Upregulation of PDK1 associates with poor prognosis in esophageal squamous cell carcinoma with facilitating tumorigenicity in vitro

Circ_0001944 depletion inhibits glycolysis and esophageal cancer progression by binding to miR-338-5p to reduce PDK1 expression

Circular RNA (circRNA) plays multiple roles in the development of esophageal cancer (EC). Herein, we investigate the function of circ_0001944 in EC progression and the related mechanism. Expression of circ_0001944, microRNA-338-5p (miR-338-5p), pyruvate dehydrogenase kinase 1 (PDK1), E-cadherin and N-cadherin was analyzed by quantitative real-time polymerase chain reaction, Western blotting or immunohistochemistry assay. Cell viability, proliferation, apoptosis, invasion and migration were investigated by cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry, transwell invasion and wound-healing assays, respectively. Glucose consumption was detected by Glucose Assay Kit. Lactate production was analyzed by Lactate Assay Kit. ATP/ADP ratio was determined by ADP/ATP ratio Assay Kit. The associations among circ_0001944, miR-338-5p and PDK1 were identified by dual-luciferase reporter and RNA pull-down assays. Xenograft mouse model assay was used to explore the role of circ_0001944 on tumor tumorigenesis in vivo. Circ_0001944 and PDK1 expression were significantly upregulated, while miR-338-5p was downregulated in EC tissues and cells in contrast with normal esophageal tissues and cells. Circ_0001944 knockdown inhibited EC cell proliferation, invasion, migration and glycolysis but induced apoptosis. Meanwhile, circ_0001944 depletion suppressed tumor tumorigenesis in vivo. Mechanistically, circ_0001944 bound to miR-338-5p, and miR-338-5p targeted PDK1. In addition, miR-338-5p inhibitors attenuated circ_0001944 depletion-induced effects in EC cells. The regulation of miR-338-5p on EC progression involved the downregulation of PDK1. Further, circ_0001944 controlled PDK1 expression through miR-338-5p. Circ_0001944 knockdown inhibited EC development and glycolysis by regulating the miR-338-5p/PDK1 pathway, providing a promising target for EC therapy.

Master kinase PDK1 in tumorigenesis

3-phosphoinositide-dependent protein kinase 1 (PDK1) is considered as master kinase regulating AGC kinase family members such as AKT, SGK, PLK, S6K and RSK. Although autophosphorylation regulates PDK1 activity, accumulating evidence suggests that PDK1 is manipulated by many other mechanisms, including S6K-mediated phosphorylation, and the E3 ligase SPOP-mediated ubiquitination and degradation. Dysregulation of these upstream regulators or downstream signals involves in cancer development, as PDK1 regulating cell growth, metastasis, invasion, apoptosis and survival time. Meanwhile, overexpression of PDK1 is also exposed in a plethora of cancers, whereas inhibition of PDK1 reduces cell size and inhibits tumor growth and progression. More importantly, PDK1 also modulates the tumor microenvironments and markedly influences tumor immunotherapies. In summary, we comprehensively summarize the downstream signals, upstream regulators, mouse models, inhibitors, tumor microenvironment and clinical treatments for PDK1, and highlight PDK1 as a potential cancer therapeutic target.

The overview of Mitogen-activated extracellular signal-regulated kinase (MEK)-based dual inhibitor in the treatment of cancers

Mitogen-activated extracellular signal-regulated kinase 1 and 2 (MEK1/2) are the critical components of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MAPK/ERK1/2) signaling pathway which is one of the well-characterized kinase cascades regulating cell proliferation, differentiation, growth, metabolism, survival and mobility both in normal and cancer cells. The aberrant activation of MAPK/ERK1/2 pathway is a hallmark of numerous human cancers, therefore targeting the components of this pathway to inhibit its dysregulation is a promising strategy for cancer treatment. Enormous efforts have been done in the development of MEK1/2 inhibitors and encouraging advancements have been made, including four inhibitors approved for clinical use. However, due to the multifactorial property of cancer and rapidly arising drug resistance, the clinical efficacy of these MEK1/2 inhibitors as monotherapy are far from ideal. Several alternative strategies have been developed to improve the limited clinical efficacy, including the dual inhibitor which is a single drug molecule able to simultaneously inhibit two targets. In this review, we first introduced the activation and function of the MAPK/ERK1/2 components and discussed the advantages of MEK1/2-based dual inhibitors compared with the single inhibitors and combination therapy in the treatment of cancers. Then, we overviewed the MEK1/2-based dual inhibitors for the treatment of cancers and highlighted the theoretical basis of concurrent inhibition of MEK1/2 and other targets for development of these dual inhibitors. Besides, the status and results of these dual inhibitors in both preclinical and clinical studies were also the focus of this review.

