MAPK and JNK transduction pathways can phosphorylate Sp1 to activate the uPA minimal promoter element and endogenous gene transcription

SP1 undergoes phase separation and activates RGS20 expression through super-enhancers to promote lung adenocarcinoma progression

Lung adenocarcinoma (LUAD) is the leading cause of cancer-related death worldwide, but the underlying molecular mechanisms remain largely unclear. The transcription factor (TF) specificity protein 1 (SP1) plays a crucial role in the development of various cancers, including LUAD. Recent studies have indicated that master TFs may form phase-separated macromolecular condensates to promote super-enhancer (SE) assembly and oncogene expression. In this study, we demonstrated that SP1 undergoes phase separation and that its zinc finger 3 in the DNA-binding domain is essential for this process. Through Cleavage Under Targets & Release Using Nuclease (CUT&RUN) using antibodies against SP1 and H3K27ac, we found a significant correlation between SP1 enrichment and SE elements, identified the regulator of the G protein signaling 20 (RGS20) gene as the most likely target regulated by SP1 through SE mechanisms, and verified this finding using different approaches. The oncogenic activity of SP1 relies on its phase separation ability and RGS20 gene activation, which can be abolished by glycogen synthase kinase J4 (GSK-J4), a demethylase inhibitor. Together, our findings provide evidence that SP1 regulates its target oncogene expression through phase separation and SE mechanisms, thereby promoting LUAD cell progression. This study also revealed an innovative target for LUAD therapies through intervening in SP1-mediated SE formation.

The Urokinase-Type Plasminogen Activator Contributes to cAMP-Induced Steroidogenesis in MA-10 Leydig Cells

Leydig cells produce androgens which are essential for male sex differentiation and reproductive functions. Steroidogenesis, as well as expression of several genes in Leydig cells, are stimulated by LH/cAMP and repressed by AMP/AMPK. One of those genes is Plau, which codes for the urokinase-type plasminogen activator (uPA), a secreted serine protease. The role of uPA and the regulation of Plau expression in Leydig cells remain unknown. Using siRNA-mediated knockdown, uPA was required for maximal cAMP-induced STAR and steroid hormone production in MA-10 Leydig cells. Analysis of Plau mRNA levels and promoter activity revealed that its expression is strongly induced by cAMP; this induction is blunted by AMPK. The cAMP-responsive region was located, in part, in the proximal Plau promoter that contains a species-conserved GC box at −56 bp. The transcription factor Krüppel-like factor 6 (KLF6) activated the Plau promoter. Mutation of the GC box at −56 bp abolished KLF6-mediated activation and significantly reduced cAMP-induced Plau promoter activity. These data define a role for uPA in Leydig cell steroidogenesis and provide insights into the regulation of Plau gene expression in these cells.

DnaJ-induced TLR7 mediates an increase in interferons through the TLR4-engaged AKT/NF-κB and JNK signaling pathways in macrophages

Toll-like receptor 7 (TLR7) signaling plays pivotal roles in innate immunity by sensing viral single-stranded RNA thereby triggering inflammatory signaling cascades and eliciting protective antiviral responses. In this study, we found that TLR7 expression is highly induced in response to Pseudomonas aeruginosa (P. aeruginosa) infection in a dose- and time-dependent manner. P. aeruginosa-derived DnaJ, a homolog of HSP40, was identified as a related inducing agent for TLR7 expression, and expression of DnaJ was stimulated when host cells were infected with P. aeruginosa. Interestingly, DnaJ was not involved in mediating an increase in the expression levels of TLR3 and TLR8, other well-known antiviral receptors. The induction of TLR7 in response to DnaJ was mediated by the activation of the AKT (Thr308 and Ser473)/NF-κB and p38/JNK MAPKs signaling pathways, consequently transmitting related signals for the expression of interferons (IFNs). Of note, these antiviral responses were regulated, at least in part, by TLR4, which senses the presence of DnaJ and then promotes downstream activation of the AKT (Ser473)/NF-κB and JNK signaling cascades. Taken together, these results suggest that P. aeruginosa-derived DnaJ is sufficient to promote an increase in TLR7 expression in the TLR4-engaged AKT/NF-κB and JNK signaling pathways, thereby promoting an increased antiviral response through the elevated expression of IFNs.

Hepatocyte Mitogen-Activated Protein Kinase Kinase 7 Contributes to Restoration of the Liver Parenchyma Following Injury in Mice

BACKGROUND AND AIMS

Mitogen-activated protein kinase kinase (MKK) 7 and MKK4 are upstream activators of c-Jun NH₂ -terminal kinases (JNKs) and have been shown to be required for the early development of the liver. Although it has been suggested that MKK7 might be involved in the regulation of hepatocyte proliferation, the functional role of MKK7 in the liver has remained unclear.

APPROACH AND RESULTS

Here, we examined phenotypic alterations in liver-specific or hepatocyte/hematopoietic cell-specific MKK7 knockout (KO) mice, which were generated by crossing MKK7^LoxP/LoxP with albumin-cyclization recombination (Alb-Cre) or myxovirus resistance protein 1-Cre mice, respectively. The livers of Alb-Cre^-/+ MKK7^LoxP/LoxP mice developed without discernible tissue disorganization. MKK7 KO mice responded normally to liver injuries incurred by partial hepatectomy or injection of CCl₄ . However, tissue repair following CCl₄ -induced injury was delayed in MKK7 KO mice compared with that of control mice. Furthermore, after repeated injections of CCl₄ for 8 weeks, the liver in MKK7 KO mice showed intense fibrosis with increased protractive hepatocyte proliferation, suggesting that MKK7 deficiency might affect regenerative responses of hepatocytes in the altered tissue microenvironment. MKK7 KO hepatocytes demonstrated normal proliferative activity when cultured in monolayers. However, MKK7 KO significantly suppressed branching morphogenesis of hepatocyte aggregates within a collagen gel matrix. Microarray analyses revealed that suppression of branching morphogenesis in MKK7 KO hepatocytes was associated with a reduction in mRNA expression of transgelin, glioma pathogenesis related 2, and plasminogen activator urokinase-type (Plau); and forced expression of these genes in MKK7 KO hepatocytes partially recovered the attenuated morphogenesis. Furthermore, hepatocyte-specific overexpression of Plau rescued the impaired tissue repair of MKK7 KO mice following CCl₄ -induced injury.

CONCLUSIONS

MKK7 is dispensable for the regenerative proliferation of hepatocytes but plays important roles in repair processes following parenchymal destruction, possibly through modulation of hepatocyte-extracellular matrix interactions.

Moscatilin Inhibits Metastatic Behavior of Human Hepatocellular Carcinoma Cells: A Crucial Role of uPA Suppression via Akt/NF-κB-Dependent Pathway

Hepatocellular carcinoma (HCC) frequently shows early invasion into blood vessels as well as intrahepatic metastasis. Innovations of novel small-molecule agents to block HCC invasion and subsequent metastasis are urgently needed. Moscatilin is a bibenzyl derivative extracted from the stems of a traditional Chinese medicine, orchid Dendrobium loddigesii. Although moscatilin has been reported to suppress tumor angiogenesis and growth, the anti-metastatic property of moscatilin has not been elucidated. The present results revealed that moscatilin inhibited metastatic behavior of HCC cells without cytotoxic fashion in highly invasive human HCC cell lines. Furthermore, moscatilin significantly suppressed the activity of urokinase plasminogen activator (uPA), but not matrix metalloproteinase (MMP)-2 and MMP-9. Interestingly, moscatilin-suppressed uPA activity was through down-regulation the protein level of uPA, and did not impair the uPA receptor and uPA inhibitory molecule (PAI-1) expressions. Meanwhile, the mRNA expression of uPA was inhibited via moscatilin in a concentration-dependent manner. In addition, the expression of phosphorylated Akt, rather than ERK1/2, was inhibited by moscatilin treatment. The expression of phosphor-IκBα, and -p65, as well as κB-luciferase activity were also repressed after moscatilin treatment. Transfection of constitutively active Akt (Myr-Akt) obviously restored the moscatilin-inhibited the activation of NF-κB and uPA, and cancer invasion in HCC cells. Taken together, these results suggest that moscatilin impedes HCC invasion and uPA expression through the Akt/NF-κB signaling pathway. Moscatilin might serve as a potential anti-metastatic agent against the disease progression of human HCC.

