bluuebunny/crossref_metadata_2025 huggingface dataset:
Data from Fibroblast Growth Factor 2 Restrains Ras-Driven Proliferation of Malignant Cells by Triggering RhoA-Mediated Senescence
Authors: Costa Érico T. , Forti Fábio L. , Matos Tatiana G.F. , Dermargos Alexandre , Nakano Fábio , Salotti Jacqueline , Rocha Kátia M. , Asprino Paula F. , Yoshihara Celina K. , Koga Marianna M. , Armelin Hugo A.
Published: March 2024

Abstract
Fibroblast growth factor 2 (FGF2) is considered to be a bona fide oncogenic factor, although results from our group and others call this into question. Here, we report that exogenous recombinant FGF2 irreversibly inhibits proliferation by inducing senescence in Ras-dependent malignant mouse cells, but not in immortalized nontumorigenic cell lines. We report the following findings in K-Ras–dependent malignant Y1 adrenocortical cells and H-Ras V12–transformed BALB-3T3 fibroblasts: (a) FGF2 inhibits clonal growth and tumor onset in nude and immunocompetent BALB/c mice, (b) FGF2 irreversibly blocks the cell cycle, and (c) FGF2 induces the senescence-associated β-galactosidase with no accompanying signs of apoptosis or necrosis. The tyrosine kinase inhibitor PD173074 completely protected malignant cells from FGF2. In Y1 adrenal cells, reducing the constitutively high levels of K-Ras-GTP using the dominant-negative RasN17 mutant made cells resistant to FGF2 cytotoxicity. In addition, transfection of the dominant-negative RhoA-N19 into either Y1 or 3T3-B61 malignant cell lines yielded stable clonal transfectants that were unable to activate RhoA and were resistant to the FGF2 stress response. We conclude that in Ras-dependent malignant cells, FGF2 interacts with its cognate receptors to trigger a senescence-like process involving RhoA-GTP. Surprisingly, attempts to select FGF2-resistant cells from the Y1 and 3T3-B61 cell lines yielded only rare clones that (a) had lost the overexpressed ras oncogene, (b) were dependent on FGF2 for proliferation, and (c) were poorly tumorigenic. Thus, FGF2 exerted a strong negative selection that Ras-dependent malignant cells could rarely overcome. [Cancer Res 2008;68(15):6215–23]
Data from The Ret Receptor Tyrosine Kinase Pathway Functionally Interacts with the ERα Pathway in Breast Cancer
Authors: Boulay Anne , Breuleux Madlaina , Stephan Christine , Fux Caroline , Brisken Cathrin , Fiche Maryse , Wartmann Markus , Stumm Michael , Lane Heidi A. , Hynes Nancy E.
Published: March 2024

Abstract
A limited number of receptor tyrosine kinases (e.g., ErbB and fibroblast growth factor receptor families) have been genetically linked to breast cancer development. Here, we investigated the contribution of the Ret receptor tyrosine kinase to breast tumor biology. Ret was expressed in primary breast tumors and cell lines. In estrogen receptor (ER)α-positive MCF7 and T47D lines, the ligand (glial-derived neurotrophic factor) activated signaling pathways and increased anchorage-independent proliferation in a Ret-dependent manner, showing that Ret signaling is functional in breast tumor cells. Ret expression was induced by estrogens and Ret signaling enhanced estrogen-driven proliferation, highlighting the functional interaction of Ret and ER pathways. Furthermore, Ret was detected in primary cancers, and there were higher Ret levels in ERα-positive tumors. In summary, we showed that Ret is a novel proliferative pathway interacting with ER signaling in vitro. Expression of Ret in primary breast tumors suggests that Ret might be a novel therapeutic target in breast cancer. [Cancer Res 2008;68(10):3743–51]
Data from Improved Therapeutic Results by Pretargeted Radioimmunotherapy of Non–Hodgkin's Lymphoma with a New Recombinant, Trivalent, Anti-CD20, Bispecific Antibody
Authors: Sharkey Robert M. , Karacay Habibe , Litwin Samuel , Rossi Edmund A. , McBride William J. , Chang Chien-Hsing , Goldenberg David M.
Published: March 2024

Abstract
We examined whether a pretargeting method using a new recombinant anti-CD20 bispecific antibody (bsMAb) followed by 90Y-1,4,7,10-tetraazacyclododecane-N,N′,N′′,N′′′-tetraacetic acid (90Y-DOTA)-peptide could reduce hematologic toxicity yet improve therapeutic responses compared with conventional 90Y-anti-CD20 IgG and a chemically conjugated bsMAb. TF4, a humanized, tri-Fab bsMAb with two Fabs binding CD20 and one Fab binding histamine-succinyl-glycine (HSG), developed by the dock and lock (DNL) method, was tested in nude mice with Ramos B-cell lymphomas. Optimal pretargeting required a 29-h interval between TF4 and 90Y-DOTA-HSG, and 20-fold more moles of TF4. TF4 cleared more rapidly from the blood than anti-CD20 IgG, with early processing in the liver, spleen, and kidney. At 24 h, TF4 improved tumor uptake of 111In-HSG-peptide 2.6-fold [13% versus 5% injected dose per gram (ID/g)] and enhanced tumor to blood ratios >45-fold (770 versus 17), compared with an anti-CD20 Fab × anti-HSG Fab chemical conjugate, and by 1.6-fold (9.0% versus 5.6% ID/g) and 1,600-fold (522 versus 0.32), respectively, compared with radiolabeled anti-CD20 IgG. A severe (≥90%) and prolonged reduction of WBCs was observed at the maximum dose of 90Y-anti-CD20 IgG, whereas pretargeting resulted in a ≤60% transient drop. TF4 pretargeting resulted in highly significant improvement in survival, curing 33% to 90% of the animals, even at relatively low doses, whereas most tumors progressed quickly without cures with 90Y-anti-CD20 IgG. These results indicate an improved therapeutic index with pretargeted radioimmunotherapy (RAIT) using a DNL-constructed tri-Fab, bsMAb, compared with conventional therapy with directly radiolabeled antibody or with a chemically conjugated bsMAb. These encouraging results prompt testing these constructs for pretargeting RAIT in patients. [Cancer Res 2008;68(13):5282–90]
Data from BH3 Mimetic ABT-737 Potentiates TRAIL-Mediated Apoptotic Signaling by Unsequestering Bim and Bak in Human Pancreatic Cancer Cells
Authors: Huang Shengbing , Sinicrope Frank A.
Published: March 2024

