Pdcd4, a colon cancer prognostic that is regulated by a microRNA

PDCD4 as a marker of mTOR pathway activation and therapeutic target in mycobacterial infections

Programmed cell death protein 4 (PDCD4) is instrumental in regulating a range of cellular processes such as translation, apoptosis, signal transduction, and inflammatory responses. There is a notable inverse correlation between PDCD4 and the mammalian target of rapamycin (mTOR) pathway, which is integral to cellular growth control. Activation of mTOR is associated with the degradation of PDCD4. Although the role of PDCD4 is well established in oncogenesis and immune response regulation, its function in mycobacterial infections and its interplay with the mTOR pathway necessitate further elucidation. This study investigates the modulation of PDCD4 expression in the context of mycobacterial infections, revealing a consistent pattern of downregulation across diverse mycobacterial species. This observation underscores the potential utility of PDCD4 as a biomarker for assessing mTOR pathway activation during such infections. Building on this finding, we employed a novel approach using PDCD4-based mTOR (Tor)-signal-indicator (TOSI) reporter cells for the high-throughput screening of FDA-approved drugs, focusing on mTOR inhibitors. This methodology facilitated the identification of several agents, inclusive of known mTOR inhibitors, which upregulated PDCD4 expression and concurrently exhibited efficacy in impeding mycobacterial proliferation within macrophages. These results not only reinforce the significance of PDCD4 as a pivotal marker in the understanding of infectious diseases, particularly mycobacterial infections, but also illuminate its potential in the identification of mTOR inhibitors, thereby contributing to the advancement of therapeutic strategies.

IMPORTANCE

This study emphasizes the critical role of the mammalian target of rapamycin (mTOR) pathway in macrophage responses to mycobacterial infections, elucidating how mycobacteria activate mTOR, resulting in PDCD4 degradation. The utilization of the (Tor)-signal-indicator (TOSI) vector for real-time monitoring of mTOR activity represents a significant advancement in understanding mTOR regulation during mycobacterial infection. These findings deepen our comprehension of mycobacteria's innate immune mechanisms and introduce PDCD4 as a novel marker for mTOR activity in infectious diseases. Importantly, this research laid the groundwork for high-throughput screening of mTOR inhibitors using FDA-approved drugs, offering the potential for repurposing treatments against mycobacterial infections. The identification of drugs that inhibit mTOR activation opens new avenues for host-directed therapies, marking a significant step forward in combating tuberculosis and other mycobacterial diseases.

Inhibitory effect of microRNA-21 on pathways and mechanisms involved in cardiac fibrosis development

Cardiac fibrosis is a pivotal cardiovascular disease (CVD) process and represents a notable health concern worldwide. While the complex mechanisms underlying CVD have been widely investigated, recent research has highlighted microRNA-21's (miR-21) role in cardiac fibrosis pathogenesis. In this narrative review, we explore the molecular interactions, focusing on the role of miR-21 in contributing to cardiac fibrosis. Various signaling pathways, such as the RAAS, TGF-β, IL-6, IL-1, ERK, PI3K-Akt, and PTEN pathways, besides dysregulation in fibroblast activity, matrix metalloproteinases (MMPs), and tissue inhibitors of MMPs cause cardiac fibrosis. Besides, miR-21 in growth factor secretion, apoptosis, and endothelial-to-mesenchymal transition play crucial roles. miR-21 capacity regulatory function presents promising insights for cardiac fibrosis. Moreover, this review discusses numerous approaches to control miR-21 expression, including antisense oligonucleotides, anti-miR-21 compounds, and Notch signaling modulation, all novel methods of cardiac fibrosis inhibition. In summary, this narrative review aims to assess the molecular mechanisms of cardiac fibrosis and its essential miR-21 function.

Neuronal activity regulates the nuclear proteome to promote activity-dependent transcription

The formation and plasticity of neuronal circuits relies on dynamic activity-dependent gene expression. Although recent work has revealed the identity of important transcriptional regulators and of genes that are transcribed and translated in response to activity, relatively little is known about the cell biological mechanisms by which activity alters the nuclear proteome of neurons to link neuronal stimulation to transcription. Using nucleus-specific proteomic mapping in silenced and stimulated neurons, we uncovered an understudied mechanism of nuclear proteome regulation: activity-dependent proteasome-mediated degradation. We found that the tumor suppressor protein PDCD4 undergoes rapid stimulus-induced degradation in the nucleus of neurons. We demonstrate that degradation of PDCD4 is required for normal activity-dependent transcription and that PDCD4 target genes include those encoding proteins critical for synapse formation, remodeling, and transmission. Our findings highlight the importance of the nuclear proteasome in regulating the activity-dependent nuclear proteome and point to a specific role for PDCD4 as a regulator of activity-dependent transcription in neurons.

Circulating miRNA 27a and miRNA150-5p; a noninvasive approach to endometrial carcinoma

The search for novel non-invasive biomarkers such as epigenetic molecular markers is new hope for common and burdensome cancers. We aim to assess serum expression of miRNA 27a and miRNA150-5p in endometrial cancer patients. Serum was drawn for 36 un-intervened endometrial cancer patients scheduled for hysterectomy and 35 controls. miRNA 27a and miRNA150-5p were measured by real time reverse transcription polymerase chain reaction. Significant overexpression of both miRNA in patients (p < 0.001). At cutoffs 0.2872 & > 1.02, miRNA 27a showed 100% sensitivity, specificity, positive and negative predictive values. miRNA150-5p showed 88.89% sensitivity, 100% specificity, 100% positive and 78.9% negative predictive values. Areas under curve were 1.0 for miRNA 27a, 0.982 for miRNA 150 performing much better than Ca125. miRNA 27a was significantly associated with type I endometroid endometrial cancer. Conclusion: miRNA 27a and miRNA-150-5P can be suggested as promising biomarkers of endometrial cancer possibly part of a miRNA panel for management.

Exosomal miR-208b related with oxaliplatin resistance promotes Treg expansion in colorectal cancer

Oxaliplatin resistance is a challenge in the treatment of colorectal cancer (CRC) patients. Regulatory T cells (Tregs) are well known for their immunosuppressive roles, and targeting Tregs is an effective way to improve chemosensitivity. Exosome-delivered microRNA (miRNA) might be used as a potential biomarker for predicting chemosensitivity. However, the relationship between Tregs and exosomal miRNAs remains largely unknown. TaqMan low-density array was performed to screen the differentially expressed serum miRNAs from pooled serum of patients who had FOLFOX treatment. Differential expression was validated using qRT-PCR in individual samples. Exosomes were isolated by sequential differential centrifugation, and they were verified by transmission electron microscopy. The RNA and protein levels were determined by quantitative real-time PCR and western blotting. A mouse xenograft model was adopted to evaluate the correlation between exosome-derived miR-208b and Tregs in vivo. We demonstrated that circulating miR-208b is a non-invasive marker for predicting FOLFOX sensitivity in CRC. miR-208b in colon cancer was secreted by tumor cells in the pattern of exosomes, and oxaliplatin-resistant cells showed the most obvious phenomenon of miR-208b increase. Colon cancer cell-secreted miR-208b was sufficiently delivered into recipient T cells to promote Treg expansion by targeting programmed cell death factor 4 (PDCD4). Furthermore, in vivo studies indicated that Treg expansion mediated by cancer cell-secreted miR-208b resulted in tumor growth and oxaliplatin resistance. Our results demonstrate that tumor-secreted miR-208b promotes Treg expansion by targeting PDCD4, and it may be related to a decrease of oxaliplatin-based chemosensitivity in CRC. These findings highlight a potential role of exosomal miR-208b as a predictive biomarker for oxaliplatin-based therapy response, and they provide a novel target for immunotherapy.