Bacterial Lipoproteins Induce BAFF Production via TLR2/MyD88/JNK Signaling Pathways in Dendritic Cells

B-cell activating factor (BAFF) plays a crucial role in survival, differentiation, and antibody secretion of B cells. Microbial products with B-cell mitogenic properties can indirectly promote expansion and activation of B cells by stimulating accessory cells, such as dendritic cells (DCs), to induce BAFF. Although bacterial lipoproteins are potent B-cell mitogen like lipopolysaccharides (LPSs), it is uncertain whether they can stimulate DCs to induce BAFF expression. Here, we evaluated the effect of bacterial lipoproteins on BAFF expression in mouse bone marrow-derived DCs. Lipoprotein-deficient Staphylococcus aureus mutant induced relatively low expression level of membrane-bound BAFF (mBAFF) and the mRNA compared with its wild-type strain, implying that bacterial lipoproteins can positively regulate BAFF induction. The synthetic lipopeptides Pam2CSK4 and Pam3CSK4, which mimic bacterial lipoproteins, dose-dependently induced BAFF expression, and their BAFF-inducing capacities were comparable to those of LPS in DCs. Induction of BAFF by the lipopeptide was higher than the induction by other microbe-associated molecular patterns, including peptidoglycan, flagellin, zymosan, lipoteichoic acid, and poly(I:C). Pam3CSK4 induced both mBAFF and soluble BAFF expression in a dose- and time-dependent manner. BAFF expression by Pam3CSK4 was completely absent in DCs from TLR2- or MyD88-deficient mice. Among various MAP kinase inhibitors, only JNK inhibitors blocked Pam3CSK4-induced BAFF mRNA expression, while inhibitors blocking ERK or p38 kinase had no such effect. Furthermore, Pam3CSK4 increased the DNA-binding activities of NF-κB and Sp1, but not that of C/EBP. Pam3CSK4-induced BAFF promoter activity via TLR2/1 was blocked by NF-κB or Sp1 inhibitor. Collectively, these results suggest that bacterial lipoproteins induce expression of BAFF through TLR2/MyD88/JNK signaling pathways leading to NF-κB and Sp1 activation in DCs, and BAFF derived from bacterial lipoprotein-stimulated DCs induces B-cell proliferation.

Transcriptional regulation of seven cyadox-related genes mainly activated by PI3K and NF-кB signaling pathways in PK-15 cells

Cyadox, a new antibacterial agent as the quinoxaline-1, 4-dioxides, has a good antibacterial and growth-promoting effect, and has the advantages of lower toxicity, adequate safety and faster absorption. Seven differential expressed genes (DEGs) induced by cyadox were screened in swine liver tissues, including Insulin-like Growth Factor-1 (IGF-1), Epidermal Growth Factor (EGF), Poly ADP-ribose polymerase (PARP), the Defender Against Apoptotic Death 1 (DAD1), Complement Component 3 (C3), Transketolase (TK) and cyadox-related novel gene (CRNG). To elucidate the signal mechanism that cyadox altered these genes expression, the time-effect relationship and signaling pathways related to 7 DEGs induced by cyadox were determined in Porcine Kidney-15 (PK-15) cells by RT-qPCR and the application of various signal pathway inhibitors. The phosphorylation levels of signal factors in PK-15 cells were detected by Western blot. The analyses demonstrated that, the mRNA expressions of 7 DEGs were significantly enhanced by cyadox mainly through the phosphoinositide 3-kinase (PI3K) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кB) signaling pathways in PK-15 cells. Furthermore, EGF might be the early response gene of cyadox to activate downstream signaling pathways and regulates the expression of other related genes or directly exerting biological effects. In brief, cyadox mainly regulates the expression of these 7 genes by PI3K and NF-кB signaling pathways to exert it's antibacterial and growth-promoting activity in PK-15 cells.

Tankyrase Inhibitors Target Colorectal Cancer Stem Cells via AXIN-Dependent Downregulation of c-KIT Tyrosine Kinase

Cancer stem cells (CSC) constitute heterogeneous cell subpopulations of a tumor. Although targeting CSCs is important for cancer eradication, no clinically approved drugs that target CSCs have been established. Tankyrase poly(ADP-ribosyl)ates and destabilizes AXIN, a negative regulator of β-catenin, and promotes β-catenin signaling. Here, we report that tankyrase inhibitors downregulate c-KIT tyrosine kinase and inhibit the growth of CD44-positive colorectal CSCs. c-KIT expression in CD44-positive subpopulations of colorectal cancer COLO-320DM cells is associated with their tumor-initiating potential in vivo Tankyrase inhibitors downregulate c-KIT expression in established cell lines, such as COLO-320DM and DLD-1, and colorectal cancer patient-derived cells. These effects of tankyrase inhibitors are caused by reducing the recruitment of SP1 transcription factor to the c-KIT gene promoter and depend on AXIN2 stabilization but not β-catenin downregulation. Whereas c-KIT knockdown inhibits the growth of CD44-positive COLO-320DM cells, c-KIT overexpression in DLD-1 cells confers resistance to tankyrase inhibitors. Combination of a low-dose tankyrase inhibitor and irinotecan significantly inhibited the growth of COLO-320DM tumors in a mouse xenograft model. These observations suggest that tankyrase inhibitors target c-KIT-positive colorectal CSCs and provide a novel therapeutic strategy for cancer.

The mechanism of SP1/p300 complex promotes proliferation of multiple myeloma cells through regulating IQGAP1 transcription

Our previous research had firstly shown that MM cells overexpressed IQGAP1 gene and activated Ras/Raf/MEK/ERK pathway. But the mechanism of IQGAP1 overexpression and IQGAP1 gene transcription regulation remains uncertain. The mechanism of IQGAP1 overexpression and transcriptional regulation of IQGAP1 gene in myeloma cells was explored in the study. Through bioinformatics analysis and prediction we predicted and screened transcription factor Sp1 as a possible upstream regulator of IQGAP1.The proliferation, cell cycle and downstream ERK1/2 and p-ERK1/2 proteins were detected after siRNA-IQGAP1 was transfected to myeloma cells. The expression of Sp1, p300, IQGAP1, p-ERK1/2 and ERK1/2 were detected after Sp1 and p300 were inhibited or overexpressed respectively. The dual-luciferase reporter system was used to detect the activity of IQGAP1 gene promoter. CHIP was used to detect the binding of the Sp1 and IQGAP1 promoter regions.CO-IP was used to explore the interaction between Sp1 and p300.The mRNA expression levels of Sp1,p300 and IQGAP1 of the myeloma patients were detected, and the correlation analysis of their mRNA expression levels were carried out. The results showed IQGAP1-siRNA inhibits cell proliferation, cell cycle, IQGAP1 expression and phosphorylation of ERK1/2 protein. Inhibition of Sp1 or p300 down-regulated ERK1/2 and IQGAP1 expression; overexpression of Sp1 or p300 up-regulated ERK1/2 and IQGAP1 expression; Sp1 and p300 had a positive regulation effect on IQGAP1.Over expression of Sp1 or p300 significantly increased activity of IQGAP1 gene promoter. The transcription factor Sp1 plays a regulatory role in the IQGAP1 promoter region. There is an interaction between Sp1 and p300 in myeloma cells. The mRNA expression levels of Sp1, IQGAP1 and p300 in MM samples showed a positive correlation. In summary IQGAP1 is required for cell proliferation in MM cells, and the transcription of Sp1/p300 complex regulates expression of IQGAP1 gene.

