Differential impact of cytoplasmic vs. nuclear RAD51 expression on breast cancer progression and patient prognosis

RAD51 recombinase is one of the DNA damage repair proteins associated with breast cancer risk. Apart from its function to maintain genomic integrity within the cell nucleus, RAD51 localized to the cytoplasm has also been implicated in breast malignancy. However, limited information exists on the roles of cytoplasmic vs. nuclear RAD51 in breast cancer progression and patient prognosis. In the present study, the association of cytoplasmic and nuclear RAD51 with clinical outcomes of patients with breast cancer was analyzed, revealing that elevated cytoplasmic RAD51 expression was associated with breast cancer progression, including increased cancer stage, grade, tumor size, lymph node metastasis and chemoresistance, along with reduced patient survival. By contrast, elevated nuclear RAD51 expression largely had the inverse effect. Results from in vitro investigations supported the cancer‑promoting effect of RAD51, showing that overexpression of RAD51 promoted breast cancer cell growth, chemoresistance and metastatic ability, while knockdown of RAD51 repressed these malignant behaviors. The current data suggest that differential expression of subcellular RAD51 had a distinct impact on breast cancer progression and patient survival. Specifically, cytoplasmic RAD51 in contrast to nuclear RAD51 was potentially an adverse marker in breast cancer.

IL-1RA promotes oral squamous cell carcinoma malignancy through mitochondrial metabolism-mediated EGFR/JNK/SOX2 pathway

BACKGROUND

Interleukin-1 receptor antagonist (IL-1RA), a member of the IL-1 family, has diverse roles in cancer development. However, the role of IL-1RA in oral squamous cell carcinoma (OSCC), in particular the underlying mechanisms, remains to be elucidated.

METHODS

Tumor tissues from OSCC patients were assessed for protein expression by immunohistochemistry. Patient survival was evaluated by Kaplan-Meier curve analysis. Impact of differential IL-1RA expression on cultured OSCC cell lines was assessed in vitro by clonogenic survival, tumorsphere formation, soft agar colony formation, and transwell cell migration and invasion assays. Oxygen consumption rate was measured by Seahorse analyzer or multi-mode plate reader. PCR array was applied to screen human cancer stem cell-related genes, proteome array for phosphorylation status of kinases, and Western blot for protein expression in cultured cells. In vivo tumor growth was investigated by orthotopic xenograft in mice, and protein expression in xenograft tumors assessed by immunohistochemistry.

RESULTS

Clinical analysis revealed that elevated IL-1RA expression in OSCC tumor tissues was associated with increased tumor size and cancer stage, and reduced survival in the patient group receiving adjuvant radiotherapy compared to the patient group without adjuvant radiotherapy. In vitro data supported these observations, showing that overexpression of IL-1RA increased OSCC cell growth, migration/invasion abilities, and resistance to ionizing radiation, whereas knockdown of IL-1RA had largely the opposite effects. Additionally, we identified that EGFR/JNK activation and SOX2 expression were modulated by differential IL-1RA expression downstream of mitochondrial metabolism, with application of mitochondrial complex inhibitors suppressing these pathways. Furthermore, in vivo data revealed that treatment with cisplatin or metformin-a mitochondrial complex inhibitor and conventional therapy for type 2 diabetes-reduced IL-1RA-associated xenograft tumor growth as well as EGFR/JNK activation and SOX2 expression. This inhibitory effect was further augmented by combination treatment with cisplatin and metformin.

CONCLUSIONS

The current study suggests that IL-1RA promoted OSCC malignancy through mitochondrial metabolism-mediated EGFR/JNK activation and SOX2 expression. Inhibition of this mitochondrial metabolic pathway may present a potential therapeutic strategy in OSCC.

ADSCs stimulated by resistin promote breast cancer cell malignancy via CXCL5 in a breast cancer coculture model

The tumor microenvironment represents one of the main obstacles in breast cancer treatment owing to the presence of heterogeneous stromal cells, such as adipose-derived stem cells (ADSCs), that may interact with breast cancer cells and promote cancer development. Resistin is an adipocytokine associated with adverse breast cancer progression; however, its underlying mechanisms in the context of the breast tumor microenvironment remain largely unidentified. Here, we utilized a transwell co-culture model containing patient-derived ADSCs and breast cancer cell lines to investigate their potential interaction, and observed that breast cancer cells co-cultured with resistin-treated ADSCs (R-ADSCs) showed enhanced cancer cell growth and metastatic ability. Screening by proteome arrays revealed that C-X-C motif chemokine ligand 5 (CXCL5) was released in the conditioned medium of the co-culture system, and phosphorylated ERK was increased in breast cancer cells after co-culture with R-ADSCs. Breast cancer cells treated with the recombinant proteins of CXCL5 showed similarly enhanced cell migration and invasion ability as occurred in the co-culture model, whereas application of neutralizing antibodies against CXCL5 reversed these phenomena. The orthotopic xenograft in mice by breast cancer cells after co-culture with R-ADSCs had a larger tumor growth and more CXCL5 expression than control. In addition, clinical analysis revealed a positive correlation between the expression of resistin and CXCL5 in both tumor tissues and serum specimens of breast cancer patients. The current study suggests that resistin-stimulated ADSCs may interact with breast cancer cells in the tumor microenvironment via CXCL5 secretion, leading to breast cancer cell malignancy.