A novel and distinctive mode of cell death revealed by using non-thermal atmospheric pressure plasma: The involvements of reactive oxygen species and the translation inhibitor Pdcd4

Cells death is indispensable for embryonic development, tissue homeostasis, and the elimination of cancer, virally infected, or degenerated cells in multicellular organisms. It occurs not only via existing modes but also via unidentified modes, whose elucidation requires. Exposure to non-thermal atmospheric pressure plasma (NTAPP) has been demonstrated to induce cell death, probably because of its ability to generate reactive oxygen species (ROS). However, the mode of this cell death and its underlying mechanism remained elusive. Here we show cell death occurring in a novel and distinctive mode different from apoptosis and necrosis/necroptosis through a mechanism that ROS mediate the loss of the translation inhibitor Programmed cell death 4 (Pdcd4) when cells are cultured in solutions activated by NTAPP irradiation. Thus, our study performed with NTAPP-activated solutions may provide insight into the existence of the atypical cell death in cells and some features of its distinguishing mode and underlying mechanism.

Repressing PDCD4 activates JNK/ABCG2 pathway to induce chemoresistance to fluorouracil in colorectal cancer cells

Background

Colorectal cancer (CRC) is the third major cause of cancer-related death worldwide, and fluorouracil (5-FU) is widely used in the treatment of CRC. However, acquired resistance to 5-FU has become an obstacle in the effective treatment of CRC. Adenosine triphosphate (ATP)-binding cassette sub-family G member 2 (ABCG2) has been found highly expressed in CRC patients with poor responsiveness to folinic acid/5-FU/irinotecan. However, the mechanisms of 5-FU resistance regulated by ABCG2 in CRC cells remain to be comprehensively understood. We aimed to explore the upstream mechanisms of ABCG2 involved in the regulation of chemoresistance in CRC cells.

Methods

We investigated the potential mechanisms of 5-FU resistance in HCT116, RKO, RKO microRNA-21 (miR-21) knockout, and acquired 5-FU-resistant HCT116 (HCT116/FUR) cells. The biochemical and biological analyses were conducted using semiquantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting, transfections, and rescue experiments, along with cell proliferation, viability, and colony formation assays. In order to investigate the efficacy of inhibiting the c-Jun NH2 terminal kinase (JNK) pathway to overcome 5-FU resistance, HCT116 and 5-FU-resistant HCT116 cells were inoculated into BALB/c-nu/nu mice to establish the cell-derived xenograft model.

Results

The results showed that ABCG2 expression in HCT116/FUR cells was higher compared to HCT116 cells. Overexpression of ABCG2 decreased sensitivity to 5-FU in HCT116 cells, but knockdown of ABCG2 decreased the survival rate in HCT116/FUR cells. Additionally, repressing programmed cell death 4 (PDCD4) activated the JNK pathway in HCT116/FUR cells. Overexpression of PDCD4 inhibited phosphorylation of c-Jun and ABCG2 expression, and recovered sensitivity to 5-FU in HCT116/FUR cells. Moreover, treatment with the JNK pathway inhibitor SP600125 downregulated ABCG2 expression and rescued sensitivity to 5-FU in HCT116/FUR cells. We also found that miR-21 expression in HCT116/FUR cells was higher compared to HCT116 cells. Finally, 5-FU treatment in combination with SP600125 significantly decreased tumorigenicity compared to other treatments in vivo.

Conclusions

Our results demonstrated that 5-FU treatment upregulated miR-21, which directly repressed PDCD4, and subsequently activated the JNK pathway, leading to the upregulation of ABCG2 in CRC cells. Inhibition of the JNK pathway overcame acquired 5-FU resistance both in vivo and in vitro.

Programmed cell death factor 4 (PDCD4), a novel therapy target for metabolic diseases besides cancer

Programmed cell death factor 4 (PDCD4) is originally described as a tumor suppressor gene that exerts antineoplastic effects by promoting apoptosis and inhibiting tumor cell proliferation, invasion, and metastasis. Several investigations have probed the aberrant expression of PDCD4 with the progression of metabolic diseases, such as polycystic ovary syndrome (PCOS), obesity, diabetes, and atherosclerosis. It has been ascertained that PDCD4 causes glucose and lipid metabolism disorders, insulin resistance, oxidative stress, chronic inflammatory response, and gut flora disorders to regulate the progression of metabolic diseases. This review aims to summarize the latest researches to uncover the structure, expression regulation, and biological functions of PDCD4 and to elucidate the regulatory mechanism of the development of tumors and metabolic diseases. This review has emphasized the understanding of the PDCD4 role and to provide new ideas for the research, diagnosis, and treatment of tumors and metabolic diseases.

PDCD4 deficiency ameliorates left ventricular remodeling and insulin resistance in a rat model of type 2 diabetic cardiomyopathy

OBJECTIVE

Diabetic cardiomyopathy (DCM) is characterized by cardiac remodeling, dysfunction, and insulin resistance; however, the underlying mechanism has not been fully elucidated. Programmed cell death 4 (PDCD4) is a novel inflammation and apoptosis gene, but its role in type 2 DCM remains elusive. We aimed to determine if PDCD4 intervention improves DCM by affecting left ventricular remodeling, function, and insulin resistance.

RESEARCH DESIGN AND METHODS

We designed a PDCD4^-/- rat, established a type 2 diabetes animal model, and constructed a PDCD4 overexpressed adenovirus and PDCD4 small interfer RNA (siRNA) vectors to alter PDCD4 expression in H9c2 cardiomyocytes. Thereafter, glucose levels, lipid metabolism, echocardiography, and extent of myocardial fibrosis, inflammation, and apoptosis were compared in vivo and in vitro.

RESULTS

PDCD4 deficiency improved insulin resistance, cardiac remodeling, and dysfunction in type 2 DCM rats and improved myocardial hypertrophy, fibrosis, inflammation, and apoptosis. Proliferation and transformation of cardiac fibroblasts was reduced via PDCD4 downregulation in vitro under high-glucose stimulation. Furthermore, PDCD4 regulated the myocardial phosphatidylinositol 3-kinase-protein kinase B (PI3K-AKT) pathway in vivo and in vitro. PDCD4 intervention affected cardiac remodeling, dysfunction, and insulin resistance by influencing fibrosis, inflammation, and apoptosis via the PI3K-AKT pathway in vivo.

CONCLUSIONS

PDCD4 knockdown protected against left ventricular remodeling, dysfunction, and insulin resistance in type 2 DCM rats. The underlying mechanisms may involve reducing cardiomyocyte apoptosis, inflammation, fibrosis, and normalized PI3K-AKT phosphorylation. To the best of our knowledge, our study is the first to report the effects and underlying mechanisms of PDCD4 in type 2 DCM. These results provide a potential new treatment avenue for improving the prognosis of patients with type 2 DCM.

PLEKHA5 regulates tumor growth in metastatic melanoma

BACKGROUND

PLEKHA5 has previously been identified as a novel molecule implicated in melanoma brain metastasis, a disease that continues to portend a poor prognosis. The aim of this study was to further investigate the functional role of PLEKHA5 in disseminated melanoma.

METHODS

The impact of PLEKHA5 on proliferation and tumor growth was examined in vitro and in melanoma xenograft models, including brain-tropic melanomas (melanomas tending to disseminate to the brain). In vitro loss- and gain-of-function studies were used to explore the underlying mechanisms of PLEKHA5-mediated tumor growth and the crosstalk between PLEKHA5 and PI3K/AKT/mTOR or MAPK/ERK signaling. The clinical relevance of PLEKHA5 dysregulation was further investigated in a cohort of matched cranial and extracranial melanoma metastases.

RESULTS

PLEKHA5 stable knockdown negatively regulated cell proliferation by inhibiting the G₁ -to-S cell cycle transition, which coincided with upregulation of the cell cycle regulator PDCD4. Conversely, ectopic PLEKHA5 expression exhibited the inverse effect. PLEKHA5 knockdown significantly inhibited tumor growth, whereas its overexpression upregulated the growth of tumors, which was induced by cranial and subcutaneous inoculation of cells in nude mice. PLEKHA5 modulation affected PDCD4 protein stability and was coupled with changes in PI3K/AKT/mTOR pathway signaling. High PDCD4 expression in cerebral specimens was associated with better overall survival.

CONCLUSIONS

This study further supports the role of PLEKHA5 as a regulator of melanoma growth at distant sites, including the brain. Furthermore, the results highlight the significance of PDCD4 dysregulation in disseminated melanoma and implicate PDCD4 as a possible causal link between PLEKHA5 and cell proliferation and growth.

