bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2789: Interaction of (+)-discodermolide-Taxol hybrids with microtubules
Authors: Yang Chia-Ping H. , Sugasawa Keizo , Atasoylu Onur , Smith Amos B. , Horwitz Susan B. 
Published: August 2012

Abstract
Taxol and discodermolide are both microtubule stabilizing agents that bind to the β-tubulin subunit of microtubules. Based on our results that the hydrophobic binding pocket of β-tubulin is occupied by the Taxol side chain but not by (+)-discodermolide, and that the two drugs act synergistically in cancer cell lines, a small library of (+)-discodermolide-Taxol hybrids was synthesized (J. Med. Chem. 54:6319, 2011). Cytotoxicity assays demonstrated a 2-9-fold increase in antiproliferative activity by the hybrids compared to discodermolide in the human cancer cell lines, A549 and MCF-7. Hybrids containing a tether of 3 carbons that connect discodermolide with the Taxol side chain, exhibited the best activity. Tubulin assembly assays were performed with the two most potent hybrid molecules. Like discodermolide, these two hybrids increased tubulin assembly rapidly without a lag period. Tubulin polymerization studies using purified bovine brain tubulin demonstrated that they also had the greatest effect on the formation of polymerized microtubules. These results also were observed in intact A549 cells and in 100,000 x g supernatants prepared from these cells. We have previously shown that [3H]2-(m-azidobenzoyl)Taxol photolabels a peptide containing amino acid residues 217-231 of β-tubulin. A 5-fold molar excess of unlabeled compound inhibited the photolabeling of purified bovine brain tubulin by 94%, demonstrating the specificity of this photolabeling. Microtubule stabilizing agents (MSAs), such as Taxol, epothilone B, discodermolide and ixabepilone, each at a 5-fold molar excess, inhibited the photolabeling by 24%, 92%, 100% and 41%, respectively, indicating that discodermolide is the most potent inhibitor of the photolabeling. In contrast, two other MSAs, laulimalide and peloruside that are known to bind to a different site in β-tubulin, exhibited stimulatory effects on the photolabeling. Both drugs, at a 5-fold molar excess, increased the labeling by 30-40%. [3H]2-(m-azidobenzoyl)Taxol (0.5 - 20 µM) was used to study the kinetics of the inhibitory effects of the hybrid molecules on photoaffinity labeling of tubulin. Discodermolide-Taxol hybrids inhibited the photolabeling of bovine brain tubulin in a dose dependent manner. The concentrations that inhibited by 50% were lowest for the two most potent hybrid molecules. Therefore, the tubulin polymerization activity and the binding affinity of the hybrids to β-tubulin correlated with their antiproliferative activity. Other biological properties of the discodermolide-Taxol hybrids including senescence and antitumor activity are being evaluated.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2789. doi:1538-7445.AM2012-2789
Abstract 2790: Localization of the binding site for Peloruside A and Laulimalide on beta-tubulin by physical and biological means
Authors: Begaye Adrian , Trostel Shana , Taylor Richard E. , Schriemer David C. , Sackett Dan L. 
Published: August 2012

Abstract
Peloruside A (Pel) and laulimalide (Laul) are microtubule-stabilizing natural products that were discovered recently compared to more established agents such as the taxanes and the epothilones. The activities of Pel and Laul are synergistic with taxanes or epothilones but not with each other, indicating separate binding sites and distinct mechanisms for Pel and Laul compared to taxanes and epothilones. Hence the location and nature of the Pel / Laul binding site is of interest. We have identified this site by a physical method (mass spec H-D footprinting) and a biological one: isolating Pel-resistant mutants of human ovarian carcinoma cells (A2780 (1A9)). Four Pel-resistant lines were obtained with single-base mutations in class I β-tubulin which resulted in the following substitutions: R306H, Y340S, N337D, and A296S in various combinations. The mutations localize to the peptides identified by the mass spec method, and center on a cleft in which modeling indicates that the Pel and Laul side chains dock. The site is accessible from the outside of the microtubule and does not overlap the Taxol site on β-tubulin. The Pel resistant lines are cross resistant to Laul, but not to any other microtubule stabilizing drug, and show no cross-sensitivity to microtubule destabilizing drugs.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2790. doi:1538-7445.AM2012-2790
Abstract 2798: Cytotoxic and cystostatic properties of rapamycin are due to differential effects on the phosphorylation of mTORC1 substrates S6 kinase and 4E-BP1
Authors: Yellen Paige , Chatterjee Amrita , Saqcena Mahesh , Salloum Darin , Preda Angela , Rodrik-Outmezguine Vanessa , Feng Jiangnan , Xu Limei , Foster David A. 
Published: August 2012

