[Show abstract][Hide abstract] ABSTRACT: Despite advances in its treatment, CNS lymphoma remains a devastating disease. Taking advantage of the tumour-tropic properties of neural stem cells (NSCs) is a novel therapeutic strategy. To apply this strategy to the treatment of CNS lymphoma, we investigated the role of NSCs expressing carboxyl esterase (HB1.F3.CE), which activates irinotecan.
In order to find in vitro bystander effects of engineered NSCs, we performed cell viability assays. In vivo, the HB1.F3.CE cells were injected into the brain of mice with orthotopic CNS lymphoma. Mice were then treated with irinotecan by systemic administration.
The HB1.F3.CE cells significantly inhibited the growth of Raji cells with irinotecan treatment. In vivo, the HB1.F3.CE cells migrated into the tumour and significantly reduced tumour volume. In addition, survival of mice was prolonged by treatment with HB1.F3.CE and irinotecan.
Transplantation of human NSCs encoding CE into brain, combined with irinotecan therapy, may be an effective treatment regimen for CNS lymphoma.
Anticancer research 12/2013; 33(12):5335-5342. · 1.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radiotherapy is the most widely used therapeutic modality in brain metastasis; however, it only provides palliation due to inevitable tumor recurrence. Resistance of tumor cells to ionizing radiation is a major cause of treatment failure. A critical unmet need in oncology is to develop rationale driven approaches that can enhance the efficacy of radiotherapy against metastatic tumor. Utilizing in vivo orthotopic primary tumor and brain metastasis models that recapitulate clinical situation of the patients with metastatic breast cancer, we investigated a molecular mechanism through which metastatic tumor cells acquire resistance to radiation. Recent studies have demonstrated that the hepatocyte growth factor (HGF)-c-Met pathway is essential for the pathologic development and progression of many human cancers such as proliferation, invasion and resistance to anticancer therapies. In this study, c-Met signaling activity as well as total c-Met expression was significantly upregulated in both breast cancer cell lines irradiated in vitro and ex vivo radio-resistant cells derived from breast cancer brain metastatic xenografts. To interrogate the role of c-Met signaling in radioresistance of brain metastasis, we evaluated the effects on tumor cell viability, clonogenicity, sensitivity to radiation, and in vitro/in vivo tumor growth after targeting c-Met by small-hairpin RNA (shRNA) or small-molecule kinase inhibitor (PF-2341066). Although c-Met silencing or radiation alone demonstrated a modest decrease in clonogenic growth of parental breast cancers and brain metastatic derivatives, combination of two modalities showed synergistic antitumor effects resulting in significant prolongation of overall survival in tumor-bearing mice. Taken together, optimizing c-Met targeting in combination with radiation is critical to enhance the effectiveness of radiotherapy in the treatments of brain metastasis.Laboratory Investigation advance online publication, 4 February 2013; doi:10.1038/labinvest.2012.180.
[Show abstract][Hide abstract] ABSTRACT: Background
Glioblastoma (GBM) is the most lethal and common type of primary brain tumor. Recent evidence suggests that a subpopulation of GBM cells (glioblastoma stem cells [GSCs]) is critical for tumor progression, invasion, and therapeutic resistance. We and others have demonstrated that MET, a receptor tyrosine kinase, positively regulates the stemness phenotype and radioresistance of GSCs. Here, we interrogated the downstream effector pathways of MET signaling in GSCs.Methods
We have established a series of GSCs and xenograft tumors derived from freshly dissociated specimens from patients with GBM and characterized a subpopulation enriched with MET activation (MET(high/+)). Through global expression profiling and subsequent pathways analysis, we identified signaling pathways that are enriched in MET(high/+) populations, one of which is Wnt/β-catenin signaling pathway. To determine molecular interaction and the biological consequences of MET and Wnt/β-catenin signaling, we used pharmacological and shRNA-mediated genetic inhibition and performed various molecular and cellular analyses, including flow cytometry, immunohistochemistry, and clonogenicity assays.ResultsWe found that Wnt/β-catenin signaling is highly active in MET(high/+) cells, compared with bulk tumor cells. We also showed that Wnt/β-catenin signaling activities in GBM are directly modulated by the addition of ligand-mediated MET activation or MET inhibition. Furthermore, the ectopic expression of active-β-catenin (S37A and S45Y) rescued the phenotypic effects caused by MET inhibition.Conclusion
These data suggest that Wnt/β-catenin signaling is a key downstream effector of MET signaling and contributes to the maintenance of GSC and GBM malignancy.
