Loss of Scribble Promotes Snail Translation through Translocation of HuR and Enhances Cancer Drug Resistance

RNA binding proteins in cancer chemotherapeutic drug resistance

Drug resistance has been a major obstacle in the quest for a cancer cure. Many chemotherapeutic treatments fail to overcome chemoresistance, resulting in tumor remission. The exact process that leads to drug resistance in many cancers has not been fully explored or understood. However, the discovery of RNA binding proteins (RBPs) has provided insight into various pathways and post-transcriptional gene modifications involved in drug tolerance. RBPs are evolutionarily conserved proteins, and their abnormal gene expression has been associated with cancer progression. Additionally, RBPs are aberrantly expressed in numerous neoplasms. RBPs have also been implicated in maintaining cancer stemness, epithelial-to-mesenchymal transition, and other processes. In this review, we aim to provide an overview of RBP-mediated mechanisms of drug resistance and their implications in cancer malignancy. We discuss in detail the role of major RBPs and their correlation with noncoding RNAs (ncRNAs) that are associated with the inhibition of chemosensitivity. Understanding and exploring the pathways of RBP-mediated chemoresistance will contribute to the development of improved cancer diagnosis and treatment strategies.

Scribble promotes fibrosis-dependent mechanisms of hepatocarcinogenesis by p53/PUMA-mediated glycolysis

BACKGROUNDS AND AIMS

Liver cancer is the sixth most common type of cancer and the fifth leading cause of cancer mortality worldwide. Scribble has been shown to function as a neoplastic tumor suppressor gene in most tumors. Our previous studies reported that down-regulation or mislocalization of Scribble was sufficient to initiate mammary tumorigenesis and NSCLC. Recently, it was reported that Scribble was highly expressed in hepatocellular carcinoma (HCC). We aim to study how it was up-regulated and the contradictory role of Scribble in HCC.

METHODS AND RESULTS

Using a mouse model of carbon tetrachloride (CCl4)-induced liver fibrosis system, we showed that Scribble was over-expressed and which may protect the mice against hepatic fibrosis. Unexpectedly, we found out the potential for Scribble to act as a tumor driver at the advanced stage of N-nitrosodiethylamine (DEN) plus CCl4 induced HCC mice model in vivo. In addition, we observed even higher expression of Scribble in HCC tumors harboring elevated levels of wild-type p53. Most importantly, nuclear translocated Scribble could interact with p53, which lead to enhanced stability and transcriptional activity of p53. Mechanistically, our data suggested that Scribble might drive HCC progression by promoting metabolic regulation of p53 through p53-upregulated modulator of apoptosis (PUMA)-mediated Warburg effect.

CONCLUSIONS

Our data identified the molecular basis of hepatic fibrosis-specific gene expression of polarity gene, such as Scribble. Interestingly, with the progression from fibrosis to cirrhosis to HCC, its nuclear translocation promoted a wild-type p53-mediated cancer metabolic switch and tumor progression in HCC. Taken together, we demonstrated that Scribble was up-regulated and served a protective role in liver fibrosis, while also apparently acting as a tumor driver in fibrosis-dependent hepatocarcinogenesis.

Relationship between HuR and tumor drug resistance

Human resistance protein R (HuR), also known as embryonic lethal abnormal visual-like protein (ELAVL1), is an RNA-binding protein widely expressed in vivo that affects the mRNA stability of targeted and is involved in post-transcriptional regulation. Recent studies have shown that HuR is aberrantly expressed in different human cancers and is an essential factor in poor clinical prognosis. The role of HuR in numerous tumors suggests that it could be a new target for tumor therapy and as a marker for efficacy and prognostic assessment. This review focuses on the relationship between HuR and drug resistance in different tumors and briefly describes the structure, function, and inhibitors of HuR. We summarize the mechanisms by which HuR causes tumor resistance and the molecular targets affected.

