bluuebunny/crossref_metadata_2025_split huggingface dataset:
Targeting XIAP Bypasses Bcl-2–Mediated Resistance to TRAIL and Cooperates with TRAIL to Suppress Pancreatic Cancer Growth In vitro and In vivo
Authors: Vogler Meike , Walczak Henning , Stadel Dominic , Haas Tobias L. , Genze Felicitas , Jovanovic Marjana , Gschwend Jürgen E. , Simmet Thomas , Debatin Klaus-Michael , Fulda Simone 
Published: October 2008

Abstract
Resistance to apoptosis is a hallmark of pancreatic cancer, a leading cause of cancer deaths. Therefore, novel strategies are required to target apoptosis resistance. Here, we report that the combination of X-linked inhibitor of apoptosis (XIAP) inhibition and tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) is an effective approach to trigger apoptosis despite Bcl-2 overexpression and to suppress pancreatic cancer growth in vitro and in vivo. Knockdown of XIAP by RNA interference cooperates with TRAIL to induce caspase activation, loss of mitochondrial membrane potential, cytochrome c release, and apoptosis in pancreatic carcinoma cells. Loss of mitochondrial membrane potential and cytochrome c release are extensively inhibited by a broad range or caspase-3 selective caspase inhibitor and by RNAi-mediated silencing of caspase-3, indicating that XIAP inhibition enhances TRAIL-induced mitochondrial damage in a caspase-3–dependent manner. XIAP inhibition combined with TRAIL even breaks Bcl-2–imposed resistance by converting type II cells that depend on the mitochondrial contribution to the death receptor pathway to type I cells in which TRAIL-induced activation of caspase-3 and caspase-9 and apoptosis proceeds irrespective of high Bcl-2 levels. Most importantly, XIAP inhibition potentiates TRAIL-induced antitumor activity in two preclinical models of pancreatic cancer in vivo. In the chicken chorioallantoic membrane model, XIAP inhibition significantly enhances TRAIL-mediated apoptosis and suppression of tumor growth. In a tumor regression model in xenograft-bearing mice, XIAP inhibition acts in concert with TRAIL to cause even regression of established pancreatic carcinoma. Thus, this combination of XIAP inhibition plus TRAIL is a promising strategy to overcome apoptosis resistance of pancreatic cancer that warrants further investigation. [Cancer Res 2008;68(19):7956–65]
MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells
Authors: Papagiannakopoulos Thales , Shapiro Alice , Kosik Kenneth S. 
Published: October 2008

Abstract
MicroRNA dysregulation is observed in different types of cancer. MiR-21 up-regulation has been reported for the majority of cancers profiled to date; however, knowledge is limited on the mechanism of action of miR-21, including identification of functionally important targets that contribute to its proproliferative and antiapoptotic actions. In this study, we show for the first time that miR-21 targets multiple important components of the p53, transforming growth factor-β (TGF-β), and mitochondrial apoptosis tumor-suppressive pathways. Down-regulation of miR-21 in glioblastoma cells leads to derepression of these pathways, causing repression of growth, increased apoptosis, and cell cycle arrest. These phenotypes are dependent on two of the miR-21 targets validated in this study, HNRPK and TAp63. These findings establish miR-21 as an important oncogene that targets a network of p53, TGF-β, and mitochondrial apoptosis tumor suppressor genes in glioblastoma cells. [Cancer Res 2008;68(19):8164–72]
Anterior Gradient 2 Is Expressed and Secreted during the Development of Pancreatic Cancer and Promotes Cancer Cell Survival
Authors: Ramachandran Vijaya , Arumugam Thiruvengadam , Wang Huamin , Logsdon Craig D. 
Published: October 2008

