Antagonism of microRNA-99a promotes cell invasion and down-regulates E-cadherin expression in pancreatic cancer cells by regulating mammalian target of rapamycin

Expression of mTOR in normal and pathological conditions

The mechanistic/mammalian target of rapamycin (mTOR), a protein discovered in 1991, integrates a complex pathway with a key role in maintaining cellular homeostasis. By comprising two functionally distinct complexes, mTOR complex 1 (mTORC1) and mTORC2, it is a central cellular hub that integrates intra- and extracellular signals of energy, nutrient, and hormone availability, modulating the molecular responses to acquire a homeostatic state through the regulation of anabolic and catabolic processes. Accordingly, dysregulation of mTOR pathway has been implicated in a variety of human diseases. While major advances have been made regarding the regulators and effectors of mTOR signaling pathway, insights into the regulation of mTOR gene expression are beginning to emerge. Here, we present the current available data regarding the mTOR expression regulation at the level of transcription, translation and mRNA stability and systematize the current knowledge about the fluctuations of mTOR expression observed in several diseases, both cancerous and non-cancerous. In addition, we discuss whether mTOR expression changes can be used as a biomarker for diagnosis, disease progression, prognosis and/or response to therapeutics. We believe that our study will contribute for the implementation of new disease biomarkers based on mTOR as it gives an exhaustive perspective about the regulation of mTOR gene expression in both normal and pathological conditions.

The Role of Circulating MicroRNAs in Patients with Early-Stage Pancreatic Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is increasing in incidence and is still associated with a high rate of mortality. Only a minority of patients are diagnosed in the early stage. Radical surgery is the only potential curative procedure. However, radicality is reached in 20% of patients operated on. Despite the multidisciplinary approach in resectable tumors, early tumor recurrences are common. Options on how to select optimal candidates for resection remain limited. Nevertheless, accumulating evidence shows an important role of circulating non-coding plasma and serum microRNAs (miRNAs), which physiologically regulate the function of a target protein. miRNAs also play a crucial role in carcinogenesis. In PDAC patients, the expression levels of certain miRNAs vary and may modulate the function of oncogenes or tumor suppressor genes. As they can be detected in a patient's blood, they have the potential to become promising non-invasive diagnostic and prognostic biomarkers. Moreover, they may also serve as markers of chemoresistance. Thus, miRNAs could be useful for early and accurate diagnosis, prognostic stratification, and individual treatment planning. In this review, we summarize the latest findings on miRNAs in PDAC patients, focusing on their potential use in the early stage of the disease.

microRNA-382 suppresses the progression of pancreatic cancer through the PI3K/Akt signaling pathway by inhibition of Anxa3

Pancreatic cancer (PC) is a lethal cancer in the digestive system. microRNAs (miRNAs) have been demonstrated to participate in PC progression. In this context, we, thus, aimed to explore the mechanism of miR-382 in epithelial mesenchymal transition (EMT) and lymph node metastasis in PC in relation to Anxa3 and the PI3K/Akt signaling pathway. Gene expression data sets GSE16515, GSE71989, and GSE32676 were screened out, with the findings showing the significance of miR-382 and annexin A3 (Anxa3) in PC. A total of 115 PC patients were selected for determination of miR-382 and Anxa3 expression with lowly expressed miR-382 and highly expressed Anxa3 found via RT-quantitative PCR and Western blot analysis. Additionally, negative correlation was found between miR-382 and Anxa3 in PC. Dual-luciferase reporter gene assay and in situ hybridization results confirmed that miR-382 negatively regulated Anxa3. miR-382 targeted Anxa3 and suppressed PC progression by blocking the PI3K/Akt signaling pathway. After a series of gain- and loss-of function approaches, upregulation of miR-382 or silencing of Anxa3 inhibited the EMT and lymph node metastasis, as evidenced by increased level of E-cadherin and decreased level of N-cadherin, vimentin, vascular endothelial growth factor(VEGFR)-3, VEGF-C, and VEGF-D. Overexpression of miR-382 or downregulation of Anxa3 was shown to inhibit colony formation, migration, and invasion abilities of PC cells. Further, tumor xenograft in nude mice in vivo also confirmed the inhibitory role of miR-382 and silenced Anxa3 in lymph node metastasis in PC. Thus, this study provides promising therapeutic targets for PC treatment.NEW & NOTEWORTHY This study focused on the mechanism of miR-382 in epithelial mesenchymal transition and lymph node metastasis in PC in relation to Anxa3 and the PI3K/Akt signaling pathway. We found the inhibitory role of miR-382 in PC in vitro and in vivo.

