HUR mRNA expression in ovarian high-grade serous carcinoma effusions is associated with poor survival

HuR as a molecular target for cancer therapeutics and immune-related disorders

The control of eukaryotic gene expression occurs at multiple levels, from transcription to messenger RNA processing, transport, localization, turnover, and translation. RNA-binding proteins control gene expression and are involved in different stages of mRNA processing, including splicing, maturation, turnover, and translation. A ubiquitously expressed RBP Human antigen R is engaged in the RNA processes mentioned above but, most importantly, controls mRNA stability and turnover. Dysregulation of HuR is linked to many diseases, including cancer and other immune-related disorders. HuR targets mRNAs containing AU-rich elements at their 3'untranslated region, which encodes proteins involved in cell growth, proliferation, tumor formation, angiogenesis, immune evasion, inflammation, invasion, and metastasis. HuR overexpression has been reported in many tumor types, which led to a poor prognosis for patients. Hence, HuR is considered an appealing drug target for cancer treatment. Therefore, multiple attempts have been made to identify small molecule inhibitors for blocking HuR functions. This article reviews the current prospects of drugs that target HuR in numerous cancer types, their mode of action, and off-target effects. Furthermore, we will summarize drugs that interfered with HuR-RNA interactions and established themselves as novel therapeutics. We will also highlight the significance of HuR overexpression in multiple cancers and discuss its role in immune functions. This review provides evidence of a new era of HuR-targeted small molecules that can be used for cancer therapeutics either as a monotherapy or in combination with other cancer treatment modalities.

Quercetin Impairs HuR-Driven Progression and Migration of Triple Negative Breast Cancer (TNBC) Cells

In the present study, we have explored the prognostic value of HuR gene as well as protein in breast cancers. Furthermore, we have also investigated the HuR therapeutic relevance in TNBCs, which is an aggressive breast cancer subtype. Using an online meta-analysis tool, we found that HuR protein overexpression positively correlates with reduced overall survival of TNBC patients (p = 0.028). Furthermore, we demonstrated that the TNBC breast cancer cell lines i.e., MDA-MB-231 and MDA-MB-468 are good model systems to study HuR protein, as they both exhibit a significant amount of cytoplasmic HuR (active form). Quercetin treatment significantly inhibited the cytoplasmic HuR in both TNBC cell lines. By using specific HuR siRNA, we established that quercetin-mediated inhibition of adhesion and migration of TNBC cells is dependent on HuR. Upon analyzing adhesion proteins i.e., β-catenin and CD44, we found that quercetin mediated effect on TNBC adhesion and migration was through the HuR-β-catenin axis and CD44, independently. Overall, the present results demonstrate that elevated HuR levels are associated with TNBC progression and relapse, and the ability of quercetin to inhibit cytoplasmic HuR protein provides a rationale for using it as an anticancer agent for the treatment of aggressive TNBCs.Supplemental data for this article is available online at at 10.1080/01635581.2021.1952628.

HuR Promotes Ovarian Cancer Cell Proliferation by Regulating TIMM44 mRNA Stability

The human antigen R (HuR) could play an essential role in stabilizing the mRNAs of many tumor-associated genes. Little research is performed to investigate the relevant mechanism mediated by HuR to promote the progress of ovarian cancer. The Cancer Genome Atlas (TCGA) dataset was retrieved to calculate the correlation between HuR and translocase of inner mitochondrial membrane 44 (TIMM44) expression. HuR expression plasmid, TIMM44 expression plasmid, siRNA HuR, and TIMM44 siRNAs were further transfected into A2780 and SKOV3 cells. The 3'UTR of TIMM44 fragment was cloned into the back of Renilla luciferase in the pSicheck2 dual fluorescent reporter to indicate the interaction between HuR and TIMM44. Cell count and MTT assay were performed to assay the proliferation ability of A2780 and SKOV3 cells. High-level HuR expression in 56 ovarian cancer patients recruited in Zibo Central Hospital was positively correlated with metastasis status and poor prognosis revealed by Kaplan-Meier analysis. Both HuR and TIMM44 can promote the proliferation of SKOV3 and A2780 cells. A high correlation of HuR and TIMM44 expression was testified in the TCGA data. Luciferase reporter assay confirmed that HuR could bind to TIMM44 to maintain the mRNA stability. TIMM44 siRNA administration inhibited the proliferation of SKOV3 cells, which could not be rescued. All of these indicate that the main function of HuR on ovarian cancer proliferation is mediated by TIMM44 through mRNA stability regulation, and HuR/TIMM44 complex can be used as a target to inhibit the proliferation of ovarian cancer cells.

