bluuebunny/crossref_metadata_2025_split huggingface dataset:
Targeting of AKT1 enhances radiation toxicity of human tumor cells by inhibiting DNA-PKcs-dependent DNA double-strand break repair
Authors: Toulany Mahmoud , Kehlbach Rainer , Florczak Urszula , Sak Ali , Wang Shaomeng , Chen Jianyong , Lobrich Markus , Rodemann H. Peter 
Published: July 2008

Abstract
We have already reported that epidermal growth factor receptor/phosphatidylinositol 3-kinase/AKT signaling is an important pathway in regulating radiation sensitivity and DNA double-strand break (DNA-dsb) repair of human tumor cells. In the present study, we investigated the effect of AKT1 on DNA-dependent protein kinase catalytic subunit (DNA-PKcs) activity and DNA-dsb repair in irradiated non-small cell lung cancer cell lines A549 and H460. Treatment of cells with the specific AKT pathway inhibitor API-59CJ-OH (API; 1-5 μmol/L) reduced clonogenic survival between 40% and 85% and enhanced radiation sensitivity of both cell lines significantly. As indicated by fluorescence-activated cell sorting analysis (sub-G1 cells) and poly(ADP-ribose) polymerase cleavage, API treatment or transfection with AKT1-small interfering RNA (siRNA) induced apoptosis of H460 but not of A549 cells. However, in either apoptosis-resistant A549 or apoptosis-sensitive H460 cells, API and/or AKT1-siRNA did not enhance poly(ADP-ribose) polymerase cleavage and apoptosis following irradiation. Pretreatment of cells with API or transfection with AKT1-siRNA strongly inhibited radiation-induced phosphorylation of DNA-PKcs at T2609 and S2056 as well as repair of DNA-dsb as measured by the γ-H2AX foci assay. Coimmunoprecipitation experiments showed a complex formation of activated AKT and DNA-PKcs, supporting the assumption that AKT plays an important regulatory role in the activation of DNA-PKcs in irradiated cells. Thus, targeting of AKT enhances radiation sensitivity of lung cancer cell lines A549 and H460 most likely through specific inhibition of DNA-PKcs-dependent DNA-dsb repair but not through enhancement of radiation-induced apoptosis. [Mol Cancer Ther 2008;7(7):1772–81]
Key role for Bak activation and Bak-Bax interaction in the apoptotic response to vinblastine
Authors: Upreti Meenakshi , Chu Rong , Galitovskaya Elena , Smart Sherri K. , Chambers Timothy C. 
Published: July 2008

Abstract
Microtubule inhibitors such as vinblastine cause mitotic arrest and subsequent apoptosis through the intrinsic mitochondrial pathway. However, although Bcl-2 family proteins have been implicated as distal mediators, their precise role is largely unknown. In this study, we investigated the role of Bak in vinblastine-induced apoptosis. Bak was mainly monomeric in untreated KB-3 cells, and multimers corresponding to dimer, trimer, and higher oligomers were observed after vinblastine treatment. The oligomeric Bak species were strongly diminished in cells stably overexpressing Bcl-xL. Immunoprecipitation with a conformation-dependent Bak antibody revealed that vinblastine induced Bak activation. Reciprocal immunoprecipitations indicated that vinblastine induced the interaction of active Bak with active Bax. Furthermore, Bcl-xL overexpression prevented Bak and Bax interaction and strongly inhibited apoptosis, whereas Bcl-2 overexpression did not prevent Bak-Bax interaction and only weakly inhibited apoptosis. The relative contributions of Bak and Bax were investigated using fibroblasts deficient in one or both of these proteins; double knockouts were highly resistant compared with single knockouts, with vinblastine sensitivities in the order of Bak+/Bax+ &gt; Bak+/Bax- &gt; Bak-/Bax+ &gt; Bak-/Bax-. These results highlight Bak as a key mediator of vinblastine-induced apoptosis and show for the first time activation and oligomerization of Bak by an antimitotic agent. In addition, our results suggest that the interaction of the activated forms of Bak and Bax represents a key distal step in the apoptotic response to this important chemotherapeutic drug. [Mol Cancer Ther 2008;7(7):2224–32]
Antimigratory effect of TK1-2 is mediated in part by interfering with integrin α2β1
Authors: Kim Hyun-Kyung , Oh Dae-Shik , Lee Sang-Bae , Ha Jung-Min , Joe Young Ae 
Published: July 2008

