bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 1070: Circadian transcriptional factor Period 2 modulates cyclin B1 expression
Authors: Yang Jianhua , Finkielstein Carla V. 
Published: February 2011

Abstract
The proper timing of cell division is a major factor contributing to the regulation of normal growth and emerges as a fundamental process in the development of most cancers. The existence in most, if not all, living organisms of many behavioral and physiological events that occur at well-defined and controlled times argues for the presence of time-keeping systems that allow them to adapt to cyclic changes in environmental conditions. Disruption of circadian rhythm has recently emerged as a new potential risk factor in the development of cancer, pointing to the core gene period 2 (per2) as a tumor suppressor. However, it remains unclear how the circadian network regulates tumor suppression. In the present study, we use cDNA microarray analysis to identify Per2 target genes following siRNA knock-down expression of Per2 in mouse hepatocytes AML12 cells. We identified cyclin B1, a key G2/M regulator of the cell cycle, as a downstream target gene that is negatively regulated by Per2 under normal conditions. Quantitative real-time PCR confirmed our observations by showing cyclin B1 expression is enhanced under Per2 knock-down condition. Accordingly, Bmal1 expression, a target gene of Per2, was specifically augmented under Per2 over-expression conditions. Further experiments focused in characterizing the regulation of the human cyclin B1 promoter by Per2 using luciferase reporter assays. Results show cyclin B1 reporter activity is enhanced in siPer2 transfected cells compared to control scrambled siRNA. Promoter analysis defined the region comprising −484 to −284 of human cyclin B1 promoter containing response elements for gene trans-activation while the region between −284-1 is mainly responsible for Per2 regulation. Our results show the canonical E-box between −284-1 is not required for Per2 regulation of cyclin B1, suggesting non-canonical E-boxes might be directly responsible for Per2-mediated expression. FACS analysis revealed that siPer2 treated cells exhibit a reduced G2/M phase with correspondingly higher cyclin B1 protein levels and reduced Tyr-15-cdc2 phosphorylation compared to scrambled siRNA treated cells. Our previous results show Per2 stability is directly controlled by the endogenous levels of heme whose endogenous levels oscillate in a 24 h cycle. Here, we evaluated whether cyclin B1 expression is altered in heme-treated cells. In contrast to its up-regulation in siPer2 treated cells, luciferase reporter assay showed a decrease in cyclin B1 promoter activity in response to heme treatment. These results may reflect a complex pattern of regulation in which Per2 acts as a sensor molecule to monitor changes in both environmental and cellular conditions that will impact cell progression.
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 1070.
Abstract 1075: Cul1 Expression Is Increased in Early Stages of Human Melanoma
Authors: Chen Guangdi , Cheng Yabin , Martinka Magdalena , Li Gang 
Published: February 2011

Abstract
As the largest family of ubiquitin-protein E3 ligases, the SCF (Skp1/Cullin/Rbx1/F-box protein) complexes ubiquitinate a broad range of proteins involved in cell cycle progression, signal transduction and transcription. Cullin1 (Cul1) serves as a rigid scaffold in SCF complex for Rbx1, Skp1 and F-box protein subunits assembly and aberrant expression of Cul1 is involved in dysfunction of SCF E3 ligases. To investigate the role of Cul1 in the development of melanoma, we examined the expression of Cul1 in melanocytic lesions at different stages and analyzed the correlation between Cul1 expression and clinicopathologic parameters by tissue microarray and immunohistochemistry. The result showed that Cul1 expression was significant increased in primary and metastatic melanoma compared with dysplastic nevi, while there was no significant difference of Cul1 expression between primary and metastatic melanoma, which suggested that Cul1 plays an important role in the initiation stage of melanoma development. We found knockdown of Cul1 inhibited melanoma cell growth and overexpression of Cul1 promoted melanoma cell growth through regulating CDK inhibitor p27Kip expression. Knockdown of Cul1 abrogated Skp2-induced p27 degradation in melanoma cells. These results suggested that Cul1 is involved in cell cycle regulation of melanoma cells via Cul1-dependent ubiquitination and degradation of the p27kip1 by SCFSkp2 complex. In conclusion, our data indicate that Cul1 may serve as a potential marker for human melanoma initiation and early diagnosis.