Abstract
Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) has been shown to induce mitochondrial apoptotic signaling that can be negatively regulated by prosurvival Bcl-2 proteins. ABT-737 is a small-molecule BH3 mimetic that binds to and antagonizes Bcl-2/Bcl-xL but not Mcl-1. We show that ABT-737 can synergistically enhance TRAIL-mediated cytotoxicity in human pancreatic cancer cell lines. ABT-737 was shown to enhance TRAIL-induced apoptosis as shown by DNA fragmentation, activation of caspase-8 and Bid, and cleavage of caspase-3 and poly(ADP-ribose) polymerase. A Bax conformational change induced by TRAIL was enhanced by ABT-737. ABT-737 disrupted the interaction of Bak with Bcl-xL in both cell lines. Furthermore, ABT-737 untethered the proapoptotic BH3-only protein Bim from its sequestration by Bcl-xL or Bcl-2. Bim small hairpin RNA (shRNA) was shown to attenuate caspase-3 cleavage and to reduce the cytotoxic effects of TRAIL plus ABT-737 compared with shRNA control cells. Finally, Mcl-1 shRNA potentiated caspase-3 cleavage by ABT-737 and enhanced its cytotoxic effects. Taken together, ABT-737 augments TRAIL-induced cell killing by unsequestering Bim and Bak and enhancing a Bax conformational change induced by TRAIL. These findings suggest a novel strategy to enhance cross-talk between the extrinsic and intrinsic apoptotic pathways to improve therapeutic efficacy against pancreatic cancer. [Cancer Res 2008;68(8):2944–51]
Data from Synergistic Effect of Oncogenic RET and Loss of p18 on Medullary Thyroid Carcinoma Development
Authors: van Veelen Wendy , van Gasteren Carola J.R. , Acton Dennis S. , Franklin David S. , Berger Ruud , Lips Cornelis J.M. , Höppener Jo W.M.
Published: March 2024

Abstract
Activating mutations in the RET proto-oncogene are associated with both familial and sporadic medullary thyroid carcinoma (MTC) development; however, the genetic mechanisms underlying MTC tumorigenesis remain largely unknown. Recently, we have identified somatic inactivating mutations in the cell cycle inhibitor gene P18 in human MTC, which coincided with activating RET mutations, suggesting a role for loss of P18 in combination with oncogenic RET in the multistep process of MTC development. Therefore, we crossed transgenic mice expressing oncogenic RET (RET2B) with mice lacking p18 (and p27, another cell cycle inhibitor) and monitored MTC development. RET2B;p18+/− mice and RET2B;p18−/− mice developed MTC with a highly increased incidence compared with their corresponding single mutant littermates. In addition, expression of oncogenic RET causes an earlier age of onset and larger MTCs in p18−/−;p27+/− mice. In a subset of MTCs of RET2B;p18+/−(;p27+/−) mice, p18Ink4c expression was completely lost. This loss of p18Ink4c expression correlated with higher proliferation rates as well as with larger MTCs, indicating that loss of p18 in combination with oncogenic RET not only increases the risk for MTC development but also enhances MTC progression. Our data strongly indicate that oncogenic RET and loss of p18 cooperate in the multistep tumorigenesis of MTC. [Cancer Res 2008;68(5):1329–37]
Data from c-Jun NH2-Terminal Kinase 1 Is a Critical Regulator for the Development of Gastric Cancer in Mice
Authors: Shibata Wataru , Maeda Shin , Hikiba Yohko , Yanai Ayako , Sakamoto Kei , Nakagawa Hayato , Ogura Keiji , Karin Michael , Omata Masao
Published: March 2024