Abstract
The mammalian target of rapamycin (mTOR) has been widely implicated in signals that promote cell cycle progression and survival in cancer cells. Rapamycin, which inhibits mTOR with high specificity, has consequently attracted much attention as an anti-cancer therapy. Used clinically at nano-molar concentrations, rapamycin suppresses phosphorylation of mTOR complex 1 (mTORC1) substrate S6 kinase and has been considered a cytostatic drug. However, we have reported that higher (micro-molar) doses are required for complete cell cycle arrest. Such high doses suppress phosphorylation of another mTORC1 substrate, eukaryotic initiation factor 4E (eIF4E) binding protein-1 (4E-BP1). In this state, eIF4E is sequestered and unable to facilitate mRNA translation. Dual ablation of S6 kinase and eIF4e resulted in a larger increase in G1 content than by ablation of S6 kinase alone. This confirmed the complete cytostatic effect of high-dose rapamycin. We also demonstrated that the differential dose effects of rapamycin correlate with partial and complete dissociation of Raptor from mTORC1 at low and high doses, respectively. Therefore, high-dose rapamycin ensures complete non-functionality of mTORC1. Interestingly, in the absence of serum, high dose rapamycin induces apoptosis and dual inhibition of S6 kinase and eIF4e does not prevent it. We have established that the differential cytostatic and cytotoxic effects of rapamycin are due to intact TGFb signaling. In serum, TGFb is activated upon low dose rapamycin (suppression of of S6 kinase phosphorylation). The lack of TGFb in the absence of serum allows cells to progress through the cell cycle; at high rapamycin doses, the inactivity of eIF4e results in cell death. This study reveals the mechanism for both cytostatic and cytotoxic properties of rapmaycin.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2798. doi:1538-7445.AM2012-2798
Abstract 2803: GSK3 plays a crucial role in determining cell response to mTOR inhibitors
Authors: Koo Junghui , Yue Ping , Tao Hui , Ramalingam Suresh S. , Khuri Fadlo R. , Sun Shi-Yong 
Published: August 2012

Abstract
The mammalian target of rapamycin (mTOR) exerts a critical role in the regulation of cell growth and cell survival, primarily through forming two complexes with raptor (mTOR complex 1; mTORC1) or rictor (mTOR complex 2; mTORC2). The mTOR axis is dysregulated in many types of human cancers, thus becoming an attractive cancer therapeutic target. Accordingly, mTOR inhibitors including the conventional allosteric inhibitors (rapamycin and its analogs; rapalogs) and novel mTOR kinase inhibitors (e.g., INK128) have been developed. However, single-agent activity of these inhibitors in the majority of cancer types is limited or modest at best. Thus, it is crucial to identify determinants that impact cell response to mTOR-targeted cancer therapy. In this study, we found that inhibition of GSK3 with both a small molecule inhibitor (e.g., SB216765) and gene knockdown substantially antagonized the suppressive effects of mTOR inhibitors (e.g., rapamycin and INK128) on the growth of cancer cells, including G1 arrest. In agreement, activation of GSK3 by expressing a constitutively activated form of GSK3[[Unsupported Character - Symbol Font &#61538;]] sensitized cells to mTOR inhibitors. Moreover, higher basal levels of GSK3 activity from 14 lung cancer cell lines were significantly associated with better cell responses to both rapamycin and INK128 (P &lt; 0.05). These data together indicate that GSK3 plays a critical role in determining cell response to mTOR inhibitors. Interestingly, GSK3 inhibition did not alter the effects of mTOR inhibitors on suppression of mTOR signaling and cap-dependent translation, but rescued downregulation of cyclin D1 and c-Myc caused by mTOR inhibitors, suggesting that mTOR inhibitors decrease cyclin D1 and c-Myc levels independent of inhibition of mTOR-mediated protein translation. Instead, we found that inhibition of mTOR (e.g., by INK128) decreased the stabilities of both cyclin D1 and c-Myc. Moreover, inhibition of proteasome (e.g., with MG132) prevented cyclin D1 and c-Myc reduction by INK128. Hence it is apparent that mTOR inhibition facilitates cyclin D1 and c-Myc degradation, leading to reduction of cyclin D1 and c-Myc. Together, these findings suggest a novel mechanism by which mTOR signaling positively regulates the stability of cyclin D1 and c-Myc. Our current findings thus warrant further investigation of the potential impact of GSK3 inhibition on the efficacy of mTOR inhibitors in the clinic. (This study was supported by the Georgia Cancer Coalition Distinguished Cancer Scholar award and NIH/NCI R01 CA118450. SS Ramalingam, FR Khuri and SY Sun are Georgia Cancer Coalition Distinguished Cancer Scholars)
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2803. doi:1538-7445.AM2012-2803
Abstract 2825: Regorafenib and Sorafenib induce reversible quiescence in human hepatoma cells
Authors: Carr Brian I. , Messa Caterina , Cavallini Aldo , D'Allesandro Rosalba , Refolo Maria Grazia , Lippolis Catia , Tafaro Angela 
Published: August 2012

