Cyclooxygenase-2 is an independent prognostic factor in gastric cancer and its expression is regulated by the messenger RNA stability factor HuR

Human antigen R: Exploring its inflammatory response impact and significance in cardiometabolic disorders

RNA-binding proteins (RBPs) play a crucial role in the regulation of posttranscriptional RNA networks, which can undergo dysregulation in many pathological conditions. Human antigen R (HuR) is a highly researched RBP that plays a crucial role as a posttranscriptional regulator. HuR plays a crucial role in the amplification of inflammatory signals by stabilizing the messenger RNA of diverse inflammatory mediators and key molecular players. The noteworthy correlations between HuR and its target molecules, coupled with the remarkable impacts reported on the pathogenesis and advancement of multiple diseases, position HuR as a promising candidate for therapeutic intervention in diverse inflammatory conditions. This review article examines the significance of HuR as a member of the RBP family, its regulatory mechanisms, and its implications in the pathophysiology of inflammation and cardiometabolic illnesses. Our objective is to illuminate potential directions for future research and drug development by conducting a comprehensive analysis of the existing body of research on HuR.

Inflammation as a driver of hematological malignancies

Hematopoiesis is a tightly regulated process that produces all adult blood cells and immune cells from multipotent hematopoietic stem cells (HSCs). HSCs usually remain quiescent, and in the presence of external stimuli like infection or inflammation, they undergo division and differentiation as a compensatory mechanism. Normal hematopoiesis is impacted by systemic inflammation, which causes HSCs to transition from quiescence to emergency myelopoiesis. At the molecular level, inflammatory cytokine signaling molecules such as tumor necrosis factor (TNF), interferons, interleukins, and toll-like receptors can all cause HSCs to multiply directly. These cytokines actively encourage HSC activation, proliferation, and differentiation during inflammation, which results in the generation and activation of immune cells required to combat acute injury. The bone marrow niche provides numerous soluble and stromal cell signals, which are essential for maintaining normal homeostasis and output of the bone marrow cells. Inflammatory signals also impact this bone marrow microenvironment called the HSC niche to regulate the inflammatory-induced hematopoiesis. Continuous pro-inflammatory cytokine and chemokine activation can have detrimental effects on the hematopoietic system, which can lead to cancer development, HSC depletion, and bone marrow failure. Reactive oxygen species (ROS), which damage DNA and ultimately lead to the transformation of HSCs into cancerous cells, are produced due to chronic inflammation. The biological elements of the HSC niche produce pro-inflammatory cytokines that cause clonal growth and the development of leukemic stem cells (LSCs) in hematological malignancies. The processes underlying how inflammation affects hematological malignancies are still not fully understood. In this review, we emphasize the effects of inflammation on normal hematopoiesis, the part it plays in the development and progression of hematological malignancies, and potential therapeutic applications for targeting these pathways for therapy in hematological malignancies.

Deletion of the mRNA stability factor ELAVL1 (HuR) in pancreatic cancer cells disrupts the tumor microenvironment integrity

Stromal cells promote extensive fibrosis in pancreatic ductal adenocarcinoma (PDAC), which is associated with poor prognosis and therapeutic resistance. We report here for the first time that loss of the RNA-binding protein human antigen R (HuR, ELAVL1) in PDAC cells leads to reprogramming of the tumor microenvironment. In multiple in vivo models, CRISPR deletion of ELAVL1 in PDAC cells resulted in a decrease of collagen deposition, accompanied by a decrease of stromal markers (i.e. podoplanin, α-smooth muscle actin, desmin). RNA-sequencing data showed that HuR plays a role in cell-cell communication. Accordingly, cytokine arrays identified that HuR regulates the secretion of signaling molecules involved in stromal activation and extracellular matrix organization [i.e. platelet-derived growth factor AA (PDGFAA) and pentraxin 3]. Ribonucleoprotein immunoprecipitation analysis and transcription inhibition studies validated PDGFA mRNA as a novel HuR target. These data suggest that tumor-intrinsic HuR supports extrinsic activation of the stroma to produce collagen and desmoplasia through regulating signaling molecules (e.g. PDGFAA). HuR-deficient PDAC in vivo tumors with an altered tumor microenvironment are more sensitive to the standard of care gemcitabine, as compared to HuR-proficient tumors. Taken together, we identified a novel role of tumor-intrinsic HuR in its ability to modify the surrounding tumor microenvironment and regulate PDGFAA.

Exosomal circSPIRE1 mediates glycosylation of E-cadherin to suppress metastasis of renal cell carcinoma

Metastasis is the main cause of mortality in renal cell carcinoma (RCC). Circular RNAs (circRNAs) involvement in RCC metastasis has been described, although the underlying mechanisms remain unknown. We evaluated recurring lung-metastasis cases using patient-derived xenograft models and isolated a highly metastatic clone. CircSPIRE1 was identified as a metastasis-inhibiting circRNA in clinical cohort and xenograft models. Mechanistically, circSPIRE1 suppressed mesenchymal state through regulating ELAV like RNA binding protein 1-mRNA binding, and upregulating polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) and KH domain RNA binding protein (QKI) expression. GALNT3 promoted glycosylation and cytomembrane localization of E-cadherin. QKI formed a positive feedback loop to enhance circSPIRE1 expression. Meanwhile, exosomal circSPIRE1 suppressed angiogenesis and vessel permeability. Our work reveals a non-canonical route for circRNAs in RCC to suppress metastasis. Furthermore, a nanomedicine consisting of circSPIRE1 plasmid suppressed metastasis formation. In conclusion, circSPIRE1 may be a predictor of metastasis and a potential therapeutic target of metastatic RCC.

MYB sustains hypoxic survival of pancreatic cancer cells by facilitating metabolic reprogramming

Extensive desmoplasia and poor vasculature renders pancreatic tumors severely hypoxic, contributing to their aggressiveness and therapy resistance. Here, we identify the HuR/MYB/HIF1α axis as a critical regulator of the metabolic plasticity and hypoxic survival of pancreatic cancer cells. HuR undergoes nuclear-to-cytoplasmic translocation under hypoxia and stabilizes MYB transcripts, while MYB transcriptionally upregulates HIF1α. Upon MYB silencing, pancreatic cancer cells fail to survive and adapt metabolically under hypoxia, despite forced overexpression of HIF1α. MYB induces the transcription of several HIF1α-regulated glycolytic genes by directly binding to their promoters, thus enhancing the recruitment of HIF1α to hypoxia-responsive elements through its interaction with p300-dependent histone acetylation. MYB-depleted pancreatic cancer cells exhibit a dramatic reduction in tumorigenic ability, glucose-uptake and metabolism in orthotopic mouse model, even after HIF1α restoration. Together, our findings reveal an essential role of MYB in metabolic reprogramming that supports pancreatic cancer cell survival under hypoxia.

Cyclooxygenase-2-Prostaglandin E2 pathway: A key player in tumor-associated immune cells

Cyclooxygenases-2 (COX-2) and Prostaglandin E2 (PGE2), which are important in chronic inflammatory diseases, can increase tumor incidence and promote tumor growth and metastasis. PGE2 binds to various prostaglandin E receptors to activate specific downstream signaling pathways such as PKA pathway, β-catenin pathway, NF-κB pathway and PI3K/AKT pathway, all of which play important roles in biological and pathological behavior. Nonsteroidal anti-inflammatory drugs (NSAIDs), which play as COX-2 inhibitors, and EP antagonists are important in anti-tumor immune evasion. The COX-2-PGE2 pathway promotes tumor immune evasion by regulating myeloid-derived suppressor cells, lymphocytes (CD8⁺ T cells, CD4⁺ T cells and natural killer cells), and antigen presenting cells (macrophages and dendritic cells). Based on conventional treatment, the addition of COX-2 inhibitors or EP antagonists may enhance immunotherapy response in anti-tumor immune escape. However, there are still a lot of challenges in cancer immunotherapy. In this review, we focus on how the COX-2-PGE2 pathway affects tumor-associated immune cells.

