in luminal subtype cells enhanced epithelial-mesenchymal transition and metastasis. We also showed that IMP2 and IMP3 are direct targets of microRNA-200a (miR-200a), which is downregulated in TNBC. Conversely, IMP2 and IMP3 suppressed the transcription of miR-200a by destabilizing progesterone receptor (PR) mRNA through recruitment of the CCR4-NOT transcription complex subunit 1 (CNOT1) complex. Together, our findings suggest that IMP2 and IMP3 partially determine the characteristic phenotype and synergistically promote the metastasis of TNBC by downregulating PR. The identified IMP2/3-miR-200a-PR axis represents a novel double-negative feedback loop and serves as a new potential therapeutic target for the treatment of TNBC.

Bivalent Epigenetic Control of Oncofetal Gene Expression in Cancer

Multiple mechanisms of epigenetic control that include DNA methylation, histone modification, noncoding RNAs, and mitotic gene bookmarking play pivotal roles in stringent gene regulation during lineage commitment and maintenance. Experimental evidence indicates that bivalent chromatin domains, i.e., genome regions that are marked by both H3K4me3 (activating) and H3K27me3 (repressive) histone modifications, are a key property of pluripotent stem cells. Bivalency of developmental genes during the G₁ phase of the pluripotent stem cell cycle contributes to cell fate decisions. Recently, some cancer types have been shown to exhibit partial recapitulation of bivalent chromatin modifications that are lost along with pluripotency, suggesting a mechanism by which cancer cells reacquire properties that are characteristic of undifferentiated, multipotent cells. This bivalent epigenetic control of oncofetal gene expression in cancer cells may offer novel insights into the onset and progression of cancer and may provide specific and selective options for diagnosis as well as for therapeutic intervention.

IMP3 expression in small-intestine neuroendocrine neoplasms: a new predictor of recurrence

PURPOSE

Small-intestine neuroendocrine neoplasms are heterogeneous neoplasms arising from endocrine cells of the intestinal mucosa. Ki-67 is the main determinant of prognosis in neuroendocrine neoplasms. However, the search for new prognostic makers represents a key point with regard to small-intestine neuroendocrine neoplasms. The oncofetal protein IMP3 plays a role in cell growth and its expression has a prognostic value in lung neoplasms.

METHODS

From January 1998 to August 2015, all the consecutive small-intestine neuroendocrine neoplasms patients suitable for surgery were included: 51 patients (32 males, median age 68 years) had small-intestine neuroendocrine neoplasms classified according to the WHO 2010 classification. In all the cases IMP3 expression was evaluated on primary tumors and, when available, on nodal and distant metastases. The medical records and pathological slides of these patients were used to determine the clinical characteristics, pathological diagnoses, and outcome information.

RESULTS

The overall 5-year and 10-year survival rate were 53.9 and 42% respectively. At Cox proportional hazards regression grading was the major factor influencing both OS and progression-free survival at univariate (p = 0.0002 and 0.0051, respectively) and multivariate analysis (p = 0.0004 and 0.0043, respectively). Also IMP3 expression at the nodal metastases resulted a factor significantly associated with progression-free survival at both univariate (p = 0.0066) and multivariate analysis (p = 0.0059, HR 3.58). IMP3 expression did not correlate with the Ki-67 (p = n.s.).

CONCLUSIONS

In this study, IMP3 at the nodal site resulted to be associated with low progression-free survival in small-intestine neuroendocrine neoplasms, independently of the Ki-67 index. We suggest that the integration of IMP3 and Ki-67 would help better stratify the risk of progression in small-intestine neuroendocrine neoplasms.

Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) promotes lung tumorigenesis via attenuating p53 stability

Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3/IMP3/KOC), initially identified as an RNA-binding protein, is highly expressed in embryonic tissues and a variety of cancers. Previously, our group reported that IGF2BP3 may serve as a potential diagnostic marker for lung cancer. However, little is known about the function of IGF2BP3 in lung cancer development. Here we demonstrate that IGF2BP3 expression was markedly increased in lung cancer tissues compared to normal tissues at both mRNA and protein levels. Overexpression of IGF2BP3 in lung cancer cells promoted cell proliferation, tumor migration and invasion in vitro and in vivo, whereas knockdown of IGF2BP3 exhibited opposite effects. Notably IGF2BP3 was directly associated with a deubiquitinase Ubiquitin specific peptidase 10 (USP10) and attenuated its function in stabilizing p53 protein. Silencing IGF2BP3 expression in lung cancer cells consistently increased the half-life and protein level of p53 and induced G0/G1 arrest. Thus, our data together demonstrate that IGF2BP3 promotes lung tumorigenesis via attenuating p53 protein stability.

iTRAQ-Based Quantitative Proteomic Analyses of High Grade Esophageal Squamous Intraepithelial Neoplasia