Gene Selection for the Discrimination of Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide. Cancer discrimination is a typical application of gene expression analysis using a microarray technique. However, microarray data suffer from the curse of dimensionality and usual imbalanced class distribution between the majority (tumor samples) and minority (normal samples) classes. Feature gene selection is necessary and important for cancer discrimination.

OBJECTIVES

To select feature genes for the discrimination of CRC.

METHODS

We improve the feature selection algorithm based on differential evolution, DEFSw by using RUSBoost classifier and weight accuracy instead of the common classifier and evaluation measure for selecting feature genes from imbalance data. We firstly extract differently expressed genes (DEGs) from the CRC dataset of the TCGA and then select the feature genes from the DEGs using the improved DEFSw algorithm. Finally, we validate the selected feature gene sets using independent datasets and retrieve the cancer related information for these genes based on text mining through the Coremine Medical online database.

RESULTS

We select out 16 single-gene feature sets for colorectal cancer discrimination and 19 single-gene feature sets only for colon cancer discrimination.

CONCLUSIONS

In summary, we find a series of high potential candidate biomarkers or signatures, which can discriminate either or both of colon cancer and rectal cancer with high sensitivity and specificity.

The Regulatory Role of Non-coding RNAs on Programmed Cell Death Four in Inflammation and Cancer

Programmed cell death 4 (PDCD4) is a tumor suppressor gene implicated in many cellular functions, including transcription, translation, apoptosis, and the modulation of different signal transduction pathways. The downstream mechanisms of PDCD4 have been well-discussed, but its upstream regulators have not been systematically summarized. Noncoding RNAs (ncRNAs) are gene transcripts with no protein-coding potential but play a pivotal role in the regulation of the pathogenesis of solid tumors, cardiac injury, and inflamed tissue. In recent studies, many ncRNAs, especially microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), were found to interact with PDCD4 to manipulate its expression through transcriptional regulation and function as oncogenes or tumor suppressors. For example, miR-21, as a classic oncogene, was identified as the key regulator of PDCD4 by targeting its 3′-untranslated region (UTR) to promote tumor proliferation, migration, and invasion in colon, breast, and bladder carcinoma. Therefore, we reviewed the recently emerging pleiotropic regulation of PDCD4 by ncRNAs in cancer and inflammatory disorders and aimed to shed light on the mechanisms of associated diseases, which could be conducive to the development of novel treatment strategies for PDCD4-induced diseases.

DTL promotes cancer progression by PDCD4 ubiquitin-dependent degradation

Background

Ubiquitin E3 ligase CUL4A plays important oncogenic roles in the development of cancers. DTL, one of the CUL4-DDB1 associated factors (DCAFs), may involve in the process of cancer development. Programmed cell death 4 (PDCD4) is a tumor suppressor gene involved in cell apoptosis, transformation, invasion and tumor progression.

Methods

Affinity-purification mass spectrometry was used to identify potential DTL interaction proteins. Co-immunoprecipitation (Co-IP) was performed to verify protein interaction between DTL and PDCD4. mRNA levels in cancer cells and tissues were detected by Quantitative real-time PCR. Lentivirus was used to establish stable overexpression and knocking down cell lines for DTL and PDCD4. Transwell and wound healing assays were used to determine migration ability of cancer cells. Matrigel assay was used to determine invasion ability of cancer cells. MTT and colony formation assays were used to evaluate proliferation of cancer cells.

Results

In this study, programmed cell death 4 (PDCD4) was identified as a potential substrate of DTL. Co-IP and immunofluorescence assays further confirmed the interaction between DTL and PDCD4. Moreover, DTL overexpression decreased the protein level and accelerated the degradation rate of PDCD4. Through in vitro ubiquitination experiment, we proved that PDCD4 was degraded by DTL through ubiquitination. Clinically DTL was significantly up-regulated in cancer tissues than that in normal tissues. The survival curves showed that cancer patients with higher DTL expression owned lower survival rate. Functional experiments showed that DTL not only enhanced the proliferation and migration abilities of cancer cells, but also promoted the tumorigenesis in nude mice. Rescued experiment results demonstrated that silencing PDCD4 simultaneous with DTL recovered the phenotypes defect caused by DTL knocking down.

Conclusions

Our results elucidated that DTL enhanced the motility and proliferation of cancer cells through degrading PDCD4 to promote the development of cancers.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1358-x) contains supplementary material, which is available to authorized users.

The expression, significance and function of cancer susceptibility candidate 9 in lung squamous cell carcinoma: A bioinformatics and in vitro investigation

The cancer susceptibility candidate 9 (CASC9) gene has been reported to exert an oncogenic effect in several types of cancer. However, its role in lung squamous cell carcinoma (LUSC) is unknown. Therefore, the present study examined the expression of CASC9 in LUSC and non-cancer tissues by reverse transcription-quantitative polymerase chain reaction assays and by data mining of high-throughput public databases, including The Cancer Genome Atlas, the Gene Expression Omnibus, ArrayExpress and the Cancer Cell Line Encyclopedia. In vitro experiments were conducted to investigate the effects of CASC9 on the viability and the proliferation of LUSC cells. Furthermore, consulting the alteration status of CASC9 in LUSC from cBioPortal, functional enrichment analysis of co-expressed genes, prediction of potential transcription factors, and inspection of adjacent protein-coding genes were conducted to explore the potential molecular mechanism of CASC9 in LUSC. The results revealed that CASC9 was overexpressed in LUSC tissue, and significantly associated with the malignant progression of LUSC. In vitro experiments demonstrated that CASC9 knockdown by RNA interference attenuated the viability and proliferation of LUSC cells. Multiple copies of CASC9 gene were detected in 4 of 179 available sequenced LUSC cases. A functional enrichment analysis of 200 co-expressed genes indicated that these genes were significantly associated with terms, including 'cell-cell junction organization', 'desmosome organization', 'epidermis development', 'Hippo signaling pathway', 'pathogenic Escherichia coli infection' and 'PID HIF1 TF pathway'. Three genes, Fos-related antigen 2 (FOSL2), SWI/SNF complex subunit SMARCC2, and transcription factor COE1 (EBF1), were predicted by lncRNAMap to be associated with CASC9. Among these, the expression of FOSL2 and EBF1 was positively and negatively correlated with the expression of CASC9, respectively. Two adjacent protein-coding genes, cysteine-rich secretory protein LCCL domain-containing 1 and hepatocyte nuclear factor 4-γ, were also positively correlated with CASC9 expression. In conclusion, the present data suggest that CASC9 serves as an oncogene in LUSC and may be a promising target for alternative therapeutic options for patients with this condition.

A Feedback Loop between MicroRNA 155 (miR-155), Programmed Cell Death 4, and Activation Protein 1 Modulates the Expression of miR-155 and Tumorigenesis in Tongue Cancer

MicroRNA 155 (miR-155) is an oncomir, generated as a noncoding RNA from the BIC gene whose promoter activity is mainly controlled via activation protein 1 (AP-1) and NF-κB transcription factors. We found that the expression levels of miR-155 and programmed cell death 4 (Pdcd4) exhibit inverse relationships in tongue cancer cells (SAS and AWL) and tumor tissues compared to their relationships in normal FBM cells and normal tongue tissues, respectively. In silico and in vitro studies with the 3' untranslated region (UTR) of Pdcd4 via luciferase reporter assays, quantitative PCR (qPCR), and Western blotting showed that miR-155 directly targets Pdcd4 mRNA and blocks its expression. Ectopic expression of Pdcd4 or knockdown of miR-155 in tongue cancer cells predominantly reduces AP-1-dependent transcriptional activity of the BIC promoter and decreases miR-155 expression. In this study, we demonstrate that miR-155 expression is modulated by a feedback loop between Pdcd4, AP-1, and miR-155 which results in enhanced expression of miR-155 with a consequent progression of tongue tumorigenesis. Further, miR-155 knockdown increases apoptosis, arrests the cell cycle, regresses tumor size in xenograft nude mice, and reduces cell viability and colony formation in soft-agar and clonogenic assays. Thus, the restoration of Pdcd4 levels by the use of molecular manipulation such as using a miR-155 sponge has an essential role in the therapeutic intervention of cancers, including tongue cancer.