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 1075.
Abstract 1076: Reversible effect of all-trans-retinoic acid on AML12 hepatocyte proliferation and cell cycle progression
Authors: Murphy Lynea , Moore Tanya , Nesnow Stephen 
Published: February 2011

Abstract
The role of all-trans-retinoic acid (atRA) in the regulation of cellular proliferation and differentiation is well documented. Numerous studies have established the cancer preventive properties of atRA which functions to regulate levels of cell cycle proteins essential for the G1/S transition and progression through S phase. Using AML12 cells, a non-transformed immortalized mouse hepatocyte cell line, the goals of this study were to first determine if changes in AML12 cell proliferation could be observed in response to atRA treatment and establish whether this was a suitable system to investigate molecular mechanisms altered by hepatocarcinogens. Cells were treated with 1µM and 5 µM atRA for 2 to 10 days. At various time points, control (DMSO) and treated cells were enumerated to determine the effect of atRA on AML12 cell proliferation. At 5 days of atRA treatment, there was a 56% decrease in the number of atRA treated cells when compared to control cells. This effect was reversible as an increase in cell number was observed two days after removal of atRA from the treatment media. Cell cycle analysis by flow cytometry using propidium iodide stained AML12 cells showed a significant reduction (p&lt;0.05) in S phase cells and a significant increase (p&lt;0.05) in G1 phase cells with 48 hours of atRA treatment when compared to control cells indicating a block at the G1/S checkpoint. Western analysis of control and treated whole cell lysates revealed a decrease in phosphorylated (Serine807/Serine811) retinoblastoma protein (pRb). Taken together, these results indicate that proliferation in AML12 hepatocytes can be reversibly modified by atRA by regulating these cells at the G1/S checkpoint with a reduction in pRb. Previous studies of liver tissues collected from mice exposed to the hepatocarcinogenic fungicide, propiconazole, have revealed an increase in cellular proliferation, increases in atRA metabolism as well as decreases in the levels of hepatic atRA. Based on the results of the present experiments, AML12 hepatocytes provide an optimal in vitro system to elucidate the molecular mechanism by which propiconazole induces hepatotumorigenesis. This work was reviewed by EPA and approved for publication but does not necessarily reflect official Agency policy.
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 1076.
Abstract 1077: Galectin-1 is implicated in G1/S-checkpoint control following irradiation - possible explanation of Galectin-1 mediated radioresistance
Authors: Huebner Alexander , Perry James , Siedow Michael , Zhang Min , Chakravarti Arnab , Lautenschlaeger Tim 
Published: February 2011

Abstract
Purpose:
The purpose of the conducted study was to examine a possible therapeutic relevance of Galectin 1 (Gal-1), a beta-galactoside binding protein. Gal-1 is overexpressed in high grade gliomas and leads to increased radioresistance in glioma cell culture models. Inhibition of Gal-1 increases radiosensitivity and thus is a potential therapeutic target for radiation sensitization. P53 has been shown to negatively regulate Gal-1, hence radiosensitivity could possibly be cell cycle mediated.
Experimental Design:
We used flow cytometry based cell cycle analysis to investigate cell cycle distribution of LN 229 glioma cells following irradiation. LN229 control cell lines and shRNA mediated Gal-1 knockdown LN 229 cell line were exposed to 6 Gy of irradiation and cell cycle analysis was performed. Furthermore Western blot analysis was carried out, probing for multiple proteins implicated in cell proliferation. The phosphorylation status of a variety of phosphorylation sites of p53, Chk1/2 and AKT were examined. Additionally p53-Gal-1 double-knockdown cell lines were created and clonogenic survival assays as well as AnnexinV apoptosis assays were conducted to analyze the influence on radiation sensitivity.
