Expression of the RNA-binding protein VICKZ in normal hematopoietic tissues and neoplasms

Insulin-like Growth Factor II mRNA-binding Protein 3 is a Highly Sensitive Marker for Intravascular Large B-cell Lymphoma: Immunohistochemical Analysis of 152 Pathology Specimens From 88 Patients

Intravascular large B-cell lymphoma (IVLBCL) is a rare type of aggressive extranodal large B-cell lymphoma characterized by the selective growth of lymphoma cells within the lumina of blood vessels, particularly capillaries. IVLBCL lacks mass formation, and its diagnosis can be challenging. We analyzed the utility of insulin-like growth factor II mRNA-binding protein 3 (IMP3) immunohistochemistry for IVLBCL diagnosis in various organs. Double staining with paired box 5 (PAX5) was performed for validation. Overall, 152 pathological specimens (111 positive and 41 negative for IVLBCL) obtained from 88 patients with a diagnosis of IVLBCL were stained for IMP3 and IMP3/PAX5. As negative controls, 40 pathology specimens from 38 patients with no history of IVLBCL or other B-cell lymphomas were stained for IMP3, which comprised 31 benign pathological specimens from 29 patients in whom malignancy was suspected, 7 cases of appendicitis with intravascular and/or intralymphatic lymphoid proliferations, and 2 cases of intravascular natural killer/T-cell lymphoma. All mononuclear cells with cytoplasmic staining were considered positive for IMP3 expression, but expression restricted to germinal center B cells was excluded from evaluation. All 111 IVLBCL pathological specimens were positive for IMP3 and IMP3/PAX5. In addition, 11 of the 41 specimens originally diagnosed as IVLBCL-negative showed IMP3/PAX5 double-positive cells, raising the suspicion of IVLBCL. However, of the 40 negative control samples, IMP3-positive non-germinal center B cells were detected in only 2 samples ( P = 0.0131) and no intravascular IMP3-positive B cells suspicious for IVLBCL were identified. Altogether, IMP3 immunohistochemistry is a highly sensitive marker of IVLBCL and can be a helpful adjunct for IVLBCL diagnosis.

Deciphering the Molecular Mechanism Underlying African Animal Trypanosomiasis by Means of the 1000 Bull Genomes Project Genomic Dataset

Simple Summary

Climate change is increasing the risk of spreading vector-borne diseases such as African Animal Trypanosomiasis (AAT), which is causing major economic losses, especially in sub-Saharan African countries. Mainly considering this disease, we have investigated transcriptomic and genomic data from two cattle breeds, namely Boran and N‘Dama, where the former is known for its susceptibility and the latter one for its tolerance to the AAT. Despite the rich literature on this disease, there is still a need to investigate underlying genetic mechanisms to decipher the complex interplay of regulatory SNPs (rSNPs), their corresponding gene expression profiles and the downstream effectors associated with the AAT disease. The findings of this study complement our previous results, which mainly involve the upstream events, including transcription factors (TFs) and their co-operations as well as master regulators. Moreover, our investigation of significant rSNPs and effectors found in the liver, spleen and lymph node tissues of both cattle breeds could enhance the understanding of distinct mechanisms leading to either resistance or susceptibility of cattle breeds.

Abstract

African Animal Trypanosomiasis (AAT) is a neglected tropical disease and spreads by the vector tsetse fly, which carries the infectious Trypanosoma sp. in their saliva. Particularly, this parasitic disease affects the health of livestock, thereby imposing economic constraints on farmers, costing billions of dollars every year, especially in sub-Saharan African countries. Mainly considering the AAT disease as a multistage progression process, we previously performed upstream analysis to identify transcription factors (TFs), their co-operations, over-represented pathways and master regulators. However, downstream analysis, including effectors, corresponding gene expression profiles and their association with the regulatory SNPs (rSNPs), has not yet been established. Therefore, in this study, we aim to investigate the complex interplay of rSNPs, corresponding gene expression and downstream effectors with regard to the AAT disease progression based on two cattle breeds: trypanosusceptible Boran and trypanotolerant N’Dama. Our findings provide mechanistic insights into the effectors involved in the regulation of several signal transduction pathways, thereby differentiating the molecular mechanism with regard to the immune responses of the cattle breeds. The effectors and their associated genes (especially MAPKAPK5, CSK, DOK2, RAC1 and DNMT1) could be promising drug candidates as they orchestrate various downstream regulatory cascades in both cattle breeds.

