bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Syk Tyrosine Kinase Localizes to the Centrosomes and Negatively Affects Mitotic Progression
Authors: Zyss Déborah , Montcourrier Philippe , Vidal Benjamin , Anguille Christelle , Mérezègue Fabrice , Sahuquet Alain , Mangeat Paul H. , Coopman Peter J. 
Published: December 2005

AbstractWe showed previously that the spleen tyrosine kinase Syk is expressed by mammary epithelial cells and that it suppresses malignant growth of breast cancer cells. The exact molecular mechanism of its tumor-suppressive activity remains, however, to be identified. Here, we show that Syk colocalizes and copurifies with the centrosomal component γ-tubulin and exhibits a catalytic activity within the centrosomes. Moreover, its centrosomal localization depends on its intact kinase activity. Centrosomal Syk expression is persistent in interphase but promptly drops during mitosis, obviously resulting from its ubiquitinylation and proteasomal degradation. Conversely, unrestrained exogenous expression of a fluorescently tagged Discosoma sp. red fluorescent protein (DsRed)-Syk chimera engenders abnormal cell division and cell death. Transient DsRed-Syk overexpression triggers an abrupt cell death lacking hallmarks of classic apoptosis but reminiscent of mitotic catastrophe. Surviving stable DsRed-Syk–transfected cells exhibit multipolar mitotic spindles and contain multiple abnormally sized nuclei and supernumerary centrosomes, revealing anomalous cell division. Taken together, these results show that Syk is a novel centrosomal kinase that negatively affects cell division. Its expression is strictly controlled in a spatiotemporal manner, and centrosomal Syk levels need to decline to allow customary progression of mitosis.
BRCA1 Promoter Methylation in Sporadic Breast Cancer Is Associated with Reduced BRCA1 Copy Number and Chromosome 17 Aneusomy
Authors: Wei Minjie , Grushko Tatyana A. , Dignam James , Hagos Fitsum , Nanda Rita , Sveen Lise , Xu Jinhua , Fackenthal James , Tretiakova Maria , Das Soma , Olopade Olufunmilayo I. 
Published: December 2005

Abstract
To explore the molecular mechanisms for the similarities between inherited and noninherited forms of breast cancer, we tested the hypothesis that inactivation of BRCA1 by promoter hypermethylation is associated with reduced gene copy number and chromosome 17 aneusomy as observed in tumors from BRCA1 mutation carriers. Using a combination of methylation-specific PCR analysis and fluorescence in situ hybridization, we observed varying degrees of promoter methylation in 39 of 131 (29.8%) primary tumors. Despite significant tumor heterogeneity, mean copy numbers of BRCA1 and CEP17 per cell were lower in methylated cases compared with unmethylated cases [1.78 versus 2.30 (P = 0.001) and 1.85 versus 2.29 (P = 0.005), respectively]. Methylation was more frequently observed in younger women (P = 0.05) with high-grade (P = 0.001), estrogen receptor–negative (P = 0.04), and progesterone receptor–negative (P = 0.01) tumors. Moreover, methylation was associated with reduced or absent BRCA1 transcripts, which was reversible in the heavily BRCA1-methylated cell line UACC3199 following treatment with 5-aza-2′-deoxycytidine and trichostatin A. We identified five CpGs at positions −533, −355, −173, −21, and +44 as critical in the reexpression of BRCA1. We conclude that BRCA1 methylation contributes to a subset of sporadic breast cancers with the resulting molecular and clinicopathologic phenotype similar to that of hereditary BRCA1-associated breast cancers. Our data support a model of carcinogenesis in which BRCA1 promoter methylation may serve as a “first hit,” much like an inherited germ line mutation, and promote tumor progression down a restricted set of molecular pathways.
ASH1 Gene Is a Specific Therapeutic Target for Lung Cancers with Neuroendocrine Features
Authors: Osada Hirotaka , Tatematsu Yoshio , Yatabe Yasushi , Horio Yoshitsugu , Takahashi Takashi 
Published: December 2005