Inhibition of PDK1 enhances radiosensitivity and reverses epithelial-mesenchymal transition in nasopharyngeal carcinoma

BACKGROUND

Radioresistance challenges the clinical outcomes of nasopharyngeal carcinoma (NPC). The 3-phosphoinositide-dependent protein kinase 1 (PDK1) is a crucial kinase of PI3K/AKT signaling pathway which has been implicated in the process of radioresistance. However, the role of PDK1 in NPC remains largely unclear.

METHODS

The expression of PDK1 was determined by immunohistochemistry and Western blot. The effects of RNA interference and pharmacologic inhibitor of PDK1 in combination with irradiation were investigated.

RESULTS

Overexpression of PDK1 was correlated with poor prognosis in patients with NPC. PDK1 depletion enhanced radiosensitivity of NPC cells both in vitro and in vivo. Additionally, a specific PDK1 inhibitor also had the potential to enhance radiosensitivity in radioresistant NPC cells. Mechanistically, PDK1 depletion inhibited various targets of AKT including mTOR and GSK-3β and reversed the epithelial-mesenchymal transition.

CONCLUSIONS

These findings indicated that PDK1 might be a potential target for NPC.

PDK1 Inhibitor BX795 Improves Cisplatin and Radio-Efficacy in Oral Squamous Cell Carcinoma by Downregulating the PDK1/CD47/Akt-Mediated Glycolysis Signaling Pathway

Background: Oral squamous cell carcinoma (OSCC) has a high prevalence and predicted global mortality rate of 67.1%, necessitating better therapeutic strategies. Moreover, the recurrence and resistance of OSCC after chemo/radioresistance remains a major bottleneck for its effective treatment. Molecular targeting is one of the new therapeutic approaches to target cancer. Among a plethora of targetable signaling molecules, PDK1 is currently rising as a potential target for cancer therapy. Its aberrant expression in many malignancies is observed associated with glycolytic re-programming and chemo/radioresistance. Methods: Furthermore, to better understand the role of PDK1 in OSCC, we analyzed tissue samples from 62 patients with OSCC for PDK1 expression. Combining in silico and in vitro analysis approaches, we determined the important association between PDK1/CD47/LDHA expression in OSCC. Next, we analyzed the effect of PDK1 expression and its connection with OSCC orosphere generation and maintenance, as well as the effect of the combination of the PDK1 inhibitor BX795, cisplatin and radiotherapy in targeting it. Results: Immunohistochemical analysis revealed that higher PDK1 expression is associated with a poor prognosis in OSCC. The immunoprecipitation assay indicated PDK1/CD47 binding. PDK1 ligation significantly impaired OSCC orosphere formation and downregulated Sox2, Oct4, and CD133 expression. The combination of BX795 and cisplatin markedly reduced in OSCC cell’s epithelial-mesenchymal transition, implying its synergistic effect. p-PDK1, CD47, Akt, PFKP, PDK3 and LDHA protein expression were significantly reduced, with the strongest inhibition in the combination group. Chemo/radiotherapy together with abrogation of PDK1 inhibits the oncogenic (Akt/CD47) and glycolytic (LDHA/PFKP/PDK3) signaling and, enhanced or sensitizes OSCC to the anticancer drug effect through inducing apoptosis and DNA damage together with metabolic reprogramming. Conclusions: Therefore, the results from our current study may serve as a basis for developing new therapeutic strategies against chemo/radioresistant OSCC.

