bluuebunny/crossref_metadata_2025_split huggingface dataset:
AKT Regulation of Estrogen Receptor β Transcriptional Activity in Breast Cancer
Authors: Duong Bich N. , Elliott Steven , Frigo Daniel E. , Melnik Lilia I. , Vanhoy Lyndsay , Tomchuck Suzanne , Lebeau Helena P. , David Odile , Beckman Barbara S. , Alam Jawed , Bratton Melyssa R. , McLachlan John A. , Burow Matthew E. 
Published: September 2006

Abstract
Growth factor activation of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway has been shown to activate the estrogen receptor (ER) α and to mediate tamoxifen resistance in breast cancer. Here, we investigated the regulation of the transcriptional activity of the newer ERβ by PI3K-AKT signaling. Tissue arrays of breast cancer specimens showed a positive association between the expressions of AKT and ERβ in the clinical setting. Reporter gene assays using pharmacologic and molecular inhibitors of AKT and constitutively active AKT revealed for the first time the ability of AKT to (a) potentiate ERβ activity and (b) target predominantly the activation function-2 (AF2) domain of the receptor, with a requirement for residue K269. Given the importance of coactivators in ER transcriptional activity, we further investigated the possible involvement of steroid receptor coactivator 1 (SRC1) and glucocorticoid receptor-interacting protein 1 (GRIP1) in AKT regulation of ERβ. Mammalian two-hybrid assays revealed that AKT enhanced both SRC1 and GRIP1 recruitment to the ERβ-AF2 domain, and reporter gene analyses revealed that AKT and GRIP1 cooperatively potentiated ERβ-mediated transcription to a level much greater than either factor alone. Investigations into AKT regulation of GRIP with mammalian one-hybrid assays showed that AKT potentiated the activation domains of GRIP1 itself, and in vitro kinase assays revealed that AKT directly phosphorylated GRIP1. The cross-talk between the PI3K-AKT and ERβ pathways, as revealed by the ability of AKT to regulate several components of ERβ-mediated transcription, may represent an important aspect that may influence breast cancer response to endocrine therapy. (Cancer Res 2006; 66(17): 8373-81)
Analysis of Genetic Alterations and Clonal Proliferation in Children Treated for Acute Lymphocytic Leukemia
Authors: Kendall Heather E. , Vacek Pamela M. , Rivers Jami L. , Rice Sederick C. , Messier Terri L. , Finette Barry A. 
Published: September 2006

Abstract
The development of risk-directed treatment protocols over the last 25 years has resulted in an increase in the survival rates of children treated for cancer. As a consequence, there is a growing population of pediatric cancer survivors in which the long-term genotoxic effects of chemotherapy is unknown. We previously reported that children treated for acute lymphocytic leukemia have significantly elevated somatic mutant frequencies at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene in their peripheral T cells. To understand the molecular etiology of the increase in mutant frequencies following chemotherapy, we investigated the HPRT mutation spectra and the extent of clonal proliferation in 562 HPRT T cell mutant isolates of 87 blood samples from 47 subjects at diagnosis, during chemotherapy, and postchemotherapy. We observed a significant increase in the proportion of CpG transitions following treatment (13.6-23.3%) compared with healthy controls (4.0%) and a significant decrease in V(D)J-mediated deletions following treatment (0-6.8%) compared with healthy controls (17.0%). There was also a significant change in the class type percentage of V(D)J-mediated HPRT deletions following treatment. In addition, there was a &gt;5-fold increase in T cell receptor gene usage–defined mean clonal proliferation from diagnosis compared with the completion of chemotherapeutic intervention. These data indicate that unique genetic alterations and extensive clonal proliferation are occurring in children following treatment for acute lymphocytic leukemia that may influence long-term risks for multifactorial diseases, including secondary cancers. (Cancer Res 2006; 66(17): 8455-61)
Breast Cancer Growth Prevention by Statins
Authors: Campbell Michael J. , Esserman Laura J. , Zhou Yamei , Shoemaker Mark , Lobo Margaret , Borman Elizabeth , Baehner Frederick , Kumar Anjali S. , Adduci Kelly , Marx Corina , Petricoin Emanuel F. , Liotta Lance A. , Winters Mary , Benz Stephen , Benz Christopher C. 
Published: September 2006