Mannan-binding lectin attenuates acetaminophen-induced hepatotoxicity by regulating CYP2E1 expression via ROS-dependent JNK/SP1 pathway

Mannan-binding lectin (MBL) acts as a soluble pattern recognition molecule in the innate immune system, which is primarily produced by the liver. MBL deficiency occurs with high frequency in the population and is reported to be associated with susceptibility to several liver diseases. In the present study, we investigated the pathophysiological role of MBL in acetaminophen (APAP)-induced hepatotoxicity. After APAP treatment, MBL-deficient (MBL^-/- ) mice had significantly higher mortality and aggravated hepatic necrosis as well as elevated serum lactate dehydrogenase and alanine aminotransferase levels compared to control mice. The enhanced hepatotoxicity in MBL^-/- mice was associated with increased concentration of APAP toxic metabolisms. Furthermore, we demonstrated here that genetic ablation of MBL resulted in excessive reactive oxygen species (ROS) production and enhanced c-Jun N-terminal kinase (JNK) activation, leading to up-regulated specificity protein 1 (SP1) nuclear expression, thus promoted CYP2E1 hepatic expression and consequently exacerbated APAP-induced liver injury in mice. Importantly, we have validated that MBL protected against APAP toxicity in human HepaRG cells in vitro with the same mechanism. Our study revealed an unexpected function of MBL in drug metabolism, thus providing new insight into the drug-induced liver injury in patients with MBL deficiency.

SP1 and STAT3 Functionally Synergize to Induce the RhoU Small GTPase and a Subclass of Non-canonical WNT Responsive Genes Correlating with Poor Prognosis in Breast Cancer

Breast cancer is a heterogeneous disease whose clinical management is very challenging. Although specific molecular features characterize breast cancer subtypes with different prognosis, the identification of specific markers predicting disease outcome within the single subtypes still lags behind. Both the non-canonical Wingless-type MMTV Integration site (WNT) and the Signal Transducer and Activator of Transcription (STAT)3 pathways are often constitutively activated in breast tumors, and both can induce the small GTPase Ras Homolog Family Member U RhoU. Here we show that RhoU transcription can be triggered by both canonical and non-canonical WNT ligands via the activation of c-JUN N-terminal kinase (JNK) and the recruitment of the Specificity Protein 1 (SP1) transcription factor to the RhoU promoter, identifying for the first time SP1 as a JNK-dependent mediator of WNT signaling. RhoU down-regulation by silencing or treatment with JNK, SP1 or STAT3 inhibitors leads to impaired migration and invasion in basal-like MDA-MB-231 and BT-549 cells, suggesting that STAT3 and SP1 can cooperate to induce high RhoU expression and enhance breast cancer cells migration. Moreover, in vivo concomitant binding of STAT3 and SP1 defines a subclass of genes belonging to the non-canonical WNT and the Interleukin (IL)-6/STAT3 pathways and contributing to breast cancer aggressiveness, suggesting the relevance of developing novel targeted therapies combining inhibitors of the STAT3 and WNT pathways or of their downstream mediators.

Ursolic acid facilitates apoptosis in rheumatoid arthritis synovial fibroblasts by inducing SP1-mediated Noxa expression and proteasomal degradation of Mcl-1

Rheumatoid arthritis (RA) is characterized by hyperplastic pannus formation mediated by activated synovial fibroblasts (RASFs) that cause joint destruction. We have shown earlier that RASFs exhibit resistance to apoptosis, primarily as a result of enhanced expression of myeloid cell leukemia-1 (Mcl-1). In this study, we discovered that ursolic acid (UA), a plant-derived pentacyclic triterpenoid, selectively induces B-cell lymphoma 2 homology 3-only protein Noxa in human RASFs. We observed that UA-induced Noxa expression was followed by a consequent decrease in Mcl-1 expression in a dose-dependent manner. Subsequent evaluation of the signaling pathways showed that UA-induced Noxa is primarily mediated by the JNK pathway in human RASFs. Chromatin immunoprecipitation (IP) studies into the promoter region of Noxa indicated the role of transcription factor specificity protein 1 in JNK-mediated Noxa expression. Furthermore, the results from IP studies and proximity ligation assays indicated that UA-induced Noxa colocalizes and associates with Mcl-1 to prime it for proteasomal degradation through K48-linked ubiquitination by the selective recruitment of Mcl-1 ubiquitin ligase E3, a homologous to E6-associated protein C terminus domain-containing E3 ubiquitin ligase. These findings unveil a novel mechanism of inducing apoptosis in RASFs and a potential adjunct therapeutic strategy of regulating synovial hyperplasia in RA.-Kim, E. Y., Sudini, K., Singh, A. K., Haque, M., Leaman, D., Khuder, S., Ahmed, S. Ursolic acid facilitates apoptosis in rheumatoid arthritis synovial fibroblasts by inducing SP1-mediated Noxa expression and proteasomal degradation of Mcl-1.

Multifaceted Role of the Urokinase-Type Plasminogen Activator (uPA) and Its Receptor (uPAR): Diagnostic, Prognostic, and Therapeutic Applications

The plasminogen activator (PA) system is an extracellular proteolytic enzyme system associated with various physiological and pathophysiological processes. A large body of evidence support that among the various components of the PA system, urokinase-type plasminogen activator (uPA), its receptor (uPAR), and plasminogen activator inhibitor-1 and -2 (PAI-1 and PAI-2) play a major role in tumor progression and metastasis. The binding of uPA with uPAR is instrumental for the activation of plasminogen to plasmin, which in turn initiates a series of proteolytic cascade to degrade the components of the extracellular matrix, and thereby, cause tumor cell migration from the primary site of origin to a distant secondary organ. The components of the PA system show altered expression patterns in several common malignancies, which have identified them as ideal diagnostic, prognostic, and therapeutic targets to reduce cancer-associated morbidity and mortality. This review summarizes the various components of the PA system and focuses on the role of uPA-uPAR in different biological processes especially in the context of malignancy. We also discuss the current state of knowledge of uPA-uPAR-targeted diagnostic and therapeutic strategies for various malignancies.

Dihydroartemisinin induced caspase-dependent apoptosis through inhibiting the specificity protein 1 pathway in hepatocellular carcinoma SK-Hep-1 cells

AIMS

Dihydroartemisinin (DHA) is a semi-synthetic derivative of artemisinin, well known for a safe and effective first-line antimalarial agent. This study investigated whether and how DHA induces apoptosis focusing on the specificity protein 1 (Sp1) pathway in hepatocellular carcinoma (HCC) SK-Hep-1 cells.

MAIN METHODS

The cell viability was evaluated by MTT assay. Cell cycle analysis was performed after PI staining by flow cytometry system. Apoptosis was confirmed by DAPI staining and by detecting cytoplasmic histone-associated-DNA-fragments using a cell death detection ELISAPLUS kit. The expression of proteins involved in apoptosis was evaluated by Western blot. The nuclear localization of Sp1 was evaluated by immunofluorescence assay.

KEY FINDINGS

DHA exerted potent cytotoxicity against HCC SK-Hep-1 cells compared with normal hepatocyte AML12 cells. The sub-G1 DNA content and apoptosis index were increased by DHA, which was accompanied by nuclei condensation and fragmentation. DHA activated caspase 3, caspase 8, and caspase 9 and cleaved poly (ADP-ribose) polymerase (PARP). DHA-induced apoptotic cell death, activation of caspases and cleavage of PARP were dramatically inhibited by pan caspase inhibitor Z-VAD-FMK. DHA down-regulated protein expression and nuclear localization of Sp1, which in turn decreased Sp1 downstream target protein, X-linked inhibitor of apoptosis. Decreased Sp1 protein expression by DHA was restored by proteasome inhibitor MG132. DHA led to a down-regulation of phospho-ERK, -p38 and -JNK without affecting their total forms.

SIGNIFICANCE

These results demonstrate that DHA induces caspase-dependent apoptosis in HCC SK-Hep-1 cells by proteasome-dependent degradation of Sp1, which is involved in mitogen-activate protein kinase pathway.

Ezrin mediates both HGF/Met autocrine and non-autocrine signaling-induced metastasis in melanoma

Aberrant HGF/Met signaling promotes tumor migration, invasion, and metastasis through both autocrine and non-autocrine mechanisms; however, the molecular downstream signaling mechanisms by which HGF/Met induces metastasis are incompletely understood. We here report that Ezrin expression is stimulated by HGF and correlates with activated HGF/Met, indicating that HGF/Met signaling regulates the expression of Ezrin. We show that HGF/Met signaling activates the transcription factor Sp1 through the MAPK pathway, and activated Sp1 can in turn directly bind to the promoter of Ezrin gene and regulate its transcription. Notably, knockdown of Ezrin expression by shRNAs inhibits the metastasis induced by either HGF/Met autocrine or non-autocrine signaling in syngeneic wildtype and HGF transgenic mouse hosts. We also used small molecule drugs in preclinical mouse models to confirm that Ezrin is one of the downstream molecules mediating HGF/Met signaling-induced metastasis in melanoma. We conclude that Ezrin is a key downstream factor involved in the regulation of HGF/Met signaling-induced metastasis and demonstrate a link between Ezrin and HGF/Met/MAPK/Sp1 activation in the metastatic process. Our data indicate that Ezrin represents a promising therapeutic target for patients bearing tumors with activated HGF/Met signaling.