Targeting pyruvate dehydrogenase kinase signaling in the development of effective cancer therapy

Pyruvate is irreversibly decarboxylated to acetyl coenzyme A by mitochondrial pyruvate dehydrogenase complex (PDC). Decarboxylation of pyruvate is considered a crucial step in cell metabolism and energetics. The cancer cells prefer aerobic glycolysis rather than mitochondrial oxidation of pyruvate. This attribute of cancer cells allows them to sustain under indefinite proliferation and growth. Pyruvate dehydrogenase kinases (PDKs) play critical roles in many diseases because they regulate PDC activity. Recent findings suggest an altered metabolism of cancer cells is associated with impaired mitochondrial function due to PDC inhibition. PDKs inhibit the PDC activity via phosphorylation of the E1a subunit and subsequently cause a glycolytic shift. Thus, inhibition of PDK is an attractive strategy in anticancer therapy. This review highlights that PDC/PDK axis could be implicated in cancer's therapeutic management by developing potential small-molecule PDK inhibitors. In recent years, a dramatic increase in the targeting of the PDC/PDK axis for cancer treatment gained an attention from the scientific community. We further discuss breakthrough findings in the PDC-PDK axis. In addition, structural features, functional significance, mechanism of activation, involvement in various human pathologies, and expression of different forms of PDKs (PDK1-4) in different types of cancers are discussed in detail. We further emphasized the gene expression profiling of PDKs in cancer patients to prognosis and therapeutic manifestations. Additionally, inhibition of the PDK/PDC axis by small molecule inhibitors and natural compounds at different clinical evaluation stages has also been discussed comprehensively.

Phosphoinositide-dependent Kinase-1 (PDPK1) regulates serum/glucocorticoid-regulated Kinase 3 (SGK3) for prostate cancer cell survival

Prostate cancer (PCa) is the most common malignancy and is the second leading cause of cancer among men globally. Using a kinome-wide lentiviral small-hairpin RNA (shRNA) library screen, we identified phosphoinositide-dependent kinase-1 (PDPK1) as a potential mediator of cell survival in PCa cells. We showed that knock-down of endogenous human PDPK1 induced significant tumour-specific cell death in PCa cells (DU145 and PC3) but not in the normal prostate epithelial cells (RWPE-1). Further analyses revealed that PDPK1 mediates cancer cell survival predominantly via activation of serum/glucocorticoid-regulated kinase 3 (SGK3). Knock-down of endogenous PDPK1 in DU145 and PC3 cells significantly reduced SGK3 phosphorylation while ectopic expression of a constitutively active SGK3 completely abrogated the apoptosis induced by PDPK1. In contrast, no such effect was observed in SGK1 and AKT phosphorylation following PDPK1 knock-down. Importantly, PDPK1 inhibitors (GSK2334470 and BX-795) significantly reduced tumour-specific cell growth and synergized docetaxel sensitivity in PCa cells. In summary, our results demonstrated that PDPK1 mediates PCa cells' survival through SGK3 signalling and suggest that inactivation of this PDPK1-SGK3 axis may potentially serve as a novel therapeutic intervention for future treatment of PCa.

Sulforaphene induces apoptosis and inhibits the invasion of esophageal cancer cells through MSK2/CREB/Bcl-2 and cadherin pathway in vivo and in vitro

Background

As a novel type of isothiocyanate derived from radish seeds from cruciferous vegetables, sulforaphene (SFE, 4-methylsufinyl-3-butenyl isothiocyanate) has various important biological effects, such as anti-oxidative and anti-bacterial effects. Recently, sulforaphene has attracted increasing attention for its anti-tumor effects and its ability to suppress the development of multiple tumors through different regulatory mechanisms. However, it has not yet been widely investigated for the treatment of esophageal cancer.

Methods

We observed an increased apoptosis in esophageal cancer cells on sulforaphene treatment through flow cytometry (FCM) analysis and transmission electron microscopy (TEM). Through mass spectrometry (MS) analysis, we further detected global changes in the proteomes and phosphoproteomes of esophageal cancer cells on sulforaphene treatment. The molecular mechanism of sulforaphene was verified by western blot,the effect and mechanism of SFE on esophageal cancer was further verified by patient-derived xenograft mouse model.

Results

We identified multiple cellular processes that were changed after sulforaphene treatment by proteomics. We found that sulforaphene could repress the phosphorylation of CREB through MSK2, leading to suppression of Bcl-2 and further promoted cell apoptosis. Additionally, we confirmed that sulforaphene induces tumor cell apoptosis in mice. Interestingly, we also observed the obvious inhibition of cell migration and invasion caused by sulforaphene treatment by inhibiting the expression of cadherin, indicating the complex effects of sulforaphene on the development of esophageal cancer.

Conclusions

Our data demonstrated that sulforaphene induced cell apoptosis and inhibits the invasion of esophageal cancer through a mechanism involving the inhibition of the MSK2–CREB–Bcl2 and cadherin pathway. Sulforaphene could therefore serve as a promising anti-tumor drug for the treatment of esophageal cancer.

