bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epigenetic modifications in osteogenic differentiation and transformation
Authors: Thomas David , Kansara Maya 
Published: April 2006

AbstractAlmost all tumors are characterized by both architectural and cellular abnormalities in differentiation. Osteoblast development is relatively well understood, making osteosarcoma a good model for understanding how tumorigenesis perturbs normal differentiation. We argue that there are two key transition points in normal cellular differentiation that are the focus of oncogenic events, in both of which epigenetic processes are critical. The first is the transition from an uncommitted pluripotent precursor (mesenchymal stem cell) to the ‘transit‐amplifying compartment’ of the osteoblast lineage. This transition, normally exquisitely regulated in space and time, is abnormal in cancer. The second involves termination of lineage expansion, equally tightly regulated under normal circumstances. In cancer, the mechanisms that mandate eventual cessation of cell division are almost universally disrupted. This model predicts that key differentiation genes in bone, such as RUNX2, act in an oncogenic fashion to initiate entry into a proliferative phase of cell differentiation, and anti‐oncogenically into the post‐mitotic state, resulting in ambivalent roles in tumorigenesis. Polycomb genes exemplify epigenetic processes in the stem cell compartment and tumorigenesis, and are implicated in skeletal development in vivo. The epigenetic functions of the retinoblastoma protein, which plays a key role in tumorigenesis in bone, is discussed in the context of terminal cell cycle exit. J. Cell. Biochem. 98: 757–769, 2006. © 2006 Wiley‐Liss, Inc.
Chaperone‐like activity revealed in the matricellular protein SPARC
Authors: Emerson Ryan O. , Sage E. Helene , Ghosh Joy G. , Clark John I. 
Published: April 2006

AbstractSPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular glycoprotein that modulates cell proliferation, adhesion, migration, and extracellular matrix (ECM) production. In this report chaperone‐like activity of SPARC was identified in a thermal aggregation assay in vitro. Ultraviolet circular dichroism (UVCD) spectroscopy determined that SPARC was stable at temperatures up to 50°C. Unfolding and aggregation of the chaperone target protein, alcohol dehydrogenase (ADH), were initiated at 50°C. SPARC inhibited the thermal aggregation of ADH in a concentration‐dependent manner, with maximal inhibition at a 1:4 molar ratio of SPARC:ADH. Synergy between the chaperone‐like activities of SPARC and αB‐crystallin, a small heat shock protein and molecular chaperone in the lens, was observed in SPARC‐αB‐crystallin double −/− mice. J. Cell. Biochem. 98: 701–705, 2006. © 2006 Wiley‐Liss, Inc.
Modulation of mouse RANKL gene expression by Runx2 and PKA pathway
Authors: Mori Kiyoshi , Kitazawa Riko , Kondo Takeshi , Maeda Sakan , Yamaguchi Akira , Kitazawa Sohei 
Published: April 2006

AbstractRunx2 regulates the target genes characteristic of osteoblastic phenotypes, while exerting diverse and sometimes controversial effects on osteoblastic cells depending on their differentiation stage. Receptor activator of nuclear factor‐κB (RANK) ligand (RANKL) is a membrane bound cytokine essential for osteo(chondro)clastogenesis. During endochondral ossification, while Runx2‐positive hypertrophic chondrocytes express RANKL, the steady‐state expression of the RANKL gene in osteoblastic cells is, at later stages, kept at a relatively low level to sustain the established bone. The aim of this study was to elucidate the mechanism whereby Runx2 and the protein kinase A (PKA) pathway modulate RANKL expression, especially from the viewpoint of their functions in RANKL basic promoter activity and in chromatin structural changes in osteoblastic/stromal cells. Osteoblastic/stromal cell lines derived from normal and Runx2‐deficient mice were used to analyze endogenous RANKL gene expression by real‐time reverse transcription (RT)‐PCR, the acetylation status of the H3 and H4 histone proteins associated with the 5′‐flanking region of the RANKL gene by chromatin immunoprecipitation, and the exogenously transfected RANKL gene promoter activity both in the steady‐state and under PKA‐activated conditions. Here, we demonstrate that Runx2 suppresses steady‐state RANKL gene expression by condensing chromatin, while showing a slightly positive effect on RANKL basic promoter activity. Besides acting through the CRE‐like region (−0.96 kb) of the RANKL gene promoter, forskolin (FK) treatment transactivates the RANKL gene by antagonizing the function of Runx2, by reducing Runx2 mRNA expression and by opening the chromatin conformation far upstream (more than 40 kb) of the RANKL gene. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Androgen axis in prostate cancer
Authors: Culig Zoran , Bartsch Georg 
Published: April 2006

