miR-124, miR-137 and miR-340 regulate colorectal cancer growth via inhibition of the Warburg effect

MicroRNA-122 affects cell aggressiveness and apoptosis by targeting PKM2 in human hepatocellular carcinoma

Human hepatocellular carcinoma (HCC) is a highly invasive tumor with frequent distant metastasis, which is the main cause for the poor prognosis. However, the mechanisms for metastasis remain poorly investigated. MicroRNAs (miRNAs) have been implicated in HCC progression. MicroRNA-122 (miR-122) is considered as a tumor suppressor in human cancer. In the present study, miR-122 expression was found to be significantly lower in HCC than the level in normal tumor-adjacent tissues. miR-122 was clearly silenced or downregulated in five HCC cell lines (HepG2, Hep3B, MHCC97H, Huh7 and SMMC-7721) compared with normal hepatocytes (LO2). HCC patients with low expression of miR-122 had a poor 3-year survival. Univariate analysis and multivariate Cox regression analysis indicated that miR-122 is an independent prognostic factor in HCC. Downregulation of miR-122 promoted proliferation and inhibited apoptosis in Hep3B cells. We found that the public miRNA database (TargetScan) predicted that PKM2 may be a target for miR-122, and the 3'-untranslated region (3'-UTR) of PKM2 contains a highly conserved binding site for miR-122. To identify this, pre-miR-122/anti-miR-122 were respectively transfected into the Hep3B cell line. We found that miR-122 overexpression significantly reduced the level of PKM2. Moreover, knockdown of PKM2 significantly increased miR-122 inhibitor-mediated Hep3B cell apoptosis and reduced miR-122 inhibitor-mediated Hep3B cell migration and invasion. Moreover, re-expression of PKM2 partially abrogated miR-122-induced HCC cell growth arrest and apoptosis in vivo. In conclusion, miR-122 serves as a prognostic biomarker and induces apoptosis and growth arrest by downregulating PKM2 in HCC.

MicroRNA-124 inhibits cancer cell growth through PTB1/PKM1/PKM2 feedback cascade in colorectal cancer

Altered levels and functions of microRNAs (miRs) have been associated with carcinogenesis. In this study, we investigated the role of miR-124 in colorectal adenoma (CRA) and cancer (CRC). The expression levels of miR-124 were decreased in CRA (81.8%) and CRC (57.6%) in 55 clinical samples. The ectopic expression of miR-124 induced apoptosis and autophagy in colon cancer cells. Also, miR-124 targeted polypyrimidine tract-binding protein 1 (PTB1), which is a splicer of pyruvate kinase muscles 1 and 2 (PKM1 and PKM2) and induced the switching of PKM isoform expression from PKM2 to PKM1. Also, siR-PTB1 induced drastic apoptosis in colon cancer cells. Furthermore, we found that the ectopic expression of miR-124 enhanced oxidative stress and the miR-124/PTB1/PKM1/PKM2 axis constituted a feedback cascade. Finally, we showed that intratumor injection of miR-124 and siR-PTB1 induced a tumor-suppressive effect in xenografted mice. The axis was established by both in vitro and in vivo experiments to function in human colorectal cancer cells. These findings suggest that miR-124 acts as a tumor-suppressor and a modulator of energy metabolism through a PTB1/PKM1/PKM2 feedback cascade in human colorectal tumor cells.

MicroRNA-137 suppresses tumor growth in epithelial ovarian cancer in vitro and in vivo

Epithelial ovarian cancer (EOC) remains a major gynecological problem, with a poor 5-year-survival rate due to distant metastases. The identification of microRNAs (miRNAs) may provide a novel avenue for diagnostic and treatment regimens for EOC. Several miRNAs have been reported to be involved in the progression of EOC, among which miRNA (miR)-137 has been observed to be downregulated in the ovarian tissues of patients with EOC. However, the functions of miR-137 in EOC cell apoptosis, migration and invasion remain to be elucidated. In the present study, the expression of miR-137 was measured in clinical ovarian cancer specimens and cell lines using reverse transcription-quantitative polymerase chain reaction. The role of miR-137 in the growth and survival of the SKOV3 human ovarian cancer cell line was determined using several in vitro approaches and in nude mouse models. The results demonstrated that the expression of miR-137 was downregulated in the ovarian cancer specimens and cell lines. It was also observed that enforced expression of miR-137 in the EOC cell lines decreased cell proliferation, clonogenicity, migration and invasion, and induced G1 arrest and cell apoptosis in vitro. Notably, the enforced expression of miR-137 suppressed tumor growth in the nude mice models. These findings suggested that miR-137 may act as a tumor suppressor and be used as a potential therapeutic agent for the treatment of EOC.

