bluuebunny/crossref_metadata_2025 huggingface dataset:
ClC-3 expression enhances etoposide resistance by increasing acidification of the late endocytic compartment
Authors: Weylandt Karsten H. , Nebrig Maxim , Jansen-Rosseck Nils , Amey Joanna S. , Carmena David , Wiedenmann Bertram , Higgins Christopher F. , Sardini Alessandro
Published: March 2007

Resistance to anticancer drugs and consequent failure of chemotherapy is a complex problem severely limiting therapeutic options in metastatic cancer. Many studies have shown a role for drug efflux pumps of the ATP-binding cassette transporters family in the development of drug resistance. ClC-3, a member of the CLC family of chloride channels and transporters, is expressed in intracellular compartments of neuronal cells and involved in vesicular acidification. It has previously been suggested that acidification of intracellular organelles can promote drug resistance by increasing drug sequestration. Therefore, we hypothesized a role for ClC-3 in drug resistance. Here, we show that ClC-3 is expressed in neuroendocrine tumor cell lines, such as BON, LCC-18, and QGP-1, and localized in intracellular vesicles colabeled with the late endosomal/lysosomal marker LAMP-1. ClC-3 overexpression increased the acidity of intracellular vesicles, as assessed by acridine orange staining, and enhanced resistance to the chemotherapeutic drug etoposide by almost doubling the IC50 in either BON or HEK293 cell lines. Prevention of organellar acidification, by inhibition of the vacuolar H+-ATPase, reduced etoposide resistance. No expression of common multidrug resistance transporters, such as P-glycoprotein or multidrug-related protein-1, was detected in either the BON parental cell line or the derivative clone overexpressing ClC-3. The probable mechanism of enhanced etoposide resistance can be attributed to the increase of vesicular acidification as consequence of ClC-3 overexpression. This study therefore provides first evidence for a role of intracellular CLC proteins in the modulation of cancer drug resistance. [Mol Cancer Ther 2007;6(3):979–86]
Protein kinase CK2 modulates apoptosis induced by resveratrol and epigallocatechin-3-gallate in prostate cancer cells
Authors: Ahmad Kashif A. , Harris Nathan H. , Johnson Andrew D. , Lindvall Hans C.N. , Wang Guixia , Ahmed Khalil
Published: March 2007

Resveratrol and epigallocatechin-3-gallate (EGCG) are important candidates as chemopreventive agents by virtue of their ability to induce apoptosis in cancer cells. Casein kinase 2 (CK2) is a ubiquitous protein ser/thr kinase that plays diverse roles in cell proliferation and apoptosis. We have previously shown that overexpression of CK2 suppresses apoptosis induced by a variety of agents, whereas down-regulation of CK2 sensitizes cells to induction of apoptosis. We therefore investigated whether or not CK2 played a role in resveratrol and EGCG signaling in androgen-sensitive (ALVA-41) and androgen-insensitive (PC-3) prostate cancer cells. Resveratrol- and EGCG-induced apoptosis is associated with a significant down-regulation of CK2 activity and protein expression in both the ALVA-41 and PC-3 cells. Overexpression of CK2α protected prostatic cancer cells against resveratrol- and EGCG-induced apoptosis. Relatively low doses (10 μmol/L) of resveratrol and EGCG induced a modest proliferative response in cancer cells that could be switched to cell death by moderate inhibition of CK2. These findings characterize, for the first time, the effects of polyphenolic compounds on CK2 signaling in androgen-sensitive and androgen-insensitive prostatic carcinoma cells and suggest that resveratrol and EGCG may mediate their cellular activity, at least in part, via their targeting of CK2. Further, the data hint at the potential of using these polyphenols alongside CK2 inhibitors in combination chemotherapy. [Mol Cancer Ther 2007;6(3):1006–12]
A coordinated action of Bax, PUMA, and p53 promotes MG132-induced mitochondria activation and apoptosis in colon cancer cells
Authors: Ding Wen-Xing , Ni Hong-Min , Chen Xiaoyun , Yu Jian , Zhang Lin , Yin Xiao-Ming
Published: March 2007

Targeting the ubiquitin-proteasome degradation pathway has become a promising approach for cancer therapy. Previous studies have shown that proteasome inhibition leads to apoptosis in various cancer cells. The mechanism by which apoptosis occurs are not fully understood and can be cell type and/or inhibitor specific. In this study, we investigated the mechanism of mitochondrial activation by proteasome inhibitors in colon cancer cells. We found that Bax activation and mitochondria translocation were required for apoptosis induced by multiple proteasome inhibitors. In contrast, reactive oxygen species did not seem to be induced by MG132 or bortezomib and antioxidants had no effects on MG132-induced apoptosis. In contrast, treatment with MG132 or bortezomib induced a significant accumulation of p53 and PUMA. Genetic deletion of either p53 or PUMA led to a marked suppression of apoptosis induced by these inhibitors, accompanied with reduced Bax activation and cytochrome c release. Consistently, inhibition of translation by cycloheximide could also effectively abolish the accumulation of p53 and PUMA and suppress MG132-induced Bax activation and apoptosis. These findings thus strongly indicate the critical involvement of p53-, PUMA-, and Bax-mediated mitochondrial activation in proteasome inhibitor–induced apoptosis in colon cancer cells. [Mol Cancer Ther 2007;6(3):1062–9]
Preclinical selection of a novel poly(ADP-ribose) polymerase inhibitor for clinical trial
Authors: Thomas Huw D. , Calabrese Christopher R. , Batey Michael A. , Canan Stacie , Hostomsky Zdenek , Kyle Suzanne , Maegley Karen A. , Newell David R. , Skalitzky Donald , Wang Lan-Zhen , Webber Stephen E. , Curtin Nicola J.
Published: March 2007