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide and is the fourth most lethal cancer in China. Little is known about the proteome of high grade esophageal squamous intraepithelial neoplasia (HGN), which is a premalignant lesion of ESCC. A quantitative proteomic analysis using an isobaric tag for relative and absolute quantification (iTRAQ) approach is used to characterize the protein expression profiles in HGN. Among the 3156 identified proteins, a total of 236 proteins are discovered to be differentially expressed. Compared with paired normal esophageal epithelial tissues, 138 proteins are upregulated and 98 proteins are downregulated in HGN. Bioinformatics analyses are performed according to gene ontology, clusters of orthologous groups, and kyoto encyclopedia of genes and genomes enrichment analyses. Six differentially expressed proteins are chosen and validated by Western blotting. The results of the study increase our understanding of early tumorigenesis during ESCC, and provide insights into the proteome at the initial stages of the disease that can be used to identify potential biomarkers for early diagnosis and for therapeutic targets.

IGF2BP3 as a potential tissue marker for the diagnosis of esophageal high-grade intraepithelial neoplasia

BACKGROUND

The clinical significance of insulin-like growth factor-II mRNA-binding protein-3 (IGF2BP3) in esophageal high-grade intraepithelial neoplasia (HGIN) is not clear. This study was designed to characterize the expression of IGF2BP3 in HGIN.

PATIENTS AND METHODS

IGF2BP3 expression was evaluated by Western blot analyses in 12 cases and by immunohistochemistry (IHC) in 112 cases. The associations between IGF2BP3 expression in HGIN and the clinicopathological parameters were examined.

RESULTS

Moderate to strong IGF2BP3 expression was present in HGIN samples. Using IHC, it was found that IGF2BP3 was positive in 68 (60.71%) cases. Intense IHC of IGF2BP3 in HGIN was associated with a deeper lesion depth, and the lesion depth was the only predictor of the positive expression of IGF2BP3.

CONCLUSION

Our results suggested that IGF2BP3 may be a supplementary tissue marker for preoperative diagnosis of HGIN.

IGF2 mRNA binding protein-2 is a tumor promoter that drives cancer proliferation through its client mRNAs IGF2 and HMGA1

The gene encoding the Insulin-like Growth Factor 2 mRNA binding protein 2/IMP2 is amplified and overexpressed in many human cancers, accompanied by a poorer prognosis. Mice lacking IMP2 exhibit a longer lifespan and a reduced tumor burden at old age. Herein we show in a diverse array of human cancer cells that IMP2 overexpression stimulates and IMP2 elimination diminishes proliferation by 50–80%. In addition to its known ability to promote the abundance of Insulin-like Growth Factor 2/IGF2, we find that IMP2 strongly promotes IGF action, by binding and stabilizing the mRNA encoding the DNA binding protein HMGA1, a known oncogene. HMGA1 suppresses the abundance of IGF binding protein 2/IGFBP2 and Grb14, inhibitors of IGF action. IMP2 stabilization of HMGA1 mRNA plus IMP2 stimulated IGF2 production synergistically drive cancer cell proliferation and account for IMP2’s tumor promoting action. IMP2’s ability to promote proliferation and IGF action requires IMP2 phosphorylation by mTOR.

Some types of cancers develop when genes known as oncogenes or tumor promoters become faulty, and are present at abnormally high levels or inappropriately turned on. For example, cancer cells often have extra copies of the gene IMP2 and therefore produce too much the IMP2 protein. Previous research has shown that mice that lack the IMP2 protein develop fewer cancers and live longer, while patients whose cancers make too much IMP2 have a poorer prognosis.

In healthy cells, the IMP2 protein normally helps to make new gene products by stabilising certain newly produced RNA molecules – the precursors of proteins, and in some cases by promoting the translation of these RNAs into proteins. For example, IMP2 binds to the mRNA that encodes the protein IGF2, which is a protein that helps cells to grow and is commonly produced in large quantities by cancer cells. However, until now it was not clear whether IMP2 only acts by increasing the production of IGF2 or also contributes to cancer growth in other ways.

Using a range of human cancer cell lines, and healthy mouse cells, Dai et al. first confirmed that without IMP2, cancer cells made less IGF2 and grew less quickly. When IGF2 was added to the cells lacking IMP2, it only partially restored their ability to grow. Further experiments revealed that cells without IMP2 had increased levels of proteins that counteract the effects of IGF2. Usually, IMP2 binds and stabilizes the mRNA that encodes the oncogenic protein HMGA1, which is known to regulate the number of ‘anti-IGF2 proteins’. However, without IMP2, the HMGA1 levels drop, which causes an increase of the anti-IGF2 proteins.

This indicates that IMP2 promotes cancer cell growth both by enabling cells to produce more IGF2 and by suppressing inhibitors of IGF2 action. This suggests that cancer patients whose tumors have abnormally high levels of IMP2 may be especially sensitive to drugs that target and inhibit IGF2.