Abstract
Pancreatic cancer is a major oncological challenge due to its aggressive growth and metastasis. In the current study, we investigated the role of anterior gradient 2 (AGR2) in these processes. AGR2 mRNA, as assessed by quantitative real-time reverse transcription–PCR (Q-RT-PCR), was 14-fold higher in pancreatic cancer compared with normal and pancreatitis tissues. Immunohistochemistry revealed high expression of AGR2 in neoplastic cells with 98% (56 of 57) positivity on pancreatic cancer and minimal staining in normal and pancreatitis tissues. AGR2 was also expressed in early pancreatic intraepithelial neoplastic lesions. RT-PCR and Western blotting showed elevated AGR2 expression in seven of nine pancreatic cancer cell lines. AGR2, as detected in conditioned media from cancer cells, indicated that it was secreted. The influence of AGR2 on pancreatic cancer cells was evaluated by silencing with small interfering RNA and short hairpin RNA. Silencing of AGR2 significantly reduced cell proliferation (MTS assay) and invasion (Boyden chamber assay) and improved gemcitabine sensitivity (fluorescence-activated cell sorting analysis). Conditioned media from cells in which AGR2 was silenced had a reduced ability to stimulate proliferation of pancreatic cancer cells, suggesting that secreted AGR2 was active. In vivo, silencing of AGR2 in MPanc-96 cells led to a significant reduction of tumor growth and increased the effectiveness of gemcitabine treatments in orthotopic tumor models evaluated by noninvasive bioluminescence imaging. In summary, AGR2 is expressed and secreted during pancreatic cancer development and plays an important role in cancer cell growth and survival. These observations suggest that AGR2 may be a useful molecular target in pancreatic cancer. [Cancer Res 2008;68(19):7811–8]
Autophagy: A Novel Mechanism of Synergistic Cytotoxicity between Doxorubicin and Roscovitine in a Sarcoma Model
Authors: Lambert Laura A. , Qiao Na , Hunt Kelly K. , Lambert Donald H. , Mills Gordon B. , Meijer Laurent , Keyomarsi Khandan 
Published: October 2008

Abstract
Doxorubicin is a genotoxic chemotherapy agent used in treatment of a wide variety of cancers. Significant clinical side effects, including cardiac toxicity and myelosuppression, severely limit the therapeutic index of this commonly used agent and methods which improve doxorubicin efficacy could benefit many patients. Because doxorubicin cytotoxicity is cell cycle specific, the cell cycle is a rational target to enhance its efficacy. We examined the direct, cyclin-dependent kinase inhibitor roscovitine as a means of enhancing doxorubicin cytotoxicity. This study showed synergistic cytotoxicity between doxorubicin and roscovitine in three sarcoma cell lines: SW-982 (synovial sarcoma), U2OS-LC3-GFP (osteosarcoma), and SK-LMS-1 (uterine leiomyosarcoma), but not the fibroblast cell line WI38. The combined treatment of doxorubicin and roscovitine was associated with a prolonged G2-M cell cycle arrest in the three sarcoma cell lines. Using three different methods for detecting apoptosis, our results revealed that apoptotic cell death did not account for the synergistic cytotoxicity between doxorubicin and roscovitine. However, morphologic changes observed by light microscopy and increased cytoplasmic LC3-GFP puncta in U20S-LC3-GFP cells after the combined treatment suggested the induction of autophagy. Induction of autophagy was also shown in SW-982 and SK-LMS-1 cells treated with both doxorubicin and roscovitine by acridine orange staining. These results suggest a novel role of autophagy in the enhanced cytotoxicity by cell cycle inhibition after genotoxic injury in tumor cells. Further investigation of this enhanced cytotoxicity as a treatment strategy for sarcomas is warranted. [Cancer Res 2008;68(19):7966–74]
NVP-BEZ235, a Dual PI3K/mTOR Inhibitor, Prevents PI3K Signaling and Inhibits the Growth of Cancer Cells with Activating PI3K Mutations
Authors: Serra Violeta , Markman Ben , Scaltriti Maurizio , Eichhorn Pieter J.A. , Valero Vanesa , Guzman Marta , Botero Maria Luisa , Llonch Elisabeth , Atzori Francesco , Di Cosimo Serena , Maira Michel , Garcia-Echeverria Carlos , Parra Josep Lluis , Arribas Joaquin , Baselga José 
Published: October 2008