AbstractEndocrine therapy for advanced prostate cancer is based on androgen ablation or blockade of the androgen receptor (AR). AR action in prostate cancer has been investigated in a number of cell lines, their derivatives, and transgenic animals. AR expression is heterogenous in prostate cancer in vivo; it could be detected in most primary tumors and their metastases. However, some cells lack the AR because of epigenetic changes in the gene promoter. AR expression increases after chronic androgen ablation in vitro. In several xenografts, AR upregulation is the most consistent change identified during progression towards therapy resistance. In contrast, the AR pathway may be by‐passed during chronic treatment with a nonsteroidal anti‐androgen. AR sensitivity in prostate cancer increases as a result of activation of the Ras/mitogen‐activated protein kinase pathway. One of the major difficulties in endocrine therapy for prostate cancer is acquisition of agonistic properties of AR antagonists observed in the presence of mutated AR. Enhancement of AR function by associated coactivator proteins has been extensively investigated. Cofactors SRC‐1, RAC3, p300/CBP, TIF‐2, and Tip60 are upregulated in advanced prostate cancer. Most studies on ligand‐independent activation of the AR are focused on Her‐2/neu and interleukin‐6 (IL‐6). On the basis of studies that showed overexpression and activation of the AR in advanced prostate cancer, it was suggested that novel therapies that reduce AR expression will provide a benefit to patients. There is experimental evidence showing that prostate tumor growth in vitro and in vivo is inhibited following administration of chemopreventive drugs or antisense oligonucleotides that downregulate AR mRNA and protein expression. J. Cell. Biochem. 99: 373–381, 2006. © 2006 Wiley‐Liss, Inc.
p27kip1 overexpression promotes paclitaxel‐induced apoptosis in pRb‐defective SaOs‐2 cells
Authors: Gabellini Chiara , Pucci Bruna , Valdivieso Paola , D'Andrilli Giuseppina , Tafani Marco , De Luca Antonio , Masciullo Valeria 
Published: April 2006

Abstractp27kip1 is a cyclin‐dependent kinase (CDK) inhibitor, which controls several cellular processes in strict collaboration with pRb. We evaluated the role of p27kip1 in paclitaxel‐induced apoptosis in the pRb‐defective SaOs‐2 cells. Following 48 h of exposure of SaOs‐2 cells to 100 nM paclitaxel, we observed an increase in p27kip1 expression caused by the decrease of the ubiquitin‐proteasome activity. Such increase was not observed in SaOs‐2 cells treated with the caspase inhibitors Z‐VAD‐FMK, suggesting that p27kip1 enhancement at 48 h is strictly related to apoptosis. Finally, we demonstrated that SaOs‐2 cells transiently overexpressing the p27kip1 protein are more susceptible to paclitaxel‐induced apoptosis than SaOs‐2 cells transiently transfected with the empty vector. Indeed, after 48 h of paclitaxel treatment, 41.8% of SaOs‐2 cells transiently transfected with a pcDNA3‐p27kip1 construct were Annexin V‐positive compared to 30.6% of SaOs‐2 cells transfected with the empty vector (P < 0.05). In conclusion, we demonstrated that transfection of the pRb‐defective SaOs‐2 cells with the p27kip1 gene via plasmid increases their susceptibility to paclitaxel‐induced apoptosis. The promoting effect of p27kip1 overexpression on apoptosis makes p27kip1 and proteasomal inhibitors interesting tools for therapy in patients with pRb‐defective cancers. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Existence of autocrine loop between interleukin‐6 and tranforming growth factor‐β1 in activated rat pancreatic stellate cells
Authors: Aoki Hiroyoshi , Ohnishi Hirohide , Hama Kouji , Shinozaki Satoshi , Kita Hiroto , Yamamoto Hironori , Osawa Hiroyuki , Sato Kiichi , Tamada Kiichi , Sugano Kentaro 
Published: April 2006