Abstract
The recombinant two kringle domain of human tissue-type plasminogen activator (TK1-2) has been shown to inhibit endothelial cell proliferation, angiogenesis, and tumor cell growth despite of sharing a low amino acid sequence homology with angiostatin. Here, we explored a possible inhibitory mechanism of action of TK1-2 by focusing on antimigratory effect. TK1-2 effectively inhibited endothelial cell migration induced by basic fibroblast growth factor or vascular endothelial growth factor in a dose-dependent manner and tube formation on Matrigel. It blocked basic fibroblast growth factor–induced or vascular endothelial growth factor–induced phosphorylation of extracellular signal-regulated kinase 1/2 and formation of actin stress fibers and focal adhesions. Interestingly, TK1-2 alone induced the weak phosphorylation of focal adhesion kinase, whereas it inhibited focal adhesion kinase phosphorylation induced by growth factors. When immobilized, TK1-2 promoted adhesion and spreading of endothelial cells compared with bovine serum albumin. However, treatment with anti-α2β1 blocking antibody markedly diminished endothelial cell adhesion to immobilized TK1-2 compared with anti-αvβ3 or anti-α5β1 antibody. Pretreatment of soluble TK1-2 also altered the binding level of anti-α2β1 antibody to endothelial cells in fluorescence-activated cell sorting analysis. Indeed, a blocking antibody against integrin α2β1 or knocking down of integrin α2 expression prevented the inhibitory effect of TK1-2 in cell migration. Therefore, these results suggest that TK1-2 inhibits endothelial cell migration through inhibition of signaling and cytoskeleton rearrangement in part by interfering with integrin α2β1. [Mol Cancer Ther 2008;7(7):2133–41]
Antiproliferative effect of sulindac in colonic neoplasia prevention: role of COOH-terminal Src kinase
Authors: Kunte Dhananjay P. , Wali Ramesh K. , Koetsier Jennifer L. , Roy Hemant K. 
Published: July 2008

Abstract
Although the nonsteroidal anti-inflammatory drugs (NSAID) protection against colorectal cancer is well established, the molecular mechanisms remain unclear. We show herein that induction of the tumor suppressor gene COOH-terminal Src kinase (Csk) by NSAID is important for their antiproliferative and hence chemopreventive effects. In the azoxymethane-treated rat model of experimental colon carcinogenesis, sulindac treatment markedly induced Csk with a corresponding increase in inhibitory phosphorylation of Src (Tyr527). Sulindac-mediated Csk induction was replicated in the human colorectal cancer cell line HT-29, with a corresponding suppression of both Src kinase activity (63% of vehicle; P &lt; 0.05) and E-cadherin tyrosine phosphorylation (an in vivo Src target). To determine the importance of Csk in NSAID antiproliferative activity, we stably transfected a Csk-specific short hairpin RNA (shRNA) vector into HT-29 cells, thereby blunting the sulindac-mediated Csk induction. These transfectants were significantly less responsive to the antiproliferative effect of sulindac sulfide (suppression of proliferating cell nuclear antigen was 21 ± 2.3% in transfectants versus 45 ± 4.23% in wild-type cells), with a corresponding mitigation of the sulindac-mediated G1-S-phase arrest (S-phase cells 48 ± 3.6% versus 14 ± 2.8% of vehicle respectively). Importantly, the Csk shRNA cells had a marked decrease in the cyclin-dependent kinase inhibitor p21cip/waf1, a critical regulator of G1-S-phase progression (49% of wild-type cells). Moreover, although sulindac-mediated induction of p21cip/waf1 was 113% in wild-type HT-29, this induction was alleviated in the Csk shRNA transfectants (65% induction; P &lt; 0.01). Thus, this is the first demonstration that the antiproliferative activity of NSAID is modulated, at least partly, through the Csk/Src axis. [Mol Cancer Ther 2008;7(7):1797–806]
Targeting Lyn inhibits tumor growth and metastasis in Ewing's sarcoma
Authors: Guan Hui , Zhou Zhichao , Gallick Gary E. , Jia Shu-Fang , Morales Jaime , Sood Anil K. , Corey Seth J. , Kleinerman Eugenie S. 
Published: July 2008

