bluuebunny/crossref_metadata_2025_split huggingface dataset:
Docetaxel induces cell death through mitotic catastrophe in human breast cancer cells
Authors: Morse David L. , Gray Heather , Payne Claire M. , Gillies Robert J. 
Published: March 2006

Abstract
Apoptosis has long been considered to be the prevailing mechanism of cell death in response to chemotherapy. Currently, a more heterogeneous model of tumor response to therapy is acknowledged wherein multiple modes of death combine to generate the overall tumor response. The resulting mechanisms of cell death are likely determined by the mechanism of action of the drug, the dosing regimen used, and the genetic background of the cells within the tumor. This study describes a nonapoptotic response to docetaxel therapy in human breast cancer cells of increasing cancer progression (MCF-10A, MCF-7, and MDA-mb-231). Docetaxel is a microtubule-stabilizing taxane that is being used in the clinic for the treatment of breast and prostate cancers and small cell carcinoma of the lung. The genetic backgrounds of these cells were characterized for the status of key pathways and gene products involved in drug response and cell death. Cellular responses to docetaxel were assessed by characterizing cell viability, cell cycle checkpoint arrest, and mechanisms of cell death. Mechanisms of cell death were determined by Annexin V binding and scoring of cytology-stained cells by morphology and transmission electron microscopy. The primary mechanism of death was determined to be mitotic catastrophe by scoring of micronucleated cells and cells undergoing aberrant mitosis. Other, nonapoptotic modes of death were also determined. No significant changes in levels of apoptosis were observed in response to docetaxel.
Differential cellular and molecular effects of bortezomib, a proteasome inhibitor, in human breast cancer cells
Authors: Codony-Servat Jordi , Tapia Maria A. , Bosch Marta , Oliva Cristina , Domingo-Domenech Josep , Mellado Begoña , Rolfe Mark , Ross Jeffrey S. , Gascon Pere , Rovira Ana , Albanell Joan 
Published: March 2006

Abstract
The cellular and molecular effects of the proteasome inhibitor bortezomib on breast cancer cells are as yet poorly characterized. Here, in a panel of six breast cancer cell lines, bortezomib reduced viability in a concentration-dependent, time-dependent, and cell line–dependent manner. Proteasome activity was relatively high in two of the three more resistant cell lines. No relationship was observed between bortezomib effects on cell viability and expression/phosphorylation of HER-2, epidermal growth factor receptor (EGFR), AKT, or extracellular signal-regulated kinase 1/2 (ERK1/2). Molecular effects of bortezomib were further studied in SK-BR-3 and BT-474 cells because they share expression of EGFR and overexpression of HER-2 while, in contrast, SK-BR-3 cells were 200-fold more sensitive to this agent. Proteasome activity was inhibited to a similar extent in the two cell lines, and known proteasome substrates accumulated similarly. In SK-BR-3 cells, a marked inhibition of EGFR, HER-2, and AKT phosphorylation was observed at a clinically relevant concentration of bortezomib. In contrast, phosphorylation of Raf/mitogen-activated protein kinase kinase 1/2 (MEK 1/2)/ERK1/2 increased by bortezomib. In BT-474 cells, the effects were much less pronounced. Treatment of SK-BR-3 cells with bortezomib combined with pharmacologic inhibitors of EGFR, phosphatidylinositol 3′-kinase, or MEK resulted in modest or no enhancement of the effects on cell viability. Collectively, these results show that bortezomib has differential cellular and molecular effects in human breast cancer cells. The bortezomib-observed effects on signaling transduction molecules might be relevant to help to design mechanistic-based combination treatments. [Mol Cancer Ther 2006;5(3):665–75]
Potentiation of the lethality of the histone deacetylase inhibitor LAQ824 by the cyclin-dependent kinase inhibitor roscovitine in human leukemia cells
Authors: Rosato Roberto R. , Almenara Jorge A. , Maggio Sonia C. , Atadja Peter , Craig Ruth , Vrana Julie , Dent Paul , Grant Steven 
Published: March 2006