miR-340 inhibits glioblastoma cell proliferation by suppressing CDK6, cyclin-D1 and cyclin-D2

Glioblastoma development is often associated with alteration in the activity and expression of cell cycle regulators, such as cyclin-dependent kinases (CKDs) and cyclins, resulting in aberrant cell proliferation. Recent studies have highlighted the pivotal roles of miRNAs in controlling the development and growth of glioblastoma. Here, we provide evidence for a function of miR-340 in the inhibition of glioblastoma cell proliferation. We found that miR-340 is downregulated in human glioblastoma tissue samples and several established glioblastoma cell lines. Proliferation and neurosphere formation assays revealed that miR-340 plays an oncosuppressive role in glioblastoma, and that its ectopic expression causes significant defect in glioblastoma cell growth. Further, using bioinformatics, luciferase assay and western blot, we found that miR-340 specifically targets the 3'UTRs of CDK6, cyclin-D1 and cyclin-D2, leading to the arrest of glioblastoma cells in the G0/G1 cell cycle phase. Confirming these results, we found that re-introducing CDK6, cyclin-D1 or cyclin-D2 expression partially, but significantly, rescues cells from the suppression of cell proliferation and cell cycle arrest mediated by miR-340. Collectively, our results demonstrate that miR-340 plays a tumor-suppressive role in glioblastoma and may be useful as a diagnostic biomarker and/or a therapeutic avenue for glioblastoma.

Pyruvate kinase M2 at a glance

Reprogrammed metabolism is a key feature of cancer cells. The pyruvate kinase M2 (PKM2) isoform, which is commonly upregulated in many human cancers, has been recently shown to play a crucial role in metabolism reprogramming, gene transcription and cell cycle progression. In this Cell Science at a glance article and accompanying poster, we provide a brief overview of recent advances in understanding the mechanisms underlying the regulation of PKM2 expression, enzymatic activity, metabolic functions and subcellular location. We highlight the instrumental role of the non-metabolic functions of PKM2 in tumorigenesis and evaluate the potential to target PKM2 for cancer treatment.

Organ-specific PTB1-associated microRNAs determine expression of pyruvate kinase isoforms

The Warburg effect is a well-known feature of cancer cells. However, its' functional significance hasn't been elucidated yet. Pyruvate kinase muscle (PKM), which is a rate-limiting glycolytic enzyme, has 2 isoforms, PKM1 and PKM2. It has been reported that PKM2 is a tumor-specific isoform and promotes the Warburg effect. Also, it has been thought that tumor cells switch their PKM isoform from PKM1 to PKM2 during tumor development. Here, we showed that this switching machinery was induced only in limited cases, based on PKM expression in normal tissues, and that brain-specific microRNA (miR)-124 and muscle-specific miR-133b regulated this machinery by controlling PKM expression through targeting polypyrimidine tract-binding protein 1 (PTB1), which is a splicer of the PKM gene. Also, we confirmed that the PKM2/PKM1 ratio was further elevated in other PKM2-dominant organs such as colon through the down-regulation of these PTB1-associated microRNAs during tumor development.

A novel miRNA-mediated STOP sign in lung cancer: miR-340 inhibits the proliferation of lung cancer cells through p27(KIP1)

Oncosuppressor miRNAs inhibit cancer cell proliferation by targeting key components of the cell cycle machinery. In our recent report we showed that miR-340 is a novel tumor suppressor in non-small cell lung cancer. miR-340 inhibits neoplastic cell proliferation and induces p27^KIP1 by targeting multiple translational and post-translational regulators of this cyclin-dependent kinase inhibitor.

MicroRNA-124 inhibits proliferation and induces apoptosis by directly repressing EZH2 in gastric cancer

MicroRNA-124 (miR-124), a pivotal member of the p53 network, was found to be down-regulated in multiple types of tumors and further reported as tumor suppressor microRNA. In this study, we found that miR-124 was down-regulated in gastric cancer cell lines and specimens. Restoration of miR-124 expression inhibited the proliferation and colony formation of gastric cancer cells. EZH2 (enhancer of zeste homolog 2), which has been shown to be an important transcription factor involved in the proliferation and metastasis of tumor cells, was here confirmed to be a direct target gene of miR-124. On the other hand, silencing EZH2 also inhibits cell proliferation of gastric cancer cells. Furthermore, the treatment combining miR-124 with 5-fluorouracil (5-FU) significantly showed more efficient anti-tumor effects than single treatment of miR-124 or 5-FU, and over-expression of miR-124 suppresses the tumor growth in vivo. Our study indicate that miR-124 can suppress gastric cancer cell growth by directly targeting the EZH2 gene and sensitize the treatment effect of 5-FU. Therefore, miR-124 shows tumor-suppressive activity and may be a new and useful approach of gastric cancer therapy.

