bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elevated CRAF as a Potential Mechanism of Acquired Resistance to BRAF Inhibition in Melanoma
Authors: Montagut Clara , Sharma Sreenath V. , Shioda Toshi , McDermott Ultan , Ulman Matthew , Ulkus Lindsey E. , Dias-Santagata Dora , Stubbs Hannah , Lee Diana Y. , Singh Anurag , Drew Lisa , Haber Daniel A. , Settleman Jeffrey 
Published: June 2008

Abstract
Activating BRAF kinase mutations arise in ∼7% of all human tumors, and preclinical studies have validated the RAF–mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase–ERK signaling cascade as a potentially important therapeutic target in this setting. Selective RAF kinase inhibitors are currently undergoing clinical development, and based on the experience with other kinase-targeted therapeutics, it is expected that clinical responses to these agents, if observed, will lead to the eventual emergence of drug resistance in most cases. Thus, it is important to establish molecular mechanisms underlying such resistance to develop effective therapeutic strategies to overcome or prevent drug resistance. To anticipate potential mechanisms of acquired resistance to RAF inhibitors during the course of treatment, we established drug-resistant clones from a human melanoma-derived cell line harboring the recurrent V600E activating BRAF mutation, which exhibits exquisite sensitivity to AZ628, a selective RAF kinase inhibitor. We determined that elevated CRAF protein levels account for the acquisition of resistance to AZ628 in these cells, associated with a switch from BRAF to CRAF dependency in tumor cells. We also found that elevated CRAF protein levels may similarly contribute to primary insensitivity to RAF inhibition in a subset of BRAF mutant tumor cells. Interestingly, AZ628-resistant cells demonstrating either primary drug insensitivity or acquired drug resistance exhibit exquisite sensitivity to the HSP90 inhibitor geldanamycin. Geldanamycin effectively promotes the degradation of CRAF, thereby revealing a potential therapeutic strategy to overcome resistance to RAF inhibition in a subset of BRAF mutant tumors. [Cancer Res 2008;68(12):4853–61]
Serine/Arginine Protein–Specific Kinase 2 Promotes Leukemia Cell Proliferation by Phosphorylating Acinus and Regulating Cyclin A1
Authors: Jang Sung-Wuk , Yang Seung-ju , Ehlén Åsa , Dong Shaozhong , Khoury Hanna , Chen Jing , Persson Jenny L. , Ye Keqiang 
Published: June 2008

Abstract
Serine/arginine (SR) protein–specific kinase (SRPK), a family of cell cycle–regulated protein kinases, phosphorylate SR domain–containing proteins in nuclear speckles and mediate the pre-mRNA splicing. However, the physiologic roles of this event in cell cycle are incompletely understood. Here, we show that SRPK2 binds and phosphorylates acinus, an SR protein essential for RNA splicing, and redistributes it from the nuclear speckles to the nucleoplasm, resulting in cyclin A1 but not A2 up-regulation. Acinus S422D, an SRPK2 phosphorylation mimetic, enhances cyclin A1 transcription, whereas acinus S422A, an unphosphorylatable mutant, blocks the stimulatory effect of SRPK2. Ablation of acinus or SRPK2 abrogates cyclin A1 expression in leukemia cells and arrest cells at G1 phase. Overexpression of acinus or SRPK2 increases leukemia cell proliferation. Furthermore, both SRPK2 and acinus are overexpressed in some human acute myelogenous leukemia patients and correlate with elevated cyclin A1 expression levels, fitting with the oncogenic activity of cyclin A1 in leukemia. Thus, our findings establish a molecular mechanism by which SR splicing machinery regulates cell cycle and contributes to leukemia tumorigenesis. [Cancer Res 2008;68(12):4559–70]
Development of a Preclinical Model of Spontaneous Human Melanoma Central Nervous System Metastasis
Authors: Cruz-Munoz William , Man Shan , Xu Ping , Kerbel Robert S. 
Published: June 2008