Abstract
The actions of the multikinase inhibitor Sorafenib (Soraf) and its more potent fluoro-analog, Regorafenib (Regoraf) were examined on human Hep3B and PLC/PRF/5 hepatoma cells in vitro. IC50 was 7.5 µM for Soraf and 5.0 µM for Regoraf. Both agents required 48 hr. exposure to cells for maximal growth inhibitory effects measured by MTT at 96 hr. Evidence was found for Regoraf-induced apoptosis (max. 25% by FACS at 48 hr. and 45% decrease in Bcl-2 and BcL-xL), non-classical autophagy (50% increase in Beclin-1, without change in LC3 I/II ratio) and cell signaling changes (decreased p-ERK, increased p-JNK and p-Jun). In addition to growth inhibition, quiescence was observed for up to 6 wk. in the presence of prolonged drug exposure. Furthermore, after 1 wk. of drug-mediated inhibition, removal of either Soraf or Regoraf resulted in normal cell proliferation (recovery), unlike treatment with TGFβ 1µM or doxorubicin 0.1µM for 48 hr., after which no recovery was seen. The data are consistent with multiple mechanisms and pathways being altered during Regoraf-mediated growth inhibition and the induction of both quiescence and recovery after withdrawal of either Soraf or Regoraf, which have clinical implications.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2825. doi:1538-7445.AM2012-2825
Abstract 2827: In vivo effects of ICA-1 on breast cancer and glioma xenografts
Authors: Acevedo-Duncan Mildred E. 
Published: August 2012

Abstract
High grade breast cancer and gliomas are highly lethal tumors for which novel therapies are necessary. PKC-iota (PKC-α), an atypical protein kinase C isoform confers resistance to drug-induced apoptosis in cancer cells (J. Biol. Chem. 272; 44: 27521-27524). This research focuses on the in-vivo effects of the novel PKC-α inhibitor [1H-imidazole-4-carboxamide, 5-amino-1-[2,3-dihydroxy-4-[(phosphonooxy) methyl] cyclopentyl]-[1R-(1α, 2α, 3 β, 4 α)] (ICA-1; The Inter. J. Biochem. & Cell Biol. 43:784-794) on breast cancer and glioma xenografts. ICA-1 targets a unique sequence (amino acid residues 469-475) in the catalytic domain of PKC-α. The breast cancer xenograft study evaluated 12 athymic nude mice while the glioma xenograft study was comprised of 6 female athymic nude mice. The breast cancer xenografts were divided into saline control (n= 4) and xenografts injected with ICA-1 (20mg/kg; 5 μM; every other day, n = 8). The six glioma nude mice were divided into two groups consisting of saline controls (n = 3) and xenografts injected with ICA-1(80 mg/kg; 20 μM; every other day) when the tumor reached 100 mm3 on day 5 post implantation (n = 3). MDA-MB-468 breast cancer cells were injected subcutaneously (2 x106 cells/ flank in 0.2 ml PBS) while the human glioblastoma cell line U-87 MG was also injected into different mice subcutaneously in the right flank (1x106 cells/flank in 0.1 ml PBS). Tumor volume was calculated using formula: length x width x width x ½. Results showed that ICA-1 prevented glioma tumor growth even after stopping dosing at day 9 and continuing to monitor tumor growth for an additional nine days. Glioma tumor volume in these ICA-1 treated mice decreased by 51% compared to controls. ICA-1 was also effective in decreasing breast cancer xenograft growth by 50%. The weight of either ICA-1 treated breast cancer or glioma xenograft mice did not decrease compared to controls. These results indicate that ICA-1 is effective in preventing the growth of breast cancer and glioma xenografts. Future studies will establish toxicity data and optimize the dose and frequency of ICA-1 treatment for potential anti-PKC-α therapy.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2827. doi:1538-7445.AM2012-2827
Abstract 2828: Characterization of protein substrates of PSA: effect of PSA stimulating peptides
Authors: Mattsson Johanna , Hekim Can , Närvänen Ale , Jonsson Magnus , Malm Johan , Stenman Ulf-Håkan , Koistinen Hannu 
Published: August 2012