[Show abstract][Hide abstract] ABSTRACT: Primary lung tumors, breast tumors, and melanoma metastasize mainly in the brain where therapy is limited to surgery and radiation. To investigate the molecular basis of brain metastases, we isolated brain-trophic metastatic MDA-MB-435-LvBr2 (LvBr2) cells via left ventricle (LV) injection of MDA-MB-435 cells into immunodeficiency (NOD/SCID) mice. Whereas parent MDA-MB-435 cells displayed an elongated morphology, LvBr2 cells were round and displayed an aggregated distribution. LvBr2 cells expressed lower β-catenin levels and higher heterogeneous nuclear ribonucleoprotein C1/C2 (hnRNPC) levels than parental cells. Since microRNAs are known to play an important role in cancer progression including metastasis, we screened microRNAs expressed specifically in brain metastases. MicroRNA-146a was almost undetectable in LvBr2 cells and highly expressed in the parental cells. Overexpression of miR-146a increased β-catenin expression and suppressed the migratory and invasive activity of LvBr2 cells. The miR-146a-elicited decrease in hnRNPC in turn lowered the expression of MMP-1, uPA, and uPAR and inhibited the migratory and invasive activity of LvBr2 cells. Taken together, our findings indicate that miR-146a is virtually absent from brain metastases and can suppress their metastatic potential including their migratory and invasive activities associated with upregulation of β-catenin and downregulation of hnRNPC.
Molecules and Cells 09/2012; 34(3):329-34. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Glioblastomas multiforme (GBM) contain highly tumorigenic, self-renewing populations of stem/initiating cells [glioblastoma stem cells (GSC)] that contribute to tumor propagation and treatment resistance. However, our knowledge of the specific signaling pathways that regulate GSCs is limited. The MET tyrosine kinase is known to stimulate the survival, proliferation, and invasion of various cancers including GBM. Here, we identified a distinct fraction of cells expressing a high level of MET in human primary GBM specimens that were preferentially localized in perivascular regions of human GBM biopsy tissues and were found to be highly clonogenic, tumorigenic, and resistant to radiation. Inhibition of MET signaling in GSCs disrupted tumor growth and invasiveness both in vitro and in vivo, suggesting that MET activation is required for GSCs. Together, our findings indicate that MET activation in GBM is a functional requisite for the cancer stem cell phenotype and a promising therapeutic target.
Cancer Research 05/2012; 72(15):3828-38. · 9.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radiation therapy is an indispensable therapeutic modality for various brain diseases. Though endogenous neural stem cells (NSCs) would provide regenerative potential, many patients nevertheless suffer from radiation-induced brain damage. Accordingly, we tested beneficial effects of exogenous NSC supplementation using in vivo mouse models that received whole brain irradiation. Systemic supplementation of primarily cultured mouse fetal NSCs inhibited radiation-induced brain atrophy and thereby preserved brain functions such as short-term memory. Transplanted NSCs migrated to the irradiated brain and differentiated into neurons, astrocytes, or oligodendrocytes. In addition, neurotrophic factors such as NGF were significantly increased in the brain by NSCs, indicating that both paracrine and replacement effects could be the therapeutic mechanisms of NSCs. Interestingly, NSCs also differentiated into brain endothelial cells, which was accompanied by the restoration the cerebral blood flow that was reduced from the irradiation. Inhibition of the VEGF signaling reduced the migration and trans-differentiation of NSCs. Therefore, trans-differentiation of NSCs into brain endothelial cells by the VEGF signaling and the consequential restoration of the cerebral blood flow would also be one of the therapeutic mechanisms of NSCs. In summary, our data demonstrate that exogenous NSC supplementation could prevent radiation-induced functional loss of the brain. Therefore, successful combination of brain radiation therapy and NSC supplementation would provide a highly promising therapeutic option for patients with various brain diseases.