Abstract
Metastatic spread of melanoma to the central nervous system (CNS) is associated with dismal prognosis. Preclinical testing of novel therapeutic approaches would be aided by the development of appropriate models of spontaneous CNS metastasis arising from primary tumors. A highly metastatic variant of the WM239A human melanoma cell line, designated 113/6-4L, was generated and used to test the efficacy of long-term, low-dose metronomic cyclophosphamide and vinblastine chemotherapy on advanced established metastatic disease in sites such as liver, lungs, and lymph node. This treatment resulted in control of advanced, systemic disease and prolongation of survival. Among long-term surviving mice, 20% showed the presence of spontaneous brain metastases. Two cell lines (131/4-5B1 and 131/4-5B2) were generated from such metastases, which were found to spontaneously metastasize to brain parenchyma with occasional localization to leptomeninges, after orthotopic transplantation and removal of the primary tumor. The cell lines were found to have increased ability to proliferate in brain-conditioned medium and displayed enhanced adhesion to lung and brain endothelial cells. These findings represent the first report of spontaneous CNS metastases generated from primary tumors of any human cancer in mice, which heritably maintains this phenotype, and as such, the variant cell lines generated should aid studies in the biology and treatment of CNS metastases, especially of melanoma origin. [Cancer Res 2008;68(12):4500–5]
Hypoxia Increases Tumor Cell Shedding of MHC Class I Chain-Related Molecule: Role of Nitric Oxide
Authors: Siemens D. Robert , Hu Nianping , Sheikhi Abdol Karim , Chung Eugene , Frederiksen Lisa J. , Pross Hugh , Graham Charles H. 
Published: June 2008

Abstract
The MHC class I chain-related (MIC) molecules play important roles in tumor immune surveillance through their interaction with the NKG2D receptor on natural killer and cytotoxic T cells. Thus, shedding of the MIC molecules from the tumor cell membrane represents a potential mechanism of escape from NKG2D-mediated immune surveillance. Tumor hypoxia is associated with a poor clinical outcome for cancer patients. We show that hypoxia contributes to tumor cell shedding of MIC through a mechanism involving impaired nitric oxide (NO) signaling. Whereas hypoxia increased MIC shedding in human prostate cancer cells, activation of NO signaling inhibited hypoxia-mediated MIC shedding. Similar to incubation in hypoxia, pharmacologic inhibition of endogenous NO signaling increased MIC shedding. Parallel studies showed hypoxia-mediated tumor cell resistance to lysis by interleukin 2–activated peripheral blood lymphocytes (PBL) and NO-mediated attenuation of this resistance to lysis. Inhibition of NO production also led to resistance to PBL-mediated lysis. Interference of MIC-NKG2D interaction with a blocking anti-MIC antibody abrogated the effect of hypoxia and NO signaling on tumor cell sensitivity to PBL-mediated lysis. Finally, continuous transdermal delivery of the NO mimetic glyceryl trinitrate (7.3 μg/h) attenuated the growth of xenografted MIC-expressing human prostate tumors. These findings suggest that the hypoxic tumor microenvironment contributes to resistance to immune surveillance and that activation of NO signaling is of potential use in cancer immunotherapy. [Cancer Res 2008;68(12):4746–53]
Neo-Organoid of Marrow Mesenchymal Stromal Cells Secreting Interleukin-12 for Breast Cancer Therapy
Authors: Eliopoulos Nicoletta , Francois Moïra , Boivin Marie-Noëlle , Martineau Daniel , Galipeau Jacques 
Published: June 2008