CD44 Mediates Oral Squamous Cell Carcinoma-Promoting Activity of MRE11 via AKT Signaling

Oral cancer is one of the highest-incidence malignancies worldwide, with the occurrence of oral squamous cell carcinoma (OSCC) being the most frequently diagnosed form. A barrier for oral cancer management may arise from tumor cells that possess properties of cancer stemness, which has been recognized as a crucial factor in tumor recurrence and metastasis. As such, understanding the molecular mechanisms underlying these tumor cells may provide insights for improving cancer treatment. MRE11 is the core protein of the RAD50/MRE11/NBS1 complex with a primary role in DNA damage repair, and it has been diversely associated with tumor development including OSCC. In this study, we aimed to investigate the engagement of CD44, a cancer stemness marker functioning in the control of cell growth and motility, in OSCC malignancy under the influence of MRE11. We found that overexpression of MRE11 enhanced CD44 expression and tumorsphere formation in OSCC cells, whereas knockdown of MRE11 reduced these phenomena. In addition, the MRE11-promoted tumorsphere formation or cell migration ability was compromised in OSCC cells carrying siRNA that targets CD44, as was the MRE11-promoted AKT phosphorylation. These were further supported by analyzing clinical samples, where higher CD44 expression was associated with lymph node metastasis. Additionally, a positive correlation between the expression of MRE11 and CD44, or that of CD44 and phosphorylated AKT, was observed in OSCC tumor tissues. Finally, the expression of CD44 was found to be higher in the metastatic lung nodules from mice receiving tail vein-injection with MRE11-overexpressing OSCC cells compared with control mice, and a positive correlation between CD44 and phosphorylated AKT was also observed in these metastatic lung nodules. Altogether, our current study revealed a previously unidentified mechanism linking CD44 and AKT in MRE11-promoted OSCC malignancy, which may shed light to the development of novel therapeutic strategies in consideration of this new pathway in OSCC.

Reduced tissue and serum resistin expression as a clinical marker for esophageal squamous cell carcinoma

Esophageal cancer is one of the most common malignancies and leading cause of cancer-associated mortality worldwide. However, the molecular mechanisms underlying esophageal cancer progression and the development of clinical tools for effective diagnosis remain unclear. Resistin, which was originally identified as an adipose tissue-secretory factor, has been associated with obesity-related diseases, including certain types of cancer. Thus, the present study aimed to investigate the expression levels of resistin in tissue and serum specimens from patients with esophageal squamous cell carcinoma (ESCC) to determine the potential biological effects of resistin on ESCC cells. The results demonstrated that both tissue and serum resistin levels were significantly lower in patients with ESCC compared with healthy controls. In addition, resistin expression was positively associated with the body mass index of patients with ESCC. In vitro studies revealed that resistin inhibited the migratory ability of ESCC cells, while having no effect on ESCC cell proliferation. Taken together, these results suggest that resistin may have the potential to be developed into a clinical marker for ESCC. However, further studies are required to investigate resistin receptor expression and determine the potential involvement of resistin-associated biological pathways, which may provide insight for future development of targeted therapies for resistin-mediated ESCC.

Visfatin Enhances Breast Cancer Progression through CXCL1 Induction in Tumor-Associated Macrophages

Visfatin, an adipocytokine highly expressed in breast tumor tissues, is associated with breast cancer progression. Recent studies showed that adipocytokines mediate tumor development through adipocytokine tumor-stromal interactions in the tumor microenvironment. This study focused on the interaction between one key stromal constituent-tumor-associated macrophages-and visfatin. Pretreatment of THP-1 and peripheral blood mononuclear cells (PBMCs) with recombinant visfatin resulted in M2-polarization determined by CD163 and CD206 expression. Indirect co-culture with visfatin-treated THP-1 (V-THP-1) promoted the viability, migration, tumorsphere formation, EMT, and stemness of breast cancer cells. Cytokine array identified an increased CXCL1 secretion in V-THP-1 conditioned medium and recombinant CXCL1 enhanced cell migration and invasion, which were abrogated by the CXCL1-neutralizing antibody. Additionally, visfatin induced pERK in THP-1 cells and clinical samples confirmed a positive CXCL1/pERK correlation. In an orthotopic mouse model, the tumor bioluminescent signal of luciferase-expressing MDA-MB-231 (Luc-MDA-MB-231) cells co-cultured with V-THP-1 and the expression of proliferation marker Ki67 were significantly higher than that co-cultured with THP-1. Furthermore, tail vein-injected Luc-MDA-MB-231 pretreated with V-PBMCs conditioned medium metastasized to lungs more frequently compared to control, and this was reversed by CXCL1 blocking antibody. In summary, this study demonstrated that visfatin enhanced breast cancer progression via pERK/CXCL1 induction in macrophages.

