Hypertonic saline reduces lipopolysaccharide-induced mouse brain edema through inhibiting aquaporin 4 expression

INTRODUCTION

Three percent sodium chloride (NaCl) treatment has been shown to reduce brain edema and inhibited brain aquaporin 4 (AQP4) expression in bacterial meningitis induced by Escherichia coli. Lipopolysaccharide (LPS) is the main pathogenic component of E. coli. We aimed to explore the effect of 3% NaCl in mouse brain edema induced by LPS, as well as to elucidate the potential mechanisms of action.

METHODS

Three percent NaCl was used to treat cerebral edema induced by LPS in mice in vivo. Brain water content, IL-1β, TNFα, immunoglobulin G (IgG), AQP4 mRNA and protein were measured in brain tissues. IL-1β, 3% NaCl and calphostin C (a specific inhibitor of protein kinase C) were used to treat the primary astrocytes in vitro. AQP4 mRNA and protein were measured in astrocytes. Differences in various groups were determined by one-way analysis of variance.

RESULTS

Three percent NaCl attenuated the increase of brain water content, IL-1β, TNFα, IgG, AQP4 mRNA and protein in brain tissues induced by LPS. Three percent NaCl inhibited the increase of AQP4 mRNA and protein in astrocytes induced by IL-1β in vitro. Calphostin C blocked the decrease of AQP4 mRNA and protein in astrocytes induced by 3% NaCl in vitro.

CONCLUSIONS

Osmotherapy with 3% NaCl ameliorated LPS-induced cerebral edema in vivo. In addition to its osmotic force, 3% NaCl exerted anti-edema effects possibly through down-regulating the expression of proinflammatory cytokines (IL-1β and TNFα) and inhibiting the expression of AQP4 induced by proinflammatory cytokines. Three percent NaCl attenuated the expression of AQP4 through activation of protein kinase C in astrocytes.

Abstract 2879: Pre-clinical characterization of Dacomitinib, an irreversible pan-HER inhibitor, combined with radiation therapy in head and neck cancer models

Introduction: Head and neck cancer is the 5th most common cancer worldwide; the majority of cases (>90%) are squamous cell carcinomas (SCCHNs). Despite advances in treatment, the 5-year overall survival rate for SCCHN patients still remains at ∼40-50%, underscoring the need to develop novel therapeutic strategies. EGFR is over-expressed in ∼90% of SCCHN cases, and is associated with tumor progression and poor prognosis. Dacomitinib (D), an irreversible pan-HER inhibitor, has demonstrated clinical potential in patients with non-small cell lung cancer, leading us to explore its therapeutic efficacy in SCCHN pre-clinical models, in combination with radiation therapy (RT), a curative modality for HNC management. Methods: The basal expression of EGFR family members was assessed via qRT-PCR in three SCCHN models (FaDu (human hypopharyngeal), UTSCC-8 & -42a (both laryngeal) squamous cancer, and NOE (normal oral epithelial) cell lines. MTS-based cell viability and clonogenic assays were performed with various concentrations of D, both alone and in combination with irradiation (IR). Inhibition of EGFR signalling by D was confirmed via immunoblotting. Cell cycle analysis was performed to assess mode of cytotoxicity. In vivo therapeutic studies were performed using FaDu xenografts in SCID mice; tumors were extracted post-treatment and examined for TUNEL, CD31, Ki67, and pEGFR via IHC. Results: EGFR was over-expressed in all three SCCHN, compared to the NOE cells. PF (50 nM) reduced FaDu cell viability by ∼25%, with an additive interaction being observed when D was combined with 2 Gy IR (∼36%). Similar trends were observed in the other two cell lines and also in the clonogenic assays. Immunoblotting confirmed a dose-dependent inhibition of EGFR signalling in D-treated SCCHN cells, along with downstream reduction of p-Erk, p-Akt, and p-mTOR expression. Cell cycle analyses showed ∼20% increase in the G0/G1 cell population in D-treated FaDu cells, and ∼10% increase in the sub-G cell population when D and IR were combined. Mice treated with the combination of D + IR exhibited a maximum tumor growth delay of ∼21 days, as compared to the IR only group, determined by time to tumor-plus-leg diameter of 14mm. Preliminary histological analysis of the extracted tumor tissue show ∼40% reduction in Ki67 staining in the PF + IR treated mice. The addition of D to IR appeared to be well-tolerated, with no change in body weight, or extent of alopecia. Conclusion: Dacomitinib effectively inhibited EGFR signalling in SCCHN models, leading to a reduction in cell viability and clonogenic survival in vitro, along with tumor growth delay in vivo. When D was combined with IR, there was an additive interaction, both in vitro and in vivo. Thus, D combined with RT may have a therapeutic benefit for patients with SCCHN.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2879. doi:1538-7445.AM2012-2879