RhoGDIβ promotes Sp1/MMP-2 expression and bladder cancer invasion through perturbing miR-200c-targeted JNK2 protein translation

Our most recent studies demonstrate that RhoGDIβ is able to promote human bladder cancer (BC) invasion and metastasis in an X‐link inhibitor of apoptosis protein‐dependent fashion accompanied by increased levels of matrix metalloproteinase (MMP)‐2 protein expression. We also found that RhoGDIβ and MMP‐2 protein expressions are consistently upregulated in both invasive BC tissues and cell lines. In the present study, we show that knockdown of RhoGDIβ inhibited MMP‐2 protein expression accompanied by a reduction of invasion in human BC cells, whereas ectopic expression of RhoGDIβ upregulated MMP‐2 protein expression and promoted invasion as well. The mechanistic studies indicated that MMP‐2 was upregulated by RhoGDIβ at the transcriptional level by increased specific binding of the transcription factor Sp1 to the mmp‐2 promoter region. Further investigation revealed that RhoGDIβ overexpression led to downregulation of miR‐200c, whereas miR‐200c was able directly to target 3′‐UTR of jnk2mRNA and attenuated JNK2 protein translation, which resulted in attenuation of Sp1mRNA and protein expression in turn, inhibiting Sp1‐dependent mmp‐2 transcription. Collectively, our studies demonstrate that RhoGDIβ overexpression inhibits miR‐200c abundance, which consequently results in increases of JNK2 protein translation, Sp1 expression, mmp‐2 transcription, and BC invasion. These findings, together with our previous results showing X‐link inhibitor of apoptosis protein mediating mRNA stabilization of both RhoGDIβ and mmp‐2, reveal the nature of the MMP‐2 regulatory network, which leads to MMP‐2 overexpression and BC invasion.

MiR-181b modulates EGFR-dependent VCAM-1 expression and monocyte adhesion in glioblastoma

Tumor-associated macrophages (TAMs) originate as circulating monocytes, and are recruited to gliomas, where they facilitate tumor growth and migration. Understanding the interaction between TAM and cancer cells may identify therapeutic targets for glioblastoma multiforme (GBM). Vascular cell adhesion molecule-1 (VCAM-1) is a cytokine-induced adhesion molecule expressed on the surface of cancer cells, which is involved in interactions with immune cells. Analysis of the glioma patient database and tissue immunohistochemistry showed that VCAM-1 expression correlated with the clinico-pathological grade of gliomas. Here, we found that VCAM-1 expression correlated positively with monocyte adhesion to GBM, and knockdown of VCAM-1 abolished the enhancement of monocyte adhesion. Importantly, upregulation of VCAM-1 is dependent on epidermal-growth-factor-receptor (EGFR) expression, and inhibition of EGFR effectively reduced VCAM-1 expression and monocyte adhesion activity. Moreover, GBM possessing higher EGFR levels (U251 cells) had higher VCAM-1 levels compared to GBMs with lower levels of EGFR (GL261 cells). Using two- and three-dimensional cultures, we found that monocyte adhesion to GBM occurs via integrin α4β1, which promotes tumor growth and invasion activity. Increased proliferation and tumor necrosis factor-α and IFN-γ levels were also observed in the adherent monocytes. Using a genetic modification approach, we demonstrated that VCAM-1 expression and monocyte adhesion were regulated by the miR-181 family, and lower levels of miR-181b correlated with high-grade glioma patients. Our results also demonstrated that miR-181b/protein phosphatase 2A-modulated SP-1 de-phosphorylation, which mediated the EGFR-dependent VCAM-1 expression and monocyte adhesion to GBM. We also found that the EGFR-dependent VCAM-1 expression is mediated by the p38/STAT3 signaling pathway. Our study suggested that VCAM-1 is a critical modulator of EGFR-dependent interaction of monocytes with GBM, which raises the possibility of developing effective and improved therapies for GBM.

Dietary restriction protects against diethylnitrosamine-induced hepatocellular tumorigenesis by restoring the disturbed gene expression profile

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent malignancies, worse still, there are very limited therapeutic measures with poor clinical outcomes. Dietary restriction (DR) has been known to inhibit spontaneous and induced tumors in several species, but the mechanisms are little known. In the current study, by using a diethylnitrosamine (DEN)-induced HCC mice model, we found that DR significantly reduced the hepatic tumor number and size, delayed tumor development, suppressed proliferation and promoted apoptosis. Further transcriptome sequencing of liver tissues from the DEN and the DEN accompanied with DR (DEN+DR) mice showed that DEN induced profound changes in the gene expression profile, especially in cancer-related pathways while DR treatment reversed most of the disturbed gene expression induced by DEN. Finally, transcription factor enrichment analysis uncovered the transcription factor specificity protein 1 (SP1) probably functioned as the main regulator of gene changes, orchestrating the protective effects of DR on DEN induced HCC. Taken together, by the first comprehensive transcriptome analysis, we elucidate that DR protects aginst DEN-induced HCC by restoring the disturbed gene expression profile, which holds the promise to provide effective molecular targets for cancer therapies.

Netrin-1-Induced Stem Cell Bioactivity Contributes to the Regeneration of Injured Tissues via the Lipid Raft-Dependent Integrin α6β4 Signaling Pathway

Netrin-1 (Ntn-1) is a multifunctional neuronal signaling molecule; however, its physiological significance, which improves the tissue-regeneration capacity of stem cells, has not been characterized. In the present study, we investigate the mechanism by which Ntn-1 promotes the proliferation of hUCB-MSCs with regard to the regeneration of injured tissues. We found that Ntn-1 induces the proliferation of hUCB-MSCs mainly via Inα6β4 coupled with c-Src. Ntn-1 induced the recruitment of NADPH oxidases and Rac1 into membrane lipid rafts to facilitate ROS production. The Inα6β4 signaling of Ntn-1 through ROS production is uniquely mediated by the activation of SP1 for cell cycle progression and the transcriptional occupancy of SP1 on the VEGF promoter. Moreover, Ntn-1 has the ability to induce the F-actin reorganization of hUCB-MSCs via the Inα6β4 signaling pathway. In an in vivo model, transplantation of hUCB-MSCs pre-treated with Ntn-1 enhanced the skin wound healing process, where relatively more angiogenesis was detected. The potential effect of Ntn-1 on angiogenesis is further verified by the mouse hindlimb ischemia model, where the pre-activation of hUCB-MSCs with Ntn-1 significantly improved vascular regeneration. These results demonstrate that Ntn-1 plays an important role in the tissue regeneration process of hUCB-MSC via the lipid raft-mediated Inα6β4 signaling pathway.

PP2A inhibitors arrest G2/M transition through JNK/Sp1- dependent down-regulation of CDK1 and autophagy-dependent up-regulation of p21

Protein phosphatase 2A (PP2A) plays an important role in the control of the cell cycle. We previously reported that the PP2A inhibitors, cantharidin and okadaic acid (OA), efficiently repressed the growth of cancer cells. In the present study, we found that PP2A inhibitors arrested the cell cycle at the G2 phase through a mechanism that was dependent on the JNK pathway. Microarrays further showed that PP2A inhibitors induced expression changes in multiple genes that participate in cell cycle transition. To verify whether these expression changes were executed in a PP2A-dependent manner, we targeted the PP2A catalytic subunit (PP2Ac) using siRNA and evaluated gene expression with a microarray. After the cross comparison of these microarray data, we identified that CDK1 was potentially the same target when treated with either PP2A inhibitors or PP2Ac siRNA. In addition, we found that the down-regulation of CDK1 occurred in a JNK-dependent manner. Luciferase reporter gene assays demonstrated that repression of the transcription of CDK1 was executed through the JNK-dependent activation of the Sp1 transcription factor. By constructing deletion mutants of the CDK1 promoter and by using ChIP assays, we identified an element in the CDK1 promoter that responded to the JNK/Sp1 pathway after stimulation with PP2A inhibitors. Cantharidin and OA also up-regulated the expression of p21, an inhibitor of CDK1, via autophagy rather than PP2A/JNK pathway. Thus, this present study found that the PP2A/JNK/Sp1/CDK1 pathway and the autophagy/p21 pathway participated in G2/M cell cycle arrest triggered by PP2A inhibitors.