PKM2 contributes to cancer metabolism

Reprogramming of cell metabolism is essential for tumorigenesis, and is regulated by a complex network, in which PKM2 plays a critical role. PKM2 exists as an inactive monomer, less active dimer and active tetramer. While dimeric PKM2 diverts glucose metabolism towards anabolism through aerobic glycolysis, tetrameric PKM2 promotes the flux of glucose-derived carbons for ATP production via oxidative phosphorylation. Equilibrium of the PKM2 dimers and tetramers is critical for tumorigenesis, and is controlled by multiple factors. The PKM2 dimer also promotes aerobic glycolysis by modulating transcriptional regulation. We will discuss the current understanding of PKM2 in regulating cancer metabolism.

SREBP1 regulates tumorigenesis and prognosis of pancreatic cancer through targeting lipid metabolism

Sterol regulatory element-binding protein 1 (SREBP1) is a known transcription factor of lipogenic genes, which plays important roles in regulating de novo lipogenesis. Accumulating evidences indicate SREBP1 is involved in tumorigenesis, yet its role in pancreatic cancer remains unclear. Here, we explored the expression characteristic and function of SREBP1 in pancreatic cancer. Analysis of 60 patients with pancreatic ducat cancer showed that SREBP1 level was significantly higher in pancreatic cancer than that in adjacent normal tissues. High expression of SREBP1 predicted poor prognosis in patients with pancreatic cancer. Multivariate analysis revealed that SREBP1 was an independent factor affecting overall survival. SREBP1 silencing resulted in proliferation inhibition and induction of apoptosis in pancreatic cancer cells. Mechanistically, lipogenic genes (acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase-1 (SCD1)) and de novo lipogenesis were promoted by SREBP1. Inhibition of lipogenic genes through specific inhibitors ablated SREBP1-mediated growth regulation. Furthermore, depletion of SREBP1 could suppress lipid metabolism and tumor growth in vivo. Our results indicate that SREBP1 had important role in tumor progression and appears to be a novel prognostic marker for pancreatic cancer.

c-Met and miRs in Cancer

c-Met, a member of the receptor tyrosine kinase family, is involved in a wide range of cellular processes, including tumor survival, cell growth, angiogenesis and metastasis, and resulting in overexpression in many human cancers, leading to a constitutive activation of the downstream pathways. Recently identified MicroRNAs are a family of small noncoding RNA molecules, extensively studied in cancer, that exert their action by inhibiting gene expression at the posttranscriptional level in several biological processes. Aberrant regulation of microRNAs expression has been implicated in the pathogenesis of different human neoplasia. Several publications point out the connections between c-Met and its ligand hepatocyte growth factor (HGF) and microRNAs. This review summarizes the current knowledge about the interplay between c-Met/HGF and microRNAs and provides evidence that microRNAs are a novel and additional system to regulate c-Met expression in tumors. In the future, microRNAs connected to c-Met may provide an additional option to inhibiting this oncogene from orchestrating an invasive growth program.

Alternative splicing of DNA damage response genes and gastrointestinal cancers

Alternative splicing, which is a common phenomenon in mammalian genomes, is a fundamental process of gene regulation and contributes to great protein diversity. Alternative splicing events not only occur in the normal gene regulation process but are also closely related to certain diseases including cancer. In this review, we briefly demonstrate the concept of alternative splicing and DNA damage and describe the association of alternative splicing and cancer pathogenesis, focusing on the potential relationship of alternative splicing, DNA damage, and gastrointestinal cancers. We will also discuss whether alternative splicing leads to genetic instability, which is considered to be a driving force for tumorigenesis. Better understanding of the role and mechanism of alternative splicing in tumorigenesis may provide new directions for future cancer studies.