Abstract
Lung cancers with neuroendocrine features are usually aggressive, although the underlying molecular mechanisms largely remain to be determined. The basic helix-loop-helix protein, achaete-scute complex-like 1/achaete-scute homologue 1 (ASH1), is expressed in normal fetal pulmonary neuroendocrine cells and lung cancers with neuroendocrine elements and is suggested to be involved in lung carcinogenesis. In the present study, we show inhibition of ASH1 expression by plasmid-based RNA interference (RNAi) to significantly suppress growth of lung cancer cells with ASH1 expression through G2-M cell cycle arrest and accumulation of sub-G1 populations, possibly linked to cleavage of caspase-9 and caspase-7. However, lung cancer cell lines without ASH1 expression and immortalized normal BEAS2B bronchial epithelial cells were not affected. The RNAi-resistant mutant ASH1 clearly induced rescue from G2-M arrest, suggesting a target-specific effect of RNAi. An ASH1-RNAi adenovirus was also established and significantly inhibited not only in vitro cell proliferation but also in vivo xenograft growth of ASH1-positive NCI-H460 cells. Elevated levels of apoptosis were also observed in NCI-H460 xenografts with the ASH1-RNAi adenovirus. The present study therefore suggests that ASH1 plays a crucial role in lung cancer development and may be an effective therapeutic target in lung cancers with neuroendocrine features.
RETRACTED: Physical and Functional Interaction of DNA Methyltransferase 3A with Mbd3 and Brg1 in Mouse Lymphosarcoma Cells
Authors: Datta Jhrana , Majumder Sarmila , Bai Shoumei , Ghoshal Kalpana , Kutay Huban , Smith David Spencer , Crabb John W. , Jacob Samson T. 
Published: December 2005

Abstract
Dnmt3a and Dnmt3b are de novo DNA methyltransferases that also act as transcriptional repressors independent of methyltransferase activity. To elucidate the underlying mechanism of transcriptional repression, Dnmt3a was purified from mouse lymphosarcoma cells (P1798) by extensive fractionation on five different chromatographic matrices followed by glycerol density gradient centrifugation. Liquid chromatography electrospray tandem mass spectrometry analysis of Dnmt3a-associated polypeptides identified the methyl CpG binding protein Mbd3, histone deacetylase 1(Hdac1), and components of Brg1 complex (Brg1, Baf155, and Baf57) in the purified preparation. Association of Dnmt3a with Mbd3 and Brg1 was confirmed by coimmunoprecipitation and coimmunolocalization studies. Glutathione S-transferase pulldown assay showed that the NH2-terminal ATRX homology domain of Dnmt3a interacts with the methyl CpG binding domain of Mbd3 and with both bromo and ATPase domains of Brg1. Chromatin immunoprecipitation assay revealed that all three proteins are associated with transcriptionally silent methylated metallothionein (MT-I) promoter in the mouse lymphosarcoma cells. To understand the functional significance of their association with the promoter, their role on the MT-I promoter activity was analyzed by transient transfection assay. The results showed that Mbd3 and Dnmt3a specifically inhibited the methylated promoter, and the catalytic activity of Dnmt3a was dispensable for the suppression. In contrast, the wild-type but not the ATPase-inactive mutant of Brg1 suppressed MT-I promoter irrespective of its methylation status, implicating involvement of ATP-dependent chromatin remodeling in the process. Coexpression of two of the three interacting proteins at a time augmented their repressor function. This study shows physical and functional interaction of Dnmt3a with components of nucleosome remodeling machinery.
mda-9/Syntenin: A Positive Regulator of Melanoma Metastasis
Authors: Boukerche Habib , Su Zao-zhong , Emdad Luni , Baril Patrick , Balme Brigitte , Thomas Luc , Randolph Aaron , Valerie Kristoffer , Sarkar Devanand , Fisher Paul B. 
Published: December 2005

Abstract
Metastasis is a significant event in cancer progression and continues to pose the greatest challenge for a cancer cure. Defining genes that control metastasis in vivo may provide new targets for intervening in this process with profound therapeutic implications. Melanoma differentiation associated gene-9 (mda-9) was initially identified by subtraction hybridization as a novel gene displaying biphasic expression during terminal differentiation in human melanoma cells. Mda-9, also known as syntenin, is a PDZ-domain protein overexpressed in many types of human cancers, where it is believed to function in tumor progression. However, a functional role of mda-9/syntenin in tumor growth and metastasis and the signaling pathways involved in mediating these biological activities remain to be defined. Evidence is now provided, using weakly and highly metastatic isogenic melanoma variants, that mda-9/syntenin regulates metastasis. Expression of mda-9/syntenin correlates with advanced stages of melanoma progression. Regulating mda-9/syntenin expression using a replication-incompetent adenovirus expressing either sense or antisense mda-9/syntenin modifies the transformed phenotype and alters metastatic ability in immortal human melanocytes and metastatic melanoma cells in vitro and in vivo in newborn rats. A direct relationship is observed between mda-9/syntenin expression and increased phosphorylation of focal adhesion kinase, c-Jun-NH2-kinase, and p38. This study provides the first direct link between mda-9/syntenin expression and tumor cell dissemination in vivo and indicates that mda-9/syntenin expression activates specific signal transduction pathways, which may regulate melanoma tumor progression. Based on its ability to directly alter metastasis, mda-9/syntenin provides a promising new focus for melanoma cancer research with potential therapeutic applications for metastatic diseases.
Overcoming Fas-Mediated Apoptosis Accelerates Helicobacter-Induced Gastric Cancer in Mice
Authors: Cai Xun , Stoicov Calin , Li Hanchen , Carlson Jane , Whary Mark , Fox James G. , Houghton JeanMarie 
Published: December 2005