Abstract
Interactions between the novel histone deacetylase inhibitor LAQ824 and the cyclin-dependent kinase inhibitor roscovitine were examined in human leukemia cells. Pretreatment (24 hours) with a subtoxic concentration of LAQ824 (30 nmol/L) followed by a minimally toxic concentration of roscovitine (10 μmol/L; 24 hours) resulted in greater than additive effects on apoptosis in U937, Jurkat, and HL-60 human leukemia cells and blasts from three patients with acute myelogenous leukemia. These events were associated with enhanced conformational changes in Bax; mitochondrial release of cytochrome c, Smac/DIABLO, and apoptosis-inducing factor; and a marked increase in caspase activation. LAQ824/roscovitine–treated cells displayed caspase-dependent down-regulation of p21CIP1 and Mcl-1 and a pronounced caspase-independent reduction in X-linked inhibitor of apoptosis (XIAP) expression. The lethality of this regimen was significantly attenuated by ectopic expression of XIAP, a nuclear localization signal–defective p21CIP1 mutant, Mcl-1, and Bcl-2. Combined exposure to LAQ824 and roscovitine resulted in a significant reduction in XIAP mRNA levels and diminished phosphorylation of the carboxyl-terminal domain of RNA polymerase II. Notably, roscovitine blocked LAQ824-mediated differentiation. Finally, LAQ824 and roscovitine individually and in combination triggered an increase in generation of reactive oxygen species; moreover, coadministration of the free radical scavenger N-acetylcysteine prevented LAQ824/roscovitine–mediated mitochondrial injury and apoptosis. Collectively, these findings suggest that combined treatment of human leukemia cells with LAQ824 and roscovitine disrupts maturation and synergistically induces apoptosis, lending further support for an antileukemic strategy combining novel histone deacetylase and cyclin-dependent kinase inhibitors.
Semisynthetic homoharringtonine induces apoptosis via inhibition of protein synthesis and triggers rapid myeloid cell leukemia-1 down-regulation in myeloid leukemia cells
Authors: Tang Ruoping , Faussat Anne-Marie , Majdak Patricia , Marzac Christophe , Dubrulle Sabine , Marjanovic Zora , Legrand Ollivier , Marie Jean-Pierre 
Published: March 2006

AbstractSemisynthetic homoharringtonine (ssHHT) is now being evaluated in phase II clinical trials for the treatment of chronic myelogenous leukemia and acute myelogenous leukemia patients. Here, we examined the mechanism of the apoptosis induced by ssHHT in myeloid leukemia cells. First, we have shown that ssHHT induces apoptosis in HL60 and HL60/MRP cell lines in a time- and dose-dependent manner, and independently of the expression of Bax. The decrease of mitochondrial membrane potential and the release of cytochrome c were observed in the apoptotic cells induced by ssHHT. To unveil the relationship between ssHHT and the mitochondrial disruption, we have shown that ssHHT decreased myeloid cell leukemia-1 (Mcl-1) expression and induced Bcl-2 cleavage in HL60 and HL60/MRP cell lines. The Bcl-2 cleavage could be inhibited by the Z-VAD.fmk caspase inhibitor. However, Mcl-1 turnover was very rapid and occurred before caspase activation. The Mcl-1 turnover was only induced by ssHHT and cycloheximide, but not by daunorubicin and cytosine arabinoside, and could be restored by proteasome inhibitors. Second, we confirmed that ssHHT rapidly induced massive apoptosis in acute myelogenous leukemia patient cells. We have also confirmed the release of cytochrome c and a rapid turnover of Mcl-1 in these patient cells, taking place only in apoptotic cells induced by ssHHT but not in cells undergoing spontaneous apoptosis. Finally, we have shown that ssHHT inhibits protein synthesis in both cell line and patient cells. We suggest that the inhibition of protein synthesis and resulting Mcl-1 turnover play a key role in the apoptosis induced by ssHHT. Our results encourage further clinical trials for the use of ssHHT in acute myelogenous leukemia. [Mol Cancer Ther 2006;5(3):723–31]
Role of O6-alkylguanine-DNA alkyltransferase in the cytotoxic activity of cloretazine
Authors: Ishiguro Kimiko , Shyam Krishnamurthy , Penketh Philip G. , Sartorelli Alan C. 
Published: March 2006

