[Show abstract][Hide abstract] ABSTRACT: MicroRNAs have added a new dimension to our understanding of tumorigenesis and associated processes like epithelial-to-mesenchymal transition (EMT). Here, we show that miR-375 is elevated in epithelial-like breast cancer cells, and ectopic miR-375 expression suppresses EMT in mesenchymal-like breast cancer cells. We identified short stature homeobox 2 (SHOX2) as a miR-375 target, and miR-375-mediated suppression in EMT was reversed by forced SHOX2 expression. Ectopic SHOX2 expression can induce EMT in epithelial-like breast cancer cells, whereas SHOX2 knockdown diminishes EMT traits in mesenchymal-like breast cancer cells, demonstrating SHOX2 as an EMT inducer. We show that SHOX2 acts as a transcription factor to upregulate transforming growth factor β receptor I (TβR-I) expression, and TβR-I inhibitor LY364947 abolishes EMT elicited by ectopic SHOX2 expression, suggesting that transforming growth factor β signaling is essential for SHOX2-induced EMT. Manipulating SHOX2 abundance in breast cancer cells impact in vitro invasion and in vivo dissemination. Analysis of breast tumor microarray database revealed that high SHOX2 expression significantly correlates with poor patient survival. Our study supports a critical role of SHOX2 in breast tumorigenicity.
Neoplasia (New York, N.Y.) 04/2014; · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRNAs) play key roles in inflammatory responses of macrophages. However, the function of miRNAs in macrophage-derived foam cell formation is unclear. Here, we investigated the role of miRNAs in macrophage-derived foam cell formation and atherosclerotic development.Methods and ResultsUsing quantitative reverse transcription-PCR (qRT-PCR), we found that level of miR-155 expression was increased significantly in both plasma and macrophages from atherosclerosis (ApoE(-/-)) mice. We identified that oxidized LDL (oxLDL) induced the expression and release of miR-155 in macrophages, and that miR-155 was required to mediate oxLDL-induced lipid uptake and reactive oxygen species (ROS) production of macrophages. Further, ectopic overexpression and knockdown experiments identified that HMG box-transcription protein1 (HBP1) is a novel target of miR-155. Knockdown of HBP1 enhanced lipid uptake and ROS production in oxLDL-stimulated macrophages, and overexpression of HBP1 repressed these effects. Furthermore, bioinformatics analysis identified three YY1 binding sites in the promoter region of pri-miR-155 and verified YY1 binding directly to its promoter region. Detailed analysis showed that the YY1/HDAC2/4 complex negatively regulated the expression of miR-155 to suppress oxLDL-induced foam cell formation. Importantly, inhibition of miR-155 by a systemically delivered antagomiR-155 decreased clearly lipid-loading in macrophages and reduced atherosclerotic plaques in ApoE(-/-) mice. Moreover, we observed that the level of miR-155 expression was upregulated in CD14(+) monocytes from patients with coronary heart disease.
Our findings reveal a new regulatory pathway of YY1/HDACs/miR-155/HBP1 in macrophage-derived foam cell formation during early atherogenesis and suggest that miR-155 is a potential therapeutic target for atherosclerosis.
