Emergence of heterogeneous nuclear ribonucleoprotein A2/B1 vs loss of E-cadherin: their reciprocal immunoexpression profiles in human pancreatic cancer

RNA-binding protein-regulated fibronectin is essential for EGFR-activated metastasis of head and neck squamous cell carcinoma

There is a higher expression level of epidermal growth factor receptor (EGFR) in up to 90% of advanced head and neck squamous cell carcinoma (HNSCC) tissue than in normal surrounding tissues. However, the role of RNA-binding proteins (RBPs) in EGFR-associated metastasis of HNSCC remains unclear. In this study, we reveal that RBPs, specifically nucleolin (NCL) and heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1), correlated with the mesenchymal phenotype of HNSCC. The depletion of RBPs significantly attenuated EGF-induced HNSCC metastasis. Intriguingly, the EGF-induced EMT markers, such as fibronectin, were regulated by RBPs through the ERK and NF-κB pathway, followed by the enhancement of mRNA stability of fibronectin through the 5' untranslated region (5'-UTR) of the gene. The upregulation of fibronectin triggered the integrin signaling activation to enhance tumor cells' attachment to endothelial cells and increase endothelial permeability. In addition, the concurrence of EGFR and RBPs or EGFR and fibronectin was associated with overall survival and disease-free survival of HNSCC. The in vivo study showed that depletion of NCL, hnRNPA2B1, and fibronectin significantly inhibited EGF-promoted extravasation of tumor cells into lung tissues. The depletion of fibronectin or treatment with integrin inhibitors dramatically attenuated EGF-induced HNSCC metastatic nodules in the lung. Our data suggest that the RBPs/fibronectin axis is essential for EGF-induced tumor-endothelial cell interactions to enhance HNSCC cell metastasis.

Emerging roles of hnRNP A2B1 in cancer and inflammation

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are a group of RNA-binding proteins with important roles in multiple aspects of nucleic acid metabolism, including the packaging of nascent transcripts, alternative splicing, transactivation of gene expression, and regulation of protein translation. As a core component of the hnRNP complex in mammalian cells, heterogeneous nuclear ribonucleoprotein A2B1 (hnRNP A2B1) participates in and coordinates various molecular events. Given its regulatory role in inflammation and cancer progression, hnRNP A2B1 has become a novel player in immune response, inflammation, and cancer development. Concomitant with these new roles, a surprising number of mechanisms deemed to regulate hnRNP A2B1 functions have been identified, including post-translational modifications, changes in subcellular localization, direct interactions with multiple DNAs, RNAs, and proteins or the formation of complexes with them, which have gradually made hnRNP A2B1 a molecular target for multiple drugs. In light of the rising interest in the intersection between cancer and inflammation, this review will focus on recent knowledge of the biological roles of hnRNP A2B1 in cancer, immune response, and inflammation.

Preclinical Evaluation of hnRNPA2B1 Antibody in Human Triple-Negative Breast Cancer MDA-MB-231 Cells via PET Imaging

Triple-negative breast cancer (TNBC) does not express estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Because TNBC lacks the expression of commonly targeted receptors, it is challenging to develop a new imaging agent for this cancer subtype. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are RNA–protein complexes that have been linked to tumor development and progression. Considering the high expression of hnRNPA2B1, an hnRNP subtype, in TNBC MDA-MB-231 cells, this study aimed to develop a novel hnRNPA2B1 antibody-based nuclear imaging agent. The hnRNPA2B1-specific antibody was radiolabeled with ⁶⁴Cu and evaluated in vitro and in vivo. The trans-cyclooctene (TCO) was functionalized on the antibody to obtain hnRNP-PEG₄-TCO and reactive tetrazine (Tz) on the ultrastable bifunctional chelator PCB-TE2A-alkyne to yield PCB-TE2A-Tz for the inverse electron demand Diels–Alder reaction. The ⁶⁴Cu-radiolabeled antibody was administered and imaged at 1–18 h time points for conventional imaging. Alternatively, the unlabeled antibody conjugate was administered, and 48 h later radiolabeled ⁶⁴Cu-PCB-TE2A-Tz was administered to the same mice for the pretargeting strategy and imaged at the same time intervals for direct comparison. The tumor was successfully visualized in both strategies, and comparatively, pretargeting showed superior results. The ⁶⁴Cu-PCB-TE2A-Tz was successfully clicked at the tumor site with hnRNP-PEG₄-TCO and the non-clicked were concurrently eliminated. This led to increase the tumor uptake with extremely high tumor-to-background ratio manifested by positron emission tomography (PET) imaging and biodistribution studies.