Abstract
Statins are cholesterol-lowering drugs with pleiotropic activities including inhibition of isoprenylation reactions and reduction of signals driving cell proliferation and survival responses. The objectives of this study were to examine the effects of statins on breast cancer cells, both in vitro and in vivo, and to begin to determine their mechanism of action. We evaluated the effects of statins on breast cancer cell growth, phosphoprotein signaling intermediates, survival/apoptosis regulators, cell cycle regulators, and activated transcription factors. We also examined the in vivo effect of statin administration in a mouse ErbB2+ breast cancer model. Only lipophilic statins had direct anticancer activity in vitro. Breast cancer cells with activated Ras or ErbB2 pathways seemed to be more sensitive than those overexpressing estrogen receptor, and this correlated with endogenous levels of activated nuclear factor κB (NF-κB). Key intermediates regulating cell survival by NF-κB activation, as well as cell proliferation by the mitogen activated protein kinase cascade, were among the earliest phosphoproteins influenced by statin treatment. These early effects were followed by declines in activator protein-1 and NF-κB activation and concordant changes in other mediators of proliferation and apoptosis. In vivo results showed that oral dosing of statins significantly inhibited the growth of a mouse mammary carcinoma. Lipophilic statins can exert direct anticancer activity in vitro by reducing proliferation and survival signals in susceptible breast cancer phenotypes. Tumor growth inhibition in vivo using a clinically relevant statin dose also seems to be associated with reduced tumor cell proliferation and survival. These findings provide supporting rationale for future statin trials in breast cancer patients. (Cancer Res 2006; 66(17): 8707-13)
Ephrin-B3 Ligand Promotes Glioma Invasion through Activation of Rac1
Authors: Nakada Mitsutoshi , Drake Kelsey L. , Nakada Satoko , Niska Jared A. , Berens Michael E. 
Published: September 2006

Abstract
Eph receptor tyrosine kinases are involved in nervous system development. Eph ligands, termed ephrins, are transmembrane proteins that bind to Eph receptors, the mutual activation of which causes repulsive effects in reciprocally contacting cells. Previously, we showed that overexpression of EphB2 in glioma cells increases cell invasion. Here, expression profiles of ephrin-B family members were determined in four glioma cell lines and in invading glioblastoma cells collected by laser capture microdissection. Ephrin-B3 mRNA was up-regulated in migrating cells of four of four glioma cell lines (1.3- to 1.7-fold) and in invading tumor cells of eight of eight biopsy specimens (1.2- to 10.0-fold). Forced expression of ephrin-B3 in low expressor cell lines (U87, T98G) stimulated cell migration and invasion in vitro and ex vivo, concomitant with tyrosine phosphorylation of ephrin-B3. In high expressor cell lines (U251, SNB19), ephrin-B3 colocalized with Rac1 to lamellipodia of motile wild-type cells. Cells transfected with ephrin-B3 small interfering RNA (siRNA) showed significant morphologic change and decreased invasion in vitro and ex vivo. Depletion of endogenous ephrin-B3 expression abrogated the increase of migration and invasion induced by EphB2/Fc, indicating increased invasion is dependent on ephrin-B3 activation. Furthermore, using a Rac1-GTP pull-down assay, we showed that ephrin-B3 is associated with Rac1 activation. Reduction of Rac1 by siRNA negated the increased invasion by addition of EphB2/Fc. In human glioma specimens, ephrin-B3 expression and phosphorylation correlated with increasing tumor grade. Immunohistochemistry revealed robust staining for phosphorylated ephrin-B and ephrin-B3 in invading glioblastoma cells. These data show that ephrin-B3 expression and signaling through Rac1 are critically important to glioma invasion. (Cancer Res 2006; 66(17): 8492-500)
The Role of the Vascular Endothelial Growth Factor–Delta-like 4 Ligand/Notch4-Ephrin B2 Cascade in Tumor Vessel Remodeling and Endothelial Cell Functions
Authors: Hainaud Patricia , Contrerès Jean-Olivier , Villemain Aude , Liu Lang-Xia , Plouët Jean , Tobelem Gérard , Dupuy Evelyne 
Published: September 2006