Abstract
Phosphatidylinositol-3-kinase (PI3K) pathway deregulation is a common event in human cancer, either through inactivation of the tumor suppressor phosphatase and tensin homologue deleted from chromosome 10 or activating mutations of p110-α. These hotspot mutations result in oncogenic activity of the enzyme and contribute to therapeutic resistance to the anti-HER2 antibody trastuzumab. The PI3K pathway is, therefore, an attractive target for cancer therapy. We have studied NVP-BEZ235, a dual inhibitor of the PI3K and the downstream mammalian target of rapamycin (mTOR). NVP-BEZ235 inhibited the activation of the downstream effectors Akt, S6 ribosomal protein, and 4EBP1 in breast cancer cells. The antiproliferative activity of NVP-BEZ235 was superior to the allosteric selective mTOR complex inhibitor everolimus in a panel of 21 cancer cell lines of different origin and mutation status. The described Akt activation due to mTOR inhibition was prevented by higher doses of NVP-BEZ235. NVP-BEZ235 reversed the hyperactivation of the PI3K/mTOR pathway caused by the oncogenic mutations of p110-α, E545K, and H1047R, and inhibited the proliferation of HER2-amplified BT474 cells exogenously expressing these mutations that render them resistant to trastuzumab. In trastuzumab-resistant BT474 H1047R breast cancer xenografts, NVP-BEZ235 inhibited PI3K signaling and had potent antitumor activity. In treated animals, there was complete inhibition of PI3K signaling in the skin at pharmacologically active doses, suggesting that skin may serve as surrogate tissue for pharmacodynamic studies. In summary, NVP-BEZ235 inhibits the PI3K/mTOR axis and results in antiproliferative and antitumoral activity in cancer cells with both wild-type and mutated p110-α. [Cancer Res 2008;68(19):8022–30]
RNAi-Mediated Silencing of Nuclear Factor Erythroid-2–Related Factor 2 Gene Expression in Non–Small Cell Lung Cancer Inhibits Tumor Growth and Increases Efficacy of Chemotherapy
Authors: Singh Anju , Boldin-Adamsky Swetlana , Thimmulappa Rajesh K. , Rath Srikanta K. , Ashush Hagit , Coulter Jonathan , Blackford Amanda , Goodman Steven N. , Bunz Fred , Watson Walter H. , Gabrielson Edward , Feinstein Elena , Biswal Shyam 
Published: October 2008

Abstract
Nuclear factor erythroid-2–related factor 2 (Nrf2) is a redox-sensitive transcription factor that regulates the expression of electrophile and xenobiotic detoxification enzymes and efflux proteins, which confer cytoprotection against oxidative stress and apoptosis in normal cells. Loss of function mutations in the Nrf2 inhibitor, Kelch-like ECH-associated protein (Keap1), results in constitutive activation of Nrf2 function in non–small cell lung cancer. In this study, we show that constitutive activation of Nrf2 in lung cancer cells promotes tumorigenicity and contributes to chemoresistance by up-regulation of glutathione, thioredoxin, and the drug efflux pathways involved in detoxification of electrophiles and broad spectrum of drugs. RNAi-mediated reduction of Nrf2 expression in lung cancer cells induces generation of reactive oxygen species, suppresses tumor growth, and results in increased sensitivity to chemotherapeutic drug–induced cell death in vitro and in vivo. Inhibiting Nrf2 expression using naked siRNA duplexes in combination with carboplatin significantly inhibits tumor growth in a subcutaneous model of lung cancer. Thus, targeting Nrf2 activity in lung cancers, particularly those with Keap1 mutations, could be a promising strategy to inhibit tumor growth and circumvent chemoresistance. [Cancer Res 2008;68(19):7975–84]
Alteration of the Mitochondrial Apoptotic Pathway Is Key to Acquired Paclitaxel Resistance and Can Be Reversed by ABT-737
Authors: Kutuk Ozgur , Letai Anthony 
Published: October 2008