MicroRNA-21 mediates high phosphate-induced endothelial cell apoptosis

Hyperphosphatemia, the elevated level of inorganic phosphate (Pi) in serum, is associated with increased cardiovascular morbidities and mortality. The effects of high Pi on endothelial cells are not well studied. This study investigated high Pi-induced endothelial cell apoptosis and the role of microRNA-21. Mouse myocardial endothelial cells (MEC) were cultured in normal (1 mM) and high (5 mM) Pi conditions. Apoptosis was detected by TUNEL staining and flow cytometry. MicroRNA profiles of MEC response to changes in Pi concentration were obtained using gene expression arrays. Expression levels of the microRNA-21 target genes, programmed cell death gene 4 ( PDCD4), poly(ADP-ribose) polymerase ( PARP), and phosphatase and tensin homolog ( PTEN), as well as NF-κB were measured by Western blotting and RT-PCR. MicroRNA-21-specific inhibitors and mimics were used to study effects of microRNA-21 on MEC apoptosis and gene expression regulations. High Pi induced MEC apoptosis and upregulated microRNA-21 expression. MicroRNA-21-specific mimics reproduced high Pi-induced apoptosis in normal Pi medium, and microRNA-21 inhibitors ameliorated the high Pi induction of apoptosis, suggesting that microRNA-21 mediated high Pi-induced MEC apoptosis. The microRNA-21 targets PDCD4, PTEN, PARP, and NF-κB were significantly downregulated in high Pi conditions. High Pi-induced downregulation of PDCD4 was abolished by microRNA-21 inhibitors and selective ERK inhibitor (selumetinib) and was reproduced by microRNA-21 mimics. Inhibitors and mimics of microRNA-21 did not have effects on high Pi-induced NF-κB downregulation. Selumetinib blocked high Pi-induced NF-κB downregulation. MicroRNA-21 mediates high Pi-induced endothelial cell apoptosis, which involves an ERK1/2/microRNA-21/PDCD4 pathway. High Pi-induced downregulation of NF-κB expression is mediated by an ERK1/2 signaling-dependent but microRNA-21-independent mechanism.

The mechanisms and clinical significance of PDCD4 in colorectal cancer

In recent years, the incidence and mortality of colorectal cancer (CRC) have been on a global upward trend. There is an urgent need for effective tools to prevent and treat CRC and reduce morbidity and mortality of CRC patients. Recent evidence suggests that programmed cell death 4 (PDCD4), a novel tumor suppressor gene, inhibits tumor progression at transcriptional and translational levels and regulates multiple signal transduction pathways. However, little is known about the precise mechanisms regulating PDCD4 expression in CRC. In addition, several studies have demonstrated that the expression of in CRC is down-regulated or even absent. PDCD4 is therefore considered to be an independent prognostic factor in CRC and may be a potential support diagnostic tool for distinguishing in normal colon tissue, benign adenoma and CRC. This review will focus on the expression of PDCD4 in CRC and the relevant molecular mechanisms.

Expression of tumor suppressor programmed cell death 4 in endometrioid endometrial carcinomas and clinicopathological significance

Programmed cell death 4 (PDCD4), as a novel tumor suppressor, serves important roles in the pathogenesis of tumors. The expression of PDCD4 is downregulated or lost in various human tumors. However, the expression of PDCD4 in endometrial cancer and the clinicopathological significance remain unclear. The aim of the present study was to investigate the expression of PDCD4 in endometrioid endometrial carcinoma (EEC) and the association with clinicopathological parameters. The expression of PDCD4 in EEC tissues and control endometrium was detected by reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemistry. PDCD4 expression was also investigated in control endometrial glandular epithelial cells and the endometrial cancer KLE cell line by immunocytochemistry, and the association between PDCD4 expression and clinicopathological parameters of patients with EEC was analyzed. The results demonstrated that PDCD4-positive staining was mainly located in the cytoplasm of endometrial glandular epithelial cells and EEC cells. The staining index of PDCD4 in the proliferative phase was significantly increased compared with that in the secretory phase of control endometrium (P<0.001). There was significantly decreased PDCD4 expression in grade (G) 2/3 EEC tissues compared with the proliferative phase of control endometrium (P<0.001). PDCD4 expression was significantly associated with tumor grade. The PDCD4 levels in G1 EEC tissues were higher compared with the G2/3 EEC group (P<0.01). The results indicated that PDCD4 is associated with the histological grade of EEC, and that PDCD4 may be a valuable indicator of the degree of tumor malignancy in patients with EEC.

Depletion of the mRNA translation initiation inhibitor, programmed cell death protein 4 (PDCD4), impairs L6 myotube formation

The mechanistic (mammalian) target of rapamycin complex 1 (mTORC1) signaling is vital for optimal muscle mass and function. Although the significance of mTORC1 in stimulating muscle growth is unequivocal, evidence in support of its role during muscle regeneration is less clear. Here, we showed that the abundance (protein and mRNA) of the mTORC1/S6K1 substrate, programmed cell death protein 4 (PDCD4), is upregulated at the onset of differentiation of L6 and C2C12 cells. The increase in PDCD4 was not associated with any changes in S6K1 activation, but the abundance of beta transducing repeat‐containing protein (β‐TrCP), the ubiquitin ligase that targets PDCD4 for degradation, increased. Myoblasts lacking PDCD4 showed impaired myotube formation and had markedly low levels of MHC‐1. Analysis of poly (ADP‐ribose) Polymerase (PARP), caspase 7 and caspase 3 indicated reduced apoptosis in PDCD4‐deficient cells. Our data demonstrate a role for PDCD4 in muscle cell formation and suggest that interventions that target this protein may hold promise for managing conditions associated with impaired myotube formation.

[ARTICLE WITHDRAWN] Long Noncoding RNA LINC01296 Harbors miR-21a to Regulate Colon Carcinoma Proliferation and Invasion

Increasing evidence has demonstrated that aberrant expressions of long noncoding RNAs (lncRNAs) are closely correlated to various malignancies, as well as colon carcinoma (CC). The aim of this study was to investigate the role of lncRNA long intergenic noncoding RNA 001296 (LINC01296) in tumorigenesis of CC. The result of the quantitative real-time polymerase chain reaction (qRT-PCR) demonstrated that LINC01296 was upregulated in CC cancerous tissues and cell lines compared to adjacent normal tissue and normal liver cell lines. LINC01296 overexpression was associated with poor prognosis and lower survival rate. Moreover, LINC01296 silencing inhibited the proliferation and invasion of CC cells in vitro detected by epithelial–mesenchymal transition (EMT). Bioinformatics analysis revealed that miR-21a targeted the 3′-UTR of LINC01296. Rescue experiments confirmed that miR21a could reverse the function of LINC01296 on CC cells. Together, our findings indicated that overexpression of LINC01296 is associated with poor survival of CC patients and promotes CC cell progression by regulating miR-21a, providing a prognostic biomarker and therapeutic target.

Defining the regulatory role of programmed cell death 4 in laryngeal squamous cell carcinoma

Programmed cell death 4 (PDCD4) is decreased in many different kinds of malignant tumors. EMT endows tumor cells invasive and metastatic properties. However, few studies have determined the role of PDCD4 in the regulation of EMT in the context of laryngeal carcinoma. We examined the relationship between PDCD4 and EMT-associated proteins E-cadherin and N-cadherin using laryngeal carcinoma tissues. Gene manipulation was used to define the regulatory capacity of PDCD4. We report that PDCD4 and E-cadherin/N-cadherin expression were significantly changed in the carcinoma tissues, and their expression was associated with pathological grade, metastatic state, and clinical stage. The suppression of PDCD4 (and consequently, E-cadherin) was concomitant with increased proliferation and G2-phase arrest, decreased apoptosis, and increased cell invasion. PDCD4 upregulation reversed the above-mentioned results. In nude mice, PDCD4 knockdown increased tumor growth and pathological features, confirming the tumorigenic role of PDCD4. Finally, PDCD4 silencing was associated with dysregulation of the carcinogenic Wnt-β-catenin and the STAT3-miR-21 signaling pathways. This study revealed a dynamic regulatory relationship between PDCD4 and critical factors for EMT, establishing a broad, functional role for PDCD4 in laryngeal carcinoma, which may be propagated by the STAT3-miR-21 pathway. These findings provide new information on an EMT-associated target that may lead to a novel therapy.

