bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional Expression and Mutations of c-Met and Its Therapeutic Inhibition with SU11274 and Small Interfering RNA in Non–Small Cell Lung Cancer
Authors: Ma Patrick C. , Jagadeeswaran Ramasamy , Jagadeesh Simha , Tretiakova Maria S. , Nallasura Vidya , Fox Edward A. , Hansen Mark , Schaefer Erik , Naoki Katsuhiko , Lader Alan , Richards William , Sugarbaker David , Husain Aliya N. , Christensen James G. , Salgia Ravi 
Published: September 2005

Abstract
Non–small cell lung cancer (NSCLC) is a difficult disease to treat. The c-Met receptor is an attractive potential target for novel therapeutic inhibition in human cancers. We provide strong evidence that c-Met is overexpressed, activated, and sometimes mutated in NSCLC cell lines and tumor tissues. Expression of c-Met was found in all (100%) of the NSCLC tumor tissues examined (n = 23) and most (89%) of the cell lines (n = 9). Sixty-one percent of tumor tissues strongly expressed total c-Met, especially adenocarcinoma (67%). Specific expression of phospho-Met (p-Met) [Y1003] and [Y1230/1234/1235] was seen by immunohistochemistry. p-Met expression was preferentially observed at the NSCLC tumor invasive fronts. c-Met alterations were identified within the semaphorin domain (E168D, L299F, S323G, and N375S) and the juxtamembrane domain (R988C, R988C + T1010I, S1058P, and alternative splice product skipping entire juxtamembrane domain) of a NSCLC cell line and adenocarcinoma tissues. We validated c-Met as potential therapeutic target using small interfering RNA down-regulation of the receptor expression by 50% to 60% in NSCLC cells. This led to inhibition of p-Met and phospho-AKT and up to 57.1 ± 7.2% cell viability inhibition at 72 hours. The selective small molecule inhibitor of c-Met SU11274 inhibited cell viability in c-Met-expressing NSCLC cells. SU11274 also abrogated hepatocyte growth factor–induced phosphorylation of c-Met and its downstream signaling. Here, we provide first direct evidence by small interfering RNA targeting and small molecule inhibitor that c-Met is important in NSCLC biology and biochemistry. These results indicate that c-Met inhibition will be an important therapeutic strategy against NSCLC to improve its clinical outcome.
RASSF1A Suppresses the c-Jun-NH2-Kinase Pathway and Inhibits Cell Cycle Progression
Authors: Whang Young Mi , Kim Yeul Hong , Kim Jun Suk , Yoo Young Do 
Published: September 2005

Abstract
Some oncogenes, such as activated Ras, cause the malignant transformation of lung cells. c-Jun-NH2-kinase (JNK) activation is essential for the oncogenic function of these cells. In this study, we show that RASSF1A inhibits the growth of lung cancer cells by blocking the JNK pathway. The exogenous expression of RASSF1A suppressed JNK phosphorylation, and cells stably transfected with RASSF1A showed reduced JNK and c-Jun phosphorylation and Cyclin D1 down-regulation. An in vitro kinase assay showed that the exogenous expression of RASSF1A inhibited JNK activity and that JNK activity suppression due to ectopically expressed RASSF1A was revived by RASSF1A siRNA treatment. Based on our data, we suggest that RASSF1A exerts a tumor-suppressing effect by blocking oncogene-mediated JNK activation in lung cells.
Histone Deacetylase Inhibitors Decrease DNA Methyltransferase-3B Messenger RNA Stability and Down-regulate De novo DNA Methyltransferase Activity in Human Endometrial Cells
Authors: Xiong Yuning , Dowdy Sean C. , Podratz Karl C. , Jin Fan , Attewell John R. , Eberhardt Norman L. , Jiang Shi-Wen 
Published: September 2005