The molecular mechanism of Y473 phosphorylation of UGDH relieves the inhibition effect of UDP-glucose on HuR

Uridine diphosphate glucose (UDP-Glc) is able to accelerate the decay of snail family transcriptional repressor 1 (SNAI1) mRNA by inhibiting Hu antigen R (HuR, an RNA-binding protein), thereby preventing cancer invasiveness and drug resistance. Nevertheless, the phosphorylation of tyrosine 473 (Y473) of UDP-glucose dehydrogenase (UGDH is capable of converting UDP-Glc to uridine diphosphate glucuronic acid (UDP-GlcUA)) weakens the inhibition of UDP-Glc to HuR, thus initiating the epithelial-mesenchymal transformation of tumor cells and promoting tumor cell migration and metastasis. To address the mechanism, we performed molecular dynamics simulations combined with molecular mechanics generalized Born surface area (MM/GBSA) analysis on wild-type and Y473 phosphorylated UGDH and HuR, UDP-Glc, UDP-GlcUA complexes. We demonstrated that Y473 phosphorylation was able to enhance the binding between UGDH and the HuR/UDP-Glc complex. Compared with HuR, UGDH has a stronger binding ability with UDP-Glc; therefore, UDP-Glc was inclined to bind to UGDH and then was catalyzed to UDP-GlcUA by UGDH, which relieved the inhibition of UDP-Glc to HuR. In addition, the binding ability of HuR for UDP-GlcUA was lower than its affinity for UDP-Glc, significantly reducing the inhibition of HuR. Hence, HuR bound to SNAI1 mRNA more easily to increase the stability of mRNA. Our results revealed the micromolecular mechanism of Y473 phosphorylation of UGDH regulating the interaction between UGDH and HuR as well as relieving the inhibition of UDP-Glc on HuR, which contributed to understanding the role of UGDH and HuR in tumor metastasis and developing small molecule drugs targeting the interaction between UGDH and HuR.

Silencing of RNA binding protein, ZFP36L1, promotes epithelial-mesenchymal transition in liver cancer cells by regulating transcription factor ZEB2

RNA binding proteins (RBPs) of the zinc finger protein 36 family including zinc finger protein 36 like 1 (ZFP36L1) are implicated in cancer, however, the underlying molecular mechanisms have remained unclear. These proteins function by regulating post-transcriptional gene expression upon binding to the AU-rich elements (ARE's) within the 3'untranslated regions (3'UTRs) of specific mRNAs and increasing their mRNA turnover. Here, we tested the role of ZFP36L1 in hepatocellular carcinoma (HCC) cell lines. ZFP36L1 was under-expressed among the three RBPs in a majority of the HCC cell lines. Silencing of ZFP36L1 in two of the seven HCC cell lines resulted in epithelial-mesenchymal transition (EMT) like morphological changes, which were characterized by the transition of epithelial morphology to elongated mesenchymal morphology and increased migration and invasion potential. Conversely, overexpression of ZFP36L1 abolished these changes. RNA-seq analysis of ZFP36L1-depleted HCC cells revealed a significant upregulation of an EMT-inducing transcription factor, ZEB2 (zinc-finger E-box-binding homeobox 2), and enrichment of pathways associated with mesenchymal cell development and differentiation. ZEB2 mRNA contains AREs within its 3'UTR and its stability was increased following ZFP36L1 knockdown. Conversely, ZEB2 was significantly downregulated following ZFP36L1 overexpression and ZEB2 3'UTR was regulated by ZFP36L1 in luciferase reporter assays. These data identify ZEB2 mRNA as a ZFP36L1 target in HCC cells and demonstrate that ZFP36L1 regulates EMT possibly through direct regulation of ZEB2 mRNA. In summary, our results demonstrate that ZFP36L1 suppresses EMT inliver cancer cells by down-regulating the expression of EMT-inducing transcription factor, ZEB2. These data suggest an important role of ZFP36L1 in the development, progression, and metastasis of hepatocellular cancer.

Study on the prognosis, immune and drug resistance of m6A-related genes in lung cancer

Background

Few studies have demonstrated that the relationship between m6A-related genes and the prognosis, tumor microenvironment and drug resistance of LC.

Methods

The main results were analyzed with bioinformatics methods.