Kaposi's sarcoma herpesvirus microRNAs induce metabolic transformation of infected cells

Altered cell metabolism is inherently connected with pathological conditions including cancer and viral infections. Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS). KS tumour cells display features of lymphatic endothelial differentiation and in their vast majority are latently infected with KSHV, while a small number are lytically infected, producing virions. Latently infected cells express only a subset of viral genes, mainly located within the latency-associated region, among them 12 microRNAs. Notably, the metabolic properties of KSHV-infected cells closely resemble the metabolic hallmarks of cancer cells. However, how and why KSHV alters host cell metabolism remains poorly understood. Here, we investigated the effect of KSHV infection on the metabolic profile of primary dermal microvascular lymphatic endothelial cells (LEC) and the functional relevance of this effect. We found that the KSHV microRNAs within the oncogenic cluster collaborate to decrease mitochondria biogenesis and to induce aerobic glycolysis in infected cells. KSHV microRNAs expression decreases oxygen consumption, increase lactate secretion and glucose uptake, stabilize HIF1α and decreases mitochondria copy number. Importantly this metabolic shift is important for latency maintenance and provides a growth advantage. Mechanistically we show that KSHV alters host cell energy metabolism through microRNA-mediated down regulation of EGLN2 and HSPA9. Our data suggest that the KSHV microRNAs induce a metabolic transformation by concurrent regulation of two independent pathways; transcriptional reprograming via HIF1 activation and reduction of mitochondria biogenesis through down regulation of the mitochondrial import machinery. These findings implicate viral microRNAs in the regulation of the cellular metabolism and highlight new potential avenues to inhibit viral latency.

Kaposi's sarcoma (KS) is the most common cancer in HIV-infected untreated individuals. Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of this neoplasm. The discovery of KSHV and its oncogenic enigmas has enlightened many fields of tumor biology and viral oncogenesis. The metabolic properties of KS significantly differ from those of normal cells and resemble cancer cells in general, but the mechanisms employed by KSHV to alter host cell metabolism are poorly understood. Our work demonstrates that KSHV microRNAs can alter cell metabolism through coherent control of independent pathways, a key feature of microRNA-mediated control of cellular functions. This provides a fresh perspective for how microRNA-encoding pathogens shape a cell's metabolism to create an optimal environment for their survival and/or replication. Indeed, we show that, in the case of KSHV, viral microRNA-driven regulation of metabolism is important for viral latency. These findings will evoke new and exciting approaches to prevent KSHV from establishing latency and later on KS.

miR-340 inhibits tumor cell proliferation and induces apoptosis by targeting multiple negative regulators of p27 in non-small cell lung cancer

MicroRNAs (miRNAs) control cell cycle progression by targeting the transcripts encoding for cyclins, CDKs and CDK inhibitors, such as p27^KIP1 (p27). p27 expression is controlled by multiple transcriptional and posttranscriptional mechanisms, including translational inhibition by miR-221/222 and posttranslational regulation by the SCF^SKP2 complex.

The oncosuppressor activity of miR-340 has been recently characterized in breast, colorectal and osteosarcoma tumor cells. However, the mechanisms underlying miR-340-induced cell growth arrest have not been elucidated.

Here we describe miR-340 as a novel tumor suppressor in non-small cell lung cancer (NSCLC). Starting from the observation that the growth-inhibitory and proapoptotic effects of miR-340 correlate with the accumulation of p27 in lung adenocarcinoma and glioblastoma cells, we have analyzed the functional relationship between miR-340 and p27 expression. miR-340 targets three key negative regulators of p27. The miR-340-mediated inhibition of both Pumilio-family RNA-binding proteins (PUM1 and PUM2), required for the miR-221/222 interaction with the p27 3′UTR, antagonizes the miRNA-dependent downregulation of p27. At the same time, miR-340 induces the stabilization of p27 by targeting SKP2, the key posttranslational regulator of p27. Therefore, miR-340 controls p27 at both translational and posttranslational levels. Accordingly, the inhibition of either PUM1 or SKP2 partially recapitulates the miR-340 effect on cell proliferation and apoptosis. In addition to the effect on tumor cell proliferation, miR-340 also inhibits intercellular adhesion and motility in lung cancer cells. These changes correlate with the miR-340-mediated inhibition of previously validated (MET and ROCK1) and potentially novel (RHOA and CDH1) miR-340 target transcripts. Finally, we show that in a small cohort of NSCLC patients (n=23), representative of all four stages of lung cancer, miR-340 expression inversely correlates with clinical staging, thus suggesting that miR-340 downregulation contributes to the disease progression.