Abstract
It is well known that the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) acts synergistically with the DNA methyltransferase (DNMT) inhibitor 5-aza-2′-deoxycytidine (ADC) to reactivate DNA methylation-silenced genes. Moreover, in several studies, TSA was capable of inducing DNA demethylation even in the absence of ADC. Here we describe a mechanism by which HDAC inhibitors affect DNA methylation through their regulation on DNMT3B, a methyltransferase responsible for de novo DNA methylation. Using quantitative real-time PCR and Western blot analysis, we show that TSA down-regulates DNMT3B mRNA and protein expression in human endometrial cancer cells. This decrease in DNMT3B mRNA results in a significant reduction in de novo methylation activities. Further experiments indicated that TSA decreases DNMT3B mRNA stability and reduces its half-life from ∼4 to 2.5 hours. We established that protein synthesis is required for posttranscriptional regulation, suggesting the involvement of an RNase and/or key mRNA stabilization factor(s) controlling the DNMT3B mRNA stability. Therefore, TSA may not only modify histone acetylation, but also potentially alter DNA methylation. Since the HDAC inhibitors are frequently used in epigenetic studies and are considered to be promising anticancer drugs, these new findings will have implications in both laboratory and clinical settings.
Targeted Measles Virus Vector Displaying Echistatin Infects Endothelial Cells via αvβ3 and Leads to Tumor Regression
Authors: Hallak Louay K. , Merchan Jaime R. , Storgard Chris M. , Loftus Joseph C. , Russell Stephen J. 
Published: September 2005

Abstract
Targeting tumor-associated vascular endothelium by replication-competent viral vectors is a promising strategy for cancer gene therapy. Here we describe the development of a viral vector based on the Edmonston vaccine strain of measles virus targeted to integrin αvβ3, which is expressed abundantly on activated but not quiescent vascular endothelium. We displayed a disintegrin, M28L echistatin that binds with a high affinity to integrin αvβ3 on the COOH terminus of the viral attachment (H) protein and rescued the replication-competent recombinant virus by reverse genetics. The new targeted virus was named measles virus echistatin vector (MV-ERV). Its native binding to CD46 was purposefully retained to allow virus infection of tumor cells expressing this receptor. MV-ERV correctly displayed echistatin on the outer surface of its envelope and produced interesting ring formation phenomena due to cell detachment upon infection of susceptible Vero cells in vitro. MV-ERV grew to 106 plaque-forming units/mL, slightly lower than the parental Edmonston strain of measles virus (MV-Edm), but it selectively infected Chinese hamster ovary cells expressing integrin αvβ3. It also selectively infected both bovine and human endothelial cells on matrigels and unlike MV-Edm, MV-ERV infected newly formed blood vessels in chorioallantoic membrane assays. In animal models, MV-ERV but not the control MV-Edm caused the regression of s.c. xenografts of resistant multiple myeloma tumors (MM1) in severe combined immunodeficient mice. The tumors were either completely eradicated or their growth was significantly retarded. The specificity, potency, and feasibility of MV-ERV infection clearly show the potential use of MV-ERV in gene therapy for targeting tumor-associated vasculature for the treatment of solid tumors.
A Novel Telomere Structure in a Human Alternative Lengthening of Telomeres Cell Line
Authors: Marciniak Robert A. , Cavazos David , Montellano Richard , Chen Qijun , Guarente Leonard , Johnson F. Brad 
Published: September 2005

Abstract
Cancer cells require mechanisms to maintain telomeres. Most use telomerase, but 5% to 20% of tumors use alternative lengthening of telomeres (ALT), a telomerase-independent mechanism that seems to depend on recombination. ALT is characterized by amplification of telomere TTAGGG repeats to lengths beyond 50 kb, by elevated rates of telomere recombination, and by nuclear structures called ALT-associated promyelocytic leukemia bodies. In Saccharomyces cerevisiae, survivors of telomerase inactivation also use recombination to maintain telomeres. There are two types of survivors, which differ in telomere structure. The first possesses telomere repeats and the Y′ subtelomeric element amplified together as a tandem array at chromosome termini (type I), and the other possesses amplification of telomeric repeats alone (type II), similar to previously described human ALT cells. Here, we describe the first human ALT cell line having “tandem array” telomeres with a structure similar to that of type I yeast survivors. The chromosome termini consist of a repeat unit containing ∼2.5 kb of SV40 DNA and a variable amount of TTAGGG sequence repeated in tandem an average of 10 to 20 times. Similar to previously described ALT cells, they show evidence of telomere recombination, but unlike standard ALT cells, they lack ALT-associated promyelocytic leukemia bodies and their telomeres are transcribed. These findings have implications for the pathogenesis and diagnosis of cancer.
Epigenetic Reactivation of Tumor Suppressor Genes by a Novel Small-Molecule Inhibitor of Human DNA Methyltransferases
Authors: Brueckner Bodo , Garcia Boy Regine , Siedlecki Pawel , Musch Tanja , Kliem H. Christian , Zielenkiewicz Piotr , Suhai Sandor , Wiessler Manfred , Lyko Frank 
Published: September 2005