HuR-dependent SOD2 protein synthesis is an early adaptation to anchorage-independence

During metastasis cancer cells must adapt to survive loss of anchorage and evade anoikis. An important pro-survival adaptation is the ability of metastatic tumor cells to increase their antioxidant capacity and restore cellular redox balance. Although much is known about the transcriptional regulation of antioxidant enzymes in response to stress, how cells acutely adapt to alter antioxidant enzyme levels is less well understood. Using ovarian cancer cells as a model, we demonstrate that an increase in mitochondrial superoxide dismutase SOD2 protein expression is a very early event initiated in response to detachment, an important step during metastasis that has been associated with increased oxidative stress. SOD2 protein synthesis is rapidly induced within 0.5-2 h of matrix detachment, and polyribosome profiling demonstrates an increase in the number of ribosomes bound to SOD2 mRNA, indicating an increase in SOD2 mRNA translation in response to anchorage-independence. Mechanistically, we find that anchorage-independence induces cytosolic accumulation of the RNA binding protein HuR/ELAVL1 and promotes HuR binding to SOD2 mRNA. Using HuR siRNA-mediated knockdown, we show that the presence of HuR is necessary for the increase in SOD2 mRNA association with the heavy polyribosome fraction and consequent nascent SOD2 protein synthesis in anchorage-independence. Cellular detachment also activates the stress-response mitogen-activated kinase p38, which is necessary for HuR-SOD2 mRNA interactions and induction of SOD2 protein output. These findings illustrate a novel translational regulatory mechanism of SOD2 by which ovarian cancer cells rapidly increase their mitochondrial antioxidant capacity as an acute stress response to anchorage-independence.

Long noncoding RNA TNFRSF10A-AS1 promotes colorectal cancer through upregulation of HuR

BACKGROUND

Recent studies have emphasized the emerging importance of long noncoding RNAs (lncRNAs) in colorectal cancer (CRC). However, the functions and regulatory mechanisms of numerous lncRNAs in CRC have not been fully elucidated.

AIM

To explore the functional role and underlying molecular mechanisms of lncRNA TNFRSF10A-AS1 in CRC.

METHODS

TNFRSF10A-AS1 expression was measured by quantitative real-time polymerase chain reaction in CRC, and the relationship between TNFRSF10A-AS1 levels and the clinicopathological features of CRC patients was analyzed. The effect of TNFRSF10A-AS1 expression on CRC proliferation and metastasis was examined in vitro and in vivo. Mechanistically, we investigated how TNFRSF10A-AS1 is involved in CRC as a competitive endogenous RNA.

RESULTS

TNFRSF10A-AS1 was expressed at a high level in CRC and the upregulation of TNFRSF10A-AS1 was associated with advanced T grade and tumor size in CRC patients. A functional investigation revealed that TNFRSF10A-AS1 enhanced the proliferation, migration ability and invasion ability of colon cancer cells in vitro and in vivo. A mechanistic analysis demonstrated that TNFRSF10A-AS1 acted as a miR-3121-3p molecular sponge to regulate HuR expression, ultimately promoting colorectal tumorigenesis and progression.

CONCLUSION

TNFRSF10A-AS1 exerts a tumor-promoting function through the miR-3121-3p/HuR axis in CRC, indicating that it may be a novel target for CRC therapy.

Hu Antigen R (HuR) Protein Structure, Function and Regulation in Hepatobiliary Tumors

Simple Summary

Hepatobiliary tumors are a group of primary malignancies encompassing the liver, the intra- and extra-hepatic biliary tracts, and the gall bladder. Within the liver, hepatocellular carcinoma (HCC) is the most common type of primary cancer, which is, also, representing the third-most recurrent cause of cancer-associated death and the sixth-most prevalent type of tumor worldwide, nowadays. Although less frequent, cholangiocarcinoma (CCA) is, currently, a fatal cancer with limited therapeutic options. Here, we review the regulatory role of Hu antigen R (HuR), a ubiquitous member of the ELAV/Hu family of RNA-binding proteins (RBPs), in the pathogenesis, progression, and treatment of HCC and CCA. Overall, HuR is proposed as a valuable diagnostic and prognostic marker, as well as a therapeutic target in hepatobiliary cancers. Therefore, novel therapeutic approaches that can selectively modulate HuR function appear to be highly attractive for the clinical management of these types of tumors.

Abstract

Hu antigen R (HuR) is a 36-kDa ubiquitous member of the ELAV/Hu family of RNA-binding proteins (RBPs), which plays an important role as a post-transcriptional regulator of specific RNAs under physiological and pathological conditions, including cancer. Herein, we review HuR protein structure, function, and its regulation, as well as its implications in the pathogenesis, progression, and treatment of hepatobiliary cancers. In particular, we focus on hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), tumors where the increased cytoplasmic localization of HuR and activity are proposed, as valuable diagnostic and prognostic markers. An overview of the main regulatory axes involving HuR, which are associated with cell proliferation, invasion, metastasis, apoptosis, and autophagy in HCC, is provided. These include the transcriptional, post-transcriptional, and post-translational modulators of HuR function, in addition to HuR target transcripts. Finally, whereas studies addressing the relevance of targeting HuR in CCA are limited, in the past few years, HuR has emerged as a potential therapeutic target in HCC. In fact, the therapeutic efficacy of some pharmacological inhibitors of HuR has been evaluated, in early experimental models of HCC. We, further, discuss the major findings and future perspectives of therapeutic approaches that specifically block HuR interactions, either with post-translational modifiers or cognate transcripts in hepatobiliary cancers.

LncRNA MALAT1 promotes gastric cancer progression via inhibiting autophagic flux and inducing fibroblast activation

Autophagy defection contributes to inflammation dysregulation, which plays an important role in gastric cancer (GC) progression. Various studies have demonstrated that long noncoding RNA could function as novel regulators of autophagy. Previously, long noncoding RNA MALAT1 was reported upregulated in GC cells and could positively regulate autophagy in various cancers. Here, we for the first time found that MALAT1 could promote interleukin-6 (IL-6) secretion in GC cells by blocking autophagic flux. Moreover, IL-6 induced by MALAT1 could activate normal to cancer-associated fibroblast conversion. The interaction between GC cells and cancer-associated fibroblasts in the tumour microenvironment could facilitate cancer progression. Mechanistically, MALAT1 overexpression destabilized the PTEN mRNA in GC cells by competitively interacting with the RNA-binding protein ELAVL1 to activate the AKT/mTOR pathway for impairing autophagic flux. As a consequence of autophagy inhibition, SQSTM1 accumulation promotes NF-κB translocation to elevate IL-6 expression. Overall, these results demonstrated that intercellular interaction between GC cells and fibroblasts was mediated by autophagy inhibition caused by increased MALAT1 that promotes GC progression, providing novel prevention and therapeutic strategies for GC.

HuR up-regulates cell surface PD-L1 via stabilizing CMTM6 transcript in cancer

Despite the well-established role of CMTM6 in the stabilization of cell surface PD-L1 in cancer cells, the mechanisms underlying CMTM6 expression and regulation are still largely unknown. Here we unexpectedly find a strikingly positive correlation between CMTM6 and Hu-Antigen R (HuR) expression in most types of cancer. Mechanistically, we elucidate HuR stabilizes CMTM6 mRNA via direct association with AU-rich elements (AREs) in its 3′UTR and predominantly up-regulates CMTM6, which is readily abolished by HuR-specific inhibitor, MS-444. Phenotypically, we notice abundant cell surface PD-L1 in HuR-high cancer cells, which significantly inhibits immune activation of co-cultured T cells as indicated by IL-2 production. Treatment with MS-444 completely relieves immune suppression imposed by HuR-overexpression and further stimulates immune responses. Ectopic HuR accelerates allograft tumor progression in vivo, which is greatly compromised by simultaneous administration with MS-444. Our study uncovers a novel mechanism in control of CMTM6 and therefore PD-L1 expression, and suggests the potential of combining HuR inhibitor with PD-1/PD-L1 antibodies for cancer immunotherapy.