Heterogeneous nuclear ribonucleoprotein A/B: an emerging group of cancer biomarkers and therapeutic targets

Heterogeneous nuclear ribonucleoprotein A/B (hnRNPA/B) is one of the core members of the RNA binding protein (RBP) hnRNPs family, including four main subtypes, A0, A1, A2/B1 and A3, which share the similar structure and functions. With the advance in understanding the molecular biology of hnRNPA/B, it has been gradually revealed that hnRNPA/B plays a critical role in almost the entire steps of RNA life cycle and its aberrant expression and mutation have important effects on the occurrence and progression of various cancers. This review focuses on the clinical significance of hnRNPA/B in various cancers and systematically summarizes its biological function and molecular mechanisms.

Pre-Clinical and Clinical Applications of Small Interfering RNAs (siRNA) and Co-Delivery Systems for Pancreatic Cancer Therapy

Pancreatic cancer (PC) is one of the leading causes of death and is the fourth most malignant tumor in men. The epigenetic and genetic alterations appear to be responsible for development of PC. Small interfering RNA (siRNA) is a powerful genetic tool that can bind to its target and reduce expression level of a specific gene. The various critical genes involved in PC progression can be effectively targeted using diverse siRNAs. Moreover, siRNAs can enhance efficacy of chemotherapy and radiotherapy in inhibiting PC progression. However, siRNAs suffer from different off target effects and their degradation by enzymes in serum can diminish their potential in gene silencing. Loading siRNAs on nanoparticles can effectively protect them against degradation and can inhibit off target actions by facilitating targeted delivery. This can lead to enhanced efficacy of siRNAs in PC therapy. Moreover, different kinds of nanoparticles such as polymeric nanoparticles, lipid nanoparticles and metal nanostructures have been applied for optimal delivery of siRNAs that are discussed in this article. This review also reveals that how naked siRNAs and their delivery systems can be exploited in treatment of PC and as siRNAs are currently being applied in clinical trials, significant progress can be made by translating the current findings into the clinical settings.

Prognostic and Clinicopathological Significance of E-Cadherin in Pancreatic Cancer Patients: A Meta-Analysis

Background

Several recent studies have investigated the prognostic and clinicopathological significance of epithelial cadherin (E-cadherin) in pancreatic cancer; however, conclusions from these studies remain inconsistent. Therefore, we performed a meta-analysis to evaluate the effects of E-cadherin expression on the prognosis and clinicopathological characteristics of pancreatic cancer.

Methods

Embase, PubMed, and Web of Science were searched to identify articles associated with E-cadherin and pancreatic cancer. Hazard ratios (HRs) and odds ratios (ORs) with corresponding confidence intervals (CIs) were calculated and summarized. All eligible studies were searched until May 20, 2020. Heterogeneity among studies was assessed using the Chi-square test and I² statistic.

Results

Overall, 25 studies were identified, of which 12 reports with 1,032 cases concerned the prognosis of pancreatic cancer, and 22 involved the risk and clinical characteristics of pancreatic cancer. The overall results revealed that E-cadherin expression was significantly related to overall survival, gender, tumor grade, lymph node metastasis, tumor differentiation, and risk of pancreatic cancer. In the subgroup analysis, no significant heterogeneity or publication bias was observed.