Results

Hence, we found 10 m6A-related genes expressed less in tumor samples in comparison with normal ones. Using consensus clustering, all LC patients were grouped into 2 subgroups according to the overall expression of 10 differential expressed m6A-related genes. In two clusters, the OS and immune characteristics were different. We analyzed the predictive potential of 10 m6A-related genes in the prognosis of LC, and obtained a risk prognosis model on the strength of ZC3H13, CBLL1, ELAVL1 and YTHDF1 as the hub candidate genes through LASSO cox. The expression of 4 hub m6A-related genes was validated by IHC in the HPA database. The infiltration level of dendritic cell, CD4+ T cell and neutrophil that were affected by CNV level of m6A-related genes in LUAD and LUSC patients. Moreover, based on GSCALite database, we found that LUSC patients with hypermethylation tended to have a better overall survival. In terms of drug sensitivity, etoposide correlated negatively with ELAVL1, HNRNPC, RBM15B, YTHDF2 and CBLL1. ZC3H13 had positively association with afatinib, while HNRNPC was positively associated with dasatinib, erlotinib, lapatinib and TGX221. Crizotinib had a negative correlation with ELAVL1, CBLL1, HNRNPC and RBM15B.

Conclusion

In conclusion, m6A-related genes are important participants in LC and the expression levels of ZC3H13, CBLL1, ELAVL1 and YTHDF1 are significant for prediction and treatment of LC. Researches of drug resistance based on m6A-related genes need to pay more attention for producing new therapeutic strategies of LC and CBLL1 may contribute to target treatment for further research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-022-04984-5.

The molecular mechanisms and therapeutic strategies of EMT in tumor progression and metastasis

Epithelial–mesenchymal transition (EMT) is an essential process in normal embryonic development and tissue regeneration. However, aberrant reactivation of EMT is associated with malignant properties of tumor cells during cancer progression and metastasis, including promoted migration and invasiveness, increased tumor stemness, and enhanced resistance to chemotherapy and immunotherapy. EMT is tightly regulated by a complex network which is orchestrated with several intrinsic and extrinsic factors, including multiple transcription factors, post-translational control, epigenetic modifications, and noncoding RNA-mediated regulation. In this review, we described the molecular mechanisms, signaling pathways, and the stages of tumorigenesis involved in the EMT process and discussed the dynamic non-binary process of EMT and its role in tumor metastasis. Finally, we summarized the challenges of chemotherapy and immunotherapy in EMT and proposed strategies for tumor therapy targeting EMT.

The role of human antigen R (HuR) in modulating proliferation, senescence and radiosensitivity of skin cells

The skin is the largest outermost organ of the human body. It is vulnerable to various damages, such as ionizing radiation. Exploration of proliferation, senescence and radiosensitivity of skin cells contributes to the development of medical and cosmetic countermeasures against skin aging and toward injury protection. Human antigen R (HuR) is one of the most widely studied RNA-binding proteins and serves an important role in stabilization of mRNA and regulation of the expression of the target genes. To investigate the role of HuR in modulating proliferation, senescence and radiosensitivity of skin cells, the present study performed an in vitro study using lentivirus-mediated overexpression or silencing of HuR in human keratinocyte HaCaT cells and human skin fibroblast WS1 cells. The results indicated that overexpression of HuR promoted proliferation, whereas downregulation of HuR inhibited proliferation of HaCaT and WS1 cells. Overexpression of HuR reduced apoptosis and senescence in skin cells. RNA-Seq of skin cells with HuR overexpression or knockdown identified 77 mRNAs positively or negatively correlated with HuR expression levels. In addition, silencing of HuR induced a significant increase in radiogenic reactive oxygen species after irradiation. Overexpression of HuR increased radiotolerance of HaCaT and WS1 cells. RNA immunoprecipitation coupled with RNA-Seq identified 14 mRNAs interacting with HuR upon radiation exposure. Overall, the findings of the present study illustrated the key role of HuR in modulating proliferation, senescence and radiosensitivity of skin cells providing a new therapeutic strategy for cosmetic treatments and to combat skin injury.

HuR Affects the Radiosensitivity of Esophageal Cancer by Regulating the EMT-Related Protein Snail

Purpose

We previously found that Hu antigen R (HuR) can regulate the proliferation and metastasis of esophageal cancer cells. This study aims to explore the effects of HuR on the radiosensitivity of esophageal cancer.