MicroRNA-150 promotes cell proliferation, migration, and invasion of cervical cancer through targeting PDCD4

Recent studies have showed that microRNA-150 (miR-150) is up-regulated in various cancers including cervical cancer. However, the specific mechanism of miR-150 in the regulation of cell proliferation, migration and invasion is still unclear. In this study, a total of 150 cervical cancer samples, including 50 cervical cancer tissues, 50 corresponding adjacent non-neoplastic tissues, and 50 serum samples were collected from cervical cancer patients. 50 matched normal tissues and 50 serum samples were collected from the control group. MiR-150 was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Programmed cell death protein 4 (PDCD4) was evaluated by qRT-PCR and western blot. Cell migration and invasion were assessed by transwell assays. Proliferative abilities were determined by MTT assays. Luciferase reporter assay was employed to validate the direct target of PDCD4 by miR-150. We found that miR-150 was increased in cervical cancer specimens. In contrast, PDCD4 was decreased in cervical cancer tissues. MiR-150 promoted cell migration, invasion and proliferation through targeting PDCD4. These results collectively indicated that miR-150 might be used as a potential therapeutic biomarker in cervical cancer.

Evaluation of miRNA-196a2 and apoptosis-related target genes: ANXA1, DFFA and PDCD4 expression in gastrointestinal cancer patients: A pilot study

Previous reports have suggested the significant association of miRNAs aberrant expression with tumor initiation, progression and metastasis in cancer, including gastrointestinal (GI) cancers. The current preliminary study aimed to evaluate the relative expression levels of miR-196a2 and three of its selected apoptosis-related targets; ANXA1, DFFA and PDCD4 in a sample of GI cancer patients. Quantitative real-time PCR for miR-196a2 and its selected mRNA targets, as well as immunohistochemical assay for annexin A1 protein expression were detected in 58 tissues with different GI cancer samples. In addition, correlation with the clinicopathological features and in silico network analysis of the selected molecular markers were analyzed. Stratified analyses by cancer site revealed elevated levels of miR-196a2 and low expression of the selected target genes. Annexin protein expression was positively correlated with its gene expression profile. In colorectal cancer, miR-196a over-expression was negatively correlated with annexin A1 protein expression (r = -0.738, p < 0.001), and both were indicators of unfavorable prognosis in terms of poor differentiation, larger tumor size, and advanced clinical stage. Taken together, aberrant expression of miR-196a2 and the selected apoptosis-related biomarkers might be involved in GI cancer development and progression and could have potential diagnostic and prognostic roles in these types of cancer; particularly colorectal cancer, provided the results experimentally validated and confirmed in larger multi-center studies.

miR‑21 attenuates contrast‑induced renal cell apoptosis by targeting PDCD4

Contrast medium (CM) is widely used in cardiac catheterization; however, it may induce acute kidney injury or renal failure, although the underlying mechanism remains to be elucidated. MicroRNA‑21 (miR‑21) is involved in renal disease and has been indicated to regulate cellular apoptosis and fibrosis, although its role in CM‑induced renal cell injury is unknown. The present study examined the expression and potential targets of miR‑21 in human renal proximal tubular epithelial (HK‑2) cells following CM treatment. CM induced renal cell apoptosis and decreased miR‑21 expression. The expression level of the apoptosis regulator protein, B‑cell lymphoma 2 (Bcl‑2) was upregulated, whereas that of the apoptosis regulator, Bcl‑2‑associated X protein (Bax) was downregulated upon transfection of miR‑21 mimics; miR‑21 overexpression additionally directly inhibited the expression of programmed cell death protein 4 (PDCD4), as determined by a dual luciferase reporter assay, and PDCD4 silencing reduced the rate of HK‑2 cell apoptosis. The results of the present study indicated that miR‑21 protected renal cells against CM‑induced apoptosis by regulating PDCD4 expression.

Up-regulation of lncRNA CASC9 promotes esophageal squamous cell carcinoma growth by negatively regulating PDCD4 expression through EZH2

Background

Abnormal expression of numerous long non-coding RNAs (lncRNAs) has been reported in esophageal squamous cell carcinoma (ESCC) recently, but the great majority of their roles and mechanisms remain largely unclear. We aim to identify the critical ESCC-associated lncRNAs and elucidate the functions and mechanisms in detail.

Methods

Microarrays were used to analyze the differentially expressed lncRNAs in ESCC tissues. qRT-PCR was used to verify the result of microarrays. The effects of the most up-regulated lncRNA, cancer susceptibility candidate 9(CASC9), on cell growth, proliferation and cell cycle were investigated by in vivo and in vitro assays. Microarrays and recovery tests were used to discover the regulatory targets of CASC9. RNA FISH and subcellular fractionation assays were used to detect the subcellular location of CASC9. Finally, the mechanism of CASC9 regulating PDCD4 was explored by RIP, RNA-protein pull down and ChIP assays.

Results

ESCC tissue microarrays showed that CASC9 was the most up-regulated lncRNA. qRT-PCR analysis indicated that CASC9 expression was positively associated with tumor size and TNM stage, and predicted poor overall survival of ESCC patients. Knockdown of CASC9 inhibited ESCC cell growth in vitro and tumorigenesis in nude mice. Furthermore interfering CASC9 decreased cell proliferation and blocked cell cycle G1/S transition. CASC9-associated microarrays indicated that PDCD4 might be the target of CASC9. Consistent with this, PDCD4 expression was negatively associated with CASC9 expression in ESCC tissues and predicted good prognosis. Manipulating CASC9 expression in ESCC cells altered both PDCD4 mRNA and protein levels and cell cycle arrest caused by CASC9 knockdown could be rescued by suppressing PDCD4 expression. CASC9 located both in the nucleus and cytoplasm. Mechanistically, enhancer of zeste homolog2 (EZH2) could bind to both CASC9 and PDCD4 promoter region. Interfering CASC9 reduced the enrichment of EZH2 and H3K27me3 in the PDCD4 promoter region.

Conclusions

Our study firstly demonstrates that lncRNA CASC9 functions as an oncogene by negatively regulating PDCD4 expression through recruiting EZH2 and subsequently altering H3K27me3 level. Our study implicates lncRNA CASC9 as a valuable biomarker for ESCC diagnosis and prognosis.

Electronic supplementary material

The online version of this article (10.1186/s12943-017-0715-7) contains supplementary material, which is available to authorized users.

The role of tumour suppressor PDCD4 in beta cell death in hypoxia

Objective

Hypoxia is known to induce pancreatic beta cell dysfunction and apoptosis. Changes in Programmed Cell Death Gene 4 (PDCD4) expression have previously been linked with beta cell neogenesis and function. Our aim was to investigate the effects of hypoxia on cell viability, PDCD4 expression and subcellular localisation.

Methods

MIN6 beta cells and ARIP ductal cells were exposed to 1% (hypoxia) or 21% O₂ (normoxia) for 12 or 24 hours. MTT assay, HPI staining, scanning electron microscopy, western blotting and immunocytochemistry analyses were performed to determine the effect of hypoxia on cell viability, morphology and PDCD4 expression.

Results

24 hour exposure to hypoxia resulted in ~70% loss of beta cell viability (P<0.001) compared to normoxia. Both HPI staining and SEM analysis demonstrated beta cell apoptosis and necrosis after 12 hours exposure to hypoxia. ARIP cells also displayed hypoxia-induced apoptosis and altered surface morphology after 24 hours, but no significant growth difference (p>0.05) was observed between hypoxic and normoxic conditions. Significantly higher expression of PDCD4 was observed in both beta cells (P<0.001) and ductal (P<0.01) cells under hypoxic conditions compared to controls. PDCD4 expression was localised to the cytoplasm of both beta cells and ductal cells, with no observed effects of hypoxia, normoxia or serum free conditions on intracellular shuttling of PDCD4.

Conclusion

These findings indicate that hypoxia-induced expression of PDCD4 is associated with increased beta cell death and suggests that PDCD4 may be an important factor in regulating beta cell survival during hypoxic stress.