Extracellular Visfatin-Promoted Malignant Behavior in Breast Cancer Is Mediated Through c-Abl and STAT3 Activation

PURPOSE

Visfatin is an adipocytokine involved in cellular metabolism, inflammation, and cancer. This study investigated the roles of extracellular visfatin in breast cancer, and explored underlying mechanisms in clinical and experimental settings.

EXPERIMENTAL DESIGN

Associations of serum visfatin with clinicopathologic characteristics and patient survival were assessed with Cox regression models and Kaplan-Meier analyses. Effects of extracellular visfatin on cultured breast cancer cells were examined, followed by in vivo investigation of tumor growth and metastasis in xenograft animal models. Imatinib and Stattic were used to inhibit c-Abl and STAT3 activation, respectively.

RESULTS

Breast cancer patients with high serum visfatin levels were associated with advanced tumor stage, increased tumor size and lymph node metastasis, and poor survival. Elevated phosphorylation of c-Abl and STAT3 in breast tumor tissues were correlated with high serum visfatin levels in patients. Visfatin-promoted in vitro cell viability and metastatic capability were suppressed by imatinib (c-Abl inhibitor) and Stattic (STAT3 inhibitor). Increased in vivo cell invasiveness was observed in zebrafish xenografted with visfatin-pretreated breast cancer cells. Tumor growth and lung metastasis occurred in visfatin-administered mice xenografted with breast cancer cells. Tail vein-injected mice with visfatin-pretreated breast cancer cells showed increased lung metastasis, which was suppressed by imatinib.

CONCLUSIONS

Serum visfatin levels in breast cancer patients reveal potential prognostic values, and our findings that visfatin promoted breast cancer through activation of c-Abl and STAT3 may provide an important molecular basis for future design of targeted therapies that take into account different serum visfatin levels in breast cancer. Clin Cancer Res; 22(17); 4478-90. ©2016 AACR.

The synthetic β-nitrostyrene derivative CYT-Rx20 induces breast cancer cell death and autophagy via ROS-mediated MEK/ERK pathway

The β-nitrostyrene family has been shown to suppress cancer cell proliferation and induce programmed cell death. However, mechanisms underlying β-nitrostyrenes remain less evaluated. Here, we synthesized a β-nitrostyrene derivative, CYT-Rx20, and characterized its anticancer effect and involving mechanisms in breast cancer. We found that CYT-Rx20 arrested breast cancer cells at G2/M phase and decreased cell viability by activating the caspase cascade, accompanying with increases of poly (ADP-ribose) polymerase (PARP) cleavage and γ-H2AX expression. On the other hand, up-regulation of Beclin-1, ATG5, and LC-3 was observed in CYT-Rx20-induced autophagy, which was evidently shown by transmission electron microscopy. In addition to these, CYT-Rx20-induced breast cancer cell death, intracellular reactive oxygen species (ROS) formation and expression of phospho-ERK1/2, Beclin-1, and LC-3 were significantly reversed in the presence of N-acetyl-l-cysteine (NAC), a thiol antioxidant. Furthermore, the cytotoxicity of CYT-Rx20 was enhanced by co-treatment with the autophagy inhibitor chloroquine or bafilomycin A1, suggesting that an incomplete autophagy process could deteriorate CYT-Rx20-induced cytotoxicity. In nude mice xenograft study, CYT-Rx20 significantly reduced orthotopic tumor growth. Immunohistochemical analysis revealed elevated expression of phospho-ERK1/2 and LC-3 in tumor tissues of the mice treated with CYT-Rx20. Together, we propose that CYT-Rx20 may have potential to be further developed into a β-nitrostyrene-based anticancer compound for the treatment of breast cancer.

Identification of Id1 as a downstream effector for arsenic-promoted angiogenesis via PI3K/Akt, NF-κB and NOS signaling

Exposure to arsenic is known to be a risk factor for various types of cancer. Apart from its carcinogenic activity, arsenic also shows promoting effects on angiogenesis, a crucial process for tumor growth. Yet, the mechanism underlying arsenic-induced angiogenesis is not fully understood. In this study, we aimed at investigating the involvement of inhibitor of DNA binding 1 (Id1) and the associated signal molecules in the arsenic-mediated angiogenesis. Our initial screening revealed that treatment with low concentrations of arsenic (0.5-1 μM) led to multiple cellular responses, including enhanced endothelial cell viability and angiogenic activity as well as increased protein expression of Id1. The arsenic-induced angiogenesis was suppressed in the Id1-knocked down cells compared to that in control cells. Furthermore, arsenic-induced Id1 expression and angiogenic activity were regulated by PI3K/Akt, NF-κB, and nitric oxide synthase (NOS) signaling. In summary, our current data demonstrate for the first time that Id1 mediates the arsenic-promoted angiogenesis, and Id1 may be regarded as an antiangiogenesis target for treatment of arsenic-associated cancer.

