bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA Polymerase ζ Regulates Cisplatin Cytotoxicity, Mutagenicity, and The Rate of Development of Cisplatin Resistance
Authors: Wu Fang , Lin Xinjian , Okuda Tsuyoshi , Howell Stephen B. 
Published: September 2005

Abstract
DNA polymerase ζ participates in translesional bypass replication. Here we show that reduced expression of the catalytic subunit hREV3 renders human fibroblasts more sensitive to the cytotoxic effect of cisplatin, reduces their sensitivity to the ability of cisplatin exposure to generate drug resistant variants in the surviving population, and reduces the rate of emergence of resistance to cisplatin at the population level. Reduction of REV3 mRNA did not alter the rate of cisplatin adduct removal but did impair both spontaneous and cisplatin-induced extrachromosomal homologous recombination and attenuated bypass replication as reflected by reduced ability to express luciferase from a platinated plasmid. Cisplatin induced a concentration- and time-dependent increase in hREV3 mRNA. The results indicate that, following formation of cisplatin adducts in DNA, REV3 mRNA levels increase, and polymerase ζ functions to promote both cell survival and the generation of drug-resistant variants in the surviving population. We conclude that when cisplatin adducts are present in the DNA, polymerase ζ is an important contributor to cisplatin-induced genomic instability and the subsequent emergence of resistance to this chemotherapeutic agent.
Inhibition of Breast Cancer Metastasis by Selective Synthetic Polypeptide against CXCR4
Authors: Liang Zhongxing , Wu Tao , Lou Hong , Yu Xiwen , Taichman Russell S. , Lau Stephen K. , Nie Shuming , Umbreit Jay , Shim Hyunsuk 
Published: September 2005

AbstractMetastasis shares many similarities with leukocyte trafficking. Among those chemokine receptors thought to be involved in hemopoietic cell homing, stromal cell-derived factor-1 and its receptor CXC chemokine receptor-4 (CXCR4) have received considerable attention. Like hemopoietic cell homing, levels of stromal cell-derived factor-1 are high at sites of breast cancer metastasis including lymph node, lung, liver, and the marrow. Moreover, CXCR4 expression is low in normal breast tissues and high in malignant tumors, suggesting that a blockade of CXCR4 might limit tumor metastasis. We therefore investigated the role of a synthetic antagonist 14-mer peptide (TN14003) in inhibiting metastasis in an animal model. Not only was TN14003 effective in limiting metastasis of breast cancer by inhibiting migration, but it may also prove useful as a diagnostic tool to identify CXCR4 receptor-positive tumor cells in culture and tumors in paraffin-embedded clinical samples.
Activated Signal Transducer and Activator of Transcription (STAT) 3
Authors: Silver Debra L. , Naora Honami , Liu Jinsong , Cheng Wenjun , Montell Denise J. 
Published: September 2005

Abstract
Constitutive activation of the Janus-activated kinase/signal transducer and activator of transcription (STAT) pathway promotes the proliferation and survival of cancer cells in culture and is associated with various cancers, including those of the ovary. We found that constitutively activated STAT3 levels correlated with aggressive clinical behavior of ovarian carcinoma specimens. Furthermore, inhibition of STAT3 reduced the motility of ovarian cancer cells in vitro. Surprisingly, we found that activated STAT3 localized not only to nuclei but also to focal adhesions in these cells. Activated STAT3 coimmunoprecipitated with phosphorylated paxillin and focal adhesion kinase and required paxillin and Src for its localization to focal adhesions. These results suggest that Janus-activated kinase/STAT signaling may contribute to ovarian cancer cell invasiveness.
A Novel Synthetic Inhibitor of CDC25 Phosphatases
Authors: Brezak Marie-Christine , Quaranta Muriel , Mondésert Odile , Galcera Marie-Odile , Lavergne Olivier , Alby Frédéric , Cazales Martine , Baldin Véronique , Thurieau Christophe , Harnett Jeremiath , Lanco Christophe , Kasprzyk Philip G. , Prevost Gregoire P. , Ducommun Bernard 
Published: September 2005

