miR-200c dampens cancer cell migration via regulation of protein kinase A subunits

Identification of Circular RNA Circ_0003256 as a Novel Player in Pediatric Acute Myeloid Leukemia

BACKGROUND

Aberrant expression of circular RNAs (circRNAs) is tightly associated with the pathogenesis of human cancers, including pediatric acute myeloid leukemia (AML). In this report, we sought to define the precise action of circ_0003256 in the pathogenesis of pediatric AML.

MATERIALS AND METHODS

Circ_0003256, microRNA (miR)-582-3p, and protein kinase cAMP-activated catalytic subunit beta (PRKACB) were quantified by quantitative real-time polymerase chain reaction and Western blot. Cell proliferation, cycle distribution, and apoptosis were estimated by MTT, 5-ethynyl-2'-deoxyuridine, and flow cytometry assays, respectively. Direct relationships among circ_0003256, miR-582-3p, and PRKACB were verified by a dual-luciferase reporter and RNA pull-down assays.

RESULTS

Our data indicated that circ_0003256 was highly expressed in pediatric AML patients and cells. Suppression of circ_0003256 hindered cell proliferation and promoted apoptosis in THP-1 and MV4-11 cells. Mechanistically, circ_0003256 contained functional binding sites for miR-582-3p, and circ_0003256 suppression influenced cell behaviors by upregulating miR-582-3p. MiR-582-3p directly targeted and inhibited PRKACB and the inhibition of PRKACB phenocopied miR-582-3p overexpression in regulating cell functional behaviors. Moreover, circ_0003256 involved the posttranscriptional regulation of PRKACB through miR-582-3p.

CONCLUSION

Our findings identify that suppression of circ_0003256 impedes the malignant behaviors of pediatric AML cells by regulating PRKACB expression by competing for shared miR-582-3p.

MicroRNA expression profiling of endocrine sensitive and resistant breast cancer cell lines

Background

Methods

Results

Conclusions

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Around 50–60% of microRNAs were significantly differentially expressed between ER- and ER + breast cancer cell lines.

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Transfection of miR-200c-3p mimic into ER -ve cells induced MET and reduced cell motility.

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Transfecting of miR-449a inhibitor into ER -ve cells reduced cell invasion but did not induce EMT.

CircRAD18 Accelerates the Progression of Acute Myeloid Leukemia by Modulation of miR-206/PRKACB Axis

Background

Circular RNAs (circRNAs) play a crucial role in tumorigenesis. However, the effects of circRNAs on acute myeloid leukemia (AML) remain largely unexplored. We explored the function of circRAD18 in AML development.

Methods

QRT-PCR was performed for the levels of circRAD18, RAD18, microRNA-206 (miR-206) and protein kinase CAMP-activated catalytic subunit beta (PRKACB). Cell Counting Kit-8 (CCK-8) assay and colony formation assay were utilized for cell proliferation. Flow cytometry analysis was carried out to analyze cell apoptosis and cell cycle process. Transwell assay was manipulated for cell migration and invasion. Western blot assay was conducted for protein levels. Dual-luciferase reporter assay was adopted to verify the interaction between miR-206 and circRAD18 or PRKACB.

Results

CircRAD18 level was increased in AML patients’ blood specimens and AML cell lines compared to normal controls. CircRAD18 knockdown impeded the proliferation, migration and invasion and facilitated the apoptosis and cell cycle arrest in AML cells. Moreover, circRAD18 was identified as a sponge for miR-206, and circRAD18 knockdown-mediated effect on AML cell progression was reversed by miR-206 suppression. Additionally, PRKACB was the target gene of miR-206. MiR-206 overexpression suppressed the malignant behaviors of AML cells, while PRKACB elevation restored the effects.

Conclusion

CircRAD18 aggravated the malignancy of AML cells through reducing miR-206 expression and elevating PRKACB expression, indicating circRAD18 might be a therapeutic target for AML.

