bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2448: Inhibiting the DLL4/Notch pathway delays tumor recurrence and decreases tumorigenicity in pancreatic cancer
Authors: Fischer Marcus , Yen Wan-Ching , Beviglia Lucia , Yeung Pete , Lewicki John , Gurney Austin , Hoey Timothy 
Published: June 2012

Abstract
It is becoming increasingly evident that cancer stem cells drive tumor growth and progression and are preferentially resistant to chemotherapy. Previously, we demonstrated that interfering with the Delta-like 4 ligand (DLL4)/Notch signaling by anti-DLL4 antibodies decreased tumor growth in a pancreatic xenograft model, delayed tumor recurrence following chemotherapy, and reduced the pancreatic cancer stem cell (CSC) fraction.
In this study, we evaluated the response of seven pancreatic xenograft tumors to anti-DLL4 antibodies as a single agent and when combined with gemcitabine. Utilizing an in vivo limiting dilution assay, we tested the ability of cells from previously treated xenografts to re-grow tumors after serial transplantation to quantify CSCs. We discovered that anti-DLL4 was efficacious as a single agent in all seven tumor models. In all seven models, when anti-DLL4 was combined with gemcitabine, the therapy provided significant efficacy over that of gemcitabine alone. This combination therapy resulted in tumor regression in three of these models. The antibody therapy reduced the CSC fraction, while gemcitabine treatment alone enriched for the CSC. The chemotherapy/antibody combination further reduced the CSC fraction compared to anti-DLL4 alone.
To analyze the mechanism of action of inhibiting DLL4-Notch signaling in tumor cells and in the host vasculature, we tested a human specific DLL4 mAb and a murine specific DLL4 mAb as single agents. Anti-human DLL4 reduced the tumorigenicity of pancreatic tumor cells, while anti-murine DLL4 had no effect on tumor initiating cell frequency. In a tumor recurrence model, the human specific DLL4 mAb delayed tumor recurrence following the termination of gemcitabine while the murine specific DLL4 mAb decreased the growth rate of recurrent tumors. The combination of human and murine targeting DLL4 mAbs produced an additive effect in reducing tumor recurrence. These data support the rationale for targeting the DLL4/Notch pathway in pancreatic cancer and provide evidence of the therapeutic utility of targeting pathways, such as Notch, required for cancer stem cell self renewal.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2448. doi:10.1158/1538-7445.AM2011-2448
Abstract 2469: ATM inhibitor 55933 abolishes the radiation resistance of CD44+/CD24−or low subsets of breast cancer cells
Authors: Yin Hong , Glass Jonathan 
Published: June 2012

Abstract
CD44+/CD24− subsets of breast cancer cells are enriched in cancer stem-like cells (CSC) and are radiation resistant. We isolated ESA+/CD44+/CD24− or low subsets by flow cytometry from MCF7, MDA-MB231, and HCC1937 breast cancer cell lines and primary cultures of breast cancer cells from two patients. The isolated CD44+/CD24−orlow subsets showed a 50 to 70% increase of sphere formation by in suspension culture in serum-free medium compared to CD44−/CD24high subsets. CD44+/CD24−or low subsets of the cell lines and primary cultures showed a significantly increased radiation resistance compared to the CD44−/CD24high cell line subsets or the unsorted primary cells with &gt; 40% increased survival at 2Gy. Post-radiation survival showed that the radiation resistance was dependent on the CD44+/CD24 −or low cell phenotype. The correlation of CD44/CD24 status with radiation resistance was demonstrated by culture of the subsets. After 2 weeks of culture the following transitions occurred: 1) CD44+/CD24−or low cells changed to CD44−/CD24high cells (MCF-7 and HCC1937) or to CD44+/CD24+ (MDA-MB-231); and 2) CD44−/CD24 high (MCF-7 and HCC1937) and CD44+/CD24+ (MDA-MB-231) cells became CD44+/CD24−or low cells. Cells that lost the CD44+/CD24 −or low phenotype were no longer radiation resistant. The mechanisms of increased radiation resistance in CD44+/CD24−orlow subsets was not a function of non-homologous end joining (NHEJ) as there was no in vivo and in vitro change in NHEJ activity in the resistant cells nor altered expression of the NHEJ related proteins Ku 80, Ku70, PARP-1, and DNA-PK. However, there were differences ATM activity between CD44+/CD24−or low and the CD44−/CD24 high (MCF-7 and primary breast cancer) or CD44+/CD24+ (MDA-MB-231) subsets. Depending on the cell type and radiation dose, ATM phsophorylation increased by 2-5 fold in radiated CD44+/CD24−or low subsets of breast cancer cell lines and primary cultured breast cancer cells compared to the control subsets. The ATM inhibitor 55933 in a dose-dependent manner increased radiation sensitivity of all subsets including significantly abolishing the radiation resistance of CD44+/CD24−or low subsets of cells. After 2Gy of radiation, the survival fractions of cells treated with10μM of 55933 were 8-10 fold lower than that of untreated cells and were now similar between CD44+/CD24−or low subsets and control subsets for the cell lines and primary cultures. In conclusion, ATM is a candidate target for eliminating the radiation resistance of CSC's of breast cancer.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2469. doi:10.1158/1538-7445.AM2011-2469
Abstract 2479: Detecting Abelson tyrosine kinase activation by ATM and DNA-PK after exposure to ionizing radiation using a peptide biosensor
Authors: Tang Jiabin , Wang Jean Y. , Parker Laurie 
Published: June 2012