Abstract
Bone marrow–derived mesenchymal stromal cells (MSCs), beneficial for regenerative medicine applications due to their wide differentiation capabilities, also hold promise as cellular vehicles for the delivery of therapeutic plasma-soluble gene products due to their ease of handling, expansion, and genetic engineering. We hypothesized that MSCs, gene enhanced to express interleukin-12 (IL-12) and then embedded in a matrix, may act as an anticancer neo-organoid when delivered s.c. in autologous/syngeneic hosts. We performed such experiments in mice and noted that primary murine MSCs retrovirally engineered to secrete murine IL-12 can significantly interfere with growth of 4T1 breast cancer cells in vivo, with a more substantial anticancer action achieved when these cells are embedded in a matrix. Plasma of mice that received the IL-12 MSC-containing neo-organoids showed increased levels of IL-12 and IFN-γ. Histopathologic analysis revealed less tumor cells in implants of 4T1 cells with IL-12 MSCs, and the presence of necrotic tumor islets and necrotic capillaries, suggesting antiangiogenesis. We also showed that the anticancer effect exerted by the IL-12 MSCs is immune mediated because it is absent in immunodeficient mice, is not due to systemic IL-12 delivery, and also occurs in a B16 melanoma model. This study therefore establishes the feasibility of using gene-enhanced MSCs in a cell-based neo-organoid approach for cancer treatment. [Cancer Res 2008;68(12):4810–8]
Early-Onset Lymphoma and Extensive Embryonic Apoptosis in Two Domain-Specific Fen1 Mice Mutants
Authors: Larsen Elisabeth , Kleppa Liv , Meza Trine J. , Meza-Zepeda Leonardo A. , Rada Christina , Castellanos Cesilie G. , Lien Guro F. , Nesse Gaute J. , Neuberger Michael S. , Laerdahl Jon K. , William Doughty Richard , Klungland Arne 
Published: June 2008

Abstract
Flap endonuclease 1 (FEN1) processes Okazaki fragments in lagging strand DNA synthesis, and FEN1 is involved in several DNA repair pathways. The interaction of FEN1 with the proliferating cell nuclear antigen (PCNA) processivity factor is central to the function of FEN1 in both DNA replication and repair. Here we present two gene-targeted mice with mutations in FEN1. The first mutant mouse carries a single amino acid point mutation in the active site of the nuclease domain of FEN1 (Fen1E160D/E160D), and the second mutant mouse contains two amino acid substitutions in the highly conserved PCNA interaction domain of FEN1 (Fen1ΔPCNA/ΔPCNA). Fen1E160D/E160D mice develop a considerably elevated incidence of B-cell lymphomas beginning at 6 months of age, particularly in females. By 16 months of age, more than 90% of the Fen1E160D/E160D females have tumors, primarily lymphomas. By contrast, Fen1ΔPCNA/ΔPCNA mouse embryos show extensive apoptosis in the forebrain and vertebrae area and die around stage E9.5 to E11.5. [Cancer Res 2008;68(12):4571–8]
Activated Cholinergic Signaling Provides a Target in Squamous Cell Lung Carcinoma
Authors: Song Pingfang , Sekhon Harmanjatinder S. , Fu Xiao Wen , Maier Michelle , Jia Yibing , Duan Jie , Proskosil Becky J. , Gravett Courtney , Lindstrom Jon , Mark Gregory P. , Saha Saurabh , Spindel Eliot R. 
Published: June 2008

Abstract
The binding of exogenous nicotine to nicotinic acetylcholine (ACh) receptors (nAChR) and the binding of endogenous ACh to both nAChR and muscarinic ACh receptors (mAChR) stimulate growth of both small cell and non–small cell lung carcinomas. Understanding how cholinergic signaling is up-regulated in lung cancer may suggest new therapeutic approaches. Analysis of 28 squamous cell lung carcinomas (SCC) showed increased levels of α5 and β3 nAChR mRNA and increased levels of ACh associated with increased levels of choline acetyltransferase mRNA and decreased cholinesterase mRNAs. Lynx1, an allosteric inhibitor of nAChR activity, was also decreased in SCC. Thus, cholinergic signaling is broadly increased in SCC caused by increased levels of receptors, increased levels of ligands, and decreased levels of receptor inhibitors. Partially explaining the cholinergic up-regulation seen in SCC, incubation of the H520 SCC cell line with nicotine increased levels of ACh secretion, increased expression of nAChR, and, as measured by electrophysiologic recording, increased activity of the expressed nAChR. Consistent with these effects, nicotine stimulated proliferation of H520 cells. One approach to blocking proliferative effects of nicotine and ACh on growth of lung cancers may be through M3 mAChR antagonists, which can limit the activation of mitogen-activated protein kinase that is caused by both nicotinic and muscarinic signaling. This was tested with the M3-selective muscarinic antagonist darifenacin. Darifenacin blocked nicotine-stimulated H520 growth in vitro and also blocked H520 growth in nude mice in vivo. Thus, cholinergic signaling is broadly up-regulated in SCC and blocking cholinergic signaling can limit basal and nicotine-stimulated growth of SCC. [Cancer Res 2008;68(12):4693–700]
Oncolytic Vesicular Stomatitis Viruses Are Potent Agents for Intravesical Treatment of High-Risk Bladder Cancer
Authors: Hadaschik Boris A. , Zhang Kaixin , So Alan I. , Fazli Ladan , Jia William , Bell John C. , Gleave Martin E. , Rennie Paul S. 
Published: June 2008