The Therapeutic Potential of Regulatory T Cells: Challenges and Opportunities

Regulatory T cells (Tregs) are an immunosuppressive subgroup of CD4+ T cells which are identified by the expression of forkhead box protein P3 (Foxp3). The modulation capacity of these immune cells holds an important role in both transplantation and the development of autoimmune diseases. These cells are the main mediators of self-tolerance and are essential for avoiding excessive immune reactions. Tregs play a key role in the induction of peripheral tolerance that can prevent autoimmunity, by protecting self-reactive lymphocytes from the immune reaction. In contrast to autoimmune responses, tumor cells exploit Tregs in order to prevent immune cell recognition and anti-tumor immune response during the carcinogenesis process. Recently, numerous studies have focused on unraveling the biological functions and principles of Tregs and their primary suppressive mechanisms. Due to the promising and outstanding results, Tregs have been widely investigated as an alternative tool in preventing graft rejection and treating autoimmune diseases. On the other hand, targeting Tregs for the purpose of improving cancer immunotherapy is being intensively evaluated as a desirable and effective method. The purpose of this review is to point out the characteristic function and therapeutic potential of Tregs in regulatory immune mechanisms in transplantation tolerance, autoimmune diseases, cancer therapy, and also to discuss that how the manipulation of these mechanisms may increase the therapeutic options.

circ_0044516 functions in the progression of gastric cancer by modulating MicroRNA-149-5p/HuR axis

Circular RNAs (circRNAs) have emerged as a multifunctional class of RNAs, while there is limited knowledge on their functions in the development of cancers. Herein, we performed the current study to probe into the regulatory mechanism of circ_0044516 in malignant behaviors of gastric cancer (GC) cells with the involvement of microRNA (miR)-149-5p/human antigen R (HuR) axis. Firstly, the expression levels of circ_0044516 in GC cell lines and normal gastric mucosal epithelial cells were determined by qRT-PCR, and GC cell lines with the highest expression of circ_0044516 were screened for further cell experiments. Subsequently, the biological functions of silenced circ_0044516 in GC were identified by CCK-8, colony formation, and transwell assays. Xenograft mouse models were established for in vivo verification. Furthermore, luciferase reporter, RIP, RNA pull-down assay and rescue experiments were performed to explore the sponge regulatory mechanism of circ_0044516. circ_0044516 was suggested to be highly expressed in GC cell lines, and circ_0044516 could promote GC cell proliferation, migration and invasion, as well as in vivo tumor growth. In addition, silenced circ-0044516 reversed the promotive roles in cell viability caused by overexpressed HuR. Furthermore, circ_0044516 mainly localized in the cytoplasm, which may act as a miR-149-5p sponge to modulate HuR expression, thereby playing an essential role in GC development. This study suggests that circ_0044516 may promote HuR expression through sponging miR-149-5p, thereby playing a part in GC progression.

Molecular Targeting of HuR Oncoprotein Suppresses MITF and Induces Apoptosis in Melanoma Cells

Simple Summary

The human antigen R (HuR) protein regulates the expression of hundreds of proteins in a cell that support tumor growth, drug resistance, and metastases. HuR is overexpressed in several human cancers, including melanoma, and is a molecular target for cancer therapy. Our study objective, therefore, was to develop HuR-targeted therapy for melanoma. We identified that HuR regulates the microphthalmia-associated transcription factor (MITF) that has been implicated in both intrinsic and acquired drug resistance in melanoma and is a putative therapeutic target in melanoma. Using a gene therapeutic approach, we demonstrated silencing of HuR reduced MITF protein expression and inhibited the growth of melanoma cells but not normal melanocytes. However, combining HuR-targeted therapy with a small molecule MEK inhibitor suppressed MITF and produced a synergistic antitumor activity against melanoma cells. Our study results demonstrate that HuR is a promising target for melanoma treatment and offers new combinatorial treatment strategies for overriding MITF-mediated drug resistance.

Abstract

Background: Treatment of metastatic melanoma possesses challenges due to drug resistance and metastases. Recent advances in targeted therapy and immunotherapy have shown clinical benefits in melanoma patients with increased survival. However, a subset of patients who initially respond to targeted therapy relapse and succumb to the disease. Therefore, efforts to identify new therapeutic targets are underway. Due to its role in stabilizing several oncoproteins’ mRNA, the human antigen R (HuR) has been shown as a promising molecular target for cancer therapy. However, little is known about its potential role in melanoma treatment. Methods: In this study, we tested the impact of siRNA-mediated gene silencing of HuR in human melanoma (MeWo, A375) and normal melanocyte cells in vitro. Cells were treated with HuR siRNA encapsulated in a lipid nanoparticle (NP) either alone or in combination with MEK inhibitor (U0126) and subjected to cell viability, cell-cycle, apoptosis, Western blotting, and cell migration and invasion assays. Cells that were untreated or treated with control siRNA-NP (C-NP) were included as controls. Results: HuR-NP treatment significantly reduced the expression of HuR and HuR-regulated oncoproteins, induced G1 cell cycle arrest, activated apoptosis signaling cascade, and mitigated melanoma cells’ aggressiveness while sparing normal melanocytes. Furthermore, we demonstrated that HuR-NP treatment significantly reduced the expression of the microphthalmia-associated transcription factor (MITF) in both MeWo and MITF-overexpressing MeWo cells (p < 0.05). Finally, combining HuR-NP with U0126 resulted in synergistic antitumor activity against MeWo cells (p < 0.01). Conclusion: HuR-NP exhibited antitumor activity in melanoma cells independent of their oncogenic B-RAF mutational status. Additionally, combinatorial therapy incorporating MEK inhibitor holds promise in overriding MITF-mediated drug resistance in melanoma.

Proteogenomic examination of esophageal squamous cell carcinoma (ESCC): new lines of inquiry

Introduction: Esophageal squamous cell carcinoma (ESCC), a histopathologic subtype of esophageal cancer is a major cause of cancer-related morbidity and mortality worldwide. This is primarily because patients are diagnosed at an advanced stage by the time symptoms appear. The genomics and mass spectrometry-based proteomics continue to provide important leads toward biomarker discovery for ESCC. However, such leads are yet to be translated into clinical utilities. Areas covered: We gathered information pertaining to proteomics and proteogenomics efforts in ESCC from the literature search until 2020. An overview of omics approaches to discover the candidate biomarkers for ESCC were highlighted. We present a summary of recent investigations of alterations in the level of gene and protein expression observed in biological samples including body fluids, tissue/biopsy and in vitro-based models. Expert opinion: A large number of protein-based biomarkers and therapeutic targets are being used in cancer therapy. Several candidates are being developed as diagnostics and prognostics for the management of cancers. High-resolution proteomic and proteogenomic approaches offer an efficient way to identify additional candidate biomarkers for diagnosis, monitoring of disease progression, prediction of response to chemo and radiotherapy. Some of these biomarkers can also be developed as therapeutic targets.

The RNA-Binding Protein HuR in Digestive System Tumors

Human antigen R (HuR) is a member of the Hu family of RNA-binding proteins. This molecule, which was first described in tumors nearly two decades ago, has recently received much attention in tumor-related research because it regulates the expression of many tumor-associated molecules through posttranscriptional regulatory mechanisms, thereby affecting biological characteristics. It is suggested that HuR might be a novel therapeutic target and a marker for therapeutic response and prognostic assessment. Increasing evidence supports that HuR also plays critical roles in the development, therapy, and prognosis of digestive system tumors. Herein, we review the relationships between HuR and digestive system tumors, demonstrating the importance of HuR in digestive system tumor diagnosis.

MicroRNA-145 suppresses gastric cancer progression by targeting Hu-antigen R

Hu-antigen R (HuR) is involved in the carcinogenesis and progression of multiple types of cancer. However, its precise role in gastric cancer (GC) and the relevant molecular mechanism remain largely unclear. In the present study, we found that HuR expression level was higher in GC tissues and cell lines than in adjacent normal tissues and normal gastric epithelial cell lines, and this elevated expression was found to have a significant association with lymph node metastasis. Moreover, silencing HuR with RNA interference inhibited cell viability and induced cell apoptosis through the apoptosis-related regulators (Bcl-2 and Bax) in GC cells. In addition, bioinformatic analysis revealed that HuR expression was inversely correlated with miR-145 expression in GC tissue samples, and HuR was identified as a direct target of miR-145 with the dual-luciferase reporter. Enforced expression of miR-145 inhibited the HuR expression at both mRNA and protein levels and induced similar biologic effects of silencing HuR in GC cells. Additionally, we also found that restoration of HuR could eliminate the effects induced by miR-145 in GC cells. Taken together, these findings demonstrate the exact role of the miR-145-HuR axis in the progression of GC and indicate a potential target for GC therapy.