Abstract
The initiating molecular events in Helicobacter-induced gastric carcinogenesis are not known. Early in infection, Fas antigen–mediated apoptosis depletes parietal and chief cell populations, leading to architectural distortion. As infection progresses, metaplastic and dysplastic glands appear, which are resistant to Fas-mediated apoptosis. These abnormal lineages precede, and are thought to be the precursor lesions of, gastric cancer. Acquisition of an antiapoptotic phenotype before transformation of cells suggests that loss of Fas sensitivity may be an early required trait for gastric cancer. We reasoned that forced Fas-apoptosis resistance would result in earlier and more aggressive gastric cancer in our mouse model. Fas antigen–deficient (lpr) mice or C57BL/6 wild-type mice were irradiated and reconstituted with C57BL/6 marrow forming partial lpr/wt chimera or wt/wt control mice, extending the life span of the lpr and ensuring a competent immune response to Helicobacter felis infection. Infected lpr/wt mice developed gastric cancer as early as 7 months after infection (compared with 15 months in wt/wt mice). At 10 months (90%) and 15 months (100%), mice developed aggressive invasive lesions. This earlier onset and more aggressive histology strongly argues that Fas-apoptosis resistance is an early and important feature of gastric cancer formation.
RNA Interference–Mediated Choline Kinase Suppression in Breast Cancer Cells Induces Differentiation and Reduces Proliferation
Authors: Glunde Kristine , Raman Venu , Mori Noriko , Bhujwalla Zaver M. 
Published: December 2005

Abstract
Choline kinase is overexpressed in breast cancer cells and activated by oncogenes and mitogenic signals, making it a potential target for cancer therapy. Here, we have examined, for the first time, the effects of RNA interference (RNAi)–mediated down-regulation of choline kinase in nonmalignant and malignant human breast epithelial cell lines using magnetic resonance spectroscopy (MRS) as well as molecular analyses of proliferation and differentiation markers. RNAi knockdown of choline kinase reduced proliferation, as detected by proliferating cell nuclear antigen and Ki-67 expression, and promoted differentiation, as detected by cytosolic lipid droplet formation and expression of galectin-3. The functional importance of RNAi-mediated choline kinase down-regulation on choline phospholipid metabolism was confirmed by the significant reduction of phosphocholine detected by MRS. These results strongly support the targeting of choline kinase in breast cancer cells with RNAi and show the potential ability of noninvasive MRS to detect and evaluate future treatments incorporating such strategies.
Increased Hsp27 after Androgen Ablation Facilitates Androgen-Independent Progression in Prostate Cancer via Signal Transducers and Activators of Transcription 3–Mediated Suppression of Apoptosis
Authors: Rocchi Palma , Beraldi Eliana , Ettinger Susan , Fazli Ladan , Vessella Robert L. , Nelson Colleen , Gleave Martin 
Published: December 2005