Abstract
c-Jun NH2-terminal kinase (JNK) links several cellular processes, including proliferation and survival, and is believed to be involved in carcinogenesis. However, the role of JNK in gastric tumorigenesis is unknown. Immunohistochemical analysis reveals that JNK is frequently activated in human gastric cancer tissue. We investigated whether JNK1, a major JNK isozyme, is involved in chemically induced gastric cancer development. Mice lacking JNK1 exhibited a marked decrease in gastric carcinogenesis induced by N-methyl-N-nitrosourea, relative to their wild-type counterparts. Impaired tumor development correlated with decreased tumor initiation, which is associated with the production of reactive oxygen species. We also found that lower levels of tumorigenesis were correlated with the decreased expression of cyclin D and CDK as well as decreased cell proliferation. Taken together, JNK seems to be involved in both tumor initiation and promotion and may be an attractive target for the prevention of gastric carcinogenesis. [Cancer Res 2008;68(13):5031–9]
Data from Ectopic Expression of P-Cadherin Correlates with Promoter Hypomethylation Early in Colorectal Carcinogenesis and Enhanced Intestinal Crypt Fission In vivo
Authors: Milicic Anita , Harrison Lea-Anne , Goodlad Robert A. , Hardy Robert G. , Nicholson Anna M. , Presz Michal , Sieber Oliver , Santander Sonia , Pringle James H. , Mandir Nikki , East Philip , Obszynska Jolanta , Sanders Scott , Piazuelo Elena , Shaw Jacqui , Harrison Rebecca , Tomlinson Ian P. , McDonald Stuart A.C. , Wright Nicholas A. , Jankowski Janusz A.Z.
Published: March 2024

Abstract
P-cadherin is normally expressed in the basal layer of squamous epithelia and absent from the healthy intestine and colon. We have previously shown it to be expressed in all inflamed, hyperplastic, and dysplastic intestinal and colonic mucosa. This study aimed to better understand the mechanisms controlling the expression of P-cadherin and the biological effects of its ectopic presence in the intestine and colon. We investigated the CpG methylation status of the P-cadherin (CDH3) promoter and P-cadherin mRNA and protein expression in cases of familial and sporadic colorectal cancer (CRC). The CDH3 promoter was hypomethylated in colonic aberrant crypt foci, in CRC, and, occasionally, in the normal epithelium adjacent to cancer, demonstrating a potential “field effect” of cancerization. The hypomethylation was also associated with induction of P-cadherin expression in the neoplastic colon (P < 0.0001). We then created transgenic mice that overexpressed P-cadherin specifically in the intestinal and colonic epithelium under the liver fatty acid binding protein promoter. Forced ectopic expression of P-cadherin accompanied by indomethacin-induced inflammation resulted in a 3-fold higher crypt fission rate within the small and large intestines in the homozygous mice compared with the wild-type animals (P < 0.02). We conclude that epigenetic demethylation of the P-cadherin promoter in the human intestine permits its ectopic expression very early in the colorectal adenoma-carcinoma sequence and persists during invasive cancer. Induced P-cadherin expression, especially in mucosal damage, leads to an increased rate of crypt fission, a common feature of clonal expansion in gastrointestinal dysplasia. [Cancer Res 2008;68(19):7760–8]
Data from Phosphatidylinositol 3-Kinase Inhibition Broadly Sensitizes Glioblastoma Cells to Death Receptor– and Drug-Induced Apoptosis
Authors: Opel Daniela , Westhoff Mike-Andrew , Bender Ariane , Braun Veit , Debatin Klaus-Michael , Fulda Simone
Published: March 2024

Abstract
The aberrant activity of the phosphatidylinositol 3-kinase (PI3K) pathway has been reported to correlate with adverse clinical outcome in human glioblastoma in vivo. However, the question of how this survival network can be successfully targeted to restore the sensitivity of glioblastoma to apoptosis induction has not yet been answered. Here, we report that inhibition of PI3K by LY294002 broadly sensitizes wild-type and mutant PTEN glioblastoma cells to both death receptor– and chemotherapy-induced apoptosis, whereas mammalian target of rapamycin (mTOR) inhibition is not sufficient to restore apoptosis sensitivity. LY294002 significantly enhances apoptosis triggered by tumor necrosis factor–related apoptosis-inducing ligand (TRAIL), agonistic anti-CD95 antibodies, or several anticancer drugs (i.e., doxorubicin, etoposide, and vincristine) in a highly synergistic manner. In addition, LY294002 cooperates with TRAIL or doxorubicin to suppress colony formation, thus also showing a strong effect on long-term survival. Similarly, genetic knockdown of PI3K subunits p110α and/or p110β by RNA interference (RNAi) primes glioblastoma cells for TRAIL- or doxorubicin-mediated apoptosis. In contrast to PI3K inhibition, pharmacologic or genetic blockade of mTOR by RAD001 (everolimus), rapamycin, or RNAi fails to enhance TRAIL- or doxorubicin-induced apoptosis. Analysis of apoptosis pathways reveals that PI3K inhibition acts in concert with TRAIL or doxorubicin to trigger mitochondrial membrane permeabilization, caspase activation, and caspase-dependent apoptosis, which are abolished by the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Most importantly, PI3K inhibition by LY294002 sensitizes primary cultured glioblastoma cells obtained from surgical specimens to TRAIL- or chemotherapy-induced cell death. By showing that PI3K inhibition broadly primes glioblastoma cells for apoptosis, our findings provide the rationale for using PI3K inhibitors in combination regimens to enhance TRAIL- or chemotherapy-induced apoptosis in glioblastoma. [Cancer Res 2008;68(15):6271–80]
Data from Signatures Associated with Rejection or Recurrence in HER-2/neu–Positive Mammary Tumors
Authors: Worschech Andrea , Kmieciak Maciej , Knutson Keith L. , Bear Harry D. , Szalay Aladar A. , Wang Ena , Marincola Francesco M. , Manjili Masoud H.
Published: March 2024