Abstract
Src family tyrosine kinases (SFK) play an important role in growth and metastasis of many types of human malignancies. However, their significance in Ewing's sarcoma remains to be elucidated. The purpose of this study was to evaluate the role of Lyn, one member of the SFK, in Ewing's sarcoma growth and metastasis and to determine whether a SFK inhibitor can induce Ewing's tumor regression. Lyn was expressed and activated in TC71, A4573, and SK-ES human Ewing's sarcoma cells. Lyn expression was seen in 13 of 15 patient tumor samples, 6 of which showed Lyn activation. Specific inhibition of Lyn using small interfering RNA significantly decreased primary tumor growth and lytic activity, and also reduced lung metastases in vivo. Down-regulation of Lyn resulted in decreased invasive capacity of tumor cells in vitro. AP23994, a small-molecule SFK inhibitor, decreased Lyn kinase activity and suppressed TC71 cell growth in vitro in a dose-dependent manner. Furthermore, treatment of mice bearing s.c. TC71 tumors with AP23994 or with polyethylenimine/Lyn-small interfering RNA gene therapy resulted in reduced Lyn kinase activity and significant tumor growth suppression. EWS/FLI-1, which is translocation fusion protein associated with Ewing's sarcoma, regulated Lyn gene expression and kinase activity. These data suggest that targeting Lyn may be a new therapeutic approach in treatment of Ewing's sarcoma. [Mol Cancer Ther 2008;7(7):1807–16]
S1P differentially regulates migration of human ovarian cancer and human ovarian surface epithelial cells
Authors: Wang Dongmei , Zhao Zhenwen , Caperell-Grant Andrea , Yang Gong , Mok Samuel C. , Liu Jinsong , Bigsby Robert M. , Xu Yan 
Published: July 2008

Abstract
Epithelial ovarian cancer (EOC) arises from the epithelial layer covering the surface of ovaries and i.p. metastasis is commonly observed at diagnosis. Sphingosine-1-phosphate (S1P), a bioactive lipid signaling molecule, is potentially involved in EOC tumorigenesis. We have found that S1P is elevated in human EOC ascites. We show that physiologically relevant concentrations of S1P stimulate migration and invasion of EOC cells but inhibit migration of human ovarian surface epithelial (HOSE) cells. In addition, S1P inhibits lysophosphatidic acid (LPA)–induced cell migration in HOSE but not in EOC cells. We have provided the first line of evidence that the expression levels of S1P receptor subtypes are not the only determinants for how cells respond to S1P. Although S1P1 is expressed and functional in HOSE cells, the inhibitory effect mediated by S1P2 is dominant in those cells. The cellular preexisting stress fibers are also important determinants for the migratory response to S1P. Differential S1P-induced morphology changes are noted in EOC and HOSE cells. Preexisting stress fibers in HOSE cells are further enhanced by S1P treatment, resulting in the negative migratory response to S1P. By contrast, EOC cells lost stress fibers and S1P treatment induces filopodium-like structures at cell edges, which correlates with increased cell motility. In addition, inhibition of the protein kinase C pathway is likely to be involved in the inhibitory effect of S1P on LPA-induced cell migration in HOSE cells. These findings are important for the development of new therapeutics targeting S1P and LPA in EOC. [Mol Cancer Ther 2008;7(7):1993–2002]
Inhibition of centromere dynamics by eribulin (E7389) during mitotic metaphase
Authors: Okouneva Tatiana , Azarenko Olga , Wilson Leslie , Littlefield Bruce A. , Jordan Mary Ann 
Published: July 2008