Translational Dysregulation in Cancer: Molecular Insights and Potential Clinical Applications in Biomarker Development

Although transcript levels have been traditionally used as a surrogate measure of gene expression, it is increasingly recognized that the latter is extensively and dynamically modulated at the level of translation (messenger RNA to protein). Over the recent years, significant progress has been made in dissecting the complex posttranscriptional mechanisms that regulate gene expression. This advancement in knowledge came hand in hand with the progress made in the methodologies to study translation both at gene-specific as well as global genomic level. The majority of translational control is exerted at the level of initiation; nonetheless, protein synthesis can be modulated at the level of translation elongation, termination, and recycling. Sequence and structural elements and epitranscriptomic modifications of individual transcripts allow for dynamic gene-specific modulation of translation. Cancer cells usurp the regulatory mechanisms that govern translation to carry out translational programs that lead to the phenotypic hallmarks of cancer. Translation is a critical nexus in neoplastic transformation. Multiple oncogenes and signaling pathways that are activated, upregulated, or mutated in cancer converge on translation and their transformative impact "bottlenecks" at the level of translation. Moreover, this translational dysregulation allows cancer cells to adapt to a diverse array of stresses associated with a hostile microenviroment and antitumor therapies. All elements involved in the process of translation, from the transcriptional template, the components of the translational machinery, to the proteins that interact with the transcriptome, have been found to be qualitatively and/or quantitatively perturbed in cancer. This review discusses the regulatory mechanisms that govern translation in normal cells and how translation becomes dysregulated in cancer leading to the phenotypic hallmarks of malignancy. We also discuss how dysregulated mediators or components of translation can be utilized as biomarkers with potential diagnostic, prognostic, or predictive significance. Such biomarkers have the potential advantage of uniform applicability in the face of inherent tumor heterogeneity and deoxyribonucleic acid instability. As translation becomes increasingly recognized as a process gone awry in cancer and agents are developed to target it, the utility and significance of these potential biomarkers is expected to increase.

IMPs: an RNA-binding protein family that provides a link between stem cell maintenance in normal development and cancer

This review by Degrauwe et al. summarizes our current understanding of the functions of IMPs during normal development and focuses on a series of recent observations that have provided new insight into how their physiological functions enable IMPs to play a potentially key role in cancer stem cell maintenance and tumor growth.

IMPs, also known as insulin-like growth factor 2 (IGF2) messenger RNA (mRNA)-binding proteins (IGF2BPs), are highly conserved oncofetal RNA-binding proteins (RBPs) that regulate RNA processing at several levels, including localization, translation, and stability. Three mammalian IMP paralogs (IMP1–3) have been identified that are expressed in most organs during embryogenesis, where they are believed to play an important role in cell migration, metabolism, and stem cell renewal. Whereas some IMP2 expression is retained in several adult mouse organs, IMP1 and IMP3 are either absent or expressed at very low levels in most tissues after birth. However, all three paralogs can be re-expressed upon malignant transformation and are found in a broad range of cancer types where their expression often correlates with poor prognosis. IMPs appear to resume their physiological functions in malignant cells, which not only contribute to tumor progression but participate in the establishment and maintenance of tumor cell hierarchies. This review summarizes our current understanding of the functions of IMPs during normal development and focuses on a series of recent observations that have provided new insight into how their physiological functions enable IMPs to play a potentially key role in cancer stem cell maintenance and tumor growth.

Prognostic value of high IMP3 expression in solid tumors: a meta-analysis

BACKGROUND

Accumulated studies have investigated the prognostic role of insulin-like growth factor II mRNA-binding protein 3 (IMP3) in various cancers, but inconsistent and controversial results were obtained. Therefore, we performed a systematic review and meta-analysis to investigate the potential value of IMP3 in the prognostic prediction of human solid tumors.

MATERIALS AND METHODS

A systematic literature search in the electronic databases PubMed, Embase, Web of Science, and Cochrane library (updated to April 2016) was conducted to identify eligible studies. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for survival outcomes were calculated and gathered using STATA 12.0 software.

RESULTS

A total of 53 studies containing 8,937 patients with solid tumors were included in this meta-analysis. High IMP3 expression was significantly associated with worse overall survival (OS) of solid tumors (HR =2.08, 95% CI: 1.80-2.42, P<0.001). Similar results were observed in cancer-specific survival (CSS), disease-free survival (DFS), recurrence-free survival (RFS), progression-free survival (PFS), and metastasis-free survival (MFS). Further subgroup analysis stratified by tumor type showed that elevated IMP3 expression was associated with poor OS in renal cell carcinoma (RCC), lung cancer, oral cancer, urothelial carcinoma, hepatocellular carcinoma (HCC), colorectal cancer, pancreatic cancer, gastric cancer, and intrahepatic cholangiocarcinoma (ICC).

CONCLUSION

The current evidence suggests that high IMP3 expression is associated with poor prognosis in most solid tumors. IMP3 is a potential valuable prognostic factor and might serve as a promising biomarker to guide clinical decisions in human solid tumors.