Circ-HuR suppresses HuR expression and gastric cancer progression by inhibiting CNBP transactivation

BACKGROUND

Circular RNAs (circRNAs), a subclass of non-coding RNAs, play essential roles in tumorigenesis and aggressiveness. Our previous study has identified that circAGO2 drives gastric cancer progression through activating human antigen R (HuR), a protein stabilizing AU-rich element-containing mRNAs. However, the functions and underlying mechanisms of circRNAs derived from HuR in gastric cancer progression remain elusive.

METHODS

CircRNAs derived from HuR were detected by real-time quantitative RT-PCR and validated by Sanger sequencing. Biotin-labeled RNA pull-down, mass spectrometry, RNA immunoprecipitation, RNA electrophoretic mobility shift, and in vitro binding assays were applied to identify proteins interacting with circRNA. Gene expression regulation was observed by chromatin immunoprecipitation, dual-luciferase assay, real-time quantitative RT-PCR, and western blot assays. Gain- and loss-of-function studies were performed to observe the impacts of circRNA and its protein partner on the growth, invasion, and metastasis of gastric cancer cells in vitro and in vivo.

RESULTS

Circ-HuR (hsa_circ_0049027) was predominantly detected in the nucleus, and was down-regulated in gastric cancer tissues and cell lines. Ectopic expression of circ-HuR suppressed the growth, invasion, and metastasis of gastric cancer cells in vitro and in vivo. Mechanistically, circ-HuR interacted with CCHC-type zinc finger nucleic acid binding protein (CNBP), and subsequently restrained its binding to HuR promoter, resulting in down-regulation of HuR and repression of tumor progression.

CONCLUSIONS

Circ-HuR serves as a tumor suppressor to inhibit CNBP-facilitated HuR expression and gastric cancer progression, indicating a potential therapeutic target for gastric cancer.

Diverse roles of RNA-binding proteins in cancer traits and their implications in gastrointestinal cancers

Gene expression patterns in cancer cells are strongly influenced by posttranscriptional mechanisms. RNA-binding proteins (RBPs) play key roles in posttranscriptional gene regulation; they can interact with target mRNAs in a sequence- and structure-dependent manner, and determine cellular behavior by manipulating the processing of these mRNAs. Numerous RBPs are aberrantly deregulated in many human cancers and hence, affect the functioning of mRNAs that encode proteins, implicated in carcinogenesis. Here, we summarize the key roles of RBPs in posttranscriptional gene regulation, describe RBPs disrupted in cancer, and lastly focus on RBPs that are responsible for implementing cancer traits in the digestive tract. These evidences may reveal a potential link between changes in expression/function of RBPs and malignant transformation, and a framework for new insights and potential therapeutic applications. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

MicroRNA‑125 inhibits RKO colorectal cancer cell growth by targeting VEGF

Colorectal cancer (CRC) is one of the major types of cancer and causes of mortality worldwide, and it remains the third most common cause of cancer‑associated mortality worldwide. MicroRNAs (miRNAs) are a class of small RNAs, which have been shown to be associated with CRC. In the present study, an MTT assay and proliferating cell nuclear antigen (PCNA) protein examination assay were performed to detect RKO cell viability. Hoechst staining, and caspase‑3 activity and BrdU incorporation assays were performed to detect RKO cell apoptosis, respectively. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses were used to analyze the expression of cyclooxygenase‑2 (COX‑2). Western blot analysis was also used to analyze the expression of vascular endothelial growth factor (VEGF) and mitogen‑activated protein kinase (MAPK) signal molecules, including extracellular signal‑regulated kinase (ERK), p38 and c‑Jun N‑terminal kinase (JNK). The target genes of miR-125 were predicted using a double luciferase reporter gene assay. The results of the MTT assay showed that RKO cell viability was decreased by an miRNA-125 mimic and increased by the miRNA-125 inhibitor. The RKO cell viability was significantly correlated with the expression of PCNA. The migration of RKO cells was significantly downregulated in the miR-125 mimics‑transfected cells and upregulated in the miRNA-125 inhibitor‑transfected cells. The results of Hoechst staining and the caspase‑3 activity and BrdU incorporation assays showed that RKO cell apoptosis was increased following miRNA-125 mimic transfection and decreased following miRNA-125 inhibitor transfection. The results of the RT‑qPCR and western blot analysis showed that the expression of COX‑2 was increased in the miR-125 mimic‑transfected cells and decreased in the miR-125 inhibitor‑transfected cells. Using an online miRNA target prediction database, the double luciferase reporter gene assay showed that miR‑125 targeted and inhibited the expression of VEGF through target sites located in the 3' untranslated region of VEGF mRNA. In conclusion, the abnormal expression of miR‑125 was found to be closely associated with CRC. Therefore, miR‑125 may be a novel therapeutic target for CRC.

Clinical Significance and Biological Role of HuR in Head and Neck Carcinomas

Background

Hu-antigen R (HuR) is a posttranscriptional regulator of several target mRNAs, implicated in carcinogenesis. This review aims to present the current evidence regarding the biological role and potential clinical significance of HuR in head and neck carcinomas.

Methods

The existing literature concerning HuR expression and function in head and neck carcinomas is critically presented and summarised.

Results

HuR is expressed in the majority of the examined samples, showing higher cytoplasmic levels in malignant or premalignant cases. Moreover, HuR modulates several genes implicated in biological processes important for malignant transformation, growth, and invasiveness. HuR seems to be an adverse prognosticator in patients with OSCCs, whereas a correlation with a more aggressive phenotype is reported in several types of carcinomas.

Conclusions

A consistent role of HuR in the carcinogenesis and progression of head and neck carcinomas is suggested; nevertheless, further studies are warranted to expand the present information.

Comprehensive evaluation of clinical efficacy and safety of celecoxib combined with chemotherapy in management of gastric cancer

BACKGROUND

To evaluate the clinical efficacy and safety of celecoxib combined with chemotherapy in the treatment of gastric cancer.

METHODS

In total, 240 gastric cancer patients undergoing radical gastrectomy followed by adjuvant chemotherapy were randomly assigned into 2 groups. In the experimental group (n = 120), patients were administered with celecoxib-based chemotherapy, and chemotherapy alone was performed in the control group. Disease-free survival (DFS) and progression-free survival (PFS) were considered as the primary efficacy parameters, and objective response rate (ORR), overall survival (OS), quality of life (QOL), and safety as the secondary efficacy parameters.

RESULTS

The 3-year OS did not significantly differ between the experimental (72%) and control groups (68%, P = .67). The 3-year DFS in the experimental group was 64%, which did not significantly differ from 51% in the control group (P = .41). In patients with positive cyclooxygenase-2 (COX-2) from the experimental group, the 3-year OS was 78%, significantly higher compared with 66% in the control group (P = .02), and the 3-year DFS was 70%, considerably >50% in the control group (P = .01). No statistical significance was identified in the incidence of nausea, neutropenia, anorexia, peripheral neurotoxicity, diarrhea, vomiting, asthenia, and thrombocytopenia, etc. The EORTC quality of life questionnaire (QLQ)-C30 questionnaire revealed that the global QOL in the experimental group was significantly higher than that in the control group (P < .05). No statistical significance was noted in the scores of functioning scale between 2 groups, whereas the scores of the symptom scale, especially pain and fatigue in the experimental group were remarkably higher than that in the control group (P < .05). The global score of EORTC QLQ-STO22 in the experimental group was considerably higher compared with that in the control group (P < .05). No statistical significance was identified in term of the domains of restrictions on feeding, dysphagia, anxiety, reflux, sense of taste, dry mouth, hair loss, and body shape between groups (all P > .05).

CONCLUSION

Celecoxib combined with chemotherapy yields clinical benefits for gastric cancer patients with positive COX-2, which not only enhances the OS, DFS, PFS, QOL, and short-term clinical efficacy, but also does not increase the risk of adverse events.