Abstract
Eribulin (E7389), a synthetic analogue of halichondrin B in phase III clinical trials for breast cancer, binds to tubulin and microtubules. At low concentrations, it suppresses the growth phase of microtubule dynamic instability in interphase cells, arrests mitosis, and induces apoptosis, suggesting that suppression of spindle microtubule dynamics induces mitotic arrest. To further test this hypothesis, we measured the effects of eribulin on dynamics of centromeres and their attached kinetochore microtubules by time-lapse confocal microscopy in living mitotic U-2 OS human osteosarcoma cells. Green fluorescent protein–labeled centromere-binding protein B marked centromeres and kinetochore-microtubule plus-ends. In control cells, sister chromatid centromere pairs alternated under tension between increasing and decreasing separation (stretching and relaxing). Eribulin suppressed centromere dynamics at concentrations that arrest mitosis. At 60 nmol/L eribulin (2 × mitotic IC50), the relaxation rate was suppressed 21%, the time spent paused increased 67%, and dynamicity decreased 35% (but without reduction in mean centromere separation), indicating that eribulin decreased normal microtubule-dependent spindle tension at the kinetochores, preventing the signal for mitotic checkpoint passage. We also examined a more potent, but in tumors less efficacious antiproliferative halichondrin derivative, ER-076349. At 2 × IC50 (4 nmol/L), mitotic arrest also occurred in concert with suppressed centromere dynamics. Although media IC50 values differed 15-fold between the two compounds, the intracellular concentrations were similar, indicating more extensive relative uptake of ER-076349 into cells compared with eribulin. The strong correlation between suppression of kinetochore-microtubule dynamics and mitotic arrest indicates that the primary mechanism by which eribulin blocks mitosis is suppression of spindle microtubule dynamics. [Mol Cancer Ther 2008;7(7):2003–11]
Small-molecule inhibitor of the AP endonuclease 1/REF-1 E3330 inhibits pancreatic cancer cell growth and migration
Authors: Zou Gang-Ming , Maitra Anirban 
Published: July 2008

AbstractAP endonuclease 1 (APE1; also known as REF-1) contains a DNA repair domain and a redox regulation domain. APE1 is overexpressed in several human cancers, and disruption of APE1 function has detrimental effects on cancer cell viability. However, the selective contribution of the redox and the DNA repair domains to maintenance of cellular homeostasis in cancer has not been elucidated. In the present study, we used E3330, a small-molecule inhibitor of APE1 redox domain function, to interrogate the functional relevance of sustained redox function in pancreatic cancer. We show that E3330 significantly reduces the growth of human pancreatic cancer cells in vitro. This phenomenon was further confirmed by a small interfering RNA experiment to knockdown APE1 expression in pancreatic cancer cells. Further, the growth-inhibitory effects of E3330 are accentuated by hypoxia, and this is accompanied by striking inhibition in the DNA-binding ability of hypoxia-inducible factor-1α, a hypoxia-induced transcription factor. E3330 exposure promotes endogenous reactive oxygen species formation in pancreatic cancer cells, and the resulting oxidative stress is associated with higher levels of oxidized, and hence inactive, SHP-2, an essential protein tyrosine phosphatase that promotes cancer cell proliferation in its active state. Finally, E3330 treatment inhibits pancreatic cancer cell migration as assessed by in vitro chemokine assays. E3330 shows anticancer properties at multiple functional levels in pancreatic cancer, such as inhibition of cancer cell growth and migration. Inhibition of the APE1 redox function through pharmacologic means has the potential to become a promising therapeutic strategy in this disease. [Mol Cancer Ther 2008;7(7):2012–21]
Thiostrepton selectively targets breast cancer cells through inhibition of forkhead box M1 expression
Authors: Kwok Jimmy M-M. , Myatt Stephen S. , Marson Charles M. , Coombes R. Charles , Constantinidou Demetra , Lam Eric W-F. 
Published: July 2008