Metabolic Flexibility in Cancer: Targeting the Pyruvate Dehydrogenase Kinase:Pyruvate Dehydrogenase Axis

Cancer cells use alterations of normal metabolic processes to sustain proliferation indefinitely. Transcriptional and posttranscriptional control of the pyruvate dehydrogenase kinase (PDK) family is one way in which cancer cells alter normal pyruvate metabolism to fuel proliferation. PDKs can phosphorylate and inactivate the pyruvate dehydrogenase complex (PDHC), which blocks oxidative metabolism of pyruvate by the mitochondria. This process is thought to enhance cancer cell growth by promoting anabolic pathways. Inhibition of PDKs induces cell death through increased PDH activity and subsequent increases in ROS production. The use of PDK inhibitors has seen widespread success as a potential therapeutic in laboratory models of multiple cancers; however, gaps still exist in our understanding of the biology of PDK regulation and function, especially in the context of individual PDKs. Efforts are currently underway to generate PDK-specific inhibitors and delineate the roles of individual PDK isozymes in specific cancers. The goal of this review is to understand the regulation of the PDK isozyme family, their role in cancer proliferation, and how to target this pathway therapeutically to specifically and effectively reduce cancer growth.

Identification of crucial miRNAs and genes in esophageal squamous cell carcinoma by miRNA-mRNA integrated analysis

Esophageal squamous cell carcinoma (ESCC) is a malignancy that severely threatens human health and carries a high incidence rate and a low 5-year survival rate. MicroRNAs (miRNAs) are commonly accepted as a key regulatory function in human cancer, but the potential regulatory mechanisms of miRNA-mRNA related to ESCC remain poorly understood.The GSE55857, GSE43732, and GSE6188 miRNA microarray datasets and the gene expression microarray datasets GSE70409, GSE29001, and GSE20347 were downloaded from Gene Expression Omnibus databases. The differentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) were obtained using GEO2R. Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis for DEGs were performed by Database for Annotation, Visualization and Integrated Discovery (DAVID). A protein-protein interaction (PPI) network and functional modules were established using the STRING database and were visualized by Cytoscape. Kaplan-Meier analysis was constructed based on The Cancer Genome Atlas (TCGA) database.In total, 26 DEMs and 280 DEGs that consisted of 96 upregulated and 184 downregulated genes were screened out. A functional enrichment analysis showed that the DEGs were mainly enriched in the ECM-receptor interaction and cytochrome P450 metabolic pathways. In addition, MMP9, PCNA, TOP2A, MMP1, AURKA, MCM2, IVL, CYP2E1, SPRR3, FOS, FLG, TGM1, and CYP2C9 were considered to be hub genes owing to high degrees in the PPI network. MiR-183-5p was with the highest connectivity target genes in hub genes. FOS was predicted to be a common target gene of the significant DEMs. Hsa-miR-9-3p, hsa-miR-34c-3p and FOS were related to patient prognosis and higher expression of the transcripts were associated with a poor OS in patients with ESCC.Our study revealed the miRNA-mediated hub genes regulatory network as a model for predicting the molecular mechanism of ESCC. This may provide novel insights for unraveling the pathogenesis of ESCC.

9za plays cytotoxic and proapoptotic roles and induces cytoprotective autophagy through the PDK1/Akt/mTOR axis in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) is an aggressive subtype of pulmonary carcinomas with high mortality. However, chemotherapy drug resistance and high recurrence rates hinder the curative effect of platinum-based first-line chemotherapy, which makes it urgent to develop new antitumor drugs for NSCLC. 9za, a new candidate drug synthesized by our research group, has been verified with potent antilung cancer activity in preliminary experiments. However, the underlying molecular mechanism of 9za remains largely vague. This work revealed that 9za could play important cytotoxic and proapoptotic roles in NSCLC cells. Moreover, 9za could induce autophagy and promote autophagy flux. Interestingly, the cytotoxic and proapoptotic roles were significantly dependent on 9za-induced cytoprotective autophagy. That is, the coadministration of 9za with an autophagy inhibitor such as chloroquine or 3-methyladenine exhibited increased cytotoxic and proapoptotic effects compared with 9za treatment alone. In addition, 9za exposure suppressed the phosphorylation of phosphoinositide-dependent protein kinase 1 (PDK1), protein kinase B (Akt), mammalian targets of rapamycin (mTOR), p70 S6 kinase, and 4E binding protein 1 by a dose-dependent way, manifesting that the Akt/mTOR axis was implicated in 9za-induced autophagy. In addition, the overexpression of PDK1 resulted in increased phosphorylation of PDK1 and Akt and blocking of 9za-mediated autophagy. These data showed that the PDK1/Akt/mTOR pathway was involved in 9za-induced autophagy. Hence, this work provides a theoretical basis for exploiting 9za as a new antilung cancer candidate drug and hints that the combination of 9za with an autophagy inhibitor is a feasible alternative approach for the therapy of NSCLC.