Immunohistochemical Study of IMP3 Expression in Laryngeal Squamous Cell Carcinoma

BACKGROUND: IMP3 is an RNA binding protein, which is strongly expressed in malignant tumors, promoting tumor cell proliferation. AIM: The aim of the study was to evaluate the expression of IMP3 in laryngeal squamous cell carcinoma (SCC) and to correlate the expression of IMP3 with available clinicopathological data. METHODS: Sixty one total laryngectomy and laryngoscopic biopsies; collected from the Pathology Department, Faculty of Medicine, Cairo University. Two slides were prepared from each paraffin embedded tumor block, one slide for Hematoxylin and Eosin staining, and the other for immunohistochemical staining by IMP3 polyclonal antibody. RESULTS: Thirty-seven cases (60.7%) showed positive IMP3 expression, and a statistically significant correlation was found between IMP3 expressions in normal, dysplastic epithelium/in situ component, and the invasive malignant tumor tissue. Correlations between IMP3 expression and other available clinicopathological data were all non-significant. CONCLUSION: This study suggests that IMP3 might play a role in laryngeal SCC carcinogenesis and progression process from normal to dysplastic to malignant epithelium, and thus IMP3 might be targeted by gene therapy.

IGF2BP3 Associates with Proliferative Phenotype and Prognostic Features in B-Cell Acute Lymphoblastic Leukemia

The oncofetal protein insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) belongs to a family of RNA-binding proteins involved in localization, stability, and translational regulation of target RNAs. IGF2BP3 is used as a diagnostic and prognostic marker in several malignancies. Although the prognosis of pediatric B-cell acute lymphoblastic leukemia (B-ALL) has improved, a subgroup of patients exhibits high-risk features and suffer from disease recurrence. We sought to identify additional biomarkers to improve diagnostics, and we assessed expression of IGF2BP3 in a population-based pediatric cohort of B-ALL using a tissue microarray platform. The majority of pediatric B-ALL cases were positive for IGF2BP3 immunohistochemistry and were associated with an increased proliferative phenotype and activated STAT5 signaling pathway. Two large gene expression data sets were probed for the expression of IGF2BP3-the highest levels were seen among the B-cell lymphomas of a germinal center origin and well-established (KMT2A-rearranged and ETV6-RUNX1) and novel subtypes of B-ALL (e.g., NUTM1 and ETV6-RUNX1-like). A high mRNA for IGF2BP3 was associated with a proliferative "metagene" signature and a high expression of CDK6 in B-ALL. A low expression portended inferior survival in a high-risk cohort of pediatric B-ALL. Overall, our results show that IGF2BP3 shows subtype-specificity in expression and provides prognostic utility in high-risk B-ALL.

RNA Regulators in Leukemia and Lymphoma

Posttranscriptional regulation of mRNA is a powerful and tightly controlled process in which cells command the integrity, diversity, and abundance of their protein products. RNA-binding proteins (RBPs) are the principal players that control many intermediary steps of posttranscriptional regulation. Recent advances in this field have discovered the importance of RBPs in hematological diseases. Herein we will review a number of RBPs that have been determined to play critical functions in leukemia and lymphoma. Furthermore, we will discuss the potential therapeutic strategies that are currently being studied to specifically target RBPs in these diseases.

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.

Localization of cofilin mRNA to the leading edge of migrating cells promotes directed cell migration

mRNA trafficking, which enables the localization of mRNAs to particular intracellular targets, occurs in a wide variety of cells. The importance of the resulting RNA distribution for cellular functions, however, has been difficult to assess. We have found that cofilin-1 mRNA is rapidly localized to the leading edge of human lung carcinoma cells and that VICKZ family RNA-binding proteins help mediate this localization through specific interactions with the 3′UTR of cofilin mRNA. Using a phagokinetic assay for cell motility, we have been able to quantify the effect of mRNA localization on the rescue of lung carcinoma cells in which cofilin was knocked down by using short hairpin RNA (shRNA). Although restoring cofilin protein to normal endogenous levels rescues general lamellipodia formation around the periphery of the cell, only when the rescuing cofilin mRNA can localize to the leading edge is it capable of also fully rescuing directed cell movement. These results demonstrate that localization of an mRNA can provide an additional level of regulation for the function of its protein product.

IGF2BP1 harbors prognostic significance by gene gain and diverse expression in neuroblastoma

PURPOSE

Chromosomal 17q21-ter gain in neuroblastoma is both a common and prognostically significant event. The insulin-like growth factor-2 mRNA-binding protein 1 (IGF2BP1) gene is located near the proximal edge of this region. Here, its prognostic value is evaluated in neuroblastoma.

METHODS

The mRNA expression of IGF2BP family members was first evaluated by microarray data sets. In addition, in a separate cohort of 69 tumors, IGF2BP1 gene copy number, mRNA, and protein abundance were determined and compared with clinical parameters.