AbstractOne strategy to improve therapies in prostate cancer involves targeting cytoprotective genes activated by androgen withdrawal to delay the emergence of the androgen-independent (AI) phenotype. The objectives of this study were to define changes in Hsp27 levels after androgen ablation and to evaluate the functional relevance of these changes in AI progression. Using a tissue microarray of 232 specimens of hormone-naïve and post-hormone ablation–treated prostate cancer, we found that Hsp27 levels increase after androgen ablation to become highly expressed (&gt;4-fold, P ≤ 0.01) in AI tumors. Hsp27 overexpression rendered LNCaP cells highly resistant to androgen withdrawal both in vitro and in vivo. Tumor volume and serum prostate–specific antigen levels increased 4.3- and 10-fold faster after castration when Hsp27 was overexpressed. Treatment of LNCaP tumor cells in vitro with Hsp27 antisense oligonucleotides (ASO) or short-interfering RNA suppressed Hsp27 levels in a dose-dependent and sequence-specific manner increased the apoptotic sub–G0-G1 fraction and caspase-3 cleavage &gt;2-fold, as well as decreased signal transducers and activators of transcription 3 (Stat3) levels and its downstream genes, c-fos and sPLA-2. The cytoprotection afforded by Hsp27 overexpression was attenuated by Stat3 knockdown using specific Stat3 ASO. Coimmunoprecipitation and immunofluorescence confirmed that Hsp27 interacts with Stat3 and that Stat3 levels correlated directly with Hsp27 levels. Hsp27 ASO treatment in athymic mice bearing LNCaP tumors significantly delayed LNCaP tumor growth after castration, decreasing mean tumor volume and serum prostate–specific antigen levels by 57% and 69%, respectively. These findings identify Hsp27 as a modulator of Stat3-regulated apoptosis after androgen ablation and as a potential therapeutic target in advanced prostate cancer.
The α6β4 Integrin Maintains the Survival of Human Breast Carcinoma Cells In vivo
Authors: Lipscomb Elizabeth A. , Simpson Kaylene J. , Lyle Stephen R. , Ring Jennifer E. , Dugan Aisling S. , Mercurio Arthur M. 
Published: December 2005

Abstract
The α6β4 integrin has been widely implicated in carcinoma function in vitro; however, in vivo data are scarce. To determine the importance of α6β4 in tumor progression, a SUM-159 breast carcinoma cell line that is essentially devoid of α6β4 expression was generated using an RNA interference strategy. Loss of α6β4 expression inhibits colony formation in soft agar assays, suggesting a vital role for α6β4 in survival signaling and anchorage-independent growth. Orthotopic injection of the β4-deficient cell line into the mammary fat pad of immunocompromised mice yielded significantly fewer and smaller tumors than the control cell line, revealing a role for the α6β4 integrin in tumor formation. Under conditions that mimicked the in vivo environment, decreased expression of the α6β4 integrin led to enhanced apoptosis as determined by the percentage of Annexin V-FITC+, PI− cells and the presence of caspase-3 cleavage products. Recombinant vascular endothelial growth factor (VEGF) significantly inhibited the cell death observed in the β4-deficient cell line, demonstrating the importance of VEGF expression in this survival pathway. Furthermore, loss of α6β4 expression leads to enhanced apoptosis and reduced expression of VEGF in breast carcinoma cells in vivo. Importantly, the specificity of α6β4 in both the in vitro and in vivo assays showed that reexpression of the β4 subunit into the β4-deficient cell line could rescue the functional phenotype. Taken together, these data implicate the α6β4 integrin in tumor formation by regulating tumor cell survival in a VEGF-dependent manner.
Interruption of Homologous Desensitization in Cyclic Guanosine 3′,5′-Monophosphate Signaling Restores Colon Cancer Cytostasis by Bacterial Enterotoxins
Authors: Pitari Giovanni M. , Baksh Ronnie I. , Harris David M. , Li Peng , Kazerounian Shiva , Waldman Scott A. 
Published: December 2005

AbstractBacterial diarrheagenic heat-stable enterotoxins induce colon cancer cell cytostasis by targeting guanylyl cyclase C (GCC) signaling. Anticancer actions of these toxins are mediated by cyclic guanosine 3′,5′-monophosphate (cGMP)–dependent influx of Ca2+ through cyclic nucleotide-gated channels. However, prolonged stimulation of GCC produces resistance in tumor cells to heat-stable enterotoxin–induced cytostasis. Resistance reflects rapid (tachyphylaxis) and slow (bradyphylaxis) mechanisms of desensitization induced by cGMP. Tachyphylaxis is mediated by cGMP-dependent protein kinase, which limits the conductance of cyclic nucleotide-gated channels, reducing the influx of Ca2+ propagating the antiproliferative signal from the membrane to the nucleus. In contrast, bradyphylaxis is mediated by cGMP-dependent allosteric activation of phosphodiesterase 5, which shapes the amplitude and duration of heat-stable enterotoxin–dependent cyclic nucleotide accumulation required for cytostasis. Importantly, interruption of tachyphylaxis and bradyphylaxis restores cancer cell cytostasis induced by heat-stable enterotoxins. Thus, regimens that incorporate cytostatic bacterial enterotoxins and inhibitors of cGMP-mediated desensitization offer a previously unrecognized therapeutic paradigm for treatment and prevention of colorectal cancer.
Suppression of Metastatic Colonization by the Context-Dependent Activation of the c-Jun NH2-Terminal Kinase Kinases JNKK1/MKK4 and MKK7
Authors: Vander Griend Donald J. , Kocherginsky Masha , Hickson Jonathan A. , Stadler Walter M. , Lin Anning , Rinker-Schaeffer Carrie W. 
Published: December 2005