Characterizing the hierarchical structures of bioactive sol-gel silicate glass and hybrid scaffolds for bone regeneration

Bone is the second most widely transplanted tissue after blood. Synthetic alternatives are needed that can reduce the need for transplants and regenerate bone by acting as active temporary templates for bone growth. Bioactive glasses are one of the most promising bone replacement/regeneration materials because they bond to existing bone, are degradable and stimulate new bone growth by the action of their dissolution products on cells. Sol-gel-derived bioactive glasses can be foamed to produce interconnected macropores suitable for tissue ingrowth, particularly cell migration and vascularization and cell penetration. The scaffolds fulfil many of the criteria of an ideal synthetic bone graft, but are not suitable for all bone defect sites because they are brittle. One strategy for improving toughness of the scaffolds without losing their other beneficial properties is to synthesize inorganic/organic hybrids. These hybrids have polymers introduced into the sol-gel process so that the organic and inorganic components interact at the molecular level, providing control over mechanical properties and degradation rates. However, a full understanding of how each feature or property of the glass and hybrid scaffolds affects cellular response is needed to optimize the materials and ensure long-term success and clinical products. This review focuses on the techniques that have been developed for characterizing the hierarchical structures of sol-gel glasses and hybrids, from atomic-scale amorphous networks, through the covalent bonding between components in hybrids and nanoporosity, to quantifying open macroporous networks of the scaffolds. Methods for non-destructive in situ monitoring of degradation and bioactivity mechanisms of the materials are also included.

Significance of dysregulated metadherin and microRNA-375 in head and neck cancer

PURPOSE

Despite recent improvements in local control of head and neck cancers (HNC), distant metastasis remains a major cause of death. Hence, further understanding of HNC biology, and in particular, the genes/pathways driving metastasis is essential to improve outcome.

EXPERIMENTAL DESIGN

Quantitative reverse transcriptase PCR (qRT-PCR) was used to measure the expression of miR-375 and metadherin (MTDH) in HNC patient samples. Targets of miR-375 were confirmed using qRT-PCR, Western blot analysis, and luciferase assays. Phenotypic effects of miR-375 reexpression and MTDH knockdown were assessed using viability (MTS), clonogenic survival, cell migration/invasion, as well as in vivo tumor formation assays. The prognostic significance of miR-375 or MTDH in nasopharyngeal carcinoma (NPC) was determined by comparing low versus high expression groups.

RESULTS

MiR-375 expression was significantly reduced (P = 0.01), and conversely, MTDH was significantly increased (P = 0.0001) in NPC samples. qRT-PCR, Western blots, and luciferase assays corroborated MTDH as a target of miR-375. Reexpression of miR-375 and siRNA knockdown of MTDH both decreased cell viability and clonogenic survival, cell migration/invasion, as well as in vivo tumor formation. NPC patients whose tumors expressed high levels of MTDH experienced significantly lower survival and, in particular, higher distant relapse rates (5-year distant relapse rates: 26% vs. 5%; P = 0.005).

CONCLUSIONS

Dysregulation of miR-375 and MTDH may represent an important oncogenic pathway driving human HNC progression, particularly distant metastases, which is now emerging as a major cause of death for HNC patients. Hence, targeting this pathway could potentially be a novel therapeutic strategy by which HNC patient outcome could be improved.