Cardiovascular research 03/2014; · 5.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cell-cell adhesion molecule cadherin-11(CDH11) is preferentially expressed in basal-like breast cancer cells and facilitates breast cancer cell migration by promoting small GTPase Rac activity. However, how the expression of CDH11 is regulated in breast cancer cells is not understood. Here, we show that CDH11 is transcriptionally controlled by homeobox C8 (HOXC8) in human breast cancer cells. HOXC8 serves as a CDH11-specific transcription factor and binds to the site of nucleotides -196 to -191 in the CDH11 promoter. Depletion of HOXC8 leads to the decrease in anchorage-independent cell growth, cell migration/invasion and spontaneous metastasis of breast cancer cells; however, suppressed tumorigenic events were fully rescued by ectopic CDH11 expression in HOXC8-knockdown cells. These results indicate that HOXC8 impacts breast tumorigenesis through CDH11. The analysis of publically available human breast tumor microarray gene expression database demonstrates a strong positive linear association between HOXC8 and CDH11 expression ( = 0.801, p < 0.001). Survival analysis (Kaplan-Meier method, log-rank test) show that both high HOXC8 and CDH11 expression correlate with poor recurrence-free survival rate of patients. Together, our study suggests that HOXC8 promotes breast tumorigenesis by maintaining high level of CDH11 expression in breast cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Increased activation of the serine-glycine biosynthetic pathway is an integral part of cancer metabolism that drives macromolecule synthesis needed for cell proliferation. Whether this pathway is under epigenetic control is unknown. Here we show that the histone H3 lysine 9 (H3K9) methyltransferase G9A is required for maintaining the pathway enzyme genes in an active state marked by H3K9 monomethylation and for the transcriptional activation of this pathway in response to serine deprivation. G9A inactivation depletes serine and its downstream metabolites, triggering cell death with autophagy in cancer cell lines of different tissue origins. Higher G9A expression, which is observed in various cancers and is associated with greater mortality in cancer patients, increases serine production and enhances the proliferation and tumorigenicity of cancer cells. These findings identify a G9A-dependent epigenetic program in the control of cancer metabolism, providing a rationale for G9A inhibition as a therapeutic strategy for cancer.
[Show abstract][Hide abstract] ABSTRACT: Cellular differentiation is characterized by the acquisition of specialized structures and functions, cell cycle exit, and global attenuation of the DNA damage response. It is largely unknown how these diverse cellular events are coordinated at the molecular level during differentiation. We addressed this question in a model system of neuroblastoma cell differentiation induced by HOXC9.
We conducted a genome-wide analysis of the HOXC9-induced neuronal differentiation program. Microarray gene expression profiling revealed that HOXC9-induced differentiation was associated with transcriptional regulation of 2,370 genes, characterized by global upregulation of neuronal genes and downregulation of cell cycle and DNA repair genes. Remarkably, genome-wide mapping by ChIP-seq demonstrated that HOXC9 bound to 40% of these genes, including a large number of genes involved in neuronal differentiation, cell cycle progression and the DNA damage response. Moreover, we showed that HOXC9 interacted with the transcriptional repressor E2F6 and recruited it to the promoters of cell cycle genes for repressing their expression.
Our results demonstrate that HOXC9 coordinates diverse cellular processes associated with differentiation by directly activating and repressing the transcription of distinct sets of genes.
[Show abstract][Hide abstract] ABSTRACT: High abundance of c-Jun is detected in invasive breast cancer cells and aggressive breast tumor malignancies. Here, we demonstrate that a major cause of high c-Jun abundance in invasive breast cancer cells is prolonged c-Jun protein stability owing to poor poly-ubiquitination of c-Jun. Among the known c-Jun-targeting E3 ligases, we identified constitutive photomorphogenesis protein 1 (COP1) as an E3 ligase responsible for c-Jun degradation in less invasive breast cancer cells because depletion of COP1 reduced c-Jun poly-ubiquitination leading to the stabilization of c-Jun protein. In a panel of breast cancer cell lines, we observed an inverse association between the levels of COP1 and c-Jun. However, overexpressing COP1 alone was unable to decrease c-Jun level in invasive breast cancer cells, indicating that efficient c-Jun protein degradation necessitates an additional event. Indeed, we found that glycogen synthase kinase 3 (GSK3) inhibitors elevated c-Jun abundance in less invasive breast cancer cells and that GSK3β nonphosphorylable c-Jun-T239A mutant displayed greater protein stability and poorer poly-ubiquitination compared to the wild-type c-Jun. The ability of simultaneously enforced expression of COP1 and constitutively active GSK3β to decrease c-Jun abundance in invasive breast cancer cells allowed us to conclude that c-Jun is negatively regulated through the coordinated action of COP1 and GSK3β. Importantly, co-expressing COP1 and active GSK3β blocked in vitro cell growth/migration and in vivo metastasis of invasive breast cancer cells. Gene expression profiling of breast tumor specimens further revealed that higher COP1 expression correlated with better recurrence-free survival. Our study supports the notion that COP1 is a suppressor of breast cancer progression.