Abstract
Bladder cancer is the second most common genitourinary malignancy. At initial diagnosis, ∼70% of cases are non–muscle-invasive; however, current treatment options for superficial disease are of limited efficacy because many patients will develop recurrent tumors. The purpose of this study was to examine two replication-competent oncolytic vesicular stomatitis virus (VSV) strains as intravesical agents in an orthotopic murine model of high-grade bladder cancer. Four human bladder cancer cell lines (RT4, MGH-U3, UM-UC3, and KU-7) were treated with either wild-type VSV or a mutant Δ51M variant (AV3) in vitro. Both wild-type VSV and AV3, which has an impaired ability to shutdown innate immunity, preferentially killed the more aggressive, IFN-nonresponsive cell lines UM-UC3 and KU-7, whereas IFN-responsive RT4 and MGH-U3 cells were less susceptible. In vivo, KU-7-luc bladder tumor cells, which stably express firefly luciferase, were inoculated into nude mice by intravesical instillation and tumor growth was quantified using bioluminescence imaging. Mice with established xenografts were administered VSV intravesically on days 4, 9, and 14, and necropsy was performed after 3 weeks. AV3 as well as wild-type VSV significantly inhibited KU-7-luc tumor growth by 90% (AV3) and 98% (wild-type), respectively, as compared with controls treated with UV-inactivated VSV. Despite using immunocompromised hosts, there was no evidence of toxicity in either group. In conclusion, VSV instillation therapy showed promising antitumor activity and safety in an orthotopic model of bladder cancer. These findings provide preclinical proof-of-principle for the intravesical use of VSV against non–muscle-invasive bladder cancer, especially in IFN-refractory patients. [Cancer Res 2008;68(12):4506–10]
Genome-Wide Analysis of Aromatase Inhibitor-Resistant, Tamoxifen-Resistant, and Long-Term Estrogen-Deprived Cells Reveals a Role for Estrogen Receptor
Authors: Masri Selma , Phung Sheryl , Wang Xin , Wu Xiwei , Yuan Yate-Ching , Wagman Lawrence , Chen Shiuan 
Published: June 2008