AbstractPaclitaxel is a microtubule-targeting antineoplastic drug widely used in human cancers. Even when tumors are initially responsive, progression of disease despite continued taxane therapy is all too common in the treatment of many of the most common epithelial cancers, including breast cancer. However, the mechanisms underlying paclitaxel resistance in cancer cells are not completely understood. Our hypothesis is that changes in the intrinsic (or mitochondrial) cell death pathway controlled by the BCL-2 family are key to the development of acquired paclitaxel resistance. Here we show that paclitaxel activates the mitochondrial apoptosis pathway, which can be blocked by BCL-2 overexpression. Treatment with ABT-737, a small-molecule BCL-2 antagonist, restores sensitivity to paclitaxel in BCL-2–overexpressing cells. To investigate the importance of changes in the intrinsic apoptotic pathway in the absence of enforced BCL-2 expression, we generated two independent breast cancer cell lines with acquired resistance to apoptosis induced by paclitaxel. In these lines, acquired resistance to paclitaxel is mediated either by increased antiapoptotic BCL-2 proteins or decreased proapoptotic BCL-2 proteins. In both cases, ABT-737 can engage the mitochondrial apoptosis pathway to restore sensitivity to paclitaxel to cell lines with acquired paclitaxel resistance. In summary, these findings suggest that alterations in the intrinsic apoptotic pathway controlled by BCL-2 protein family members may be crucial to causing paclitaxel resistance. Furthermore, our results suggest that combining small-molecule BCL-2 antagonists with paclitaxel may offer benefit to patients with paclitaxel-resistant tumors, an oncologic problem of great prevalence. [Cancer Res 2008;68(19):7985–94]
Optimized Clostridium-Directed Enzyme Prodrug Therapy Improves the Antitumor Activity of the Novel DNA Cross-Linking Agent PR-104
Authors: Liu Shie-Chau , Ahn G-One , Kioi Mitomu , Dorie Mary-Jo , Patterson Adam V. , Brown J. Martin 
Published: October 2008

Abstract
We have previously shown that spores of the nonpathogenic clostridial strain C. sporogenes genetically engineered to express the E. coli–derived cytosine deaminase gene are effective in converting systemically injected nontoxic 5-fluorocytosine into the toxic anticancer drug 5-fluorouracil, thereby producing tumor-specific antitumor activity. To improve the expression of E. coli–derived genes with this system, we first replaced the original fdP promoter in the vector with one of two powerful endogenous clostridial promoters: that of the thiolase gene (thlP) and that for the clostridial transcription factor abrB310 (abrBP). These substitutions improved protein expression levels of the prodrug-activating genes by 2- to 3-fold in comparison with fdP-driven expression. However, despite these strong promoters, we found much higher expression of the nitroreductase (NTR) protein in the E. coli host compared with the clostridial host, which we hypothesized could be the result of different codon use between the two organisms. To test this, we constructed new expression vectors with an artificially synthesized NTR gene using optimized clostridial codons (sNTR). Results from both enzymatic assays and Western blots of cell extracts from clostridial transformants harboring plasmid constructs of thlP-sNTR and abrBP-sNTR showed that the expression and activity of the NTR gene product was increased by ∼20-fold compared with the original construct. In vivo studies with i.v. administered sNTR-expressing C. sporogenes spores in SiHa tumor–bearing mice showed significantly improved antitumor efficacy when combined with either 5-aziridinyl-2,4-dinitrobenzamide (CB1954) or the novel dinitrobenzamide mustard prodrug, PR-104. [Cancer Res 2008;68(19):7995–8003]
Dual Roles for Coactivator Activator and its Counterbalancing Isoform Coactivator Modulator in Human Kidney Cell Tumorigenesis
Authors: Kang Yun Kyoung , Schiff Rachel , Ko Lan , Wang Tao , Tsai Sophia Y. , Tsai Ming-Jer , O'Malley Bert W. 
Published: October 2008