RESULTS

In two independent microarray data sets, 77% to 100% of tumors had substantial IGF2BP1 mRNA levels measured. High IGF2BP1 transcript abundance was significantly associated with stage 4 tumors (P < .001) and decreased patient survival (P < .001). IGF2BP1 was also associated with MYCN gene amplification and MYCN mRNA abundance. In the 69 neuroblastoma samples, IGF2BP1 DNA copy number (increased in 84% of tumors), mRNA, and protein abundance were significantly higher in stage 4 compared with stage 1 tumors. Importantly, IGF2BP1 protein levels were associated with lower overall patient survival (P = .012) and positively correlated with MYCN mRNA, even when excluding MYCN-amplified tumors. Moreover, IGF2BP1 clearly affected MYCN expression and neuroblastoma cell survival in vitro.

CONCLUSION

In neuroblastoma, IGF2BP1 was expressed in the majority of neuroblastoma specimens analyzed and was associated with lower overall patient survival and MYCN abundance. These data demonstrate that IGF2BP1 is a potential oncogene and an independent negative prognostic factor in neuroblastoma.

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.

VICKZ2 protein expression in ovarian serous carcinoma effusions is associated with poor survival

The involvement of VICKZ proteins has been implicated in a large number of cancers. The aim of the present study was to investigate the biological and clinical role of VICKZ proteins in ovarian carcinoma (OC). VICKZ1-3 protein expression was analyzed in 82 serous OC specimens (51 effusions, 14 primary carcinomas, 17 solid metastases) by immunoblotting. Protein localization was studied using immunohistochemistry in 101 tumors (40 effusions, 25 primary carcinomas, 36 solid metastases). The effect of VICKZ silencing using short hairpin RNA on collagenolytic activity and invasion was assessed in ES-2 OC cells. VICKZ2 was the most frequently expressed family member in serous carcinomas. VICKZ levels measured by pan-VICKZ antibody were significantly higher in primary carcinomas and solid metastases compared to effusions (P < .001). In contrast, VICKZ1 and VICKZ2 were overexpressed in effusions compared to primary carcinomas and solid metastases (P = .016 and P = .024, respectively), and higher VICKZ2 expression in effusions was associated with shorter overall survival in univariate analysis (P = .01). All 3 proteins were localized to OC cells by immunohistochemistry, with tumor-specific expression observed for VICKZ1 and VICKZ2. VICKZ silencing in ES-2 cells led to reduced matrix metalloproteinase 9 activity and reduced invasion. In conclusion, VICKZ2 is the most frequently expressed VICKZ family member in serous OCs. VICKZ1 and VICKZ2 are overexpressed in effusions compared to primary carcinomas and solid metastases, suggesting a biological role at this anatomical site, and appear to have a role in proteolysis and invasion. VICKZ2 may be a prognostic marker in ovarian serous carcinoma effusions.

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.

Identification of characteristic IGF2BP expression patterns in distinct B-ALL entities

Insulin-like growth factor 2 mRNA-binding proteins IGF2BP1, IGF2BP2, and IGF2BP3 have been shown to have diagnostic and prognostic utility in a number of epithelial and soft tissue tumors. Still, little is known about the expression of these molecules in different types of leukemia and our study aims to fill this gap. By using an RT-qPCR approach, we have systemically analyzed the expression of three IGF2BP coding genes in normal hematopoietic tissues and distinct acute lymphoblastic leukemia (ALL) entities. We show that low/negative IGF2BP1 and IGF2BP3 and high IGF2BP2 levels are characteristic to healthy donor bone marrow and peripheral blood whereas different B-ALL entities displayed characteristic perturbations of IGF2BP expression patterns. Namely, we have identified significant associations of overexpressed IGF2BP1 with ETV6/RUNX1-positive (r(2)=0.7891, y=0.8105x-0.4471, p<0.0001), underexpressed IGF2BP2 with E2A/PBX1-positive (p<0.01), and overexpressed IGF2BP2 and IGF2BP3 with MLL/AF4-positive (r(2)=0.6571, y=0.1507x-0.2722, p<0.0001, and r(2)=0.7022, y=0.6482x-0.7660, p<0.0001, respectively) leukemia. Secondly, based on transcript expression dynamics during follow-up, we conclude that overexpression of only IGF2BP1 is inherent characteristic of ETV6/RUNX1-positive leukemic blasts in contrast to IGF2BP3 which remained stably expressed throughout the monitoring period and upon the achievement of molecular remission. Finally, our data suggest that IGF2BP3 might be a marker of disease aggressiveness in BCR/ABL1-positive ALL as consistently increasing levels of this transcript during follow-up predicted eventual leukemia relapse by three months. Altogether, our results highlight the potential utility of IGF2BP profiling in precursor B lymphoid neoplasms as the functions of IGF2BPs in normal and malignant hematopoiesis are further delineated.