Abstract
Vascular endothelial growth factor (VEGF) and Delta-like 4 ligand (DLL4) are the only genes whose haploinsufficiency results in vascular abnormalities. Although many common pathways are up-regulated in both vascular development and tumor angiogenesis and in vascular remodeling, the role of the Delta/Notch pathway has not been clearly defined in tumor angiogenesis. In this study, we assessed the expression of DLL4, Notch4, and ephrin B2 in transgenic mice developing hepatocarcinoma characterized by a strong remodeling of the tumor sinusoids. We also investigated the role of VEGF in the expression and biological functions of these molecules on human venous endothelial cells. In transgenic livers, we showed that DLL4, active Notch4, and ephrin B2 were gradually up-regulated within the hepatocarcinoma progression and expressed on tumor sinusoidal endothelial cells. In venous endothelial cells, we showed that VEGF up-regulates DLL4 and presenilin, and increased the activation of Notch4, leading to an up-regulation of ephrin B2 with a down-regulation of Eph B4. We also showed that the activation of Notch4 is required for VEGF-induced up-regulation of ephrin B2 and the differentiation of human venous endothelial cells in vitro. Accordingly, the disruption of Notch4 signaling by pharmacologic inhibition of presenilin or addition of soluble DLL4 inhibited the effect of VEGF on human venous endothelial cell migration and differentiation. Our study strongly suggests that a coordinated activation of DDL4/Notch4 and ephrin B2 pathways downstream of VEGF plays a key role in the abnormal remodeling of tumor vessels. (Cancer Res 2006; 66(17): 8501-10)
Calreticulin, a Molecular Chaperone in the Endoplasmic Reticulum, Modulates Radiosensitivity of Human Glioblastoma U251MG Cells
Authors: Okunaga Tomohiro , Urata Yoshishige , Goto Shinji , Matsuo Takayuki , Mizota Shingo , Tsutsumi Keisuke , Nagata Izumi , Kondo Takahito , Ihara Yoshito 
Published: September 2006

Abstract
Radiotherapy is the primary and most important adjuvant therapy for malignant gliomas. Although the mechanism of radiation resistance in gliomas has been studied for decades, it is still not clear how the resistance is related with functions of molecular chaperones in the endoplasmic reticulum. Calreticulin (CRT) is a Ca2+-binding molecular chaperone in the endoplasmic reticulum. Recently, it was reported that changes in intracellular Ca2+ homeostasis play a role in the modulation of apoptosis. In the present study, we found that the level of CRT was higher in neuroglioma H4 cells than in glioblastoma cells (U251MG and T98G), and was well correlated with the sensitivity to γ-irradiation. To examine the role of CRT in the radiosensitivity of malignant gliomas, the CRT gene was introduced into U251MG cells, which express low levels of CRT, and the effect of overexpression of CRT on the radiosensitivity was examined. The cells transfected with the CRT gene exhibited enhanced radiation-induced apoptosis compared with untransfected control cells. In CRT-overexpressing cells, cell survival signaling via Akt was markedly suppressed. Furthermore, the gene expression of protein phosphatase 2Acα (PP2Acα), which is responsible for the dephosphorylation and inactivation of Akt, was up-regulated in CRT-overexpressing cells, and the regulation was dependent on Ca2+. Thus, overexpression of CRT modulates radiation-induced apoptosis by suppressing Akt signaling through the up-regulation of PP2Acα expression via altered Ca2+ homeostasis. These results show the novel mechanism by which CRT is involved in the regulation of radiosensitivity and radiation-induced apoptosis in malignant glioma cells. (Cancer Res 2006; 66(17): 8662-71)
Ionizing Radiation Enhances Matrix Metalloproteinase-2 Secretion and Invasion of Glioma Cells through Src/Epidermal Growth Factor Receptor–Mediated p38/Akt and Phosphatidylinositol 3-Kinase/Akt Signaling Pathways
Authors: Park Chang-Min , Park Myung-Jin , Kwak Hee-Jin , Lee Hyung-Chahn , Kim Mi-Suk , Lee Seung-Hoon , Park In-Chul , Rhee Chang Hun , Hong Seok-Il 
Published: September 2006