Thrombosis recanalization by paeoniflorin through the upregulation of urokinase‑type plasminogen activator via the MAPK signaling pathway

Paeoniflorin, the major component of Paeonia lactiflora pall, has previously been reported to prevent thrombosis. Plasminogen activator urokinase (uPA) is a serine protease that markedly facilitates normal thrombosis resolution. Paeoniflorin and uPA have been linked to the mitogen-activated protein kinase (MAPK) signaling pathway. In the current study, the influence of paeoniflorin on the expression of uPA was investigated and the underlying regulatory mechanism was preliminarily determined. The prothrombotic state of the model animals treated with paeoniflorin were assessed by enzyme-linked immunosorbent assay (ELISA). Additionally, the cytotoxicity of paeoniflorin on human umbilical vein endothelial cell (HUVEC) cultures was estimated using a methyl thiazolyl tetrazolium assay and the possible pathways involved in the interaction between paeoniflorin and uPA were evaluated using western blot analysis. The ELISA results demonstrated that the levels of 6-keto prostaglandin F_1a, fibronectin and uPA were significantly upregulated by treatment with paeoniflorin compared with control (P<0.05). By contrast, the expression of fibrinogen, D-dimer and thromboxane B₂ were inhibited. With an increase in the concentration of paeoniflorin the cell viability of HUVECs decreased gradually. The results of western blot analysis demonstrated that paeoniflorin increased the phosphorylation of MAPK 14 (p38) and MAPK 8 (JNK). The present study demonstrated that paeoniflorin has the potential to improve the prethrombotic state and recanalize thrombosis by increasing the expression of uPA, which may be mediated via regulation of the p38 and JNK MAPK signaling pathways. However, this treatment effect was dependent on the concentration of paeoniflorin used, an unsuitable concentration of the agent would result in a negative effect on the anti-thrombosis pathways.

Docosahexaenoic Acid Downregulates EGF-Induced Urokinase Plasminogen Activator and Matrix Metalloproteinase 9 Expression by Inactivating EGFR/ErbB2 Signaling in SK-BR3 Breast Cancer Cells

Urokinase plasminogen activator (uPA) and matrix metalloproteinase 9 (MMP-9) play crucial roles in tumor metastasis. Despite the well-known anticancer role of docosa-hexaenoic acid (DHA), its specific effect on ErbB2-mediated breast cancer metastasis is not fully clarified. In this study, we investigated the effect of DHA on epidermal growth factor (EGF)-induced uPA and MMP-9 activity, expression and cell invasion in SK-BR3 breast cancer cells and the possible mechanisms involved. The results showed that EGF (40 ng/ml) induced uPA and MMP-9 mRNA and protein expression, enzyme activity, and 100 μM DHA significantly inhibited EGF-induced uPA and MMP-9 mRNA, protein expression, enzyme activity, cell migration, and cell invasion. EGF increased protein expression and phosphorylation of EGF receptor (EGFR) and ErbB2 as well as of JNK2, ERK1/2, and Akt, and these changes were attenuated by DHA pretreatment. AG1478, an inhibitor of EGFR, also attenuated EGF-induced activation of EGFR, JNK2, ERK1/2, and Akt. Knocked down ErbB2 expression resulted in a similar inhibition of uPA and MMP-9 expression as noted by DHA and AG1478. Taken together, these results suggest that suppression of EGF-induced metastasis by DHA is likely through an inhibition of EGFR and ErbB2 protein expression and the downstream target uPA and MMP-9 activation in SK-BR3 human breast cancer cells.

Estrogen receptor-α drives adiponectin effects on cyclin D1 expression in breast cancer cells

Obesity is a risk factor for breast cancer, largely due to altered expression of various adipocytokines. As it concerns adiponectin, there are not univocal results regarding its role in breast cancer occurrence and progression. Here, we demonstrate that in animals injected with human estrogen receptor (ER)-α-negative MDA-MB-231 cells pretreated with adiponectin (1 and 5 µg/ml), a significant reduction (60 and 40%, respectively) in tumor volume is observed, whereas an increased tumor growth (54 and 109%, respectively) is evidenced in the animals receiving human ER-α-positive MCF-7 cells. Moreover, cyclin D1 (CD1) mRNA and protein levels are decreased in MDA-MB-231 cells, whereas they are up-regulated in ER-α-positive cells by adiponectin. These findings fit with the opposite effects of adiponectin on CD1 promoter: 0.44- and 0.34-fold decrease in MDA-MB-231 cells and 0.63- and 0.95-fold increase in MCF-7 cells, treated with 1 and 5 µg/ml, respectively. Functional studies indicate that these effects are mediated by the specific protein 1 motif located in the CD1 promoter. In the absence of ER-α, the adiponectin-mediated down-regulation of CD1 involves the recruitment of corepressors. In the presence of ER-α, the adiponectin-induced expression of CD1 requires the involvement of an activator complex. In conclusion, we propose that a possible mechanism through which adiponectin differently affects breast cancer growth is the opposite modulation of CD1 levels accordingly to ER-α expression.

Map kinase and PKC signaling pathways modulate NGF-mediated apoE transcription

The present study assessed the mechanisms by which nerve growth factor (NGF) increased the level of apolipoprotein E (apoE) in PC12 cells. NGF (50ng/mL) significantly increased apoE protein levels following 72h of treatment. Similarly NGF increased luciferase activity in cells transfected with a luciferase reporter construct containing a 500bp fragment of the apoE promoter, indicating NGF-induced apoE expression is regulated, at least in part, at the level of transcription. The non-selective nitric oxide synthase (NOS) inhibitor N(ɷ)-nitro-L-arginine methylester (L-NAME; 20mM) did not attenuate the NGF-mediated increase in luciferase activity, while the inducible NOS inhibitor s-methylisothiourea (S-MIU; 2mM) partially attenuated this action of NGF. Inhibition of MAP kinase activation with 50μM U0126 or pre-treatment with the PKC inhibitor bisindolylmaleimide 1 (BIS-1; 10μM) prevented the NGF-mediated activation of the apoE promoter. Pre-treatment with the phospholipase C (PLC) inhibitor U73122 (5μM) partially inhibited the NGF-induced increase in luciferase activity while the Akt inhibitor LY294002 (10μM) had no effect. These data suggest NGF-induced apoE transcription requires MAP kinase and PKC activation and that these TrkA signaling pathways may be modulated by NO.

Sp1 and the 'hallmarks of cancer'

For many years, transcription factor Sp1 was viewed as a basal transcription factor and relegated to a role in the regulation of so-called housekeeping genes. Identification of Sp1's role in recruiting the general transcription machinery in the absence of a TATA box increased its importance in gene regulation, particularly in light of recent estimates that the majority of mammalian genes lack a TATA box. In this review, we briefly consider the history of Sp1, the founding member of the Sp family of transcription factors. We review the evidence suggesting that Sp1 is highly regulated by post-translational modifications that positively and negatively affect the activity of Sp1 on a wide array of genes. Sp1 is over-expressed in many cancers and is associated with poor prognosis. Targeting Sp1 in cancer treatment has been suggested; however, our review of the literature on the role of Sp1 in the regulation of genes that contribute to the 'hallmarks of cancer' illustrates the extreme complexity of Sp1 functions. Sp1 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, as well as genes involved in essential cellular functions, including proliferation, differentiation, the DNA damage response, apoptosis, senescence and angiogenesis. Sp1 is also implicated in inflammation and genomic instability, as well as epigenetic silencing. Given the apparently opposing effects of Sp1, a more complete understanding of the function of Sp1 in cancer is required to validate its potential as a therapeutic target.