Neoplasia (New York, N.Y.) 09/2013; 15(9):1075-85. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The importance of microRNAs (miRNAs) in biological and disease processes necessitates a better understanding of the mechanisms that regulate miRNA abundance. We showed that the activities of the mitogen-activated protein kinase (MAPK) p38 and its downstream effector kinase MAPK-activated protein kinase 2 (MK2) were necessary for the efficient processing of a subset of primary miRNAs (pri-miRNAs). Through yeast two-hybrid screening, we identified p68 (also known as DDX5), a key component of the Drosha complex that processes pri-miRNAs, as an MK2-interacting protein, and we found that MK2 phosphorylated p68 at Ser197 in cells. In wild-type mouse embryonic fibroblasts (MEFs) treated with a p38 inhibitor or in MK2-deficient (MK2-/-) MEFs, expression of a phosphomimetic mutant p68 fully restored pri-miRNA processing, suggesting that MK2-mediated phosphorylation of p68 was essential for this process. We found that, whereas p68 was present in the nuclei of wild-type MEFs, it was found mostly in the cytoplasm of MK2-/- MEFs. Nuclear localization of p68 depended on MK2-mediated phosphorylation of Ser197. In addition, inhibition of p38 MAPK promoted the growth of wild-type MEFs and breast cancer MCF7 cells by enhancing the abundance of c-Myc through suppression of the biogenesis of the miRNA miR-145, which targets c-Myc. Because pri-miRNA processing occurs in the nucleus, our findings suggest that the p38 MAPK-MK2 signaling pathway promotes miRNA biogenesis by facilitating the nuclear localization of p68.
[Show abstract][Hide abstract] ABSTRACT: Traditional Chinese medicine (TCM) ZHENG as the key pathological principle is to understand the human homeostasis and guide TCM treatment. Here, circulating microRNAs (miRNAs) were utilized to differentiate between ZHENGs including liver-gallbladder dampness-heat syndrome (LGDHS) and liver-kidney yin deficiency syndrome (LKYDS) in chronic hepatitis B (CHB). Sera samples of CHB patients with LGDHS (n = 35), LKYDS (n = 24), and healthy controls (Ctrls, n = 21) were analyzed by microarray and real-time RT-PCR. Receiver-operator characteristic (ROC) curves were established to evaluate the levels of serum miRNA for discriminating LGDHS and LKYDS. The target genes of miRNAs were predicted by TargetScan. Gene Ontology (GO) and pathways were analyzed using DAVID tool. The results showed that 22 miRNAs were differentially expressed between LGDHS and LKYDS (fold change >2.0 and P < 0.01). Circulating miR-583 and miR-663 were significantly higher (P < 0.001) in CHB patients with LGDHS than those with LKYDS and Ctrls. ROC curve analysis revealed that miR-583 and miR-663 were sensitive and specific enough to distinguish LGDHS from LKYDS. Pathway enrichment analysis indicated that 354 putative targets for miR-583 and 68 putative targets for miR-663 were mainly involved in Axon guidance, Neurotrophin, and MAPK signaling pathway. miR-583 and miR-663 may be potential markers for ZHENG differentiation in CHB.
Evidence-based Complementary and Alternative Medicine 01/2013; 2013:751341. · 1.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Elevated level of urokinase receptor (uPAR) is detected in various aggressive cancer types and is closely associated with poor prognosis of cancers. Binding of uPA to uPAR triggers the conversion of plasminogen to plasmin and the subsequent activation of metalloproteinases. These events confer tumor cells with the capability to degrade the components of the surrounding extracellular matrix, thus contributing to tumor cell invasion and metastasis. uPA-uPAR interaction also elicits signals that stimulate cell proliferation/survival and the expression of tumor-promoting genes, thus assisting tumor development. In addition to its interaction with uPA, uPAR also interacts with vitronectin and this interaction promotes cancer metastasis by activating Rac and stimulating cell migration. Although underlying mechanisms are yet to be fully elucidated, uPAR has been shown to facilitate epithelial-mesenchymal transition (EMT) and induce cancer stem cell-like properties in breast cancer cells. The fact that uPAR lacks intracellular domain suggests that its signaling must be mediated through its co-receptors. Indeed, uPAR interacts with diverse transmembrane proteins including integrins, ENDO180, G protein-coupled receptors and growth factor receptors in cancer cells and these interactions are proven to be critical for the role of uPAR in tumorigenesis. Inhibitory peptide that prevents uPA-uPAR interaction has shown the promise to prolong patients' survival in the early stage of clinical trial. The importance of uPAR's co-receptor in uPAR's tumor-promoting effects implicate that anti-cancer therapeutic agents may also be developed by disrupting the interactions between uPAR and its functional partners.