PLoS ONE 01/2012; 7(2):e25936. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Glioblastoma (GBM) patients have dismal median survival even with the most rigorous treatments currently available. Radiotherapy is the most effective non-surgical therapy for GBM patients; however, patients succumb due to tumor recurrence within a year. To develop a curative therapeutic approach, we need to better understand the underlying molecular mechanism of radiation resistance in GBM. Towards this goal, we developed an in vivo orthotopic GBM model system that mimics the radiation response of human GBM, using both established-GBM cell line and patient-derived freshly dissociated GBM specimen. In-vivo ionizing radiation (IR) treatment prolonged the survival of mice with intracranical tumor derived from U373MG, but failed to prevent tumor recurrence. U373MG and GBM578 cells isolated after in-vivo IR (U373-IR and 578-IR) were more clonogenic and enriched with stem cell-like characteristics, compared with mock-treated control tumor cells. Transcriptomic analyses and quantitative real-time reverse-transcription PCR analyses using these matched GBM cells before and after radiation treatment revealed that Wnt pathways were preferentially activated in post-IR GBM cells. U373-IR cells and 578-IR were enriched with cells positive for both active β-catenin (ABC) and Sox2 population, and this subpopulation was further increased after additional in-vitro radiation treatment, suggesting that radiation resistance of GBM is mediated due, in part, to the activation of stem cell-associated pathways including Wnt. Finally, pharmacological and siRNA inhibition of Wnt pathway significantly decreased the survival and clonogenicity of GBM cells and reduced their ABC(+)/Sox2(+) population. Together, these data suggest that Wnt activation is a molecular mechanism to confer GBM radioresistance and an important therapeutic target.
[Show abstract][Hide abstract] ABSTRACT: Neural stem cells (NSCs) led to the development of a novel strategy for delivering therapeutic genes to tumors. NSCs expressing rabbit carboxyl esterase (F3.CE), which activates CPT-11, significantly inhibited the growth of MDA-MB-435 cells in the presence of CPT-11. F3.CE cells migrated selectively into the brain metastases located in the opposite hemisphere. The treatment also significantly decreased tumor volume in immune-deficient mice bearing MDA-MB-435 tumors when F3.CE cells were transplanted into the contralateral hemisphere. The survival rate was significantly prolonged with the treatment with F3.CE and CPT-11. This strategy may be considered as an effective treatment regimen for brain metastases.
Cancer letters 07/2011; 311(2):152-9. · 5.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radiation is the most useful treatment modality for cancer patients. It initiates a series of signal cascades such as DNA damage response (DDR) signaling for repairing damaged DNA, arresting the cell cycle, and inducing cell death. Until now, few genes have been found to be regulated by radiation, which explains the molecular mechanisms of cellular responses to radiation. Although the transcriptional changes caused by radiation have been widely investigated, little is known about the direct evidence for the transcriptional control of DDR-related genes. Here, we examined the radiosensitivity of two non-small cell lung cancer cell lines (H460 and H1299), which have different p53 status. We monitored the time-dependent changes of 24 DDR-related gene expressions via microarray analysis. Based on the basal expression levels and temporal patterns, we further classified 24 DDR-related genes into four subgroups. Then, we also addressed the protein levels of several DDR-related genes such as TopBP1, Chk1 and Chk2, confirming the results of microarray analysis. Together, these results indicate that the expression patterns of DDR-related genes are associated with radiosensitivity and with the p53 statuses of H460 and H1299, which adds to the understanding of the complex biological responses to radiation.
Experimental and Molecular Medicine 06/2011; 43(7):419-26. · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: GaN-based light-emitting diodes (LEDs) grown on Si(111) substrates were fabricated with a vertical electrode method by using wafer bonding technology. The fabricated vertical LEDs showed a lower operating voltage and larger light output power than conventional LEDs due to enhancement in current spreading and reduction in tensile strain. The light output power of the vertical structured LEDs was 2.6 times higher than that of conventional LEDs, with an operating voltage at 20 mA reduced from 3.5 to 3.2 V.