Introducing traditional Chinese nursing: a review of concepts, theories and practices

AIM

This paper discussed the basic concepts, theories and practices of traditional Chinese nursing (TCN) to enrich our understanding of relevant concepts and ways to contribute to human health.

BACKGROUND

Advantages of TCN include health education based on theories and techniques of traditional Chinese medicine. It focuses mainly on mobilizing humans' capacity for self-adjustment and self-rehabilitation to make a dynamic balance between yin and yang, qi and blood and zang and fu. It has played a significant role in the fields of primary nursing, geriatric nursing, hospice, family nursing, etc., in China.

METHOD

PubMed, CINAHL, Ovid Medline (English) and the Wang Fang (Chinese) databases were searched for literature on a range of keywords relating to traditional Chinese medicine and nursing. Forty references (13 English and 27 Chinese) were finally selected for review.

CONCLUSION

Practices of nursing care in traditional Chinese medicine are based mainly on the theories of yin-yang and the five elements. There are two prime characteristics in the theoretical system of TCN: holism and nursing determination based on syndrome differentiation. The distinctive content include prevention, daily care of patients, dietary nursing, etc. TCN, with its characteristics of little damage, little pain, ease of operation and low cost, is appropriately used in primary health care in China. By combining Western and Eastern philosophies and approaches to nursing, life phenomena can be better understood, and more ways to promote health can be exploited. Scientists are beginning to use Western research methods to establish effectiveness. Many common interventions would not, however, be considered safe in Western nursing practice without more evidence and consideration of health and safety issues.

Uroporphyrinogen decarboxylase is a radiosensitizing target for head and neck cancer

Head and neck cancer (HNC) is the eighth most common malignancy worldwide, comprising a diverse group of cancers affecting the head and neck region. Despite advances in therapeutic options over the last few decades, treatment toxicities and overall clinical outcomes have remained disappointing, thereby underscoring a need to develop novel therapeutic approaches in HNC treatment. Uroporphyrinogen decarboxylase (UROD), a key regulator of heme biosynthesis, was identified from an RNA interference-based high-throughput screen as a tumor-selective radiosensitizing target for HNC. UROD knockdown plus radiation induced caspase-mediated apoptosis and cell cycle arrest in HNC cells in vitro and suppressed the in vivo tumor-forming capacity of HNC cells, as well as delayed the growth of established tumor xenografts in mice. This radiosensitization appeared to be mediated by alterations in iron homeostasis and increased production of reactive oxygen species, resulting in enhanced tumor oxidative stress. Moreover, UROD was significantly overexpressed in HNC patient biopsies. Lower preradiation UROD mRNA expression correlated with improved disease-free survival, suggesting that UROD could potentially be used to predict radiation response. UROD down-regulation also radiosensitized several different models of human cancer, as well as sensitized tumors to chemotherapeutic agents, including 5-fluorouracil, cisplatin, and paclitaxel. Thus, our study has revealed UROD as a potent tumor-selective sensitizer for both radiation and chemotherapy, with potential relevance to many human malignancies.

Abstract 3967: Identification of metadherin as a novel target of miR-375 in head and neck cancer

Purpose: The objective of this study is to investigate the significance of miR-375 and its target metadherin in head and neck cancer (HNC) patients.