Cytokeratin19 induced by HER2/ERK binds and stabilizes HER2 on cell membranes

Cytokeratin19 (KRT19) is widely used as a biomarker for the detection of disseminated tumors. Using an LC-MS/MS proteomics approach, we found that KRT19 was upregulated in HER2-overexpressing cells and tissues. KRT19 expression was induced by HER2-downstream ERK at the transcriptional level. Another HER2-downstream kinase, Akt, was found to phosphorylate KRT19 on Ser35 and induce membrane translocation of KRT19 and remodeling of KRT19 from filamentous to granulous form. KRT19 phosphorylated by Akt could bind HER2 on the plasma membrane and stabilized HER2 via inhibition of proteasome-mediated degradation of HER2. Silencing of KRT19 by shRNA resulted in increased ubiquitination and destabilization of HER2. Moreover, treatment of KRT19 antibody resulted in downregulation of HER2 and reduced cell viability. These data provide a new rationale for targeting HER2-positive breast cancers.

Up-regulation of urinary-type plasminogen activator correlates with high-risk papillary thyroid carcinoma with BRAF(V600E) mutation and its possible molecular mechanism

The aim of the present study is to investigate the relationship between urinary-type plasminogen activator (uPA) expression and clinicopathological features in papillary thyroid carcinoma (PTC) and to determine the signal transduction of PTC cells in vitro. PTC tissues from 42 patients were analyzed for the expression of uPA and the BRAF(V600E) mutation. BCPAP, a PTC cell line harboring the BRAF(V600E) mutation, was used to study MAPK signaling. PCR and direct sequencing were applied to analyze BRAF(V600E) mutation status. uPA mRNA expression was measured using a quantitative RT-PCR method, and uPA protein was localized using an immunohistochemical method. The ERK protein status was detected by Western blot analysis. uPA gene expression was significantly increased in PTC tissues as compared to the corresponding non-tumor tissues. Furthermore, the up-regulation of uPA mRNAs was correlated with high-risk clinicopathological features, including extrathyroid invasion, loss of cellular polarity/cohesiveness, and the BRAF(V600E) mutation. Marked dephosphorylation of ERK1/2 and down-regulation of uPA expression were detected when BCPAP was treated with a MEK inhibitor, U0126. MEK inhibitors might be a potential treatment strategy for aggressive PTC with BRAF(V600E) through inhibition of uPA expression.

RECK controls breast cancer metastasis by modulating a convergent, STAT3-dependent neoangiogenic switch

Metastasis is the primary cause of cancer-related death in oncology patients. A comprehensive understanding of the molecular mechanisms that cancer cells usurp to promote metastatic dissemination is critical for the development and implementation of novel diagnostic and treatment strategies. Here we show that the membrane protein RECK (Reversion-inducing cysteine-rich protein with kazal motifs) controls breast cancer metastasis by modulating a novel, non-canonical and convergent signal transducer and activator of transcription factor 3 (STAT3)-dependent angiogenic program. Neoangiogenesis and STAT3 hyperactivation are known to be fundamentally important for metastasis, but the root molecular initiators of these phenotypes are poorly understood. Our study identifies loss of RECK as a critical and previously unknown trigger for these hallmarks of metastasis. Using multiple xenograft mouse models, we comprehensively show that RECK inhibits metastasis, concomitant with a suppression of neoangiogenesis at secondary sites, while leaving primary tumor growth unaffected. Further, with functional genomics and biochemical dissection we demonstrate that RECK controls this angiogenic rheostat through a novel complex with cell surface receptors to regulate STAT3 activation, cytokine signaling, and the induction of both vascular endothelial growth factor and urokinase plasminogen activator. In accordance with these findings, inhibition of STAT3 can rescue this phenotype both in vitro and in vivo. Taken together, our study uncovers, for the first time, that RECK is a novel regulator of multiple well-established and robust mediators of metastasis; thus, RECK is a keystone protein that may be exploited in a clinical setting to target metastatic disease from multiple angles.

The tetraspanin CD81 protein increases melanoma cell motility by up-regulating metalloproteinase MT1-MMP expression through the pro-oncogenic Akt-dependent Sp1 activation signaling pathways

Despite the importance of multiple tetraspanin proteins in cancer invasion and metastasis, little is known about the role and significance of tetraspanin CD81 in these processes. In the present study, we examined CD81 effects on melanoma cell invasiveness and metastasis. Transfection of CD81 into melanoma cells lacking endogenous CD81 expression significantly enhanced the migrating, invasive, and metastatic abilities of melanoma cells. Interestingly, membrane type 1 matrix metalloproteinase (MT1-MMP) expression was found in CD81-expressing melanoma cells but not in CD81-deficient cells. siRNA knockdown of CD81 in melanoma cells with endogenous CD81 demonstrated decreased MT1-MMP levels and cell motility. Notably, CD81-induced cell migration was abrogated by antibody blocking and siRNA knockdown of MT1-MMP, indicating that MT1-MMP is responsible for CD81-stimulated melanoma cell migration. Promoter analysis revealed an essential role of the Sp1 transcription factor in CD81-induced MT1-MMP transcription. We also demonstrate that the Sp1-activating Akt pathway is involved in adhesion-dependent CD81 signaling to induce MT1-MMP expression and cell motility. Importantly, human skin cancer tissue specimens displayed a positive correlation of CD81 with MT1-MMP expression levels and a close association of CD81 with malignant melanomas. Taken together, these results strongly suggest that CD81 stimulates melanoma cell motility by inducing MT1-MMP expression through the Akt-dependent Sp1 activation signaling pathway, leading to increased melanoma invasion and metastasis.

TGF-β-activated kinase 1 (TAK1) signaling regulates TGF-β-induced WNT-5A expression in airway smooth muscle cells via Sp1 and β-catenin

WNT-5A, a key player in embryonic development and post-natal homeostasis, has been associated with a myriad of pathological conditions including malignant, fibroproliferative and inflammatory disorders. Previously, we have identified WNT-5A as a transcriptional target of TGF-β in airway smooth muscle cells and demonstrated its function as a mediator of airway remodeling. Here, we investigated the molecular mechanisms underlying TGF-β-induced WNT-5A expression. We show that TGF-β-activated kinase 1 (TAK1) is a critical mediator of WNT-5A expression as its pharmacological inhibition or siRNA-mediated silencing reduced TGF-β induction of WNT-5A. Furthermore, we show that TAK1 engages p38 and c-Jun N-terminal kinase (JNK) signaling which redundantly participates in WNT-5A induction as only simultaneous, but not individual, inhibition of p38 and JNK suppressed TGF-β-induced WNT-5A expression. Remarkably, we demonstrate a central role of β-catenin in TGF-β-induced WNT-5A expression. Regulated by TAK1, β-catenin is required for WNT-5A induction as its silencing repressed WNT-5A expression whereas a constitutively active mutant augmented basal WNT-5A abundance. Furthermore, we identify Sp1 as the transcription factor for WNT-5A and demonstrate its interaction with β-catenin. We discover that Sp1 is recruited to the WNT-5A promoter in a TGF-β-induced and TAK1-regulated manner. Collectively, our findings describe a TAK1-dependent, β-catenin- and Sp1-mediated signaling cascade activated downstream of TGF-β which regulates WNT-5A induction.

Neural epidermal growth factor-like like protein 2 (NELL2) promotes aggregation of embryonic carcinoma P19 cells by inducing N-cadherin expression

NELL2 was first identified as a mammalian homolog of chick NEL (Neural EGF-like) protein. It is almost exclusively expressed in neurons of the rat brain and has been suggested to play a role in neural differentiation. However, there is still no clear evidence for the detailed function of NELL2 in the differentiation of neurons. In this study, we identified NELL2 function during neural differentiation of mouse embryonic carcinoma P19 cells. Endogenous expression of NELL2 in the P19 cells increased in parallel with the neuronal differentiation induced by retinoic acid (RA). We found that the mouse NELL2 promoter contains RA response elements (RAREs) and that treatment with RA increased NELL2 promoter activity. Transfection of P19 cells with NELL2 expression vectors induced a dramatic increase in cell aggregation, resulting in the facilitation of neural differentiation. Moreover, NELL2 significantly increased N-cadherin expression in the P19 cell. These data suggest that NELL2 plays an important role in the regulation of neuronal differentiation via control of N-cadherin expression and cell aggregation.