HuR-targeted small molecule inhibitor exhibits cytotoxicity towards human lung cancer cells

Human antigen (Hu) R is an RNA-binding protein whose overexpression in human cancer correlates with aggressive disease, drug resistance, and poor prognosis. HuR inhibition has profound anticancer activity. Pharmacologic inhibitors can overcome the limitations of genetic inhibition. In this study, we examined the antitumor activity of CMLD-2, a small-molecule inhibitor directed against HuR, using non-small cell lung cancer (NSCLC) as a model. CMLD-2 efficacy was tested in vitro using H1299, A549, HCC827, and H1975 NSCLC cells and MRC-9 and CCD-16 normal human fibroblasts. Treatment of NSCLC cells with CMLD-2 produced dose-dependent cytotoxicity, caused a G1 phase cell-cycle arrest and induced apoptosis. CMLD-2 decreased HuR mRNA and the mRNAs of HuR-regulated proteins (Bcl2 and p27) in tumor cells. Additionally, reduction in the expression of HuR, Bcl2, cyclin E, and Bcl-XL with increased expression of Bax and p27 in CMLD-2-treated NSCLC cells were observed. CMLD-2-treated normal cells, HuR-regulated mRNAs and proteins albeit showed some reduction were less compared to tumor cells. Finally, CMLD-2 treatment resulted in greater mitochondrial perturbation, activation of caspase-9 and -3 and cleavage of PARP in tumor cells compared to normal cells. Our proof-of concept study results demonstrate CMLD-2 represents a promising HuR-targeted therapeutic class that with further development could lead to advanced preclinical studied and ultimately for lung cancer treatment.

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.

HuR Small-Molecule Inhibitor Elicits Differential Effects in Adenomatosis Polyposis and Colorectal Carcinogenesis

HuR is an RNA-binding protein implicated in immune homeostasis and various cancers, including colorectal cancer. HuR binding to AU-rich elements within the 3' untranslated region of mRNAs encoding oncogenes, growth factors, and various cytokines leads message stability and translation. In this study, we evaluated HuR as a small-molecule target for preventing colorectal cancer in high-risk groups such as those with familial adenomatosis polyposis (FAP) or inflammatory bowel disease (IBD). In human specimens, levels of cytoplasmic HuR were increased in colonic epithelial cells from patients with IBD, IBD-cancer, FAP-adenoma, and colorectal cancer, but not in patients with IBD-dysplasia. Intraperitoneal injection of the HuR small-molecule inhibitor MS-444 in AOM/DSS mice, a model of IBD and inflammatory colon cancer, augmented DSS-induced weight loss and increased tumor multiplicity, size, and invasiveness. MS-444 treatment also abrogated tumor cell apoptosis and depleted tumor-associated eosinophils, accompanied by a decrease in IL18 and eotaxin-1. In contrast, HuR inhibition in APCMin mice, a model of FAP and colon cancer, diminished the number of small intestinal tumors generated. In this setting, fecal microbiota, evaluated by 16S rRNA gene amplicon sequencing, shifted to a state of reduced bacterial diversity, with an increased representation of Prevotella, Akkermansia, and Lachnospiraceae Taken together, our results indicate that HuR activation is an early event in FAP-adenoma but is not present in IBD-dysplasia. Furthermore, our results offer a preclinical proof of concept for HuR inhibition as an effective means of FAP chemoprevention, with caution advised in the setting of IBD. Cancer Res; 77(9); 2424-38. ©2017 AACR.

Downregulation of HuR Inhibits the Progression of Esophageal Cancer through Interleukin-18

Purpose

The purpose of this study was to investigate the effect of human antigen R (HuR) downregulation and the potential target genes of HuR on the progression of esophageal squamous cell carcinoma (ESCC).

Materials and Methods

In this study, a proteomics assay was used to detect the expression of proteins after HuR downregulation, and a luciferase assay was used to detect the potential presence of a HuR binding site on the 3’-untranslated region (3'-UTR) of interleukin 18 (IL-18). In addition, colony formation assay, MTT, EdU incorporation assay, Western blot, flow cytometry, immunohistochemistry, transwell invasion assay, and wound healing assay were used.

Results

In the present study, we found that the expression of both HuR protein and mRNA levels were higher in tumor tissues than in the adjacent tissues. HuR downregulation significantly suppressed cell proliferation. In addition, the metastasis of esophageal cancer cells was inhibited, while the expression of E-cadherin was increased and the expression of matrix metalloproteinase (MMP) 2, MMP9, and vimentin was decreased after HuR knockdown. Moreover, silencing of HuR disturbed the cell cycle of ESCC cells mainly by inducing G1 arrest. Furthermore, proteomics analysis showed that downregulation of HuR in TE-1 cells resulted in 100 upregulated and 122 downregulated proteins, including IL-18 as a significantly upregulated protein. The expression of IL-18 was inversely regulated by HuR. IL-18 expression was decreased in ESCC tissues, and exogenous IL-18 significantly inhibited the proliferation and metastasis of ESCC cells. The 3'-UTR of IL-18 harbored a HuR binding site, as shown by an in vitro luciferase assay.

Conclusion

HuR plays an important role in the progression of esophageal carcinoma by targeting IL-18, which may be a potential therapeutic target for the treatment of ESCC.

Targeting the mRNA-binding protein HuR impairs malignant characteristics of pancreatic ductal adenocarcinoma cells

Post-transcriptional regulation is a powerful mediator of gene expression, and can rapidly alter the expression of numerous transcripts involved in tumorigenesis. We have previously shown that the mRNA-binding protein HuR (ELAVL1) is elevated in human pancreatic ductal adenocarcinoma (PDA) specimens compared to normal pancreatic tissues, and its cytoplasmic localization is associated with increased tumor stage. To gain a better insight into HuR’s role in PDA biology and to assess it as a candidate therapeutic target, we altered HuR expression in PDA cell lines and characterized the resulting phenotype in preclinical models. HuR silencing by short hairpin and small interfering RNAs significantly decreased cell proliferation and anchorage-independent growth, as well as impaired migration and invasion. In comparison, HuR overexpression increased migration and invasion, but had no significant effects on cell proliferation and anchorage-independent growth. Importantly, two distinct targeted approaches to HuR silencing showed marked impairment in tumor growth in mouse xenografts. NanoString nCounter^® analyses demonstrated that HuR regulates core biological processes, highlighting that HuR inhibition likely thwarts PDA viability through post-transcriptional regulation of diverse signaling pathways (e.g. cell cycle, apoptosis, DNA repair). Taken together, our study suggests that targeted inhibition of HuR may be a novel, promising approach to the treatment of PDA.

Mouse models for gastric cancer: Matching models to biological questions

Gastric cancer is the third leading cause of cancer-related mortality worldwide. This is in part due to the asymptomatic nature of the disease, which often results in late-stage diagnosis, at which point there are limited treatment options. Even when treated successfully, gastric cancer patients have a high risk of tumor recurrence and acquired drug resistance. It is vital to gain a better understanding of the molecular mechanisms underlying gastric cancer pathogenesis to facilitate the design of new-targeted therapies that may improve patient survival. A number of chemically and genetically engineered mouse models of gastric cancer have provided significant insight into the contribution of genetic and environmental factors to disease onset and progression. This review outlines the strengths and limitations of current mouse models of gastric cancer and their relevance to the pre-clinical development of new therapeutics.

Molecular alterations in gastric cancer with special reference to the early-onset subtype

Currently, gastric cancer (GC) is one of the most frequently diagnosed neoplasms, with a global burden of 723000 deaths in 2012. It is the third leading cause of cancer-related death worldwide. There are numerous possible factors that stimulate the pro-carcinogenic activity of important genes. These factors include genetic susceptibility expressed in a single-nucleotide polymorphism, various acquired mutations (chromosomal instability, microsatellite instability, somatic gene mutations, epigenetic alterations) and environmental circumstances (e.g., Helicobcter pylori infection, EBV infection, diet, and smoking). Most of the aforementioned pathways overlap, and authors agree that a clear-cut pathway for GC may not exist. Thus, the categorization of carcinogenic events is complicated. Lately, it has been claimed that research on early-onset gastric carcinoma (EOGC) and hereditary GC may contribute towards unravelling some part of the mystery of the GC molecular pattern because young patients are less exposed to environmental carcinogens and because carcinogenesis in this setting may be more dependent on genetic factors. The comparison of various aspects that differ and coexist in EOGCs and conventional GCs might enable scientists to: distinguish which features in the pathway of gastric carcinogenesis are modifiable, discover specific GC markers and identify a specific target. This review provides a summary of the data published thus far concerning the molecular characteristics of GC and highlights the outstanding features of EOGC.