Transcriptional regulation of PRKAR2B by miR-200b-3p/200c-3p and XBP1 in human prostate cancer

The cyclic adenosine monophosphate (cAMP)-activated protein kinase A (PKA) pathway is profoundly implicated in Prostate cancer (PCa) progression. Previously, we showed that PRKAR2B, the type II-beta regulatory subunit of PKA, is highly expressed in castration-resistant prostate cancer (CRPC) and can induce epithelial-mesenchymal transition by activating Wnt/β-catenin signaling in PCa cells. However, the molecular mechanism of dysregulated PRKAR2B expression pattern is still largely unknown. In this study, we found that the mutation, copy number alteration, and methylation status of PRKAR2B gene have no correlation with its expression level in PCa. Then, we identified two microRNAs (miR-200b-3p and miR-200c-3p) to be critical regulators of PRKAR2B expression in PCa. Notably, miR-200b-3p and miR-200c-3p expression were significantly downregulated in metastatic CRPC and negatively correlated with the expression level of PRKAR2B in PCa tissues. Moreover, we characterized X-Box Binding Protein 1 (XBP1) as a key transcription factor responsible for PRKAR2B expression in PCa. Importantly, miR-200b-3p/200c-3p or XBP1 knockdown inhibited PCa cell proliferation and promoted cell apoptosis and these inhibitory roles could be largely restored by PRKAR2B, suggesting that PRKAR2B is a functional mediator of miR-200b-3p, miR-200c-3p, and XBP1 in PCa. Collectively, our study firstly identified miR-200b-3p/200c-3p and XBP1 as the critical upstream regulators of PRKAR2B in PCa and provided novel insights to PRKAR2B-driven PCa progression.

Cardiac myxoma and neural crests: a tense relationship

In cardiac myxomas, the malignant transformation process, selecting incidental gene mutations and leading to loss of proliferation control, has not a so drastic effects in terms of growth rate of tumor mass, but frequently the particular location of lesion engrosses the high risk for health. For accurate cancer cell profiling, it is important to establish the embryologic origin of malignant cells and their initial commitments, above all, in the sight of therapeutic strategies and solutions. Here, we advance, for cardiac myxoma, the hypothesis of an origin from cardiac neural crest cells and we attempt to support it by an integrated discussion of current knowledge about embryological characteristics of neural crest cells and most recent studies focusing cardiac myxomas. We discuss the relationship between the basic plasticity of cardiac neural crest cells and some typical mutations arising in neoplastic lesions as well as the expression of typical cell markers of neural crests derivatives. Dysfunctions in proliferative and migratory programs, focused in other studies, are evaluated in the context of the topological and histopathological characteristics of cardiac myxomas.

Effect of Stromal Cells in Tumor Microenvironment on Metastasis Initiation

The cellular environment where tumor cells reside is called the tumor microenvironment (TME), which consists of borders, blood vessels, lymph vessels, extracellular matrix (ECM), stromal cells, immune/inflammatory cells, secreted proteins, RNAs and small organelles. By dynamically interacting with tumor cells, stromal cells participate in all stages of tumor initiation, progression, metastasis, recurrence and drug response, and consequently, affect the fate of patients. During the processes of tumor evolution and metastasis initiation, stromal cells in TME also experience some changes and play roles in both the suppression and promotion of metastasis, while the overall function of stromal cells is beneficial for cancer cell survival and movement. In this review, we examine the effects of stromal cells in TME on metastasis initiation, including angiogenesis, epithelial-mesenchymal transition (EMT) and invasion. We also highlight functions of proteins, RNAs and small organelles secreted by stromal cells in their influences on multiple stages of tumor metastasis.

Role of Circular RNA DLEU2 in Human Acute Myeloid Leukemia

In the current study, we were interested in exploring the molecular mechanism of circular RNA DLEU2 (circRNA-DLEU2) (hsa_circ_0000488) and microRNA 496 (miR-496), as well as PRKACB, in human acute myeloid leukemia (AML) cell activities. The RNA expression levels of circRNA-DLEU2, hsa-miR-496, and PRKACB were assessed by quantitative real-time PCR (qRT-PCR). The proliferation and apoptosis abilities of the cells were determined by CCK8 assay and flow cytometry analysis. Target relationships between circRNA-DLEU2 and miR-496, as well as PRKACB, were analyzed by luciferase reporter assay and probe assay. Immunoblotting assays were used to detect the protein expression level of PRKACB. We also did <i>in vivo</i> experiments to observe tumor formation after overexpression of circRNA-DLEU2. Our data showed that circRNA-DLEU2 was upregulated in AML tissues and cells, which promoted AML cell proliferation and inhibited cell apoptosis. circRNA-DLEU2 promoted AML tumor formation <i>in vivo</i> miR-496 was inhibited by circRNA-DLEU2 and was downregulated in AML tissues. circRNA-DLEU2 inhibited miR-496 expression and promoted PRKACB expression. miR-496 antagonized the effects of PRKACB on MOLM-13 cell proliferation and apoptosis. Collectively, circRNA-DLEU2 accelerated human AML by suppressing miR-496 and promoting PRKACB expression.

