bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2489: Dramatically increased microtubule shortening resulting from overexpression of β5-tubulin is reversed by paclitaxel
Authors: Bhattacharya Rajat , Yang Hailing , Cabral Fernando 
Published: February 2011

Abstract
Vertebrate cells express 6-7 isotypes of both α and β-tubulin, all of which coassemble into microtubules. Our previous studies demonstrated that β3 and β5 (but not β1, β2, and β4b) tubulin overexpression destabilizes microtubules, inhibits cell growth, and confers paclitaxel resistance (Blade, K., et al. (1999). J Cell Sci 112: 2213-21; Bhattacharya, R. and F. Cabral (2004). Mol Biol Cell 15: 3123-31; Hari, M., et al. (2003). Cell Motil Cytoskeleton 56: 45-56.). Overexpression of β3 does not appear to significantly alter microtubule dynamics, but dynamic behavior is relatively resistant to suppression by paclitaxel (Kamath, K., et al. (2005). J Biol Chem 280: 12902-7.). We now report the effects of β5 overexpression on microtubule dynamics. Microtubules were visualized in wild type (WT) or β5 overexpressing CHO cells using eGPF-MAP4. Growth and shrinkage of individual microtubules were measured using ImageJ and dynamic parameters were calculated by analyzing life history plots. We found that microtubules with high β5 content had significantly increased shortening rates and very long depolymerization distances compared to wild type. Addition of paclitaxel at a concentration that rescues cell growth, completely reversed these effects; but the dynamic parameters in such microtubules were significantly different compared to WT microtubules and resembled the inhibited microtubule dynamics of WT cells treated with paclitaxel. We conclude that suppression of microtubule dynamics in presence of paclitaxel is insufficient to explain why β5 overexpressing cells become resistant to the drug.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2489.
Abstract 2492: Microtubule-interacting agents increase Class I HLA and HLA-A2 molecules surface expression in ovarian cancer cells
Authors: Pellicciotta Ilenia , Goldberg Gary L. , Shahabi Shohreh 
Published: February 2011

Abstract
Objective: Ovarian cancer is the leading cause of death from gynecologic cancers in the United States. Standard first line therapy for ovarian cancer includes paclitaxel and platinum based agents. Epothilone B, Taxol and Vinblastin belong to a family of anti-neoplastic agents that interfere with microtubules and arrest cells in the G2/M phase of the cell cycle. Little is known about the effect of these drugs on the immune response to tumors. There is compelling evidence that cancer cells use multiple strategies to evade immune recognition. One of these mechanisms is the down-regulation of human leukocyte antigen (HLA) Class I molecule expression on the tumor cell surface, allowing the cancer cell to escape immune recognition and destruction.
Data will be presented to illustrate the effect of microtubule affecting agents on HLA class I molecule expression in ovarian cancer cells. The effect on the expression of HLA-A2, the most common class I allele in the Caucasian population, has been evaluated as well. We also investigated the relationship between surface HLA expression and transcriptional modification of HLA induced by the drugs.
Methods: IC50 was determined for each compound based on a 72 h cytotoxicity assay, using ovarian cancer cell line Hey. Cells were treated with different concentrations ranging from 1-fold IC50 to 100-fold IC50, and incubated at 37°C for 24 h, 48 h and 72 h. Cell surface expression of HLA class I molecules and HLA-A2 was examined by flow cytometry, using anti-HLA-A,B,C antibody (G46-2.6 clone) and HLA-A2 (BB7.2 clone). RT-PCR and real time PCR were used to amplify HLA genes, using Platinum Taq DNA Polymerase and Power SYBR Green master mix respectively.
Results: Low dose Epothilone B, Taxol and Vinblastin (10-fold IC50) increased cell surface expression of HLA Class I up to four-fold in Hey ovarian cancer cells. HLA-A2 molecules were increased up to 2-fold. The increase of HLA Class I molecule expression was dose- and time-dependent.