Molecular profiling of locally-advanced rectal adenocarcinoma using microRNA expression (Review)

Treatment for locally-advanced rectal cancer (LARC) typically consists of neoadjuvant chemoradiation followed by total mesorectal excision. Recently, there has been growing interest in non-operative management for patients who are medically-inoperable or wish to avoid surgical morbidity and permanent colostomy. Approximately 50% of patients who receive pre-operative neoadjuvant chemoradiation develop some degree of pathologic response. Approximately 10-20% of patients are found to have a complete pathologic response, a finding which has frequently been shown to predict better clinical outcomes, including local-regional control, distant metastasis and survival. Many recent studies have evaluated the role of molecular biomarkers in predicting response to neoadjuvant therapy. MicroRNAs (miRNAs) are an emerging class of biomarkers that have the potential to predict which patients are most likely to benefit from pre-operative therapy and from a selective surgical approach. Here, we review the published literature on microRNAs as prognostic and predictive biomarkers in rectal cancer after pre-operative therapy. In the future, the development of prospectively validated miRNA signatures will allow clinical implementation of miRNAs as prognostic and predictive signatures in LARC.

Current Status and Perspectives Regarding LNA-Anti-miR Oligonucleotides and microRNA miR-21 Inhibitors as a Potential Therapeutic Option in Treatment of Colorectal Cancer

Colorectal cancer (CRC) is among the leading causes of cancer-related death, principally due to its metastatic spread and multifactorial chemoresistance. The therapeutic failure can also be explained by inter- or intra-tumor genetic heterogeneity and tumor stromal content. Thus, the identification of novel prognostic biomarkers and therapeutic options are warranted in the management of CRC patients. There are data showing that microRNA-21 is elevated in different types of cancer, particularly colon adenocarcinoma and that this is association with a poor prognosis. This suggests that microRNA-21 may be of value as a potential therapeutic target. Furthermore, locked nucleic acid (LNA)-modified oligonucleotides have recently emerged as a therapeutic option for targeting dysregulated miRNAs in cancer therapy, through antisense-based gene silencing. Further work is required to identify innovative anticancer drugs that improve the current therapy either through novel combinatorial approaches or with better efficacy than conventional drugs. We aimed to provide an overview of the preclinical and clinical studies targeting key dysregulated signaling pathways in CRC as well as the therapeutic application of LNA-modified oligonucleotides, and miR inhibitors in the treatment of CRC patients. J. Cell. Biochem. 118: 4129-4140, 2017. © 2017 Wiley Periodicals, Inc.

Regulatory miRNAs in Colorectal Carcinogenesis and Metastasis

Colorectal cancer is one of the most common malignancies and is the second-leading cause of cancer-related death world-wide, which is linked to genetic mutations, epigenetic alterations, and oncogenic signaling activation. MicroRNAs, one of the categories of epigenetics, have been demonstrated significant roles in carcinogenesis and progression through regulating of oncogenic signaling pathways, stem cells, epithelial-mesenchymal transition, and metastasis. This review summarizes the roles of microRNAs in the regulating of Wnt, Ras, TGF-β, and inflammatory signaling pathways, stemness, and epithelial-mesenchymal transition, for carcinogenesis and metastasis in colorectal cancer. Improving our understanding of the mechanisms of regulatory interactions of microRNAs with signaling pathways in colorectal cancer formation and progression will aid in determining the genes responsible for colorectal cancer initiation, progression, metastasis, and recurrence and, finally, in developing personalized approaches for cancer prevention and therapy.

Inhibition of microRNA-21 via locked nucleic acid-anti-miR suppressed metastatic features of colorectal cancer cells through modulation of programmed cell death 4

Colorectal cancer is among the most lethal of malignancies, due to its propensity to metastatic spread and multifactorial-chemoresistance. The latter property supports the need to identify novel therapeutic approaches for the treatment of colorectal cancer. MicroRNAs are endogenous non-coding small RNA molecules that function as post-transcriptional regulators of gene expression. Recently, programmed cell death 4 has been identified as a protein that increases during apoptosis. This gene is among the potential targets of miR-21 (OncomiR). Locked nucleic acid-modified oligonucleotides have recently emerged as a potential therapeutic option for targeting microRNAs. The aim of this study was to explore the functional role of locked nucleic acid-anti-miR-21 in the LS174T cell line in vitro and in vivo models. LS174T cells were treated with locked nucleic acid-anti-miR-21 for 24, 48, and 72 h in vitro. The expression of miR-21 and PDCD4 at messenger RNA (mRNA) level was evaluated by quantitative real-time polymerase chain reaction, while the protein level of PDCD4 was determined by Western blotting. Cell migratory behavior and the cluster-forming ability of cells were assessed before and after therapy. The disseminated tumor cells were assessed in the chick chorioallantoic membrane model by Alu quantitative polymerase chain reaction. Locked nucleic acid-anti-miR-21 was transfected successfully into the LS174T cells and inhibited the expression of miR-21. Locked nucleic acid-anti-miR-21 inhibited the migration and the number of cells forming clusters. Moreover, we found that locked nucleic acid-anti-miR-21 transfection was associated with a significant reduction in metastatic properties as assessed by the in ovo model. Our findings demonstrated the novel therapeutic potential of locked nucleic acid-anti-miR-21 in colon adenocarcinoma with high miR-21 expression.

Assessment of histone tail modifications and transcriptional profiling during colon cancer progression reveals a global decrease in H3K4me3 activity

During colon cancer, epigenetic alterations contribute to the dysregulation of major cellular functions and signaling pathways. Modifications in chromatin signatures such as H3K4me3 and H3K9ac, which are associated with transcriptionally active genes, can lead to genomic instability and perturb the expression of gene sets associated with oncogenic processes. In order to further elucidate early pre-tumorigenic epigenetic molecular events driving CRC, we integrated diverse, genome-wide, epigenetic inputs (by high throughput sequencing of RNA, H3K4me3, and H3K9ac) and compared differentially expressed transcripts (DE) and enriched regions (DER) in an in-vivo rat colon cancer progression model. Carcinogen (AOM) effects were detected genome-wide at the RNA (116 DE genes), K9ac (49 DERs including 24 genes) and K4me3 (7678 DERs including 3792 genes) level. RNA-seq differential expression and pathway analysis indicated that interferon-associated innate immune responses were impacted by AOM exposure. Despite extensive associations between K4me3 DERs and colon tumorigenesis (1210 genes were linked to colorectal carcinoma) including FOXO3, GNAI2, H2AFX, MSH2, NR3C1, PDCD4 and VEGFA, these changes were not reflected at the RNA gene expression level during early cancer progression. Collectively, our results indicate that carcinogen-induced changes in gene K4me3 DERs are harbingers of future transcriptional events, which drive malignant transformation of the colon.

miR-208a-3p suppresses cell apoptosis by targeting PDCD4 in gastric cancer

Programmed cell death 4 (PDCD4) is a novel tumor suppressor gene and a promising target for anticancer therapies. PDCD4 is frequently downregulated in various human cancers; however, the molecular mechanism accounting for the loss expression of PDCD4 in cancers is not fully understood. In this study, we identified specific targeting sites for miR-208a-3p in the 3'-untranslated region (3'-UTR) of the PDCD4 gene which regulated PDCD4 expression. We demonstrated that miR-208a-3p suppressed apoptosis in gastric cancer cells by targeting PDCD4. We also showed that miR-208a-3p promoted the development of tumor growth in xenograft mice by negatively regulating PDCD4. Taken together, this study revealed a critical role for miR-208a-3p as an oncogenic miRNA in gastric carcinogenesis and it may provide a potential novel target for gastric cancer diagnosis and therapy.

Ubiquitin-specific protease 4 inhibits breast cancer cell growth through the upregulation of PDCD4

Breast cancer is a common malignant tumor affecting women. The study of the association between breast cancer and molecular aberrations may lead to the development of novel diagnostic and therapeutic strategies for the disease. In the present study, we examined the role of ubiquitin-specific protease 4 (USP4) in breast cancer. We found that USP4 expression was significantly decreased in breast cancer tissue samples compared with paired normal breast tissue samples (P<0.001). USP4 was identified as a tumor suppressor. In addition, by inducing USP4 overexpression (using a USP4 overexpression plasmid) or the knockdown of USP4 (by transfection with a USP4 shRNA plasmid), we found that USP4 inhibited cell proliferation in vitro. We also found that USP4 suppressed tumor growth by using a mouse tumor xenograft model. Moreover, programmed cell death 4 (PCD4) was identified to be a target of USP4, which plays a role as a tumor suppressor. As a whole, our findings sugggest that USP4 acts as a tumor suppressor in breast cancer and that it may be an effective target for the treatment of breast cancer.