Hybrid epithelial/mesenchymal phenotypes promote metastasis and therapy resistance across carcinomas

Cancer metastasis and therapy resistance are the major unsolved clinical challenges, and account for nearly all cancer-related deaths. Both metastasis and therapy resistance are fueled by epithelial plasticity, the reversible phenotypic transitions between epithelial and mesenchymal phenotypes, including epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). EMT and MET have been largely considered as binary processes, where cells detach from the primary tumor as individual units with many, if not all, traits of a mesenchymal cell (EMT) and then convert back to being epithelial (MET). However, recent studies have demonstrated that cells can metastasize in ways alternative to traditional EMT paradigm; for example, they can detach as clusters, and/or occupy one or more stable hybrid epithelial/mesenchymal (E/M) phenotypes that can be the end point of a transition. Such hybrid E/M cells can integrate various epithelial and mesenchymal traits and markers, facilitating collective cell migration. Furthermore, these hybrid E/M cells may possess higher tumor-initiation and metastatic potential as compared to cells on either end of the EMT spectrum. Here, we review in silico, in vitro, in vivo and clinical evidence for the existence of one or more hybrid E/M phenotype(s) in multiple carcinomas, and discuss their implications in tumor-initiation, tumor relapse, therapy resistance, and metastasis. Together, these studies drive the emerging notion that cells in a hybrid E/M phenotype may occupy 'metastatic sweet spot' in multiple subtypes of carcinomas, and pathways linked to this (these) hybrid E/M state(s) may be relevant as prognostic biomarkers as well as a promising therapeutic targets.

Identification of molecular targets for esophageal carcinoma diagnosis using miRNA-seq and RNA-seq data from The Cancer Genome Atlas: a study of 187 cases

Esophageal carcinoma (ESCA) is one of the most common malignancies worldwide, and its pathogenesis is complex. In this study, we identified differentially expressed miRNAs (DEMs) and genes (DEGs) of ESCA from The Cancer Genome Atlas (TCGA) database. The diagnostic values of DEMs were determined by receiver operating characteristic (ROC) analyses and validated based on data from Gene Expression Omnibus (GEO). The top five DEMs with the best diagnostic values were selected, and their potential targets were predicted by various in silico methods. These target genes were then identified among the DEGs from TCGA. Furthermore, the overlapping genes were subjected to protein-protein interaction (PPI) analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The miRNA-transcription factor (TF) regulatory relations were determined using CircuitsDB and TransmiR. Finally, the regulatory networks of miRNA-TF and miRNA-gene were constructed and analyzed. A total of 136 DEMs and 3541 DEGs were identified in ESCA. The top five DEMs with the highest area under the receiver operating characteristic curve (AUC) values were miRNA-93 (0.953), miRNA-21 (0.928), miRNA-4746 (0.915), miRNA-196a-1 (0.906) and miRNA-196a-2 (0.906). The combined AUC of these five DEMs was 0.985. The KEGG analysis with 349 overlapping genes showed that the calcium signaling pathway and the neuroactive ligand-receptor interaction were the most relevant pathways. The regulatory networks of miRNA-TF and miRNA-gene, including 38 miRNA-TF and 560 miRNA-gene pairs, were successfully established. Our findings may provide new insights into the molecular mechanisms of ESCA pathogenesis. Future research will aim to explore the role of novel miRNAs in the pathogenesis and improve the early diagnosis of ESCA.