High Id1 expression, a generally negative prognostic factor, paradoxically predicts a favorable prognosis for adjuvant paclitaxel plus cisplatin therapy in surgically treated lung cancer patients

Adjuvant chemotherapy is commonly given to surgically treated non-small-cell lung cancer (NSCLC) patients. However, the prerequisite for chemotherapy needs to be scrutinized in order to maximize the benefits to patients. In this study, we observed that NSCLC cells with high Id1 protein expression were vulnerable to the treatment of paclitaxel and cisplatin. In addition, paclitaxel and cisplatin caused Id1 protein degradation through ubiquitination. In the nude mice xenograft model, the tumor growth was reduced to a large degree in the Id1-overexpressing group upon treatment with paclitaxel and cisplatin. Furthermore, immunohistochemical staining for Id1 followed by Kaplan-Meier survival analysis showed that surgically treated NSCLC patients with high Id1 expression in primary tumor tissues had better disease-free and overall survivals after adjuvant paclitaxel and cisplatin chemotherapy. In summary, our current data suggest that Id1, a generally negative prognostic factor, predicts a favorable prognosis in the case of surgically treated NSCLC patients receiving the definitive adjuvant chemotherapy. The distinct role of Id1 reported in this study may arise from the phenomenon of Id1 dependence of NSCLC cells for survival, which renders the cancer cells additionally susceptive to the adjuvant chemotherapy with paclitaxel and cisplatin.

Abstract 434: Circulating visfatin promotes malignant cancer behavior through activation of STAT3 signaling in breast cancer

Adipocytokines are adipocyte-derived hormones which have been shown potentially associated with carcinogenesis. In this study, the role of circulating visfatin, a recently discovered adipocytokine involving in breast cancer progression, was investigated. Our data showed that the levels of serum visfatin in breast cancer patients were closely correlated with several clinicopathological characteristics including tumor stages, tumor size, and lymph node (LN) metastasis. In addition, differential association of disease recurrence and patients survival with hormone receptors such as estrogen receptor (ER), progesterone receptor (PR), and epidermal growth factor receptor 2 (Her2/Neu) were observed. Patients with high serum visfatin, especially in combination with ER- status, showed the lowest survival rate. Furthermore, high serum visfatin patients had a lower recurrence risk and better patient survival after adjuvant hormone therapy. Notably, serum visfatin was positively associated with STAT3 activation through tyrosine phosphorylation in breast cancer tissues. In agreement with the clinical observation, our in vitro data revealed that breast cancer cells treated with visfatin not only enhanced cell proliferation but also activated STAT3 and its upstream regulator, JAK1. Moreover, inhibition of STAT3 resulted in the reduced cell proliferation and invasive ability of breast cancer cells. In conclusion, we propose that high levels of circulating visfatin, probably via activation of STAT3 signaling pathway, lead to a malignant cancer progression and poor survival of breast cancer patients. Therefore, the visfatin/STAT3 pathway may constitute a valuable prognostic system for breast cancer patients. In addition, interference of the visfatin/STAT3 signaling may represent a novel therapeutic potential in the treatment of breast cancer.

Table 1. Univariate and multivariable analysis of overall survival for breast cancerVariablesItemUnivariateMultivariable†Hazard Rate Ratio95% Confidence intervalP valueHazard Rate Ratio95% Confidence intervalP valueTumor size (cm)>54.36(1.69,11.27)0.0022.13(0.79,5.74)0.1362-52.47(1.05,5.81)0.0391.68(0.70,4.05)0.245<21.001.00LN Metastasis≥23.34(1.75,6.37)<0.0012.43(1.25,4.72)0.0090-11.001.00GradeIII2.47(0.81,7.53)0.112---II1.56(0.53,4.55)0.419--I1.00-Age(y)>501.49(0.81,2.73)0.197---≤501.00-BMI(kg/m2)<241.14(0.60,2.14)0.690---≥241.00-Her2/NeuPositive1.14(0.60,2.17)0.699---Negative1.00-RadiotherapyYes1.11(0.60,2.03)0.744---No1.00-ChemotherapyYes0.89(0.41,1.93)0.774---No1.00-HormoneTherapyYes0.36(0.20,0.66)0.0010.46(0.24,0.87)0.017No1.001.00VisfatinHigh5.67(2.01,15.98)0.0013.55(1.22,10.36)0.020Low1.001.00† Variables with P values greater than 0.10 in the univariate analysis were excluded from multivariable analysis.

Citation Format: Shyng-Shiou F. Yuan, Amos C. Hung, Ming-Feng Hou. Circulating visfatin promotes malignant cancer behavior through activation of STAT3 signaling in breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 434. doi:10.1158/1538-7445.AM2014-434

Role of cystatin C in amyloid precursor protein-induced proliferation of neural stem/progenitor cells

The amyloid precursor protein (APP) is well studied for its role in Alzheimer disease. However, little is known about its normal function. In this study, we examined the role of APP in neural stem/progenitor cell (NSPC) proliferation. NSPCs derived from APP-overexpressing Tg2576 transgenic mice proliferated more rapidly than NSPCs from the corresponding background strain (C57Bl/6xSJL) wild-type mice. In contrast, NSPCs from APP knock-out (APP-KO) mice had reduced proliferation rates when compared with NSPCs from the corresponding background strain (C57Bl/6). A secreted factor, identified as cystatin C, was found to be responsible for this effect. Levels of cystatin C were higher in the Tg2576 conditioned medium and lower in the APP-KO conditioned medium. Furthermore, immunodepletion of cystatin C from the conditioned medium completely removed the ability of the conditioned medium to increase NSPC proliferation. The results demonstrate that APP expression stimulates NSPC proliferation and that this effect is mediated via an increase in cystatin C secretion.

