Low tristetraprolin expression promotes cell proliferation and predicts poor patients outcome in pancreatic cancer

The oncogenic and tumor suppressive roles of RNA-binding proteins in human cancers

Posttranscriptional regulation is a mechanism for the cells to control gene regulation at the RNA level. In this process, RNA-binding proteins (RBPs) play central roles and orchestrate the function of RNA molecules in multiple steps. Accumulating evidence has shown that the aberrant regulation of RBPs makes  contributions to the initiation and progression of tumorigenesis via numerous mechanisms such as genetic changes, epigenetic alterations, and noncoding RNA-mediated regulations. In this article, we review the effects caused by RBPs and their functional diversity in the malignant transformation of cancer cells that occurs through the involvement of these proteins in various stages of RNA regulation including alternative splicing, stability, polyadenylation, localization, and translation. Besides this, we review the various interactions between RBPs and other crucial posttranscriptional regulators such as microRNAs and long noncoding RNAs in the pathogenesis of cancer. Finally, we discuss the potential approaches for targeting RBPs in human cancers.

Tristetraprolin: A cytosolic regulator of mRNA turnover moonlighting as transcriptional corepressor of gene expression

Tristetraprolin (TTP) is a nucleocytoplasmic 326 amino acid protein whose sequence is characterized by possessing two CCCH-type zinc finger domains. In the cytoplasm TTP function is to promote the degradation of mRNAs that contain adenylate/uridylate-rich elements (AREs). Mechanistically, TTP promotes the recruitment of poly(A)-specific deadenylases and exoribonucleases. By reducing the half-life of about 10% of all the transcripts in the cell TTP has been shown to participate in multiple cell processes that include regulation of gene expression, cell proliferation, metabolic homeostasis and control of inflammation and immune responses. However, beyond its role in mRNA decay, in the cell nucleus TTP acts as a transcriptional coregulator by interacting with chromatin modifying enzymes. TTP has been shown to repress the transactivation of NF-κB and estrogen receptor suggesting the possibility that it participates in the transcriptional regulation of hundreds of genes in human cells and its possible involvement in breast cancer progression. In this review, we discuss the cytoplasmic and nuclear functions of TTP and the effect of the dysregulation of its protein levels in the development of human diseases. We suggest that TTP be classified as a moonlighting tumor supressor protein that regulates gene expression through two different mechanims; the decay of ARE-mRNAs and a transcriptional coregulatory function.

Tristetraprolin, a Potential Safeguard Against Carcinoma: Role in the Tumor Microenvironment

Tristetraprolin (TTP), a well-known RNA-binding protein, primarily affects the expression of inflammation-related proteins by binding to the targeted AU-rich element in the 3' untranslated region after transcription and subsequently mediates messenger RNA decay. Recent studies have focused on the role of TTP in tumors and their related microenvironments, most of which have referred to TTP as a potential tumor suppressor involved in regulating cell proliferation, apoptosis, and metastasis of various cancers, as well as tumor immunity, inflammation, and metabolism of the microenvironment. Elevated TTP expression levels could aid the diagnosis and treatment of different cancers, improving the prognosis of patients. The aim of this review is to describe the role of TTP as a potential safeguard against carcinoma.

Mechanisms of resveratrol in the prevention and treatment of gastrointestinal cancer

Gastrointestinal (GI) cancer is one of the leading causes of cancer-related deaths worldwide. According to the Global Cancer Statistics, colorectal cancer is the second leading cause of cancer-related mortality, closely followed by gastric cancer (GC). Environmental, dietary, and lifestyle factors including cigarette smoking, alcohol intake, and genetics are the most important risk factors for GI cancer. Furthermore, infections caused by Helicobacter pylori are a major cause of GC initiation. Despite improvements in conventional therapies, including surgery, chemotherapy, and radiotherapy, the length or quality of life of patients with advanced GI cancer is still poor because of delayed diagnosis, recurrence and side effect. Resveratrol (3, 4, 5-trihydroxy-trans-stilbene; Res), a natural polyphenolic compound, reportedly has various pharmacologic functions including anti-oxidant, anti-inflammatory, anti-cancer, and cardioprotective functions. Many studies have demonstrated that Res also exerts a chemopreventive effect on GI cancer. Research investigating the anti-cancer mechanism of Res for the prevention and treatment of GI cancer has implicated multiple pathways including oxidative stress, cell proliferation, and apoptosis. Therefore, this paper provides a review of the function and molecular mechanisms of Res in the prevention and treatment of GI cancer.