Methods and Results: Expression of miR-375 was measured by quantitative RT-PCR and observed to be significantly under expressed in both head and neck squamous cell (HNSCC) and nasopharyngeal carcinoma (NPC) samples by factors of 5.0 and 4.4, respectively. One mechanism of miR-375 silencing appears to be promoter methylation. Using a combination of experimentally-observed transcript changes after miR-375 re-expression in HNC cell lines, with in silico prediction algorithms, metadherin was identified as a novel target of miR-375. Luciferase reporter assays confirmed an inhibitory interaction between miR-375 and the 3’UTR of metadherin. Functional characterizations of miR-375 and metadherin were then conducted using FaDu (hypopharyngeal squamous cell) and C666-1 (nasopharyngeal) cancer cell lines. In vitro re-expression of miR-375 as well as knock-down of metadherin using siRNA markedly decreased cell viability and clonogenic survival (30% – 45%), cell migration (50% – 80%), and in vivo tumour forming ability in both cancer models. In vitro cell invasion was also significantly decreased by miR-375 over-expression and metadherin knock-down in FaDu cells (>90%). Western blot analyses demonstrated that metadherin knock-down resulted in reduced phosphorylation of PKB, indicating that the PI(3)K pathway may be involved in mediating these effects. Using qRT-PCR on 100 NPC and 22 HNSCC archival samples, there was an inverse relationship between metadherin over-expression with miR-375 under-expression, corroborating the relevance of this axis in primary human HNC tissues. Furthermore, NPC patients whose tumours expressed high levels of metadherin (defined as > median) experienced significantly lower overall and disease-free survival (5-year OS of 82%, DFS of 73%) compared to patients with low (< median) expression levels (5-year OS of 66%, DFS of 56%). Specifically, this reduced survival was most significantly related to distant metastases, wherein high metadherin expression was significantly associated with distant relapse (5-year distant relapse rates: 26% vs. 5% for high vs. low expressors, respectively).

Conclusions: We report that the miR-375:metadherin control mechanism may represent a novel oncogenic pathway driving human HNC progression, potentially mediated in part by the PI(3)K cascade. Most importantly, metadherin over-expression was a significant predictor of distant metastases, a major clinical challenge in HNC given the improvements in loco-regional control as a consequence of technical advances in radiation therapy delivery. Hence, targeting this pathway could be a potentially novel therapeutic strategy to improve outcome for HNC patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3967. doi:10.1158/1538-7445.AM2011-3967

MiR-218 suppresses nasopharyngeal cancer progression through downregulation of survivin and the SLIT2-ROBO1 pathway

Nasopharayngeal carcinoma (NPC) is an Epstein-Barr virus-associated malignancy most common in East Asia and Africa. Here we report frequent downregulation of the microRNA miR-218 in primary NPC tissues and cell lines where it plays a critical role in NPC progression. Suppression of miR-218 was associated with epigenetic silencing of SLIT2 and SLIT3, ligands of ROBO receptors that have been previously implicated in tumor angiogenesis. Exogenous expression of miR-218 caused significant toxicity in NPC cells in vitro and delayed tumor growth in vivo. We used an integrated trimodality approach to identify targets of miR-218 in NPC, cervical, and breast cell lines. Direct interaction between miR-218 and the 3'-untranslated regions (UTR) of mRNAs encoding ROBO1, survivin (BIRC5), and connexin43 (GJA1) was validated in a luciferase-based transcription reporter assay. Mechanistic investigations revealed a negative feedback loop wherein miR-218 regulates NPC cell migration via the SLIT-ROBO pathway. Pleotropic effects of miR-218 on NPC survival and migration were rescued by enforced expression of miR-218-resistant, engineered isoforms of survivin and ROBO1, respectively. In clinical specimens of NPC (n=71), ROBO1 overexpression was significantly associated with worse overall (P=0.04, HR=2.4) and nodal relapse-free survival (P=0.008, HR=6.0). Our findings define an integrative tumor suppressor function for miR-218 in NPC and further suggest that restoring miR-218 expression in NPC might be useful for its clinical management.

Bioactive glass scaffolds for bone regeneration and their hierarchical characterisation

Scaffolds are needed that can act as temporary templates for bone regeneration and actively stimulate vascularized bone growth so that bone grafting is no longer necessary. To achieve this, the scaffold must have a suitable interconnected pore network and be made of an osteogenic material. Bioactive glass is an ideal material because it rapidly bonds to bone and degrades over time, releasing soluble silica and calcium ions that are thought to stimulate osteoprogenitor cells. Melt-derived bioactive glasses, such as the original Bioglass® composition, are available commercially, but porous scaffolds have been difficult to produce because Bioglass and similar compositions crystallize on sintering. Sol-gel foam scaffolds have been developed that avoid this problem. They have a hierarchical pore structure comprising interconnected macropores, with interconnect diameters in excess of the 100 μm that is thought to be needed for vascularized bone ingrowth, and an inherent nanoporosity of interconnected mesopores (2–50 nm) which is beneficial for the attachment of osteoprogenitor cells. They also have a compressive strength in the range of cancellous bone. This paper describes the optimized sol-gel foaming process and illustrates the importance of optimizing the hierarchical structure from the atomic through nano, to the macro scale with respect to biological response.