Sequential adaptive changes in a c-Myc-driven model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common cancer that frequently overexpresses the c-Myc (Myc) oncoprotein. Using a mouse model of Myc-induced HCC, we studied the metabolic, biochemical, and molecular changes accompanying HCC progression, regression, and recurrence. These involved altered rates of pyruvate and fatty acid β-oxidation and the likely re-directing of glutamine into biosynthetic rather than energy-generating pathways. Initial tumors also showed reduced mitochondrial mass and differential contributions of electron transport chain complexes I and II to respiration. The uncoupling of complex II's electron transport function from its succinate dehydrogenase activity also suggested a mechanism by which Myc generates reactive oxygen species. RNA sequence studies revealed an orderly progression of transcriptional changes involving pathways pertinent to DNA damage repair, cell cycle progression, insulin-like growth factor signaling, innate immunity, and further metabolic re-programming. Only a subset of functions deregulated in initial tumors was similarly deregulated in recurrent tumors thereby indicating that the latter can "normalize" some behaviors to suit their needs. An interactive and freely available software tool was developed to allow continued analyses of these and other transcriptional profiles. Collectively, these studies define the metabolic, biochemical, and molecular events accompanyingHCCevolution, regression, and recurrence in the absence of any potentially confounding therapies.

Modeling the Attractor Landscape of Disease Progression: a Network-Based Approach

Genome-wide regulatory networks enable cells to function, develop, and survive. Perturbation of these networks can lead to appearance of a disease phenotype. Inspired by Conrad Waddington's epigenetic landscape of cell development, we use a Hopfield network formalism to construct an attractor landscape model of disease progression based on protein- or gene-correlation networks of Parkinson's disease, glioma, and colorectal cancer. Attractors in this landscape correspond to normal and disease states of the cell. We introduce approaches to estimate the size and robustness of these attractors, and take a network-based approach to study their biological features such as the key genes and their functions associated with the attractors. Our results show that the attractor of cancer cells is wider than the attractor of normal cells, suggesting a heterogeneous nature of cancer. Perturbation analysis shows that robustness depends on characteristics of the input data (number of samples per time-point, and the fraction which converge to an attractor). We identify unique gene interactions at each stage, which reflect the temporal rewiring of the gene regulatory network (GRN) with disease progression. Our model of the attractor landscape, constructed from large-scale gene expression profiles of individual patients, captures snapshots of disease progression and identifies gene interactions specific to different stages, opening the way for development of stage-specific therapeutic strategies.

Spatially and temporally regulating translation via mRNA-binding proteins in cellular and neuronal function

Coordinated regulation of mRNA localization and local translation are essential steps in cellular asymmetry and function. It is increasingly evident that mRNA-binding proteins play critical functions in controlling the fate of mRNA, including when and where translation occurs. In this review, we discuss the robust and complex roles that mRNA-binding proteins play in the regulation of local translation that impact cellular function in vertebrates. First, we discuss the role of local translation in cellular polarity and possible links to vertebrate development and patterning. Next, we discuss the expanding role for local protein synthesis in neuronal development and function, with special focus on how a number of neurological diseases have given us insight into the importance of translational regulation. Finally, we discuss the ever-increasing set of tools to study regulated translation and how these tools will be vital in pushing forward and addressing the outstanding questions in the field.

Elucidation of the genetic and epigenetic landscape alterations in RNA binding proteins in glioblastoma

RNA binding proteins (RBPs) have been implicated in cancer development. An integrated bioinformatics analysis of RBPs (n = 1756) in various datasets (n = 11) revealed several genetic and epigenetically altered events among RBPs in glioblastoma (GBM). We identified 13 mutated and 472 differentially regulated RBPs in GBM samples. Mutations in AHNAK predicted poor prognosis. Copy number variation (CNV), DNA methylation and miRNA targeting contributed to RBP differential regulation. Two sets of differentially regulated RBPs that may be implicated in initial astrocytic transformation and glioma progression were identified. We have also identified a four RBP (NOL3, SUCLG1, HERC5 and AFF3) signature, having a unique expression pattern in glioma stem-like cells (GSCs), to be an independent poor prognostic indicator in GBM. RBP risk score derived from the signature also stratified GBM into low-risk and high-risk groups with significant survival difference. Silencing NOL3, SUCLG1 and HERC5 inhibited GSC maintenance. Gene set enrichment analysis of differentially regulated genes between high-risk and low-risk underscored the importance of inflammation, EMT and hypoxia in high-risk GBM. Thus, we provide a comprehensive overview of genetic and epigenetic regulation of RBPs in glioma development and progression.