Abstract
Increased proteolytic activity is associated with cancer, where proteases play a major role in tumor spread and formation of metastases. However, proteases may also inhibit tumor growth. The prostate produces several proteases, the most abundant one being prostate-specific antigen (PSA or kallikrein-related peptidase-3, KLK3). The role of PSA in the prostate, and in particular in prostate cancer, is not well known. However, several functions have been proposed, most of which are based on the protein substrates, which PSA cleaves in vitro. These include both tumor growth promoting and inhibiting activities, e.g., antiangiogenic activity of PSA. We have previously used phage display technology to develop peptides, the synthetic analogs of which stimulate the activity of PSA. These peptides are useful for studying the significance of PSA-activity and potentially for prostate cancer treatment. We analyzed the cleavage of different protein substrates of PSA and found that physiological substrates, semenogelin-1 and −2, are cleaved much more efficiently than other substrates, such as IGFBP-3, fibronectin and galectin-3. The peptides increased the proteolytic activity of PSA towards these protein substrates, but the extent of stimulation and the relative efficiency of peptides were different than with small peptide substrates. We conclude that the peptides can be used to stimulate the activity of PSA towards natural protein substrates. Thus, they may be potential lead molecules for drug development. As most of the studied protein substrates are cleaved with very low efficiency, their relevance as PSA substrates is questionable, especially as prostate produces several other highly active proteases, including several kallikreins and trypsin. As compared to other substrates, semenogelins are very efficiently cleaved by PSA, highlighting the substrate specificity of PSA.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2828. doi:1538-7445.AM2012-2828
Abstract 2831: Studies on the mechanistic basis of the anticancer activity of 2,4-disulfonyl-PBN (OKN-007)
Authors: Floyd Robert A. , Chandru Hema , Stewart Charles , Towner Rheal A. 
Published: August 2012

Abstract
Sulfatase 2 (Sulf2) is a protein which resides in the extracellular matrix of cancer cells and enzymatically removes sulfate from the 6-O-sulfate esters of heparin. Several tumors have been shown to be enriched in Sulf2 in comparison to normal tissues where it is either absent or present at very low levels. The action of Sulf2 alters growth factor binding to the extracellular matrix of cells and has been shown to be important in the development of many cancers including breast, lung, liver, colon, and pancreas. Sulf2 mobilizes fibroblast growth factors (FGFs), vascular endothelial growth factor (VEGF) and stromal derived growth factor-1 (SDF-1) bound to heparin. We found that OKN-007 acts to weakly inhibit the aryl sulfatase activity of Sulf2 acting on the substrate 4-methylumbelliferyl-sulfate (4-MUS) and to more effectively inhibit the enzymatic activity of Sulf2 when it acts upon its natural substrate the 6-O-sulfate ester of heparin. The Sulf2 enzymatic activity was potently inhibited by suramin, a compound that has 6 phenyl-sulfonyl groups as part of its chemical structure and has been shown to have anti-cancer activity. Utilizing the natural substrate we have shown that other sulfonyl-phenyl compounds act to suppress the activity of Sulf2. We have conducted preliminary studies to see if OKN-007 has anti-cancer activity in a breast cancer mouse xenograph model. Balb/c female ovariectomized Estradiol pellet-implanted nude mice were implanted with MCF-7 breast cancer cells and OKN-007 was administered at 250mg/kg/day in the drinking water. The experiment was terminated at week 5 at which time the data showed that OKN-007 decreased the average tumor volume by 33%. OKN-007 has been shown to have anti-cancer activity in the rat C6 model of glioma. The anti-cancer mechanism of action of OKN-007 is still unknown. Recently we have explored the potential of OKN-007 to alter cancer cell migration in a gradient involving the chemokine SDF-1 and its cellular receptor CXCR4. The CXCL4/SDF-1 gradient is considered to be important in the metastasis of primary cancers. Results with rat C6 glioma cells, U87MG human glioma cells as well as MCF-7 breast cancer cells indicate that OKN-007 at low concentrations inhibits cancer migration in a CXCR4/SDF-1 gradient. These observations need to be explored in more depth utilizing animal models of cancer metastasis. Research supported in part by US Army Concept Grant W81XWH-09-1-0352. Dr. Floyd holds the Merrick Foundation Chair in Aging Research.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2831. doi:1538-7445.AM2012-2831
Abstract 2838: High-throughput genotoxicity screening unlocks chemotherapeutic potential of antioxidants
Authors: Myung Kyungjae 
Published: August 2012

Abstract
Human ATAD5 is a biomarker for identifying genotoxic compounds because ATAD5 protein levels increase post-transcriptionally in response to DNA damage. We screened over 4,000 compounds with a novel, cell-based quantitative high-throughput ATAD5-luciferase assay detecting genotoxic compounds. We identified 22 antioxidants, including resveratrol, genistein, and baicalein, that are currently used or investigated for the treatment of cardiovascular disease, type 2 diabetes, osteopenia, osteoporosis, and chronic hepatitis, and for anti-aging. Treatment of dividing cells with these compounds induced DNA damage and resulted in cell death. Despite their genotoxic effects, resveratrol, genistein, and baicalein did not cause mutagenesis, which is a major side effect of conventional anti-cancer drugs. Furthermore, resveratrol and genistein killed multi-drug resistant cancer cells. We therefore propose that resveratrol, genistein, and baicalein are attractive candidates for improved chemotherapeutic agents.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2838. doi:1538-7445.AM2012-2838