Abstract
Cloretazine (VNP40101M; 101M; 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)-2-[(methylamino)carbonyl]hydrazine) is a sulfonylhydrazine prodrug that generates both chloroethylating and carbamoylating species on activation. To explore the molecular mechanisms underlying the broad anticancer activity observed in preclinical studies, cloretazine and chloroethylating-only [i.e., 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine] and carbamoylating-only (i.e., 1,2-bis(methylsulfonyl)-1-[(methylamino)carbonyl]hydrazine) analogues were evaluated in five murine hematopoietic cell lines. These cell lines were separable into two groups by virtue of their sensitivity to 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine; the sensitive group included L1210, P388, and F-MEL leukemias (IC50s, 6–8 μmol/L) and the resistant group consisted of Ba/F3 bone marrow and WEHI-3B leukemia cells (IC50s, 50–70 μmol/L). Resistant cells expressed O6-alkylguanine-DNA alkyltransferase (AGT), whereas sensitive cells did not. A correlation existed between AGT expression and the functional status of p53; AGT− cells possessed defective p53, whereas AGT+ cells contained wild-type p53. Based on recent findings on regulation of AGT gene expression by others, we suspect that silencing of the AGT gene by promoter hypermethylation frequently occurs during tumor progression involving p53 inactivation. O6-Chloroethylguanine is the initial DNA lesion that progresses to lethal interstrand DNA cross-links. Cloretazine exhibited a much higher preference toward the O6-chloroethylation of guanine, as measured by the difference in IC50s to wild-type and AGT-transfected L1210 cells, than 1,3-bis(2-chloroethyl)-1-nitrosourea, which targets the same site in DNA. Preferential toxicity of cloretazine against AGT− tumor cells coupled with decreased toxicity to AGT+ cells in host tissues constitute the therapeutic basis for cloretazine.
AP23846, a novel and highly potent Src family kinase inhibitor, reduces vascular endothelial growth factor and interleukin-8 expression in human solid tumor cell lines and abrogates downstream angiogenic processes
Authors: Summy Justin M. , Trevino Jose G. , Lesslie Donald P. , Baker Cheryl H. , Shakespeare William C. , Wang Yihan , Sundaramoorthi Raji , Metcalf Chester A. , Keats Jeffrey A. , Sawyer Tomi K. , Gallick Gary E. 
Published: March 2006

Abstract
c-Src is frequently activated in human malignancies, including colon, breast, and pancreatic carcinomas. Several recent studies have shown that activation of Src family kinases leads to tumor progression and metastasis by increasing cellular migration and invasion, promoting cell growth and survival, and deregulating expression of proangiogenic molecules. Therefore, selective inhibitors of Src are being developed for cancer therapy. In this study, we characterize the biological effects of the novel ATP-based Src family kinase inhibitor, AP23846, in tumor cells with high Src activity. As a lead compound, AP23846 is a potent c-Src kinase inhibitor (IC50 ∼0.5 nmol/L in vitro, ∼10-fold more potent than PP2, the most widely used commercially available Src family kinase inhibitor). At concentrations of 1 μmol/L, AP23846 led to complete Src inhibition for 48 hours in cells. No cytotoxicity was observed under these conditions, although proliferation rates were slower. Therefore, this was an excellent inhibitor to examine Src-regulated signaling pathways in tumor cells. AP23846 reduced cellular migration, vascular endothelial growth factor, and interleukin-8 in a dose-dependent fashion in pancreatic adenocarcinoma cells grown in vitro. Correspondingly, cell culture supernatants from L3.6pl pancreatic adenocarcinoma cells pretreated with AP23846 failed to promote migration of hepatic endothelial cells in vitro and failed to support angiogenesis into gel foams implanted s.c. in mice in vivo. These results suggest that Src inhibitors affect biological properties of tumor progression and may be useful as cancer therapeutic agents in more advanced disease. [Mol Cancer Ther 2005;4(12):1900–11]
Comparison of biological effects of non-nucleoside DNA methylation inhibitors versus 5-aza-2′-deoxycytidine
Authors: Chuang Jody C. , Yoo Christine B. , Kwan Jennifer M. , Li Tony W.H. , Liang Gangning , Yang Allen S. , Jones Peter A. 
Published: March 2006