Correlation of 15-prostagladin dehydrogenase expression with clinicopathological factors and survival rate in gastric adenocarcinoma

INTRODUCTION

The prostaglandin (PG) E2 level, which is associated with oncogenesis, progression and metastasis in various types of cancer, is determined by reciprocal regulation of 15-prostaglandin dehydrogenase (15-PGDH) and cyclooxygenase-2. This study investigated 15-PGDH expression in gastric adenocarcinoma, the associations between 15-PGDH expression and clinicopathological factors, and the correlation between 15-PGDH expression and the 5-year gastric-cancer-specific survival rate (5-year GCSS).

METHODS

From 175 patients who underwent gastrectomy, we obtained biopsies of gastric adenocarcinoma tissues and adjacent normal tissues for preparation as formalin-fixed, paraffin-embedded specimens and conducted an immunohistochemical analysis.

RESULTS

15-PGDH expression was low in 65.1% of cases. 15-PGDH expression showed no relationship with age or gender, but was significantly correlated with the pathologic type, T stage, N stage, TNM stage, positive lymph node metastasis, metastasis to a larger quantity of lymph nodes, positive lymphatic invasion, positive vascular invasion, positive perineural invasion, and palliative gastrectomy. The 5-year GCSS of the low-expression group was 77.19% and a lower level of 15-PGDH expression correlated to a lower 5-year GCSS. 15-PGDH expression significantly influenced the 5-year GCSS on univariate but not multivariate analysis.

CONCLUSION

Our findings indicate that 15-PGDH expression was low in gastric adenocarcinoma and was correlated with the clinicopathological factors associated with prognosis and a more advanced stage of gastric adenocarcinoma. Also, 15-PGDH expression was significantly associated with the 5-year GCSS, but was not an independent prognostic factor thereof.

Progress on the relationship between miR-125 family and tumorigenesis

miRNA-125 family, which is a highly conserved miRNA family throughout evolution, is consist of miRNA-125a-3p, miRNA-125a-5p, miRNA-125b-1 and miRNA-125b-2.The aberrant expression of miR-125 familyis tightly related to tumorigenesis and tumor development. The downstream targets of miRNA-125 include transcription factors like STAT3, cytokines like IL-6 and TGF-β, tumor suppressing protein p53, pro-apoptotic protein Bak1 and RNA binding protein HuR et al. Through regulating these downstream targets miR-125 family is involved in regulating tumorigenesis and tumor development. Nowadays, miR-125b have already became a putative and valuable biomarker for cancer diagnosis, treatment and prognosis. In this review, we mainly summarize the dual function of miRNA-125 family in suppression and promotion of cancer cells and further elaborate its regulatory mechanisms from four facets, proliferation, apoptosis, invasion or metastasis and immune response.

Prognostic effect of hENT1, dCK and HuR expression by morphological type in periampullary adenocarcinoma, including pancreatic cancer

BACKGROUND

Putative biomarkers of gemcitabine response have been extensively studied in pancreatic cancer, but less so in other types of periampullary adenocarcinoma. The most studied biomarker is human equilibrative nucleoside transporter 1 (hENT1), and the activating enzyme deoxycytidine kinase (dCK) has also been linked to treatment response. The RNA-binding protein human antigen R (HuR) has been demonstrated to confer increased dCK levels in vitro and to predict gemcitabine response in vivo. Here, we investigated the prognostic impact of hENT1, dCK and HuR in pancreatobiliary (PB) and intestinal (I) type periampullary cancers, respectively.

MATERIAL AND METHODS

Immunohistochemical expression of hENT1, dCK and HuR was evaluated in tissue microarrays with all primary tumours and 103 paired lymph node metastases from a consecutive retrospective cohort of 175 patients with resected periampullary adenocarcinomas.

RESULTS

In patients with PB-type tumours, neither hENT1 nor dCK expression was prognostic. A high HuR cytoplasmic/nuclear ratio was associated with a significantly reduced five-year overall survival (OS) in patients receiving adjuvant gemcitabine (HR 2.07, 95% CI 1.03-4.17) but not in untreated patients (pinteraction = 0.028). In patients with I-type tumours receiving adjuvant chemotherapy, high dCK expression was significantly associated with a prolonged recurrence-free survival (RFS) (HR 0.09, 95% CI 0.01-0.73, pinteraction = 0.023). Furthermore, HuR expression was associated with a prolonged OS and RFS in unadjusted but not in adjusted analysis and hENT1 expression was an independent predictor of a prolonged RFS (HR 0.24, 95% CI 0.10-0.59), regardless of adjuvant treatment.

CONCLUSION

hENT1 expression is a favourable prognostic factor in I-type, but not in PB-type tumours. High dCK expression is a favourable prognostic factor in patients with I-type tumours receiving adjuvant treatment and a high cytoplasmic/nuclear HuR ratio is a negative prognostic factor in gemcitabine-treated PB-type tumours. Morphological subtype should always be considered in biomarker studies on periampullary cancer.

Cytoplasmic c-ros oncogene 1 receptor tyrosine kinase expression may be associated with the development of human oral squamous cell carcinoma

The c-ros oncogene 1 receptor tyrosine kinase (ROS1) gene encodes a proto-oncogenic protein that has been demonstrated to be involved in the pathogenesis of several types of cancer. The present study aimed to analyze the expression of ROS1 in human oral squamous cell carcinomas (OSCCs), and investigate the association between its expression and the clinicopathological parameters of patients with OSCC. Paraffin-embedded OSCC tissues from 31 patients were obtained and the expression of ROS1 was analyzed by immunohistochemistry. The cellular location of ROS1 was determined by immunofluorescence in human oral cancer CAL-27 cells. The association of clinicopathological characteristics and survival rates with ROS1 expression were assessed. The results revealed that ROS1 was exclusively localized in the cytoplasm of the OSCC tissues (24/30, 80.0%), and in the cytoplasm of adjacent dysplastic epithelial tissues (2/15, 13.3%) (P<0.001). The moderate to strong expression of ROS1 in the cytoplasm was higher in OSCC tissues than in the normal epithelial tissues adjacent to the tumor (67.7 vs. 0%, P=0.001). The results of the Kaplan-Meier analysis and multivariate Cox regression analysis indicated that there was no association between the 5-year survival rate of patients and the cytoplasmic (P=0.28 and P=0.60, respectively) or nuclear expression (P=0.90 and P=0.31, respectively) of ROS1. These results suggest that the cytoplasmic expression level of ROS1 may be associated with the development of OSCC.

Artesunate inhibits the growth and induces apoptosis of human gastric cancer cells by downregulating COX-2

Artesunate, a derivative of artemisinin isolated from Artemisia annua L., has been traditionally used to treat malaria, and artesunate has demonstrated cytotoxic effects against a variety of cancer cells. However, there is little available information about the antitumor effects of artesunate on human gastric cancer cells. In the present study, we investigated the antitumor effect of artesunate on human gastric cancer cells and whether its antitumor effect is associated with reduction in COX-2 expression. The effects of artesunate on the growth and apoptosis of gastric cancer cells were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometric analysis of annexin V-fluorescein isothiocyanate/propidium iodide staining, rhodamine 123 staining, and Western blot analysis. Results indicate that artesunate exhibits antiproliferative effects and apoptosis-inducing activities. Artesunate markedly inhibited gastric cancer cell proliferation in a time- and dose-dependent manner and induced apoptosis in gastric cancer cells a dose-dependent manner, which was associated with a reduction in COX-2 expression. Treatment with the selective COX-2 inhibitor celecoxib, or transient transfection of gastric cancer cells with COX-2 siRNA, also inhibited cell proliferation and induced apoptosis. Furthermore, the treatment with artesunate promoted the expression of proapoptotic factor Bax and suppressed the expression of antiapoptotic factor Bcl-2. In addition, caspase-3 and caspase-9 were activated, and artesunate induced loss of mitochondrial membrane potential, suggesting that the apoptosis is mediated by mitochondrial pathways. These results demonstrate that artesunate has an effect on anti-gastric cancer cells. One of the antitumor mechanisms of artesunate may be that its inhibition of COX-2 led to reduced proliferation and induction of apoptosis, connected with mitochondrial dysfunction. Artesunate might be a potential therapeutic agent for gastric cancer.