Abstract
CDC25 dual-specificity phosphatases are essential regulators that dephosphorylate and activate cyclin-dependent kinase/cyclin complexes at key transitions of the cell cycle. CDC25 activity is currently considered to be an interesting target for the development of new antiproliferative agents. Here we report the identification of a new CDC25 inhibitor and the characterization of its effects at the molecular and cellular levels, and in animal models.
BN82002 inhibits the phosphatase activity of recombinant human CDC25A, B, and C in vitro. It impairs the proliferation of tumoral cell lines and increases cyclin-dependent kinase 1 inhibitory tyrosine phosphorylation. In synchronized HeLa cells, BN82002 delays cell cycle progression at G1-S, in S phase and at the G2-M transition. In contrast, BN82002 arrests U2OS cell cycle mostly in the G1 phase. Selectivity of this inhibitor is demonstrated: (a) by the reversion of the mitotic-inducing effect observed in HeLa cells upon CDC25B overexpression; and (b) by the partial reversion of cell cycle arrest in U2OS expressing CDC25. We also show that BN82002 reduces growth rate of human tumor xenografts in athymic nude mice.
BN82002 is a original CDC25 inhibitor that is active both in cell and animal models. This greatly reinforces the interest in CDC25 as an anticancer target.
Bryostatin-1 Enhances the Maturation and Antigen-Presenting Ability of Murine and Human Dendritic Cells
Authors: Do Yoonkyung , Hegde Venkatesh L. , Nagarkatti Prakash S. , Nagarkatti Mitzi 
Published: September 2005

Abstract
In this study, we investigated the effect of bryostatin-1 (Bryo-1), an antineoplastic agent, on dendritic cell (DC) maturation, activation, and functions. Murine bone marrow-derived DCs on culture with Bryo-1 alone, Bryo-1 + calcium ionophore (CI), but not CI alone exhibited morphologic changes characteristic of mature DCs and expressed increased levels of CD40, CD80, and CD86. Moreover, Bryo-1 + CI–treated DCs exhibited enhanced antigen-presenting ability to naive and antigen-specific T cells and alloreactive T cells. Bryo-1 + CI–mediated activation of DCs involved protein kinase C (PKC), especially PKC-α, -δ, and -ι, and addition of PKC inhibitors impaired their ability to activate T cells. Bryo-1 + CI treatment of DCs did not activate mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase, p38 MAPK, or stress-activated protein kinase/c-Jun NH2-terminal kinase pathways. Finally, treatment of DCs with Bryo-1 alone and Bryo-1 + CI, but not CI alone, induced nuclear translocation of nuclear factor κB as studied by confocal microscopy. DCs generated from human peripheral blood monocytes or from human cord blood CD34+ hematopoietic stem cells, when cultured with Bryo-1 + CI, also showed maturation and increased T-cell stimulatory activity. Bryo-1 + CI was more potent in inducing maturation and activation of DCs when compared with other agents such as tumor necrosis factor α, lipopolysaccharide, or phorbol 12-myristate 13acetate + CI. Collectively, the current study shows for the first time that Bryo-1 alone or in combination with CI may promote the maturation of DCs and therefore may be useful in development of DC-based cancer immunotherapy.
Fluoxetine Inhibits Multidrug Resistance Extrusion Pumps and Enhances Responses to Chemotherapy in Syngeneic and in Human Xenograft Mouse Tumor Models
Authors: Peer Dan , Dekel Yaron , Melikhov Dina , Margalit Rimona 
Published: September 2005