[Show abstract][Hide abstract] ABSTRACT: Liver X receptor (LXR), a sterol-activated nuclear hormone receptor, has been implicated in cholesterol and fatty acid homeostasis via regulation of reverse cholesterol transport and de novo fatty acid synthesis. LXR is also involved in immune responses, including anti-inflammatory action and T cell proliferation. In this study, we demonstrated that activated LXR suppresses cell cycle progression and proliferation in certain cell types. Stimulation of LXR with synthetic ligand T0901317 or GW3965 inhibited cell growth rate and arrested the cell cycle at the G1/S boundary in several cells, such as RWPE1, THP1, SNU16, LNCaP, and HepG2. However, LXR ligands did not exhibit antiproliferative activity in PC3, HEK293, or HeLa cells. Interestingly, activated LXR-mediated cell cycle arrest is closely correlated with the lipogenic gene expression and triacylglyceride accumulation. In accordance with these findings, suppression of FAS via small-interference RNA (siRNA) partially alleviated the antiproliferative effect of LXR activation in RWPE1 cells. Together, these data suggest that LXR activation with its ligands inhibits cell proliferation and induces G1/S arrest through elevated lipogenic activity, thus proposing a novel effect of activated LXR on cell cycle regulation.
The Journal of Lipid Research 12/2010; 51(12):3425-33. · 4.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In obesity, dysregulation of adipocytokines is involved in several pathological conditions including diabetes and certain cancers. As a member of the adipocytokines, adiponectin plays crucial roles in whole-body energy homeostasis. Recently, it has been reported that the level of plasma adiponectin is reduced in several types of cancer patients. However, it is largely unknown whether and how adiponectin affects colon cancer cell growth. Here, we show that adiponectin suppresses the proliferation of colon cancer cells including HCT116, HT29, and LoVo. In colon cancer cells, adiponectin attenuated cell cycle progression at the G(1)/S boundary and concurrently increased expression of cyclin-dependent kinase inhibitors such as p21 and p27. Adiponectin stimulated AMP-activated protein kinase (AMPK) phosphorylation whereas inhibition of AMPK activity blunted the effect of adiponectin on the proliferation of colon cancer cells. Furthermore, knockdown of adiponectin receptors such as AdipoR1 and AdipoR2 relieved the suppressive effect of adiponectin on the growth of colon cancer cells. In addition, adiponectin repressed the expression of sterol regulatory element binding protein-1c, which is a key lipogenic transcription factor associated with colon cancers. These results suggest that adiponectin could inhibit the growth of colon cancer cells through stimulating AMPK activity.
[Show abstract][Hide abstract] ABSTRACT: We confirmed the potential of an aluminum nitride (AlN) substrate to be used as a bonding material for the high current operation of vertical light-emitting diodes (VLEDs). For the electrical connection to the top and bottom of the AlN substrate, via-holes were formed by laser drilling and then filled with Ag, which plays a role in improving the thermal dissipation from the VLEDs. The forward voltage of the fabricated AlN-bonded VLEDs was 3.54 V at 350 mA, which is similar to that of the Si-bonded VLEDs. It was also found that the light output power of the AlN-bonded VLEDs increased steadily with increasing injection current up to 1 A, while that of the Si-bonded VLEDs started to decrease at around 850 mA. In addition, the thermal resistance of the AlN-bonded VLEDs was significantly reduced, as compared with that of the Si-bonded VLEDs and conventional LEDs, under the same package conditions.