Poly(ADP-ribose) polymerase (PARP)-1 (EC 2.4.2.30) is a nuclear enzyme that promotes the base excision repair of DNA breaks. Inhibition of PARP-1 enhances the efficacy of DNA alkylating agents, topoisomerase I poisons, and ionizing radiation. Our aim was to identify a PARP inhibitor for clinical trial from a panel of 42 potent PARP inhibitors (Ki, 1.4–15.1 nmol/L) based on the quinazolinone, benzimidazole, tricyclic benzimidazole, tricyclic indole, and tricyclic indole-1-one core structures. We evaluated chemosensitization of temozolomide and topotecan using LoVo and SW620 human colorectal cells; in vitro radiosensitization was measured using LoVo cells, and the enhancement of antitumor activity of temozolomide was evaluated in mice bearing SW620 xenografts. Excellent chemopotentiation and radiopotentiation were observed in vitro, with 17 of the compounds causing a greater temozolomide and topotecan sensitization than the benchmark inhibitor AG14361 and 10 compounds were more potent radiosensitizers than AG14361. In tumor-bearing mice, none of the compounds were toxic when given alone, and the antitumor activity of the PARP inhibitor-temozolomide combinations was unrelated to toxicity. Compounds that were more potent chemosensitizers in vivo than AG14361 were also more potent in vitro, validating in vitro assays as a prescreen. These studies have identified a compound, AG14447, as a PARP inhibitor with outstanding in vivo chemosensitization potency at tolerable doses, which is at least 10 times more potent than the initial lead, AG14361. The phosphate salt of AG14447 (AG014699), which has improved aqueous solubility, has been selected for clinical trial. [Mol Cancer Ther 2007;6(3):945–56]
Biochemical and cellular characterization of VRX0466617, a novel and selective inhibitor for the checkpoint kinase Chk2
Authors: Carlessi Luigi , Buscemi Giacomo , Larson Gary , Hong Zhi , Wu Jim Zhen , Delia Domenico
Published: March 2007

VRX0466617 is a novel selective small-molecule inhibitor for Chk2 discovered through a protein kinase screening program. In this study, we provide a detailed biochemical and cellular characterization of VRX0466617. We show that VRX0466617 blocks the enzymatic activity of recombinant Chk2, as well as the ionizing radiation (IR)–induced activation of Chk2 from cells pretreated with the compound, at doses between 5 and 10 μmol/L. These doses of VRX0466617 inhibited, to some extent, the phosphorylation of Chk2 Ser19 and Ser33–35, but not of Chk2 Thr68, which is phosphorylated by the upstream ataxia-telangiectasia mutated (ATM) kinase. Interestingly, VRX0466617 induced the phosphorylation of Chk2 Thr68 even in the absence of DNA damage, arising from the block of its enzymatic activity. VRX0466617 prevented the IR-induced Chk2-dependent degradation of Hdmx, concordant with the in vivo inhibition of Chk2. Analysis of ATM/ATM and Rad3-related substrates Smc1, p53, and Chk1 excluded a cross-inhibition of these kinases. VRX0466617 did not modify the cell cycle phase distribution, although it caused an increase in multinucleated cells. Whereas VRX0466617 attenuated IR-induced apoptosis, in short-term assays it did not affect the cytotoxicity by the anticancer drugs doxorubicin, Taxol, and cisplatin. These results underscore the specificity of VRX0466617 for Chk2, both in vitro and in vivo, and support the use of this compound as a biological probe to study the Chk2-dependent pathways. [Mol Cancer Ther 2007;6(3):935–44]
The glycotope-specific RAV12 monoclonal antibody induces oncosis in vitro and has antitumor activity against gastrointestinal adenocarcinoma tumor xenografts in vivo
Authors: Loo Deryk , Pryer Nancy , Young Peter , Liang Tony , Coberly Suzanne , King Kathleen L. , Kang Key , Roberts Penny , Tsao Mary , Xu Xiaolin , Potts Beverly , Mather Jennie P.
Published: March 2007

RAV12 is a chimeric antibody that recognizes an N-linked carbohydrate antigen (RAAG12) strongly expressed on multiple solid organ cancers. More than 90% of tumors of colorectal, gastric, and pancreatic origin express RAAG12, and a majority of these tumors exhibit uniform RAAG12 expression. RAV12 exhibits potent cytotoxic activity in vitro against COLO 205 colon tumor cells via an oncotic cell death mechanism. RAV12-treated COLO 205 cells undergo morphologic changes consistent with oncosis, including cytoskeletal rearrangement, rapid plasma membrane swelling, and cell lysis. RAV12 inhibited the growth of RAAG12-expressing gastrointestinal tumor xenografts in athymic mice. In the case of SNU-16 tumor cells, twice weekly treatment of established s.c. tumors with 10 mg/kg RAV12 caused a ∼70% suppression of tumor growth at the end of the study. This preclinical data has led to the initiation of a phase I/IIA clinical study of RAV12 in patients with metastatic or recurrent adenocarcinoma. [Mol Cancer Ther 2007;6(3):856–65]
Radiation-induced cell signaling: inside-out and outside-in
Authors: Valerie Kristoffer , Yacoub Adly , Hagan Michael P. , Curiel David T. , Fisher Paul B. , Grant Steven , Dent Paul
Published: March 2007