MiR-590-3p suppresses epithelial-mesenchymal transition in intrahepatic cholangiocarcinoma by inhibiting SIP1 expression

The functional roles and clinical significances of miR-590-3p in ICC remain unclear. In the current study, we investigated the expression of miR-590-3p in tissues and sera of ICC by real-time quantitative polymerase chain reaction. We found miR-590-3p was significantly down-regulated in the sera and tissues of ICC patients, especially in those patients with lymph node metastasis or distant metastasis. AUC curves and Cox proportional hazards mode revealed serum miR-590-3p could be novel diagnostic and prognostic biomarker for ICC patients. MiR-590-3p dramatically suppressed epithelial-mesenchymal transition, cell migration, and invasion of ICC cells. SIP1 was identified as direct and functional target of miR-590-3p in ICC cells by luciferase assays. Finally, we found SIP1 expression was inversely correlated with miR-590-3p and closely related to diminished survival in ICC patients. These findings reveal functional and mechanistic roles of miR-590-3p and EMT activator SIP1 in the pathogenesis of ICC.

The epithelial-to-mesenchymal transition activator ZEB1 initiates a prometastatic competing endogenous RNA network

Epithelial tumor cells undergo epithelial-to-mesenchymal transition (EMT) to gain metastatic activity. Competing endogenous RNAs (ceRNAs) have binding sites for a common set of microRNAs (miRs) and regulate each other's expression by sponging miRs. Here, we address whether ceRNAs govern metastasis driven by the EMT-activating transcription factor ZEB1. High miR-181b levels were correlated with an improved prognosis in human lung adenocarcinomas, and metastatic tumor cell lines derived from a murine lung adenocarcinoma model in which metastasis is ZEB1-driven were enriched in miR-181b targets. ZEB1 relieved a strong basal repression of α1 integrin (ITGA1) mRNA, which in turn upregulated adenylyl cyclase 9 mRNA (ADCY9) by sponging miR181b. Ectopic expression of the ITGA1 3'-untranslated region reversed miR-181b-mediated metastasis suppression and increased the levels of adenylyl cyclase 9 protein (AC9), which promoted tumor cell migration and metastasis. In human lung adenocarcinomas, ITGA1 and ADCY9 levels were positively correlated, and an AC9-activated transcriptomic signature had poor-prognostic value. Thus, ZEB1 initiates a miR-181b-regulated ceRNA network to drive metastasis.

A Novel TP53 Mutation Associated with TWIST1 and SIP1 Expression in an Aggressive Adrenocortical Carcinoma

Adrenocortical carcinomas (ACC) are very rare tumors related to TP53 mutations mostly in childhood onset cases. Epithelial-mesenchymal transition (EMT) transcription factors TWIST1 and Smad interacting protein 1 (SIP1) are related to poorer outcomes in other malignancies, but their role in ACC is unknown. We describe a case of an advanced metastatic ACC (Weiss-score of 9) in a patient at age 76. After primary tumor resection, mitotane therapy was started as palliation to low-volume liver metastasis. After a 2-year period of stable disease, the patient died due to brain metastasis. Somatic gene sequencing revealed a novel TP53 mutation in DNA extracted from paraffin-embedded tissue, a deletion of 8bp in exon 8 (c.811_818del8; GAGGTGCG/-) in homo or hemizygosis causing a subsequent frameshift and premature stop codon at position 302. Immunohistochemistry of P53 and p-Ser-15 P53 showed absent tumoral staining. In addition, immunohistochemical analysis showed an increased expression of the mesenchymal markers vimentin and fibronectin. At last, EMT transcription factors TWIST1 and SIP1 were also overexpressed in tumoral cells. This case report describes an aggressive ACC with not only a novel somatic mutation, but also a novel International Agency for Research on Cancer database 8 base-pair deletion in TP53 exon 8. In addition, the expression of EMT inducers TWIST1 and SIP1 have been reported for the first time in an ACC case. Further investigation is needed to clarify the biologic significance of this new TP53 mutation and its role in the EMT process.