[Show abstract][Hide abstract] ABSTRACT: In this study we performed a systematic evaluation of functional miRNA-mRNA interactions associated with the invasiveness of breast cancer cells using a combination of integrated miRNA and mRNA expression profiling, bioinformatics prediction, and functional assays. Analysis of the miRNA expression identified 11 miRNAs that were differentially expressed, including 7 down-regulated (miR-200c, miR-205, miR-203, miR-141, miR-34a, miR-183, and miR-375) and 4 up-regulated miRNAs (miR-146a, miR-138, miR-125b1 and miR-100), in invasive cell lines when compared to normal and less invasive cell lines. Transfection of miR-200c, miR-205, and miR-375 mimics into MDA-MB-231 cells led to the inhibition of in vitro cell migration and invasion. The integrated analysis of miRNA and mRNA expression identified 35 known and novel target genes of miR-200c, miR-205, and mir-375, including CFL2, LAMC1, TIMP2, ZEB1, CDH11, PRKCA, PTPRJ, PTPRM, LDHB, and SEC23A. Surprisingly, the majority of these genes (27 genes) were target genes of miR-200c, suggesting that miR-200c plays a pivotal role in regulating the invasiveness of breast cancer cells. We characterized one of the target genes of miR-200c, CFL2, and demonstrated that CFL2 is overexpressed in aggressive breast cancer cell lines and can be significantly down-regulated by exogenous miR-200c. Tissue microarray analysis further revealed that CFL2 expression in primary breast cancer tissue correlated with tumor grade. The results obtained from this study may improve our understanding of the role of these candidate miRNAs and their target genes in relation to breast cancer invasiveness and ultimately lead to the identification of novel biomarkers associated with prognosis.
Journal of Translational Medicine 01/2013; 11:57. · 3.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Xiao Chai Hu Tang (XCHT), a compound formula originally recorded in an ancient Chinese medical book Shanghanlun, has been used to treat chronic liver diseases for a long period of time in China. Although extensive studies have been demonstrated the efficacy of this formula to treat chronic hepatitis, hepatic fibrosis, and hepatocarcinoma, how it works against these diseases still awaits full understanding. Here, we firstly present an overview arranging from the entire formula to mechanism studies of single herb in XCHT and their active components, from a new perspective of "separation study," and we tried our best to both detailedly and systematically organize the antihepatocarcinoma effects of it, hoping that the review will facilitate the strive on elucidating how XCHT elicits its antihepatocarcinoma role.
Evidence-based Complementary and Alternative Medicine 01/2013; 2013:529458. · 1.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Loss of function in either VHL or Nek1 leads to cyst formation in tissues, especially in kidneys. Whether there is a connection between pVHL and Nek1 regulation is unknown. Here, we report that the VHL protein (pVHL) may be a substrate of Nek1. While Nek1 can phosphorylate pVHL at multiple sites, the phosphorylation at serine-168 results in pVHL degradation. Nek1-mediated phosphorylation of pVHL does not significantly affect hypoxia-inducible factors (HIF), a known target of pVHL. However, non-phosphorylable pVHL reconstituted in VHL-deficient cells induces more stable cilia than wild-type VHL during serum stimulation and Nocodazole treatment. The results suggest a possible regulation of pVHL by Nek1 that may contribute to ciliary homeostasis and cystogenesis.
[Show abstract][Hide abstract] ABSTRACT: To investigate whether circulating microRNAs (miRNAs) can serve as molecular markers to predict liver injury resulted from chronic hepatitis B (CHB).