AbstractDNA cytosine methylation plays a considerable role in normal development, gene regulation, and carcinogenesis. Hypermethylation of the promoters of some tumor suppressor genes and the associated silencing of these genes often occur in certain cancer types. The reversal of this process by DNA methylation inhibitors is a promising new strategy for cancer therapy. In addition to the four well-characterized nucleoside analogue methylation inhibitors, 5-azacytidine, 5-aza-2′-deoxycytidine (5-Aza-CdR), 5-fluoro-2′-deoxycytidine, and zebularine, there is a growing list of non-nucleoside inhibitors. However, a systemic study comparing these potential demethylating agents has not been done. In this study, we examined three non-nucleoside demethylating agents, (−)-epigallocatechin-3-gallate, hydralazine, and procainamide, and compared their effects and potencies with 5-Aza-CdR, the most potent DNA methylation inhibitor. We found that 5-Aza-CdR is far more effective in DNA methylation inhibition as well as in reactivating genes, compared with non-nucleoside inhibitors.
Knockdown of the cytoprotective chaperone, clusterin, chemosensitizes human breast cancer cells bothin vitroandin vivo
Authors: So Alan , Sinnemann Shannon , Huntsman David , Fazli Ladan , Gleave Martin 
Published: March 2006

AbstractClusterin is a stress-associated cytoprotective chaperone up-regulated by various apoptotic triggers in many cancers and confers treatment resistance when overexpressed. The objectives of this study were to evaluate clusterin expression levels in human breast cancer and to determine whether antisense oligonucleotides or double-stranded small interfering RNAs (siRNA) targeting the clusterin gene enhance apoptosis induced by paclitaxel. Clusterin immunostaining was evaluated in a tissue microarray of 379 spotted breast cancers. The effect of hormone withdrawal, paclitaxel treatment, clusterin antisense oligonucleotide (OGX-011), and siRNA treatments on clusterin expression was examined in MCF-7 and MDA-MB-231 cells. Northern, quantitative real-time PCR, and Western analyses were used to measure change in clusterin mRNA and protein levels. The effect of OGX-011 or siRNA clusterin treatment on chemosensitivity to paclitaxel was done in both cell lines in vitro, whereas the ability of OGX-011 to chemosensitize in vivo was evaluated in athymic mice bearing MCF-7 tumors. Clusterin was expressed in 62.5% of tumors within the tissue microarray. Clusterin expression increased after estrogen withdrawal and paclitaxel treatment in vitro in MCF-7 cells. OGX-011 or siRNA clusterin decreased clusterin levels by &gt;90% in a dose-dependent, sequence-specific manner and significantly enhanced chemosensitivity to paclitaxel in vitro. When combined, OGX-011 or siRNA clusterin reduced the IC50 by 2-log compared with paclitaxel alone. In vivo administration of OGX-011 enhanced the effects of paclitaxel to significantly delay MCF-7 tumor growth. These data identify clusterin as a valid therapeutic target and provides preclinical proof-of-principle to test OGX-011 in multimodality therapies for breast cancer. [Mol Cancer Ther 2005;4(12):1837–49]
Restoration of p53 function for selective Fas-mediated apoptosis in human and rat glioma cells in vitro and in vivo by a p53 COOH-terminal peptide
Authors: Senatus Patrick B. , Li Yin , Mandigo Christopher , Nichols Gwen , Moise Gaetan , Mao Yuehua , Brown Melandee D. , Anderson Richard C. , Parsa Andrew T. , Brandt-Rauf Paul W. , Bruce Jeffrey N. , Fine Robert L. 
Published: March 2006