Abstract
Multidrug resistance (MDR) operated by extrusion pumps such as P-glycoprotein and multidrug-resistance-associated-proteins, is a major reason for poor responses and failures in cancer chemotherapy. MDR modulators (chemosensitizers) were found among drugs approved for noncancer indications and their derivatives. Yet toxicity, adverse effects, and poor solubility at doses required for MDR reversal prevent their clinical application. Among newly designed chemosensitizers, some still suffer from toxicity and adverse effects, whereas others progressed to clinical trials. Diversities among tumors and among MDR pumps indicate a need for several clinically approved MDR modulators. Here we report for the first time that fluoxetine (Prozac), the well-known antidepressant, is a highly effective chemosensitizer. In vitro, fluoxetine enhanced (10- to 100-fold) cytotoxicity of anticancer drugs (doxorubicin, mitomycin C, vinblastine, and paclitaxel) in drug-resistant but not in drug-sensitive cells (5 and 3 lines, respectively). Fluoxetine increased drug accumulation within MDR-cells and inhibited drug efflux from those cells. In vivo, fluoxetine enhanced doxorubicin accumulation within tumors (12-fold) with unaltered pharmacokinetics. In four resistant mouse tumor models of both syngeneic and human xenograft, combination treatment of fluoxetine and doxorubicin generated substantial (P &lt; 0.001) improvements in tumor responses and in survivals (2- to 3-fold). Moreover, fluoxetine reversed MDR at doses that are well below its human safety limits, free of the severe dose-related toxicity, adverse effects, and poor solubility that are obstacles to other chemosensitizers. This low-dose range, together with the findings reported here, indicate that fluoxetine has a high potential to join the arsenal of MDR reversal agents that may reach the clinic.
A Mouse Skin Multistage Carcinogenesis Model Reflects the Aberrant DNA Methylation Patterns of Human Tumors
Authors: Fraga Mario F. , Herranz Michel , Espada Jesús , Ballestar Esteban , Paz Maria F. , Ropero Santiago , Erkek Emel , Bozdogan Onder , Peinado Héctor , Niveleau Alain , Mao Jian-Hua , Balmain Alan , Cano Amparo , Esteller Manel 
Published: September 2005

Abstract
Whereas accepted models of tumorigenesis exist for genetic lesions, the timing of epigenetic alterations in cancer is not clearly understood. We have analyzed the profile of aberrations in DNA methylation occurring in cells lines and primary tumors of one of the best-characterized mouse carcinogenesis systems, the multistage skin cancer progression model. Initial analysis using high-performance capillary electrophoresis and immunolocalization revealed a loss of genomic 5-methylcytosine associated with the degree of tumor aggressiveness. Paradoxically, this occurs in the context of a growing number of hypermethylated CpG islands of tumor suppressor genes at the most malignant stages of carcinogenesis. We have observed this last phenomenon using two approaches, a candidate gene approach, studying genes with well-known methylation-associated silencing in human tumors, and a mouse cDNA microarray expression analysis after treatment with DNA demethylating drugs. The transition from epithelial to spindle cell morphology is particularly associated with major epigenetic alterations, such as E-cadherin methylation, demethylation of the Snail promoter, and a decrease of the global DNA methylation. Analysis of data obtained from the cDNA microarray strategy led to the identification of new genes that undergo methylation-associated silencing and have growth-inhibitory effects, such as the insulin-like growth factor binding protein-3. Most importantly, all of the above genes were also hypermethylated in human cancer cell lines and primary tumors, underlining the value of the mouse skin carcinogenesis model for the study of aberrant DNA methylation events in cancer cells.
Mechanism of the Pharmacokinetic Interaction between Methotrexate and Benzimidazoles
Authors: Breedveld Pauline , Zelcer Noam , Pluim Dick , Sönmezer Özgür , Tibben Matthijs M. , Beijnen Jos H. , Schinkel Alfred H. , van Tellingen Olaf , Borst Piet , Schellens Jan H. M. 
Published: September 2005