Materials and Method

Analyses of CCK-8, colony formation assay, Western blot, immunofluorescence, flow cytometry, reactive oxygen species (ROS), and mitochondrial membrane potential were conducted to characterize the esophageal cancer cells. Nude mouse models were used to detect the effects of HuR in a combination of X-ray treatment on the subcutaneous xenografts of esophageal cancer. In addition, a luciferase assay was used to detect the direct interaction of HuR with Snail mRNA 3’-UTR.

Results

The down-regulation of HuR combined with X-ray can significantly inhibit the proliferation and colony formation of esophageal cancer cells. Flow cytometry data showed that the down-regulation of HuR could induce a G1 phase cell cycle block in esophageal cancer cells, and aggravate X-ray-induced apoptosis, indicated by the increases of apoptosis-related proteins Bax, caspase-3 and caspase-9. Moreover, the down-regulation of HuR could significantly impair the mitochondrial membrane potential and increase the ROS production and DNA double-strand break marker γH2AX expression in esophageal cancer cells that were exposed to X-rays. In vivo data showed that the down-regulation of HuR combined with radiation significantly decreased the growth of subcutaneous xenograft tumors. Furthermore, HuR could interact with Snail. Up-regulation of Snail can reverse the EMT inhibitory effects caused by HuR down-regulation, and attenuate the tumor-inhibiting and radiosensitizing effects caused by HuR down-regulation.

Conclusion

In summary, our data demonstrate that HuR effectively regulates the radiosensitivity of esophageal cancer, which may be achieved by stabilizing Snail. Thus, HuR/Snail axis is a potentially therapeutic target for the treatment of esophageal cancer.

HuR confers IL-17a-induced migration and invasion of gastric cancer cells via upregulation of Snail translation

Human gastric cancer is a leading cause of cancer mortality in the world wide. We found that the expression of IL-17a was significantly increased in gastric cancer cells. Treatment with recombinant IL-17a (rIL-17a) can increase migration, invasion and epithelial to mesenchymal transition (EMT) of gastric cancer cells. Further, Snail, a key factor to regulate EMT, was significantly increased in rIL-17a-treated gastric cancer cells. While knockdown of Snail can abolish IL-17a-induced EMT of gastric cancer cells. Mechanistically, IL-17a can promote the translation efficiency of Snail, while had no effect on its mRNA expression or protein stability. Further, we found that IL-17a can increase the expression of HuR, which markedly promoted translation of Snail mRNA. While knockdown of HuR can reverse rIL-17a-induced expression of Snail and EMT of gastric cancer cells. Collectively, our data suggested that HuR confers IL-17a induced migration and invasion of gastric cancer cells via upregulation of Snail translation.

miR‑224‑5p regulates the proliferation, migration and invasion of pancreatic mucinous cystadenocarcinoma by targeting PTEN

Pancreatic mucinous cystadenocarcinoma (MCC) is a rare malignant tumor, with a limited number of studies. The present study aimed to investigate the function and mechanism of microRNA (miR)-224-5p on proliferation, migration and invasion of MCC of the pancreas. Reverse transcription-quantitative PCR was used to explorethe expression of miR-224-5p and the PTEN gene. MTT, wound healing, Transwell and tumorigenesis assays were conducted to investigate the proliferation, migration and invasion of MCC1 cells in vitro and in vivo. Western blot analysis was employed to test the protein expression of PTEN. The target gene of miR-224-5p was assessed and verified by luciferase assay. miR-224-5p expression was notably higher, while PTEN expression was lower, in MCC1 cells compared with normal tissues and cells. Overexpression of miR-224-5p promoted the proliferation, migration and invasion of MCC and knockdown of miR-224-5p inhibited these functions. Bioinformatics analysis and luciferase assay indicated that PTEN was the direct target gene of miR-224-5p. The negative correlation between miR-224-5p and PTEN was confirmed both in vitro and in vivo. PTEN reversed the effects of miR-224-5p on proliferation, migration and invasion of MCC1 cells. The present study revealed for the first time, to the best of the authors' knowledge, that miR-224-5p was highly expressed and served an oncogenic role in MCC. miR-224-5p not only regulated the proliferation, migration and invasion of pancreatic MCC but may also be a potential therapeutic target for MCC.