Abstract
Abelson (Abl) kinase is a non-receptor tyrosine kinase that is involved in many cellular processes, including survival, differentiation and apoptosis. Abl is activated in the response to DNA damage, and is involved in the decision between DNA repair versus apoptosis. It is widely accepted that Abl is regulated in response to DNA double-strand breaks (DSBs) by ataxia telangiectasia mutated protein (ATM) via phosphorylation of Abl at S465. However, other aspects of this complex signaling response have been unclear, including the role of other kinases such as DNA-dependent protein kinase (DNA-PK), because of the difficulties of detecting subtle changes in Abl activation through endogenous substrates. Here, we show Abl is activated in a mutant cell line that cannot be phosphorylated by ATM at S465 (Abl-S465A-EGFP) after exposure to ionizing radiation (IR) using a peptide biosensor we developed for Abl kinase. This biosensor contains the following functional modules: a highly specific Abl kinase substrate, an Abl SH3 binding ligand, a photocleavable linker, a biotin tag and a cell penetrating peptide derived from Hiv-TAT to aid intracellular delivery of cargo across the plasma membrane. Using a combination of chemical biology approaches, Western blot for the phosphorylation of the biosensor peptide and high-resolution MS-based phosphoproteomics, we identified a potential role for DNA-PK in activating Abl kinase after IR, independent of ATM and S465. This information about the importance of DNA-PK in this signaling pathway may lead to a better understanding of c-Abl's function in the response to IR, and could be useful to develop strategies to combat radioresistance or improve radiosensitivity in tumors.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2479. doi:10.1158/1538-7445.AM2011-2479
Abstract 2480: Low dose radiation- and thiol-induced effects on micronuclei formation following fractionated irradiation
Authors: Murley Jeffrey S. , Miller Richard C. , Baker Kenneth L. , Murley Tyler S. , Miller Kristin L. , Sullivan Joseph T. , Wardak Hamid , Grdina David J. 
Published: June 2012