Results:
The results of the flow cytometry based cell cycle analysis show significant differences between the LN 229 control cell line and the Gal-1 knockdown cell line after irradiation. 24 h after irradiation 77 % of the control line cells are in G1 whereas only 60 % of the Gal-1 knockdown cells are in G1.
Previous data has identified differences in the phosphorylation status of Akt in control vs. Gal-1 knockdown glioma cell lines. Phosphorylation of Akt is induced after irradiation. Western blot analysis indicates a reduction of phosphorylated Chk1/2 in Gal1 knockdown cell lines after irradiation. The phosphorylation state of the p53 phosphorylation site, correlating with Chk1/2 activity, exhibit anticipated results.
P53-Gal-1 double-knockdown cell lines demonstrate significantly reduced clonogenic survival compared to control cell lines.
Conclusions:
The finding that less Gal-1 knockdown cells are in G1 phase after irradiation and that there is a reduction in phosphorylated Chk1/2 leads to the conclusion that Gal-1 knockdown abrogates G1 arrest through a Chk1/2 mediated pathway. That means in reverse that Gal-1 can mediate cell cycle arrest, thus potentially can explain Gal-1 mediated radioresistance. Further analysis of Chk1/2 independent phosphorylation sites of p53 is going to be conducted.
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 1077.
Abstract 1081: The role of calcium in relationship of microtubule stabilization, mitotic arrest, and apoptosis induced by Taxol in breast cancer cells
Authors: Pan Zhi , Gollahon Lauren 
Published: February 2011

Abstract
Background: Our previous study showed that Taxol, an important anticancer agent for breast cancer, directly releases calcium from the endoplasmic reticulum (ER), promoting subsequent apoptosis in breast cancer cells. Taxol also stabilizes microtubules, causing mitotic arrest. The relationship between these events and apoptosis remains unclear. The purpose of this study was to investigate the connection between calcium regulation, mitotic arrest and apoptosis induced by Taxol treatment.
Objective & Specific Aims: To accomplish this, we (1) Visualized the microtubule changes induced by Taxol at different dosages after different exposure times, (2) Quantified the cell cycle arrest induced by Taxol at different dosages after different exposure times, (3) Analyzed whether agents that interfere with intracellular calcium fluxes affect microtubule stabilization, mitotic arrest and apoptosis during Taxol treatment.
Study Method: Breast cancer cell lines MDA-MB-468, MDA-MB-231, MCF-7 were treated with two Taxol dosages (∼10−7M and ∼10−6M). Microtubule changes were detected using immunocytochemistry. Cell cycle analysis was detected using flow cytometry. Cells were pretreated with the cytosolic calcium chelator BAPTA-AM and the ER calcium inhibitor 2-APB to interfere with the calcium changes induced by Taxol. This allowed us to determine whether Taxol-induced mitotic arrest was calcium dependent. Free cytosolic calcium changes were measured by Fluo-AM calcium dye, and ER calcium changes were specifically measured by the advanced calcium cameleon D1ER.
Results & Relevance: Our data showed that microtubule stabilization and mitotic arrest were observed (6h) before significant apoptosis occurred at 12h exposure. Pretreatment of calcium agents inhibited both mitotic arrest and apoptosis induced by Taxol. High (∼10−6M) dosage Taxol induced calcium-promoting mitotic arrest, whereas low (∼10−7M) dosage Taxol did not. A similar pattern was also observed in our previous apoptosis analysis, indicating calcium, cell cycle arrest, and apoptosis are tightly associated with each other and need further investigation. In summary, our results suggest elucidating the role of calcium is essential to understand the process through which the widely used anticancer agent Taxol induces mitotic arrest and apoptosis. It will provide new insights into the action of Taxol and aid in the development of more effective breast cancer therapies.