A Spectrum of Cell States During the Epithelial-to-Mesenchymal Transition

The epithelial-to-mesenchymal transition (EMT) encompasses a complex cascade of events through which a cell transits to reduce its epithelial characteristics and become migratory. Classically, this transition has been considered complete upon loss of molecular markers characteristic of an "epithelial" state and acquisition of those associated with "mesenchymal" cells. Recently, however, evidence from both developmental and cancer EMT contexts suggest that cells undergoing EMT are often heterogeneous, concomitantly expressing both epithelial and mesenchymal markers to varying degrees; rather, cells frequently display a "partial" EMT phenotype and do not necessarily require full "mesenchymalization" to become migratory. Here, we offer a brief perspective on recent important advances in our fundamental understanding of the spectrum of cellular states that occur during partial EMT in the context of development and cancer metastasis.

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.

Fine-tuning the metabolic rewiring and adaptation of translational machinery during an epithelial-mesenchymal transition in breast cancer cells

ABSTRACT

BACKGROUND

During breast cancer progression, the epithelial to mesenchymal transition has been associated with metastasis and endocrine therapy resistance; however, the underlying mechanisms remain elusive. To gain insight into this process, we studied the transition undergone by MCF7-derived cells, which is driven by the constitutive nuclear expression of a MKL1 variant devoid of the actin-binding domain (MKL1 ΔN200). We characterized the adaptive changes that occur during the MKL1-induced cellular model and focused on regulation of translation machinery and metabolic adaptation.

METHODS

We performed a genome-wide analysis at the transcriptional and translational level using ribosome profiling complemented with RNA-Seq and analyzed the expression of components of the translation machinery and enzymes involved in energy metabolism. NGS data were correlated with metabolomic measurements and quantification of specific mRNAs extracted from polysomes and western blots.

RESULTS

Our results reveal the expression profiles of a luminal to basal-like state in accordance with an epithelial to mesenchymal transition. During the transition, the synthesis of ribosomal proteins and that of many translational factors was upregulated. This overexpression of the translational machinery appears to be regulated at the translational level. Our results indicate an increase of ribosome biogenesis and translation activity. We detected an extensive metabolic rewiring occurring in an already "Warburg-like" context, in which enzyme isoform switches and metabolic shunts indicate a crucial role of HIF-1α along with other master regulatory factors. Furthermore, we detected a decrease in the expression of enzymes involved in ribonucleotide synthesis from the pentose phosphate pathway. During this transition, cells increase in size, downregulate genes associated with proliferation, and strongly upregulate expression of cytoskeletal and extracellular matrix genes.

CONCLUSIONS

Our study reveals multiple regulatory events associated with metabolic and translational machinery adaptation during an epithelial mesenchymal-like transition process. During this major cellular transition, cells achieve a new homeostatic state ensuring their survival. This work shows that ribosome profiling complemented with RNA-Seq is a powerful approach to unveil in-depth global adaptive cellular responses and the interconnection among regulatory circuits, which will be helpful for identification of new therapeutic targets.

HuR Reduces Radiation-Induced DNA Damage by Enhancing Expression of ARID1A

Tumor suppressor ARID1A, a subunit of the chromatin remodeling complex SWI/SNF, regulates cell cycle progression, interacts with the tumor suppressor TP53, and prevents genomic instability. In addition, ARID1A has been shown to foster resistance to cancer therapy. By promoting non-homologous end joining (NHEJ), ARID1A enhances DNA repair. Consequently, ARID1A has been proposed as a promising therapeutic target to sensitize cancer cells to chemotherapy and radiation. Here, we report that ARID1A is regulated by human antigen R (HuR), an RNA-binding protein that is highly expressed in a wide range of cancers and enables resistance to chemotherapy and radiation. Our results indicate that HuR binds ARID1A mRNA, thereby increasing its stability in breast cancer cells. We further find that ARID1A expression suppresses the accumulation of DNA double-strand breaks (DSBs) caused by radiation and can rescue the loss of radioresistance triggered by HuR inhibition, suggesting that ARID1A plays an important role in HuR-driven resistance to radiation. Taken together, our work shows that HuR and ARID1A form an important regulatory axis in radiation resistance that can be targeted to improve radiotherapy in breast cancer patients.