The profiles of serum miRNA expression were first generated with serum samples collected from 10 patients with CHB and 10 healthy donors (Ctrls) by microarray analysis. The levels of several miRNAs were further quantitated by real-time reverse transcription polymerase chain reaction with serum samples from another 24 CHB patients and 24 Ctrls. Serum samples of 20 patients with nonalcohlic steatohepatitis (NASH) were also included for comparison. The comparison in the levels of miRNAs between groups (CHB, NASH and Ctrl) was analyzed with Mann-Whitney U-test. The correlation between miRNAs and clinical pathoparameters was analyzed using Spearman correlation analysis or canonical correlation analysis. The receiver-operator characteristic (ROC) curves were also generated to determine the specificity and sensitivity of each individual miRNA in distinguishing patients with CHB from Ctrls.
miRNA profile analysis showed that 34 miRNAs were differentially expressed between CHB and Ctrl subjects, in which 12 were up-regulated and 22 down-regulated in CHB subject (fold change > 2.0 and P < 0.01). The median levels of miR-122, -572, -575 and -638 were significantly higher (P < 1.00 × 10(-5)) while miR-744 significantly lower (P < 1.00 × 10(-6)) in CHB compared with the Ctrl. The levels of miR-122, -572 and -638 were also higher (P < 1.00 × 10(-3)) while the level of miR-744 lower in CHB (P < 0.05) than in NASH, although the difference between them was not as significant as that between CHB and Ctrl. ROC curve analysis revealed that the levels of miR-122, -572, -575, -638 and -744 in serum were sensitive and specific enough to distinguish CHB, NASH and Ctrl. Multivariate analysis further showed that the levels of these miRNAs were correlated with the liver function parameters. Most significantly, it was the scatter plot of principal component with the levels of these miRNAs, but not the parameters of liver function, which clearly distinguished CHB, NASH and Ctrl subjects.
Serum levels of miR-122, -572, -575, -638 and -744 are deregulated in patients with CHB or NASH. The levels of these miRNAs may serve as potential biomarkers for liver injury caused by CHB and NASH.
World Journal of Gastroenterology 10/2012; 18(37):5188-96. · 2.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cell-cell contact formation following cadherin engagement requires actomyosin contraction along the periphery of cell-cell contact. The molecular mechanisms that regulate myosin activation during this process are not clear. In this paper, we show that two polarity proteins, partitioning defective 3 homologue (Par3) and mammalian homologues of Drosophila Lethal (2) Giant Larvae (Lgl1/2), antagonize each other in modulating myosin II activation during cell-cell contact formation in Madin-Darby canine kidney cells. While overexpression of Lgl1/2 or depletion of endogenous Par3 leads to enhanced myosin II activation, knockdown of Lgl1/2 does the opposite. Intriguingly, altering the counteraction between Par3 and Lgl1/2 induces cell-cell internalization during early cell-cell contact formation, which involves active invasion of the lateral cell-cell contact underneath the apical-junctional complexes and requires activation of the Rho-Rho-associated, coiled-coil containing protein kinase (ROCK)-myosin pathway. This is followed by predominantly nonapoptotic cell-in-cell death of the internalized cells and frequent aneuploidy of the host cells. Such effects are reminiscent of entosis, a recently described process observed when mammary gland epithelial cells were cultured in suspension. We propose that entosis could occur without matrix detachment and that overactivation of myosin or unbalanced myosin activation between contacting cells may be the driving force for entosis in epithelial cells.
Molecular biology of the cell 04/2012; 23(11):2076-91. · 5.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this pre-clinical in vitro study conducted in estrogen receptor positive (ER+) breast cancer cells, we have characterized the effects of insulin-like growth factor I (IGF-1) on the cytostatic and cytotoxic action of antiestrogen treatment when used as a single agent or in combination with the antiprogestin mifepristone (MIF). Our goal was to identify new molecular targets to improve the efficacy of hormonal therapy in breast cancer patients that have a poor response to hormonal therapy, in part, due to high circulating levels of unbound insulinIGF-1.