Abstract
Coactivator activator (CoAA) has been reported to be a coactivator that regulates steroid receptor–mediated transcription and alternative RNA splicing. Herein, we show that CoAA is a dual-function coregulator that inhibits G1-S transition in human kidney cells and suppresses anchorage-independent growth and xenograft tumor formation. Suppression occurs in part by down-regulating c-myc and its downstream effectors ccnd1 and skp2 and causing accumulation of p27/Kip1 protein. In this cellular setting, CoAA directly represses the proto-oncogene c-myc by recruiting HDAC3 protein and decreasing both the acetylation of histone H3 and the presence of RNA polymerase II on the c-myc promoter. Interestingly, a splicing isoform of CoAA, coactivator modulator (CoAM), antagonizes CoAA-induced G1-S transition and growth inhibition by negatively regulating the mRNA levels of the endogenous CoAA isoform. In addition, we found that expression of CoAA protein is significantly decreased in human renal cell carcinoma compared with normal kidney. Our study presents evidence that CoAA is a potential tumor suppressor in renal carcinoma and that CoAM is a counterbalancing splice isoform. This is, thus far, the only example of a nuclear receptor coregulator involved in suppression of kidney cancer and suggests potentially significant new roles for coregulators in renal cancer biology. [Cancer Res 2008;68(19):7887–96]
Hepatocyte Growth Factor and Sonic Hedgehog Expression in Cerebellar Neural Progenitor Cells Costimulate Medulloblastoma Initiation and Growth
Authors: Binning Mandy J. , Niazi Toba , Pedone Carolyn A. , Lal Bachchu , Eberhart Charles G. , Kim K. Jin , Laterra John , Fults Daniel W. 
Published: October 2008

Abstract
Medulloblastomas are malignant brain tumors that arise by transformation of neural progenitor cells in the cerebellum in children. Treatment-related neurotoxicity has created a critical need to identify signaling molecules that can be targeted therapeutically to maximize tumor growth suppression and minimize collateral neurologic injury. In genetically engineered mice, activation of Sonic Hedgehog (Shh) signaling in neural stem cells in the developing cerebellum induces medulloblastomas. Hepatocyte growth factor (HGF) and its cell surface receptor c-Met are highly expressed in human medulloblastomas, and elevated levels of c-Met and HGF mRNA predict an unfavorable prognosis for patients. HGF is neuroprotective for cerebellar granule cells and promotes growth of human medulloblastoma cells in culture and in murine xenografts. We modeled the ability of HGF to induce medulloblastomas in mice using a version of the RCAS/tv-a system that allows gene transfer to cerebellar neural progenitors during their postnatal expansion phase when these cells are highly susceptible to transformation. Here, we report a high frequency of medulloblastoma formation in mice after postnatal expression of HGF in cooperation with Shh. Some tumors showed neurocytic differentiation similar to that in human nodular medulloblastomas with activated Shh signaling. Systemic administration of a monoclonal antibody against HGF prolonged survival of mice bearing Shh + HGF–induced medulloblastomas by stimulating apoptosis. These findings indicate a role for HGF in medulloblastoma initiation and growth and show efficacy of HGF-targeted therapy in a mouse model of endogenously arising tumors. [Cancer Res 2008;68(19):7838–45]
A Double-Negative Feedback Loop between ZEB1-SIP1 and the microRNA-200 Family Regulates Epithelial-Mesenchymal Transition
Authors: Bracken Cameron P. , Gregory Philip A. , Kolesnikoff Natasha , Bert Andrew G. , Wang Jun , Shannon M. Frances , Goodall Gregory J. 
Published: October 2008