Loss of Scribble confers cisplatin resistance during NSCLC chemotherapy via Nox2/ROS and Nrf2/PD-L1 signaling

Background

Cisplatin resistance remains a major clinical obstacle to the successful treatment of non-small cell lung cancer (NSCLC). Scribble contributes to ROS-induced inflammation and cisplatin-elevated toxic reactive oxygen species (ROS) promotes cell death. However, it is unknown whether and how Scribble is involved in the cisplatin-related cell death and the underlying mechanism of Scribble in response to chemotherapies and in the process of oxidative stress in NSCLC.

Methods

We used two independent cohorts of NSCLC samples derived from patients treated with platinum-containing chemotherapy and xenograft modeling in vivo. We analyzed the correlation between Scribble and Nox2 or Nrf2/PD-L1 both in vivo and in vitro, and explored the role of Scribble in cisplatin-induced ROS and apoptosis.

Findings

Clinical analysis revealed that Scribble expression positively correlated with clinical outcomes and chemotherapeutic sensitivity in NSCLC patients. Scribble protected Nox2 protein from proteasomal degradation. Scribble knockdown induced cisplatin resistance by blocking Nox2/ROS and apoptosis in LRR domain-dependent manner. In addition, low levels of Scribble correlated with high levels of PD-L1 via activation of Nrf2 transcription in vivo and in vitro.

Interpretations

Our study revealed that polarity protein Scribble increased cisplatin-induced ROS generation and is beneficial to chemotherapeutic outcomes in NSCLC. Although Scribble deficiency tends to lead to cisplatin resistance by Nox2/ROS and Nrf2/PD-L1, it is still possible that Scribble deficiency-induced PD-L1 may yield benefits in immunotherapy.

Fund

National Key R&D Program of China, Strategic Priority Research Program of the Chinese Academy of Sciences, National Natural Science Foundation of China, China Postdoctoral Science Foundation.

Epithelial-mesenchymal transition is driven by transcriptional and post transcriptional modulations in COPD: implications for disease progression and new therapeutics

COPD is a common and highly destructive disease with huge impacts on people and health services throughout the world. It is mainly caused by cigarette smoking though environmental pollution is also significant. There are no current treatments that affect the overall course of COPD; current drugs focus on symptomatic relief and to some extent reducing exacerbation rates. There is an urgent need for in-depth studies of the fundamental pathogenic mechanisms that underpin COPD. This is vital, given the fact that nearly 40%-60% of the small airway and alveolar damage occurs in COPD well before the first measurable changes in lung function are detected. These individuals are also at a high risk of lung cancer. Current COPD research is mostly centered around late disease and/or innate immune activation within the airway lumen, but the actual damage to the airway wall has early onset. COPD is the end result of complex mechanisms, possibly triggered through initial epithelial activation. To change the disease trajectory, it is crucial to understand the mechanisms in the epithelium that are switched on early in smokers. One such mechanism we believe is the process of epithelial to mesenchymal transition. This article highlights the importance of this profound epithelial cell plasticity in COPD and also its regulation. We consider that understanding early changes in COPD will open new windows for therapy.

Context-dependent EMT programs in cancer metastasis

Epithelial-mesenchymal transition (EMT) is a developmental process whereby stationary, adherent cells acquire the ability to migrate. EMT is critical for dramatic cellular movements during embryogenesis; however, tumor cells can reactivate EMT programs, which increases their aggressiveness. In addition to motility, EMT is associated with enhanced stem cell properties and drug resistance; thus it can drive metastasis, tumor recurrence, and therapy resistance in the context of cancer. However, the precise requirements for EMT in metastasis have not been fully delineated, with different tumor types relying on discrete EMT effectors. Most tumor cells do not undergo a full EMT, but rather adopt some qualities of mesenchymal cells and maintain some epithelial characteristics. Emerging evidence suggests that partial EMT can drive distinct migratory properties and enhance the epithelial-mesenchymal plasticity of cancer cells as well as cell fate plasticity. This review discusses the diverse regulatory mechanisms and functional consequences of EMT, with an emphasis on the importance of partial EMT.