Effects of heparin and enoxaparin on APP processing and Aβ production in primary cortical neurons from Tg2576 mice

BACKGROUND

Alzheimer's disease (AD) is caused by accumulation of Aβ, which is produced through sequential cleavage of β-amyloid precursor protein (APP) by the β-site APP cleaving enzyme (BACE1) and γ-secretase. Enoxaparin, a low molecular weight form of the glycosaminoglycan (GAG) heparin, has been reported to lower Aβ plaque deposition and improve cognitive function in AD transgenic mice.

METHODOLOGY/PRINCIPAL FINDINGS

We examined whether heparin and enoxaparin influence APP processing and inhibit Aβ production in primary cortical cell cultures. Heparin and enoxaparin were incubated with primary cortical cells derived from Tg2576 mice, and the level of APP and proteolytic products of APP (sAPPα, C99, C83 and Aβ) was measured by western blotting. Treatment of the cells with heparin or enoxaparin had no significant effect on the level of total APP. However, both GAGs decreased the level of C99 and C83, and inhibited sAPPα and Aβ secretion. Heparin also decreased the level of β-secretase (BACE1) and α-secretase (ADAM10). In contrast, heparin had no effect on the level of ADAM17.

CONCLUSIONS/SIGNIFICANCE

The data indicate that heparin and enoxaparin decrease APP processing via both α- and β-secretase pathways. The possibility that GAGs may be beneficial for the treatment of AD needs further study.

Is BACE1 a suitable therapeutic target for the treatment of Alzheimer's disease? Current strategies and future directions

Alzheimer's disease (AD) is characterized by the extracellular deposition of the β-amyloid protein (Aβ). Aβ is a fragment of a much larger precursor protein, the amyloid precursor protein (APP). Sequential proteolytic cleavage of APP by β-secretase and γ-secretase liberates Aβ from APP. The aspartyl protease BACE1 (β-site APP-cleaving enzyme 1) catalyses the rate-limiting step in the production of Aβ, and as such it is considered to be a major target for drug development in Alzheimer's disease. However, the development of a BACE1 inhibitor therapy is problematic for two reasons. First, BACE1 has been found to have important physiological roles. Therefore, inhibition of the enzyme could have toxic consequences. Second, the active site of BACE1 is relatively large, and many of the bulky compounds that are needed to inhibit BACE1 activity are unlikely to cross the blood-brain barrier. This review focuses on the structure BACE1, current therapeutic strategies based on developing active-site inhibitors, and new approaches to therapy involving targeting the expression or post-translational regulation of BACE1.

The role of Abeta-induced calcium dysregulation in the pathogenesis of Alzheimer's disease

Although many of the biochemical mechanisms which regulate production or clearance of the amyloid-beta protein (Abeta) of Alzheimer's disease (AD) are now well understood, the mechanism of Abeta neurotoxicity remains unclear. A number of studies have shown that Abeta can disrupt neuronal Ca(2+) homeostasis by inducing influx of extracellular Ca(2+) into the neuronal cytoplasm. Ca(2+) is known to play an important role in neuronal excitability, synaptic plasticity and neurotoxicity. Therefore, Abeta-induced Ca(2+) dysregulation may contribute to many of the cognitive and neuropathologic features of AD. In vitro studies show that Abeta can increase ion permeability in lipid membranes. This increased permeability is reportedly associated with the formation of artificial ion pores formed from Abeta oligomers. However, a number of other studies show that Abeta can activate endogenous ion channels on the cell surface. There is also increasing evidence that presenilin mutations alter intracellular Ca(2+) stores. It is likely that elucidation of the mechanism by which Abeta and presenilin cause Ca(2+) dysregulation in neurons will help to identify new drug targets for the treatment of AD.

Secretogranin II: a key AP-1-regulated protein that mediates neuronal differentiation and protection from nitric oxide-induced apoptosis of neuroblastoma cells

Identification of AP-1 target genes in apoptosis and differentiation has proved elusive. Secretogranin II (SgII) is a protein widely distributed in nervous and endocrine tissues, and abundant in neuroendocrine granules. We addressed whether SgII is regulated by AP-1, and if SgII is involved in neuronal differentiation or the cellular response to nitrosative stress. Nitric oxide (NO) upregulated sgII mRNA dependent on a cyclic AMP response element (CRE) in the sgII promoter, and NO stimulated SgII protein secretion in neuroblastoma cells. Upregulation of sgII mRNA, sgII CRE-driven gene expression and SgII protein synthesis/export were attenuated in cells transformed with dominant-negative c-Jun (TAM67), which became sensitized to NO-induced apoptosis and failed to undergo nerve growth factor-dependent neuronal differentiation. Stable transformation of TAM67 cells with sgII restored neuronal differentiation and resistance to NO. RNAi knockdown of sgII in cells expressing functional c-Jun abolished neuronal differentiation and rendered the cells sensitive to NO-induced apoptosis. Therefore, SgII represents a key AP-1-regulated protein that counteracts NO toxicity and mediates neuronal differentiation of neuroblastoma cells.