Exposure of tumor cells to clinically relevant doses of ionizing radiation causes DNA damage as well as mitochondria-dependent generation of reactive oxygen species. DNA damage causes activation of ataxia telangiectasia mutated and ataxia telangiectasia mutated and Rad3-related protein, which induce cell cycle checkpoints and also modulate the activation of prosurvival and proapoptotic signaling pathways, such as extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun NH2-terminal kinase 1/2, respectively. Radiation causes a rapid reactive oxygen species–dependent activation of ERBB family and other tyrosine kinases, leading to activation of RAS proteins and multiple protective downstream signaling pathways (e.g., AKT and ERK1/2), which alter transcription factor function and the apoptotic threshold of cells. The initial radiation-induced activation of ERK1/2 can promote the cleavage and release of paracrine ligands, which cause a temporally delayed reactivation of receptors and intracellular signaling pathways in irradiated and unirradiated bystander cells. Hence, signals from within the cell can promote activation of membrane-associated receptors, which signal back into the cytosol: signaling from inside the cell outward to receptors and then inward again via kinase pathways. However, cytosolic signaling can also cause release of membrane-associated paracrine factors, and thus, paracrine signals from outside of the cell can promote activation of growth factor receptors: signaling from the outside inward. The ultimate consequence of these signaling events after multiple exposures may be to reprogram the irradiated and affected bystander cells in terms of their expression levels of growth-regulatory and cell survival proteins, resulting in altered mitogenic rates and thresholds at which genotoxic stresses cause cell death. Inhibition of signaling in one and/or multiple survival pathways enhances radiosensitivity. Prolonged inhibition of any one of these pathways, however, gives rise to lineages of cells, which have become resistant to the inhibitor drug, by evolutionary selection for the clonal outgrowth of cells with point mutations in the specific targeted protein that make the target protein drug resistant or by the reprogramming of multiple signaling processes within all cells, to maintain viability. Thus, tumor cells are dynamic with respect to their reliance on specific cell signaling pathways to exist and rapidly adapt to repeated toxic challenges in an attempt to maintain tumor cell survival. [Mol Cancer Ther 2007;6(3):789–801]
In vitro and in vivo synergy of MCP compounds with mitogen-activated protein kinase pathway– and microtubule-targeting inhibitors
Authors: Skobeleva Natalia , Menon Sanjay , Weber Lutz , Golemis Erica A. , Khazak Vladimir
Published: March 2007

An important clinical task is to coherently integrate the use of protein-targeted drugs into preexisting therapeutic regimens, with the goal of improving treatment efficacy. Constitutive activation of Ras-dependent signaling is important in many tumors, and agents that inhibit this pathway might be useful in numerous therapeutic combinations. The MCP compounds were identified as inhibitors of Ras-Raf interactions and previously shown to inhibit multiple Ras-dependent transformation phenotypes when used as monoagents in cell culture analyses. In this study, we investigate the ability of the MCP110 compound to synergistically enhance the activity of other therapeutic agents. In both a defined K-Ras–transformed fibroblast model and in human tumor cell lines with mutationally activated Ras, MCP110 selectively synergizes with other agents targeting the mitogen-activated protein kinase pathway, and with multiple agents (paclitaxel, docetaxel, and vincristine) targeting the microtubule network. The synergistic activity of MCP110 and paclitaxel was further established by experiments showing that in Kaposi's sarcoma oncogenically transformed cell lines, cellular models for tumors treated with taxanes in the clinic and in which Raf-dependent signaling plays an important role, MCP110 synergizes with paclitaxel and limit growth. Finally, in vivo testing indicate that MCP110 is bioavailable, inhibits the growth of LXFA 629 lung and SW620 colon carcinoma cells in xenograft models, and again strongly synergizes with paclitaxel. Together, these findings indicate that MCP compounds have potential to be effective in combination with other anticancer agents. [Mol Cancer Ther 2007;6(3):898–906]
Emodin has a cytotoxic activity against human multiple myeloma as a Janus-activated kinase 2 inhibitor
Authors: Muto Akihiro , Hori Mayumi , Sasaki Yosuke , Saitoh Akari , Yasuda Iho , Maekawa Tadahito , Uchida Tomoe , Asakura Keiko , Nakazato Tomonori , Kaneda Toshio , Kizaki Masahiro , Ikeda Yasuo , Yoshida Tadashi
Published: March 2007

Emodin is an active component of a traditional Chinese and Japanese medicine isolated from the root and rhizomes of Rheum palmatum L. Here, we show that emodin significantly induces cytotoxicity in the human myeloma cells through the elimination of myeloid cell leukemia 1 (Mcl-1). Emodin inhibited interleukin-6–induced activation of Janus-activated kinase 2 (JAK2) and phosphorylation of signal transducer and activator of transcription 3 (STAT3), followed by the decreased expression of Mcl-1. Activation of caspase-3 and caspase-9 was triggered by emodin, but the expression of other antiapoptotic Bcl-2 family members, except Mcl-1, did not change in the presence of emodin. To clarify the importance of Mcl-1 in emodin-induced apoptosis, the Mcl-1 expression vector was introduced into the human myeloma cells by electroporation. Induction of apoptosis by emodin was almost abrogated in Mcl-1–overexpressing myeloma cells as the same level as in parental cells, which were not treated with emodin. In conclusion, emodin inhibits interleukin-6–induced JAK2/STAT3 pathway selectively and induces apoptosis in myeloma cells via down-regulation of Mcl-1, which is a good target for treating myeloma. Taken together, our results show emodin as a new potent anticancer agent for the treatment of multiple myeloma patients. [Mol Cancer Ther 2007;6(3):987–94]
The power and promise of “rewiring” the mitogen-activated protein kinase network in prostate cancer therapeutics
Authors: Papatsoris Athanasios G. , Karamouzis Michalis V. , Papavassiliou Athanasios G.
Published: March 2007