Immune profiling and cancer post transplantation

Half of all long-term (> 10 year) australian kidney transplant recipients (KTR) will develop squamous cell carcinoma (SCC) or solid organ cancer (SOC), making cancer the leading cause of death with a functioning graft. At least 30% of KTR with a history of SCC or SOC will develop a subsequent SCC or SOC lesion. Pharmacological immunosuppression is a major contributor of the increased risk of cancer for KTR, with the cancer lesions themselves further adding to systemic immunosuppression and could explain, in part, these phenomena. Immune profiling includes; measuring immunosuppressive drug levels and pharmacokinetics, enumerating leucocytes and leucocyte subsets as well as testing leucocyte function in either an antigen specific or non-specific manner. Outputs can vary from assay to assay according to methods used. In this review we define the rationale behind post-transplant immune monitoring assays and focus on assays that associate and/or have the ability to predict cancer and rejection in the KTR. We find that immune monitoring can identify those KTR of developing multiple SCC lesions and provide evidence they may benefit from pharmacological immunosuppressive drug dose reductions. In these KTR risk of rejection needs to be assessed to determine if reduction of immunosuppression will not harm the graft.

COX-2 Inhibitors and Gastric Cancer

The evidence that cyclooxygenase-2 (COX-2) is upregulated and plays an important role in carcinogenesis of gastric cancer has triggered the topic of COX-2 inhibitors as chemopreventive agents for gastric cancer. Studies find that COX-2 inhibitors are associated not only with chemoprophylactic effects, but also with chemotherapeutic potentials in gastric cancer. Both COX-dependent and COX-independent pathways have a role in the anticancer efficiency of COX-2 inhibitors. However, enthusiasm is thwarted by the potential toxicity, that is, gastrointestinal toxicity of nonselective COX-2 inhibitors and cardiovascular risk of selective COX-2 inhibitors. Therefore, more studies are needed to develop new targeted antitumor agents (such as prostaglandin E receptor antagonist) and to define fundamental questions such as optimal treatment regimens, integration of cotherapy, and careful selection of candidates.

Clinical significance of HuR expression in human malignancy

Hu-antigen R (HuR) is an RNA-binding protein that regulates the stability, translation, and nucleus-to-cytoplasm translocation of target mRNAs. The aim of the present review was to summarize and present the currently available information in the English literature on HuR expression in various human tumors, verifying its possible clinical significance. HuR function is directly linked to its subcellular localization. In normal cells, HuR is mostly localized in the nucleus, while in malignant cells, an increase in cytoplasmic HuR levels has been noted, in both cell lines and tissue samples. Moreover, in malignancy, elevated HuR expression levels and cytoplasmic immunohistochemical pattern have been correlated with advanced clinicopathological parameters and altered expression levels of proteins implicated in neoplasia. Additionally, elevated HuR expression levels and mainly cytoplasmic immunohistochemical pattern were correlated with decreased patients' survival rate in various human tumors. HuR is a putative drug target for cancer therapy, since it is expressed ubiquitously in malignant clinical samples and has an apparently consistent role in tumor formation and progression.

Krüppel -like factor 8 is a stress-responsive transcription factor that regulates expression of HuR

BACKGROUND/AIMS

HuR is an RNA-binding protein that regulates the post-transcriptional life of thousands of cellular mRNAs and promotes cell survival. HuR is expressed as two mRNA transcripts that are differentially regulated by cell stress. The goal of this study is to define factors that promote transcription of the longer alternate form.

METHODS

Effects of transcription factors on HuR expression were determined by inhibition or overexpression of these factors followed by competitive RT-PCR, gel mobility shift, and chromatin immunoprecipitation. Transcription factor expression patterns were identified through competitive RT-PCR and Western analysis. Stress responses were assayed in thapsigargin-treated proximal tubule cells and in ischemic rat kidney.

RESULTS

A previously described NF-κB site and a newly identified Sp/KLF factor binding site were shown to be important for transcription of the long HuR mRNA. KLF8, but not Sp1, was shown to bind this site and increase HuR mRNA levels. Cellular stress in cultured or native proximal tubule cells resulted in a rapid decrease of KLF8 levels that paralleled those of the long HuR mRNA variant.

CONCLUSIONS

These results demonstrate that KLF8 can participate in regulating expression of alternate forms of HuR mRNA along with NF-κB and other factors, depending on cellular contexts.

miR-137 effects on gastric carcinogenesis are mediated by targeting Cox-2-activated PI3K/AKT signaling pathway

The discovery of microRNAs (miRNAs) provided a new avenue for early diagnosis and treatment of GC. MiR-137 has been reported to be under-expressed and involved in various cell processes. However, the role of miR-137 in GC is less known. In this study, we show that miR-137 is under-expressed in GC and functions as a tumor suppressor through targeting Cyclooxygenase-2 (Cox-2), which subsequently suppresses the activation of PI3K/AKT signaling pathway both in vitro and in vivo. Moreover, restored Cox-2 expression partially abolished the tumor suppressive effects of miR-137 in GC cells, suggesting miR-137 may suppress GC carcinogenesis by targeting Cox-2.

Cyclooxygenase-2 expression is associated with poor overall survival of patients with gastric cancer: a meta-analysis

BACKGROUND

Cyclooxygenase-2 (COX-2) is believed to be involved in gastric carcinogenesis. However, it is still controversial whether COX-2 expression can be regarded as a prognostic factor for gastric cancer patients.

AIM

To obtain a more accurate relationship between COX-2 overexpression and prognosis in gastric cancer by meta-analysis.

METHOD

Relevant articles published up to May 2013 were searched by use of several keywords in electronic databases. Separate hazard ratio (HR) estimates and 95 % confidence intervals (95 % CI) for COX-2 overexpression and overall survival (OS) and disease-free survival (DFS) with gastric cancer were extracted. Combined HR with 95 % CI was calculated by use of Stata11.0 software to estimate the size of the effect. Publication bias testing and sensitivity analysis were also performed.

RESULTS

A total of 27 studies which included 3,891 gastric cancer patients were combined in the final analysis. Combined results suggested that COX-2 overexpression was associated with an unfavorable OS (HR 1.58, 95 % CI 1.36-1.84) but not DFS (HR 1.15, 95 % CI 0.93-1.43) among patients with gastric cancer. Publication bias was absent. Sensitivity analysis suggested that the results of this meta-analysis were robust.

CONCLUSIONS

The results of this meta-analysis suggest that high COX-2 expression may be an independent risk factor for poor OS of patients with gastric cancer. More large prospective studies are now needed to further clarify the prognostic value of COX-2 expression for DFS in gastric cancer.

Apurinic/apyrimidinic endonuclease-1 is associated with angiogenesis and VEGF production via upregulation of COX-2 expression in esophageal cancer tissues

Apurinic/apyrimidinic endonuclease-1 (APE-1) is a key enzyme responsible for DNA base excision repair and is also a multifunctional protein such as redox effector for several transcriptional factors. Our study was designed to investigate APE-1 expression and to study its interaction with cyclooxygenase (COX)-2 expression and VEGF production in the esophageal cancer. The expression of APE-1, COX-2, monocyte chemoattractant protein (MCP)-1, CC-chemokine receptor (CCR)2, and VEGF were evaluated by immunohistochemistry in 65 human esophageal squamous cell carcinoma (ESCC) tissues. Real-time PCR and Western blotting were performed to detect mRNA and protein expression of APE-1 and p-signal transducer and activator of transcription 3 (STAT3) expression in MCP-1-stimulated ESCC cell lines (KYSE 220 and EC-GI-10). siRNA for APE-1 was treated to determine the role of APE-1 in the regulation of COX-2 expression, VEGF production, and antiapoptotic effect against cisplatin. In human ESCC tissues, nuclear localization of APE-1 was observed in 92.3% (60/65) of all tissues. There was a significant relationship (P = 0.029, R = 0.49) between nuclear APE-1 and cytoplasmic COX-2 expression levels in the esophageal cancer tissues. In KYSE 220 and EC-GI-10 cells, MCP-1 stimulation significantly increased mRNA and protein expression of APE-1. Treatment with siRNA for APE-1 significantly inhibited p-STAT3 expression levels in MCP-1-stimulated cells. Furthermore, treatment of siRNA for APE-1 significantly reduced COX-2 expression and VEGF production in MCP-1-stimulated esophageal cancer cell lines. Treatment with APE-1 siRNA significantly increased apoptotic levels in cisplatin-incubated KYSE 220 and EC-GI-10 cells. We concluded that APE-1 is overexpressed and associated with COX-2 expression and VEGF production in esophageal cancer tissues.