Elucidation of ATP-stimulated stress protein expression of RBA-2 type-2 astrocytes: ATP potentiate HSP60 and Cu/Zn SOD expression and stimulates pI shift of peroxiredoxin II

ATP has been shown to mediate stress responses in the brain. The present study examined the ATP-stimulated stress protein expression of RBA-2 type-2 astrocytes. Our results revealed that ATP stimulated HSP60 expression in a dose- and time-dependent manner. The stimulation requires a minimal ATP concentration of 500 microM and high concentration of extracellular ATP (1 mM) stimulated a significant increase of HSP60 expression from 2 to 24 h. In addition, the ATP-stimulated HSP60 expressions were inhibited by inhibitors for protein kinase C (PKC) and phospholipase D (PLD), and by antioxidants, resveratrol, and catalase. Furthermore, ATP stimulated the expression of Cu/Zn superoxide dismutase (SOD). In addition, ATP and P2X7 receptor selective agonist BzATP also decreased mitochondria membrane potential measured by flow cytometry. To further examine the proteins involving in ATP-mediated stress responses, we conducted proteomic analysis. We found that RBA-2 astrocytes possess abundant peroxiredoxin II (Prx II), an antioxidant enzyme. ATP and exogenous H2O2 stimulated Prx II shifting from oxidized form to reduced form. Thus, we concluded that ATP potentiated the expression of HSP60 and Cu/Zn SOD, and decreased mitochondria membrane potential. In addition, RBA-2 astrocytes expressed Prx II that might also serve as a protective mechanism to control the concentration of reactive oxygen species.

Roles of protein kinase C in regulation of P2X7 receptor-mediated calcium signalling of cultured type-2 astrocyte cell line, RBA-2

The role of protein kinase C (PKC) on regulation of P2X(7) receptor-mediated Ca(2+) signalling was examined on RBA-2 astrocytes. Activation of PKC decreased the receptor-mediated Ca(2+) signalling and the decrease was restored by PKC inhibitors. Down regulation of PKC also caused a decrease in the Ca(2+) signalling. Thus PKC might play a dual role on the P2X(7) receptor signalling. Successive stimulation of the P2X(7) receptor induced a gradual decline of Ca(2+) signalling but PKC inhibitors failed to restore the decline. Nevertheless, PMA stimulated translocation of PKC-alpha, -betaI, -betaII, and -gamma, but only anti-PKC-gamma co-immunoprecipitated the receptors. To examine the role of PKC-gamma, Ca(2+) signalling was measured by Ca(2+) imaging. Our results revealed that the agonist-stimulated Ca(2+) signalling were reduced in the cells that the transfection of either P2X(7) receptor or PKC-gamma morpholino antisense oligo was identified. Thus, we concluded that PKC-gamma interacted with P2X(7) receptor complex and positively regulated the receptor-mediated Ca(2+) signalling.

Regulation of type VI adenylyl cyclase by Snapin, a SNAP25-binding protein

In the present study, we used the N terminus (amino acids 1 approximately 160) of type VI adenylyl cyclase (ACVI) as bait to screen a mouse brain cDNA library and identified Snapin as a novel ACVI-interacting molecule. Snapin is a binding protein of SNAP25, a component of the SNARE complex. Co-immunoprecipitation analyses confirmed the interaction between Snapin and full-length ACVI. Mutational analysis revealed that the interaction domains of ACVI and Snapin were located within amino acids 1 approximately 86 of ACVI and 33-51 of Snapin, respectively. Co-localization of ACVI and Snapin was observed in primary hippocampal neurons. Moreover, expression of Snapin specifically eliminated protein kinase C (PKC)-mediated suppression of ACVI, but not that of cAMP-dependent protein kinase (PKA) or calcium. Mutation of the potential PKC and PKA phosphorylation sites of Snapin did not affect the ability of Snapin to reverse the PKC inhibitory effect on ACVI. Phosphorylation of Snapin by PKC or PKA therefore might not be crucial for Snapin action on ACVI. In contrast, Snapin(Delta33-51), which harbors an internal deletion of amino acids 33-51 did not affect PKC-mediated inhibition of ACVI, supporting that amino acids 33-51 of Snapin comprises the ACVI-interacting region. Consistently, Snapin exerted no effect on PKC-mediated inhibition of an ACVI mutant (ACVI-DeltaA87), which lacked the Snapin-interacting region (amino acids 1-86). Snapin thus reverses its action via direct interaction with the N terminus of ACVI. Collectively, we demonstrate herein that in addition to its association with the SNARE complex, Snapin also functions as a regulator of an important cAMP synthesis enzyme in the brain.