AbstractAcquired resistance to either tamoxifen or aromatase inhibitors (AI) develops after prolonged treatment in a majority of hormone-responsive breast cancers. In an attempt to further elucidate mechanisms of acquired resistance to AIs, MCF-7aro cells resistant to letrozole (T+LET R), anastrozole (T+ANA R), and exemestane (T+EXE R), as well as long-term estrogen deprived (LTEDaro) and tamoxifen-resistant (T+TAM R) lines were generated. This is the first complete panel of endocrine therapy–resistant cell lines, which were generated as multiple independent biological replicates for unbiased genome-wide analysis using affymetrix microarrays. Although similarities are apparent, microarray results clearly show gene signatures unique to AI-resistance were inherently different from LTEDaro and T+TAM R gene expression profiles. Based on hierarchical clustering, unique estrogen-responsive gene signatures vary depending on cell line, with some genes up-regulated in all lines versus other genes up-regulated only in the AI-resistant lines. Characterization of these resistant lines showed that LTEDaro, T+LET R, and T+ANA R cells contained a constitutively active estrogen receptor (ER)α that does not require estrogen for activation. This ligand-independent activation of ER was not observed in the parental cells, as well as T+EXE R and T+TAM R cells. Further characterization of these resistant lines was performed using cell cycle analysis, immunofluorescence experiments to visualize ER subcellular localization, as well as cross-resistance studies to determine second-line inhibitor response. Using this well-defined model system, our studies provide important information regarding differences in resistance mechanisms to AIs, TAM, and LTEDaro, which are critical in overcoming resistance when treating hormone-responsive breast cancers. [Cancer Res 2008;68(12):4910–8]
Gain of Oncogenic Function of p53 Mutants Induces Invasive Phenotypes in Human Breast Cancer Cells by Silencing CCN5/WISP-2
Authors: Dhar Gopal , Banerjee Snigdha , Dhar Kakali , Tawfik Ossama , Mayo Matthew S. , VanVeldhuizen Peter J. , Banerjee Sushanta K. 
Published: June 2008

Abstract
CCN5/WISP-2 is overexpressed in noninvasive breast cancer cells and tissue samples, whereas its expression is minimal or undetected in invasive conditions. CCN5/WISP-2 has been considered as an antiinvasive gene because CCN5/WISP-2 silencing augments the invasive phenotypes in vitro. However, the mechanism of silencing of CCN5 during the progression of the disease has been elusive. Because p53 mutations are associated with breast cancer progression and have been shown to correlate inversely with CCN5/WISP-2 expression in other cancer cell types, the objective of this study was to explore whether p53 mutants suppress CCN5 expression in breast tumor cells resulting in the progression of this disease. We found CCN5 expression is inversely correlated with the mutational activation of p53 in human breast tumor cells. The ectopic expression of p53 mutants in ER-positive noninvasive breast tumor cells silenced the CCN5/WISP-2 expression and enhanced invasive phenotypes, including the induction of morphologic changes from the epithelial-to-mesenchymal type along with the alterations of hallmark proteins of these cell types and an augmentation of the migration of these cells. The suppression of CCN5 by the p53 mutants can be nullified by estrogen signaling in these cells through the transcriptional activation of the CCN5 gene. Moreover, the invasive changes can be imitated by blocking the CCN5/WISP-2 expression through RNA interference or can be reversed by the addition of CCN5/WISP-2 recombinant protein in the culture. Thus, these studies suggest that CCN5 inactivation could be an essential molecular event for p53 mutant–induced invasive phenotypes. [Cancer Res 2008;68(12):4580–7]
The Chemokine Receptor CXCR6 and Its Ligand CXCL16 Are Expressed in Carcinomas and Inhibit Proliferation
Authors: Meijer Joost , Ogink Janneke , Kreike Bas , Nuyten Dimitry , de Visser Karin E. , Roos Ed 
Published: June 2008

Abstract
The chemokine receptor CXCR6 and its ligand CXCL16 are involved in inflammation. Thus far, they were known to be expressed mainly by T cells and macrophages, respectively. However, we detected both in all of 170 human primary mammary carcinomas and at similar levels in all 8 human mammary carcinoma cell lines tested by microarray analysis. Expression was confirmed by reverse transcription-PCR and for the cell lines also by fluorescence-activated cell sorting analysis. CXCR6 and CXCL16 were also detected in several mouse and human mammary, colon, and pancreatic carcinoma cell lines. CXCL16 is a transmembrane protein from which the soluble chemokine can be cleaved off. The transmembrane form is present on the surface of the carcinoma cells. Surprisingly, suppression of either CXCR6 or CXCL16 led to greatly enhanced proliferation in vitro as well as in vivo, indicating that their interaction inhibits proliferation. This notion was verified using inhibitory antibodies and by introduction of CXCL16 into a rare CXCL16-negative cell line. The effect was mediated by the G protein–coupled receptor CXCR6 because it was blocked by the Gi protein inhibitor pertussis toxin. In contrast, the soluble CXCL16 chemokine enhanced proliferation, and this was also mediated by CXCR6 but not via Gi protein. It is remarkable that both CXCR6 and CXCL16 are expressed by all mammary carcinomas because cells that lose either acquire a growth advantage and should be selected during tumor progression. This suggests an unknown important role in tumor formation. Proteases, possibly macrophage derived, might convert inhibitory transmembrane CXCL16 into the stimulatory chemokine. [Cancer Res 2008;68(12):4701–8]
Salmonella Promoters Preferentially Activated Inside Tumors
Authors: Arrach Nabil , Zhao Ming , Porwollik Steffen , Hoffman Robert M. , McClelland Michael 
Published: June 2008