Insulin-like growth factor II mRNA binding protein 1 modulates Rev-dependent human immunodeficiency virus type 1 RNA expression

Human immunodeficiency virus type 1 (HIV-1) needs to overcome cellular counter mechanisms such as to successfully propagate itself. Results of our recent studies show that overexpression of insulin-like growth factor II mRNA binding protein 1 (IMP1) inhibits production of infectious HIV-1 particles through adversely affecting virus maturation. Here, we report that IMP1 interacts with HIV-1 Rev protein and its ectopic expression causes relocation of Rev from the nucleus to the cytoplasm. In accordance with this observation, ectopic expression of IMP1 severely diminishes Rev-dependent expression of CAT enzyme and disturbs HIV-1 RNA expression by causing accumulation of the multiple spliced viral RNA. Results of mutagenesis analysis further reveal that the KH4 domain represents the key element of IMP1 in modulating HIV-1 RNA expression. Taken together, these data suggest, in addition to hampering virus assembly, that IMP1 also has an effect on Rev-dependent viral RNA expression.

A role for VICKZ proteins in the progression of colorectal carcinomas: regulating lamellipodia formation

VICKZ proteins are a highly conserved family of RNA binding proteins, implicated in RNA regulatory processes such as intracellular RNA localization, RNA stability, and translational control. During embryogenesis, VICKZ proteins are required for neural crest migration and in adults, the proteins are overexpressed primarily in different cancers. We hypothesized that VICKZ proteins may play a role in cancer cell migration. In patients, VICKZ expression varies with tumour type, with over 60% of colon, lung, and ovarian tumours showing strong expression. In colorectal carcinomas (CRCs), expression is detected at early stages, and the frequency and intensity of staining increase with progression of the disease to lymph node metastases, of which 97% express the protein at high levels. Indeed, in stage II CRC, the level of VICKZ expression in the primary lesion correlates with the degree of lymph node metastasis. In culture, VICKZ proteins rapidly accumulate in processes at the leading edge of PMA-stimulated SW480 CRC cells, where they co-localize with beta-actin mRNA. Two distinct cocktails of shRNAs, each targeting all three VICKZ paralogues, cause a dramatic drop in lamellipodia and ruffle formation in stimulated cells. Thus, VICKZ proteins help to facilitate the dynamic cell surface morphology required for cell motility. We propose that these proteins play an important role in CRC metastasis by shuttling requisite RNAs to the lamellipodia of migrating cells.

The Stanford Tissue Microarray Database

The Stanford Tissue Microarray Database (TMAD; http://tma.stanford.edu) is a public resource for disseminating annotated tissue images and associated expression data. Stanford University pathologists, researchers and their collaborators worldwide use TMAD for designing, viewing, scoring and analyzing their tissue microarrays. The use of tissue microarrays allows hundreds of human tissue cores to be simultaneously probed by antibodies to detect protein abundance (Immunohistochemistry; IHC), or by labeled nucleic acids (in situ hybridization; ISH) to detect transcript abundance. TMAD archives multi-wavelength fluorescence and bright-field images of tissue microarrays for scoring and analysis. As of July 2007, TMAD contained 205 161 images archiving 349 distinct probes on 1488 tissue microarray slides. Of these, 31 306 images for 68 probes on 125 slides have been released to the public. To date, 12 publications have been based on these raw public data. TMAD incorporates the NCI Thesaurus ontology for searching tissues in the cancer domain. Image processing researchers can extract images and scores for training and testing classification algorithms. The production server uses the Apache HTTP Server, Oracle Database and Perl application code. Source code is available to interested researchers under a no-cost license.

VICKZ proteins mediate cell migration via their RNA binding activity

The highly conserved, RNA binding VICKZ proteins help regulate RNA localization, stability, and translation in many eukaryotes. These proteins are also required for cell migration in embryos and cultured cells. In adults, many tumors overexpress VICKZ homologs, and it has been hypothesized that the proteins can mediate cell motility and invasion. How these proteins facilitate cell movement and, in particular, whether their ability to bind RNA plays a role in their function remain unclear. Using HPLC and mass spectrometry to identify a region of Xenopus Vg1 RBP (xVICKZ3) that binds the vegetal localization element of Vg1 RNA, we generated a deletion construct that functions in a dominant-negative manner. The construct associates with full-length xVICKZ3 and severely reduces binding to target RNAs. This dominant-negative construct phenocopies the effect of down-regulating xVICKZ3 in Xenopus embryos. A corresponding deletion in the human homolog hVICKZ1 similarly functions in a dominant-negative fashion to reduce the ability of full-length hVICKZ protein to bind RNA. Expression of the dominant-negative construct in human carcinoma cells inhibits cell movement by several criteria. We conclude that the ability of VICKZ proteins to mediate cell migration, in vitro and in vivo, requires their RNA binding activity.