MicroRNAs as Mediators of the Ageing Process

Human ageing is a complex and integrated gradual deterioration of cellular processes. There are nine major hallmarks of ageing, that include changes in DNA repair and DNA damage response, telomere shortening, changes in control over the expression and regulation of genes brought about by epigenetic and mRNA processing changes, loss of protein homeostasis, altered nutrient signaling, mitochondrial dysfunction, stem cell exhaustion, premature cellular senescence and altered intracellular communication. Like practically all other cellular processes, genes associated in features of ageing are regulated by miRNAs. In this review, I will outline each of the features of ageing, together with examples of specific miRNAs that have been demonstrated to be involved in each one. This will demonstrate the interconnected nature of the regulation of transcripts involved in human ageing, and the role of miRNAs in this process. Definition of the factors involved in degeneration of organismal, tissue and cellular homeostasis may provide biomarkers for healthy ageing and increase understanding of the processes that underpin the ageing process itself.

MicroRNA-340 as a modulator of RAS-RAF-MAPK signaling in melanoma

microRNA (miRNA)-dependent regulation of gene expression is increasingly linked to development and progression of melanoma. In this study we evaluated the functions of miR-340 in human melanoma cells. Here, we show that miR-340 inhibits the tumorigenic phenotype of melanoma cells. We also found that miR-340 regulates RAS-RAF-Mitogen Activated Protein Kinase (MAPK) signaling by modulating the expression of multiple components of this pathway. Given the importance of MAPK signaling in melanoma, these results provide further insight into the pathogenesis of melanoma.

MicroRNA 340 is involved in UVB-induced dendrite formation through the regulation of RhoA expression in melanocytes

The influence of UV irradiation on pigmentation is well established, but the molecular and cellular mechanisms controlling dendrite formation remain incompletely understood. MicroRNAs (miRNAs) are a class of small RNAs that participate in various cellular processes by suppressing the expression of target mRNAs. In this study, we investigated the expression of miRNAs in response to UVB irradiation using a microarray screen and then identified potential mRNA targets for differentially expressed miRNAs among the genes governing dendrite formation. We subsequently determined the ability of miRNA 340 (miR-340) to suppress the expression of RhoA, which is a predicted miR-340 target gene that regulates dendrite formation. The overexpression of miR-340 promoted dendrite formation and melanosome transport, and the downregulation of miR-340 inhibited UVB-induced dendrite formation and melanosome transport. Moreover, a luciferase reporter assay demonstrated direct targeting of RhoA by miR-340 in the immortalized human melanocyte cell line Pig1. In conclusion, this study has established an miRNA associated with UVB irradiation. The significant downregulation of RhoA protein and mRNA expression after UVB irradiation and the modulation of miR-340 expression suggest a key role for miR-340 in regulating UVB-induced dendrite formation and melanosome transport.

MicroRNAs in colorectal cancer as markers and targets: Recent advances

MicroRNAs are evolutionarily conserved small non-coding RNA molecules encoded by eukaryotic genomic DNA, and function in post-transcriptional regulation of gene expression via base-pairing with complementary sequences in target mRNAs, resulting in translational repression or degradation of target mRNAs. They represent one of the major types of epigenetic modification and play important roles in all aspects of cellular activities. Altered expression of microRNAs has been found in various human diseases including cancer. Many efforts have been made to discover the characteristic microRNA expression profiles, to understand the roles of aberrantly expressed microRNAs and underlying mechanisms in different cancers. With the application of DNA microarray, real-time quantitative polymerase chain reaction and other molecular biology techniques, increasing evidence has been accumulated which reveal that aberrant microRNAs can be detected not only intracellularly within the cancer cells, but also extracellularly in plasma of patients, postulating the potential of aberrant microRNAs as promising diagnostic/prognostic markers and attracting therapeutic targets. This review is intended to provide the most recent advances in microRNA studies in one of the most common cancers, colorectal cancer, especially the identification of those specifically altered microRNAs in colorectal cancer, validation for their relevance to clinical pathological parameters of patients, functional analyses and potential applications of these microRNAs.

The pro-apoptotic role of the regulatory feedback loop between miR-124 and PKM1/HNF4α in colorectal cancer cells

Accumulating evidence indicates that miRNA regulatory circuits play important roles in tumorigenesis. We previously reported that miR-124 is correlated with prognosis of colorectal cancer due to PKM-dependent regulation of glycolysis. However, the mechanism by which miR-124 regulates apoptosis in colorectal cancer remains largely elusive. Here, we show that miR-124 induced significant apoptosis in a panel of colorectal cancer cell lines. The mitochondrial apoptosis pathway was activated by miR-124. Furthermore, the pro-apoptotic role of miR-124 was dependent on the status of PKM1/2 level. PKM1 was required for miR-124-induced apoptosis. Via direct protein-protein interaction, PKM1 promoted HNF4α binding to the promoter region of miR-124 and transcribing miR-124. Moreover, HNF4α or PKM1 had a more dramatic effect on colorectal cancer cell apoptosis in the presence of miR-124. However, inhibition of miR-124 blocked cell apoptosis induced by HNF4α or PKM1. These data indicate that miR-124 not only alters the expression of genes involved in glucose metabolism but also stimulates cancer cell apoptosis. In addition, the positive feedback loop between miR-124 and PKM1/HNF4α plays an important role in colorectal cancer cell apoptosis; it suggests that disrupting this regulatory circuit might be a potential therapeutic tool for colorectal cancer treatment.