E-Cadherin in Pancreatic Ductal Adenocarcinoma: A Multifaceted Actor during EMT

Epithelial-to-mesenchymal transition (EMT) is a step-wise process observed in normal and tumor cells leading to a switch from epithelial to mesenchymal phenotype. In tumors, EMT provides cancer cells with a metastatic phenotype characterized by E-cadherin down-regulation, cytoskeleton reorganization, motile and invasive potential. E-cadherin down-regulation is known as a key event during EMT. However, E-cadherin expression can be influenced by the different experimental settings and environmental stimuli so that the paradigm of EMT based on the loss of E-cadherin determining tumor cell behavior and fate often becomes an open question. In this review, we aimed at focusing on some critical points in order to improve the knowledge of the dynamic role of epithelial cells plasticity in EMT and, specifically, address the role of E-cadherin as a marker for the EMT axis.

Silencing of long noncoding RNA LINC00958 prevents tumor initiation of pancreatic cancer by acting as a sponge of microRNA-330-5p to down-regulate PAX8

Pancreatic cancer (PC) represents a relatively rare but severe malignancy worldwide. Accumulated studies have emphasized the potential of long noncoding RNA (lncRNA) as therapeutic strategies for several human cancers. Thus, we aimed to investigate whether a novel non-coding RNA regulatory circuitry involved in PC. Aberrantly expressed lncRNAs and mRNAs were screened out of microarray database. Following the determination of RNA expression, PANC-1 and BxPC-3 PC cells were adopted, after which the expression of miR-330-5p, PAX8 and LINC00958 were subsequently altered. RNA crosstalk was validated by dual-luciferase reporter gene assay. In order to detect whether LINC00958 could act as ceRNA to competitively sponge miR-330-5p and regulate PAX8, subcellular location of LINC00958 and interaction between LINC00958 and miR-330-5p were measured by FISH and RNA pull down respectively. The epithelial mesenchymal transition (EMT) process, cell invasion, and tumor growth were determined in vitro and in vivo. LINC00958 and PAX8 were up-regulated, while miR-330-5p was down-regulated during PC. LINC00958 mainly expressed in the cytoplasm and LINC00958 competitively sponged miR-330-5p. Upregulated miR-330-5p or downregulated PAX8 inhibited the EMT process as well as the invasion and metastasis ability of the PC cells. Moreover, the results indicated that miR-330-5p negatively targeted PAX8, and LINC00958 ultimately showcasing its ability to bind to miR-330-5p through its interaction with AGO2. Therefore, silencing of LINC00958 may bind to miR-330-5p to inhibit PAX8 in a competitive fashion, thereby preventing the progression of PC.

Molecular targets regulating invasion and metastasis of pancreatic cancer

Pancreatic cancer is one of the most malignant tumors of the digestive system. Invasion and metastasis are important biological characteristics of pancreatic cancer and contribute greatly to the poor prognosis of the patients. Many lines of evidence have recently revealed that many molecules, genes and proteins regulate the invasion and metastasis of pancreatic cancer cells. Therefore, exploration and a deep understanding of the molecular mechanism accounting for the invasion and metastasis of pancreatic cancer can help find novel pancreatic cancer biomarkers, improve early diagnosis, develop novel and effective treatment strategies, and predict the prognosis. This review summarizes the latest progress in the research of molecular targets for pancreatic cancer and the mechanisms by which they participate in the invasion and metastasis of this aggressive malignancy.

MicroRNA-488 inhibits progression of colorectal cancer via inhibition of the mitogen-activated protein kinase pathway by targeting claudin-2

Colorectal cancer (CRC) affects people globally, and lymph node metastasis (LNM) is an important indicator of poor clinical outcome in CRC. The current study aims to evaluate the role of microRNA-448 (miR-488) and claudin-2 (CLDN2) in epithelial-mesenchymal transition (EMT) and LNM of CRC through the MAPK signaling pathway. First, microarray analysis indicated that miR-488 was poorly expressed in CRC, whereas CLDN2 was highly expressed. Additionally, the bioinformatics website MicroRNA.org and the dual luciferase reporter gene assay found that CLDN2 was a target gene of miR-488. Next, the results for the correlations between expression of miR-488 and clinicopathological characteristics of CRC indicated that the expression of miR-488 was closely associated with differentiation degree, LNM, and Dukes stages in CRC patients. Moreover, overexpression of miR-488 inhibited the activation of the MAPK signal transduction pathway. Notably, loss- and gain-of-function experiments demonstrated that upregulation of miR-488 suppressed SW480 cell viability, invasion, and migration and promoted apoptosis in SW480 cells. Finally, overexpression of miR-488 inhibited LNM, microlymphatic vessel density, and tumor growth in nude mice. We conclude that overexpression of miR-488 could suppress the cell proliferation, EMT, and LNM of CRC cells via inhibition of the CLDN2-mediated MAPK signaling pathway, which could be a new molecular therapy target for CRC.

Downregulation of circ_008018 protects against cerebral ischemia-reperfusion injury by targeting miR-99a

Circular RNAs (circRNAs) are highly expressed in eukaryotic cells and regulate physiological and pathophysiological processes. However, the role of circRNAs in cerebral ischemia-reperfusion (I/R) injury remains largely unknown. In this study, we found that circ_008018 level was higher in the cortical tissue of mice with middle cerebral artery occlusion as compared to those in the sham group 24 h after reperfusion. Knockdown of circ_008018 attenuated cerebral I/R-induced brain tissue damage and neurological deficits in mice by inducing microRNA miR-99a overexpression. The decreased phosphorylation of Akt and glycogen synthase kinase 3β caused by I/R was partly reversed by circ_008018 silencing or miR-99a overexpression. Taken together, these results provide new insight into the mechanisms of apoptosis resulting from cerebral I/R injury and suggest that targeted inhibition of circ_008018 can protect against subsequent neurological damage.