Quercetin inhibits Cr(VI)-induced malignant cell transformation by targeting miR-21-PDCD4 signaling pathway

Hexavalent chromium [Cr(VI)] is an important human carcinogen associated with pulmonary diseases and lung cancer. Inhibition of Cr(VI)-induced carcinogenesis by a dietary antioxidant is a novel approach. Quercetin is one of the most abundant dietary flavonoids widely present in many fruits and vegetables, possesses potent antioxidant and anticancer properties. MicroRNA-21 (miR-21) is a key oncomiR significantly elevated in the majority of human cancers that exerts its oncogenic activity by targeting the tumor suppressor gene programmed cell death 4 (PDCD4). The present study examined the effect of quercetin on the inhibition of Cr(VI)-induced malignant cell transformation and the role of miR-21-PDCD4 signaling involved. Our results showed that quercetin decreased ROS generation induced by Cr(VI) exposure in BEAS-2B cells. Chronic Cr(VI) exposure induced malignant cell transformation, increased miR-21 expression and caused inhibition of PDCD4, which were significantly inhibited by the treatment of quercetin in a dose dependent manner. Nude mice injected with BEAS-2B cells chronically exposed to Cr(VI) in the presence of quercetin showed reduced tumor incidence compared to Cr(VI) alone treated group. Stable knockdown of miR-21 and overexpression of PDCD4 or catalase in BEAS-2B cells suppressed Cr(VI)-induced malignant transformation and tumorigenesis. Taken together, these results demonstrate that quercetin is able to protect BEAS-2B cells from Cr(VI)-induced carcinogenesis by targeting miR-21-PDCD4 signaling.

MicroRNAs as diagnostic and prognostic biomarkers in colorectal cancer

MicroRNAs (miRNAs) are key regulators involved in various tumors. They regulate cell cycle, apoptosis and cancer stemness, metastasis and chemoresistance by controlling their target gene expressions. Here, we mainly discuss the potential uses of miRNAs in colorectal cancer (CRC) diagnosis. We also shed light on the important corresponding miRNA targets and on the major regulators of miRNAs. Furthermore, we discuss miRNA activity in assessing the prognosis and recurrence of CRC as well as in modulating responsiveness to chemotherapy. Based on the various pro-oncogenic/anti-oncogenic roles of miRNAs, the advantages of a therapeutic strategy based on the delivery of miRNA mimics are also mentioned. Together, miRNA seems to be an excellent tool for effectively monitoring and targeting CRC.

Exosome-shuttling microRNA-21 promotes cell migration and invasion-targeting PDCD4 in esophageal cancer

Recent evidence indicates that exosomes can mediate certain microRNAs (miRNAs) involved in a series of biological functions in tumor occurrence and development. Our previous studies showed that microRNA-21 (miR-21) was abundant in both esophageal cancer cells and their corresponding exosomes. The present study explored the function of exosome-shuttling miR-21 involved in esophageal cancer progression. We found that exosomes could be internalized from the extracellular space to the cytoplasm. The exosome-derived Cy3-labeled miR-21 mimics could be transported into recipient cells in a neutral sphingomyelinase 2 (nSMase2)-dependent manner. miR-21 overexpression from donor cells significantly promoted the migration and invasion of recipient cells by targeting programmed cell death 4 (PDCD4) and activating its downstream c-Jun N-terminal kinase (JNK) signaling pathway after co-cultivation. Our population plasma sample analysis indicated that miR-21 was upregulated significantly in plasma from esophageal cancer patients and showed a significant risk association for esophageal cancer. Our data demonstrated that a close correlation existed between exosome-shuttling miR-21 and esophageal cancer recurrence and distant metastasis. Thus, exosome-shuttling miR-21 may become a potential biomarker for prognosis among esophageal cancer patients.

Diaryl Disulfides as Novel Stabilizers of Tumor Suppressor Pdcd4

The translation inhibitor and tumor suppressor Pdcd4 was reported to be lost in various tumors and put forward as prognostic marker in tumorigenesis. Decreased Pdcd4 protein stability due to PI3K-mTOR-p70S6K1 dependent phosphorylation of Pdcd4 followed by β-TrCP1-mediated ubiquitination, and proteasomal destruction of the protein was characterized as a major mechanism contributing to the loss of Pdcd4 expression in tumors. In an attempt to identify stabilizers of Pdcd4, we used a luciferase-based high-throughput compatible cellular assay to monitor phosphorylation-dependent proteasomal degradation of Pdcd4 in response to mitogen stimulation. Following a screen of approximately 2000 compounds, we identified 1,2-bis(4-chlorophenyl)disulfide as a novel Pdcd4 stabilizer. To determine an initial structure-activity relationship, we used 3 additional compounds, synthesized according to previous reports, and 2 commercially available compounds for further testing, in which either the linker between the aryls was modified (compounds 2-4) or the chlorine residues were replaced by groups with different electronic properties (compounds 5 and 6). We observed that those compounds with alterations in the sulfide linker completely lost the Pdcd4 stabilizing potential. In contrast, modifications in the chlorine residues showed only minor effects on the Pdcd4 stabilizing activity. A reporter with a mutated phospho-degron verified the specificity of the compounds for stabilizing the Pdcd4 reporter. Interestingly, the active diaryl disulfides inhibited proliferation and viability at concentrations where they stabilized Pdcd4, suggesting that Pdcd4 stabilization might contribute to the anti-proliferative properties. Finally, computational modelling indicated that the flexibility of the disulfide linker might be necessary to exert the biological functions of the compounds, as the inactive compound appeared to be energetically more restricted.

MicroRNA-21 induces 5-fluorouracil resistance in human pancreatic cancer cells by regulating PTEN and PDCD4

Pancreatic cancer patients are often resistant to chemotherapy treatment, which results in poor prognosis. The objective of this study was to delineate the mechanism by which miR-21 induces drug resistance to 5-fluorouracil (5-FU) in human pancreatic cancer cells (PATU8988 and PANC-1). We report that PATU8988 cells resistant to 5-FU express high levels of miR-21 in comparison to sensitive primary PATU8988 cells. Suppression of miR-21 expression in 5-Fu-resistant PATU8988 cells can alleviate its 5-FU resistance. Meanwhile, lentiviral vector-mediated overexpression of miR-21 not only conferred resistance to 5-FU but also promoted proliferation, migration, and invasion of PATU8988 and PANC-1 cells. The proresistance effects of miR-21 were attributed to the attenuated expression of tumor suppressor genes, including PTEN and PDCD4. Overexpression of PTEN and PDCD4 antagonized miR-21-induced resistance to 5-FU and migration activity. Our work demonstrates that miR-21 can confer drug resistance to 5-FU in pancreatic cancer cells by regulating the expression of tumor suppressor genes, as the target genes of miR-21, PTEN and PDCD4 can rescue 5-FU sensitivity and the phenotypic characteristics disrupted by miR-21.

Circulating microRNA Profiles in Patients with Type-1 Autoimmune Hepatitis

Recent studies have demonstrated that micro (mi)RNA molecules can be detected in the circulation and can serve as potential biomarkers of various diseases. This study used microarray analysis to identify aberrantly expressed circulating miRNAs in patients with type 1 autoimmune hepatitis (AIH) compared with healthy controls. Patients with well-documented and untreated AIH were selected from the National Hospital Organization (NHO)-AIH-liver-network database. They underwent blood sampling and liver biopsy with inflammation grading and fibrosis staging before receiving treatment. To further confirm the microarray data, circulating expression levels of miR-21 and miR-122 were quantified by real-time quantitative polymerase chain reaction in 46 AIH patients, 40 patients with chronic hepatitis C (CHC), and 13 healthy controls. Consistent with the microarray data, serum levels of miR-21 were significantly elevated in AIH patients compared with CHC patients and healthy controls. miR-21 and miR-122 serum levels correlated with alanine aminotransferase levels. Circulating levels of miR-21 and miR-122 were significantly reduced in AIH patients with liver cirrhosis, and were inversely correlated with increased stages of fibrosis. By contrast, levels of circulating miR-21 showed a significant correlation with the histological grades of inflammation in AIH. We postulate that aberrantly expressed serum miRNAs are potential biomarkers of AIH and could be implicated in AIH pathogenesis. Alternations of miR-21 and miR-122 serum levels could reflect their putative roles in the mediation of inflammatory processes in AIH.