The PDK1/c‑Jun pathway activated by TGF‑β induces EMT and promotes proliferation and invasion in human glioblastoma

Glioblastoma multiforme (GBM) is the most common primary malignant tumor affecting the human brain. Despite improvements in therapeutic technologies, patients with GBM have a poor clinical result and the molecular mechanisms responsible for the development of GBM have not yet been fully elucidated. 3-phosphoinositide dependent protein kinase 1 (PDK1) is upregulated in various tumors and promotes tumor invasion. In glioma, transforming growth factor-β (TGF‑β) promotes cell invasion; however, whether TGF‑β directly regulates PDK1 protein and promotes proliferation and invasion is not yet clear. In this study, PDK1 levels were measured in glioma tissues using tissue microarray (TMA) by immunohistochemistry (IHC) and RT‑qPCR. Kaplan-Meier analyses were used to calculate the survival rate of patients with glioma. In vitro, U251 and U87 glioma cell lines were used for functional analyses. Cell proliferation and invasion were analyzed using siRNA transfection, MTT assay, RT‑qPCR, western blot analysis, flow cytometry and invasion assay. In vivo, U251 glioma cell xenografts were established. The results revealed that PDK1 protein was significantly upregulated in glioma tissues compared with non-tumorous tissues. Furthermore, the higher PDK1 levels were associated with a large tumor size (>5.0 cm), a higher WHO grade and a shorter survival of patients with GBM. Univariate and multivariate analyses indicated that PDK1 was an independent prognostic factor. In vivo, PDK1 promoted glioma tumor xenograft growth. In vitro, functional analyses confirmed that TGF‑β upregulated PDK1 protein expression and PDK1 promoted cell migration and invasion, and functioned as an oncogene in GBM, by upregulating c‑Jun protein and inducing epithelial-mesenchymal transition (EMT). c‑Jun protein were overexpressed in glioma tissues and positively correlated with PDK1 levels. Moreover, our findings were further validated by the online Oncomine database. On the whole, the findings of this study indicate that in GBM, PDK1 functions as an oncogene, promoting proliferation and invasion.

MicroRNAs in esophageal squamous cell carcinoma: Potential biomarkers and therapeutic targets

Esophageal cancer is a common cause of cancer-related deaths worldwide. Squamous cell carcinoma (SCC) is the major histological type of esophageal cancer in developing countries including China, and the prognosis is very poor. Many microRNAs are involved in several important biological and pathologic processes, and promote tumorigenesis. To better understand the prognostic and therapeutic roles of microRNAs in ESCC, we reviewed the diagnosis and prognosis associated oncogenic microRNAs (e.g. miR-21 and miR-17-92 cluster) and tumor suppressor microRNAs (e.g. miR-375, miR-133a and miR-133b), and diagnosis and prognosis associated oncogenic target genes (e.g. PDCD4 and CCND1) and tumor suppressor target genes (e.g. EZH2 and PDK1). We also summarized the prognostic microRNA and target gene pairs (e.g. miR-296 and CCND1, miR214 and EZH2). Taken together, our review highlights the opportunities and challenges for microRNAs in the molecular diagnosis and target therapy of ESCC.