Abstract
Exposure of cells to low doses of ionizing radiation (≤ 10 cGy) or amifostine induces pro-survival pathways that result in protection against the damaging effects of high dose ionizing radiation exposure. We have identified one such signaling pathway whose molecular mechanism involves the elevation of active manganese superoxide dismutase (SOD2) levels in the cell. SOD2 is a mitochondrial matrix protein that serves as the primary mitochondrial defense against superoxide formation. Treatment of RKO36 human colon carcinoma cells with 40 μM WR1065 or 10 cGy x-rays causes a significant increase in SOD2 activity that peaks 24 h after exposure. This increase in SOD2 activity is completely eliminated in cells subsequently exposed to 2 Gy. Following the dismutation of O2−, SOD2 is rapidly converted back into active enzyme in the case where enzyme and substrate concentrations are approximately equal. However, when substrate concentration is much greater than enzyme concentration, as is the case following exposure to 2 Gy radiation, the conversion from inactive to active enzyme occurs with much slower kinetics, taking minutes rather than seconds to occur. The protective effect of the thiol- and radiation-induced elevation in active SOD2 was examined using the endpoint of micronuclei formation as a measure of chromosomal damage. Exposure of RKO36 cells to 4 Gy results in a significant increase in the mean number of micronuclei observed. The frequency of micronuclei formation is significantly reduced when cells are treated with 40 μM WR1065 or exposed to 10 cGy 24 h prior to being irradiated with 4 Gy. No protective response is observed in cells exposed to 40 μM WR1065 30 min, 1 h or 3 h prior to two 2 Gy fractionated radiation doses separated by 24 h, or in cells exposed to 10 cGy 30 min, 3 h or 6 h before the first of two 2 Gy fractions. Treatment of cells with 40 μM WR1065 30 min, 1 h or 3 h after the first of the two 2 Gy fractions, or with 10 cGy 30 min, 3 h or 6 h after the first 2 Gy fraction also did not protect cells against the formation of micronuclei relative to cells exposed to the 2 Gy fractions alone. This work was supported by NIH/NCI grant R01 CA132998 and DOE Low Dose Program/Project Grant DE-SC0001271 (D.J.G).
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2480. doi:10.1158/1538-7445.AM2011-2480
Abstract 2526: Tyrosine 656 in topoisomerase IIβ is important for the catalytic activity
Authors: Ganapathi Mahrukh K. , Grozav Adrian G. , Willard Belinda B. , Kozuki Toshiyuki , Chikamori Kenichi , Micluta Marius A. , Petrescu Andrei-Jose , Kinter Michael , Ganapathi Ram N. 
Published: June 2012

Abstract
Topoisomerase (topo) II catalyzes topological changes in DNA. Although, both human isozymes, topo IIα and β, are phosphorylated, site-specific phosphorylation of topo IIβ is poorly characterized. Using LC-MS/MS analysis of topo IIβ, cleaved with trypsin, Arg C or cyanogen bromide (CNBr) plus trypsin we detected four +80-Da modified sites, tyrosine 656, serine 1395, threonine 1426 and serine 1545. Phosphorylation at serine 1395, threonine 1426 and serine 1545 was established based on neutral loss of H3PO4 (−98 Da) in the collision-induced dissociation (CID) spectra and on differences in 2D-phosphopeptide maps of 32P-labeled wild type (WT) and serine1395alanine or threonine1426alanine/serine1545alanine mutant topo IIβ. However, phosphorylation at tyrosine 656 could not be verified by 2D-phosphopeptide mapping of 32P-labeled WT and tyrosine656phenylalanine mutant protein or by Western blotting with phosphotyrosine-specific antibodies. Since the +80-Da modification on tyrosine 656 was observed exclusively during cleavage with CNBr and trypsin, this modification likely represented bromination, which occurred during CNBr cleavage. Re-evaluation of the CID spectra identified +78/+80-Da fragment ions (characteristic of bromination) in CID spectra of two peptides containing tyrosine 656 and tyrosine 711, confirming bromination. Interestingly, mutation of only tyrosine 656, but not serine 1395, threonine 1426 or serine 1545, decreased topo IIβ activity suggesting a functional role for tyrosine 656. Homology modeling of the region of topo IIβ (amino acids 449-1108) containing these two reactive tyrosine residues revealed that tyrosine 711 is buried, whereas tyrosine 656 is highly exposed on the surface. This region is within, or very close to the dimerization interface, which suggests that these amino acids may be critical for topo IIβ dimer formation. These results, while identifying an important tyrosine in topo IIβ, underscore the importance of careful interpretation of modifications having the same nominal mass.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2526. doi:10.1158/1538-7445.AM2011-2526
Abstract 2542: Preclinical studies of novel phosphonium salts with broad-spectrum activity
Authors: Millard Melissa , Pathania Divya , Shabaik Yumna , Taheri Laleh , Deng Jinxia , Neamati Nouri 
Published: June 2012