Prostate cancer is the most frequently diagnosed cancer among men and the second leading cause of male cancer deaths. Initially, tumor growth is androgen dependent and thus responsive to pharmacologic androgen deprivation, but there is a high rate of treatment failure because the disease evolves in an androgen-independent state. Growing evidence suggests that the Ras/mitogen-activated protein kinase (MAPK) signaling cascade represents a pivotal molecular circuitry participating directly or indirectly in prostate cancer evolution. The crucial role of the protein elements comprising this complex signal transduction network makes them potential targets for pharmacologic interference. Here, we will delineate the current knowledge regarding the involvement of the Ras/MAPK pathway in prostate carcinogenesis, spotlight ongoing research concerning the development of novel targeted agents such as the Ras/MAPK inhibitors in prostate cancer, and discuss the future perspectives of their therapeutic efficacy. [Mol Cancer Ther 2007;6(3):811–9]
Targeted therapeutics for multiple myeloma: The arrival of a risk-stratified approach
Authors: Fonseca Rafael , Stewart A. Keith
Published: March 2007

Multiple myeloma (MM) remains an incurable hematologic malignancy characterized by frequent early responses, inevitably followed by treatment relapse. Until recently, few effective therapies existed. Indeed, the use of alkylating agents and corticosteroids had remained the treatment of choice for almost four decades. Several novel agents for MM have now become available, including the immunomodulatory drugs thalidomide and lenalidomide, as well as the proteasome inhibitor bortezomib. Each of these agents is undergoing extensive clinical evaluation in combination with other therapies to produce unprecedented response rates in newly diagnosed and relapsed MM. Nevertheless, relapse remains universal and further therapeutics with broad activity are required. Importantly, it has become clear that pivotal genetic events are the primary harbingers of clinical outcome and novel targeted therapy approaches using existing approved drugs or novel agents, which address that disrupted signaling pathways are now in various stages of clinical testing. It seems increasingly likely that novel drug combinations, which together turn off these critical Achilles heels, will become the standard of care and that treatment will become increasingly personalized and guided by genetic testing and prognostic factors. [Mol Cancer Ther 2007;6(3):802–10]
Inhibition of heat shock protein 90 impairs epidermal growth factor–mediated signaling in gastric cancer cells and reduces tumor growth and vascularization in vivo
Authors: Lang Sven A. , Klein Dagmar , Moser Christian , Gaumann Andreas , Glockzin Gabriel , Dahlke Marc H. , Dietmaier Wolfgang , Bolder Ulrich , Schlitt Hans J. , Geissler Edward K. , Stoeltzing Oliver
Published: March 2007

Oncogenic signaling through activation of epidermal growth factor receptor (EGFR), HER-2, and hypoxia inducible-factor-1α (HIF-1α) has been implicated in gastric cancer growth and angiogenesis through up-regulation of vascular endothelial growth factor (VEGF). Recently, heat shock protein 90 (Hsp90) has been identified as a critical regulator of oncogenic protein stability, including EGFR, HER-2, and HIF-1α. We hypothesized that inhibition of Hsp90 impairs EGF- and hypoxia-mediated angiogenic signaling in gastric cancer cells and consequently inhibits angiogenesis and tumor growth. In vitro, the geldanamycin derivate 17-allylamino-17-demethoxygeldanamycin (17-AAG) led to marked reduction in constitutive and inducible activation of extracellular signal-regulated kinase 1/2, Akt, and signal transducer and activator of transcription 3 and decreased nuclear HIF-1α protein. In addition, EGFR and HER-2 were down-regulated after Hsp90 inhibition. With respect to regulation of angiogenic molecules, 17-AAG significantly reduced EGF-mediated VEGF secretion. Phosphorylation of focal adhesion kinase and paxillin were both abrogated by 17-AAG, which resulted in significant impairment of cancer cell motility. Interestingly, cytotoxic effects of 17-AAG in vitro were higher on cancer cells and gastric fibroblasts than on pericytes. In vivo, the water-soluble compound 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG; 25 mg/kg, thrice per week) significantly reduced s.c. xenografted tumor growth. By immunohistochemistry, 17-DMAG significantly reduced vessel area and numbers of proliferating tumor cells in sections. Furthermore, similar significant growth-inhibitory effects of 17-DMAG were achieved when administered as low-dose therapy (5 mg/kg, thrice per week). In conclusion, blocking Hsp90 disrupts multiple proangiogenic signaling pathways in gastric cancer cells and inhibits xenografted tumor growth in vivo. Hence, gastric cancer harbors attractive molecular targets for therapy with Hsp90 inhibitors, which could lead to improved efficacy of antineoplastic therapy regimens. [Mol Cancer Ther 2007;6(3):1123–32]
Combined targeting of epidermal growth factor receptor and hedgehog signaling by gefitinib and cyclopamine cooperatively improves the cytotoxic effects of docetaxel on metastatic prostate cancer cells
Authors: Mimeault Murielle , Johansson Sonny L. , Vankatraman Ganesh , Moore Eric , Henichart Jean-Pierre , Depreux Patrick , Lin Ming-Fong , Batra Surinder K.
Published: March 2007