Enhancer of Zeste homolog 2 (EZH2) is overexpressed in recurrent nasopharyngeal carcinoma and is regulated by miR-26a, miR-101, and miR-98

There is increasing evidence supporting the role of members of the polycomb group (PcG) gene family in tumor development and progression. However, their precise role in tumorigenesis and mechanisms of their regulation remain to be elucidated. Using nasopharyngeal carcinoma (NPC) as a disease model, a comprehensive analysis was undertaken on the clinical significance of EZH2 expression, identification of the cellular processes regulated by EZH2, and the mechanisms of its deregulated expression. Herein, we report EZH2 as being associated with a higher risk of relapse in NPC patients (P=0.002). Genome-wide microarray and bioinformatics identified several vital cellular processes (such as differentiation, development, and apoptosis) to be regulated by EZH2, corroborated by in vitro lethality, and delayed tumor formation in vivo upon EZH2 depletion. The combination of global microRNA (miR) profiling in primary NPC specimens, and in silico analyses provided several candidate miRs that could regulate EZH2. Using a luciferase-based assay, miR-26a, miR-101, and miR-98 were validated as bona fide regulators of EZH2 expression. In particular, miR-98 was underexpressed in relapsed patient samples, strongly suggesting an important role for the miR-98 and EZH2 axis in NPC biology.

Targeting polo-like kinase 1 enhances radiation efficacy for head-and-neck squamous cell carcinoma

PURPOSE

To investigate the efficacy of targeting polo-like kinase 1 (Plk1) combined with ionizing radiotherapy (RT) for head-and-neck squamous cell carcinoma (HNSCC).

METHODS AND MATERIALS

Polo-like kinase 1 messenger ribonucleic acid (mRNA) was targeted by small interfering RNA (siRNA) transfection into the FaDu HNSCC cell line; reduction was confirmed using quantitative real-time polymerase chain reaction. The cellular effects were assessed using [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium], clonogenic, flow cytometric, and caspase assays. In vivo efficacy of siPlk1 was evaluated using mouse xenograft models.

RESULTS

Small interfering Plk1 significantly decreased Plk1 mRNA expression, while also increasing cyclin B1 and p21(Waf1/CIP1) mRNA levels after 24 h. This depletion resulted in a time-dependent increase in FaDu cytotoxicity, which was enhanced by the addition of RT. Flow cytometric and caspase assays demonstrated progressive apoptosis, DNA double-strand breaks (gamma-H2AX), G2/M arrest, and activation of caspases 3 and 7. Implantation of siPlk1-treated FaDu cells in severe combined immunodeficient mice delayed tumor formation, and systemic administration of siPlk1 inhibited tumor growth enhanced by RT.

CONCLUSIONS

These data demonstrate the suitability of Plk1 as a potential therapeutic target for HNSCC, because Plk1 depletion resulted in significant cytotoxicity in vitro and abrogated tumor-forming potential in vivo. The effects of Plk1 depletion were enhanced with the addition of RT, indicating that Plk1 represents an important potential radiation sensitizer for HNSCC.

Abstract SSY01-03: An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer

Introduction:

Head and neck cancer (HNC) is a challenging disease due to its heterogeneity and complexity. Despite continued advances in therapeutic options, treatment-associated toxicities and overall clinical outcomes have remained disappointing. Even with radiation therapy (RT), which remains the primary curative modality for HNC, the most effective regimens achieve local control rates of 50-70%, with disease free survival rates of only 30-40% for patients with locally advanced HNSCC. Thus, the development of novel strategies to enhance tumor cell killing, while minimizing damage to the surrounding normal tissues, is critical for improving cure rates with RT.