Abstract
The antifolate drug methotrexate (MTX) is transported by breast cancer resistance protein (BCRP; ABCG2) and multidrug resistance-associated protein1–4 (MRP1–4; ABCC1–4). In cancer patients, coadministration of benzimidazoles and MTX can result in profound MTX-induced toxicity coinciding with an increase in the serum concentrations of MTX and its main metabolite 7-hydroxymethotrexate. We hypothesized that benzimidazoles interfere with the clearance of MTX and/or 7-hydroxymethotrexate by inhibition of the ATP-binding cassette drug transporters BCRP and/or MRP2, two transporters known to transport MTX and located in apical membranes of epithelia involved in drug disposition. First, we investigated the mechanism of interaction between benzimidazoles (pantoprazole and omeprazole) and MTX in vitro in membrane vesicles from Sf9 cells infected with a baculovirus containing human BCRP or human MRP2 cDNA. In Sf9-BCRP vesicles, pantoprazole and omeprazole inhibited MTX transport (IC50 13 μm and 36 μm, respectively). In Sf9-MRP2 vesicles, pantoprazole did not inhibit MTX transport and at high concentrations (1 mm), it even stimulated MTX transport 1.6-fold. Secondly, we studied the transport of pantoprazole in MDCKII monolayers transfected with mouse Bcrp1 or human MRP2. Pantoprazole was actively transported by Bcrp1 but not by MRP2. Finally, the mechanism of the interaction was studied in vivo using Bcrp1−/− mice and wild-type mice. Both in wild-type mice pretreated with pantoprazole to inhibit Bcrp1 and in Bcrp1−/− mice that lack Bcrp1, the clearance of i.v. MTX was decreased significantly 1.8- to 1.9-fold compared with the clearance of i.v. MTX in wild-type mice. The conclusion is as follows: benzimidazoles differentially affect transport of MTX mediated by BCRP and MRP2. Competition for BCRP may explain the clinical interaction between MTX and benzimidazoles.
From the Cyclooxygenase-2 Inhibitor Celecoxib to a Novel Class of 3-Phosphoinositide-Dependent Protein Kinase-1 Inhibitors
Authors: Zhu Jiuxiang , Huang Jui-Wen , Tseng Ping-Hui , Yang Ya-Ting , Fowble Joseph , Shiau Chung-Wai , Shaw Yeng-Jeng , Kulp Samuel K. , Chen Ching-Shih 
Published: September 2005

Abstract
The blockade of Akt activation through the inhibition of 3-phosphoinositide-dependent kinase-1 (PDK-1) represents a major signaling mechanism whereby celecoxib mediates apoptosis. Celecoxib, however, is a weak PDK-1 inhibitor (IC50, 48 μm), requiring at least 30 μm to exhibit discernable effects on the growth of tumor cells in vitro. Here, we report the structure-based optimization of celecoxib to develop PDK-1 inhibitors with greater potency in enzyme inhibition and growth inhibition. Kinetics of PDK-1 inhibition by celecoxib with respect to ATP suggest that celecoxib derivatives inhibit PDK-1 by competing with ATP for binding, a mechanism reminiscent to that of many kinase inhibitors. Structure-activity analysis together with molecular modeling was used to generate compounds that were tested for their potency in inhibiting PDK-1 kinase activity and in inducing apoptosis in PC-3 prostate cancer cells. Docking of potent compounds into the ATP-binding site of PDK-1 was performed for lead optimization, leading to two compounds, OSU-03012 and OSU-03013, with IC50 values in PDK-1 inhibition and apoptosis induction in the low μm range. Exposure of PC-3 cells to these agents led to Akt dephosphorylation and inhibition of p70 S6 kinase activity. Moreover, overexpression of constitutively active forms of PDK-1 and Akt partially protected OSU-03012-induced apoptosis. Screening in a panel of 60 cell lines and more extensive testing in PC-3 cells indicated that the mean concentration for total growth inhibition was ∼3 μm for both agents. Considering the conserved role of PDK-1/Akt signaling in promoting tumorigenesis, these celecoxib analogs are of translational relevance for cancer prevention and therapy.
Reduced Infiltration of Class A Scavenger Receptor Positive Antigen-Presenting Cells Is Associated with Prostate Cancer Progression
Authors: Yang Guang , Addai Josephine , Tian Wei-hua , Frolov Anna , Wheeler Thomas M. , Thompson Timothy C. 
Published: September 2005