Abstract
Proliferation under selective pressures exerted by an unstable microenvironment, requires tumor cells employ adaptive mechanisms that confer growth advantage. Adaptation to adverse conditions results in cellular phenotypes that typify neoplastic transformation and offer unique opportunities for selective targeting of cancer cells. Agents that target tumor cell mitochondria with high selectivity hold clinical significance due to the adaptive, modulatory and essential role of this organelle in cancer cell energy production, metabolism and apoptosis. To this end, we have identified a series of novel, mitochondriotropic phosphonium salts, (TP compounds), that have shown broad-spectrum anti-cancer and anti-angiogenic activity in preclinical evaluation. A high-throughput MTT-based screen of over 10,000 drug-like small molecules for anti-proliferative activity identified the phosphonium salts TP187, 197 and 421 and numerous close analogues as having IC50 concentrations in the sub-micromolar range. TP treatment induced cell cycle arrest, lowered oxygen consumption, and increased mitochondrial superoxide production. Administered as single agents in a mouse model of human breast cancer, TP compounds significantly decreased tumor growth with no observed toxicities. Protein microarray data demonstrated significant down-regulation of integrin and growth factor mediated signaling pathways governing key processes including cancer cell survival, proliferation and tumor angiogenesis. At low micromolar concentrations, TP compounds prevented integrin-mediated cell adhesion to fibronectin and vitronectin coated substrates and tumor cell haptotaxsis on vitronectin coated boyden chambers. Similar concentrations of TP compound also prevented growth factor induced endothelial cell tube formation in 3-D culture using basement membrane extracts. Taken together, these results suggest that as mitochondria-targeted agents, TP compounds act to inhibit tumor cell proliferation and angiogenic capacity.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2542. doi:10.1158/1538-7445.AM2011-2542
Abstract 2547: NCI-60 combination screening matrix of approved anticancer drugs
Authors: Holbeck Susan L. , Collins Jerry M. , Doroshow James H. 
Published: June 2012

Abstract
Anticancer drugs are rarely curative as single agents, thus most treatment regimens utilize a combination of agents. Selection of rational combinations based upon presumed mechanisms of action is an active area of research. Nonetheless, treatment regimens may have built up over time by addition of new agents to existing standards of care. In order to establish a framework for extending our understanding combination therapy, we have initiated an additional approach: the systematic testing of all pairwise combinations of FDA-approved anticancer drugs in the NCI-60 panel of human tumor cell lines. About 100 small molecule drugs are approved for cancer treatment worldwide – testing all 5000 pairwise combinations in each of 60 cell lines will require 300,000 experiments. Combinations are tested at 3 or more concentrations of each agent, and single agents are tested on the same plates, requiring ∼ 5 million wells. To date, about 100 pairs of drugs have been tested in the NCI-60 in a pilot phase – the high-throughput phase has just begun. Some combinations of drugs, such as bortezomib combined with cladribine, show better than single agent activity in nearly all cell lines tested. Other combinations, such as doxorubicin plus lapatinib, show more restricted benefit, with some cell lines showing enhanced growth inhibition or cell kill, while in other cell lines the combination is antagonistic or identical to the more active single agent. The NCI-60 panel of cell lines has been extensively molecularly characterized, with publicly available data including gene mutation, DNA copy number, DNA methylation, and expression of mRNA, protein and microRNA. The patterns of cell line sensitivity for a particular drug combination can be used to probe these molecular characterization data, generating hypotheses about potential predictive markers and/or mechanisms of action. Probing the doxorubicin plus lapatinib patterns reveals a strong correlation with MDR activity, with high MDR expressing lines showing enhanced combination activity. The most promising combinations identified from NCI-60 testing are being tested in vivo to determine the therapeutic index. Already 2 combinations have demonstrated promising xenograft activity. The combination screening data, along with tools to analyze the data, will be made available to the public through the NCI web site.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2547. doi:10.1158/1538-7445.AM2011-2547
Abstract 2548: Chemosensitization of cancer cells by KU-0060648: A dual inhibitor of DNA-PK and PI-3K
Authors: Batey Michael A. , Munck Joanne M. , Zhao Yan , Cano Celine , Tavecchio Michele , Bardos Julia , Griffin Roger J. , Jenkins Helen , Menear Keith , Smith Graeme , Thommes Pia , Newell David R. , Martin Niall , Curtin Nicola J. 
Published: June 2012