Transforming growth factor-Beta and urokinase-type plasminogen activator: dangerous partners in tumorigenesis-implications in skin cancer

Transforming growth factor-beta (TGF-β) is a pleiotropic factor, with several different roles in health and disease. TGF-β has been postulated as a dual factor in tumor progression, since it represses epithelial tumor development in early stages, whereas it stimulates tumor progression in advanced stages. During tumorigenesis, cancer cells acquire the capacity to migrate and invade surrounding tissues and to metastasize different organs. The urokinase-type plasminogen activator (uPA) system, comprising uPA, the uPA cell surface receptor, and plasminogen-plasmin, is involved in the proteolytic degradation of the extracellular matrix and regulates key cellular events by activating intracellular signal pathways, which together allow cancer cells to survive, thus, enhancing cell malignance during tumor progression. Due to their importance, uPA and its receptor are tightly transcriptionally regulated in normal development, but are deregulated in cancer, when their activity and expression are related to further development of cancer. TGF-β regulates uPA expression in cancer cells, while uPA, by plasminogen activation, may activate the secreted latent TGF-β, thus, producing a pernicious cycle which contributes to the enhancement of tumor progression. Here we review the specific roles and the interplay between TGF-β and uPA system in cancer cells and their implication in skin cancer.

Stromal cell-derived factor-1 (SDF-1) enhances cells invasion by αvβ6 integrin-mediated signaling in ovarian cancer

Ovarian carcinoma is a common gynecological malignancy and a great threat to health as a result of metastasis. The chemokine stromal-derived factor (SDF-1) plays multiple roles in tumor pathogenesis. However, the precise molecular mechanism underlying SDF-1-induced ovarian cancer cell invasion is still undefined. αvβ6 integrin is an important factor in tumor progression. Therefore, we speculate that SDF-1-enhanced ovarian cancer cell invasion is related to αvβ6 integrin-mediated signaling. After culturing with SDF-1, an obvious time- and dose-dependent increase in αvβ6 integrin was demonstrated. Furthermore, CXC receptor 4 (CXCR4) was responsible for SDF-1-induced αvβ6 integrin expression. Simultaneously, SDF-1 was found to dramatically enhance extracellular matrix degradation via urokinase-type plasminogen activator (uPA) expression and cell invasion by αvβ6 integrin expression; these reinforce failed to be increased when pretreatment was performed with the CXCR4 inhibitor AMD3100 or anti-αvβ6 integrin antibody, respectively. In addition, αvβ6 integrin induced the phosphorylation of p38 MAPK and PI3 K/Akt, contributing to the up-regulation of uPA, as treatment with the specific inhibitor for p38 mitogen-activated protein kinases (MAPK) (SB203580) or phosphatidylinositol 3-kinase (PI3 K)/Akt (LY294002) strikingly abrogated uPA expression. Taken together, these results demonstrated that SDF-1 enhanced ovarian cancer cell invasion through αvβ6 integrin-mediated uPA expression via the p38 MAPK and PI3 K/Akt pathway. Consequently, our findings will provide a new explanation about how SDF-1 aggravates the pathogenesis of ovarian cancer.

A novel role for RIP1 kinase in mediating TNFα production

Receptor-interacting protein 1 (RIP1) is a Ser/Thr kinase with both kinase-dependent and kinase-independent roles in death receptor signaling. The kinase activity of RIP1 is required for necroptosis, a caspase-independent pathway of programmed cell death. In some cell types, the inhibition of caspases leads to autocrine production of TNFα, which then activates necroptosis. Here, we describe a novel role for RIP1 kinase in regulating TNFα production after caspase inhibition. Caspase inhibitors activate RIP1 kinase and another protein, EDD, to mediate JNK signaling, which stimulates Sp1-dependent transcription of TNFα. This pathway is independent of nuclear factor κB and also occurs after Smac mimetic/IAP antagonist treatment or the loss of TNF receptor-associated factor 2 (Traf2). These findings implicate cIAP1/2 and Traf2 as negative regulators of this RIP1 kinase-dependent TNFα production pathway and suggest a novel role for RIP1 kinase in mediating TNFα production under certain conditions.

Stromal cell-derived factor-1/CXC receptor 4 and β1 integrin interaction regulates urokinase-type plasminogen activator expression in human colorectal cancer cells

The stromal cell-derived factor-1 (SDF-1)/CXC receptor 4 (CXCR4) axis has been shown to play a role in colorectal cancer progression. In addition, the protease urokinase-type plasminogen activator (uPA) is an important factor in tumor cell invasion and metastasis. However, the mechanism by which SDF-1 mediates uPA expression in human colorectal cancer cells remains unknown. We investigated the molecular mechanism governing the interaction between SDF-1 stimulation and uPA expression in three human colon cancer cell lines (DLD-1, SW48, and COLO 205). We found that SDF-1 stimulation led to an increase in the expression and secretion of uPA in these cells. Experiments involving specific inhibitors and small interfering RNA demonstrated that the activation of p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt pathways are critical for SDF-1-induced uPA expression. Analysis of transcription factor binding using ELISA and chromatin immunoprecipitation assays revealed that SDF-1 increased Sp1- and AP-1-DNA-binding activities in DLD-1 cells. Inhibition of Sp1 and AP-1 activation blocked the SDF-1-induced expression and activity of the uPA promoter. The effect of SDF-1 on DLD-1 signaling and uPA expression was mediated by the CXCR4/β1 integrin axis. In summary, our findings elucidate the mechanisms of SDF-1/CXCR4 downstream signaling and provide insights into the function of SDF-1 in colon cancer cells.

Transcriptional hallmarks of Noonan syndrome and Noonan-like syndrome with loose anagen hair

Noonan syndrome (NS) is among the most common nonchromosomal disorders affecting development and growth. NS is genetically heterogeneous, being caused by germline mutations affecting various genes implicated in the RAS signaling network. This network transduces extracellular signals into intracellular biochemical and transcriptional responses controlling cell proliferation, differentiation, metabolism, and senescence. To explore the transcriptional consequences of NS-causing mutations, we performed global mRNA expression profiling on peripheral blood mononuclear cells obtained from 23 NS patients carrying heterozygous mutations in PTPN11 or SOS1. Gene expression profiling was also resolved in five subjects with Noonan-like syndrome with loose anagen hair (NS/LAH), a condition clinically related to NS and caused by an invariant mutation in SHOC2. Robust transcriptional signatures were found to specifically discriminate each of the three mutation groups from 21 age- and sex-matched controls. Despite the only partial overlap in terms of gene composition, the three signatures showed a notable concordance in terms of biological processes and regulatory circuits affected. These data establish expression profiling of peripheral blood mononuclear cells as a powerful tool to appreciate differential perturbations driven by germline mutations of transducers involved in RAS signaling and to dissect molecular mechanisms underlying NS and other RASopathies. Hum Mutat 33:703–709, 2012. © 2012 Wiley Periodicals, Inc.

Sp1 phosphorylation by cyclin-dependent kinase 1/cyclin B1 represses its DNA-binding activity during mitosis in cancer cells

Sp1 is important for the transcription of many genes. Our previous studies have shown that Sp1 is degraded in normal cell, but it is preserved in cancer cells during mitosis and exists a priori in the daughter cells, ready to engage in gene transcription and thereby contributes to the proliferation and survival of cancer cells. The mechanism by which Sp1 is preserved in cancer cells during mitosis remains unknown. In this study, we observed that Sp1 strongly colocalized with cyclin-dependent kinase 1 (CDK1)/cyclin B1 during mitosis. Moreover, we showed that Sp1 is a novel mitotic substrate of CDK1/cyclin B1 and is phosphorylated by it at Thr 739 before the onset of mitosis. Phospho-Sp1 reduced its DNA-binding ability and facilitated the chromatin condensation process during mitosis. Mutation of Thr739 to alanine resulted in Sp1 remaining in the chromosomes, delayed cell-cycle progression, and eventually led to apoptosis. Screening of Sp1-associated proteins during mitosis by using liquid chromatography/mass spectrometry indicated the tethering of Sp1 to myosin/F-actin. Furthermore, phospho-Sp1 and myosin/F-actin appeared to exist as a congregated ring at the periphery of the chromosome. However, at the end of mitosis and the beginning of interphase, Sp1 was dephosphorylated by PP2A and returned to the chromatin. These results indicate that cancer cells use CDK1 and PP2A to regulate the movement of Sp1 in and out of the chromosomes during cell-cycle progression, which may benefit cancer-cell proliferation.