AbstractInterleukin (IL)‐6 is a proinflammatory cytokine assumed to participate in pancreatic fibrosis by activating pancreatic stellate cells (PSCs). Autocrine TGF‐β1 is to central in PSC functional regulation. In this study, we examined IL‐6 secretion from culture‐activated rat PSCs and its regulatory mechanism. Activated PSCs express and secrete IL‐6. When anti‐TGF‐β1 neutralizing antibody was added in the culture medium, IL‐6 secretion from activated PSCs was inhibited, whereas exogenous TGF‐β1 added in the culture medium enhanced IL‐6 expression and secretion by PSCs in a dose dependent manner. Infection of PSCs with an adenovirus expressing dominant‐negative Smad2/3 attenuated basal and TGF‐β1‐stimulated IL‐6 expression and secretion of PSCs. We also demonstrated the reciprocal effect of PSCs‐secreted IL‐6 on autocrine TGF‐β1. Anti‐IL‐6 neutralizing antibody inhibited TGF‐β1 secretion from PSCs. Preincubation of cells with 10 nM PD98059, an extracellular signal‐regulated kinase (ERK)‐dependent pathway inhibitor, attenuated IL‐6‐enhanced TGF‐β1 expression and secretion of PSCs. In addition, IL‐6 activated ERK in PSCs. These data indicate the existence of autocrine loop between IL‐6 and TGF‐β1 through ERK‐ and Smad2/3‐dependent pathways in activated PSCs. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Methotrexate induced differentiation in colon cancer cells is primarily due to purine deprivation
Authors: Singh R. , Fouladi‐Nashta A.A. , Li D. , Halliday N. , Barrett D.A. , Sinclair K.D. 
Published: April 2006

AbstractThe folate antagonist methotrexate (MTX) inhibits synthesis of tetrahydrofolate (THF), pyrimidines and purines, and induces differentiation in several cell types. At 1 µM, MTX reduced proliferation and induced differentiation in HT29 colon cancer cells; the latter effect was augmented (P < 0.001) by thymidine (100 µM) but was reversed (P < 0.001) by the purines, hypoxanthine (Hx; 100 µM) and adenosine (100 µM). In contrast 5‐fluoro‐uracil (5‐FU), a specific thymidylate synthase (TS) inhibitor, had no effect on differentiation, suggesting that MTX‐induced differentiation is not due to a reduction in thymidine but to the inhibition of purine biosynthesis. Inhibition of cyclic AMP (cAMP) by RpcAMP (25 µM) further enhanced (P < 0.001) MTX induced differentiation, whereas the cAMP activator forskolin (10 µM) reversed (P < 0.001) MTX induced differentiation. These observations implicate a central role of adenosine and cAMP in MTX induced differentiation. By combining Western blot analysis with liquid chromatography‐mass spectrometry (LC‐MS)and HPLC analyses we also reveal both the expression and activity of key enzymes (i.e. methionine synthase (MS), s‐adenosylhomocysteinase, cystathionine β‐synthase and ornithine decarboxylase) regulating methyl cycle, transsulfuration and polyamine pathways in HT29 colon cancer cells. At 1 µM, MTX induced differentiation was associated with a marked reduction in the intracellular concentrations of adenosine and, consequently, S‐adenosylmethionine (SAM), S‐adenosylhomocysteine, polyamines and glutathione (GSH). Importantly, the marked reduction in methionine that accompanied MS inhibition following MTX treatment was non‐limiting with respect to SAM synthesis. Collectively, these findings indicate that the effects of MTX on cellular differentiation and single carbon metabolism are primarily due to the intracellular depletion of purines. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
UVB‐induced 1,25(OH)2D3 production and vitamin D activity in intestinal CaCo‐2 cells and in THP‐1 macrophages pretreated with a sterol Δ7‐reductase inhibitor
Authors: Vantieghem Katleen , Overbergh Lut , Carmeliet Geert , De Haes Petra , Bouillon Roger , Segaert Siegfried 
Published: April 2006