Expression of IMP3 as a marker for predicting poor outcome in gastroenteropancreatic neuroendocrine neoplasms

The aim of the present study was to investigate the expression and clinical significance of oncofetal protein insulin-like growth factor (IGF) II mRNA-binding protein 3 (IMP3) in the differentiation of gastroenteropancreatic neuroendocrine neoplasm (GEP-NEN). A total of 162 patients who were diagnosed with GEP-NEN, and who underwent surgical or endoscopic resection from January 2006 to March 2013, were enrolled in the study, including 85 cases of grade (G)1 neuroendocrine tumors, 40 cases of G2 neuroendocrine tumors, 28 cases of G3 neuroendocrine carcinomas and 9 cases of mixed stage adenoneuroendocrine carcinomas. The clinical and pathological data were recorded for analysis. The expression of IMP3, cluster of differentiation (CD)44, IGF1 receptor (IGF1R) and matrix metalloproteinase (MMP)2 was determined by immunohistochemistry. SPSS 13.0 software was used for data processing and analyses, and P<0.05 was used to determine significance. Oncofetal protein IMP3 exhibited a high expression rate (74.69%) in GEP-NEN. IMP3-positive cases demonstrated significantly decreased overall and disease-free survival times, as compared with IMP3-negative cases (P=0.012). Overexpression of IMP3 was correlated with tumor grade, clinical stage, tumor size and poor prognosis (all P<0.05). Therefore, patients with overexpressed IMP3 had a poorer prognosis (P<0.01); COX regression analysis revealed that the overexpression of IMP3, the tumor grade, tumor size and metastasis of GEP-NEN were each associated with the clinical outcomes. The results also indicated that the expression rates of CD44, IGF1R and MMP2 in GEP-NEN were 19.75, 53.7 and 55.56%, respectively. While it was negatively associated with the expression of CD44 (r=-0.131; P=0.096), the expression of IMP3 was positively correlated with the expression of IGF1R and MMP2 (r=0.288, P<0.01; r=0.208, P=0.008). In addition, the expression levels of IGF1R and MMP2 were positively associated (r=0.687; P<0.01). In conclusion, high IMP3 expression levels were determined to be associated with a high disease stage in patients with GEP-NEN, thus it may serve as a predictor for metastasis and poor clinical outcomes in GEP-NEN.

THADA fusion is a mechanism of IGF2BP3 activation and IGF1R signaling in thyroid cancer

Thyroid cancer development is driven by known point mutations or gene fusions found in ∼90% of cases, whereas driver mutations in the remaining tumors are unknown. The insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) plays an important role in cancer, yet the mechanisms of its activation in cancer cells remain poorly understood. Using whole-transcriptome and whole-genome analyses, we identified a recurrent fusion between the thyroid adenoma-associated (THADA) gene on chromosome 2 and the LOC389473 gene on chromosome 7 located 12 kb upstream of the IGF2BP3 gene. We show that THADA fusion to LOC389473 and other regions in the vicinity does not result in the formation of a chimeric protein but instead leads to strong overexpression of the full-length IGF2BP3 mRNA and protein, increased IGF2 translation and IGF1 receptor (IGF1R) signaling via PI3K and MAPK cascades, and promotion of cell proliferation, invasion, and transformation. THADA fusions and IGF2BP3 overexpression are found in ∼5% of thyroid cancers that lack any other driver mutations. We also find that strong IGF2BP3 overexpression via gene fusion, amplification, or other mechanisms occurs in 5 to 15% of several other cancer types. Finally, we provide in vitro and in vivo evidence that growth of IGF2BP3-driven cells and tumors may be blocked by IGF1R inhibition, raising the possibility that IGF2BP3 overexpression in cancer cells may predict an anti-IGF1R benefit.

A Concise Atlas of Thyroid Cancer Next-Generation Sequencing Panel ThyroSeq v.2

The next-generation sequencing technology allows high out-put genomic analysis. An innovative assay in thyroid cancer, ThyroSeq® was developed for targeted mutation detection by next generation sequencing technology in fine needle aspiration and tissue samples. ThyroSeq v.2 next generation sequencing panel offers simultaneous sequencing and detection in >1000 hotspots of 14 thyroid cancer-related genes and for 42 types of gene fusions known to occur in thyroid cancer. ThyroSeq is being increasingly used to further narrow the indeterminate category defined by cytology for thyroid nodules. From a surgical perspective, genomic profiling also provides prognostic and predictive information and closely relates to determination of surgical strategy. Both the genomic analysis technology and the informatics for the cancer genome data base are rapidly developing. In this paper, we have gathered existing information on the thyroid cancer-related genes involved in the initiation and progression of thyroid cancer. Our goal is to assemble a glossary for the current ThyroSeq genomic panel that can help elucidate the role genomics play in thyroid cancer oncogenesis.

IMP3 Immunohistochemical Expression Remains Consistent Among All Grades of Gastrointestinal Neuroendocrine Tumors