Abstract
DNA double strand breaks (DSBs) are the most cytotoxic lesions induced by topoisomerase II poisons. Enzyme-mediated repair of DNA DSBs is a major mechanism of resistance to DNA DSB-inducing agents. Non-homologous end joining (NHEJ) is the major pathway for the repair of DSBs and requires DNA-PK activity. DNA-PK has close structural similarities to PI-3K, which promotes cell survival and proliferation and is up-regulated in many cancers. KU-0060648 is a dual inhibitor of DNA-PK and PI-3K in vitro. We investigated the therapeutic utility of KU-0060648, in models of human cancer.
KU-0060648 was investigated in a panel of human breast and colon cancer cells, it inhibited cellular DNA-PK auto-phosphorylation with IC50 values of 0.019 µM (MCF7 cells) and 0.17 µM (SW620 cells), and PI-3K-mediated AKT phosphorylation with IC50 values of 0.039 µM (MCF7 cells) and &gt;10 µM (SW620 cells). 5-day exposure to 1 µM KU-0060648 inhibited cell proliferation by &gt; 95% in MCF7 cells, but only by 55% in SW620 cells. In clonogenic survival assays, KU-0060648 increased the cytotoxicity of etoposide and doxorubicin across the panel of DNA-PKcs-proficient cells, but not in DNA-PKcs-deficient cells, thus confirming that enhanced cytotoxicity was due to DNA-PK inhibition. In mice bearing SW620 and MCF7 xenografts, concentrations of KU-0060648 that were sufficient for in vitro growth inhibition and chemosensitisation were maintained within the tumour for at least 4 hours at non-toxic doses. KU-0060648 alone delayed the growth of MCF7 xenografts and increased etoposide-induced tumour growth delay in both SW620 and MCF7 xenografts by up to 4.5-fold, without exacerbating etoposide toxicity to unacceptable levels.
The proof of principle in vitro and in vivo chemosensitisation with KU-0060648 justifies further evaluation and characterisation of dual DNA-PK and PI-3K inhibitors.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2548. doi:10.1158/1538-7445.AM2011-2548
Abstract 2551: The Nampt inhibitor MPC-9528 synergizes with DNA damaging agents
Authors: Terry-Lorenzo Ryan T. , Douce Thomas B. , Austin Harry A. , Boniface J. Jay , Cimbora Daniel M. , Fleischer Tracey C. , Carlson Robert O. 
Published: June 2012

Abstract
Background: MPC-9528 reduces cellular NAD levels and causes cell death, by blocking the NAD salvage pathway through inhibition of nicotinamide phosphoribosyltransferase (Nampt). Many DNA damaging agents also reduce cellular NAD levels, by activating the NAD consuming enzyme poly(ADP-ribose) polymerase (Parp). We hypothesized that the combination of a Nampt inhibitor and a DNA damaging agent would synergize in killing cancer cells, due to a combined effect on NAD levels through two independent mechanisms.
Methods: Cellular NAD was measured using a coupled enzymatic assay. Drug combination experiments were performed in HCT116 colon carcinoma cells, using measurement of ATP levels as a cell viability endpoint. Synergy, antagonism, or additivity was assessed using the MacSynergy II program.
Results: In HCT116 cells, saturating doses of MPC-9528 induced depletion of NAD with a half-life of 5 hours and a decrease in ATP that was delayed approximately 14 hours relative to NAD. Lower, sublethal concentrations of MPC-9528 induced partial NAD depletion without a concomitant ATP loss. At these sublethal concentrations, MPC-9528 was found to synergize with the DNA alkylating agents temozolomide and streptozotocin, which are known to activate Parp. Additionally, MPC-9528 was found to synergize with two structurally different thymidylate synthase inhibitors, 5-fluorouracil (5-FU) and raltitrexed, neither of which have been reported to activate Parp. Individually, 5-FU and raltitrexed each caused NAD depletion in HCT116 cells, which was enhanced by combination with MPC-9528. Furthermore, both 5-FU- and raltitrexed-mediated NAD depletion and synergy with MPC-9528 were completely blocked by the Parp inhibitor olaparib.
Conclusions: Parp activation induced by the alkylating agents temozolomide and streptozotocin, or by the thymidylate synthase inhibitors 5-FU and raltitrexed, is the basis for tumoricidal synergy with the Nampt inhibitor MPC-9528. This synergy is a direct consequence of the NAD depletion resulting from Parp activation coupled with the inhibition of NAD synthesis due to Nampt inhibition. These results provide a basis for clinical combination of MPC-9528 with the agents studied here or with related agents that induce Parp activation.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2551. doi:10.1158/1538-7445.AM2011-2551