Abstract
Salmonella enterica and avirulent derivatives prefer solid tumors over normal tissue in animal models. The identification of endogenous Salmonella promoters that are preferentially activated in tumors could further our understanding of this phenomenon. Toward this goal, a random library of S. enterica typhimurium 14028 genomic DNA was cloned upstream of a promoterless gene encoding the green fluorescent protein (GFP) TurboGFP. A population of Salmonella containing this library was injected i.v. into tumor-free nude mice and into human PC3 prostate tumors growing subcutaneously in nude mice. After 2 days, fluorescence-activated cell sorting was used to enrich for bacterial clones expressing GFP from spleens or tumors. The resulting libraries were hybridized to an oligonucleotide tiling array of the Salmonella genome. Eighty-six intergenic regions were found to be enriched in tumor samples but not in spleen. Twenty of these candidate promoters were also detected in the sequences of 100 random clones from a library enriched for expression in bacteria growing in tumors. Three candidate promoter clones were individually tested in vivo, and enhanced GFP expression in bacteria growing in tumor relative to spleen was confirmed. Two of the three clones (pflE and ansB promoter regions) are known to be induced in hypoxic conditions that pertain to many tumors. For many of the other candidate promoters preferentially induced in bacteria growing in tumors, regulatory mechanisms may not be related to hypoxia. The expression of therapeutics in Salmonella under the regulation of one or more promoters that are activated preferentially in tumors has the potential to improve the targeting of drug delivery. [Cancer Res 2008;68(12):4827–32]
Role of Acetylation and Extracellular Location of Heat Shock Protein 90α in Tumor Cell Invasion
Authors: Yang Yonghua , Rao Rehka , Shen Jie , Tang Yun , Fiskus Warren , Nechtman John , Atadja Peter , Bhalla Kapil 
Published: June 2008

Abstract
Heat shock protein (hsp) 90 is an ATP-dependent molecular chaperone that maintains the active conformation of client oncoproteins in cancer cells. An isoform, hsp90α, promotes extracellular maturation of matrix metalloproteinase (MMP)-2, involved in tumor invasion and metastasis. Knockdown of histone deacetylase (HDAC) 6, which deacetylates lysine residues in hsp90, induces reversible hyperacetylation and attenuates ATP binding and chaperone function of hsp90. Here, using mass spectrometry, we identified seven lysine residues in hsp90α that are hyperacetylated after treatment of eukaryotic cells with a pan-HDAC inhibitor that also inhibits HDAC6. Depending on the specific lysine residue in the middle domain involved, although acetylation affects ATP, cochaperone, and client protein binding to hsp90α, acetylation of all seven lysines increased the binding of hsp90α to 17-allyl-amino-demethoxy geldanamycin. Notably, after treatment with the pan-HDAC inhibitor panobinostat (LBH589), the extracellular hsp90α was hyperacetylated and it bound to MMP-2, which was associated with increased in vitro tumor cell invasiveness. Treatment with antiacetylated hsp90α antibody inhibited in vitro invasion by tumor cells. Thus, reversible hyperacetylation modulates the intracellular and extracellular chaperone function of hsp90, and targeting extracellular hyperacetylated hsp90α may undermine tumor invasion and metastasis. [Cancer Res 2008;68(12):4833–42]