[Show abstract][Hide abstract] ABSTRACT: Liver X receptor (LXR) is a ligand-activated transcription factor that plays important roles in cholesterol and lipid homeostasis. However, ligand-induced posttranslational modification of LXR is largely unknown. Here, we show that ligand-free LXRalpha is rapidly degraded by ubiquitination. Without ligand, LXRalpha interacts with an ubiquitin E3-ligase protein complex containing breast and ovarian cancer susceptibility 1 (BRCA1)-associated RING domain 1 (BARD1). Interestingly, LXR ligand represses ubiquitination and degradation of LXRalpha, and the interaction between LXRalpha and BARD1 is inhibited by LXR ligand. Consistently, T0901317, a synthetic LXR ligand, increased the level of LXRalpha protein in liver. Moreover, overexpression of BARD1/BRCA1 promoted the ubiquitination of LXRalpha and reduced the recruitment of LXRalpha to the target gene promoters, whereas BARD1 knockdown reversed such effects. Taken together, these data suggest that LXR ligand prevents LXRalpha from ubiquitination and degradation by detaching BARD1/BRCA1, which might be critical for the early step of transcriptional activation of ligand-stimulated LXRalpha through a stable binding of LXRalpha to the promoters of target genes.
[Show abstract][Hide abstract] ABSTRACT: Highly reflective and thermally stable indium-tin-oxide (ITO)-Ag-Pt p-type reflectors for use in high-performance GaN-based light-emitting diodes (LEDs) have been investigated. The specific contact resistance of the ITO-Ag-Pt contacts was found to be 7.2 ×10<sup>-5</sup>Omegamiddotcm<sup>2</sup>. The ITO-Ag-Pt contacts showed a higher reflectance after thermal annealing (82% at 460 nm), while the reflectance of the ITO-Ag contacts was reduced from 81% to 65%. In addition, surface agglomeration was drastically decreased, indicating that the Pt layer efficiently prevents the surface agglomeration of the Ag layer. The vertical LEDs (VLEDs) fabricated with the ITO-Ag-Pt contacts had a 17% higher output power (at 20 mA) than the VLEDs fabricated with the ITO-Ag contacts.
[Show abstract][Hide abstract] ABSTRACT: Sterol regulatory element binding protein-1c (SREBP-1c) is a basic helix-loop-helix (bHLH) homodimeric transactivator, which induces itself and several lipogenic enzymes, notably fatty acid synthase (FAS). We demonstrated that hypoxia-inducible factor (HIF) represses the SREBP-1c gene by inducing Stimulated with retinoic acid (Stra)13/Differentiated embryo chondrocyte 1(DEC1) and its isoform, DEC2. Stra13/DEC1 and DEC2 are bHLH homodimeric transcription repressors. We found that both Stra13 and DEC2 inhibit SREBP-1c-induced transcription by competing with SREBP-1c for binding to the E-box in the SREBP-1c promoter and/or by interacting with SREBP-1c protein. DEC2 is instantly and temporarily induced in acute hypoxia, while Stra13 is induced in prolonged hypoxia. This expression profile reflects the finding that Stra13 represses DEC2, thus maintains low level of DEC2 in prolonged hypoxia. DEC2-siRNA restores the hypoxic repression but Stra13-siRNA fails to do so, suggesting that DEC2 is the major initiator of hypoxic repression of SREBP-1c, whereas Stra13 substitutes for DEC2 in prolonged hypoxia. Our findings imply that Stra13 and DEC2 are the mediators to repress SREBP-1c gene in response to hypoxia. By doing so, HIF and its targets, Stra13 and DEC2 reduce the ATP consuming anabolic lipogenesis prior to the actual decrease of ATP acting as a feed-forward mechanism.
Nucleic Acids Research 11/2008; 36(20):6372-85. · 8.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Liver X receptor (LXR)alpha and LXRbeta play important roles in fatty acid metabolism and cholesterol homeostasis. Although the functional roles of LXR in the liver, intestine, fat, and macrophages are well established, its role in pancreatic beta-cells has not been clearly defined. In this study, we revealed that chronic activation of LXR contributes to lipotoxicity-induced beta-cell dysfunction. We observed significantly elevated expression of LXR in the islets of diabetic rodent models, including fa/fa ZDF rats, OLETF rats, and db/db mice. In primary pancreatic islets and INS-1 insulinoma cells, activation of LXR with a synthetic ligand, T0901317, stimulated expression of the lipogenic genes ADD1/SREBP1c, FAS, and ACC and resulted in increased intracellular lipid accumulation. Moreover, chronic LXR activation induced apoptosis in pancreatic islets and INS-1 cells, which was synergistically promoted by high glucose conditions. Taken together, we suggest lipid accumulation caused by chronic activation of LXR in beta-cells as a possible cause of beta-cell lipotoxicity, a key step in the development of type 2 diabetes.