Conclusions

E-cadherin expression is strongly associated with the risk, clinical features, and prognosis of pancreatic cancer, suggesting that E-cadherin may be an effective biomarker for the clinical assessments and predicting prognosis of pancreatic cancer.

β-Asarone Inhibits Invasion and EMT in Human Glioma U251 Cells by Suppressing Splicing Factor HnRNP A2/B1

β-asarone, the main component in the volatile oil of Acori tatarinowii Rhizoma, has been found to possess antitumor activity. However, its effect and mechanisms against tumor invasion and epithelial–mesenchymal transition (EMT) are still unclear. In this study, no or less cytotoxicity was caused by β-asarone within 0–120 μM in human glioma U251 cells for 48 h. β-asarone (30 and 60 μM) inhibited the migration of U251 cells in the wound healing assay, suppressed the invasion of U251 cells in the Boyden chamber invasion assay, and inhibited the adhesion of U251 cells onto the Matrigel. Moreover, β-asarone suppressed EMT with the up-regulation of E-cadherin and the down-regulation of vimentin. HnRNP A2/B1, a well-characterized oncogenic protein, was shown at a high basal level in U251 cells and β-asarone reduced hnRNP A2/B1 expression in a concentration and time-dependent way. Importantly, hnRNP A2/B1 overexpression significantly counteracted the inhibition of β-asarone on the migration, invasion, and adhesion of U251 cells and reversed the modulation of EMT markers by β-asarone. Additionally, β-asarone decreased the MMP-9 and p-STAT3 in U251 cells, which was also reversed by hnRNP A2/B1 overexpression. Together, our results suggest that hnRNP A2/B1 may be a potential molecular target underlying the inhibitory effect of β-asarone on invasion and EMT in glioma cells.

Pseudolaric Acid B Inhibits Proliferation, Invasion and Epithelial-to-Mesenchymal Transition in Human Pancreatic Cancer Cell

PURPOSE

This study was aimed to investigate the effect of pseudolaric acid B (PAB) on proliferation, invasion and epithelial-to-mesenchymal transition (EMT) in pancreatic cancer cells and to explore the possible mechanism.

MATERIALS AND METHODS

The pancreatic cancer cell line SW1990 was cultured and treated with PAB dose- and time-dependent manners. Cell proliferation and invasion ability were measured by MTT assay and Matrigel/Transwell test, respectively. Semi-quantitative real-time polymerase chain reaction and Western blotting were conducted to detect the expression of EMT markers and the key molecules. Finally, nude mice subcutaneous transplantation tumor model was used to confirm the therapy efficacy of PAB.

RESULTS

PAB could inhibit SW1990 cell proliferation and invasion in time- and dose-dependent manners. Vimentin, fibronectin, N-cadherin, Snail, Slug, YAP, TEAD1, and Survivin were down-regulated (p<0.01), while E-cadherin, caspase-9, MST1, and pYAP were up-regulated (p<0.05). Combined PAB and gemcitabine treatment markedly restricted the tumor growth compared with gencitabin or PAB alone groups.

CONCLUSION

PAB could inhibit the proliferation and invasion ability of pancreatic cancer cells through activating Hippo-YAP pathway and inhibiting the process of EMT.

Abnormal levels of heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) in tumour tissue and blood samples from patients diagnosed with lung cancer

Lung cancer is the second most common type of cancer in the world and is the most common cause of cancer-related death in both men and women. Research into causes, prevention and treatment of lung cancer is ongoing and much progress has been made recently in these areas, however survival rates have not significantly improved. Therefore, it is essential to develop biomarkers for early diagnosis of lung cancer, prediction of metastasis and evaluation of treatment efficiency, as well as using these molecules to provide some understanding about tumour biology and translate highly promising findings in basic science research to clinical application. In this investigation, two-dimensional difference gel electrophoresis and mass spectrometry were initially used to analyse conditioned media from a panel of lung cancer and normal bronchial epithelial cell lines. Significant proteins were identified with heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1), pyruvate kinase M2 isoform (PKM2), Hsc-70 interacting protein and lactate dehydrogenase A (LDHA) selected for analysis in serum from healthy individuals and lung cancer patients. hnRNPA2B1, PKM2 and LDHA were found to be statistically significant in all comparisons. Tissue analysis and knockdown of hnRNPA2B1 using siRNA subsequently demonstrated both the overexpression and potential role for this molecule in lung tumorigenesis. The data presented highlights a number of in vitro derived candidate biomarkers subsequently verified in patient samples and also provides some insight into their roles in the complex intracellular mechanisms associated with tumour progression.