Proteome profiling of clear cell renal cell carcinoma in von Hippel-Lindau patients highlights upregulation of Xaa-Pro aminopeptidase-1, an anti-proliferative and anti-migratory exoprotease

Patients of the von Hippel-Lindau (VHL) disease frequently develop clear cell renal cell carcinoma (ccRCC). Using archived, formalin-fixed, paraffin-embedded (FFPE) samples, we sought to determine global proteome alterations that distinguish ccRCC tissue from adjacent, non-malignant kidney tissue in VHL-patients. Our quantitative proteomic analysis clearly discriminated tumor and non-malignant tissue. Significantly dysregulated proteins were distinguished using the linear models for microarray data algorithm. In the ccRCC tissue, we noticed a predominant under-representation of proteins involved in the tricarboxylic acid cycle and an increase in proteins involved in glycolysis. This profile possibly represents a proteomic fingerprint of the "Warburg effect", which is a molecular hallmark of ccRCC. Furthermore, we observed an increase in proteins involved in extracellular matrix organization. We also noticed differential expression of many exoproteases in the ccRCC tissue. Of particular note were opposing alterations of Xaa-Pro Aminopeptidases-1 and -2 (XPNPEP-1 and -2): a strong decrease of XPNPEP-2 in ccRCC was accompanied by abundant presence of the related protease XPNPEP-1. In both cases, we corroborated the proteomic results by immunohistochemical analysis of ccRCC and adjacent, non-malignant kidney tissue of VHL patients. To functionally investigate the role of XPNPEP-1 in ccRCC, we performed small-hairpin RNA mediated XPNPEP-1 expression silencing in 786-O ccRCC cells harboring a mutated VHL gene. We found that XPNPEP-1 expression dampens cellular proliferation and migration. These results suggest that XPNPEP-1 is likely an anti-target in ccRCC. Methodologically, our work further validates the robustness of using FFPE material for quantitative proteomics.

Re-expression of miR-200c suppresses proliferation, colony formation and in vivo tumor growth of murine claudin-low mammary tumor cells

Claudin-low breast cancer is a relatively rare breast cancer subtype. These cancers are typically ER-/PR-/HER2- and express high levels of mesenchymal genes as well as genes associated with inflammation, angiogenesis and stem cell function. In addition to alterations in gene expression, it was recently demonstrated that claudin-low breast cancers express very low levels of the miR-200 family of miRNAs. Given that each miRNA can regulate tens, hundreds or even thousands of genes, miRNAs are being evaluated as therapeutic targets. In this study we show that mammary tumors from MTB-IGFIR transgenic mice and cell lines derived from these tumors represent a model of human claudin-low breast cancer and murine claudin-low mammary tumors and cell lines express only very low levels of all five members of the miR-200 family. Reduced miR-200 family expression appears to be regulated via methylation as cells and tumors expressing low levels of miR-200 family members had higher levels of CpG methylation in a putative promoter region than tumors and cells expressing high levels of miR-200 family members. Re-expression of miR-200c in murine claudin-low mammary tumor cells inhibited tumor cell proliferation and colony formation in vitro and tumor growth in vivo. With respect to tumor growth in vivo, re-expression of miR-200c was associated with a reduction in tumor vasculature and expression of Flt1 and Vegfc. Therefore, miR-200c is an important regulator of mesenchymal tumor cell growth.

NR2F2 inhibits Smad7 expression and promotes TGF-β-dependent epithelial-mesenchymal transition of CRC via transactivation of miR-21

Metastasis is one of the most decisive factors influencing CRC patient prognosis and current studies suggest that a molecular mechanism known as EMT broadly regulates cancer metastasis. NR2F2 is a key molecule in the development of CRC, but the roles and underlying mechanisms of NR2F2 in TGF-β induced EMT in CRC remain largely unknown. In the current study, we were interested to examine the role of NR2F2 in the TGF-β-induced EMT in CRC. Here, we found NR2F2 was upregulated in CRC cells and promotes TGF-β-induced EMT in CRC. Using comparative miRNA profiling TGF-β pre-treated CRC cells in which NR2F2 had been knocked down with that of control cells, we identified miR-21 as a commonly downregulated miRNA in HT29 cells treated with TGF-β and NR2F2 siRNA, and its downregulation inhibiting migration and invasion of CRC cells. Moreover, we found NR2F2 could transcriptional activated miR-21 expression by binding to miR-21 promoter in HT29 by ChIP and luciferase assay. In the last, our data demonstrated that Smad7 was the direct target of miR-21 in CRC cells. Thus, NR2F2 could promote TGF-β-induced EMT and inhibit Smad7 expression via transactivation of miR-21, and NR2F2 may be a new common therapeutic target for CRC.