Abstract
The class A macrophage scavenger receptor (SR-A) is expressed in antigen presenting cells and is involved in host immune responses. Germ-line mutation of this gene has been associated with increased risk of human prostate cancer. However, there is little known about its expression in normal or neoplastic human prostate tissues. Double immunofluorescent labeling with monoclonal antibodies to SR-A and specific macrophage and dendritic cell markers was used to identify cells expressing SR-A in human prostate tissues. SR-A immunohistochemical staining was performed on paraffin sections of normal prostate, prostatic intraepithelial neoplasia (PIN) lesions, and prostate cancers from radical prostatectomy specimens. SR-A was expressed in a subset of macrophages and dendritic cells that infiltrated prostatic tissues. The majority of SR-A-positive cells coexpressed CD68, and a relatively low percentage expressed S100 protein. The number of SR-A-positive cells was significantly increased in PIN as compared with normal prostatic tissue (P = 0.0176). In contrast, the number of SR-A-positive cells decreased with tumor progression. A lower SR-A-positive cell density was associated with higher clinical stage (ρ = −0.26; P = 0.0234). Inverse associations were also found between SR-A density and positive lymph nodes (ρ = −0.23; P = 0.0437), tumor size (ρ = −0.31; P = 0.0100) and preoperative PSA levels (ρ = −0.32; P = 0.0057). SR-A density is a significant predictor of disease-free survival after surgery univariately (P = 0.0003), as well as multivariately, adjusted for known clinical and pathological markers including preoperative prostate-specific antigen, clinical stage, Gleason score, surgical margin, extraprostatic extension, and seminal vesicle invasion, as well as lymph node metastasis (P = 0.0021). The preferential accumulation of SR-A-positive cells in PIN suggests a role for SR-A in the APC response to early malignancy. A reduction in the number of SR-A-positive cells demarcates tumor progression as indicated by clinical and pathological correlations. Our results additionally indicate that systematic measurement of SR-A density is a strong prognostic marker for clinical outcome after surgery.
Hypermethylation of a Small CpGuanine-Rich Region Correlates with Loss of Activator Protein-2α Expression during Progression of Breast Cancer
Authors: Douglas Donna B. , Akiyama Yoshimitsu , Carraway Hetty , Belinsky Steven A. , Esteller Manel , Gabrielson Edward , Weitzman Sigmund , Williams Trevor , Herman James G. , Baylin Stephen B. 
Published: September 2005

Abstract
The transcription factor activator protein-2α (AP-2α) has recently been implicated as a tumor suppressor protein that can be lost during tumor progression and that exhibits growth-inhibitory properties when overexpressed in cancer cell lines. We now demonstrate that hypermethylation of a discrete 5′ region within a promoter CpG island of the gene is associated in breast cancer with the loss of AP-2α expression. Multiple CpG sites within the island become hypermethylated during breast cancer evolution. However, only hypermethylation of the most CpG-rich region, a small, ∼300-bp area at the 3′ end of exon 1, fully distinguishes neoplastic from normal breast tissue and correlates with transcriptional silencing. In cell culture, silenced AP-2α, associated with exon 1 hypermethylation, is re-expressed by 5-aza-2′deoxycytidine resulting in the restoration of a functional DNA sequence-specific binding protein. In vivo, as detected by a very sensitive nested PCR approach, methylation of the discrete AP-2α exon 1 region does not occur in normal breast epithelium and occurs in only 3 (16%) of 19 ductal carcinoma in situ (DCIS) lesions, but is present in 12 (75%) of 16 invasive breast tumors (P &lt; 0.001; DCIS versus invasive cancers). Tumors unmethylated for this region expressed AP-2α protein throughout, whereas tumors with hypermethylation showed large areas of loss. Our studies then determine that hypermethylation of a small region of a CpG island correlates with silencing of AP-2α in breast cancer and suggest that inactivation of this gene could be a factor in, and a useful marker for, the progression of DCIS lesions.
Targeting Endogenous Transforming Growth Factor β Receptor Signaling in SMAD4-Deficient Human Pancreatic Carcinoma Cells Inhibits Their Invasive Phenotype
Authors: Subramanian Gayathri , Schwarz Roderich E. , Higgins Linda , McEnroe Glenn , Chakravarty Sarvajit , Dugar Sundeep , Reiss Michael 
Published: September 2005