The epidermal growth factor receptor (EGFR) and hedgehog cascades provide a critical role in prostate cancer progression and contribute to the resistance to clinical therapies and disease relapse. Therefore, we evaluated, for the first time, the antiproliferative and cytotoxic effects induced by a combination of selective inhibitors of EGFR tyrosine kinase and smoothened hedgehog signaling element, gefitinib and cyclopamine, with a current chemotherapeutic drug used in the clinics, docetaxel, on some metastatic prostate cancer cell lines. Immunohistochemical analyses revealed that sonic hedgehog (SHH) expression was enhanced in 39% of primary prostatic adenocarcinomas (Gleason scores 4–10) compared with the corresponding normal tissues of the same prostate gland from 32 prostate cancer patients. The confocal microscopy and Western blot analyses have also indicated the high expression levels of SHH and EGFR in metastatic LNCaP, DU145, and PC3 cells. Moreover, the results revealed that the drugs, alone or in combination, at lower concentrations inhibited the growth of EGF plus SHH–stimulated and serum-stimulated androgen-responsive LNCaP-C33 and androgen-independent LNCaP-C81, DU145, and PC3 cells. Importantly, the combined docetaxel, gefitinib, and cyclopamine also caused a higher rate of apoptotic death of prostate cancer cells compared with individual agents. The cytotoxic effects induced by these drugs in PC3 cells seem to be mediated in part through the cellular ceramide production and activation of caspase cascades via a mitochondrial pathway and the release of cytochrome c into the cytosol. Additionally, the combined agents were more effective at suppressing the invasiveness of PC3 cells through Matrigel in vitro than the single drugs. These findings indicate that the combined use of inhibitors of EGF-EGFR and hedgehog signaling with docetaxel could represent a more promising strategy for treatment in patients with metastatic and androgen-independent prostate cancer. [Mol Cancer Ther 2007;6(3):967–78]
Epigenetic profiling of multidrug-resistant human MCF-7 breast adenocarcinoma cells reveals novel hyper- and hypomethylated targets
Authors: Chekhun Vasyl' F. , Lukyanova Nataliya Yu , Kovalchuk Olga , Tryndyak Volodymyr P. , Pogribny Igor P.
Published: March 2007

The successful treatment of cancer requires a clear understanding of multiple interacting factors involved in the development of drug resistance. Presently, two hypotheses, genetic and epigenetic, have been proposed to explain mechanisms of acquired cancer drug resistance. In the present study, we examined the alterations in epigenetic mechanisms in the drug-resistant MCF-7 human breast cancer cells induced by doxorubicin (DOX) and cisplatin (cisDDP), two chemotherapeutic drugs with different modes of action. Despite this difference, both of the drug-resistant cell lines displayed similar pronounced changes in the global epigenetic landscape showing loss of global DNA methylation, loss of histone H4 lysine 20 trimethylation, increased phosporylation of histone H3 serine 10, and diminished expression of Suv4-20h2 histone methyltransferase compared with parental MCF-7 cells. In addition to global epigenetic changes, the MCF-7/DOX and MCF-7/cisDDP drug-resistant cells are characterized by extensive alterations in region-specific DNA methylation, as indicated by the appearance of the number of differentially methylated DNA genes. A detailed analysis of hypo- and hypermethylated DNA sequences revealed that the acquisition of drug-resistant phenotype of MCF-7 cells to DOX and cisDDP, in addition to specific alterations induced by a particular drug only, was characterized by three major common mechanisms: dysfunction of genes involved in estrogen metabolism (sulfatase 2 and estrogen receptor α), apoptosis (p73, α-tubulin, BCL2-antagonist of cell death, tissue transglutaminase 2 and forkhead box protein K1), and cell-cell contact (leptin, stromal cell–derived factor receptor 1, activin A receptor E-cadherin) and showed that two opposing hypo- and hypermethylation processes may enhance and complement each other in the disruption of these pathways. These results provided evidence that epigenetic changes are an important feature of cancer cells with acquired drug-resistant phenotype and may be a crucial contributing factor to its development. Finally, deregulation of similar pathways may explain the existence and provide mechanism of cross-resistance of cancer cells to different types of chemotherapeutic agents. [Mol Cancer Ther 2007;6(3):1089–98]
Food versus risk: foraging decision in young Tiger snakes, Notechis scutatus
Authors: Bradshaw Don , Bonnet Xavier , Aubret Fabien
Published: March 2007

Foraging behaviour is influenced by an animal's level of hunger, and may reflect a trade-off between optimizing food acquisition and avoiding predation. Young tiger snakes were raised either on a high or low food diet and exposed to a predation threat while foraging. Under these circumstances, lower condition snakes (low food diet) were prone to take additional feeding/foraging risks: food was accepted at a much higher rate compared with the higher condition animals (high food diet) that were less inclined to risk feeding under a predation threat. This study provides the first direct example of predation risk-associated foraging decisions in snakes.
Temporal niche of acoustic activity in anurans: interspecific and seasonal variation in a neotropical assemblage from south-eastern Brazil
Authors: Rocha Carlos Frederico Duarte , Marra Rodrigo Ventura , Van Sluys Monique , Boquimpani-Freitas Leonardo
Published: March 2007