Abstract
We have previously shown T-cell–mediated rejection of the neu-overexpressing mammary carcinoma cells (MMC) in wild-type FVB mice. However, following rejection of primary tumors, a fraction of animals experienced a recurrence of a neu antigen-negative variant (ANV) of MMC (tumor evasion model) after a long latency period. In the present study, we determined that T cells derived from wild-type FVB mice can specifically recognize MMC by secreting IFN-γ and can induce apoptosis of MMC in vitro. Neu transgenic (FVBN202) mice develop spontaneous tumors and cannot reject it (tumor tolerance model). To dissect the mechanisms associated with rejection or tolerance of MMC tumors, we compared transcriptional patterns within the tumor microenvironment of MMC undergoing rejection with those that resisted it either because of tumor evasion/antigen loss recurrence (ANV tumors) or because of intrinsic tolerance mechanisms displayed by the transgenic mice. Gene profiling confirmed that immune rejection is primarily mediated through activation of IFN-stimulated genes and T-cell effector mechanisms. The tumor evasion model showed combined activation of Th1 and Th2 with a deviation toward Th2 and humoral immune responses that failed to achieve rejection likely because of lack of target antigen. Interestingly, the tumor tolerance model instead displayed immune suppression pathways through activation of regulatory mechanisms that included in particular the overexpression of interleukin-10 (IL-10), IL-10 receptor, and suppressor of cytokine signaling (SOCS)-1 and SOCS-3. These data provide a road map for the identification of novel biomarkers of immune responsiveness in clinical trials. [Cancer Res 2008;68(7):2436–46]
Data from In vivo Switching of Human Melanoma Cells between Proliferative and Invasive States
Authors: Hoek Keith S. , Eichhoff Ossia M. , Schlegel Natalie C. , Döbbeling Udo , Kobert Nikita , Schaerer Leo , Hemmi Silvio , Dummer Reinhard
Published: March 2024

Abstract
Metastatic melanoma represents a complex and heterogeneous disease for which there are no therapies to improve patient survival. Recent expression profiling of melanoma cell lines identified two transcription signatures, respectively, corresponding with proliferative and invasive cellular phenotypes. A model derived from these findings predicts that in vivo melanoma cells may switch between these states. Here, DNA microarray–characterized cell lines were subjected to in vitro characterization before s.c. injection into immunocompromised mice. Tumor growth rates were measured and postexcision samples were assessed by immunohistochemistry to identify invasive and proliferative signature cells. In vitro tests showed that proliferative signature melanoma cells are faster growing but less motile than invasive signature cells. In vivo proliferative signature cells initiated tumor growth in 14 ± 3 days postinjection. By comparison, invasive signature cells required a significantly longer (P < 0.001) period of 59 ± 11 days. Immunohistochemistry showed that regardless of the seed cell signature, tumors showed evidence for both proliferative and invasive cell types. Furthermore, proliferative signature cell types were detected most frequently in the peripheral margin of growing tumors. These data indicate that melanoma cells undergo transcriptional signature switching in vivo likely regulated by local microenvironmental conditions. Our findings challenge previous models of melanoma progression that evoke one-way changes in gene expression. We present a new model for melanoma progression that accounts for transcription signature plasticity and provides a more rational context for explaining observed melanoma biology. [Cancer Res 2008;68(3):650–6]
Data from Targeted Delivery of Gemcitabine to Pancreatic Adenocarcinoma Using Cetuximab as a Targeting Agent
Authors: Patra Chitta Ranjan , Bhattacharya Resham , Wang Enfeng , Katarya Aaron , Lau Julie S. , Dutta Shamit , Muders Michael , Wang Shanfeng , Buhrow Sarah A. , Safgren Stephanie L. , Yaszemski Michael J. , Reid Joel M. , Ames Matthew M. , Mukherjee Priyabrata , Mukhopadhyay Debabrata
Published: March 2024

Abstract
One of the key challenges in anticancer therapy is the toxicity and poor bioavailability of the anticancer drugs. Nanotechnology can play a pivotal role by delivering drugs in a targeted fashion to the malignant cells that will reduce the systemic toxicity of the anticancer drug. In this report, we show a stepwise development of a nanoparticle-based targeted delivery system for in vitro and in vivo therapeutic application in pancreatic cancer. In the first part of the study, we have shown the fabrication and characterization of the delivery system containing gold nanoparticle as a delivery vehicle, cetuximab as a targeting agent, and gemcitabine as an anticancer drug for in vitro application. Nanoconjugate was first characterized physico-chemically. In vitro targeting efficacy, tested against three pancreatic cancer cell lines (PANC-1, AsPC-1, and MIA Paca2) with variable epidermal growth factor receptor (EGFR) expression, showed that gold uptake correlated with EGFR expression. In the second part, we showed the in vivo therapeutic efficacy of the targeted delivery system. Administration of this targeted delivery system resulted in significant inhibition of pancreatic tumor cell proliferation in vitro and orthotopic pancreatic tumor growth in vivo. Tumor progression was monitored noninvasively by measuring bioluminescence of the implanted tumor cells. Pharmacokinetic experiments along with the quantitation of gold both in vitro and in vivo further confirmed that the inhibition of tumor growth was due to targeted delivery. This strategy could be used as a generalized approach for the treatment of a variety of cancers characterized by overexpression of EGFR. [Cancer Res 2008;68(6):1970–8]
Data from EWS-FLI-1 Expression Triggers a Ewing's Sarcoma Initiation Program in Primary Human Mesenchymal Stem Cells
Authors: Riggi Nicolò , Suvà Mario-Luca , Suvà Domizio , Cironi Luisa , Provero Paolo , Tercier Stéphane , Joseph Jean-Marc , Stehle Jean-Christophe , Baumer Karine , Kindler Vincent , Stamenkovic Ivan
Published: March 2024