Abstract
DNA methylation regulates gene expression in normal and malignant cells. The possibility to reactivate epigenetically silenced genes has generated considerable interest in the development of DNA methyltransferase inhibitors. Here, we provide a detailed characterization of RG108, a novel small molecule that effectively blocked DNA methyltransferases in vitro and did not cause covalent enzyme trapping in human cell lines. Incubation of cells with low micromolar concentrations of the compound resulted in significant demethylation of genomic DNA without any detectable toxicity. Intriguingly, RG108 caused demethylation and reactivation of tumor suppressor genes, but it did not affect the methylation of centromeric satellite sequences. These results establish RG108 as a DNA methyltransferase inhibitor with fundamentally novel characteristics that will be particularly useful for the experimental modulation of epigenetic gene regulation.
Mimicry of a Cellular Low Energy Status Blocks Tumor Cell Anabolism and Suppresses the Malignant Phenotype
Authors: Swinnen Johannes V. , Beckers Annelies , Brusselmans Koen , Organe Sophie , Segers Joanna , Timmermans Leen , Vanderhoydonc Frank , Deboel Ludo , Derua Rita , Waelkens Etienne , De Schrijver Ellen , Van de Sande Tine , Noël Agnès , Foufelle Fabienne , Verhoeven Guido 
Published: September 2005

AbstractAggressive cancer cells typically show a high rate of energy-consuming anabolic processes driving the synthesis of lipids, proteins, and DNA. Here, we took advantage of the ability of the cell-permeable nucleoside 5-aminoimidazole-4-carboxamide (AICA) riboside to increase the intracellular levels of AICA ribotide, an AMP analogue, mimicking a low energy status of the cell. Treatment of cancer cells with AICA riboside impeded lipogenesis, decreased protein translation, and blocked DNA synthesis. Cells treated with AICA riboside stopped proliferating and lost their invasive properties and their ability to form colonies. When administered in vivo, AICA riboside attenuated the growth of MDA-MB-231 tumors in nude mice. These findings point toward a central tie between energy, anabolism, and cancer and suggest that the cellular energy sensing machinery in cancer cells is an exploitable target for cancer prevention and/or therapy.
Survivin as a Radioresistance Factor, and Prognostic and Therapeutic Target for Radiotherapy in Rectal Cancer
Authors: Rödel Franz , Hoffmann Jörg , Distel Luitpold , Herrmann Martin , Noisternig Timmo , Papadopoulos Thomas , Sauer Rolf , Rödel Claus 
Published: September 2005

Abstract
Apoptosis levels have been shown to predict tumor response to preoperative radiochemotherapy in rectal cancer. Recently, the prominent role of survivin, a structurally unique member of the inhibitor of apoptosis protein family, has been shown in colorectal cancer tumorigenesis and prognosis. In this study, we investigated whether survivin plays a direct role in mediating radiation resistance. We used short interfering RNA molecules to decrease survivin in radioresistant SW480 and intermediately radioresistant HCT-15 colorectal cancer cells. This resulted in a significant decrease of survivin mRNA and protein expression with a maximum at 24 to 48 hours after transfection. If irradiated during this sensitive period, an increased percentage of apoptotic cells and an increased caspase 3/7 activity in parallel with a decreased cell viability and a reduced clonogenic survival was shown. These effects were more pronounced in the radioresistant SW480 cell line with a radiation-induced cytotoxicity enhancement factor at 10% and 50% survival of 1.8 to 2.2 for SW480 and 1.5 to 1.7 for HCT-15, respectively. Furthermore, transfection with survivin short interfering RNA increased levels of G2-M arrest and levels of DNA double-strand breaks in irradiated cells. These observations indicate that cell cycle and DNA repair mechanisms may be associated with apoptosis induction in tumor cells that are otherwise resistant to killing by radiation. In a translational study of 59 patients with rectal cancer treated with a combination of radiotherapy and chemotherapy, increased survivin expression was inversely related to the levels of apoptosis, and was also associated with a significantly higher risk of a local tumor recurrence.
Multiphoton Microscopy of Endogenous Fluorescence Differentiates Normal, Precancerous, and Cancerous Squamous Epithelial Tissues
Authors: Skala Melissa C. , Squirrell Jayne M. , Vrotsos Kristin M. , Eickhoff Jens C. , Gendron-Fitzpatrick Annette , Eliceiri Kevin W. , Ramanujam Nirmala 
Published: September 2005