Overexpression of the human DEK oncogene reprograms cellular metabolism and promotes glycolysis

The DEK oncogene is overexpressed in many human malignancies including at early tumor stages. Our reported in vitro and in vivo models of squamous cell carcinoma have demonstrated that DEK contributes functionally to cellular and tumor survival and to proliferation. However, the underlying molecular mechanisms remain poorly understood. Based on recent RNA sequencing experiments, DEK expression was necessary for the transcription of several metabolic enzymes involved in anabolic pathways. This identified a possible mechanism whereby DEK may drive cellular metabolism to enable cell proliferation. Functional metabolic Seahorse analysis demonstrated increased baseline and maximum extracellular acidification rates, a readout of glycolysis, in DEK-overexpressing keratinocytes and squamous cell carcinoma cells. DEK overexpression also increased the maximum rate of oxygen consumption and therefore increased the potential for oxidative phosphorylation (OxPhos). To detect small metabolites that participate in glycolysis and the tricarboxylic acid cycle (TCA) that supplies substrate for OxPhos, we carried out NMR-based metabolomics studies. We found that high levels of DEK significantly reprogrammed cellular metabolism and altered the abundances of amino acids, TCA cycle intermediates and the glycolytic end products lactate, alanine and NAD+. Taken together, these data support a scenario whereby overexpression of the human DEK oncogene reprograms keratinocyte metabolism to fulfill energy and macromolecule demands required to enable and sustain cancer cell growth.

Serine/Threonine Kinase 3-Phosphoinositide-Dependent Protein Kinase-1 (PDK1) as a Key Regulator of Cell Migration and Cancer Dissemination

Dissecting the cellular signaling that governs the motility of eukaryotic cells is one of the fundamental tasks of modern cell biology, not only because of the large number of physiological processes in which cell migration is crucial, but even more so because of the pathological ones, in particular tumor invasion and metastasis. Cell migration requires the coordination of at least four major processes: polarization of intracellular signaling, regulation of the actin cytoskeleton and membrane extension, focal adhesion and integrin signaling and contractile forces generation and rear retraction. Among the molecular components involved in the regulation of locomotion, the phosphatidylinositol-3-kinase (PI3K) pathway has been shown to exert fundamental role. A pivotal node of such pathway is represented by the serine/threonine kinase 3-phosphoinositide-dependent protein kinase-1 (PDPK1 or PDK1). PDK1, and the majority of its substrates, belong to the AGC family of kinases (related to cAMP-dependent protein kinase 1, cyclic Guanosine monophosphate-dependent protein kinase and protein kinase C), and control a plethora of cellular processes, downstream either to PI3K or to other pathways, such as RAS GTPase-MAPK (mitogen-activated protein kinase). Interestingly, PDK1 has been demonstrated to be crucial for the regulation of each step of cell migration, by activating several proteins such as protein kinase B/Akt (PKB/Akt), myotonic dystrophy-related CDC42-binding kinases alpha (MRCKα), Rho associated coiled-coil containing protein kinase 1 (ROCK1), phospholipase C gamma 1 (PLCγ1) and β3 integrin. Moreover, PDK1 regulates cancer cell invasion as well, thus representing a possible target to prevent cancer metastasis in human patients. The aim of this review is to summarize the various mechanisms by which PDK1 controls the cell migration process, from cell polarization to actin cytoskeleton and focal adhesion regulation, and finally, to discuss the evidence supporting a role for PDK1 in cancer cell invasion and dissemination.

Will targeting PI3K/Akt/mTOR signaling work in hematopoietic malignancies?

The constitutive activation of phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway has been demonstrated to be critical in clinical cancer patients as well as in laboratory cancer models including hematological malignancies. Great efforts have been made to develop inhibitors targeting this pathway in hematological malignancies but so far the efficacies of these inhibitors were not as good as expected. By analyzing existing literatures and datasets available, we found that mutations of genes in the pathway only constitute a very small subset of hematological malignancies. Deep understanding of the function of gene, the pathway and/or its regulators, and the cellular response to inhibitors, may help us design better drugs targeting the hematological malignancies.

MiR-454 inhibited cell proliferation of human glioblastoma cells by suppressing PDK1 expression

It has been well documented that aberrant expression of microRNAs is associated with carcinogenesis of glioblastoma (GBM), however the underlying mechanisms are not clear. In this present study, we aimed to clarify the biological function of miR-454 in GBM. MiR-454 was identified to be significantly down-regulated in GBM primary tumors and cell lines. Overexpression of miR-454 in GBM cells resulted in arresting cells at G0/G1 phase and thus inhibiting cell proliferation. Bioinformatic analysis predicted 3-phosphoinositide-dependent protein kinase-1 (PDK1) as a target of miR-454 which acted as a tumor promoter gene. Increased miR-454 significantly repressed PDK1 expression, and then regulating cell proliferation and cell cycle regulators, down-regulation of Cyclin D1 and p-pRb and p21 was up-regulated. Taken together, our study has revealed miR-454 as a tumor suppressor in GBM.