The Tristetraprolin Family of RNA-Binding Proteins in Cancer: Progress and Future Prospects

Post-transcriptional regulation of gene expression plays a key role in cellular proliferation, differentiation, migration, and apoptosis. Increasing evidence suggests dysregulated post-transcriptional gene expression as an important mechanism in the pathogenesis of cancer. The tristetraprolin family of RNA-binding proteins (RBPs), which include Zinc Finger Protein 36 (ZFP36; commonly referred to as tristetraprolin (TTP)), Zinc Finger Protein 36 like 1 (ZFP36L1), and Zinc Finger Protein 36 like 2 (ZFP36L2), play key roles in the post-transcriptional regulation of gene expression. Mechanistically, these proteins function by binding to the AU-rich elements within the 3′-untranslated regions of their target mRNAs and, in turn, increasing mRNA turnover. The TTP family RBPs are emerging as key regulators of multiple biological processes relevant to cancer and are aberrantly expressed in numerous human cancers. The TTP family RBPs have tumor-suppressive properties and are also associated with cancer prognosis, metastasis, and resistance to chemotherapy. Herein, we summarize the various hallmark molecular traits of cancers that are reported to be regulated by the TTP family RBPs. We emphasize the role of the TTP family RBPs in the regulation of trait-associated mRNA targets in relevant cancer types/cell lines. Finally, we highlight the potential of the TTP family RBPs as prognostic indicators and discuss the possibility of targeting these TTP family RBPs for therapeutic benefits.

Posttranscriptional control of the replication stress response via TTP-mediated Claspin mRNA stabilization

ATR and CHK1 play key roles in the protection and recovery of the stalled replication forks. Claspin, an adaptor for CHK1 activation, is essential for DNA damage signaling and efficient replication fork progression. Here, we show that tristetraprolin (TTP), an mRNA-binding protein, can modulate the replication stress response via stabilization of Claspin mRNA. TTP depletion compromised specifically in the phosphorylation of CHK1, but not p53 or H2AX among other ATR substrates, and produced CHK1-defective replication phenotypes including accumulation of stalled replication forks. Importantly, the expression of siRNA-resistant TTP in TTP-deficient cells restored CHK1 phosphorylation and reduced the number of stalled replication forks as close to the control cells. Besides, we found that TTP was required for efficient replication fork progression even in the absence of exogenous DNA damage in a Claspin-dependent manner. Mechanistically, TTP was able to bind to the 3'-untranslated region of Claspin mRNA to increase the stability of Claspin mRNA which eventually contributed to the subsequent ATR-CHK1 activation upon DNA damage. Taken together, our results revealed an intimate link between TTP-dependent Claspin mRNA stability and ATR-CHK1-dependent replication fork stability to maintain replication fork integrity and chromosomal stability.

Plasma Messenger RNAs Identified Through Bioinformatics Analysis are Novel, Non-Invasive Prostate Cancer Biomarkers

Aim

To identify new biomarkers of prostate cancer (PCa) for the diagnosis and prediction of clinical outcomes.

Materials and Methods

Existing microarray data of PCa tissues in the Oncomine database were analyzed and candidate differentially expressed genes (DEGs) that may be novel and noninvasive biomarkers were obtained. On this basis, plasma mRNA was extracted from PCa patients and healthy donors. Furthermore, plasma mRNA expression of DEGs was evaluated by qRT-PCR. Finally, the diagnostic power of the biomarkers was evaluated in comparison to the clinical characteristics of the patients.

Results

In this study, the top five significantly overexpressed mRNA (AMACR, PPP1R14b, PCA3, DLX1, and RPL22L1) and the top five significantly underexpressed mRNA (DUOX1, EFS, GSTP1, S100A16, and NCRNA00087) were selected for further validation in PCa patients and healthy donors by qRT-PCR. The results showed that AMACR, DLX1, PCA3, DUOX1, and GSTP1 mRNA were stably amplified in plasma. Additionally, DLX1, PCA3, DUOX1, and GSTP1 mRNA expression was significantly different between PCa circulating free mRNA samples and healthy donors. These mRNAs may be useful biomarkers for PCa diagnosis.