Methods:

A siRNA-based high-throughput screen (HTS) was performed for the large-scale identification of novel genes that will selectively sensitize HNC cells to ionizing radiation (IR). The Dharmacon Protein Kinase and Druggable Genome siRNA Libraries were screened using FaDu cells (human hypopharyngeal squamous cell cancer). Radiosensitizing targets were subjected to functional validation studies and in vitro characterization of mechanisms for radiosensitization. In vivo validation studies including tumor formation assays and the treatment of established HNC xenograft models were also conducted.

Results:

The HTS identified 67 target sequences with potential radiosensitizing effects; the validity of the screen was corroborated by the identification of known radiosensitizing targets (e.g. ATM, ATR, AURKA). Targets reducing the surviving fraction by >50% at 2 Gy relative to their un-irradiated counterparts were selected for further evaluation. A key regulator of the heme biosynthetic pathway was thus identified as a novel tumor-selective radiosensitizing target. Down-regulation of the enzyme plus IR induced caspase-mediated apoptosis and cell cycle arrest in vitro, while delaying tumor growth in vivo. Radiosensitization appeared to be mediated via enhancement of tumor oxidative stress from perturbation of iron homeostasis and increased reactive oxygen species production. This radiosensitizing target was significantly over-expressed in HNC patient biopsies, wherein lower pre-RT mRNA levels correlated with improved survival, suggesting that this enzyme could also be a potential predictor for radiation response. Down-regulation of the enzyme also radiosensitized several different human cancer models, while sparing normal cells.

Conclusion:

We have successfully developed an RNAi-based radiosensitizer HTS, and uncovered a key regulator of heme biosynthesis as a potent sensitizer for RT, with potentially broad implications in the management of many human malignancies.

Citation Format: Emma Ito, Shijun Yue, Eduardo H. Moriyama, Angela B. Hui, Inki Kim, Wei Shi, Nehad M. Alajez, Nirmal Bhogal, GuoHua Li, Alessandro Datti, Aaron D. Schimmer, Brian C. Wilson, Peter P. Liu, Daniel Durocher, Benjamin G. Neel, Brian O'Sullivan, Bernard Cummings, Rob Bristow, Fei-Fei Liu. An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer [abstract]. In: Proceedings of the AACR 101st Annual Meeting 2010; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr SSY01-03

Efficacy of combining GMX1777 with radiation therapy for human head and neck carcinoma

PURPOSE

Rapidly metabolizing tumor cells have elevated levels of nicotinamide phosphoribosyltransferase, an enzyme involved in NAD(+) biosynthesis, which serves as an important substrate for proteins involved in DNA repair. GMX1777, which inhibits nicotinamide phosphoribosyltransferase, was evaluated in two human head and neck cancer models in combination with radiotherapy.

EXPERIMENTAL DESIGN

Effects of GMX1777-mediated radiosensitization were examined via metabolic and cytotoxicity assays in vitro; mechanism of action, in vivo antitumor efficacy, and radiosensitization were also investigated.

RESULTS

IC(50) values of GMX1777 for FaDu and C666-1 cells were 10 and 5 nmol/L, respectively, which interacted synergistically with radiotherapy. GMX1777 induced a rapid decline in intracellular NAD(+) followed by ATP reduction associated with significant cytotoxicity. These metabolic changes were slightly increased with the addition of radiotherapy, although poly(ADP-ribose) polymerase activity was significantly reduced when GMX1777 was combined with radiotherapy, thereby accounting for the synergistic cytotoxicity of these two modalities. Systemic GMX1777 administration with local tumor radiotherapy caused complete disappearance of FaDu and C666-1 tumors for 50 and 20 days, respectively. There was also significant reduction in tumor vascularity, particularly for the more sensitive FaDu model. [(18)F]FDG-positron emission tomography/computed tomography images showed reduction in [(18)F]FDG uptake after GMX1777 administration, showing decreased glucose metabolism in vivo.