Abstract
Ewing's sarcoma family tumors (ESFT) express the EWS-FLI-1 fusion gene generated by the chromosomal translocation t(11;22)(q24;q12). Expression of the EWS-FLI-1 fusion protein in a permissive cellular environment is believed to play a key role in ESFT pathogenesis. However, EWS-FLI-1 induces growth arrest or apoptosis in differentiated primary cells, and the identity of permissive primary human cells that can support its expression and function has until now remained elusive. Here we show that expression of EWS-FLI-1 in human mesenchymal stem cells (hMSC) is not only stably maintained without inhibiting proliferation but also induces a gene expression profile bearing striking similarity to that of ESFT, including genes that are among the highest ESFT discriminators. Expression of EWS-FLI-1 in hMSCs may recapitulate the initial steps of Ewing's sarcoma development, allowing identification of genes that play an important role early in its pathogenesis. Among relevant candidate transcripts induced by EWS-FLI-1 in hMSCs, we found the polycomb group gene EZH2, which we show to play a critical role in Ewing's sarcoma growth. These observations are consistent with our recent findings using mouse mesenchymal progenitor cells and provide compelling evidence that hMSCs are candidate cells of origin of ESFT. [Cancer Res 2008;68(7):2176–85]
Data from Regulatory T Cell–Resistant CD8+ T Cells Induced by Glucocorticoid-Induced Tumor Necrosis Factor Receptor Signaling
Authors: Nishikawa Hiroyoshi , Kato Takuma , Hirayama Michiko , Orito Yuki , Sato Eiichi , Harada Naozumi , Gnjatic Sacha , Old Lloyd J. , Shiku Hiroshi
Published: March 2024

Abstract
We previously found that a Salmonella typhimurium vector engineered to secrete soluble tumor antigen induces CD4+ T cells resistant to CD4+CD25+ regulatory T cells (Treg) and that glucocorticoid-induced tumor necrosis factor receptor family-related gene (GITR) signal is involved in the development of this resistance. In this study, we address the potential of incorporating GITR ligand (GITRL) as a way to augment the immunogenicity of cancer vaccines. BALB/c mice were immunized by gene gun with plasmids encoding the mutated extracellular signal-regulated kinase 2 (mERK) with or without plasmids encoding mouse GITRL. Coadministration with GITRL during primary and secondary immunization enhanced the induction of mERK-specific CD8+ T cells. Antibody depletion and minigene analysis suggested that GITRL directly activated CTL epitope-specific CD8+ T cells independently of CD4+ T cells. Immunization with plasmids encoding a CTL epitope and GITRL resulted in strong tumor inhibition in a CD8+ T cell–dependent manner. Furthermore, CTL epitope-specific CD8+ T cells induced by immunization with plasmids encoding CTL epitope coadministered with GITRL were refractory to suppression by CD4+CD25+ Tregs compared with CD8+ T cells induced without GITR signaling. We propose that coadministration of GITR signaling agents with tumor antigens constitutes a promising novel strategy for cancer vaccine development. [Cancer Res 2008;68(14):5948–54]
Data from MDM2 Regulates Dihydrofolate Reductase Activity through Monoubiquitination
Authors: Maguire Maria , Nield Paul C. , Devling Timothy , Jenkins Rosalind E. , Park B. Kevin , Polański Radosław , Vlatković Nikolina , Boyd Mark T.
Published: March 2024

Abstract
MDM2 is a ubiquitin ligase that is best known for its essential function in the negative regulation of p53. In addition, MDM2 expression is associated with tumor progression in a number of common cancers, and in some cases, this has been shown to be independent of p53 status. MDM2 has been shown to promote the degradation of a number of other proteins involved in the regulation of normal cell growth and proliferation, including MDM4 and RB1. Here, we describe the identification of a novel substrate for the MDM2 ubiquitin ligase: dihydrofolate reductase (DHFR). MDM2 binds directly to DHFR and catalyses its monoubiquitination and not its polyubiquitination. In addition, MDM2 expression reduces DHFR activity in a p53-independent manner, but has no effect upon the steady-state level of expression of DHFR. We show that changes in MDM2 expression alter folate metabolism in cells as evidenced by MDM2-dependent alteration in the sensitivity of cells to the antifolate drug methotrexate. Furthermore, we show that the ability of MDM2 to inhibit DHFR activity depends upon an intact MDM2 RING finger. Our studies provide for the first time a link between MDM2, an oncogene with a critical ubiquitin ligase activity and a vital one-carbon donor pathway involved in epigenetic regulation, and DNA metabolism, which has wide ranging implications for both cell biology and tumor development. [Cancer Res 2008;68(9):3232–41]
Data from 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: March 2024

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]
Data from Quantitative Spatiotemporal Analysis of Antibody Fragment Diffusion and Endocytic Consumption in Tumor Spheroids
Authors: Thurber Greg M. , Wittrup K. Dane
Published: March 2024