Conclusion

Analysis of the expression of genes in the Oncomine database showed that DLX1, PCA3, and DUOX1 expressions have a cancer specific pattern in PCa. Collectively, DLX1, PCA3, and DUOX1 may be useful candidate biomarkers for PCa diagnosis.

Cancer the'RBP'eutics-RNA-binding proteins as therapeutic targets for cancer

RNA-binding proteins (RBPs) play a critical role in the regulation of various RNA processes, including splicing, cleavage and polyadenylation, transport, translation and degradation of coding RNAs, non-coding RNAs and microRNAs. Recent studies indicate that RBPs not only play an instrumental role in normal cellular processes but have also emerged as major players in the development and spread of cancer. Herein, we review the current knowledge about RNA binding proteins and their role in tumorigenesis as well as the potential to target RBPs for cancer therapeutics.

Roles of Tristetraprolin in Tumorigenesis

Genetic loss or mutations in tumor suppressor genes promote tumorigenesis. The prospective tumor suppressor tristetraprolin (TTP) has been shown to negatively regulate tumorigenesis through destabilizing the messenger RNAs of critical genes implicated in both tumor onset and tumor progression. Regulation of TTP has therefore emerged as an important issue in tumorigenesis. Similar to other tumor suppressors, TTP expression is frequently downregualted in various human cancers, and its low expression is correlated with poor prognosis. Additionally, disruption in the regulation of TTP by various mechanisms results in the inactivation of TTP protein or altered TTP expression. A recent study showing alleviation of Myc-driven lymphomagenesis by the forced expression of TTP has shed light on new therapeutic avenues for cancer prevention and treatment through the restoration of TTP expression. In this review, we summarize key oncogenes subjected to the TTP-mediated mRNA degradation, and discuss how dysregulation of TTP can contribute to tumorigenesis. In addition, the control mechanism underlying TTP expression at the posttranscriptional and posttranslational levels will be discussed.

Tristetraprolin Is a Prognostic Biomarker for Poor Outcomes among Patients with Low-Grade Prostate Cancer

Background: We studied the utility of the tumor suppressor Tristetraprolin (TTP, ZFP36) as a clinically relevant biomarker of aggressive disease in prostate cancer patients after radical prostatectomy (RP).Methods: TTP RNA expression was measured in an RP cohort of patients treated at Moffitt Cancer Center (MCC) and obtained from six publically available RP datasets with biochemical recurrence (BCR; total n = 1,394) and/or metastatic outcome data (total n = 1,222). TTP protein expression was measured by immunohistochemistry in a tissue microarray of 153 MCC RP samples. The time to BCR or metastasis based on TTP RNA or protein levels was calculated using the Kaplan-Meier analysis. Univariable and multivariable Cox proportional hazard models were performed on multiple cohorts to evaluate if TTP is a clinically relevant biomarker and to assess if TTP improves upon the Cancer of the Prostate Risk Assessment postsurgical (CAPRA-S) score for predicting clinical outcomes.Results: In all of the RP patient cohorts, prostate cancer with low TTP RNA or protein levels had decreased time to BCR or metastasis versus TTP-high tumors. Further, the decreased time to BCR in TTP-low prostate cancer was more pronounced in low-grade tumors. Finally, pooled survival analysis suggests that TTP RNA expression provides independent information beyond CAPRA-S to predict BCR.Conclusions: TTP is a promising prostate cancer biomarker for predicting which RP patients will have poor outcomes, especially for low-grade prostate cancer patients.Impact: This study suggests that TTP RNA expression can be used to enhance the accuracy of CAPRA-S to predict outcomes in patients treated with RP. Cancer Epidemiol Biomarkers Prev; 27(11); 1376-83. ©2018 AACR.