MiR-30c-5p suppresses migration, invasion and epithelial to mesenchymal transition of gastric cancer via targeting MTA1

BACKGROUND

In China, gastric cancer (GC) is an ordinary malignant tumor. Recent literatures have shown that microRNA is critical during tumorigenesis. This study focuses on the influence of miR-30c-5p on the metastasis of GC and further explores its underlying mechanism.

METHODS

Before the study, expression level of miR-30c-5p and targeted protein was detected in 40 GC tissue samples and 5 GC cells by RT-qPCR. Meanwhile, correlation analysis was conducted between miR-30c-5p expression level and clinicopathological features. In addition, wound healing assay and cell invasion assay were utilized to identify whether miR-30c-5p could affect the migrated and invaded ability of GC cells. Western blotting assay and luciferase assay were used to explore the potential mechanism.

RESULTS

In GC tissues, miR-30c-5p expression level was significantly lower and was remarkably related with clinical features such as tumor node metastasis(TNM) stage and lymphatic metastasis. Moreover, the migrated and invaded ability of GC cells was enhanced through knockdown of miR-30c-5p, while overexpression of miR-30c-5p presented with reversed effect. Further study showed that miR-30c-5p inhibited the expression of its target spot, metastasis-associated protein 1(MTA1), and then suppressed the process of epithelial to mesenchymal transition(EMT) which was important in the metastasis of GC.

CONCLUSION

The results indicate that miR-30c-5p, a novel suppressor in tumorigenesis, could inhibit the metastasis and EMT via MTA1, which may offer a possible therapeutic target in GC.

MicroRNA-375 suppresses esophageal cancer cell growth and invasion by repressing metadherin expression

Accumulating evidence indicates that aberrant expression of microRNAs is involved in tumorigenesis, tumor progression and response to therapy. MicroRNA-375 (miR-375) is an important cancer-associated RNA that is downregulated in multiple types of cancer. In the present study, the potential effects of and underlying molecular mechanism for miR-375 in esophageal cancer were investigated. The expression of miR-375 in paired esophageal squamous cell carcinoma (ESCC) and non-tumor tissues from 10 patients was quantified using the reverse transcription-quantitative polymerase chain reaction. The miR-375 levels in the ESCC cell line EC109 and a normal esophageal epithelial cell line, Het-1A, were also detected. The effect of miR-375 on ESCC cell growth and invasion was determined using Cell Counting kit-8, flow cytometry and invasion assays. A luciferase assay was conducted for target identification. The results of the present study revealed that miR-375 was downregulated in ESCC tumor tissue and EC109 cells compared with normal tissue and Het-1A cells (P<0.01). Overexpression of miR-375 inhibited EC109 cell growth and invasion, and induced cell cycle arrest. In addition, metadherin (MTDH) was demonstrated to be a direct target of miR-375 (P<0.01). The overexpression of miR-375 downregulated MTDH (P<0.01), cyclin D1 (P<0.05) and vascular endothelial growth factor (P<0.01) expression, while upregulating epithelial cadherin (P<0.01) expression, which may account for its effect on ESCC cell proliferation and invasion. The results of the present study suggest that the miR-375/MTDH axis represents a target for the treatment of ESCC.

Cancer-Related Triplets of mRNA-lncRNA-miRNA Revealed by Integrative Network in Uterine Corpus Endometrial Carcinoma

The regulation of transcriptome expression level is a complex process involving multiple-level interactions among molecules such as protein coding RNA (mRNA), long noncoding RNA (lncRNA), and microRNA (miRNA), which are essential for the transcriptome stability and maintenance and regulation of body homeostasis. The availability of multilevel expression data enables a comprehensive view of the regulatory network. In this study, we analyzed the coding and noncoding gene expression profiles of 301 patients with uterine corpus endometrial carcinoma (UCEC). A new method was proposed to construct a genome-wide integrative network based on variance inflation factor (VIF) regression method. The cross-regulation relations of mRNA, lncRNA, and miRNA were then selected based on clique-searching algorithm from the network, when any two molecules of the three were shown as interacting according to the integrative network. Such relation, which we call the mRNA-lncRNA-miRNA triplet, demonstrated the complexity in transcriptome regulation process. Finally, six UCEC-related triplets were selected in which the mRNA participates in endometrial carcinoma pathway, such as CDH1 and TP53. The multi-type RNAs are proved to be cross-regulated as to each of the six triplets according to literature. All the triplets demonstrated the association with the initiation and progression of UCEC. Our method provides a comprehensive strategy for the investigation of transcriptome regulation mechanism.