Abstract
Antibody-based cancer treatment depends upon distribution of the targeting macromolecule throughout tumor tissue, and spatial heterogeneity could significantly limit efficacy in many cases. Antibody distribution in tumor tissue is a function of drug dosage, antigen concentration, binding affinity, antigen internalization, drug extravasation from blood vessels, diffusion in the tumor extracellular matrix, and systemic clearance rates. We have isolated the effects of a subset of these variables by live-cell microscopic imaging of single-chain antibody fragments against carcinoembryonic antigen in LS174T tumor spheroids. The measured rates of scFv penetration and retention were compared with theoretical predictions based on simple scaling criteria. The theory predicts that antibody dose must be large enough to drive a sufficient diffusive flux of antibody to overcome cellular internalization, and exposure time must be long enough to allow penetration to the spheroid center. The experimental results in spheroids are quantitatively consistent with these predictions. Therefore, simple scaling criteria can be applied to accurately predict antibody and antibody fragment penetration distance in tumor tissue. [Cancer Res 2008;68(9):3334–41]
Data from 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: March 2024

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]
Data from Transient Inhibition of ATM Kinase Is Sufficient to Enhance Cellular Sensitivity to Ionizing Radiation
Authors: Rainey Michael D. , Charlton Maura E. , Stanton Robert V. , Kastan Michael B.
Published: March 2024

Abstract
In response to DNA damage, the ATM protein kinase activates signal transduction pathways essential for coordinating cell cycle progression with DNA repair. In the human disease ataxia-telangiectasia, mutation of the ATM gene results in multiple cellular defects, including enhanced sensitivity to ionizing radiation (IR). This phenotype highlights ATM as a potential target for novel inhibitors that could be used to enhance tumor cell sensitivity to radiotherapy. A targeted compound library was screened for potential inhibitors of the ATM kinase, and CP466722 was identified. The compound is nontoxic and does not inhibit phosphatidylinositol 3-kinase (PI3K) or PI3K-like protein kinase family members in cells. CP466722 inhibited cellular ATM-dependent phosphorylation events and disruption of ATM function resulted in characteristic cell cycle checkpoint defects. Inhibition of cellular ATM kinase activity was rapidly and completely reversed by removing CP466722. Interestingly, clonogenic survival assays showed that transient inhibition of ATM is sufficient to sensitize cells to IR and suggests that therapeutic radiosensitization may only require ATM inhibition for short periods of time. The ability of CP466722 to rapidly and reversibly regulate ATM activity provides a new tool to ask questions about ATM function that could not easily be addressed using genetic models or RNA interference technologies. [Cancer Res 2008;68(18):7466–74]
Data from Hypoxia-Inducible Factor 1α Mediates Anoikis Resistance via Suppression of α5 Integrin
Authors: Rohwer Nadine , Welzel Martina , Daskalow Katjana , Pfander David , Wiedenmann Bertram , Detjen Katharina , Cramer Thorsten
Published: March 2024

Abstract
The transcription factor hypoxia-inducible factor 1 (HIF-1) α is abundantly expressed in the majority of human carcinomas and their metastases. HIF-1α controls central metastasis-associated pathways such as glycolysis, angiogenesis, and invasion. Functional inhibition of HIF-1α leads to impaired metastasis formation in murine tumor models. However, the precise molecular mechanisms underlying the metastasis-promoting role of HIF-1α have not been fully characterized. The ability of transformed epithelial cells to initiate the metastatic cascade relies on their ability to escape anoikis, a default program of apoptosis induction following loss of integrin anchoring to the extracellular matrix. Therefore, we addressed the function of HIF-1α in anoikis resistance and anchorage-independent growth. Inhibition of HIF-1α via RNA interference resulted in up-regulation of α5 integrin on the cell surface of human gastric cancer cells, whereas other integrins remained unaffected. Integrin α5 induction occurred at the level of transcription and was dependent on elevated intracellular superoxide in HIF-1α-knockdown cells. HIF-1α–deficient cells displayed significantly increased anoikis susceptibility due to up-regulated α5 integrin. Finally, colony formation in soft agar was shown to be dependent on HIF-1α as HIF-1α–deficient cells displayed a 70% reduction in anchorage-independent proliferation. Results obtained by RNA interference could be entirely confirmed by application of the pharmacologic HIF-1α-inhibitor 2-methoxyestradiol. Hence, our data argue for a pivotal role for HIF-1α in anoikis control via suppression of α5 integrin. HIF-1α–inhibiting drugs might therefore offer an innovative strategy for antimetastatic cancer therapy. [Cancer Res 2008;68(24):10113–20]
Data from Small Interfering RNA Molecules Targeting Endothelin-Converting Enzyme-1 Inhibit Endothelin-1 Synthesis and the Invasive Phenotype of Ovarian Carcinoma Cells
Authors: Rayhman Oleg , Klipper Eyal , Muller Laurent , Davidson Ben , Reich Reuven , Meidan Rina
Published: March 2024