Abstract
Transforming growth factor-β (TGF-β) suppresses tumor formation by blocking cell cycle progression and maintaining tissue homeostasis. In pancreatic carcinomas, this tumor suppressive activity is often lost by inactivation of the TGF-β-signaling mediator, Smad4. We found that human pancreatic carcinoma cell lines that have undergone deletion of MADH4 constitutively expressed high endogenous levels of phosphorylated receptor-associated Smad proteins (pR-Smad2 and pR-Smad3), whereas Smad4-positive lines did not. These elevated pR-Smad levels could not be attributed to a decreased dephosphorylation rate nor to increased expression of TGF-β type I (TβR-I) or type II (TβR-II) receptors. Although minimal amounts of free bioactive TGF-β1 and TGF-β2 were detected in conditioned medium, treatment with a pan-specific (but not a TGF-β3 specific) TGF-β-neutralizing antibody and with anti-αVβ6 integrin antibody decreased steady-state pSmad2 levels and activation of a TGF-β-inducible reporter gene in neighboring cells, respectively. Thus, activation of TGF-β at the cell surface was responsible for the increased autocrine endogenous and paracrine signaling. Blocking TβR-I activity using a selective kinase inhibitor (SD-093) strongly decreased the in vitro motility and invasiveness of the pancreatic carcinoma cells without affecting their growth characteristics, morphology, or the subcellular distribution of E-cadherin and F-actin. Moreover, exogenous TGF-β strongly stimulated in vitro invasiveness of BxPC-3 cells, an effect that could also be blocked by SD-093. Thus, the motile and invasive properties of Smad4-deficient pancreatic cancer cells are at least partly driven by activation of endogenous TGF-β signaling. Therefore, targeting the TβR-I kinase represents a potentially powerful novel therapeutic approach for the treatment of this disease.
Galectin-1(L11A) Predicted from a Computed Galectin-1 Farnesyl-Binding Pocket Selectively Inhibits Ras-GTP
Authors: Rotblat Barak , Niv Hagit , André Sabine , Kaltner Herbert , Gabius Hans-Joachim , Kloog Yoel 
Published: September 2005

Abstract
Ras biological activity necessitates membrane anchorage that depends on the Ras farnesyl moiety and is strengthened by Ras/galectin-1 interactions. We identified a hydrophobic pocket in galectin-1, analogous to the Cdc42 geranylgeranyl-binding cavity in RhoGDI, possessing homologous isoprenoid-binding residues, including the critical L11, whose RhoGDI L77 homologue changes dramatically on Cdc42 binding. By substituting L11A, we obtained a dominant interfering galectin-1 that possessed normal carbohydrate-binding capacity but inhibited H-Ras GTP-loading and extracellular signal-regulated kinase activation, dislodged H-Ras(G12V) from the cell membrane, and attenuated H-Ras(G12V) fibroblast transformation and PC12-cell neurite outgrowth. Thus, independently of carbohydrate binding, galectin-1 cooperates with Ras, whereas galectin-1(L11A) inhibits it.