IGF-1-mediated effects on cytostasis and apoptotic cell death were determined with cell counts conducted in the presence and absence of trypan blue; enzyme-linked immunosorbent assays to determine the intracellular levels of cleaved cytokeratin 18, a marker of epithelial cancer cell apoptosis; and immunoblot analysis to determine the levels of cleaved poly-ADP ribose polymerase (PARP) and lamin A that result from caspase-dependent apoptosis. Cytotoxicity was further characterized by determination of the levels of reactive oxygen species (ROS) and the percent of mitochondrial membrane depolarization in cell populations treated with the different hormones in the presence and absence of IGF-1. Small molecule inhibitors of the dual-specificity protein kinase MEK1, MEK1 siRNA, Bim siRNA, and vectors overexpressing MEK1 wild type and mutant, dominant negative cDNA were used to identify key IGF-1 downstream prosurvival effectors.
IGF-1, at physiologically relevant levels, blocked the cytotoxic action(s) of the antiestrogens 4-hydroxytamoxifen (4-OHT) and tamoxifen (TAM) when used as single agents or in combination with the antiprogestin MIF. The antiapoptotic action of IGF-1 was mediated primarily through the action of MEK1. MEK1 expression reduced the levels of ROS and mitochondrial membrane depolarization induced by the hormonal treatments via a mechanism that involved the phosphorylation and proteasomal turnover of the proapoptotic BH3-only Bcl-2 family member Bim. Importantly, small-molecule inhibitors of MEK1 circumvented the prosurvival action of IGF-1 by restoring Bim to levels that more effectively mediated apoptosis in ER+ breast cancer cells.
his study provides strong support for the use of MEK1 inhibitors in combination with hormonal therapy to effectively affect cytostasis and activate a Bim-dependent apoptotic pathway in ER+ breast cancer cells. We discuss that MEK1 blockade may be a particularly effective treatment for women with high circulating levels of IGF-1, which have been correlated to a poor prognosis.
Breast cancer research: BCR 03/2012; 14(2):R52. · 5.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Retinoic acid (RA) can induce growth arrest and neuronal differentiation of neuroblastoma cells and has been used in clinic for treatment of neuroblastoma. It has been reported that RA induces the expression of several HOXD genes in human neuroblastoma cell lines, but their roles in RA action are largely unknown. The HOXD cluster contains nine genes (HOXD1, HOXD3, HOXD4, and HOXD8-13) that are positioned sequentially from 3' to 5', with HOXD1 at the 3' end and HOXD13 the 5' end. Here we show that all HOXD genes are induced by RA in the human neuroblastoma BE(2)-C cells, with the genes located at the 3' end being activated generally earlier than those positioned more 5' within the cluster. Individual induction of HOXD8, HOXD9, HOXD10 or HOXD12 is sufficient to induce both growth arrest and neuronal differentiation, which is associated with downregulation of cell cycle-promoting genes and upregulation of neuronal differentiation genes. However, induction of other HOXD genes either has no effect (HOXD1) or has partial effects (HOXD3, HOXD4, HOXD11 and HOXD13) on BE(2)-C cell proliferation or differentiation. We further show that knockdown of HOXD8 expression, but not that of HOXD9 expression, significantly inhibits the differentiation-inducing activity of RA. HOXD8 directly activates the transcription of HOXC9, a key effector of RA action in neuroblastoma cells. These findings highlight the distinct functions of HOXD genes in RA induction of neuroblastoma cell differentiation.
PLoS ONE 01/2012; 7(8):e40728. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: AU-rich elements (AREs), residing in the 3' untranslated region (UTR) of many labile mRNAs, are important cis-acting elements that modulate the stability of these mRNAs by collaborating with trans-acting factors such as tristetraprolin (TTP). AREs also regulate translation, but the underlying mechanism is not fully understood. Here we examined the function and mechanism of TTP in ARE-mRNA translation. Through a luciferase-based reporter system, we used knockdown, overexpression, and tethering assays in 293T cells to demonstrate that TTP represses ARE reporter mRNA translation. Polyribosome fractionation experiments showed that TTP shifts target mRNAs to lighter fractions. In murine RAW264.7 macrophages, knocking down TTP produces significantly more tumor necrosis factor alpha (TNF-α) than the control, while the corresponding mRNA level has a marginal change. Furthermore, knockdown of TTP increases the rate of biosynthesis of TNF-α, suggesting that TTP can exert effects at translational levels. Finally, we demonstrate that the general translational repressor RCK may cooperate with TTP to regulate ARE-mRNA translation. Collectively, our studies reveal a novel function of TTP in repressing ARE-mRNA translation and that RCK is a functional partner of TTP in promoting TTP-mediated translational repression.