CONCLUSIONS

Our data represent the first report showing that GMX1777 plus radiotherapy is an effective therapeutic strategy for head and neck cancer, mediated via pleiotropic effects of inhibition of DNA repair and tumor angiogenesis, while sparing normal tissues. Therefore, GMX1777 combined with radiotherapy definitely warrants clinical evaluation in human head and neck cancer patients.

Therapeutic efficacy of seliciclib in combination with ionizing radiation for human nasopharyngeal carcinoma

PURPOSE

Seliciclib is a small-molecule cyclin-dependent kinase inhibitor, which has been reported to induce apoptosis and cell cycle arrest in EBV-negative nasopharyngeal carcinoma cell lines. Because most nasopharyngeal carcinoma patients harbor EBV, we proceeded to evaluate the cytotoxic effects of seliciclib in EBV-positive nasopharyngeal carcinoma models.

EXPERIMENTAL DESIGN

Cytotoxicity of seliciclib was investigated in the EBV-positive cell line C666-1 and the C666-1 and C15 xenograft models. Caspase activities and cell cycle analyses were measured by flow cytometry. Efficacy of combined treatment of seliciclib with radiation therapy was also evaluated.

RESULTS

Seliciclib caused significant cytotoxicity in the C666-1 cells in a time- and dose-dependent manner, with accumulation of cells in both sub-G(1) and G(2)-M phases, indicative of apoptosis and cell cycle arrest, respectively. Caspase-2, -3, -8, and -9 activities were all increased, with caspase-3 being the most significantly activated at 48 h after treatment. These cells also showed a reduction of Mcl-1 mRNA and protein levels. Combined treatment of seliciclib with radiation therapy showed a synergistic interaction with enhanced cytotoxicity in C666-1 cells and delayed repair of double-strand DNA breaks. For in vivo models, significant delays in tumor growth were observed for both C666-1 and C15 tumors, which were associated with enhanced apoptosis as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and immunohistochemistry analyses.

CONCLUSIONS

Seliciclib enhanced the antitumor efficacy of radiation therapy in EBV-positive nasopharyngeal carcinoma, characterized by G(2)-M arrest, and apoptosis, associated with an induction in caspase activity. This process is mediated by reduction in Mcl-1 expression and by attenuation of double-strand DNA break repair.

Hedgehog signaling promotes the degradation of tumor suppressor Sufu through the ubiquitin-proteasome pathway

Sustained Sonic hedgehog (Shh) pathway activity is associated with tumorigenesis in a wide variety of tissues. Mutational inactivation of Shh receptor Patched (Ptch) and a downstream gene Suppressor of fused (Sufu), both of which are negative regulators of the pathway, increases susceptibility to cerebellum cancer in humans and mice. Sufu is a binding partner of Shh pathway transcription factor Gli. Recent data indicate that inactivation of Sufu, through either gene targeting in mice or RNAi-mediated silencing in cultured fibroblasts, is sufficient to turn on Shh target gene expression. Here, we report that Sufu is degraded rapidly in certain cancer cells and we show that Shh signaling promotes ubiquitination of Sufu, which leads to its destruction in the proteasomes. We identified an ubiquitin attachment site on K257 of Sufu, and showed that Sufu-K257R mutant is more potent as a transcription repressor and cell growth inhibitor because of increased stability. These results indicate that Shh signaling regulates Sufu activity by inducing its turnover via the ubiquitin-proteasome system.