Abstract
Endothelin-1 (ET-1) has been implicated in the progression of various cancers, including ovarian carcinoma. We found that the ovarian carcinoma cell lines ES2 and OVCAR3 and tumors from different anatomic sites expressed ET-1 system members [ET receptor A and ET-converting enzyme-1 (ECE-1)]. However, only ECE-1 was significantly higher in the solid tumors compared with effusions. We therefore investigated the effect of RNA interference-induced knockdown of ECE-1, the key enzyme in ET-1 production, on these two ovarian carcinoma cell lines. Small interfering RNA (siRNA) targeting of ECE-1 markedly reduced ECE-1 mRNA and protein levels, which subsequently led to 80% to 90% inhibition of ET-1 peptide secretion by the cells. ECE-1 silencing also profoundly affected the behavior of tumor cells compared with cells treated with scrambled siRNA. Silenced cells exhibited (a) reduced ET-1–dependent p44/42 mitogen-activated protein kinase phosphorylation; (b) decreased invasiveness and matrix metalloproteinase-2 activity; (c) improved adhesion to basal lamina proteins, laminin-1, and collagen IV; and (d) increased E-cadherin, an epithelial adhesion molecule, and reduced N-cadherin expression, a mesenchymal marker. Altered cell adherence is one of the hallmarks of the transformed phenotype, often characterized by the loss of the epithelial features and the gain of a mesenchymal phenotype. ECE-1 ablation did not, however, alter viable ovarian carcinoma cell numbers. Addition of exogenous ET-1 reversed the effects cited above. Taken together, these data indicate that siRNA is an effective tool for manipulating ECE-1 expression, ET-1 biosynthesis, and invasiveness of ovarian carcinoma. ECE-1 silencing may therefore develop into a promising novel anticancer therapy. [Cancer Res 2008;68(22):9265–73]
Data from Up-regulation of Inflammatory Signalings by Areca Nut Extract and Role of Cyclooxygenase-2 −1195G>A Polymorphism Reveal Risk of Oral Cancer
Authors: Chiang Shang-Lun , Chen Ping-Ho , Lee Chien-Hung , Ko Albert Min-Shan , Lee Ka-Wo , Lin Ying-Chu , Ho Pei-Shan , Tu Hung-Pin , Wu Deng-Chyang , Shieh Tien-Yu , Ko Ying-Chin
Published: March 2024

Abstract
Because the mRNA expression of cyclooxygenase-2 (COX-2) is up-regulated by arecoline in human gingival fibroblasts, as shown in our previous study, we further investigated the mRNA expression level of COX-2 and its upstream effectors in three oral epithelial carcinoma cell lines (KB, SAS, and Ca9-22) by using areca nut extract (ANE) and saliva-reacted ANE (sANE). A case-control study of 377 oral squamous cell carcinoma (OSCC) patients and 442 controls was conducted to evaluate the gene-environment interaction between COX-2 promoter polymorphisms and substance use of alcohol, betel quid, and cigarettes (ABC) in risk of OSCC. The heterogeneous characteristics of the oral site and the COX-2 −1195G>A polymorphism in these cell lines showed diverse inflammatory response (KB≫Ca9-22>SAS) after 24-hour ANE/sANE treatments, and the COX-2 up-regulation might be mostly elicited from alternative nuclear factor-κB activation. In the case-control study, betel chewing [adjusted odds ratios (aOR), 42.2] posed a much higher risk of OSCC than alcohol drinking and cigarette smoking (aORs, 2.4 and 1.8, respectively), whereas the COX-2 −1195A/A homozygote presented a potential genetic risk (OR, 1.55). The strongest joint effect for OSCC was seen in betel chewers with −1195A/A homozygote (aOR, 79.44). In the non–betel chewing group, the −1195A/G and A/A genotypes together with the combined use of alcohol and cigarettes increased risk to 15.1-fold and 32.1-fold, respectively, compared with the G/G genotype without substance use. Taken together, these findings illustrate a valuable insight into the potential role of the COX-2 promoter region in contributing to the development of betel-related OSCC, including ANE/sANE–induced transcriptional effects and enhanced joint effects of COX-2 −1195A allele with substance use of ABC. [Cancer Res 2008;68(20):8489–98]
Data from 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: March 2024

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]
Data from HEXIM1 Regulates 17β-Estradiol/Estrogen Receptor-α–Mediated Expression of Cyclin D1 in Mammary Cells via Modulation of P-TEFb
Authors: Ogba Ndiya , Chaplin Laura J. , Doughman Yong Qiu , Fujinaga Koh , Montano Monica M.
Published: March 2024

Abstract
Estrogen receptor α (ERα) plays a key role in mammary gland development and is implicated in breast cancer through the transcriptional regulation of genes linked to proliferation and apoptosis. We previously reported that hexamethylene bisacetamide inducible protein 1 (HEXIM1) inhibits the activity of ligand-bound ERα and bridges a functional interaction between ERα and positive transcription elongation factor b (P-TEFb). To examine the consequences of a functional HEXIM1-ERα-P-TEFb interaction in vivo, we generated MMTV/HEXIM1 mice that exhibit mammary epithelial-specific and doxycycline-inducible expression of HEXIM1. Increased HEXIM1 expression in the mammary gland decreased estrogen-driven ductal morphogenesis and inhibited the expression of cyclin D1 and serine 2 phosphorylated RNA polymerase II (S2P RNAP II). In addition, increased HEXIM1 expression in MCF-7 cells led to a decrease in estrogen-induced cyclin D1 expression, whereas down-regulation of HEXIM1 expression led to an enhancement of estrogen-induced cyclin D1 expression. Studies on the mechanism of HEXIM1 regulation on estrogen action indicated a decrease in estrogen-stimulated recruitment of ERα, P-TEFb, and S2P RNAP II to promoter and coding regions of ERα-responsive genes pS2 and CCND1 with increased HEXIM1 expression in MCF-7 cells. Notably, increased HEXIM1 expression decreased only estrogen-induced P-TEFb activity. Whereas there have been previous reports on HEXIM1 inhibition of P-TEFb activity, our studies add a new dimension by showing that E2/ER is an important regulator of the HEXIM1/P-TEFb functional unit in breast cells. Together, these studies provide novel insight into the role of HEXIM1 and ERα in mammary epithelial cell function. [Cancer Res 2008;68(17):7015–24]
Data from Inhibition of Activated Fibroblast Growth Factor Receptor 2 in Endometrial Cancer Cells Induces Cell Death Despite PTEN Abrogation
Authors: Byron Sara A. , Gartside Michael G. , Wellens Candice L. , Mallon Mary A. , Keenan Jack B. , Powell Matthew A. , Goodfellow Paul J. , Pollock Pamela M.
Published: March 2024