Quantitative proteomic analysis of paired colorectal cancer and non-tumorigenic tissues reveals signature proteins and perturbed pathways involved in CRC progression and metastasis

Modern proteomics has proven instrumental in our understanding of the molecular deregulations associated with the development and progression of cancer. Herein, we profile membrane-enriched proteome of tumor and adjacent normal tissues from eight CRC patients using label-free nanoLC-MS/MS-based quantitative proteomics and advanced pathway analysis. Of the 948 identified proteins, 184 proteins were differentially expressed (P<0.05, fold change>1.5) between the tumor and non-tumor tissue (69 up-regulated and 115 down-regulated in tumor tissues). The CRC tumor and non-tumor tissues clustered tightly in separate groups using hierarchical cluster analysis of the differentially expressed proteins, indicating a strong CRC-association of this proteome subset. Specifically, cancer associated proteins such as FN1, TNC, DEFA1, ITGB2, MLEC, CDH17, EZR and pathways including actin cytoskeleton and RhoGDI signaling were deregulated. Stage-specific proteome signatures were identified including up-regulated ribosomal proteins and down-regulated annexin proteins in early stage CRC. Finally, EGFR(+) CRC tissues showed an EGFR-dependent down-regulation of cell adhesion molecules, relative to EGFR(-) tissues. Taken together, this study provides a detailed map of the altered proteome and associated protein pathways in CRC, which enhances our mechanistic understanding of CRC biology and opens avenues for a knowledge-driven search for candidate CRC protein markers.

miR-183 induces cell proliferation, migration, and invasion by regulating PDCD4 expression in the SW1990 pancreatic cancer cell line

The aim of this study was to investigate the function of miR-183 in the SW1990 cancer cell line, and the mechanisms regulating these processes. miRNAs are known to play important roles in cancer cell development. However, the pattern and biological role of miR-183 in pancreatic cancer remain largely unknown. Here, we have reported the reduction in pancreatic cancer cell growth in vitro by miR-183 intervention, by inducing apoptosis and decreasing the Bcl-2 expression. Moreover, miR-183 was observed to enhance pancreatic cancer cell migration and invasion, whereas inhibition of miR-183 caused an opposite effect. miR-183 inhibition was shown to increase E-cadherin expression and decrease N-cadherin expression. These regulatory actions play an important role in the cancer epithelial-mesenchymal transition (EMT). Mechanistically, we demonstrated that the overexpression of miR-183 decreased the expression of PDCD4 (programmed cell death 4) mRNA and protein, and vice versa. This helped to identify PDCD4 as the target genes in pancreatic cancer. In conclusion, our analyses indicated miR-183 to be an important contributor to cell migration. This could also be used as a potential therapeutic target for pancreatic cancer treatment.

STAT3 regulates the migration and invasion of a stem‑like subpopulation through microRNA‑21 and multiple targets in hepatocellular carcinoma

Despite advances in the detection and treatment of hepatocellular carcinoma (HCC), the prognosis remains poor partly due to recurrence or extra/intrahepatic metastasis. Stem‑like cancer cells are considered the source of malignant phenotypes including metastasis in various types of cancer. HCC side population (SP), considered as stem‑like cancer cells, plays an important role in the migration and invasion in HCC, while the mechanisms involved remain unknown. In the present study, high levels of STAT3 and phospho‑STAT3 were observed in MHCC97H SP cells compared with the main population (MP) cells. Inhibition of phospho‑STAT3 led to a reduction of miR‑21 expression, an increase of PTEN, RECK, and programmed cell death 4 (PDCD4) expression as well as the migration and invasion of SP cells. A set of rescue experiments was performed using different combinations of STAT3 inhibitor, miR‑21 mimics and siRNAs to observe the expression of miR‑21 targets, cell migration and invasion alterations. Data indicated that the alterations induced by STAT3 inhibition were partly reversed by the upregulation of miR‑21. Additionally, the cells migration and invasion when silencing the targets of miR‑21 were also reversed by STAT3 inhibition. In conclusion, the present study revealed the aberrant expression of STAT3 and miR‑21 in HCC SP cells. Targeting STAT3 may limit HCC migration and invasion, which is likely to involve the regulation of miR‑21 and its targets PTEN, RECK and PDCD4. Strategies directed towards STAT3 may therefore be a novel approach for the treatment of HCC.

microRNA-21-induced dissociation of PDCD4 from rictor contributes to Akt-IKKβ-mTORC1 axis to regulate renal cancer cell invasion

Renal cancer metastasis may result from oncogenic forces that contribute to the primary tumor. We have recently identified microRNA-21 as an oncogenic driver of renal cancer cells. The mechanism by which miR-21 controls renal cancer cell invasion is poorly understood. We show that miR-21 directly downregulates the proapoptotic protein PDCD4 to increase migration and invasion of ACHN and 786-O renal cancer cells as a result of phosphorylation/activation of Akt and IKKβ, which activate NFκB-dependent transcription. Constitutively active (CA) Akt or CA IKKβ blocks PDCD4-mediated inhibition and restores renal cancer cell migration and invasion. PDCD4 inhibits mTORC1 activity, which was reversed by CA IKKβ. Moreover, CA mTORC1 restores cell migration and invasion inhibited by PDCD4 and dominant negative IKKβ. Moreover, PDCD4 negatively regulates mTORC2-dependent Akt phosphorylation upstream of this cascade. We show that PDCD4 forms a complex with rictor, an exclusive component of mTORC2, and that this complex formation is reduced in renal cancer cells due to increased miR-21 expression resulting in enhanced phosphorylation of Akt. Thus our results identify a previously unrecognized signaling node where high miR-21 levels reduce rictor-PDCD4 interaction to increase phosphorylation of Akt and contribute to metastatic fitness of renal cancer cells.

The PDCD4/miR-21 pathway in medullary thyroid carcinoma

Programmed cell death 4 (PDCD4) is a tumor suppressor gene involved in tumorogenesis. MicroRNA-21 (miR-21) specifically targets PDCD4, and recent studies suggest that PDCD4 is also regulated by Akt (antiapoptotic regulator within phosphatidylinositol 3-kinase). Medullary thyroid carcinoma (MTC) is a rare neuroendocrine cancer, and disease stage at diagnosis represents the main prognostic indicator. A consecutive series of 64 MTCs was considered. REarranged during Transfection (RET) and rat sarcoma (RAS) mutation status was assessed by direct sequencing. Quantitative real-time polymerase chain reaction was used to quantify mature hsa-miR-21. PDCD4 and Ki-67 immunostaining was performed with an automated platform. Immunoblot analysis of PI3K/Akt pathway was done on thyroid tissues. MTCs were consistently associated with miR-21 up-regulation (P < .0016) and featured significant PDCD4 nuclear down-regulation. An inverse correlation emerged between miR-21 overexpression and PDCD4 down-regulation (P = .0013). At enrollment, high miR-21 levels were associated with high calcitonin levels (P = .0003), lymph node metastases (P = .001), and advanced stages (P = .0003). At the end of follow-up, high miR-21 levels were associated with biochemically persistent disease (P = .0076). At enrollment, instead, PDCD4 nuclear down-regulation was associated with high calcitonin levels (P = .04), more advanced stages of disease (P < .01), and persistent disease after the follow-up (P = .02). p-Akt was more expressed in RAS-mutated MTC than in nonmutated cancers and normal tissue. This study showed, in MTCs, that miR-21 regulates PDCD4 expression and also that the miR-21/PDCD4 pathway correlates with clinicopathological variables and prognosis. Further studies should investigate the role of miR-21 as a prognostic biomarker and the feasibility of using PDCD4-restoring strategies as a therapeutic approach to MTC.