Conclusions: Nanomolar concentrations of microtubule-interacting agents increase the expression of HLA class I molecules in Hey ovarian cancer cells. Our data suggest that low doses of microtubule-interacting agents can mediate modulation of surface HLA expression and may enhance immune recognition of tumor cells.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2492.
Abstract 2493: Inhibition of phosphoinositide 3-kinase suppressed growth of cancer cells with PIK3CA mutations or loss of PTEN expression via G0/G1 arrest of cell cycle but not apoptosis
Authors: Dan Shingo , Okamura Mutsumi , Yoshimi Hisashi , Mukai Yumiko , Yamazaki Kanami , Inoue Yasumichi , Hanyu Aki , Imamura Takeshi , Sakaue-Sawano Asako , Miyawaki Atsushi , Yamori Takao 
Published: February 2011

Abstract
Background: The phosphoinositide 3-kinase (PI3K) pathway is frequently activated in cancer by gain-of-function mutation of PIK3CA and loss of PTEN expression, and mediates growth- and anti-apoptotic signals. Therefore, PI3K is considered as a promising therapeutic target to inhibit growth and to induce apoptosis in such cancers. We previously developed a novel PI3K-specific inhibitor ZSTK474 with antitumor efficacy (Yaguchi et al, J. Natl. Cancer Inst. 98: 545-56, 2006; Kong and Yamori, Curr. Med. Chem. 16: 2839-54, 2009). In this study, we have examined the cellular mechanism by which ZSTK474 exerts its antitumor efficacy in human cancer cells with or without PIK3CA/PTEN aberrations.
Methods: We examined the antitumor effect of ZSTK474 on various human cancer cell lines with or without PIK3CA/PTEN aberration in vitro and in vivo. Protein expression and apoptosis in ZSTK474-treated and untreated tumor sections were analyzed by immunohistochemistry and TUNEL assay, respectively. Analysis of cell cycle in vitro was determined by flow cytometry and by Fucci (Fluorescent Ubiquitination-based Cell Cycle Indicator) system introduced to cancer cells. Induction of apoptosis in vitro was estimated by caspase activation using a substrate cleavage assay and by detection of subdiploid cells using flow cytometry.
Results: In vivo, ZSTK474 effectively inhibited the growth of human tumor xenograft derived from a PTEN-null prostate cancer cell line PC3. In parallel, ZSTK474 treatment suppressed the expression of phospho-Akt, suggesting effective PI3K inhibition, and also suppressed the expression of nuclear cyclin D1 and Ki67, both of which are hallmarks of proliferation. However, ZSTK474 treatment did not increase TUNEL-positive apoptotic cells. Similar result was obtained in another PTEN-negative cell line KM-12 and three PIK3CA-mutated cell lines HCT-15 (E545K), MKN1 (E545K) and SK-OV3 (H1047R). In vitro, ZSTK474 induced marked G0/G1 arrest accompanied by a decrease of nuclear cyclin D1, induction of p27kip1 and p15ink4b, and hypophosphorylation of pRB in PC-3 cells. However, ZSTK474 did not increase the subdiploid cells or activate caspase, both of which are hallmarks of apoptosis. Similar result was obtained other cell lines with or without PIK3CA /PTEN aberrations.
Conclusion: These results clearly indicated that ZSTK474 did not induce apoptosis but rather induced strong G0/G1 arrest in cancer cells with or without PIK3CA/PTEN aberrations, which might cause its therapeutic efficacy.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2493.
Abstract 2510: Efficacy of the Chk1 inhibitor SCH900776 at abrogating cell cycle arrest and enhancing DNA damage-induced cytotoxicity: Comparison with UCN-01
Authors: Eastman Alan , Montano Ryan E. , Garner Kristen M. , Chung Injae , Parry David A. 