Abstract
Epithelial to mesenchymal transition occurs during embryologic development to allow tissue remodeling and is proposed to be a key step in the metastasis of epithelial-derived tumors. The miR-200 family of microRNAs plays a major role in specifying the epithelial phenotype by preventing expression of the transcription repressors, ZEB1/δEF1 and SIP1/ZEB2. We show here that miR-200a, miR-200b, and the related miR-429 are all encoded on a 7.5-kb polycistronic primary miRNA (pri-miR) transcript. We show that the promoter for the pri-miR is located within a 300-bp segment located 4 kb upstream of miR-200b. This promoter region is sufficient to confer expression in epithelial cells and is repressed in mesenchymal cells by ZEB1 and SIP1 through their binding to a conserved pair of ZEB-type E-box elements located proximal to the transcription start site. These findings establish a double-negative feedback loop controlling ZEB1-SIP1 and miR-200 family expression that regulates cellular phenotype and has direct relevance to the role of these factors in tumor progression. [Cancer Res 2008;68(19):7846–54]
The Mammary Progenitor Marker CD61/β3 Integrin Identifies Cancer Stem Cells in Mouse Models of Mammary Tumorigenesis
Authors: Vaillant François , Asselin-Labat Marie-Liesse , Shackleton Mark , Forrest Natasha C. , Lindeman Geoffrey J. , Visvader Jane E. 
Published: October 2008

Abstract
The cells of origin and mechanisms that underpin tumor heterogeneity in breast cancer are poorly understood. Here, we have examined three mouse models of mammary tumorigenesis (MMTV-wnt-1, MMTV-neu, and p53+/−) for changes in their epithelial cell hierarchy during the preneoplastic and neoplastic stages of tumor progression. In preneoplastic tissue, only MMTV-wnt-1 mice showed a perturbation in their epithelial subpopulations. In addition to an expanded mammary stem cell pool, repopulating cells capable of yielding extensive mammary outgrowths in vivo were revealed in the committed luminal progenitor population. These findings indicate that wnt-1 activation induces the appearance of aberrant progenitor cells, and suggest that both mammary stem and progenitor cells can serve as the cellular targets of wnt-1–induced tumorigenesis. In tumors arising in MMTV-wnt-1 tumors, the luminal epithelial progenitor marker CD61/β3 integrin identified a cancer stem cell (CSC) population that was highly enriched for tumorigenic capability relative to the CD61− subset. CD61 expression also defined a CSC subset in 50% of p53+/−–derived tumors. No CSCs, however, could be identified in the more homogeneous MMTV-neu/erbB2 model, suggesting an alternative model of tumorigenesis. Overall, our findings show the utility of the progenitor marker CD61 in the identification of CSCs that sustain specific mammary tumors. [Cancer Res 2008;68(19):7711–7]
The Melanoma-Associated Antigen A3 Mediates Fibronectin-Controlled Cancer Progression and Metastasis
Authors: Liu Wei , Cheng Sonia , Asa Sylvia L. , Ezzat Shereen 
Published: October 2008

Abstract
Tumor cells frequently exhibit decreased adhesiveness due to failure to deposit stromal fibronectin (FN), permitting more rapid proliferation, migration, invasion, and metastasis. Although up-regulation of FN has been noted in gene profiles of carcinomas compared with normal tissue, reduced FN expression has been described at the peripheral margins of invading tumors. In this study, we investigate the role of FN in cancer behavior. Using human thyroid carcinoma cells with stably down-regulated FN, we performed gene profiling and created an orthotopic mouse model. We stably overexpressed the FN target, MAGE A3, which has also been identified as a target of the breast cancer risk factor fibroblast growth factor receptor 2, and examined the functional effects in vitro and in vivo in a flank model and an orthotopic model of thyroid cancer. Mouse xenografts showed significantly enhanced tumor growth as well as larger and more numerous lung metastases in response to FN silencing. Gene profiling identified the melanoma-associated antigen (MAGE A3) as significantly up-regulated in response to FN silencing. Forced expression of MAGE A3 resulted in p21 down-regulation, accelerated cell cycle progression, increased cell migration rate, and invasion in vitro and in vivo in an orthotopic mouse model where microcomputed tomography confirmed lung metastases that recapitulate the progression of human thyroid cancer. We conclude that MAGE A3 is a functional integrator of diverse signals, including FGFR2 and FN, to modulate cancer progression. [Cancer Res 2008;68(19):8104–12]