Decreased miR-340 expression in bone marrow is associated with liver metastasis of colorectal cancer

Studies have shown the prognostic significance of disseminated tumor cells (DTC) in bone marrow of patients with colorectal cancer. However, the molecular characteristics of DTCs, including their miRNA expression profiles, remain mostly unknown. In this study, we analyzed the miRNA expression of DTCs in bone marrow. EpCAM(+) bone marrow cells were collected using immunomagnetic beads after exclusion of CD14(+) and CD45(+) cells, then subjected to miRNA microarray analysis. Cluster analysis (7 colorectal cancer patients with liver metastasis and 12 colorectal cancer patients without liver metastasis) indicated that miR-340 and miR-542-3p expressions were significantly decreased in EpCAM(+) bone marrow cells of patients with liver metastasis (P = 0.019 and 0.037, respectively). We demonstrated that pre-miR-340 administration inhibited growth of colon cancer cells and suppressed c-Met expression in vitro. In clinical samples of colorectal cancer, miR-340 was expressed at significantly lower levels in tumor tissues compared with normal mucosa. Survival analysis in 136 patients with colorectal cancer indicated that low miR-340 expression was correlated with shorter 5-year disease-free survival (P = 0.023) and poor 5-year overall survival (P = 0.046). It was of note that the colorectal cancer group with low miR-340 and high c-Met expression had the worst prognosis. We further demonstrated that systemic pre-miR-340 administration suppressed growth of pre-established HCT116 tumors in animal therapeutic models. These findings indicate that miR-340 may be useful as a novel prognostic factor and as a therapeutic tool against colorectal cancer. Our data suggest that miR-340 in bone marrow may play an important role in regulating the metastasis cascade of colorectal cancer.

NF-κB target microRNAs and their target genes in TNFα-stimulated HeLa cells

As a transcription factor, NF-κB was demonstrated to regulate the expressions of miRNAs. However, only a few miRNAs have been identified as its targets so far. In this study, by using ChIP-Seq, Genechip and miRNA-Seq techniques, we identified 14 NF-κB target miRNAs in TNFα-stimulated HeLa Cells, including miR-1276, miR-1286, miR-125b-1-3p, miR-219-1-3p, miR-2467-5p, miR-3200-3p, miR-449c-5p, miR-502-5p, miR-548d-5p, miR-30b-3p, miR-3620-5p, miR-340-3p, miR-4454 and miR-4485. Of these miRNAs, 8 detected miRNAs were also NF-κB target misRNAs in TNFα-stimulated HepG2 cells. We also identified 16 target genes of 6 miRNAs including miR-125b-1-3p, miR-1286, miR-502-5p, miR-1276, miR-219-1-3p and miR-30b-3p, in TNFα-stimulated HeLa cells. Target genes of miR-125b-1-3p and miR-1276 were validated in HeLa and HepG2 cells by transfecting their expression plasmids and mimics. Bioinformatic analysis revealed that two potential target genes of miR-1276, BMP2 and CASP9, were enriched in disease phenotypes. The former is enriched in osteoarthritis, and the latter is enriched in Type 2 diabetes and lung cancer, respectively. These findings suggested that this little known miRNA might play roles in these diseases via its two target genes of BMP2 and CASP9. The expression of miR-125b-1 regulated by NF-κB has been reported in diverse cell types under various stimuli, this study found that its expression was also significantly regulated by NF-κB in TNFα-stimulated HeLa and HepG2 cells. Therefore, this miRNA was proposed as a central mediator of NF-κB pathway. These findings provide new insights into the functions of NF-κB in its target miRNA-related biological processes and the mechanisms underlying the regulation of these miRNAs.