Abstract
Elevated expression or activity of the transcription factor forkhead box M1 (FOXM1) is associated with the development and progression of many malignancies, including breast cancer. In this study, we show that the thiazole antibiotic thiostrepton selectively induces cell cycle arrest and cell death in breast cancer cells through down-regulating FOXM1 expression. Crucially, our data show that thiostrepton treatment reduced FOXM1 expression in a time- and dose-dependent manner, independent of de novo protein synthesis and predominantly at transcriptional and gene promoter levels. Our results indicate that thiostrepton can induce cell death through caspase-dependent intrinsic and extrinsic apoptotic pathways as well as through caspase-independent death mechanisms, as observed in MCF-7 cells, which are deficient of caspase-3 and caspase-7. Cell cycle analysis showed that thiostrepton induced cell cycle arrest at G1 and S phases and cell death, concomitant with FOXM1 repression in breast cancer cells. Furthermore, thiostrepton also shows efficacy in repressing breast cancer cell migration, metastasis, and transformation, which are all downstream functional attributes of FOXM1. We also show that overexpression of a constitutively active FOXM1 mutant, ΔN-FOXM1, can abrogate the antiproliferative effects of thiostrepton. Interestingly, thiostrepton has no affect on FOXM1 expression and proliferation of the untransformed MCF-10A breast epithelial cells. Collectively, our data show that FOXM1 is one of the primary cellular targets of thiostrepton in breast cancer cells and that thiostrepton may represent a novel lead compound for targeted therapy of breast cancer with minimal toxicity against noncancer cells. [Mol Cancer Ther 2008;7(7):2022–32]
Laser postionization secondary neutral mass spectrometry in tissue: a powerful tool for elemental and molecular imaging in the development of targeted drugs
Authors: Wittig Andrea , Arlinghaus Heinrich F. , Kriegeskotte Christian , Moss Raymond L. , Appelman Klaas , Schmid Kurt W. , Sauerwein Wolfgang A.G. 
Published: July 2008

Abstract
The exact intracellular localization and distribution of molecules and elements becomes increasingly important for the development of targeted therapies and contrast agents. We show that laser postionization secondary neutral mass spectrometry (laser-SNMS) is well suited to localize particular elements and small molecules with subcellular spatial resolution applying the technique exemplary to Boron Neutron Capture Therapy (BNCT). We showed in a murine sarcoma that the drugs used for clinical BNCT, namely l-para-boronophenylalanine (700 mg/kg body weight i.p.) and sodium mercaptoundecahydro-closo-dodecaborate (200 mg/kg body weight i.p.), transport the therapeutic agent 10B into the cytoplasm and into the nucleus itself, the most sensitive area of the cell. Sodium mercaptoundecahydro-closo-dodecaborate distributes 10B homogeneously and l-para-boronophenylalanine heterogeneously. When combining laser-SNMS with prompt γ-ray analysis as a screening technique, strategies for BNCT can be elaborated to develop new drugs or to improve the use of existing drugs on scientifically based evidence. The study shows the power of laser-SNMS in the early stages of drug development, also outside BNCT. [Mol Cancer Ther 2008;7(7):1763–71]
Silibinin inhibits cytokine-induced signaling cascades and down-regulates inducible nitric oxide synthase in human lung carcinoma A549 cells
Authors: Chittezhath Manesh , Deep Gagan , Singh Rana P. , Agarwal Chapla , Agarwal Rajesh 
Published: July 2008