Multiple functions of HuR in urinary tumors

PURPOSE

Human embryonic lethal abnormal visual-like protein, HuR, belongs to a member of the Hu family of RNA-binding protein and plays a critical role in urinary tumors. The purpose of this review is to summarize the current literature to demonstrate the importance of HuR in urinary tract tumors' biology and explore the potential role in therapeutic strategies aimed at targeting this molecule in cancer cells.

METHODS

The relevant literature from PubMed and Medline databases is reviewed in this article.

RESULTS

Increasing evidence supports that HuR plays a critical role in urinary tumors' biology because it regulates the expression of many urinary tumors-associated molecules through post-transcriptional regulatory mechanisms (including mRNA trafficking, mRNA decay and protein translation). Recent studies have demonstrated that HuR is associated with chemoresistance of urinary tumors, suggesting that HuR might be a novel therapeutic target and a marker for therapeutic response and prognosis assessment.

CONCLUSION

HuR is associated with various urinary tumors biological characteristics. Targeted therapy of HuR may become an attractive treatment strategy. What's more, more preclinical and clinical trials of this targeted strategy are necessary for the treatment of urinary tumors.

Loss of Wwox drives metastasis in triple-negative breast cancer by JAK2/STAT3 axis

Loss of WW domain-containing oxidoreductase (Wwox) expression has been observed in breast cancer (BC). However, its regulatory effects are largely unknown, especially in triple-negative breast cancer (TNBC). Herein, gene expression profiling revealed that JAK/STAT3 pathway was one of the most differentially modulated pathways in basal-like BC cells. The lower expression of Wwox was significantly correlated with high activation of STAT3 in basal-like cells and TNBC tissues. Overexpression of Wwox markedly inhibited proliferation and metastasis of BC cells by suppressing STAT3 activation, which is to interact with JAK2 to inhibit JAK2 and STAT3 phosphorylation. Furthermore, Wwox limited STAT3 binding to the interleukin-6 promoter, repressing expression of the IL-6 cytokine. Altogether, our data established that Wwox suppresses BC cell metastasis and proliferation by JAK2/STAT3 pathway. Targeting of Wwox with STAT3 could offer a promising therapeutic strategy for TNBC.

In breast cancer, the loss of expression of WW domain-containing oxireductase (Wwox) has been observed. Here, the authors illustrate that in triple negative breast cancer models Wwox suppresses metastasis and proliferation via the JAK2/STAT3 pathway.

LKB1 obliterates Snail stability and inhibits pancreatic cancer metastasis in response to metformin treatment

Metastasis to distant organs is a particularly ominous feature of malignant cancer. LKB1 (also known as STK11) has been identified as a tumor suppressor in several types of cancers. Here, we show that LKB1 is at low levels and is negatively associated with poor clinical outcomes in pancreatic cancer (PC). LKB1 is inversely correlated with Snail protein in PC, in which the loss of LKB1 facilitates metastasis through elevating Snail protein level. Furthermore, LKB1 boosts Snail's interaction with E3 ligase FBXL14, leading to increasing ubiquitin‐mediated Snail degradation. Notably, metformin could increase Snail protein ubiquitination via augmenting the location of LKB1 at cytoplasm as well as increasing LKB1 expression. Altogether, our data established that LKB1 impedes invasion and metastasis by decreasing the Snail protein level in PC. Targeting the LKB1/FBXL14/Snail axis may represent a promising therapeutic strategy and metformin might be beneficial for PC therapy through activating the LKB1‐mediated Snail ubiquitination pathway.

Cell Extrusion: A Stress-Responsive Force for Good or Evil in Epithelial Homeostasis

Epithelial tissues robustly respond to internal and external stressors via dynamic cellular rearrangements. Cell extrusion acts as a key regulator of epithelial homeostasis by removing apoptotic cells, orchestrating morphogenesis, and mediating competitive cellular battles during tumorigenesis. Here, we delineate the diverse functions of cell extrusion during development and disease. We emphasize the expanding role for apoptotic cell extrusion in exerting morphogenetic forces, as well as the strong intersection of cell extrusion with cell competition, a homeostatic mechanism that eliminates aberrant or unfit cells. While cell competition and extrusion can exert potent, tumor-suppressive effects, dysregulation of either critical homeostatic program can fuel cancer progression.