Combined microRNA-340 and ROCK1 mRNA profiling predicts tumor progression and prognosis in pediatric osteosarcoma

To investigate the association of combined microRNA-340 (miR-340) and ROCK1 mRNA profiling with clinicopathologic features and prognosis in pediatric patients with osteosarcoma. Quantitative real-time reverse transcriptase-polymerase chain reaction analysis was performed to detect expression levels of miR-340 and ROCK1 mRNA in cancerous and noncancerous bone tissues from 92 children treated for primary osteosarcomas. Compared with noncancerous bone tissues, the expression levels of miR-340 and ROCK1 mRNA were, respectively, downregulated and upregulated in osteosarcoma tissues (both p < 0.001), which was consistent with the results of in situ hybridization and immunohistochemistry analysis. The downregulation of miR-340 was negatively correlated with the upregulation of ROCK1 mRNA in osteosarcoma tissues (r = −0.78, p = 0.001). In addition, the combined miR-340 downregulation and ROCK1 upregulation (miR-340-low/ROCK1-high) occurred more frequently in osteosarcoma tissues with positive metastasis (p < 0.001) and poor response to pre-operative chemotherapy (p = 0.002). Moreover, miR-340-low/ROCK1-high expression was significantly associated with both shortest overall survival (p < 0.001) and progression-free survival (p < 0.001). Multivariate analysis further confirmed that miR-340-low/ROCK1-high expression was an independent prognostic factor of unfavorable survival in pediatric osteosarcoma (for overall survival: p = 0.006, for progression-free survival: p = 0.008). Our data offer convincing evidence, for the first time, that the combined miR-340 downregulation and ROCK1 upregulation may be linked to tumor progression and adverse prognosis in pediatric osteosarcoma.

Dysregulation of miR-124-1 predicts favorable prognosis in acute myeloid leukemia

OBJECTIVE

MicroRNA miR-124 has been suggested as a tumor suppressor for its role in inhibiting cell growth, inducing differentiation and promoting apoptosis. The present study was aimed to investigate the expression status of miR-124-1 and its clinical relevance in patients with acute myeloid leukemia (AML).

DESIGNS AND METHODS

Real-time quantitative PCR was performed to detect the expression level of miR-124-1 in AML patients. The clinical significance of miR-124-1 expression in AML was investigated.

RESULTS

miR-124-1 underexpression was identified in 30 (36%) of 83 AML patients. No significant difference could be observed in sex, age and blood parameters between the patients with and without miR-124-1 underexpression. The frequency of miR-124-1 underexpression was higher in the patients with t(15;17) than in others (62% versus 30%, P = 0.040). The status of miR-124-1 expression was not correlated with the mutations of nine genes (FLT3-ITD, NPM1, C-KIT, IDH1/IDH2, DNMT3A, N/K-RAS and C/EBPA). The patients with miR-124-1 underexpression had borderline longer overall survival and relapse-free survival than those without miR-124-1 underexpression (P = 0.052 and 0.045, respectively).

CONCLUSIONS

These findings suggest that miR-124-1 underexpression is a common event and might have a favorable impact on prognosis in AML.

CHO microRNA engineering is growing up: recent successes and future challenges

microRNAs with their ability to regulate complex pathways that control cellular behavior and phenotype have been proposed as potential targets for cell engineering in the context of optimization of biopharmaceutical production cell lines, specifically of Chinese Hamster Ovary cells. However, until recently, research was limited by a lack of genomic sequence information on this industrially important cell line. With the publication of the genomic sequence and other relevant data sets for CHO cells since 2011, the doors have been opened for an improved understanding of CHO cell physiology and for the development of the necessary tools for novel engineering strategies. In the present review we discuss both knowledge on the regulatory mechanisms of microRNAs obtained from other biological models and proof of concepts already performed on CHO cells, thus providing an outlook of potential applications of microRNA engineering in production cell lines.

miRNAs link metabolic reprogramming to oncogenesis

The most profound biochemical phenotype of cancer cells is their ability to metabolize glucose to lactate, even under aerobic conditions. This alternative metabolic circuitry is sufficient to support the biosynthetic and energy requirements for cancer cell proliferation and metastasis. Alterations in oncogenes and tumor-suppressor genes are involved in the metabolic switch of cancer cells to aerobic glycolysis, increased glutaminolysis, and fatty acid biosynthesis. miRNAs mediate fine-tuning of genes involved directly or indirectly in cancer metabolism. In this review we discuss the regulatory role of miRNAs on enzymes, signaling pathways, and transcription factors involved in glucose and lipid metabolism. We further consider the therapeutic potential of metabolism-related miRNAs in cancer.