Sympatric anuran species tend to differ in their temporal niche breadth and may also have considerable seasonal variation in diel activity patterns. We studied the temporal niche breadths of six anuran species during 24 consecutive months in an area of secondary forest at the Brazilian Atlantic Rainforest. Along hourly intervals, at each of three observation points along a stream, the number of calling males of Adenomera marmorata, Eleutherodactylus parvus, Physalaemus signifer, Aplastodiscus eugenioi, Scinax hayii and S. trapicheiroi was recorded. The influence of rainfall, air humidity and temperature on the variation in the niche breadth of each species was analysed. Mean niche breadth differed for all species. Scinax trapicheiroi had the broadest niche and S. hayii had the smallest. Temporal niche breadth varied seasonally for all species. Two species (E. parvus and S. hayii) showed strong variation in the temporal niche when compared to the other species. Eleutherodactylus parvus, A. eugenioi and S. hayii were significantly affected by rainfall, air humidity and temperature. Niche overlap among species pairs also varied annually with mean temporal niche overlap being greater during the rainy season than during the dry season.
Thermal effects on locomotion in the nocturnal gecko Homonota darwini (Gekkonidae)
Authors: Renner Marianne , Cussac Víctor , Ibargüengoytía Nora , Piantoni Carla , Boretto Jorgelina
Published: March 2007

Nocturnal lizards show a complex adaptation to environmental temperature. They obtain heat from the substratum, using daytime for performing physiological functions inside thermally suitable shelters, and night-time which involves locomotion and loss of heat for capturing prey. Homonota darwini, the southernmost geckonid in the world, is a small nocturnal insectivorous gecko that occurs in saxicolous habitats of Patagonia, Argentina. Geckos were captured by hand during the day on a rocky hill near Bariloche (Río Negro, Argentina) in spring and summer. All the geckos were active during daytime and had good limb mobility with a median body temperature of 23°C. Body temperatures showed a direct dependence on the temperature of the roof of the shelter and on the air temperature. Geckos were made to run on a horizontal track and running speed was measured in two experiments: long runs (1 m) and sprint runs (0.20 m) during the day (diurnal) and at night (nocturnal). Speed was significantly greater in sprints than in long runs and speed increased with body temperature, reaching a maximum at a body temperature of 22°C. Thus, we conclude that, although the low temperatures of Patagonia impose heavy constraints on the physiological performance of Homonota darwini, they have a peculiar arrangement of mechanical and biochemical abilities which allows for resource acquisition at night, using cryptic habits and short sprint runs.
Population size, habitat choice and sexual dimorphism of the Amazonian tortoise (Geochelone denticulata) in Tinigua National Park, Colombia
Authors: Álvarez  , Rojas Ana , Borda Carlos , Stevenson Pablo
Published: March 2007

The Amazonian tortoise, Geochelone denticulata, has been classified as vulnerable; nevertheless, necessary ecological and demographic information to formulate conservation plans is limited. In this study we present data on population density, habitat preference, diet and morphological measurements of a population inhabiting a lowland rainforest in Colombia. We used line transect methods to estimate population density over three different years, and we measured and marked 73 individuals in two additional years. The estimated population density based on 158 encounters was similar over the three years (41 ± 20, 38 ± 6, 34 ± 8 ind/km2 ±SE, respectively). However, we found marked differences between seasons within years, because it was easy to detect individuals (particularly males) during mating periods. There was no evidence of large scale seasonal migrations; thus, it is possible that individuals were missed in the non-reproductive season and therefore our figures may underestimate population size. For the same reason, sex ratios during the mating season may be more biased towards males than for whole year estimates (1.7:1 vs. 1.2:1). Monthly density estimates were significantly correlated with mating frequency and with estimates of fruit abundance, but were not associated with rainfall, temperature or sun radiance. These results suggest that males might use available energy from fruit to travel extensively during the mating season in search of females. However, the most productive forest type in terms of fruit was not preferred by tortoises, to the contrary, they were more commonly encountered in forests with a high proportion of gaps. Males tended to have larger and more elongated bodies than females. This result supports the hypothesis that since males must travel more in search of mates, it is an advantage for them to have an elongated carapace in order to move through dense understory. More ecological information is required from other geographical locations to establish which ecological variables are most important in determining the carrying capacity for terrestrial tortoises. So far the demographic structure of the populations suggest that predation of young individuals plays a major role.
Do crocodiles co-opt their sense of "touch" to "taste"? A possible new type of vertebrate sensory organ
Authors: Jackson Kate , Brooks Daniel
Published: March 2007

We recount here two experiments carried out which suggest the existence of the first described integumentary osmoreceptor of its kind in a vertebrate. Domed pressure receptors, present on the cranial scales of alligators have previously been demonstrated to convey the sensation of "touch" when flattened by pressure. Here we find that morphologically similar domed sensory organs present on the post-cranial scales of crocodylid but not alligatorid crocodilians flatten when exposed to increased osmotic pressure, such as that experienced when swimming in sea water hyper-osmotic to the body fluids. When contact between the integument and the surrounding sea water solution is blocked, crocodiles are found to lose their ability to discriminate salinities. We propose that the flattening of the sensory organ in hyper-osmotic sea water is sensed by the animal as "touch", but interpreted as chemical information about its surroundings.
Growth layers in bones and acrodont teeth of the agamid lizard Laudakia stoliczkana (Blanford, 1875) (Agamidae, Sauria)
Authors: Smirina Ella , Ananjeva Natalia
Published: March 2007