Significant biological role of sp1 transactivation in multiple myeloma

PURPOSE

The transcription factor specificity protein 1 (Sp1) controls number of cellular processes by regulating the expression of critical cell cycle, differentiation, and apoptosis-related genes containing proximal GC/GT-rich promoter elements. We here provide experimental and clinical evidence that Sp1 plays an important regulatory role in multiple myeloma (MM) cell growth and survival.

EXPERIMENTAL DESIGN

We have investigated the functional Sp1 activity in MM cells using a plasmid with Firefly luciferase reporter gene driven by Sp1-responsive promoter. We have also used both siRNA- and short hairpin RNA-mediated Sp1 knockdown to investigate the growth and survival effects of Sp1 on MM cells and further investigated the anti-MM activity of terameprocol (TMP), a small molecule that specifically competes with Sp1-DNA binding in vitro and in vivo.

RESULTS

We have confirmed high Sp1 activity in MM cells that is further induced by adhesion to bone marrow stromal cells (BMSC). Sp1 knockdown decreases MM cell proliferation and induces apoptosis. Sp1-DNA binding inhibition by TMP inhibits MM cell growth both in vitro and in vivo, inducing caspase-9-dependent apoptosis and overcoming the protective effects of BMSCs.

CONCLUSIONS

Our results show Sp1 as an important transcription factor in myeloma that can be therapeutically targeted for clinical application by TMP.

Thalidomide Analogues Suppress Lipopolysaccharide-Induced Synthesis of TNF-α and Nitrite, an Intermediate of Nitric Oxide, in a Cellular Model of Inflammation

An unregulated neuroinflammation accompanies numerous chronic and acute neurodegenerative disorders and it is postulated that such a neuroinflammatory component likely exacerbates disease progression. A key player in brain inflammation is the microglial cell; a vital soluble factor synthesized by activated microglial cells is the key cytokine, tumor necrosis factor-alpha (TNF-α). Additionally, microglial cells release IL-1α/β, reactive oxygen species (ROS), such as superoxide (O(2) (-)) and reactive nitrogen species (RNS) like nitric oxide (NO). Nitric oxide reactive oxygen species can undergo various forms of interactions in cells whereby the synthesis of RNS / ROS intermediates are generated that can damage cell membranes. The presence of oxidative damaged cells is implicated with the abnormal cellular activity in brain or in the spinal cord, and is a classical feature of neurodegenerative disorders. To aid characterize this process, a quantitative analysis of nitrite generation was undertaken on agents developed to lower TNF-α levels in cell culture. Nitrite is a stable end product of nitric oxide metabolism and, thereby, acts as a surrogate measure of the highly unstable nitric oxide. Utilizing a RAW 264.7 cellular model of lipopolysaccharide-induced inflammation that induces high levels of TNF-α protein accompanied by a robust generation of nitrite, the properties of a series of thalidomide-based TNF-α synthesis inhibitors were evaluated to reduce the levels of both. Specific analogues of thalidomide effectively suppressed the generation of both TNF-α and nitrite at well-tolerated doses.

Targeting TNF-α to elucidate and ameliorate neuroinflammation in neurodegenerative diseases

Inflammatory signals generated within the brain and peripheral nervous system direct diverse biological processes. Key amongst the inflammatory molecules is tumor necrosis factor-α (TNF-α), a potent pro-inflammatory cytokine that, via binding to its associated receptors, is considered to be a master regulator of cellular cascades that control a number of diverse processes coupled to cell viability, gene expression, synaptic integrity and ion homeostasis. Whereas a self-limiting neuroinflammatory response generally results in the resolution of an intrinsically or extrinsically triggered insult by the elimination of toxic material or injured tissue to restore brain homeostasis and function, in the event of an unregulated reaction, where the immune response persists, inappropriate chronic neuroinflammation can ensue. Uncontrolled neuroinflammatory activity can induce cellular dysfunction and demise, and lead to a self-propagating cascade of harmful pathogenic events. Such chronic neuroinflammation is a typical feature across a range of debilitating common neurodegenerative diseases, epitomized by Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis, in which TNF-α expression appears to be upregulated and may represent a valuable target for intervention. Elaboration of the protective homeostasis signaling cascades from the harmful pathogenic ones that likely drive disease onset and progression could aid in the clinical translation of approaches to lower brain and peripheral nervous system TNF-α levels, and amelioration of inappropriate neuroinflammation.

GATA6 promotes colon cancer cell invasion by regulating urokinase plasminogen activator gene expression

GATA6 is a zinc finger transcription factor expressed in the colorectal epithelium. We have examined the expression of GATA6 in colon cancers and investigated the mechanisms by which GATA6 regulates colon cancer cell invasion. GATA6 was overexpressed in colorectal polyps and primary and metastatic tumors. GATA6 was strongly expressed in both the nuclear and cytoplasmic compartments of the colon cancer cells. GATA6 expression was upregulated in invasive HT29 and KM12L4 cells compared with the parental HT29 and KM12 cells and positively correlated with urokinase-type plasminogen activator (uPA) gene expression. Small interfering RNA (siRNA) knockdown of GATA6 resulted in reduced uPA gene expression and cell invasion. GATA6 bound to the uPA gene regulatory sequences in vivo and activated uPA promoter activity in vitro. uPA promoter deletion analysis indicated that the promoter proximal Sp1 sites were required for GATA6 activation of the uPA promoter. Accordingly, GATA6 physically associated with Sp1 and siRNA knockdown of Sp1 decreased GATA6 activation of the uPA promoter activity suggesting that Sp1 recruits GATA6 to the uPA promoter and mediates GATA6 induced activation of the uPA promoter activity. On the basis of our results, we conclude that GATA6 is an important regulator of uPA gene expression, and the dysregulated expression of GATA6 contributes to colorectal tumorigenesis and tumor invasion.

Curcumin facilitates fibrinolysis and cellular migration during wound healing by modulating urokinase plasminogen activator expression

Urokinase plasminogen activator (uPA) plays a vital role in the early phases of wound healing by aiding fibrin dissolution and promoting the migration, proliferation, and adhesion of various cells to the wound bed. The efficacy of botanicals in healing wounds is an area of active research. Among these, curcumin, a yellow pigment abundant in turmeric rhizome, has been the center of extensive studies. This study focused on the effect of curcumin on uPA expression and its consequence on fibrin dissolution and cellular migration. Treatment of human fibroblast cells with curcumin caused an upregulation of uPA mRNA and protein. Activation of JNK and p38 MAPK signal pathways was necessary for the upregulation of uPA. Curcumin treatment resulted in an increase in fibrinolytic activity and cell migration towards the wound area. The involvement of uPA in fibrinolysis and cell migration was confirmed by zymography and siRNA studies, respectively.

Gastrin increases its own synthesis in gastrointestinal cancer cells via the CCK2 receptor

The involvement of the gastrointestinal hormone gastrin in the development of gastrointestinal cancer is highly controversial. Here we demonstrate a positive-feedback loop whereby gastrin, acting via the CCK2 receptor, increases its own expression. Such an autocrine loop has not previously been reported for any other gastrointestinal hormone. Gastrin promoter activation was dependent on the MAP kinase pathway and did not involve Sp1 binding sites or epidermal growth factor receptor transactivation. As the treatment of gastrointestinal cancer cells with amidated gastrin led to increased expression of non-amidated gastrins, the positive-feedback loop may contribute to the sustained increase in circulating gastrins observed in colorectal cancer patients.

Tumor necrosis factor-alpha mediated signaling in neuronal homeostasis and dysfunction

Tumor necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory molecule, which upon engagement with its cognate receptors on target cells, triggers downstream signaling cascades that control a number of cellular processes related to cell viability, gene expression, ion homeostasis, and synaptic integrity. In the central nervous system (CNS), TNF-alpha is produced by brain-resident astrocytes, microglia, and neurons in response to numerous intrinsic and extrinsic stimuli. This review will summarize the key events that lead to TNF-alpha elaboration in the CNS, and the effects that these inflammatory signals impart on neuronal signaling in the context of homeostasis and neuropathology.