The function of the RNA-binding protein hnRNP in cancer metastasis

Heterogeneous ribonucleoproteins (hnRNPs) are involved in a variety of key cellular functions and are most likely involved in different steps of pre-mRNA processing. Over the past decades, the central roles of hnRNPs have been detected, which show that they are involved in RNA splicing, telomere biogenesis, DNA repair, cell signaling, and in transcription and translation. Mounting evidence suggests that they are involved in the regulation of mRNA stability and translation in many cancer types. The hnRNPs have a variety of potential roles in inhibition of apoptosis, angiogenesis, cell invasion, and epithelial-mesenchymal transition (EMT). It is thus suggested that hnRNP might be a novel and promising therapeutic target and a marker for treatment response and prognostic evaluation. The aims of this review are to survey the existing evidence and discuss the diverse functions of hnRNPs in cancer metastasis.

Induction of pancreatic cancer cell apoptosis, invasion, migration, and enhancement of chemotherapy sensitivity of gemcitabine, 5-FU, and oxaliplatin by hnRNP A2/B1 siRNA

We investigated the effects of inhibiting heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) expression on apoptosis, invasion, migration, and the chemotherapy sensitivity of pancreatic cancer cells to gemcitabine, 5-FU, and oxaliplatin chemotherapy using small interfering RNA (siRNA). Chemically synthesized siRNA hnRNP A2/B1 was transfected into the human pancreatic cancer cell lines SW1990 and BxPC-3. The IC(50) of gemcitabine, 5-FU, and oxaliplatin was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell apoptosis and cycle were detected using flow cytometry. The expressions of apoptosis-related genes, p53, Bax, Bcl-2, TRAIL, Survivin, multidrug resistance 1 (MDR1), E-cadherin, and matrix metalloproteinases-2 (MMP-2) were detected using real-time PCR and western blot. Plate colony formation assay, wound scratch assay, invasion, and migration were also examined. Gemcitabine, 5-FU, and oxaliplatin inhibit the proliferation of SW1990 and BxPC-3 cells in a concentration-dependent manner. Inhibition of hnRNP A2/B1 expression significantly reduced the IC(50) of gemcitabine, 5-FU, and oxaliplatin (P<0.01). hnRNP A2/B1 siRNA combined with gemcitabine, 5-FU and oxaliplatin significantly increased (P<0.01) apoptosis of pancreatic cancer cell lines SW1990 and BxPC-3, increased the expression level of Bax mRNA, decreased Bcl-2 mRNA and MDR1 mRNA expression (P<0.01), and induced no change in p53, TRAIL, and Survivin mRNA expression in SW1990. In the western blot analysis, the expression level of Bax protein increased (P<0.01); the expression of both P-glycoprotein (Pg-p) protein and Bcl-2 protein decreased (P<0.01). Silencing hnRNP A2/B1 decreased invasion and migration in the cell line SW1990. Silencing hnRNP A2/B1 in SW1990 also correlated with an increase in E-cadherin expression and a decrease in MMP-2 expression at the same time. Inhibition of hnRNP A2/B1 expression can induce apoptosis in pancreatic cancer cells and improve chemosensitivity to gemcitabine, 5-FU, and oxaliplatin. hnRNP A2/B1 may play a role in invasion and migration in the pancreatic cancer cell line SW1990 through the regulation of E-cadherin and expression of MMP-2.