Abstract
Advances in clinical, translational, and basic studies of metastasis have identified molecular changes associated with specific facets of the metastatic process. Studies of metastasis suppressor gene function are providing a critical mechanistic link between signaling cascades and biological outcomes. We have previously identified c-Jun NH2-terminal kinase (JNK) kinase 1/mitogen-activated protein kinase (MAPK) kinase 4 (JNKK1/MKK4) as a prostate cancer metastasis suppressor gene. The JNKK1/MKK4 protein is a dual-specificity kinase that has been shown to phosphorylate and activate the JNK and p38 MAPKs in response to a variety of extracellular stimuli. In this current study, we show that the kinase activity of JNKK1/MKK4 is required for suppression of overt metastases and is sufficient to prolong animal survival in the AT6.1 model of spontaneous metastasis. Ectopic expression of the JNK-specific kinase MKK7 suppresses the formation of overt metastases, whereas the p38-specific kinase MKK6 has no effect. In vivo studies show that both JNKK1/MKK4 and MKK7 suppress the formation of overt metastases by inhibiting the ability of disseminated cells to colonize the lung (secondary site). Finally, we show that JNKK1/MKK4 and MKK7 from disseminated tumor cells are active in the lung but not in the primary tumor, providing a biochemical explanation for why their expression specifically suppressed metastasis while exerting no effect on the primary tumor. Taken together, these studies contribute to a mechanistic understanding of the context-dependent function of metastasis regulatory proteins.
The Octamer Binding Transcription Factor Oct-1 Is a Stress Sensor
Authors: Tantin Dean , Schild-Poulter Caroline , Wang Victoria , Haché Robert J.G. , Sharp Phillip A. 
Published: December 2005

AbstractThe POU-domain transcription factor Oct-1 is widely expressed in adult tissues and has been proposed to regulate a large group of target genes. Microarray expression profiling was used to evaluate gene expression changes in Oct-1-deficient mouse fibroblasts. A number of genes associated with cellular stress exhibited altered expression. Consistent with this finding, Oct-1-deficient fibroblasts were hypersensitive to γ radiation, doxorubicin, and hydrogen peroxide and harbored elevated reactive oxygen species. Expression profiling identified a second group of genes dysregulated in Oct-1-deficient fibroblasts following irradiation, including many associated with oxidative and metabolic stress. A number of these genes contain octamer sequences in their immediate 5′ regulatory regions, some of which are conserved in human. These results indicate that Oct-1 modulates the activity of genes important for the cellular response to stress.
Breast Cancer–Associated PIK3CA Mutations Are Oncogenic in Mammary Epithelial Cells
Authors: Isakoff Steven J. , Engelman Jeffrey A. , Irie Hanna Y. , Luo Ji , Brachmann Saskia M. , Pearline Rachel V. , Cantley Lewis C. , Brugge Joan S. 
Published: December 2005

Abstract
Activation of the phosphoinositide 3-kinase (PI3K) pathway has been implicated in the pathogenesis of a variety of cancers. Recently, mutations in the gene encoding the p110α catalytic subunit of PI3K (PIK3CA) have been identified in several human cancers. The mutations primarily result in single amino acid substitutions, with &gt;85% of the mutations in either exon 9 or 20. Multiple studies have shown that these mutations are observed in 18% to 40% of breast cancers. However, the phenotypic effects of these PIK3CA mutations have not been examined in breast epithelial cells. Herein, we examine the activity of the two most common variants, E545K and H1047R, in the MCF-10A immortalized breast epithelial cell line. Both variants display higher PI3K activity than wild-type p110α yet remain sensitive to pharmacologic PI3K inhibition. In addition, expression of p110α mutants in mammary epithelial cells induces multiple phenotypic alterations characteristic of breast tumor cells, including anchorage-independent proliferation in soft agar, growth factor–independent proliferation, and protection from anoikis. Expression of these mutant p110α isoforms also confers increased resistance to paclitaxel and induces abnormal mammary acinar morphogenesis in three-dimensional basement membrane cultures. Together, these data support the notion that the cancer-associated mutations in PIK3CA may significantly contribute to breast cancer pathogenesis and represent attractive targets for therapeutic inhibition.