The RNA Binding Protein HuR: A Promising Drug Target for Anticancer Therapy

The stability of mRNA is one of the key factors governing the regulation of eukaryotic gene expression and function. Human antigen R (HuR) is an RNA-binding protein that regulates the stability, translation, and nucleus-to-cytoplasm shuttling of its target mRNAs. While HuR is normally localized within the nucleus, it has been shown that HuR binds mRNAs in the nucleus and then escorts the mRNAs to the cytoplasm where HuR protects them from degradation. It contains several RNA recognition motifs, which specifically bind to adenylate and uridylate-rich regions within the 3'-untranslated region of the target mRNA to mediate its effect. Many of the HuR target mRNAs encode proteins important for cell growth, tumorigenesis, angiogenesis, tumor inflammation, invasion and metastasis. HuR overexpression is known to correlate well with high-grade malignancy and poor prognosis in many tumor types. Thus, HuR has emerged as an attractive drug target for cancer therapy. Novel small molecule HuR inhibitors have been identified by high throughput screening and new formulations for targeted delivery of HuR siRNA to tumor cells have been developed with promising anticancer activity. This review summarizes the significant role of HuR in cancer development, progression, and poor treatment response. We will discuss the potential and challenges of targeting HuR therapeutically.

Ovarian cancer stem cells: What progress have we made?

Ovarian cancer (OvCa) is the most lethal gynecological malignancy in the United States primarily due to lack of a reliable early diagnostic, high incidence of chemo-resistant recurrent disease as well as profuse tumor heterogeneity. Cancer stem cells (CSCs) continue to gain attention, as they are known to resist chemotherapy, self-renew and re-populate the bulk tumor with undifferentiated and differentiated cells. Moreover, CSCs appear to readily adapt to environmental, immunologic and pharmacologic cues. The plasticity and ability to inactivate or activate signaling pathways promoting their longevity has been, and continues to be, the challenge faced in developing successful CSC targeted therapies. Identifying and understanding unique ovarian CSC markers and the pathways they utilize could reveal new therapeutic opportunities that may offer alternative adjuvant treatment options. Herein, we will discuss the current state of ovarian CSC characterization, their contribution to disease resistance, recurrence and shed light on clinical trials that may target the CSC population.

Prognostic value of abnormally expressed lncRNAs in ovarian carcinoma: a systematic review and meta-analysis

Ovarian cancer (OC) is the most deadly gynecological cancer and it is urgently needed to find a new marker for the progress of OC. Many long noncoding RNAs (lncRNAs) have been reported to be aberrantly expressed in ovarian carcinoma, and may serve as prognostic markers. Therefore, we conducted this meta-analysis to gain a better understanding of the prognostic value of lncRNAs in patients with varian carcinoma. We systematically searched PubMed, EMBASE, and Web of Science. A total of 13 eligible studies, including 10 on clinicopathological features, 13 on prognosis were identified. Pooled hazard ratios (HRs) or odds ratios (OR) and 95% confidence intervals (95% CIs) were calculated using random- or fixed-effects models. Our results revealed that the increased expressions of 8 lncRNAs were associated with poor prognosis and the decreased expressions of 5 lncRNAs were related to poor prognosis in ovarian carcinoma. High HOTAIR expression was associated with shorter overall survival in ovarian cancer (pooled HR: 2.05, 95% CI: 1.51-2.77, P < 0.001). In conclusion, our meta-analysis suggested that LncRNAs could function as potential prognostic markers for ovarian cancer patients and high expression HOTAIR was associated with shorter overall survival in ovarian cancer.

RNA-based ovarian cancer research from 'a gene to systems biomedicine' perspective

Ovarian cancer remains the leading cause of death from a gynecologic malignancy, and treatment of this disease is harder than any other type of female reproductive cancer. Improvements in the diagnosis and development of novel and effective treatment strategies for complex pathophysiologies, such as ovarian cancer, require a better understanding of disease emergence and mechanisms of progression through systems medicine approaches. RNA-level analyses generate new information that can help in understanding the mechanisms behind disease pathogenesis, to identify new biomarkers and therapeutic targets and in new drug discovery. Whole RNA sequencing and coding and non-coding RNA expression array datasets have shed light on the mechanisms underlying disease progression and have identified mRNAs, miRNAs, and lncRNAs involved in ovarian cancer progression. In addition, the results from these analyses indicate that various signalling pathways and biological processes are associated with ovarian cancer. Here, we present a comprehensive literature review on RNA-based ovarian cancer research and highlight the benefits of integrative approaches within the systems biomedicine concept for future ovarian cancer research. We invite the ovarian cancer and systems biomedicine research fields to join forces to achieve the interdisciplinary caliber and rigor required to find real-life solutions to common, devastating, and complex diseases such as ovarian cancer.