Abstract
Recently, we reported that silibinin inhibits primary lung tumor growth and progression in mice and down-regulates inducible nitric oxide synthase (iNOS) expression in tumors; however, the mechanisms of silibinin action are largely not understood. Also, the activation of signaling pathways inducing various transcription factors are associated with lung carcinogenesis and their inhibition could be an effective strategy to prevent and/or treat lung cancer. Herein, we used human lung epithelial carcinoma A549 cells to explore the potential mechanisms and observed strong iNOS expression by cytokine mixture (containing 100 units/mL IFN-γ + 0.5 ng/mL interleukin-1β + 10 ng/mL tumor necrosis factor-α). We also examined the cytokine mixture–activated signaling cascades, which could potentially up-regulate iNOS expression, and then examined the effect of silibinin (50-200 μmol/L) on these signaling cascades. Silibinin treatment inhibited, albeit to different extent, the cytokine mixture–induced activation of signal transducer and activator of transcription 1 (Tyr701), signal transducer and activator of transcription 3 (Tyr705), activator protein-1 family of transcription factors, and nuclear factor-κB. The results for activator protein-1 were correlated with the decreased nuclear levels of phosphorylated c-Jun, c-Jun, JunB, JunD, phosphorylated c-Fos, and c-Fos. Further, silibinin also strongly decreased cytokine mixture–induced phosphorylation of extracellular signal-regulated kinase 1/2 but only marginally affected JNK1/2 phosphorylation. Silibinin treatment also decreased constitutive p38 phosphorylation in the presence or absence of cytokine mixture. Downstream of these pathways, silibinin strongly decreased cytokine mixture–induced expression of hypoxia-inducible factor-1α without any considerable effect on Akt activation. Cytokine mixture–induced iNOS expression was completely inhibited by silibinin. Overall, these results suggest that silibinin could target multiple cytokine-induced signaling pathways to down-regulate iNOS expression in lung cancer cells and that could contribute to its overall cancer preventive efficacy against lung tumorigenesis. [Mol Cancer Ther 2008;7(7):1817–26]
Active roles for inhibitory κB kinases α and β in nuclear factor-κB–mediated chemoresistance to doxorubicin
Authors: Bednarski Brian K. , Ding Xiaoyu , Coombe Kavita , Baldwin Albert S. , Kim Hong J. 
Published: July 2008

Abstract
Chemotherapy agents have been shown to induce the transcription factor nuclear factor-κB (NF-κB) and subsequent chemoresistance in fibrosarcomas and other cancers. The mechanism of NF-κB-mediated chemoresistance remains unclear, with a previous report suggesting that doxorubicin induces this response independent of the inhibitory κB kinases (IKK). Other studies have indicated that IKKβ, but not IKKα, is required. Mouse embryo fibroblasts devoid of IKKα, IKKβ, or both subunits (double knockout) were treated with doxorubicin. The absence of either IKKα or IKKβ or both kinases resulted in impaired induction of NF-κB DNA-binding activity in response to doxorubicin. To provide a valid clinical correlate, HT1080 human fibrosarcoma cells were transfected with small interference RNA specific for IKKα or IKKβ and then subsequently treated with doxorubicin. Knockdown of IKKα severely impaired the ability of doxorubicin to initiate NF-κB DNA-binding activity. However, a decrease in either IKKα or IKKβ resulted in decreased phosphorylation of p65 in response to doxorubicin. The inhibition of doxorubicin-induced NF-κB activation by the knockdown of either catalytic subunit resulted in increased cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase and increased apoptosis when compared with doxorubicin alone. The results of this study validate current approaches aimed at NF-κB inhibition to improve clinical therapies. Moreover, we show that IKKα plays a critical role in NF-κB-mediated chemoresistance in response to doxorubicin and may serve as a potential target in combinational strategies to improve chemotherapeutic response. [Mol Cancer Ther 2008;7(7):1827–35]