Endothelin-1 stimulated capacitative Ca2+ entry through ET(A) receptors of a rat brain-derived type-1 astrocyte cell line, IA-1g1

The present study demonstrated that endotheline-1 (ET-1) stimulated a biphasic (transient and sustained) increase in [Ca(2+)](i) and signaling was blocked by BQ123 and inhibited by BQ788. RT-PCR analysis revealed that ET(A) was expressed more than ET(B) mRNA-suggesting that ET(A) is the major receptor. Simply reintroducing Ca(2+) in the buffer stimulated a sustained increase in [Ca(2+)](i) and the effect was inhibited by U73122, thapsigargin (TG), miconazole and SKF96365. When measured in Ca(2+)-free buffer, the ET-1-stimulated Ca(2+) transient decreased by 73% and the reintroduction of Ca(2+) induced a large sustained increase in [Ca(2+)](i). These effects were not affected by nifedipine, but were inhibited by miconazole and SKF96365-indicating that the sustained increase in [Ca(2+)](i) mediated by ET-1 was mostly due to capacitative Ca(2+) entry (CCE). The ET-1-induced CCE was inhibited by phorbol ester (PMA) but was enhanced by GF109203X; it was also enhanced by 8-bromo-cyclic AMP (8-Br-cAMP) but was inhibited by H89. Thus, protein kinase C (PKC) negatively regulated and cAMP-dependent protein kinase (PKA) positively regulated the ET-1-mediated CCE in these cells.

The P2X(7) receptor-mediated phospholipase D activation is regulated by both PKC-dependent and PKC-independent pathways in a rat brain-derived Type-2 astrocyte cell line, RBA-2

The aim of this study was to characterize the regulatory mechanisms of the P2X(7) receptor (P2X(7)R)-mediated phospholipase D (PLD) activation in a rat brain-derived Type-2 astrocyte cell line, RBA-2. A time course study revealed that activation of P2X(7)R resulted in a choline and not phosphorylcholine formation, suggesting that activation of P2X(7)R is associated with the phosphatidylcholine-PLD (PC-PLD) in these cells. GF 109203X, a selective protein kinase C (PKC) inhibitor, partially inhibited the P2X(7)R-mediated PLD activation, while blocking the phorbol 12-myristate 13-acetate (PMA)-stimulated PLD activity. In addition, PMA synergistically activated the P2X(7)R-mediated PLD activity. Furthermore, genistein, a tyrosine kinase inhibitor, blocked the P2X(7)R-activated PLD, while KN62, a Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitor, was less effective, whereas the mitogen-activated protein kinase (MAPK) inhibitor PD98059 was ineffective. No additive inhibitory effects were found by simultaneous treatment of GF 109203X and KN62 on P2X(7)R-activated PLD. Taken together, these results demonstrate that both PKC-dependent and PKC-independent signaling pathways are involved in the regulation of P2X(7)R-mediated PLD activation. Additionally, CaMKII may participate in the PKC-dependent pathway, and tyrosine kinase may play a pivotal role on both PKC-dependent and PKC-independent pathways in the P2X(7)R-mediated PLD activation in RBA-2 cells.

Molecular phylogenetics and the classification of honey bee viruses

We present the phylogenetic relationships of several picorna-like RNA viruses found in honey bees, with respect to 13 additional plant and animal positive-strand RNA viruses. Most of the honey bee viruses fall into an unnamed family of insect RNA viruses typified by the Drosophila C virus. Different bee viruses are broadly distributed within this group, suggesting either that the ability to infect honey bees has evolved multiple times, or that these viruses are generalistic in their abilities to infect insect hosts. At least one major change in gene order has occurred among the bee viruses, based on their phylogenetic affiliations. At the amino-acid level, the bee viruses differed by 15-28% at three conserved loci. Most differed by greater than 50% at the RNA level, indicating that sequence-based methods for bee virus identification must be tailored to at least three different virus clades independently.

ATP-stimulated c-fos and zif268 mRNA expression is inhibited by chemical hypoxia in a rat brain-derived type 2 astrocyte cell line, RBA-2

The stimulus-transcriptional coupling during ischemia/hypoxia was examined for ATP-stimulated expression of immediate early genes (IEGs; c-fos, zif268, c-myc and nur77) in a rat brain-derived type 2 astrocyte cell line, RBA-2. Incubation of cells with 1 mM of extracellular ATP stimulated time-dependent expression of c-fos and zif268. ATP induced the largest increases in zif268 mRNA and a lesser one in c-fos mRNA. ATP also induced a slight increase in nur77 mRNA but was ineffective in inducing c-myc expression in these cells. Brief exposure of cells to potassium cyanide to simulate chemical hypoxia induced 9-fold and 7-fold transient increases in c-fos and zif268 expression, respectively, but did not affect c-myc or nur77 expression. When cyanide and ATP were added together, the expression of c-fos and zif268 expression was inhibited, and the effect was mimicked by simulating chemical hypoxia with sodium azide. To elucidate the mechanism involved, the effect of cyanide on ATP-stimulated increases in intracellular Ca(2+) concentrations, [Ca(2+)](i), and phospholipase D (PLD) activities were measured. Cyanide induced an increase in [Ca(2&plus);](i) and further enhanced the ATP-stimulated increases in [Ca(2+)](i) and PLD activities. Nevertheless, metabolic inhibitor, iodoacetate, blocked the ATP-induced c-fos and partially inhibited zif268 expression, and deprivation of cells with glucose also inhibited the ATP-induced c-fos expression. Taken together, these results demonstrate that both extracellular ATP and chemical hypoxia induce c-fos and zif268 expression in RBA-2 type 2 astrocytes. The chemical hypoxia inhibited ATP-stimulated c-fos and zif268 expression is not due to alterations in Ca(2+) and PLD signaling, and is at least partially related to metabolic disturbance in these cells.