AbstractEpidermal keratinocytes are able to produce 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] and induce vitamin D activity upon UVB irradiation. To find out whether this property is keratinocyte specific, we investigated this characteristic in two other cell types, namely intestinal CaCo‐2 cells and the macrophage‐like differentiated THP‐1 cells. THP‐1 macrophages and preconfluent CaCo‐2 cells contain the vitamin D receptor (VDR), possess 25‐hydroxylase (CYP2R1 and CYP27A1) and 1α‐hydroxylase (CYP27B1) activity, and survive the low UVB doses essential for vitamin D3 photoproduction. Upon irradiation, 24‐hydroxylase (CYP24) mRNA is induced in both cell types pretreated with the sterol Δ7‐reductase inhibitor BM15766 whereby the 7‐dehydrocholesterol (7‐DHC) content was increased. Transfection studies in CaCo‐2 cells with a vitamin D response element‐containing construct revealed the involvement of the VDR in this UVB‐dependent CYP24 induction. The CYP24 inducing activity in BM15766‐pretreated UVB‐irradiated CaCo‐2 cells and THP‐1 macrophages was identified as 1,25(OH)2D3 by combined high‐performance liquid chromatography radioimmunoassay. Addition of vitamin D binding protein to the CaCo‐2 cells attenuated UVB‐induced CYP24 induction suggesting the possibility of a paracrine or autocrine role for the photoproduced 1,25(OH)2D3. In conclusion, preconfluent CaCo‐2 cells and THP‐1 macrophages are able to induce vitamin D activity upon UVB irradiation and hence combine all parts of the vitamin D photoendocrine system, a characteristic which is therefore not keratinocyte specific. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Alteration in cellular functions in mouse macrophages after exposure to 50 Hz magnetic fields
Authors: Frahm Jana , Lantow Magaréta , Lupke Madeleine , Weiss Dieter G. , Simkó Myrtill 
Published: April 2006

AbstractThe aim of the present study is to investigate whether extremely low frequency electromagnetic fields (ELF‐EMF) affect certain cellular functions and immunologic parameters of mouse macrophages. In this study, the influence of 50 Hz magnetic fields (MF) at 1.0 mT was investigated on the phagocytic activity and on the interleukin‐1β (IL‐1β) production in differentiated macrophages. MF‐exposure led to an increased phagocytic activity after 45 min, shown as a 1.6‐fold increased uptake of latex beads in MF‐exposed cells compared to controls. We also demonstrate an increased IL‐1β release in macrophages after 24 h exposure (1.0 mT MF). Time‐dependent IL‐1β formation was significantly increased already after 4 h and reached a maximum of 12.3‐fold increase after 24 h compared to controls. Another aspect of this study was to examine the genotoxic capacity of 1.0 mT MF by analyzing the micronucleus (MN) formation in long‐term (12, 24, and 48 h) exposed macrophages. Our data show no significant differences in MN formation or irregular mitotic activities in exposed cells. Furthermore, the effects of different flux densities (ranging from 0.05 up to 1.0 mT for 45 min) of 50 Hz MF was tested on free radical formation as an endpoint of cell activation in mouse macrophage precursor cells. All tested flux densities significantly stimulated the formation of free radicals. Here, we demonstrate the capacity of ELF‐EMF to stimulate physiological cell functions in mouse macrophages shown by the significantly elevated phagocytic activity, free radical release, and IL‐1β production suggesting the cell activation capacity of ELF‐EMF in the absence of any genotoxic effects. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Stable formation of mutated p53 multimers in a Chinese hamster cell line causes defective p53 nuclear localization and abrogates its residual function
Authors: Ottaggio Laura , Campomenosi Paola , Fronza Gilberto , Menichini Paola , Miele Mariangela , Moro Francesca , Viaggi Silvia , Zunino Annalisa , Abbondandolo Angelo 
Published: April 2006