Growth layers in different tubular bones, in dental bone and in tooth dentine of L. stoliczkana were examined to estimate their suitability for the study of its age and growth. All bones studied have growth layers recording annual seasonal patterns of growth. Their pattern is identical in all bones studied. Resting lines, or Lines of Arrested Growth (LAGs) corresponding to the two first hibernations are subjected to resorption in the massive elongate tubular bones (femur and tibia) whereas in the more slender fibula the rate of resorption is lower. In the phalanx even the first formed layers are not subjected to resorption, but its growth in width is most likely limited. Growth layers are formed in acrodont tooth dentine, but these layers are indistinct and cannot be used for age determination. There are growth layers in the bone of attachment, but due to their multidirectional deposition it is difficult, if not impossible, to count them.
A multi-layer metadata schema for digital folklore collections
Authors: Lourdi Irene , Papatheodorou Christos , Nikolaidou Mara
Published: March 2007

Digital folklore collections are valuable sources for studying the cultural and oral tradition of a country. The main difficulty in managing such collections is material heterogeneity (handwritten texts, photographs, 3D objects, sound recordings etc.) that imposes different digitization, description and maintenance practices. A multi-layer metadata model for the description of a digital folklore collection is presented. The proposed meta-data policy considers a collection as a hierarchy of entities and combines different metadata schemas for the management of each entity. The metadata model integrates elements from different metadata schemas ensuring efficient information recovery from all structural levels. Furthermore, interoperability between the used metadata schemas is discussed and a Topic Maps model is presented as an approach for developing mappings.
An evolutionary stage model of cyberspace: a case study of Samsung Economic Research Institute
Authors: Yoon Soon-Bong , Bock Gee-Woo , Jang Seungkwon
Published: March 2007

An evolutionary stage model of cyberspace is proposed based on the four key fundamental driving forces: Moore’s Law, Gilder’s Law, Metcalfe’s Law, and the Law of Disruption. It is suggested that the managerial tasks and information and communication technologies associated with the utilization of cyberspace will change in character over a period of time, and will evolve in patterns roughly related to the proposed four stages, namely, the node stage, the link stage, the network stage, and the space stage. Each stage is described and validated through a longitudinal single-case study of Samsung Economic Research Institute (SERI) from 1996 to 2001.
A note on measuring overlap
Authors: Egghe L. , Goovaerts M.
Published: March 2007

In measuring the overlap between two sets A and B (e.g. libraries, databases) one is obliged to calculate the overlap O(A|B) of A with respect to B (i.e. the fraction of elements of B that are also in A) and of O(B|A) of B with respect to A (i.e. the fraction of elements in A that are also in B). Theoretically this requires two samples. In this paper we explain that one sample can suffice to determine confidence intervals for both O(A|B) and O(B|A). The paper closes with the example of measuring the overlap between the secondary sources in mathematics MathSciNet and Zentralblatt MATH and with a remark on the estimation of the Jaccard index.
UK academic web links and collaboration - an exploratory study
Authors: Stuart David , Thelwall Mike , Harries Gareth
Published: March 2007

Universities work in collaboration with many other organizations, and these collaborations have important consequences for the national economy. The ability to measure these collaborations in a quick, timely fashion in comparison with similar organizations would enable institutions to improve collaborative efforts. This article investigates the potential of web links to act as an indicator of collaboration through a detailed classification of 2600 links from universities to government, commercial and other domains. Whilst there are significant differences in the proportion of web links that reflect collaboration, depending on the source page owner and the target page top-level domain, the majority of web links on a university web page do not reflect a collaboration between the web page owner and the target web page owner. However, there are still a significant number of links reflecting collaborative relationships which can provide a rich source of information. A potential future area of investigation is into the number of links between web sites.
Bronchoscopy-guided radiofrequency ablation as a potential novel therapeutic tool
Authors: Tsushima K. , Koizumi T. , Tanabe T. , Nakagawa R. , Yoshikawa S. , Yasuo M. , Kubo K.
Published: March 2007

The aim of the current study was to assess the safety of bronchoscopy-guided radiofrequency ablation (RFA) and compare the effectiveness between new internal cooled-RFA and standard noncooled-RFA.

Normal lungs from sheep were used (n = 6). Internal cooled-RFA and standard noncooled-RFA were set to assess the most suitable RFA conditions, such as power output, flow rate and ablation time. Internal cooled-RFA was then applied under the most optimal conditions of power output and flow rate for 15, 30, 60 and 120 s, and two water temperatures either room temperature (RT) water or cold water. Criteria for the most appropriate conditions were set over 15 s of ablation time and 50°C of the tip's temperature.

Internal cooled-RFA had no complications. Standard noncooled-RFA was complicated with bronchial bleeding after RFA. On the basis of the histological findings, average temperature and average output, the most appropriate conditions of the cooled-RFA were a power output of 30 W and flow rate of 30 or 40 mL·min−1. The cooled-RFA using cold water caused a smaller, more discrete, lesion compared with that using RT water.

Bronchoscopy-guided internal cooled-radiofrequency ablation was an effective, safe and feasible procedure that could become a potential therapeutic tool in managing lung pathology.
PU.1 and ICSBP control constitutive and IFN-γ-regulatedTlr9gene expression in mouse macrophages
Authors: Schroder Kate , Lichtinger Monika , Irvine Katharine M , Brion Kristian , Trieu Angela , Ross Ian L , Ravasi Timothy , Stacey Katryn J , Rehli Michael , Hume David A , Sweet Matthew J
Published: March 2007