Tristetraprolin activation by resveratrol inhibits the proliferation and metastasis of colorectal cancer cells

Resveratrol (RSV) is a polyphenolic compound that naturally occurs in grapes, peanuts and berries. Considerable research has been conducted to determine the benefits of RSV against various human cancer types. Tristetraprolin (TTP) is an AU-rich element-binding protein that regulates mRNA stability and has decreased expression in human cancer. The present study investigated the biological effect of RSV on TTP gene regulation in colon cancer cells. RSV inhibited the proliferation and invasion/metastasis of HCT116 and SNU81 colon cancer cells. Furthermore, RSV induced a dose-dependent increase in TTP expression in HCT116 and SNU81 cells. The microarray experiment revealed that RSV significantly increased TTP expression by downregulating E2F transcription factor 1 (E2F1), a downstream target gene of TTP and regulated genes associated with inflammation, cell proliferation, cell death, angiogenesis and metastasis. Although TTP silencing inhibited TTP mRNA expression, the expression was subsequently restored by RSV. Small interfering RNA-induced TTP inhibition attenuated the effects of RSV on cell growth. In addition, RSV induced the mRNA-decaying activity of TTP and inhibited the relative luciferase activity of baculoviral IAP repeat containing 3 (cIAP2), large tumor suppressor kinase 2 (LATS2), E2F1, and lin‑28 homolog A (Lin28) in HCT116 and SNU81 cells. Therefore, RSV enhanced the inhibitory activity of TTP in HCT116 and SNU81 cells by negatively regulating cIAP2, E2F1, LATS2, and Lin28 expression. In conclusion, RSV suppressed the proliferation and invasion/metastasis of colon cancer cells by activating TTP.

Dysregulation of tristetraprolin and human antigen R promotes gastric cancer progressions partly by upregulation of the high-mobility group box 1

Aberrant expression of ARE-binding proteins (ARE-BPs) plays an important role in several diseases, including cancer. Both tristetraprolin (TTP) and human antigen R (HuR) are important ARE-BPs and always play opposite roles in regulating target mRNAs. Our previous work has demonstrated that TTP expression is decreased in gastric cancer (GC). In this study, we reported that HuR was elevated in GC cell lines and gastric cancer patients and that decreased TTP expression partly contributed to the elevated HuR levels by regulating its mRNA turnover. We also observed that dysregulation of TTP and HuR elevated the high-mobility group box 1 (HMGB1) expression in different ways. HuR promoted HMGB1 expression at translational level, while TTP regulated HMGB1 mRNA turnover by destabilizing its mRNA. Increased HuR promoted cancer cell proliferation and the metastasis potential partly by HMGB1. Using immunohistochemistry, we observed that both positive cytoplasmic and high-expression of nuclear HuR were associated with poor pathologic features and survival of GC patients. In conclusion, this study demonstrated that dysregulation of the TTP and HuR plays an important role in GC. Moreover, high HuR nuclear expression or aberrant cytoplasmic distribution may serve as a predictor of poor survival.

The RNA binding protein tristetraprolin down-regulates autophagy in lung adenocarcinoma cells

Tristetraprolin (TTP) is the most well-known member of RNA-binding zinc-finger protein that play a significant role in accelerating mRNA decay. Increasingly studies have reported that TTP was functioned as a tumor suppressor gene in several types of carcinomas, while its underlying mechanism is not clear yet. In the current study, we found that TTP overexpression decreased cell proliferation and increased cell death in lung adenocarcinoma cells, with the cell cycle arrest at the S phase. Remarkably, instead of inducing cell apoptosis directly, TTP overexpression alters cell autophagy. Our studies demonstrate that TTP overexpression has no effect on apoptosis related genes, but decreases the expression of autophagy-related genes, including Beclin 1 and LC3II. The level of autophagy flux assessed by infection with the mGFP-RFP-LC3 adenovirus construction has been blocked by TTP overexpression. Moreover, the autophagic vacuoles number detected by transmission electron microscopy decreased with TTP expression up-regulation. Our results indicate, for the first time, that TTP suppresses cell proliferation and increases cell death through cell autophagy pathway in lung cancer cells. Our study provides a new angle of view for TTP function as a tumor suppressor which could be targeted in tumor treatment.