Abstract
KRAS activation and PTEN inactivation are frequent events in endometrial tumorigenesis, occurring in 10% to 30% and 26% to 80% of endometrial cancers, respectively. Because we have recently shown activating mutations in fibroblast growth factor receptor 2 (FGFR2) in 16% of endometrioid endometrial cancers, we sought to determine the genetic context in which FGFR2 mutations occur. Analysis of 116 primary endometrioid endometrial cancers revealed that FGFR2 and KRAS mutations were mutually exclusive, whereas FGFR2 mutations were seen concomitantly with PTEN mutations. Here, we show that shRNA knockdown of FGFR2 or treatment with a pan-FGFR inhibitor, PD173074, resulted in cell cycle arrest and induction of cell death in endometrial cancer cells with activating mutations in FGFR2. This cell death in response to FGFR2 inhibition occurred within the context of loss-of-function mutations in PTEN and constitutive AKT phosphorylation, and was associated with a marked reduction in extracellular signal-regulated kinase 1/2 activation. Together, these data suggest that inhibition of FGFR2 may be a viable therapeutic option in endometrial tumors possessing activating mutations in FGFR2, despite the frequent abrogation of PTEN in this cancer type. [Cancer Res 2008;68(17):6902–7]
Data from The Warburg Effect in Leukemia-Stroma Cocultures Is Mediated by Mitochondrial Uncoupling Associated with Uncoupling Protein 2 Activation
Authors: Samudio Ismael , Fiegl Michael , McQueen Teresa , Clise-Dwyer Karen , Andreeff Michael
Published: March 2024

Abstract
In 1956, Otto Warburg proposed that the origin of cancer cells was closely linked to a permanent respiratory defect that bypassed the Pasteur effect (i.e., the inhibition of anaerobic fermentation by oxygen). Since then, permanent defects in oxygen consumption that could explain the dependence of cancer cells on aerobic glycolysis have not been identified. Here, we show that under normoxic conditions exposure of leukemia cells to bone marrow–derived mesenchymal stromal cells (MSC) promotes accumulation of lactate in the culture medium and reduces mitochondrial membrane potential (ΔΨM) in both cell types. Notably, the consumption of glucose was not altered in cocultures, suggesting that the accumulation of lactate was the result of reduced pyruvate metabolism. Interestingly, the decrease in ΔΨM was mediated by mitochondrial uncoupling in leukemia cells and was accompanied by increased expression of uncoupling protein 2 (UCP2). HL60 cells fail to increase UCP2 expression, are not uncoupled after coculture, and do not exhibit increased aerobic glycolysis, whereas small interfering RNA–mediated suppression of UCP2 in OCI-AML3 cells reversed mitochondrial uncoupling and aerobic glycolysis elicited by MSC. Taken together, these data suggest that microenvironment activation of highly conserved mammalian UCPs may facilitate the Warburg effect in the absence of permanent respiratory impairment. [Cancer Res 2008;68(13):5198–205]
Data from CTCFL/BORIS Is a Methylation-Independent DNA-Binding Protein That Preferentially Binds to the Paternal H19 Differentially Methylated Region
Authors: Nguyen Phuongmai , Cui Hengmi , Bisht Kheem S. , Sun Lunching , Patel Krish , Lee Richard S. , Kugoh Hiroyuki , Oshimura Mitsuo , Feinberg Andrew P. , Gius David
Published: March 2024

Abstract
The CTCF paralog BORIS (brother of the regulator of imprinted sites) is an insulator DNA-binding protein thought to play a role in chromatin organization and gene expression. Under normal physiologic conditions, BORIS is predominantly expressed during embryonic male germ cell development; however, it is also expressed in tumors and tumor cell lines and, as such, has been classified as a cancer-germline or cancer-testis gene. It has been suggested that BORIS may be a pro-proliferative factor, whereas CTCF favors antiproliferation. BORIS and CTCF share similar zinc finger DNA-binding domains and seem to bind to identical target sequences. Thus, one critical question is the mechanism governing the DNA-binding specificity of these two proteins when both are present in tumor cells. Chromatin immunoprecipitation (ChIP) in HCT116 cells and their hypermethylated variant showed that BORIS binds to methylated DNA sequences, whereas CTCF binds to unmethylated DNA. Electromobility shift assays, using both whole-cell extracts and in vitro translated CTCF and BORIS protein, and methylation-specific ChIP PCR showed that BORIS is a methylation-independent DNA-binding protein. Finally, experiments in murine hybrid cells containing either the maternal or paternal human chromosome 11 showed that BORIS preferentially binds to the methylated paternal H19 differentially methylated region, suggesting a mechanism in which the affinity of CTCF for the unmethylated maternal allele directs the DNA binding of BORIS toward the paternal allele. [Cancer Res 2008;68(14):5546–51]