Abstract
Glioblastoma is a severe type of primary brain tumor, and its highly invasive character is considered to be a major therapeutic obstacle. Several recent studies have reported that ionizing radiation (IR) enhances the invasion of tumor cells, but the mechanisms for this effect are not well understood. In this study, we investigated the possible signaling mechanisms involved in IR-induced invasion of glioma cells. IR increased the matrix metalloproteinase (MMP)-2 promoter activity, mRNA transcription, and protein secretion along with the invasiveness of glioma cells lacking functional PTEN (U87, U251, U373, and C6) but not those harboring wild-type (WT)-PTEN (LN18 and LN428). IR activated phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin, and blockade of these kinases by specific inhibitors (LY294002, Akt inhibitor IV, and rapamycin, respectively) and transfection of dominant-negative (DN) mutants (DN-p85 and DN-Akt) or WT-PTEN suppressed the IR-induced MMP-2 secretion in U251 and U373 cells. In addition, inhibitors of epidermal growth factor receptor (EGFR; AG490 and AG1478), Src (PP2), and p38 (SB203580), EGFR neutralizing antibody, and transfection of DN-Src and DN-p38 significantly blocked IR-induced Akt phosphorylation and MMP-2 secretion. IR-induced activation of EGFR was suppressed by PP2, whereas LY294002 and SB203580 did not affect the activations of p38 and PI3K, respectively. Finally, these kinase inhibitors significantly reduced the IR-induced invasiveness of these cells on Matrigel. Taken together, our findings suggest that IR induces Src-dependent EGFR activation, which triggers the p38/Akt and PI3K/Akt signaling pathways, leading to increased MMP-2 expression and heightened invasiveness of PTEN mutant glioma cells. (Cancer Res 2006; 66(17): 8511-9)
Inducible Resistance of Tumor Cells to Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand Receptor 2–Mediated Apoptosis by Generation of a Blockade at the Death Domain Function
Authors: Li Yang , Wang Hong , Wang Zheng , Makhija Sharmila , Buchsbaum Donald , LoBuglio Albert , Kimberly Robert , Zhou Tong 
Published: September 2006

AbstractInduction of tumor cell resistance to therapeutics has been a major obstacle in cancer therapy. Targeting of the death receptors by a natural ligand, tumor necrosis factor–related apoptosis-inducing ligand (TRAIL), or agonistic monoclonal antibodies against TRAIL receptor 1 (TRAIL-R1) or TRAIL receptor 2 (TRAIL-R2) has been thought to be a promising cancer therapy. To determine whether tumor cells are able to generate a resistance to apoptosis induced by an anti-TRAIL-R2 antibody, TRA-8, we examined the apoptotic response of human breast and ovarian cancer cell lines after treatment with TRA-8. Our results show that tumor cell resistance to TRA-8 can be induced by repeated treatment of tumor cells with low, non-apoptosis-inducing doses of TRA-8. Interestingly, the induced resistance to apoptosis was not due to a global apoptotic defect in tumor cells but rather a selective defect in the TRAIL-R2 signaling pathway. Whereas TRA-8-treated tumor cells developed a selective resistance to TRAIL-R2-mediated apoptosis, the apoptotic responses induced by TRAIL, an anti-TRAIL-R1 antibody (2E12), and other apoptotic stimuli were not impaired. The expression levels of cell surface TRAIL-R2 were not altered and mutations of TRAIL-R2 were not found in the resistant cells. The induced TRA-8 resistance was due to a selective blockade at the level of the death domain and could be reversed by a wide array of chemotherapeutic agents. Proteomic analysis of death-inducing signaling complex formation during TRA-8 treatment shows that the translocation of TRAIL-R2-associated apoptotic proteins was significantly altered. Our results suggest that the prevention of tumor cell resistance to therapeutic agents that target the death receptors must be taken into consideration. (Cancer Res 2006; 66(17): 8520-8)
Prognostic Significance of Nuclear Factor-κB p105/p50 in Human Melanoma and Its Role in Cell Migration
Authors: Gao Kai , Dai Derek L. , Martinka Magdalena , Li Gang 
Published: September 2006

Abstract
Transcriptional factor nuclear factor-κB (NF-κB) family has been shown to play an important role in tumor pathogenesis and serve as a potential target in cancer therapy. However, it is necessary to clarify the specific functions of NF-κB members, which would provide the basis for the selective blockade and reduction of therapeutic side effects resulting from unspecific inhibition of NF-κB members. In this study, we explored the role of NF-κB p105/p50 in melanoma pathogenesis in vitro and in vivo. We found that the expression of NF-κB p105/p50 significantly increased in dysplastic nevi, primary melanoma, and metastatic melanoma compared with normal nevi (P = 0.0004, χ2 test). Furthermore, NF-κB p105/p50 nuclear staining increased with melanoma progression and strong NF-κB p105/p50 nuclear staining was inversely correlated with disease-specific 5-year survival of patients with tumor thickness &gt;2.0 mm (P = 0.014, log-rank test). Multivariate Cox regression analysis revealed that nuclear expression of NF-κB p105/p50 is an independent prognostic factor in this subgroup. Moreover, we found that up-regulation of NF-κB p50 enhanced melanoma cell migration, whereas small interfering RNA knockdown inhibited cell migration. In addition, overexpression of NF-κB p50 induced RhoA activity and Rock-mediated formation of stress fiber in melanoma cells. Taken together, our data indicate that NF-κB p105/p50 may be an important marker for human melanoma progression and prognosis as well as a potentially selective therapeutic target. (Cancer Res 2006; 66(17): 8382-8)
Chk1- and Claspin-Dependent but ATR/ATM– and Rad17-Independent DNA Replication Checkpoint Response in HeLa Cells
Authors: Rodríguez-Bravo Verónica , Guaita-Esteruelas Sandra , Florensa Roger , Bachs Oriol , Agell Neus 
Published: September 2006