Abstract
This study characterizes the morphologic features and the endogenous fluorescence in the stratified squamous epithelia of the 7,12-dimethylbenz(a)anthracene-treated hamster cheek pouch model of carcinogenesis using multiphoton laser scanning microscopy (MPLSM). MPLSM allows high-resolution, three-dimensional image data to be collected deeper within thick tissue samples with reduced phototoxicity compared with single-photon imaging. Three-dimensional image stacks of normal (n = 13), precancerous (dysplasia, n = 12; carcinoma in situ, n = 9) and cancerous tissue [nonpapillary squamous cell carcinoma (SCC), n = 10, and papillary SCC, n = 7] sites in the hamster cheek pouch were collected in viable, unsectioned tissue biopsies at a two-photon excitation wavelength of 780 nm. Five features were quantified from the MPLSM images. These included nuclear density versus depth, keratin layer thickness, epithelial thickness, and the fluorescence per voxel in the keratin and epithelial layers. Statistically significant differences in all five features were found between normal and both precancerous and cancerous tissues. The only exception to this was a lack of statistically significant differences in the keratin fluorescence between normal tissues and papillary SCCs. Statistically significant differences were also observed in the epithelial thickness of dysplasia and carcinoma in situ, and in the keratin layer thickness of dysplasia and SCCs (both nonpapillary and papillary). This work clearly shows that three-dimensional images from MPLSM of endogenous tissue fluorescence can effectively distinguish between normal, precancerous, and cancerous epithelial tissues. This study provides the groundwork for further exploration into the application of multiphoton fluorescence endoscopy in a clinical setting.
Tbx2 Is Overexpressed and Plays an Important Role in Maintaining Proliferation and Suppression of Senescence in Melanomas
Authors: Vance Keith W. , Carreira Suzanne , Brosch Gerald , Goding Colin R. 
Published: September 2005

Abstract
The INK4a and ARF genes found at the CDKN2A locus are key effectors of cellular senescence that is believed to act as a powerful anticancer mechanism. Accordingly, mutations in these genes are present in a wide variety of spontaneous human cancers and CDKN2A germ line mutations are found in familial melanoma. The TBX2 gene encoding a key developmental transcription factor is amplified in pancreatic cancer cell lines and preferentially amplified and overexpressed in BRCA1 and BRCA2 mutated breast tumors. Overexpression of Tbx2 and the related factor Tbx3, which is also overexpressed in breast cancer and melanomas, can suppress senescence in defined experimental systems through repression of ARF expression. However, it is not known how Tbx2 mediates its repressive effect nor whether endogenous Tbx2 or Tbx3 perform a similar antisenescence function in transformed cells. This is a particularly important question because the loss of CDKN2A in many human cancers would, in principle, bypass the requirement for Tbx2/3-mediated repression of ARF in suppressing senescence. We show here that Tbx2 is overexpressed in melanoma cell lines and that Tbx2 targets histone deacetylase 1 to the p21Cip1 (CDKN1A) initiator. Strikingly, expression of an inducible dominant-negative Tbx2 (dnTbx2) leads to displacement of histone deacetylase 1, up-regulation of p21Cip1 expression, and the induction of replicative senescence in CDKN2A-null B16 melanoma cells. In human melanoma cells, expression of dnTbx2 leads to severely reduced growth and induction of senescence-associated heterochromatin foci. The results suggest that the activity of endogenous Tbx2 is critically required to maintain proliferation and suppress senescence in melanomas.
A Novel Transgenic Mouse Model Reveals Humanlike Regulation of an 8-kbp Human TERT Gene Promoter Fragment in Normal and Tumor Tissues
Authors: Ritz Julia M. , Kühle Olaf , Riethdorf Sabine , Sipos Bence , Deppert Wolfgang , Englert Christoph , Günes Cagatay 
Published: September 2005