ABBREVIATIONS

CAF: cancer-associated fibroblasts; COG: Cluster of Orthologous Groups; DEA: disease enrichment analysis; EOC: epithelial ovarian carcinoma; ESCC: oesophageal squamous cell carcinoma; GSI: gamma secretase inhibitor; GO: Gene Ontology; GSEA: gene set enrichment analyzes; HAS: Hungarian Academy of Sciences; lncRNAs: long non-coding RNAs; MAPK/ERK: mitogen-activated protein kinase/extracellular signal-regulated kinases; NGS: next-generation sequencing; ncRNAs: non-coding RNAs; OvC: ovarian cancer; PI3K/Akt/mTOR: phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin; RT-PCR: real-time polymerase chain reaction; SNP: single nucleotide polymorphism; TF: transcription factor; TGF-β: transforming growth factor-β.

RNA-Binding Proteins in Female Reproductive Pathologies

RNA-binding proteins are key regulatory molecules involved primarily in post-transcriptional gene regulation of RNAs. Post-transcriptional gene regulation is critical for adequate cellular growth and survival. Recent reports have shown key interactions between these RNA-binding proteins and other regulatory elements, such as miRNAs and long noncoding RNAs, either enhancing or diminishing their response to RNA stabilization. Many RNA-binding proteins have been reported to play a functional role in mediation of cytokines involved in inflammation and immune dysfunction, and some have been classified as global post-transcriptional regulators of inflammation. The ubiquitous expression of RNA-binding proteins in a wide variety of cell types and their unique mechanisms of degradative action provide evidence that they are involved in reproductive tract pathologies. Aberrant inflammation and immune dysfunction are major contributors to the pathogenesis and disease pathophysiology of many reproductive pathologies, including ovarian and endometrial cancers in the female reproductive tract. Herein, we discuss various RNA-binding proteins and their unique contributions to female reproductive pathologies with a focus on those mediated by aberrant inflammation and immune dysfunction.

miR-200c Regulation of Metastases in Ovarian Cancer: Potential Role in Epithelial and Mesenchymal Transition

Among the gynecological malignancies, ovarian cancer is the most fatal due to its high mortality rate. Most of the identified cases are epithelial ovarian cancer (EOC) with five distinct subtypes: high-grade serous carcinoma, low-grade serous carcinoma, mucinous carcinoma, endometrioid carcinoma, and clear-cell carcinoma. Lack of an early diagnostic approach, high incidence of tumor relapse and the heterogenous characteristics between each EOC subtypes contribute to the difficulties in developing precise intervention and therapy for the patients. MicroRNAs (miRNAs) are single-stranded RNAs that have been shown to function as tumor suppressors or oncomiRs. The miR-200 family, especially miR-200c, has been shown to be implicated in the metastasis and invasion of ovarian carcinoma due to its functional regulation of epithelial-to-mesenchymal transition (EMT). This mini review is aimed to summarize the recent findings of the miR-200c functional role as well as its validated targets in the metastasis cascade of ovarian cancer, with a focus on EMT regulation. The potential of this miRNA in early diagnosis and its dual expression status are also discussed.

HuR-regulated lncRNA NEAT1 stability in tumorigenesis and progression of ovarian cancer

Long noncoding RNAs (lncRNAs) have recently emerged as pivotal regulators in governing fundamental biological processes, as well as in tumorigenesis. The nuclear paraspeckle assembly transcript 1 (NEAT1) is one of the most highly regulated lncRNAs in recent genomic datasets, however, its biological role and regulatory mechanism in ovarian cancer (OC) development and progression are poorly defined. In this study, we identified that NEAT1 was up-regulated in OC patients and cell lines, and its expression was associated with the FIGO stage and lymph node metastasis. Furthermore, the ectopic expression of NEAT1_1 in OVCAR-3 cell lines promoted cell proliferation and invasion, whereas knockdown of NEAT1_1 did the opposite. Furthermore, NEAT1_1 was stabilized by an RNA-binding protein HuR, but suppressed by miR-124-3p in OC cells. Accordingly, the increased HuR mRNA and decreased miR-124-3p levels were observed in OC patients. These results suggested that lncRNA NEAT1, whose expression was collaboratively controlled by HuR and miR-124-3p, could regulate ovarian carcinogenesis and may serve as a potential target for antineoplastic therapies.