Insulin-like growth factor-II messenger RNA-binding protein-3 (IMP3), is an oncofetal protein whose aberrant expression has previously been detected in multiple malignant neoplasms. Pulmonary neuroendocrine carcinomas demonstrate increased expression compared with pulmonary carcinoid tumors, but this relationship has not been studied in gastrointestinal neuroendocrine tumors (GINETs). This study examined IMP3 expression in GINETs, with a focus on correlation with established grading criteria. Fifty-four GINETs were immunohistochemically studied using a monoclonal antibody against IMP3. Using established World Health Organization criteria, the cases were stratified by grade and included 31 grade 1 neuroendocrine tumors (G1 GINETs), 15 grade 2 neuroendocrine tumors (G2 GINETs), and 8 neuroendocrine carcinomas (GINECs). The majority (51/54, 94.4%) of GINETs demonstrated IMP3 staining. Thirty cases (55.6%) showed IMP3 cytoplasmic/membranous staining in 60% or greater of tumor cells, with moderate to strong staining in nearly all of these cases (29/30; 96.7%). Of the remaining 24 cases, 3 cases showed no staining, whereas 17 (81%) demonstrated weak staining. When stratified by grade, there was no statistically significant difference in IMP3 staining among the 3 grades of GINETs; of the G1 GINETs, 14 (45.2%) demonstrated staining in at least 60% of tumor cells, compared with 10 (66.7%) G2 GINETs and 6 (75%) GINECs. Hindgut neoplasms of any grade were the most likely to show significant IMP3 staining. Unlike what has been demonstrated in neuroendocrine neoplasms in the lungs, GINETs appear to have a consistent IMP3 expression profile among all tumors grades, which may be reflective of their unique tumor biology.

Neural stem cell-encoded temporal patterning delineates an early window of malignant susceptibility in Drosophila

Pediatric neural tumors are often initiated during early development and can undergo very rapid transformation. However, the molecular basis of this early malignant susceptibility remains unknown. During Drosophila development, neural stem cells (NSCs) divide asymmetrically and generate intermediate progenitors that rapidly differentiate in neurons. Upon gene inactivation, these progeny can dedifferentiate and generate malignant tumors. Here, we find that intermediate progenitors are prone to malignancy only when born during an early window of development while expressing the transcription factor Chinmo, and the mRNA-binding proteins Imp/IGF2BP and Lin-28. These genes compose an oncogenic module that is coopted upon dedifferentiation of early-born intermediate progenitors to drive unlimited tumor growth. In late larvae, temporal transcription factor progression in NSCs silences the module, thereby limiting mitotic potential and terminating the window of malignant susceptibility. Thus, this study identifies the gene regulatory network that confers malignant potential to neural tumors with early developmental origins.

Spontaneous Hepatocellular Carcinoma after the Combined Deletion of Akt Isoforms

Akt is frequently hyperactivated in human cancers and is targeted for cancer therapy. However, the physiological consequences of systemic Akt isoform inhibition were not fully explored. We showed that while combined Akt1 and Akt3 deletion in adult mice is tolerated, combined Akt1 and Akt2 deletion induced rapid mortality. Akt2(-/-) mice survived hepatic Akt1 deletion but all developed spontaneous hepatocellular carcinoma (HCC), which is associated with FoxO-dependent liver injury and inflammation. The gene expression signature of HCC-bearing livers is similar to aggressive human HCC. Consistently, neither Akt1(-/-) nor Akt2(-/-) mice are resistant to diethylnitrosamine-induced hepatocarcinogenesis, and Akt2(-/-) mice display a high incidence of lung metastasis. Thus, in contrast to other cancers, hepatic Akt inhibition induces liver injury that could promote HCC.

Identification of Epigenetic Biomarkers of Lung Adenocarcinoma through Multi-Omics Data Analysis

Epigenetic mechanisms such as DNA methylation or histone modifications are essential for the regulation of gene expression and development of tissues. Alteration of epigenetic modifications can be used as an epigenetic biomarker for diagnosis and as promising targets for epigenetic therapy. A recent study explored cancer-cell specific epigenetic biomarkers by examining different types of epigenetic modifications simultaneously. However, it was based on microarrays and reported biomarkers that were also present in normal cells at a low frequency. Here, we first analyzed multi-omics data (including ChIP-Seq data of six types of histone modifications: H3K27ac, H3K4me1, H3K9me3, H3K36me3, H3K27me3, and H3K4me3) obtained from 26 lung adenocarcinoma cell lines and a normal cell line. We identified six genes with both H3K27ac and H3K4me3 histone modifications in their promoter regions, which were not present in the normal cell line, but present in ≥85% (22 out of 26) and ≤96% (25 out of 26) of the lung adenocarcinoma cell lines. Of these genes, NUP210 (encoding a main component of the nuclear pore complex) was the only gene in which the two modifications were not detected in another normal cell line. RNA-Seq analysis revealed that NUP210 was aberrantly overexpressed among the 26 lung adenocarcinoma cell lines, although the frequency of NUP210 overexpression was lower (19.3%) in 57 lung adenocarcinoma tissue samples studied and stored in another database. This study provides a basis to discover epigenetic biomarkers highly specific to a certain cancer, based on multi-omics data at the cell population level.