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 1081.
Abstract 1082: BI 811283, a potent inhibitor of the mitotic kinase Aurora B, shows dose- and schedule-dependent efficacy in human cancer xenograft models
Authors: Gürtler Ulrich , Tontsch-Grunt Ulrike , Zahn Stephan K. , Quant Jens , Adolf Guenther R. , Solca Flavio 
Published: February 2011

Abstract
Background. The serine/threonine kinase Aurora B is involved in the regulation of several mitotic processes, including chromosome condensation, congression and segregation as well as cytokinesis. The essential functions of Aurora B and its overexpression in many cancer types render this protein kinase an attractive target for therapeutic intervention. BI 811283, a potent inhibitor of this key mitotic regulator, inhibits proliferation of a wide range of cultured human cancer cells at low nanomolar concentrations by inducing polyploidy, senescence and apoptosis.
Methods. BomTac:NMRI-Foxn1nu mice were grafted subcutaneously with NCI-H460 non-small cell lung carcinoma (mutant KRAS, wild-type p53), HCT 116 colon carcinoma (mutant KRAS, wild-type p53) or BxPC-3 pancreas adenocarcinoma cells (wild-type KRAS, mutant p53). Treatment was initiated when the tumors had reached a volume of ∼50 mm3. BI 811283 was injected intravenously once or twice weekly as a single bolus or b.i.d. Alternatively, the compound was administered once-weekly by a continuous 24 h infusion via subcutaneously implanted osmotic mini-pumps. Multiple dose levels and dosing schedules were evaluated.
Results. In models of human non-small cell lung cancer, colon carcinoma and pancreas carcinoma, multiple cycles of treatment with BI 811283 at total weekly doses of 20 to 75 mg/kg resulted in dose-dependent inhibition of tumor growth or tumor regression. Continuous s.c. infusion at 20 mg/kg over 24 h once-weekly was clearly superior to all bolus injection schedules delivering weekly doses up to 75 mg/kg. Furthermore, regression of large tumors (350 mm3) was induced in the HCT 116 colon carcinoma model. Biomarker analyses of HCT 116 tumors revealed that therapeutic doses of BI 811283 inhibited phosphorylation of histone H3, a direct substrate of Aurora B. Histological examination showed an accumulation of enlarged, multinucleated cells in accordance with the expected mechanism of action.
Conclusions. BI 811283 has demonstrated potent antitumor activity in multiple cancer models at well-tolerated doses; treated tumors show hallmarks of Aurora B inhibition. Continuous infusion over 24 h provides a superior therapeutic index compared with bolus administration. The compound is currently under investigation in Phase I 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 1082.
Abstract 1088: Differences in p53 signaling following induction of nucleotide pool deficiencies with hydroxyurea or PALA
Authors: Heyer Cortney L. , Moran Richard G. 