ATP-stimulated Ca2+ influx and phospholipase D activities of a rat brain-derived type-2 astrocyte cell line, RBA-2, are mediated through P2X7 receptors

This study characterizes and examines the P2 receptor-mediated signal transduction pathway of a rat brain-derived type 2 astrocyte cell line, RBA-2. ATP induced Ca2+ influx and activated phospholipase D (PLD). The ATP-stimulated Ca2+ influx was inhibited by pretreating cells with P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), in a concentration-dependent manner. The agonist 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) stimulated the largest increases in intracellular Ca2+ concentrations ([Ca2+]i); ATP, 2-methylthioadenosine triphosphate tetrasodium, and ATPgammaS were much less effective, whereas UTP, ADP, alpha,beta-methylene-ATP, and beta,gamma-methylene-ATP were ineffective. Furthermore, removal of extracellular Mg2+ enhanced the ATP- and BzATP-stimulated increases in [Ca2+]i. BzATP stimulated PLD in a concentration- and time-dependent manner that could be abolished by removal of extracellular Ca2+ and was inhibited by suramin, PPADS, and oxidized ATP. In addition, PLD activities were activated by the Ca2+ mobilization agent, ionomycin, in an extracellular Ca2+ concentration-dependent manner. Both staurosporine and prolonged phorbol ester treatment inhibited BzATP-stimulated PLD activity. Taken together, these data indicate that activation of the P2X7 receptors induces Ca2+ influx and stimulates a Ca2+-dependent PLD in RBA-2 astrocytes. Furthermore, protein kinase C regulates this PLD.

Error-resilient pyramid vector quantization for image compression

Pyramid vector quantization (PVQ) uses the lattice points of a pyramidal shape in multidimensional space as the quantizer codebook. It is a fixed-rate quantization technique that can be used for the compression of Laplacian-like sources arising from transform and subband image coding, where its performance approaches the optimal entropy-coded scalar quantizer without the necessity of variable length codes. In this paper, we investigate the use of PVQ for compressed image transmission over noisy channels, where the fixed-rate quantization reduces the susceptibility to bit-error corruption. We propose a new method of deriving the indices of the lattice points of the multidimensional pyramid and describe how these techniques can also improve the channel noise immunity of general symmetric lattice quantizers. Our new indexing scheme improves channel robustness by up to 3 dB over previous indexing methods, and can be performed with similar computational cost. The final fixed-rate coding algorithm surpasses the performance of typical Joint Photographic Experts Group (JPEG) implementations and exhibits much greater error resilience.

Multidimensional rotations for robust quantization of image data

Laplacian and generalized Gaussian data arise in the transform and subband coding of images. This paper describes a method of rotating independent, identically distributed (i.i.d.) Laplacian-like data in multiple dimensions to significantly improve the overload characteristics for quantization. The rotation is motivated by the geometry of the Laplacian probability distribution, and can be achieved with only additions and subtractions using a Walsh-Hadamard transform. Its theoretical and simulated results for scalar, lattice, and polar quantization are presented in this paper, followed by a direct application to image compression. We show that rotating the image data before quantization not only improves compression performance, but also increases robustness to the channel noise and deep fades often encountered in wireless communication.

Insemination-induced histolysis of the flight musculature in fire ants (Solenopsis, spp.): an ultrastructural study (1)

The fine structure of the insemination-induced flight muscle degeneration (histolysis) in the queen fire ant (Solenopsis spp.) has been investigated. Within 2 hours post-insemination, degenerative changes are detectable in the most peripheral fasciculi of the fibrillar flight muscle. Histolysis proceeds internally with time. Myofibril (sarcomere) dissolution begins with myofilament breakdown and continues until only free Z-line material remains. The latter subsequently disappears leaving, at the terminal stages, only nuclei, lamellar bodies (myelin figures), and tracheoles as residual myoid elements. Lysosomes and/or phagocytes do not appear to play a primary role in the initiation and continuance of this process.

Interspecific Hybridization and Caste Specificity of Protein in Fire Ant

One natural population of fire ant in Texas was found to be a hybrid between Solenopsis geminata and S. xyloni. Evidence from isozyme studies and breeding experiments is provided to demonstrate interspecific hybridization in ants. In this hybrid population, all worker ants have both parental types of nicotinamide adenine dinucleotide-malate dehydrogenase isozymes, but 95 percent of queens possess only the maternal type.