Molecular and cellular biology 12/2011; 32(5):913-28. · 6.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HOXC8 expression is upregulated in diverse cancer types, and a high level of HOXC8 is often associated with the aggressive/metastatic phenotypes. We previously reported that the presence of HOXC8 is essential for breast cancer cell migration and metastasis. However, the underlying molecular mechanism of HOXC8 regulation of cell migration is unclear. Here, we demonstrate that the presence of HOXC8 is required for cadherin 11 (CDH11) expression in breast cancer cells and that HOXC8 regulation of cell migration is mediated by CDH11. To understand the role of HOXC8-CDH11 axis in cell migration, we show that depleting either HOXC8 or CDH11 diminishes the formation of actin-based membrane ruffles, an event essential for cell migration. The loss of membrane ruffles in HOXC8- or CDH11-knockdown cells is apparently caused by reduced Rac activity because ectopically expressing active Rac1 restores cytoskeleton reorganization. CDH11 physically interacts with Trio, a Rac GEF. We show that Trio is responsible for the majority of endogenous Rac activity in migratory breast cancer cells. Because knockdown of CDH11 prevents the plasma membrane localization of Trio, our study indicates that CDH11 may play a role in recruiting Trio to the plasma membrane where Trio activates Rac, leading to cell migration. This study reveals a novel HOXC8-CDH11-Trio-Rac signaling axis that contributes significantly to breast cancer cell migration.
[Show abstract][Hide abstract] ABSTRACT: Cisplatin is a widely used cancer therapy drug that unfortunately has major side effects in normal tissues, notably nephrotoxicity in kidneys. Despite intensive research, the mechanism of cisplatin-induced nephrotoxicity remains unclear, and renoprotective approaches during cisplatin-based chemotherapy are lacking. Here we have identified PKCδ as a critical regulator of cisplatin nephrotoxicity, which can be effectively targeted for renoprotection during chemotherapy. We showed that early during cisplatin nephrotoxicity, Src interacted with, phosphorylated, and activated PKCδ in mouse kidney lysates. After activation, PKCδ regulated MAPKs, but not p53, to induce renal cell apoptosis. Thus, inhibition of PKCδ pharmacologically or genetically attenuated kidney cell apoptosis and tissue damage, preserving renal function during cisplatin treatment. Conversely, inhibition of PKCδ enhanced cisplatin-induced cell death in multiple cancer cell lines and, remarkably, enhanced the chemotherapeutic effects of cisplatin in several xenograft and syngeneic mouse tumor models while protecting kidneys from nephrotoxicity. Together these results demonstrate a role of PKCδ in cisplatin nephrotoxicity and support targeting PKCδ as an effective strategy for renoprotection during cisplatin-based cancer therapy.
The Journal of clinical investigation 06/2011; 121(7):2709-22. · 15.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the host immune system, the leukocytes are often exposed to multiple pathogens including bacteria and viruses. The principal challenge for the host is to efficiently detect the invading pathogen and mount a rapid defensive response. Leukocytes recognize invading pathogens by directly interacting with pathogen-associated molecular patterns via Toll-like receptors (TLRs) expressed on the leukocyte surfaces. In this study, we provide direct evidence that bacterial LPS enhances the host antiviral response by up-regulating TLR3 expression in human peripheral blood monocytes and monocytic cell lines, THP1 cells. Moreover, LPS induces TLR3 expression via a TLR4-MyD88-IRAK-TRAF6-NF-κB-dependent signaling pathway. Interestingly, CYLD, an important deubiquitinase, acts as a negative regulator of TLR3 induction by LPS. Our study thus provides new insights into a novel role for bacterial infection in enhancing host antiviral response; furthermore, it identifies CYLD for the first time as a critical negative regulator of bacterial LPS-induced response.
International Immunology 06/2011; 23(6):357-64. · 3.14 Impact Factor