Published: February 2011

Abstract
Many anticancer agents damage DNA and arrest cell cycle progression primarily in S or G2 phase of the cell cycle depending on drug concentration. Previous studies with the topoisomerase I inhibitor SN38 have demonstrated the efficacy of the Chk1 inhibitor UCN-01 to overcome arrest forcing cells through S, G2 and lethal mitosis. UCN-01 was limited in clinical trials by high plasma protein binding; as a consequence many alternate Chk1 inhibitors have now been developed. SCH900776 is a novel Chk1 inhibitor entering Phase II clinical trials. SCH900776 inhibits Chk1 and overcomes SN38-mediated S and G2 arrest at 300 nM in several carcinoma cell lines which is comparable to UCN-01 at 50 nM. While both Chk1 inhibitors accelerated the rate of cell killing induced by SN38, neither enhanced the overall cell killing. Similarly, no overall sensitization to cisplatin was observed. In contrast, both Chk1 inhibitors induced dramatic sensitization of cells to antimetabolite-induced damage. For example, inhibition of Chk1 sensitized MDA-MB-231 cells to hydroxyurea with the 50% growth inhibitory concentration decreasing from 3 mM to 30 µM, a 100 fold sensitization. Importantly, concentrations of hydroxyurea that exhibited no activation of a checkpoint and no growth inhibition alone were sensitized by inhibition of Chk1. SCH900776 also induced a 50-fold sensitization to cytarabine, 10 fold sensitization to gemcitabine, but no sensitization to 5-fluorouracil. Hence, this sensitization does not extend to all antimetabolites. The 100-fold sensitization to hydroxyurea appeared to require complete inhibition of Chk1 (2 µM 776), although 10-fold sensitization to hydroxyurea was still observed at 200 nM SCH900776. In an MDA-MB-231 derivative expressing shRNA that resulted in almost undetectable levels of Chk1, the full level of sensitization to hydroxyurea could be achieved at 200 nM SCH900776 demonstrating that the response of tumors may vary with the endogenous level of Chk1. We are currently comparing the differential response of a panel of carcinoma cell lines and find some that are sensitized to hydroxyurea up to 100-fold at 200 nM SCH900776, although there appear to be determinants other than the Chk1 levels. These results can be extrapolated to suggest that marked differences in efficacy of SCH900776 can be expected in patients. It will be important to define the parameters of response as these may facilitate selection of patients most likely to respond to combination therapy with Chk1 inhibitors.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2510.
Abstract 2512: Epothilone B enhances surface EpCAM expression in ovarian cancer cells
Authors: Shahabi Shohreh , Yang Chia-Ping H. , Goldberg Gary , Horwitz Susan B. 
Published: February 2011

Abstract
OBJECTIVES
Epothilone B (EpoB), like Taxol, induces tubulin polymerization and microtubule stabilization resulting in an inhibition of microtubule dynamic instability. The drug is presently being evaluated in phase III clinical trials. An EpoB analog Ixabepilone, has been approved by the FDA for the treatment of metastatic breast cancer. Epithelial cell adhesion antigen (EpCAM) expression is significantly higher in epithelial ovarian cancer cells compared to normal cells.
METHODS
We used biochemical methods, immunofluorescence and flow cytometry to identify EpCAM expression on the surface of the ovarian cancer cell line, Hey, after exposure to EpoB. We also investigated the relationship between EpoB-mediated surface EpCAM expression and EpoB-induced tubulin acetylation in Hey cells.
RESULTS
We investigated the effect of EpoB and other microtubule-interacting agents on surface EpCAM expression and found that nanomolar concentrations of EpoB, Taxol, discodermolide or vinblastine caused a marked increase in surface EpCAM expression in an ovarian cancer cell line, Hey. Alpha-tubulin acetylation, a surrogate marker for stable microtubules, was increased following treatment with Taxol, EpoB and discodermolide, but not with vinblastine, indicating that drug-enhanced surface EpCAM expression does not correlate with tubulin acetylation or stabilization. Unexpectedly, EpoB did not have a significant effect on EpCAM mRNA expression, nor did it alter the level of total cellular EpCAM in the human ovarian cancer cell line.
CONCLUSIONS
Our results suggest that disruption of the microtubule cytoskeleton is associated with the redistribution of cell surface antigens in ovarian cancer cells. The increase in cell surface EpCAM antigen density may facilitate the antibody targeting of EpCAM-positive ovarian cancer cells.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2512.