[Show abstract][Hide abstract] ABSTRACT: In adipocytes, oxidative stress and chronic inflammation are closely associated with metabolic disorders, including insulin resistance, obesity, cardiovascular disease, and type 2 diabetes. However, the molecular mechanisms underlying these metabolic disorders have not been thoroughly elucidated. In this report, we demonstrate that overexpression of glucose-6-phosphate dehydrogenase (G6PD) in adipocytes stimulates oxidative stress and inflammatory responses, thus affecting the neighboring macrophages. Adipogenic G6PD overexpression promotes the expression of pro-oxidative enzymes, including inducible nitric oxide synthase and NADPH oxidase, and the activation of nuclear factor-kappaB (NF-kappaB) signaling, which eventually leads to the dysregulation of adipocytokines and inflammatory signals. Furthermore, secretory factors from G6PD-overexpressing adipocytes stimulate macrophages to express more proinflammatory cytokines and to be recruited to the adipocytes; this would cause chronic inflammatory conditions in the adipose tissue of obesity. These effects of G6PD overexpression in adipocytes were abolished by pretreatment with NF-kappaB inhibitors or antioxidant drugs. Thus, we propose that a high level of G6PD in adipocytes may mediate the onset of metabolic disorders in obesity by increasing the oxidative stress and inflammatory signals.
[Show abstract][Hide abstract] ABSTRACT: Liver X receptors (LXRs) are nuclear hormone receptors that behave as lipid sensors of cellular cholesterol and fatty acid. Although LXR activation can alleviate hypercholesterolemia by inducing cholesterol efflux, it also results in undesirable effects of fatty acid synthesis, resulting in hepatic steatosis and hyperlipidemia. Therefore, it is critical to identify LXRalpha inhibitory agents that would repress fatty acid synthesis and hepatic lipid accumulation. In current study, screening of plant extracts used for traditional oriental medicine resulted in the identification of two candidates demonstrating selective LXRalpha inhibitory activity. These were whole leaf methanol extracts of Parthenocissua tricuspidata (MEH184) and Euscaphis japonica (MEH185). Both MEH184 and MEH185 decreased transcriptional activity of LXRalpha and the expression of LXRalpha target genes, such as FAS and ADD1/SREBP1c. Additionally, MEH184 and MEH184 significantly reduced lipogenesis and adipocyte differentiation. Together, the data imply that MEH184 and MEH185 possess selective antagonistic properties on LXRalpha to downregulate lipogenesis.
Biochemical and Biophysical Research Communications 11/2006; 349(2):513-8. · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: All-optical wavelength conversion at 10 Gb s−1 is demonstrated in a Mach–Zehnder interferometric wavelength converter (MZI-WC) module with monolithically integrated SOA preamplifiers and tapered-edge multimode interference couplers (TMMIs). A conventional buried-type 1 × 2 MMI coupler exhibits a minimal excess loss of 0.43 dB and a reflectivity of 5.1 × 10−4 (LMMI = 172 µm, WMMI = 12 µm). We adapt the 1 × 2 TMMI in the MZI-WC to improve back-reflection and poor uniformity, which is a major problem of conventional MMI and Y-branch. A good performance of the MZI-WC monolithically integrated with TMMI and SOA preamplifiers at 10 Gb s−1 is obtained with clear eye patterns, and a power penalty below 1.5 dB at a 10−9 bit error rate over the whole C band (45 nm span) is obtained. The dynamic input power range is enhanced up to 11.3 dB by adjusting only the injection current of the SOA preamplifier.
Semiconductor Science and Technology 09/2006; 21(10):1478. · 1.92 Impact Factor