Tristetraprolin disables prostate cancer maintenance by impairing proliferation and metabolic function

Tristetraprolin (TTP) is an RNA-binding protein that post-transcriptionally suppresses gene expression by delivering mRNA cargo to processing bodies (P-bodies) where the mRNA is degraded. TTP functions as a tumor suppressor in a mouse model of B cell lymphoma, and in some human malignancies low TTP expression correlates with reduced survival. Here we report important prognostic and functional roles for TTP in human prostate cancer. First, gene expression analysis of prostate tumors revealed low TTP expression correlates with patients having high-risk Gleason scores and increased biochemical recurrence. Second, in prostate cancer cells with low levels of endogenous TTP, inducible TTP expression inhibits their growth and proliferation, as well as their clonogenic growth. Third, TTP functions as a tumor suppressor in prostate cancer, as forced TTP expression markedly impairs the tumorigenic potential of prostate cancer cells in a mouse xenograft model. Finally, pathway analysis of gene expression data suggested metabolism is altered by TTP expression in prostate tumor cells, and metabolic analyses revealed that such processes are impaired by TTP, including mitochondrial respiration. Collectively, these findings suggest that TTP is an important prognostic indicator for prostate cancer, and augmenting TTP function would effectively disable the metabolism and proliferation of aggressive prostate tumors.

Emerging role of HuR in inflammatory response in kidney diseases

Human antigen R (HuR) is a member of the embryonic lethal abnormal vision (ELAV) family which can bind to the A/U rich elements in 3' un-translated region of mRNA and regulate mRNA splicing, transportation, and stability. Unlike other members of the ELAV family, HuR is ubiquitously expressed. Early studies mainly focused on HuR function in malignant diseases. As researches proceed, more and more proofs demonstrate its relationship with inflammation. Since most kidney diseases involve pathological changes of inflammation, HuR is now suggested to play a pivotal role in glomerular nephropathy, tubular ischemia-reperfusion damage, renal fibrosis and even renal tumors. By regulating the mRNAs of target genes, HuR is causally linked to the onset and progression of kidney diseases. Reports on this topic are steadily increasing, however, the detailed function and mechanism of action of HuR are still not well understood. The aim of this review article is to summarize the present understanding of the role of HuR in inflammation in kidney diseases, and we anticipate that future research will ultimately elucidate the therapeutic value of this novel target.

Loss of Sun2 promotes the progression of prostate cancer by regulating fatty acid oxidation

The role of Sun2 has been described by previous studies in various types of cancers, including breast cancer and lung cancer. However, its role and potential molecular mechanism in the progression of prostate cancer have not been fully elucidated. In the present study, we found that Sun2 expression was reduced in prostate cancer tissues compared with paired normal tissues, and that low expression of Sun2 was significantly correlated with Higher Gleason scores, postoperative T stage (pT), Lymph nodal invasion and Clinical pathological stages. In addition, reduced Sun2 Expression predicts poor survival of prostate cancer patients and could serve as an independent predictor of prostate cancer patients overall survival (OS).Furthermore, Sun2 overexpression inhibits the prostate cancer cells growth, and Sun2 knockdown promotes the prostate cancer cells growth both in vitro and vivo. Mechanical silencing of , Sun2 promoted fatty acid oxidation (FAO) in prostate cancer, prostate cancer cells growth promoted by Sun2 silencing could be reversed by the FAO inhibitor Etomoxir. Additionally, we also showed that serum amyloid A1 (SAA1) play a vital role in FAO, ATP and cell growth promoted by Sun2 loss in prostate cancer. These results suggest that Loss of Sun2 promoted the prostate cancer progression by regulating FAO.

Cell cycle RNA regulons coordinating early lymphocyte development

Lymphocytes undergo dynamic changes in gene expression as they develop from progenitor cells lacking antigen receptors, to mature cells that are prepared to mount immune responses. While transcription factors have established roles in lymphocyte development, they act in concert with post-transcriptional and post-translational regulators to determine the proteome. Furthermore, the post-transcriptional regulation of RNA regulons consisting of mRNAs whose protein products act cooperatively allows RNA binding proteins to exert their effects at multiple points in a pathway. Here, we review recent evidence demonstrating the importance of RNA binding proteins that control the cell cycle in lymphocyte development and discuss the implications for tumorigenesis. WIREs RNA 2017, 8:e1419. doi: 10.1002/wrna.1419 For further resources related to this article, please visit the WIREs website.