Abstract
Telomerase activity is repressed in most human somatic tissues during differentiation processes but strongly up-regulated in most human tumors. Regulation of human telomerase activity primarily occurs at the level of transcriptional initiation of the TERT gene, which encodes the catalytic subunit of telomerase. We have generated a novel transgenic mouse model to study the regulation of the human TERT gene promoter in an in vivo system. For this purpose, we have cloned an 8.0-kbp human TERT promoter fragment in front of the bacterial lacZ reporter gene (hTERTp-lacZ), which encodes the β-galactosidase enzyme. Expression of the reporter gene was monitored by reverse transcription–PCR analysis, 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside staining of whole mount preparations, and histologic sections. We find that the activity of the human TERT promoter in most normal mouse tissues recapitulates the expression of the hTERT gene in normal human tissues and is under tighter control when compared with the endogenous mouse TERT gene expression. In testis, where highest lacZ expression was observed, the expression of the reporter gene was restricted to the spermatogonial stem cells and the spermatocytes. Intriguingly, we find increased levels of lacZ expression in mammary tumors of hTERTp-lacZ × p53+/− bitransgenic mouse mammary tumor model. Thus, this transgenic mouse model provides a suitable in vivo system to analyze the expression of the human TERT gene under physiologic conditions and during tumorigenesis.
DNA Ligase III as a Candidate Component of Backup Pathways of Nonhomologous End Joining
Authors: Wang Huichen , Rosidi Bustanur , Perrault Ronel , Wang Minli , Zhang Lihua , Windhofer Frank , Iliakis George 
Published: September 2005

Abstract
Biochemical and genetic studies support the view that the majority of DNA double-strand breaks induced in the genome of higher eukaryotes by ionizing radiation are removed by two pathways of nonhomologous end joining (NHEJ) termed D-NHEJ and B-NHEJ. Whereas D-NHEJ depends on the activities of the DNA-dependent protein kinase and DNA ligase IV/XRCC4, components of B-NHEJ have not been identified. Using extract fractionation, we show that the majority of DNA end joining activity in extracts of HeLa cells derives from DNA ligase III. DNA ligase III fractionates through two columns with the maximum in DNA end joining activity and its depletion from the extract causes loss of activity that can be recovered by the addition of purified enzyme. The same fractionation protocols provide evidence for an additional factor strongly enhancing DNA end joining and shifting the product spectrum from circles to multimers. An in vivo plasmid assay shows that DNA ligase IV–deficient mouse embryo fibroblasts retain significant DNA end joining activity that can be reduced by up to 80% by knocking down DNA ligase III using RNA interference. These in vivo and in vitro observations identify DNA ligase III as a candidate component for B-NHEJ and point to additional factors contributing to NHEJ efficiency.
Hypersialylation of β1 Integrins, Observed in Colon Adenocarcinoma, May Contribute to Cancer Progression by Up-regulating Cell Motility
Authors: Seales Eric C. , Jurado Gustavo A. , Brunson Brian A. , Wakefield John K. , Frost Andra R. , Bellis Susan L. 
Published: September 2005

Abstract
Colon adenocarcinomas are known to express elevated levels of α2-6 sialylation and increased activity of ST6Gal-I, the Golgi glycosyltransferase that creates α2-6 linkages. Elevated ST6Gal-I positively correlates with metastasis and poor survival, and therefore ST6Gal-I–mediated hypersialylation likely plays a role in colorectal tumor invasion. Previously we found that oncogenic ras (present in roughly 50% of colon adenocarcinomas) up-regulates ST6Gal-I and, in turn, increases sialylation of β1 integrin adhesion receptors in colon epithelial cells. However, we wanted to know if this pattern held true in vivo and, if so, how β1 hypersialylation might contribute to colon tumor progression. In the present study, we find that β1 integrins from colon adenocarcinomas consistently carry higher levels of α2-6 sialic acid. To explore the effects of increased α2-6 sialylation on β1-integrin function, we stably expressed ST6Gal-I in a colon epithelial cell line lacking endogenous ST6Gal-I. ST6Gal-I expressors (with α2-6 sialylated β1 integrins) exhibited up-regulated attachment to collagen I and laminin and increased haptotactic migration toward collagen I, relative to parental cells (with completely unsialylated β1 integrins). Blockade of ST6Gal-I expression with short interfering RNA reversed collagen binding back to the level of ST6Gal-I nonexpressors, confirming that α2-6 sialylation regulates β1 integrin function. Finally, we show that β1 integrins from ST6Gal-I expressors have increased association with talin, a marker for integrin activation. Collectively, these findings suggest that β1 hypersialylation may augment colon tumor progression by altering cell preference for certain extracellular matrix milieus, as well as by stimulating cell migration.