Abstract 2518: TAK-733 is a Potent and Selective Inhibitor of Mammalian MEK Kinases Capable of Inducing Apoptosis in BRAF Driven Cells Both in vitro and in vivo
Authors: Fabrey Robyn , Shawn O'Connell , Tsuchiya Shuntarou , Hori Akira , Vincent Patrick 
Published: February 2011

Abstract
Mutations in BRAF a serine/threonine protein kinase are frequently observed in human cancers. A valine to glutamic acid mutation at amino acid position 600 accounts for nearly 80% of all the activating mutations found for this kinase. This mutation (V600E) forces BRAF to become constitutively active and phosphorylate its substrates regardless of upstream signaling. Numerous cancers in tissues such as skin, colon, thyroid, and ovary have been attributed to uncontrolled proliferation driven by this mutation. TAK-733 represents a novel and distinct chemotype which is capable of allosteric inhibition of the BRAF substrates MEK-1 and MEK-2 at low nanomolar concentrations. Viability assays in established human cancer cell lines which bear the BRAF V600E mutation demonstrate this compound was also capable of lowering NADH levels with single digit nanomolar EC50s. Loss of NADH production can be attributed to the induction of programmed cell death pathways involving Caspases 3 and 7. Induction of these apoptosis markers was confirmed in vitro by a Caspase-GLO assay. TAK-733 induces apoptosis more potently in COLO 205 (BRAF V600E) human colo-rectal carcinoma cells when compared to other MEK inhibitors. Pharmacodynamic analysis of COLO 205 tumor bearing mice confirmed TAK-733, unlike other MEK inhibitors tested, is capable of inducing apoptosis 36 hours after a single oral administration. To determine whether the anti-tumor effect of TAK-733 is associated with apoptosis, A375 (BRAF V600E) human melanoma tumors were harvested at sacrifice and protein extracted to determine cleavage products of PARP. A single oral treatment with 1, 10, and 30 mg/kg TAK-733 increased protein expression of cleaved PARP in a dose and time dependent manner. Elevated cleaved PARP protein expression was detected as early as 0.5-hours in tumors following 30 mg/kg dose and detectable at all groups by 4-hours. The increase cleaved PARP protein levels persisted for at least 24-hours and returned to control expression levels by 48-hours. Daily oral administration of 1, 10, and 30 mg/kg/day TAK-733 for 14 days potently inhibited tumor growth resulting in tumor growth delay of 3.4, 10.8, and 26.6 days in A375 cell implanted mice. A 60% partial regression response rate (tumor volume reduced by more than 50% of initial volume) was observed in mice that received 30 mg/kg/day TAK-733. These data suggest a possible explanation as to why TAK-733 is capable of inducing regressions in COLO 205 and A375 tumor growth inhibition studies, and may represent a differentiation point from other MEK inhibitors currently in clinical trials.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2518.