RNA-binding protein IGF2BP3 targeting of oncogenic transcripts promotes hematopoietic progenitor proliferation

Posttranscriptional control of gene expression is important for defining both normal and pathological cellular phenotypes. In vitro, RNA-binding proteins (RBPs) have recently been shown to play important roles in posttranscriptional regulation; however, the contribution of RBPs to cell specification is not well understood. Here, we determined that the RBP insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is specifically overexpressed in mixed lineage leukemia-rearranged (MLL-rearranged) B-acute lymphoblastic leukemia (B-ALL), which constitutes a subtype of this malignancy associated with poor prognosis and high risk of relapse. IGF2BP3 was required for the survival of B-ALL cell lines, as knockdown led to decreased proliferation and increased apoptosis. Enforced expression of IGF2BP3 provided murine BM cells with a strong survival advantage, led to proliferation of hematopoietic stem and progenitor cells, and skewed hematopoietic development to the B cell/myeloid lineage. Cross-link immunoprecipitation and high throughput sequencing uncovered the IGF2BP3-regulated transcriptome, which includes oncogenes MYC and CDK6 as direct targets. IGF2BP3 regulated transcripts via targeting elements within 3' untranslated regions (3'UTR), and enforced IGF2BP3 expression in mice resulted in enhanced expression of Myc and Cdk6 in BM. Together, our data suggest that IGF2BP3-mediated targeting of oncogenic transcripts may represent a critical pathogenetic mechanism in MLL-rearranged B-ALL and support IGF2BP3 and its cognate RNA-binding partners as potential therapeutic targets in this disease.

The oncogenic triangle of HMGA2, LIN28B and IGF2BP1 antagonizes tumor-suppressive actions of the let-7 family

The tumor-suppressive let-7 microRNA family targets various oncogene-encoding mRNAs. We identify the let-7 targets HMGA2, LIN28B and IGF2BP1 to form a let-7 antagonizing self-promoting oncogenic triangle. Surprisingly, 3′-end processing of IGF2BP1 mRNAs is unaltered in aggressive cancers and tumor-derived cells although IGF2BP1 synthesis was proposed to escape let-7 attack by APA-dependent (alternative polyadenylation) 3′ UTR shortening. However, the expression of the triangle factors is inversely correlated with let-7 levels and promoted by LIN28B impairing let-7 biogenesis. Moreover, IGF2BP1 enhances the expression of all triangle factors by recruiting the respective mRNAs in mRNPs lacking AGO proteins and let-7 miRNAs. This indicates that the downregulation of let-7, largely facilitated by LIN28B upregulation, and the protection of let-7 target mRNAs by IGF2BP1-directed shielding in mRNPs synergize in enhancing the expression of triangle factors. The oncogenic potential of this triangle was confirmed in ovarian cancer (OC)-derived ES-2 cells transduced with let-7 targeting decoys. In these, the depletion of HMGA2 only diminishes tumor cell growth under permissive conditions. The depletion of LIN28B and more prominently IGF2BP1 severely impairs tumor cell viability, self-renewal and 2D as well as 3D migration. In conclusion, this suggests the targeting of the HMGA2-LIN28B-IGF2BP1 triangle as a promising strategy in cancer treatment.

Regulation of Stem Cell Self-Renewal and Oncogenesis by RNA-Binding Proteins

Throughout their life span, multicellular organisms rely on stem cell systems. During development pluripotent embryonic stem cells give rise to all cell types that make up the organism. After birth, tissue stem cells maintain properly functioning tissues and organs under homeostasis as well as promote regeneration after tissue damage or injury. Stem cells are capable of self-renewal, which is the ability to divide indefinitely while retaining the potential of differentiation into multiple cell types. The ability to self-renew, however, is a double-edged sword; the molecular mechanisms of self-renewal can be a target of malignant transformation driving tumor development and progression. Growing lines of evidence have shown that RNA-binding proteins (RBPs) play pivotal roles in the regulation of self-renewal by modulating metabolism of coding and non-coding RNAs both in normal tissues and in cancers. In this review, we discuss our current understanding of tissue stem cell systems and how RBPs regulate stem cell fates as well as how the regulatory functions of RBPs contribute to oncogenesis.

Urachal Carcinoma of the Bladder: Impact of Clinical and Immunohistochemical Parameters on Prognosis

PURPOSE

Urachal carcinoma of the bladder is a rare malignancy. Its histological phenotype is similar to that of primary bladder and colorectal adenocarcinoma. The aim of this study was to explore the expression and prognostic relevance of 6 select protein markers of urachal carcinoma of the bladder, including p53, Ki67, RHAMM, BGN, IMP3 and MMP-7, which were formerly shown to be prognostic in urothelial carcinoma and colorectal adenocarcinoma.

MATERIALS AND METHODS

Clinical and followup data were obtained on a total of 26 patients with urachal carcinoma of the bladder treated at 2 university hospitals. Immunohistochemical analysis of p53, Ki67, RHAMM, BGN, IMP3 and MMP-7 expression was performed in samples from 15 patients. Clinicopathological parameters and immunohistochemical results were tested for prognostic value on univariable and multivariable analyses.