MicroRNA-519a demonstrates significant tumour suppressive activity in laryngeal squamous cells by targeting anti-carcinoma HuR gene

Objective:

This study investigated the expression and functional effects, and related molecular mechanisms, of microRNA-519a in laryngeal squamous cell carcinoma.

Methods:

MicroRNA-519a and HuR messenger RNA in laryngeal squamous cell carcinoma were measured using reverse transcription polymerase chain reaction. MicroRNA-519a effects on the growth of human epithelial type 2 cells were tested using an MTT assay. The influence of microRNA-519a on the expression levels of HuR and other related genes in protein was tested by Western blotting. Cell cycle analyses were performed using flow cytometry. Associations between expression levels and patients' clinical parameters were analysed with Pearson correlation analysis.

Results:

Expression of microRNA-519a in laryngeal squamous cell carcinoma tissues was significantly lower than in adjacent non-cancerous tissues. The expression of microRNA-519a was negatively associated with histological differentiation, tumour–node–metastasis stage, lymphatic metastasis and disease-free survival time. After increasing the level of microRNA-519a in laryngeal squamous cell carcinoma human epithelial type 2 cells, cell growth was inhibited and cell cycle was arrested in the G2/M phase. MicroRNA-519a down-regulated HuR gene expression in protein levels without affecting messenger RNA levels.

Conclusion:

MicroRNA-519a may function as a tumour suppressor by inhibiting HuR expression, and may serve as a therapeutic target for laryngeal squamous cell carcinoma.

Role of cyclooxygenase-2 in gastric cancer development and progression

Although the incidence of gastric cancer has been declining in recent decades, it remains a major public health issue as the second leading cause of cancer death worldwide. In China, gastric cancer is still the main cause of death in patients with malignant tumors. Most patients are diagnosed at an advanced stage and mortality is high. Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostanoid synthesis and plays an important role in the development and progression of gastric cancer. The expression of COX-2 in gastric cancer is upregulated and its molecular mechanisms have been investigated. Helicobacter pylori infection, tumor suppressor gene mutation and the activation of nuclear factor-kappa B may be responsible for the elevated expression of COX-2 in gastric cancer. The mechanisms of COX-2 in the development and progression of gastric cancer are probably through promoting the proliferation of gastric cancer cells, while inhibiting apoptosis, assisting angiogenesis and lymphatic metastasis, and participating in cancer invasion and immunosuppression. This review is intended to discuss, comment and summarize recent research progress on the role of COX-2 in gastric cancer development and progression, and elucidate the molecular mechanisms which might be involved in the carcinogenesis.

HuR cytoplasmic expression is associated with increased cyclin A expression and inferior disease-free survival in patients with gastrointestinal stromal tumours (GISTs)

AIMS

HuR is an RNA-binding protein that post-transcriptionally modulates the expression of various target genes involved in carcinogenesis, such as CCNA2, which encodes cyclin A. The aim of this study was to evaluate the significance of HuR expression and subcellular localization in a large cohort of gastrointestinal stromal tumours (GISTs).

METHODS AND RESULTS

HuR immunostaining was assessable for nuclear and cytoplasmic expression in 341 cases on tissue microarrays of primary GISTs, of which 318, 296 and 193 cases were also characterized for Ki67 labelling, cyclin A immunoexpression, and KIT and PDGFRA receptor tyrosine kinase (RTK) genotypes, respectively. The results of HuR nuclear and cytoplasmic expression were correlated with disease-free survival (DFS) and clinicopathological, immunohistochemical and RTK genotypic variables. HuR cytoplasmic expression was present in 42% of primary GISTs, and was significantly related to epithelioid histology, larger tumour size, NIH risk category, and nuclear expression of Ki67 and cyclin A. Importantly, HuR cytoplasmic expression (P < 0.001) and cyclin A overexpression (P < 0.001) were strongly associated with worse DFS. Both variables remained independently predictive of adverse outcome [P = 0.020 and risk ratio (RR) 2.605 for cytoplasmic HuR; P = 0.026 and RR 2.763 for cyclin A].

CONCLUSIONS

HuR cytoplasmic expression not only correlates with adverse prognosticators and cyclin A overexpression, but also independently predicts worse DFS, indicating a causative role in conferring tumour aggressiveness.

Cytoplasmic expression of the ELAV-like protein HuR as a potential prognostic marker in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most frequent cancers and a leading cause of death from cancer in China. The human ELAV-like protein HuR has been found to contribute to cancer development and progression through stabilizing a group of cellular mRNAs of cancer-related genes. In this study, we investigated the expression of HuR in a cohort of ESCC patients using immunohistochemical staining. HuR detected in the cytoplasm of cancer cells was positive in 46.6% of 58 ESCC specimens; 75.9% of these specimens had nuclear immunoreactivity for HuR. Cytoplasmic HuR expression was higher in cancer tissues compared to 20 matched adjacent noncancerous tissues. A clinicopathological study showed that cytoplasmic HuR expression was positively associated with lymph node metastasis, depth of tumor invasion, and advanced stage, whereas nuclear HuR expression was not correlated with any clinicopathological factors. Patients positive for cytoplasmic HuR expression had a cumulative 5-year survival rate of 25.3%, whereas it was 43.8% for patients negative for cytoplasmic HuR expression. In a multivariate analysis, cytoplasmic HuR expression was an independent prognostic factor, whereas nuclear positivity for HuR was not. Our results indicate that high cytoplasmic HuR expression is associated with positive lymph node metastasis, deep tumor invasion, high stage, and poor survival in ESCC. Thus, HuR is the first mRNA stability protein whose expression is associated with poor survival in esophageal cancer.

Multiple functions of the RNA-binding protein HuR in cancer progression, treatment responses and prognosis

The human embryonic lethal abnormal vision-like protein, HuR, is a member of the Hu family of RNA-binding proteins. Over the past decade, this ubiquitously expressed protein has been extensively investigated in cancer research because it is involved in the regulation of mRNA stability and translation in many cell types. HuR activity and function is associated with its subcellular distribution, transcriptional regulation, translational and post-translational modifications. HuR regulation of target mRNAs is based on the interaction between the three specific domains of HuR protein and one or several U- or AU-rich elements (AREs) in the untranslated region of target mRNAs. A number of cancer-related transcripts containing AREs, including mRNAs for proto-oncogenes, cytokines, growth factors, and invasion factors, have been characterized as HuR targets. It has been proposed that HuR has a central tumorigenic activity by enabling multiple cancer phenotypes. In this review, we comprehensively survey the existing evidence with regard to the diverse functions of HuR in caner development and progression. The current data also suggest that HuR might be a novel and promising therapeutic target and a marker for treatment response and prognostic evaluation.

miR-29a inhibition normalizes HuR over-expression and aberrant AU-rich mRNA stability in invasive cancer

The activities of RNA-binding proteins are perturbed in several pathological conditions, including cancer. These proteins include tristetraprolin (TTP, ZFP36) and HuR (ELAVL1), which respectively promote the decay or stability of adenylate-uridylate-rich (AU-rich) mRNAs. Here, we demonstrated that increased stabilization and subsequent over-expression of HuR mRNA were coupled to TTP deficiency. These findings were observed in breast cancer cell lines with an invasive phenotype and were further confirmed in ZFP36-knockout mouse fibroblasts. We show that TTP–HuR imbalance correlated with increased expression of AU-rich element (ARE) mRNAs that code for cancer invasion genes. The microRNA miR-29a was abundant in invasive breast cancer cells when compared to non-tumourigenic cell types. When normal breast cells were treated with miR-29a, HuR mRNA and protein expression were up-regulated. MiR-29a recognized a seed target in the TTP 3′ UTR and a cell-permeable miR-29a inhibitor increased TTP activity towards HuR 3′ UTR. This led to HuR mRNA destabilization and restoration of the aberrant TTP–HuR axis. Subsequently, the cancer invasion factors uPA, MMP-1 and MMP-13, and cell invasiveness, were decreased. The TTP:HuR mRNA ratios were also perturbed in samples from invasive breast cancer patients when compared with normal tissues, and were associated with invasion gene expression. This study demonstrates that an aberrant ARE-mediated pathway in invasive cancer can be normalized by targeting the aberrant and functionally coupled TTP–HuR axis, indicating a potential therapeutic approach. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.