Downregulation of miR-124 promotes the growth and invasiveness of glioblastoma cells involving upregulation of PPP1R13L

microRNA-124 (miR-124) plays an important role in regulating growth, invasiveness, stem-like traits, differentiation and apoptosis of glioblastoma cells. PPP1R3L, an inhibitory member of the apoptosis-stimulating protein of p53 family (IASPP), is also able to affect growth, cell cycle progression, metastasis and apoptosis of various types of cancer. To investigate the regulation of PPP1R13L expression by miR-124 and their effects on proliferation, cell cycle transition and invasion in glioblastoma cells, U251 and U373 glioblastoma cells were transfected with miR-124 mimics, its negative control (NC) or an inhibitor. We found that miR-124 was downregulated in glioblastoma tissues, and inversely regulated PPP1R13L expression in U251 and U373 glioblastoma cells. PPP1R13L was found to be a direct target of miR-124 in glioblastoma cells. Overexpression of miR-124 inhibited proliferation, G1/S transition and invasiveness in glioblastoma cells. miR-124 downregulation-mediated malignant progression of glioblastoma was partly attributed to increased PPP1R13L expression. Consequently, our findings provide a molecular basis for the role of miR-124/PPP1R13L in the progression of human glioblastoma and suggest a novel target for the treatment of glioblastoma.

PKM2, a Central Point of Regulation in Cancer Metabolism

Aerobic glycolysis is the dominant metabolic pathway utilized by cancer cells, owing to its ability to divert glucose metabolites from ATP production towards the synthesis of cellular building blocks (nucleotides, amino acids, and lipids) to meet the demands of proliferation. The M2 isoform of pyruvate kinase (PKM2) catalyzes the final and also a rate-limiting reaction in the glycolytic pathway. In the PK family, PKM2 is subjected to a complex regulation by both oncogenes and tumour suppressors, which allows for a fine-tone regulation of PKM2 activity. The less active form of PKM2 drives glucose through the route of aerobic glycolysis, while active PKM2 directs glucose towards oxidative metabolism. Additionally, PKM2 possesses protein tyrosine kinase activity and plays a role in modulating gene expression and thereby contributing to tumorigenesis. We will discuss our current understanding of PKM2's regulation and its many contributions to tumorigenesis.

Targeting cell cycle regulation in cancer therapy

Cell proliferation is an essential mechanism for growth, development and regeneration of eukaryotic organisms; however, it is also the cause of one of the most devastating diseases of our era: cancer. Given the relevance of the processes in which cell proliferation is involved, its regulation is of paramount importance for multicellular organisms. Cell division is orchestrated by a complex network of interactions between proteins, metabolism and microenvironment including several signaling pathways and mechanisms of control aiming to enable cell proliferation only in response to specific stimuli and under adequate conditions. Three main players have been identified in the coordinated variation of the many molecules that play a role in cell cycle: i) The cell cycle protein machinery including cyclin-dependent kinases (CDK)-cyclin complexes and related kinases, ii) The metabolic enzymes and related metabolites and iii) The reactive-oxygen species (ROS) and cellular redox status. The role of these key players and the interaction between oscillatory and non-oscillatory species have proved essential for driving the cell cycle. Moreover, cancer development has been associated to defects in all of them. Here, we provide an overview on the role of CDK-cyclin complexes, metabolic adaptations and oxidative stress in regulating progression through each cell cycle phase and transitions between them. Thus, new approaches for the design of innovative cancer therapies targeting crosstalk between cell cycle simultaneous events are proposed.

The Warburg effect: insights from the past decade

Several decades ago, Otto Warburg discovered that cancer cells produce energy predominantly by glycolysis; a phenomenon now termed "Warburg effect". Warburg linked mitochondrial respiratory defects in cancer cells to aerobic glycolysis; this theory of his gradually lost its importance with the lack of conclusive evidence confirming the presence of mitochondrial defects in cancer cells. Scientists began to believe that this altered mechanism of energy production in cancer cells was more of an effect than the cause. More than 50 years later, the clinical use of FDG-PET imaging in the diagnosis and monitoring of cancers rekindled the interest of the scientific community in Warburg's hypothesis. In the last ten years considerable progress in the field has advanced our understanding of the Warburg effect. However, it still remains unclear if the Warburg effect plays a causal role in cancers or it is an epiphenomenon in tumorigenesis. In this review we aim to discuss the molecular mechanisms associated with the Warburg effect with emphasis on recent advances in the field including the role of epigenetic changes, miRNAs and post-translational modification of proteins. In addition, we also discuss emerging therapeutic strategies that target the dependence of cancer cells on altered energy processing through aerobic glycolysis.