Published: February 2011

Abstract
The tumor suppressor p53 is stabilized following the induction of deficiencies in nucleotide pool levels by antimetabolites. N-(phosphonacetyl)-L-aspartate (PALA) reversibly inhibits aspartate transcarbamylase, causing interruption of de novo pyrimidine synthesis; hydroxyurea (HU) reversibly inhibits ribonucleotide reductase, inhibiting the conversion of ribonucleotide triphosphates to deoxynucleotide triphosphates. When HCT116, a human colon carcinoma cell line, is treated with either HU or PALA, p53 accumulates and cells arrest in S-phase. Beyond these similarities, the cellular responses to PALA and HU are strikingly different. Chk1 is phosphorylated to a far greater extent in HU-treated HCT116 cells than following PALA treatment. The lack of Chk1 phosphorylation observed during PALA treatment was found to be due to the p53-dependent transcriptional activation of the Wip1 phosphatase, rather than the inactivity of ATR. Chromatin immunoprecipitation studies performed on PALA-treated cells demonstrated the presence of p53 at the Wip1 promoter, and both Wip1 transcript and protein levels were elevated. In contrast, the residency of p53 over the Wip1 promoter was not observed during HU treatment, nor was Wip1 protein or transcript elevated. During PALA treatment of the isogenic p53 null HCT116 cell line, Wip1 transcript levels are not elevated and Chk1 phosphorylation is restored, demonstrating the role of p53 in the elevation of Wip1 following PALA treatment. Although p53 accumulates during both HU and PALA treatment, the responses to the individual drugs differ so greatly that PALA-treated cells undergo a p53-dependent apoptosis while HU-treated cells enter a cytostatic cell cycle arrest. The post-translational modifications of p53 are dissimilar in the two treatments suggesting a variation of signaling to p53 as well as the downstream actions of the modified p53. The accumulated p53 in PALA-treated cells is phosphorylated at serine 46, an event needed to direct p53 to pro-apoptotic promoters; this phenomenon is not observed in HU-treated cells. Hence, during de novo pyrimidine synthesis inhibition, p53 promotes Wip1 transcription causing dephosphorylation of Chk1 leading to apoptosis. When deoxynucleotide triphosphate synthesis is inhibited, Chk1 is phosphorylated promoting cellular arrest in S-phase.
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 1088.
Abstract 1097: Arf induction by Tgf-beta2 is mediated by Smad-2/3 dependent enhancement of Arf transcription
Authors: Zheng Yanbin , Zhao Yi D. , Chu Patricia , Skapek Stephen X. 
Published: February 2011

Abstract
The Arf tumor suppressor gene product, p19Arf, is induced in response to certain oncogenic signals to block cancer development and progression. How the oncogenic cues are coupled to Arf promoter activation remains poorly defined, though. We took advantage of the fact that the Arf promoter is strictly controlled during development to investigate the normal regulatory mechanisms. We have recently published that Tgf-beta2 is required for Arf promoter activation at several sites in the developing mouse. To define mechanisms for the regulation, we developed a cell culture-based assay. We now show that Tgf-beta2 (5 ng/ml) induced p19Arf expression in WT mouse embryo fibroblasts (MEFs), enhanced Arf promoter activity in Arf lacZ/lacZ MEFs, and maintained a G1 cell cycle arrest in an Arf-dependent manner. The Arf promoter was also increased by Tgf-beta1, which functionally overlaps with Tgf-beta2, but not by Pdgf-B, a potent mitogen, nor BMP-2, another Tgf-beta superfamily member. To elucidate which pathway mediated the Tgf-beta2 effects, we used a panel of chemical inhibitors of Smad-dependent and -independent pathways. Among them, SB431542, a Tgf-beta type I receptor inhibitor, blocked Smad2 phosphorylation and impeded Tgf-beta2 induction of Arf. Genetic studies confirmed this because RNAi-driven knock-down of Tgf-beta receptor I, Smad2 or Smad3 impaired ArflacZ induction by Tgf-beta2. Further, Tgf-beta2 failed to induce p19Arf in Cre-treated Tgfbr2 flox/flox MEFs, in which Tgf-beta receptor II was deleted. Interestingly, the p38 MAPK inhibitor SB203580 partially impeded Arf induction, showing cross-talk with Smad signals. Chromatin immunoprecipitation revealed that Tgf-beta2 induced the binding of Smad2/3 and RNA Polymerase II to genomic DNA proximal to Arf exon 1 beta. Increased promoter binding preceded the progressively induced Arf mRNA and primary Arf transcripts at 24 and 48 hours, indicating that the induction was due to increased transcription. In summary, our results indicate that Tgf-beta2 induces the Arf promoter via a direct Smad-dependent signaling pathway. This study provides the first evidence that Arf expression is coupled to cell extrinsic signals. We are currently exploring this pathway in other type of cells and testing whether Arf induction by oncogenes also depends on Tgf-beta signaling.
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 1097.