A novel element regulates expression of the proximal human proglucagon promoter in islet cells

The human and rat proglucagon gene proximal promoter regions have differing transcriptional activities in pancreatic islet cell lines, with 300 bases of rat proglucagon 5' flanking sequence being sufficient to support expression in rodent islet cell lines, while the homologous human sequences are transcriptionally silent. To better understand the changes in promoter activity between human and rat we have used a comparative approach and cloned promoters from diverse mammalian species and tested their transcriptional activities. Proglucagon gene proximal promoter regions from species representing three orders of mammals (rodents, artiodactyls, and carnivores) support transcription in rodent islet cell lines, while promoters from primates (human and rhesus monkey), despite significant sequence conservation, failed to drive reporter gene expression. These results suggest that nucleotide changes have occurred to the sequence of the proximal promoter region of the proglucagon gene during the evolution of primates that prevent them from supporting expression in rodent islet cell lines. Using hybrid human-rat proglucagon promoters and site-directed mutagenesis we identified a novel regulatory element in the human proglucagon proximal promoter, located between the G2 and G3 enhancer elements that is responsible for most of the difference in transcriptional activity between the human and rat proximal proglucagon promoters.

Mechanism of neuroprotective effect induced by QingKaiLing as an adjuvant drug in rabbits with E. coli bacterial meningitis

OBJECTIVE

To explore the neuroprotective effects and underlying mechanism of QingKaiLing (QKL) as an adjuvant treatment for bacterial meningitis.

METHOD

E. coli bacterial meningitis rabbits were treated with antibiotics (ampicillin) alone or in combination with QKL. The number of leukocytes and the concentration of protein in the cerebrospinal fluid (CSF) of rabbits were determined at 0, 16, and 26 hours after treatment. Brain water, sodium, potassium, and calcium contents were determined at the 26-hour time point. The level of matrix metalloproteinase-9 in the brain was also determined by Western blot.

RESULT

The average number of leukocytes and the concentration of protein in CSF of the QKL adjuvant treatment group were reduced compared with the ampicillin alone group. Brain water, sodium, and calcium contents were reduced in the QKL adjuvant treatment group. The level of MMP-9 in brain tissue was also reduced in the QKL adjuvant treatment group.

CONCLUSION

QKL adjuvant treatment alleviates the aggravated inflammatory reaction and partially protects brain tissue from antibiotic-induced injury. The mechanism of this neuroprotective effect of QKL may be due to decreased levels of Ca2+ and MMP-9 in the brain.

The effect of microstructure on the wear of cobalt-based alloys used in metal-on-metal hip implants

The influence of microstructure on the wear of cobalt-based alloys used in metal-on-metal hip implants was investigated in a boundary lubrication regime designed to represent the conditions that occurred some of the time in vivo. These cobalt-chromium-molybdenum alloys were either wrought, with a total carbon content of 0.05 or 0.23 wt %, cast with a solution-annealing procedure or simply as-cast but not solution annealed. Bars of these different alloy grades were subjected to various heat treatments to develop different microstructures. The wear was evaluated in a linear-tracking reciprocating pin-on-plate apparatus with a 25 per cent bovine serum lubricant. The wear was found to be strongly affected by the dissolved carbon content of the alloys and mostly independent of grain size or the carbide characteristics. The increased carbon in solid solution caused reductions in volumetric wear because carbon helped to stabilize a face-centred cubic crystal structure, thus limiting the amount of strain-induced transformation to a hexagonal close-packed crystal structure. Based on the observed surface twining in and around the contact zone and the potentially detrimental effect of the hexagonal close-packed phase, it was postulated that the wear of cobalt-based alloys in the present study was controlled by a deformation mechanism.

Effect of microstructure on the dry sliding friction behavior of CoCrMo alloys used in metal-on-metal hip implants

The microstructure and its effect on the friction behavior of a medical grade wrought cobalt-chromium-molybdenum (CoCrMo) alloy for surgical implants were studied in this work. In particular, the effects of compression and carbon (C) content on the above characteristics were analyzed. Increasing amounts of deformation resulted in a decrease in the number of annealing twins in the microstructures. In addition, there was an increase in the volume fraction of the hexagonal closed-packed (HCP) phase due to a strain-induced transformation (SIT) from the metastable face-centered cubic (FCC) phase. The high C (HC) alloy had a lower volume fraction of this SIT phase. Friction studies conducted on these alloys revealed a higher coefficient of friction for the HC alloy and no significant effect of SIT on the friction characteristics.