AbstractWe have previously described a methotrexate‐resistant cell line (MTX M) characterized by amplified dihydrofolate reductase (DHFR) genes, cytoplasmic p53 localization, and p53 stable tetramers. To investigate the p53 functionality in MTX M, the effect of chemical/physical agents was studied. In MTX M cells, DNA damage did not induce p53 or mdm‐2 protein, while in the parental V79 cells, a residual p53 activity was found. cDNA sequencing showed that V79 and MTX M cells share the same mutations, indicating that the complete loss of p53 function in MTX M cells was due to cytoplasmic sequestration of a mutated p53 with residual activity. In Chinese hamster, both p53 and DHFR genes map on short arm of chromosome 2 suggesting that p53 itself might be amplified. However, fluorescence in situ hybridization with a hamster p53 probe showed only a single signal. Thus, the presence of p53 stable tetramers in MTX M cells, although correlated with DNA amplification, could not be the consequence of either p53 or DHFR gene amplification. Expression of a C‐terminal human p53 peptide does not induce p53 nuclear accumulation, indicating that the cytoplasmic localization is due to a mechanism different from that already described in cancer cell lines. Treatments with Sodium Butyrate induced β‐tubulin polymerization, but did not apparently organize a normal microtubule network, which is shown to be important for the p53 localization. Our data indicated that in MTX M cells, p53 is sequestered in the cytoplasm by a novel mechanism that abrogates p53 residual function. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Retinoids directly activate the collagen X promoter in prehypertrophic chondrocytes through a distal retinoic acid response element
Authors: Cohen Arthur J. , Lassová Luisa , Golden Eleanor B. , Niu Zeling , Adams Sherrill L. 
Published: April 2006

AbstractRetinoids are essential for the terminal differentiation of chondrocytes during endochondral bone formation. This maturation process is characterized by increased cell size, expression of a unique extracellular matrix protein, collagen X, and eventually by mineralization of the matrix. Retinoids stimulate chondrocyte maturation in cultured cells and experimental animals, as well as in clinical studies of synthetic retinoids; furthermore, retinoid antagonists prevent chondrocyte maturation in vivo. However, the mechanisms by which retinoids regulate this process are poorly understood. We and others showed previously that retinoic acid (RA) stimulates expression of genes encoding bone morphogenetic proteins (BMPs), suggesting that retinoid effects on chondrocyte maturation may be indirect. However, we now show that RA also directly stimulates transcription of the collagen X gene promoter. We have identified three RA response element (RARE) half‐sites in the promoter, located 2,600 nucleotides upstream from the transcription start site. These three half‐sites function as two overlapping RAREs that share the middle half‐site. Ablation of the middle half‐site destroys both elements, abolishing RA receptor (RAR) binding and drastically decreasing RA stimulation of transcription. Ablation of each of the other two half‐sites destroys only one RARE, resulting in an intermediate level of RAR binding and transcriptional stimulation. These results, together with our previously published data, indicate that retinoids stimulate collagen X transcription both directly, through activation of RARs, and indirectly, through increased BMP production. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Hamiltonian graphs involving neighborhood unions
Authors: Chen Guantao , Shreve Warren E. , Wei Bing 
Published: April 2006