PRKAR1A is a functional tumor suppressor inhibiting ERK/Snail/E-cadherin pathway in lung adenocarcinoma

Protein Kinase cAMP-Dependent Regulatory Type I Alpha (PRKAR1A) is a tissue-specific extinguisher that transduces a signal through phosphorylation of different target proteins. Loss of PRKAR1A was frequently observed in endocrine neoplasia and stromal cell tumors. However, a few cases were seen in epithelial tumors. Previously, we first found that PRKAR1A was downregulated in lung adenocarcinoma patients. Thus, the present study aimed to clarify its clinical implication and biological function as a tumor suppressor in lung adenocarcinoma. The low levels of PRKAR1A transcript were correlated with tumor progression and poor overall survival. The re-expression of PRKAR1A in H1299 cells suppressed the tumor cell proliferation and migration; stable knockdown (KD) of PRKAR1A in A549 cells enhanced this function both in vitro and in vivo. Moreover, KD of PRKAR1A in A549 cells promoted the statistical colonization of circulating tumor cells to the lungs in nude mice. These effects by PRKAR1A were attributed to inhibiting E-cadherin expression. Elevated E-cadherin significantly suppressed the PRKAR1A-KD induced cell proliferation and migration. Most notably, deletion of PRKAR1A inhibited E-cadherin by activating ERK/Snail signaling. In conclusion, PRKAR1A was a potent suppressor, and through the inhibition of PRKAR1A-ERK-Snail-E-cadherin axis could serve as a potential therapeutic target.

Functional characterization of AMP-activated protein kinase signaling in tumorigenesis

AMP-activated protein kinase (AMPK) is a ubiquitously expressed metabolic sensor among various species. Specifically, cellular AMPK is phosphorylated and activated under certain stressful conditions, such as energy deprivation, in turn to activate diversified downstream substrates to modulate the adaptive changes and maintain metabolic homeostasis. Recently, emerging evidences have implicated the potential roles of AMPK signaling in tumor initiation and progression. Nevertheless, a comprehensive description on such topic is still in scarcity, especially in combination of its biochemical features with mouse modeling results to elucidate the physiological role of AMPK signaling in tumorigenesis. Hence, we performed this thorough review by summarizing the tumorigenic role of each component along the AMPK signaling, comprising of both its upstream and downstream effectors. Moreover, their functional interplay with the AMPK heterotrimer and exclusive efficacies in carcinogenesis were chiefly explained among genetically altered mice models. Importantly, the pharmaceutical investigations of AMPK relevant medications have also been highlighted. In summary, in this review, we not only elucidate the potential functions of AMPK signaling pathway in governing tumorigenesis, but also potentiate the future targeted strategy aiming for better treatment of aberrant metabolism-associated diseases, including cancer.

miR-200c: a versatile watchdog in cancer progression, EMT, and drug resistance

MicroRNAs (miRNAs) are 20-22-nucleotide small endogenous non-coding RNAs which regulate gene expression at post-transcriptional level. In the last two decades, identification of almost 2600 miRNAs in human and their potential to be modulated opened a new avenue to target almost all hallmarks of cancer. miRNAs have been classified as tumor suppressors or oncogenes depending on the phenotype they induce, the targets they modulate, and the tissue where they function. miR-200c, an illustrious tumor suppressor, is one of the highly studied miRNAs in terms of development, stemness, proliferation, epithelial-mesenchymal transition (EMT), therapy resistance, and metastasis. In this review, we first focus on the regulation of miR-200c expression and its role in regulating EMT in a ZEB1/E-cadherin axis-dependent and ZEB1/E-cadherin axis-independent manner. We then describe the role of miR-200c in therapy resistance in terms of multidrug resistance, chemoresistance, targeted therapy resistance, and radiotherapy resistance in various cancer types. We highlight the importance of miR-200c at the intersection of EMT and chemoresistance. Furthermore, we show how miR-200c coordinates several important signaling cascades such as TGF-β signaling, PI3K/Akt signaling, Notch signaling, VEGF signaling, and NF-κB signaling. Finally, we discuss miR-200c as a potential prognostic/diagnostic biomarker in several diseases, but mainly focusing on cancer and its potential application in future therapeutics.