Macrophages are activated by unmethylated CpG-containing DNA (CpG DNA) via TLR9. IFN-γ and LPS can synergize with CpG DNA to enhance proinflammatory responses in murine macrophages. Here, we show that LPS and IFN-γ up-regulated Tlr9 mRNA in murine bone marrow-derived macrophages (BMM). The ability of LPS and IFN-γ to induce Tlr9 mRNA expression in BMM was dependent on the presence of the growth factor, CSF-1, which is constitutively present in vivo. However, there were clear differences in mechanisms of Tlr9 mRNA induction. LPS stimulation rapidly removed the CSF-1 receptor (CSF-1R) from the cell surface, thereby blocking CSF-1-mediated transcriptional repression and indirectly inducing Tlr9 mRNA expression. By contrast, IFN-γ activated the Tlr9 promoter directly and only marginally affected cell surface CSF-1R expression. An ∼100-bp proximal promoter of the murine Tlr9 gene was sufficient to confer basal and IFN-γ-inducible expression in RAW264.7 cells. A composite IFN regulatory factor (IRF)/PU.1 site upon the major transcription start site was identified. Mutation of the binding sites for PU.1 or IRF impaired basal promoter activity, but only the IRF-binding site was required for IFN-γ induction. The mRNA expression of the IRF family member IFN consensus-binding protein [(ICSBP)/IRF8] was coregulated with Tlr9 in macrophages, and constitutive and IFN-γ-inducible Tlr9 mRNA expression was reduced in ICSBP-deficient BMM. This study therefore characterizes the regulation of mouse Tlr9 expression and defines a molecular mechanism by which IFN-γ amplifies mouse macrophage responses to CpG DNA.
Transcript overexpression of theMBD2andMBD4genes in CD4+ T cells from systemic lupus erythematosus patients
Authors: Balada Eva , Ordi-Ros Josep , Serrano-Acedo Silvia , Martinez-Lostao Luis , Vilardell-Tarrés Miquel
Published: March 2007

Global DNA hypomethylation in CD4+ T cells has been detected in systemic lupus erythematosus (SLE), and it seems to be linked to its pathogenesis. We investigated the relationship between overall DNA methylation and the expression of two methyl CpG-binding domain (MBD) proteins. DNA deoxymethylcytosine (dmC) content of purified CD4+ T cells from 29 SLE patients and 30 healthy controls was measured by means of an ELISA. Transcript levels of two methyl CpG-binding proteins (MBD2 and MBD4) were quantified by real-time RT-PCR. Association studies were also carried out with several laboratory parameters, as well as with the patients’ clinical manifestations. SLE patients had significantly less CD4+ T cell DNA dmC content than controls (0.802±0.134 vs. 0.901±0.133; P=0.007). MBD2 and MBD4 mRNA levels were considerably higher in the patients’ group: 0.975 ± 0683 versus 0.604 ± 0.614 (P=0.004) and 0.359 ± 0.330 versus 0.092 ± 0.169, respectively (P<0.0005). It is interesting that SLE patients showed a negative correlation between methylation indices and MBD2 (r=–0.609, P<0.0005) and MBD4 (r=–0.395, P=0.034) transcript levels. MBD2 and MBD4 transcript overexpression and inverse correlations with DNA methylation indices indicate that both enzymes may really have a direct and active role on the genome-wide DNA hypomethylation observed in CD4+ T cells from SLE patients.
Leukocyte membrane “expansion”: a central mechanism for leukocyte extravasation
Authors: Dewitt Sharon , Hallett Maurice
Published: March 2007

The infiltration of inflamed tissues by leukocytes is a key event in the development and progression of inflammation. Although individual cytokines, which coordinate extravasation, have become the targets for therapy, a mechanism that is common to white cell extravasation, regardless of the specific molecular mechanism involved, would represent a more attractive therapeutic target. Such a target may be represented by the events underlying the spreading of leukocytes on the endothelium, which is a necessary prelude to extravasation. This leukocyte “spreading” involves an apparent increase in the cell surface area. The aim of this review is to examine whether the mechanism underlying the apparent expansion of plasma membrane surface area during leukocyte extravasation could be an “Achilles’ heel,” which is amenable to therapeutic intervention. In this short review, we evaluate the models proposed for the mechanism of membrane “expansion” and discuss recent data, which point to a mechanism of membrane “unwrinkling.” The molecular pathway for the unwrinkling of the leukocyte plasma membrane may involve Ca2+ activatio of μ-calpain and cleavage of cytoskeletal linkage molecules such as talin and ezrin. This route could be common to all extravasation signals and thus, represents a potential target for anti-inflammatory therapy.
Focal adhesion kinase controls morphogenesis of theDrosophilaoptic stalk
Authors: Murakami Satoshi , Umetsu Daiki , Maeyama Yuko , Sato Makoto , Yoshida Shoko , Tabata Tetsuya
Published: March 2007

Photoreceptor cell axons (R axons) innervate optic ganglia in the Drosophila brain through the tubular optic stalk. This structure consists of surface glia (SG) and forms independently of R axon projection. In a screen for genes involved in optic stalk formation, we identified Fak56D encoding a Drosophila homolog of mammalian focal adhesion kinase (FAK). FAK is a main component of the focal adhesion signaling that regulates various cellular events, including cell migration and morphology. We show that Fak56D mutation causes severe disruption of the optic stalk structure. These phenotypes were completely rescued by Fak56D transgene expression in the SG cells but not in photoreceptor cells. Moreover, Fak56D genetically interacts with myospheroid, which encodes an integrin β subunit. In addition,we found that CdGAPr is also required for optic stalk formation and genetically interacts with Fak56D. CdGAPr encodes a GTPase-activating domain that is homologous to that of mammalian CdGAP, which functions in focal adhesion signaling. Hence the optic stalk is a simple monolayered structure that can serve as an ideal system for studying glial cell morphogenesis and the developmental role(s) of focal adhesion signaling.