Abstract
We have shown that a COOH-terminal peptide of p53 (amino acids 361–382, p53p), linked to the truncated homeobox domain of Antennapedia (Ant) as a carrier for transduction, induced rapid apoptosis in human premalignant and malignant cell lines. Here, we report that human and rat glioma lines containing endogenous mutant p53 or wild-type (WT) p53 were induced into apoptosis by exposure to this peptide called p53p-Ant. The peptide was comparatively nontoxic to proliferating nonmalignant human and rat glial cell lines containing WT p53 and proliferating normal human peripheral marrow blood stem cells. Degree of sensitivity to the peptide correlated directly with the level of endogenous p53 expression and mutant p53 conformation. Apoptosis induction by p53p-Ant was quantitated by terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling assay and Annexin V staining in human glioma cells in vitro and in a syngeneic orthotopic 9L glioma rat model using convection-enhanced delivery in vivo. The mechanism of cell death by this peptide was solely through the Fas extrinsic apoptotic pathway. p53p-Ant induced a 3-fold increase in extracellular membrane Fas expression in glioma cells but no significant increase in nonmalignant glial cells. These data suggest that p53 function for inducing Fas-mediated apoptosis in gliomas, which express sufficient quantities of endogenous mutant or WT p53, may be restored or activated, respectively, by a cell-permeable peptide derived from the p53 COOH-terminal regulatory domain (p53p-Ant). p53p-Ant may serve as a prototypic model for the development of new anticancer agents with unique selectivity for glioma cancer cells and it can be successfully delivered in vivo into a brain tumor by a convection-enhanced delivery system, which circumvents the blood-brain barrier. [Mol Cancer Ther 2006;5(1):20–8]
Valproic acid induces growth arrest, apoptosis, and senescence in medulloblastomas by increasing histone hyperacetylation and regulating expression of p21Cip1, CDK4, and CMYC
Authors: Li Xiao-Nan , Shu Qin , Su Jack Men-Feng , Perlaky Laszlo , Blaney Susan M. , Lau Ching C. 
Published: March 2006

Abstract
Valproic acid is a well-tolerated anticonvulsant that has been identified recently as a histone deacetylase inhibitor. To evaluate the antitumor efficacy and mechanisms of action of valproic acid in medulloblastoma and supratentorial primitive neuroectodermal tumor (sPNET), which are among the most common malignant brain tumors in children with poor prognosis, two medulloblastoma (DAOY and D283-MED) and one sPNET (PFSK) cell lines were treated with valproic acid and evaluated with a panel of in vitro and in vivo assays. Our results showed that valproic acid, at clinically safe concentrations (0.6 and 1 mmol/L), induced potent growth inhibition, cell cycle arrest, apoptosis, senescence, and differentiation and suppressed colony-forming efficiency and tumorigenicity in a time- and dose-dependent manner. The medulloblastoma cell lines were more responsive than the sPNET cell line and can be induced to irreversible suppression of proliferation and significantly reduced tumorigenicity by 0.6 and 1 mmol/L valproic acid. Daily i.p. injection of valproic acid (400 mg/kg) for 28 days significantly inhibited the in vivo growth of DAOY and D283-MED s.c. xenografts in severe combined immunodeficient mice. With Western hybridization and real-time reverse transcription-PCR, we further showed that the antitumor activities of valproic acid correlated with induction of histone (H3 and H4) hyperacetylation, activation of p21, and suppression of TP53, CDK4, and CMYC expression. In conclusion, valproic acid possesses potent in vitro and in vivo antimedulloblastoma activities that correlated with induction of histone hyperacetylation and regulation of pathways critical for maintaining growth inhibition and cell cycle arrest. Therefore, valproic acid may represent a novel therapeutic option in medulloblastoma treatment. [Mol Cancer Ther 2005;4(12):1912–22]
Radiosensitization of MDA-MB-231 breast tumor cells by adenovirus-mediated overexpression of a fragment of the XRCC4 protein
Authors: Jones Kara R. , Gewirtz David A. , Yannone Steven M. , Zhou Shaoming , Schatz David G. , Valerie Kristoffer , Povirk Lawrence F. 
Published: March 2006