Abstract 2522: Identification and characterization of new highly selective and potent BRAF inhibitors
Authors: Pulici Maurizio , Amboldi Nadia , Biondaro Sonia , Caprera Francesco , Casale Elena , Gasparri Fabio , Leone Antonella , Lupi Rosita , Marchionni Chiara , Modugno Michele , Pastori Wilma , Traquandi Gabriella , Zuccotto Fabio , Colotta Francesco , Donati Daniele , Felder Eduard R. , Galvani Arturo , Isacchi Antonella , Pesenti Enrico , Ciomei Marina 
Published: February 2011

Abstract
Aberrant activation of the MAPK-mediated pathway components, RAF-MEK-ERK, is frequently found in human cancers and clearly contributes to oncogenesis. In particular, one of the three isoforms of RAF, BRAF, presents activating somatic mutations in 70% of melanomas, 50% of thyroid cancers, 10% of colon and 20% ovarian carcinomas. The most common BRAF mutation, substitution of glutamic acid for valine at position 600 within the activation segment of the kinase domain, accounts for 90% of mutated BRAF cases, and results in elevated kinase activity with consequent enhanced promotion of cell survival and proliferation. Here we describe the in vitro and in vivo properties of a novel class of potent and selective BRAF inhibitors. Starting from a series of arylpyrazole derivatives that were found to be active against wild-type and mutated BRAF, an expansion and optimization program was undertaken. This led to the identification of both inhibitors of the active conformation and inhibitors of the inactive conformation of the enzyme, as confirmed by co-crystallography studies. Among the former category, a sub-series endowed with high potency and selectivity was identified, with compounds possessing low nM affinity for BRAFV600E and negligible cross-reactivity against a panel of 44 kinases. Members of this sub-series inhibited 72-hour proliferation of cell lines harboring the BRAFV600E mutation with IC50s below 100 nM and with greater than 100-fold selectivity compared to lines with wild-type BRAF. Consistent with this observation, inhibition of the MAPK signal transduction pathway was highly selective for cell lines with mutated BRAF. Biochemical profile, potency in cell proliferation assays, and cellular mechanism of action compared favorably among the sub-series to a reference BRAF inhibitor, PLX-4720, tested in parallel. The most potent compounds (e.g. NMS-P730 and NMS-P383) were selected for in vivo evaluation. In vivo, potent tumor growth inhibition was observed in the A375 xenograft model following oral administration, with no overt toxicity, and with corresponding modulation of the MAPK pathway, consistent with expected mechanism of action. Selection of candidates most suitable for further development is underway.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2522.
Abstract 2527: Potent, highly selective peptidomimetic prodrugs targeting the SH2 domain of Stat3 decrease vasculogenic mimicry, invasion, and anchorage independent growth of cancer cells
Authors: Mandal Pijus K. , Liao Warren S. , Gao Fengqin , Robertson Fredika M. , Thudi Nanda K. , Ekmekcioglu Suhendan , Chattopadhyay Chandrani , Ren Zhiyong , Chen Xiaomin , Lu Zhen , Bast Robert C. , Ramesh Rajagopal , McMurray John S. 
Published: February 2011

Abstract
Signal transducer and activator of transcription 3 (Stat3) transmits signals from IL-6 family cytokines, EGF and VEGF. Stat3 is constitutively activated in lung, head and neck, breast, and prostate cancers, AML and other malignancies, providing a target for cancer drug design. To uncouple Stat3 from its roles in proliferation, survival, angiogenesis, and invasion, we are targeting its SH2 domain with phosphopeptide mimetics derived from the recognition sequence, pTyr-Leu-Pro-Gln. Molecular modeling indicated that a methyl group attached to the β-position of a pTyr mimic would enhance affinity due to hydrophobic contact. This modification increased affinity 2-3 fold in a series of peptidomimetics based on pCinn-Xxx-Yyy-Gln-NHBn (pCinn = 4-phosphorylcinnamic acid), resulting in IC50 values of 35 − 112 nM in a biochemical fluorescence polarization assay. Conversion of these to bis-pivaloyloxymethyl (POM) protected difluoromethylphosphonate prodrugs resulted in complete inhibition of the phosphorylation of Tyr705 of Stat3 at concentrations of 0.5 − 1 μM in breast, ovarian, and melanoma cells. Prodrugs were selective for Stat3 over other SH2 domain-containing proteins such as Stat1, Stat5, Src, and PI3K p85. Quantitative RT-PCR showed that prodrugs inhibited Stat3-targeted gene expression. Prodrugs were not cytotoxic to cells grown in 2D cultures on plastic dishes. However, potent inhibition of Stat3-driven processes such as vasculogenic mimicry, invasion, and anchorage independent growth in soft agar was observed. Conclusions: 1. peptidomimetic prodrugs are highly potent and selective inhibitors of Stat3; 2. cultured tumor cells do not depend on phosphorylation of Tyr705 of Stat3 for survival; 3. highly selective inhibitors of Stat3 phosphorylation are likely to be effective antitumor agents due to inhibition of invasion and angiogenesis.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2527.