Regulation of cellular and PCP signalling by the Scribble polarity module

Since the first identification of the Scribble polarity module proteins as a new class of tumour suppressors that regulate both cell polarity and proliferation, an increasing amount of evidence has uncovered a broader role for Scribble, Dlg and Lgl in the control of fundamental cellular functions and their signalling pathways. Here, we review these findings as well as discuss more specifically the role of the Scribble module in PCP signalling.

Post-transcriptional regulation of cytokine and growth factor signaling in cancer

Cytokines and growth factors regulate cell proliferation, differentiation, migration and apoptosis, and play important roles in coordinating growth signal responses during development. The expression of cytokine genes and the signals transmitted through cytokine receptors are tightly regulated at several levels, including transcriptional and post-transcriptional levels. A majority of cytokine mRNAs, including growth factor transcripts, contain AU-rich elements (AREs) in their 3' untranslated regions that control gene expression by regulating mRNA degradation and changing translational rates. In addition, numerous proteins involved in transmitting signals downstream of cytokine receptors are regulated at the level of mRNA degradation by GU-rich elements (GREs) found in their 3' untranslated regions. Abnormal stabilization and overexpression of ARE or GRE-containing transcripts had been observed in many malignancies, which is a consequence of the malfunction of RNA-binding proteins. In this review, we briefly summarize the role of AREs and GREs in regulating mRNA turnover to coordinate cytokine and growth factor expression, and we describe how dysregulation of mRNA degradation mechanisms contributes to the development and progression of cancer.

Induction of Glucocorticoid-induced Leucine Zipper (GILZ) Contributes to Anti-inflammatory Effects of the Natural Product Curcumin in Macrophages

GILZ (glucocorticoid-induced leucine zipper) is inducible by glucocorticoids and plays a key role in their mode of action. GILZ attenuates inflammation mainly by inhibition of NF-κB and mitogen-activated protein kinase activation but does not seem to be involved in the severe side effects observed after glucocorticoid treatment. Therefore, GILZ might be a promising target for new therapeutic approaches. The present work focuses on the natural product curcumin, which has previously been reported to inhibit NF-κB. GILZ was inducible by curcumin in macrophage cell lines, primary human monocyte-derived macrophages, and murine bone marrow-derived macrophages. The up-regulation of GILZ was neither associated with glucocorticoid receptor activation nor with transcriptional induction or mRNA or protein stabilization but was a result of enhanced translation. Because the GILZ 3'-UTR contains AU-rich elements (AREs), we analyzed the role of the mRNA-binding protein HuR, which has been shown to promote the translation of ARE-containing mRNAs. Our results suggest that curcumin treatment induces HuR expression. An RNA immunoprecipitation assay confirmed that HuR can bind GILZ mRNA. In accordance, HuR overexpression led to increased GILZ protein levels but had no effect on GILZ mRNA expression. Our data employing siRNA in LPS-activated RAW264.7 macrophages show that curcumin facilitates its anti-inflammatory action by induction of GILZ in macrophages. Experiments with LPS-activated bone marrow-derived macrophages from wild-type and GILZ knock-out mice demonstrated that curcumin inhibits the activity of inflammatory regulators, such as NF-κB or ERK, and subsequent TNF-α production via GILZ. In summary, our data indicate that HuR-dependent GILZ induction contributes to the anti-inflammatory properties of curcumin.

Hallmarks of cancer and AU-rich elements

Post‐transcriptional control of gene expression is aberrant in cancer cells. Sustained stabilization and enhanced translation of specific mRNAs are features of tumor cells. AU‐rich elements (AREs), cis‐acting mRNA decay determinants, play a major role in the posttranscriptional regulation of many genes involved in cancer processes. This review discusses the role of aberrant ARE‐mediated posttranscriptional processes in each of the hallmarks of cancer, including sustained cellular growth, resistance to apoptosis, angiogenesis, invasion, and metastasis. WIREs RNA 2017, 8:e1368. doi: 10.1002/wrna.1368

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