Abstract
Incomplete DNA repair or misrepair can contribute to the cytotoxicity of DNA double-strand breaks. Consequently, interference with double-strand break repair, by pharmacologic or genetic means, is likely to sensitize tumor cells to ionizing radiation. The current studies were designed to inhibit the nonhomologous end joining repair pathway by interfering with the function of the XRCC4/ligase IV complex. A PCR-generated fragment of the XRCC4 gene, encompassing the homodimerization and ligase IV–binding domains, was inserted into a plasmid vector (pFLAG-CMV-2) expressing the FLAG peptide and the cassette encoding FLAG-tagged XRCC4 fragment was cloned into an adenoviral vector. Both the plasmid and the corresponding adenovirus elicited robust expression of a truncated XRCC4 protein designed to compete in a dominant-negative fashion with full-length XRCC4 for binding to ligase IV. Binding of the XRCC4 fragment to ligase IV in vivo was confirmed by immunoprecipitation. Clonogenic survival assays showed that the adenovirus expressing the truncated XRCC4 protein sensitizes MDA-MB-231 breast tumor cells to ionizing radiation, presumably through interference with the functional activity of ligase IV, leading to inhibition of the final ligation step in end joining. These studies support the potential clinical utility of combining radiation therapy with agents that inhibit DNA double-strand break repair.
In vivo synergy between topoisomerase II and histone deacetylase inhibitors: predictive correlates
Authors: Marchion Douglas C. , Bicaku Elona , Daud Adil I. , Sullivan Daniel M. , Munster Pamela N. 
Published: March 2006

Abstract
Histone deacetylase inhibitors (HDACi) are a promising class of anticancer agents, yet the specific biological effects resulting in cell death are still poorly understood and clinically relevant markers of response are not adequately defined. The anticonvulsant valproic acid has recently emerged as an HDACi, and in vitro studies suggested that valproic acid may potentiate cytotoxic agents. We evaluated the pharmacologic and biological effects of valproic acid on histone acetylation, chromatin structure, and DNA damage induced by topoisomerase II inhibitors in mice bearing breast cancer tumors and developed an ex vivo methodology for response prediction using comet assays. The exposure of mice to valproic acid before exposure to epirubicin led to tumor regression when valproic acid was given for 48 hours at concentrations sufficient for histone hyperacetylation, down-regulation of heterochromatin maintenance proteins, and chromatin decondensation. Tumor response was accurately predicted by ex vivo comet moments. Valproic acid did not exacerbate epirubicin-related toxicity. Antitumor effects were not observed with valproic acid alone despite biologically active valproic acid concentrations. These findings suggest that exposure of tumor-bearing mice to valproic acid potentiated the antitumor effects of topoisomerase II inhibitors without enhancing toxicity. The HDACi-induced histone acetylation and modulation of heterochromatin correlated with potentiation of epirubicin-mediated DNA damage. However, these effects did not result in antitumor activity when using a HDACi alone and hence should not be considered a surrogate marker. Ex vivo comet assays may be useful as a predictive tool when tumor cells are limited and serial biopsies are difficult to obtain. [Mol Cancer Ther 2005;4(12):1993–2000]