Abstract
When DNA synthesis is inhibited, DNA replication checkpoint is activated to prevent mitosis entry without fully replicated DNA. In Xenopus, caffeine-sensitive kinases [ataxia telangiectasia mutated (ATM) and ATM-related protein (ATR)] are essential in this checkpoint response, but in mammal cells an ATR/ATM–independent checkpoint response to DNA synthesis inhibition exists. Using HeLa cells, which have a caffeine-insensitive checkpoint response, we have analyzed here which molecules known to be involved in the DNA replication checkpoint participate in the caffeine-insensitive response. When DNA synthesis was inhibited in the presence of UCN01 or after knocking down Chk1 expression [Chk1 small interfering RNA (siRNA)], HeLa cells entered into aberrant mitosis. Consequently, Chk1 is essential for both the ATR/ATM–dependent and ATR/ATM–independent checkpoint response in HeLa cells. Neither wortmannin, Ly294002, nor SB202190 abrogated the caffeine-insensitive checkpoint response, indicating that DNA-PK and p38α,β are not involved in the ATR/ATM–independent Chk1 activation upon DNA synthesis inhibition. Using siRNA to knock down Rad17 and claspin, two molecules involved in sensing stalled replication forks, we also showed that claspin but not Rad17 is essential for the ATR/ATM–independent checkpoint response. Inhibition of DNA synthesis in HeLa cells led to a decrease in cyclin B1 protein accumulation that was abrogated when UCN01 was added or when claspin was knocked down. We conclude that upon DNA synthesis inhibition, Chk1 can be activated in a claspin-dependent manner independently of ATR and ATM, leading to cyclin B1 down-regulation and providing the cells of an additional mechanism to inhibit mitosis entry. (Cancer Res 2006; 66(17): 8672-9)
Class II Histone Deacetylases Are Associated with VHL-Independent Regulation of Hypoxia-Inducible Factor 1α
Authors: Qian David Z. , Kachhap Sushant K. , Collis Spencer J. , Verheul Henk M.W. , Carducci Michael A. , Atadja Peter , Pili Roberto 
Published: September 2006

Abstract
Hypoxia-inducible factor 1α (HIF-1α) plays a critical role in transcriptional gene activation involved in tumor angiogenesis. A novel class of agents, the histone deacetylase (HDAC) inhibitors, has been shown to inhibit tumor angiogenesis and HIF-1α protein expression. However, the molecular mechanism responsible for this inhibition remains to be elucidated. In the current study, we investigated the molecular link between HIF-1α inhibition and HDAC inhibition. Treatment of the VHL-deficient human renal cell carcinoma cell line UMRC2 with the hydroxamic HDAC inhibitor LAQ824 resulted in a dose-dependent inhibition of HIF-1α protein via a VHL-independent mechanism and reduction of HIF-1α transcriptional activity. HIF-1α inhibition by LAQ824 was associated with HIF-1α acetylation and polyubiquitination. HIF-1α immunoprecipitates contained HDAC activity. Then, we tested different classes of HDAC inhibitors with diverse inhibitory activity of class I versus class II HDACs and assessed their capability of targeting HIF-1α. Hydroxamic acid derivatives with known activity against both class I and class II HDACs were effective in inhibiting HIF-1α at low nanomolar concentrations. In contrast, valproic acid and trapoxin were able to inhibit HIF-1α only at concentrations that are effective against class II HDACs. Coimmunoprecipitation studies showed that class II HDAC4 and HDAC6 were associated with HIF-1α protein. Inhibition by small interfering RNA of HDAC4 and HDAC6 reduced HIF-1α protein expression and transcriptional activity. Taken together, these results suggest that class II HDACs are associated with HIF-1α stability and provide a rationale for targeting HIF-1α with HDAC inhibitors against class II isozymes. (Cancer Res 2006; 66(17): 8814-21)