AbstractDirac proved that a graph G is hamiltonian if the minimum degree $\delta(G) \geq n/2$, where n is the order of G. Let G be a graph and $A \subseteq V(G)$. The neighborhood of A is $N(A)=\{ b: ab \in E(G)$ for some $a \in A\}$. For any positive integer k, we show that every (2k − 1)‐connected graph of order n ≥ 16k3 is hamiltonian if |N(A)| ≥ n/2 for every independent vertex set A of k vertices. The result contains a few known results as special cases. The case of k = 1 is the classic result of Dirac when n is large and the case of k = 2 is a result of Broersma, Van den Heuvel, and Veldman when n is large. For general k, this result improves a result of Chen and Liu. The lower bound 2k − 1 on connectivity is best possible in general while the lower bound 16k3 for n is conjectured to be unnecessary. © 2006 Wiley Periodicals, Inc. J Graph Theory 53: 83–100, 2006
Pandemic influenza and the hospitalist: Apocalypse when?
Authors: Pile James C. , Gordon Steven M. 
Published: April 2006

AbstractBeginning with a cluster of human cases in Hong Kong in 1997, avian influenza (H5N1) has spread progressively through, and beyond, Asia in poultry and other birds; and has resulted in sporadic cases of human disease associated with high mortality. The potential for H5N1 influenza to cause a pandemic of human disease continues to be the subject of intense scrutiny by both the media and the scientific community. While the likelihood of such a prospect is uncertain, the inevitability of future pandemics of influenza is clear. Planning for the eventuality of a virulent influenza pandemic at the local, national and global level is critical to limiting the mortality and morbidity of such an occurrence. Hospitalists have a key role to play in institutional efforts to prepare for a influenza pandemic, and should be aware of lessons that my be applied from both the response to Hurricane Katrina, as well as the severe acute respiratory syndrome (SARS) epidemic. Journal of Hospital Medicine 2006;1:118–123. © 2006 Society of Hospital Medicine
Characterization of metabolites of tanshinone IIA in rats by liquid chromatography/tandem mass spectrometry
Authors: Li Peng , Wang Guang‐Ji , Li Jing , Hao Hai‐Ping , Zheng Chao‐Nan 
Published: April 2006

AbstractThe metabolism of tanshinone IIA was studied in rats after a single‐dose intravenous administration. In the present study, 12 metabolites of tanshinone IIA were identified in rat bile, urine and feces with two LC gradients using LC‐MS/MS. Seven phase I metabolites and five phase II metabolites of tanshinone IIA were characterized and their molecular structures proposed on the basis of the characteristics of their precursor ions, product ions and chromatographic retention time. The seven phase I metabolites were formed, through two main metabolic routes, which were hydroxylation and dehydrogenation metabolism. M1, M4, M5 and M6 were supposedly tanshinone IIB, hydroxytanshinone IIA, przewaquinone A and dehydrotanshinone IIA, respectively, by comparing their HPLC retention times and mass spectral patterns with those of the standard compounds. The five phase II metabolites identified in this research were all glucuronide conjugates, all of which showed a neutral loss of 176 Da. M9 and M12 were more abundant than other identified metabolites in the bile, which was the main excretion path of tanshinone IIA and the metabolites. M12 was the main metabolite of tanshinone IIA. M9 and M12 were proposed to be the glucuronide conjugates of two different semiquinones and these semiquinones were the hydrogenation products of dehydrotanshinone IIA and tanshinone IIA, respectively. This hydrogenized reaction may be catalyzed by the NAD(P)H: quinone acceptor oxidoreductase (NQO). The biotransformation pathways of tanshinone IIA were proposed on the basis of this research. Copyright © 2006 John Wiley & Sons, Ltd.