RESULTS

Followup was 50 months. Five-year overall and progression-free survival was 46% and 32%, respectively. On multivariable analysis a positive resection margin was an independent predictor of poor overall survival (p = 0.025). RHAMM (p = 0.0431), IMP3 (p = 0.0052), Ki67 (p = 0.0006) and p53 (p = 0.0024) expression rates were significantly increased in urachal carcinoma of the bladder cells compared to normal urothelium. IMP3 was elevated in Sheldon tumor stage IIIA compared to IIIB or greater (p = 0.0048). None of the analyzed protein markers was associated with survival.

CONCLUSIONS

The independent prognostic value of a positive resection margin underlines the importance of complete surgical removal of urachal carcinoma of the bladder combined with en bloc resection of the median umbilical ligament and umbilicus. Our results in a limited number of samples show that Ki67, p53, RHAMM and IMP3 expression is enhanced but has no prognostic significance in urachal carcinoma of the bladder.

IDH1 mutation-associated long non-coding RNA expression profile changes in glioma

Isocitrate dehydrogenase 1 (IDH1) mutation is an important prognostic marker in glioma. However, its downstream effect remains incompletely understood. Long non-coding RNAs (lncRNAs) are emerging as important regulators of tumorigenesis in a number of human malignancies, including glioma. Here, we investigated whether and how lncRNA expression profiles would differ between gliomas with or without IDH1 mutation. By using our previously reported lncRNA mining approach, we performed lncRNA profiling in three public glioma microarray datasets. The differential lncRNA expression analysis was then conducted between mutant-type and wild-type IDH1 glioma samples. Comparison analysis identified 14 and 9 lncRNA probe sets that showed significantly altered expressions in astrocytic and oligodendroglial tumors, respectively (fold change ≥ 1.5, false discovery rate ≤ 0.1). Moreover, the differential expressions of these lncRNAs could be confirmed in the independent testing sets. Functional exploration of the lncRNAs by analyzing the lncRNA-protein interactions revealed that these IDH1 mutation-associated lncRNAs were involved in multiple tumor-associated cellular processes, including metabolism, cell growth and apoptosis. Our data suggest the potential roles of lncRNA in gliomagenesis, and may help to understand the pathogenesis of gliomas associated with IDH1 mutation.

A Novel Role for VICKZ Proteins in Maintaining Epithelial Integrity during Embryogenesis

Background

VICKZ (IGF2BP1,2,3/ZBP1/Vg1RBP/IMP1,2,3) proteins bind RNA and help regulate many RNA-mediated processes. In the midbrain region of early chick embryos, VICKZ is expressed in the neural folds and along the basal surface of the neural epithelium, but, upon neural tube closure, is down-regulated in prospective cranial neural crest (CNC) cells, concomitant with their emigration and epithelial-to-mesenchymal transition (EMT). Electroporation of constructs that modulate cVICKZ expression demonstrates that this down-regulation is both necessary and sufficient for CNC EMT. These results suggest that VICKZ down-regulation in CNC cell-autonomously promotes EMT and migration. Reduction of VICKZ throughout the embryo, however, inhibits CNC migration non-cell-autonomously, as judged by transplantation experiments in Xenopus embryos.

Results and Conclusions

Given the positive role reported for VICKZ proteins in promoting cell migration of chick embryo fibroblasts and many types of cancer cells, we have begun to look for specific mRNAs that could mediate context-specific differences. We report here that the laminin receptor, integrin alpha 6, is down-regulated in the dorsal neural tube when CNC cells emigrate, this process is mediated by cVICKZ, and integrin alpha 6 mRNA is found in VICKZ ribonucleoprotein complexes. Significantly, prolonged inhibition of cVICKZ in either the neural tube or the nascent dermomyotome sheet, which also dynamically expresses cVICKZ, induces disruption of these epithelia. These data point to a previously unreported role for VICKZ in maintaining epithelial integrity.

Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions

Hepatocellular carcinoma develops in either chronically injured or seemingly intact livers. To explore the tumorigenic mechanisms underlying these different conditions, we compared the mRNA expression profiles of mouse hepatocellular tumors induced by the repeated injection of CCl₄ or a single diethylnitrosamine (DEN) injection using a cDNA microarray. We identified tumor-associated genes that were expressed differentially in the cirrhotic CCl₄ model (H19, Igf2, Cbr3, and Krt20) and the non-cirrhotic DEN model (Tff3, Akr1c18, Gpc3, Afp, and Abcd2) as well as genes that were expressed comparably in both models (Ly6d, Slpi, Spink3, Scd2, and Cpe). The levels and patterns of mRNA expression of these genes were validated by quantitative RT-PCR analyses. Most of these genes were highly expressed in mouse livers during the fetal/neonatal periods. We also examined the mRNA expression of these genes in mouse tumors induced by thioacetamide, another cirrhotic inducer, and those that developed spontaneously in non-cirrhotic livers and found that they shared a similar expression profile as that observed in CCl₄-induced and DEN-induced tumors, respectively. There was a close relationship between the expression levels of Igf2 and H19 mRNA, which were activated in the cirrhotic models. Our results show that mouse liver tumors reactivate fetal/neonatal genes, some of which are specific to cirrhotic or non-cirrhotic modes of pathogenesis.