bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 487: RNAi-mediated silencing of TCF7L2 sensitizes colorectal cancer cells to radiation therapy
Authors: Grade Marian , Kendziorra Emil , Emons Georg , Ahlborn Kerstin , Spitzner Melanie , Gaedcke Jochen , Rave-Frank Margret , Pukrop Tobias , Beissbarth Tim , Becker Heinz , Ghadimi Michael , Ried Thomas 
Published: February 2011

Abstract
Background:
The standard treatment for locally advanced rectal carcinomas consists of preoperative chemoradiotherapy (CT/RT), followed by radical surgery. However, the clinical response to this treatment strategy is very heterogeneous. To determine the molecular basis of disparate response, we recently profiled a series of responsive and resistant rectal cancers using gene expression microarrays and identified a set of differentially expressed genes. One gene that was significantly over-expressed in the resistant tumors was TCF7L2 (also known as TCF4), the main downstream effector of the Wnt signaling pathway. The aim of this study was to understand its role in treatment response by testing the hypothesis that RNAi-mediated silencing of TCF7L2 sensitizes tumor cells to radiation therapy.
Methods:
The colorectal cancer cell line SW480, which is relatively resistant to radiation, was transfected with two different shRNA-vectors targeting TCF7L2, and a non-silencing control. Subsequently, stable single cell clones were established, and knockdown efficiency was analyzed by Western blot analysis. For each vector, individual clones were irradiated at 2, 4, 6 and 8 Gy. Colonies were counted after 10 days to calculate the respective surviving fractions.
Results:
TCF7L2 protein levels were reduced to ∼ 34% for shRNA_1, and ∼ 29% for shRNA_2. This led to a ∼ 1.6-fold growth inhibition (plating efficiency) compared to the non-silencing control. Importantly, RNAi-mediated silencing of TCF7L2 significantly reduced colony-formation after radiation (dose reduction factors of ∼ 1.5 and ∼ 2.0 at 37% survival for shRNA_1 and shRNA_2, respectively). These results were validated in a second cell line (HT29). In addition, we analyzed global gene expression profiles after RNAi to analyze the global transcriptomic changes induced by silencing TCF7L2.
Conclusion:
TCF7L2 is over-expressed in rectal carcinomas resistant to chemoradiotherapy. RNAi-mediated silencing of this gene caused a significant growth inhibition and, importantly, radiosensitization of colorectal cancer cells. Thus, TCF7L2 might represent a potential molecular target to sensitize a priori resistant tumor cells. Additionally, these data provide first evidence that the Wnt signaling pathway might not only be central for the development of colorectal cancers, but also for the resistance to therapy.
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 487.
Abstract 4877: Polyamine analogues modulate gene expression by inhibiting KDM1/LSD1 and altering chromatin structure in human breast cancer cells
Authors: Zhu Qingsong , Huang Yi , Marton Laurence J. , Woster Patrick M. , Davidson Nancy E. , Casero Robert A. 
Published: February 2011

Abstract
Gene expression can be modulated through histone methylation, which is tightly control by the balance of histone methytransferase and demethylase. Methylation (mono-, di- and tri-methylation) of lysine 4 of histone 3 is associated with active gene transcription. Lysine-specific demethylase 1 (KDM1/LSD1) can enzymatically demethylate mono- and di-methyl H3K4 that leads to suppression of gene transcription. Our previous studies demonstrated that a novel class of polyamine analogues can effectively inhibit KDM1/LSD1 and induce re-expression of candidate epigenetically silenced genes. The purpose of this study was to examine the molecular effects of polyamine analogues, 2d and PG11144, on global gene expression profile by inhibition of KDM/LSD1 in estrogen receptor-negative MDA-MB-231 breast cancer cells. The possible mechanisms of polyamine analogues mediating modulation of gene expression were also investigated. Treatment with polyamine analogous, 2d or PG11144, significantly increases global histone 3 dimethylation at lysine 4 (H3K4me2), as well as altering gene expression. There are 274 and 625 genes changed at least 2-fold after treatment with 2d and PG11144 respectively. The genes’ expression levels of twelve 2d up-regulated and fourteen PG11144 up-regulated genes were confirmed by real-time RT-PCR. Chromatin immunoprecipitation analysis demonstrated that up-regulated gene expression by polyamine analogous is associated with up-regulated active histone marks (H3K4me, H3K4me2 and ActH3K9) and down-regulated repressive histone marks (H3K9me2 and H3K27me3) in the promoter regions of the relevant target genes. Supported by NIH CA 88843, CA51085, Breast Cancer Research Foundation, and Komen for the Cure KG080923.
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 4877.
Abstract 4886: Knockdown of EZH2 inhibits the malignant phenotype of lung cancer cells
Authors: Liu Fang , Xi Sichuan , Zhang Mary , Kemp Clinton , Rao Mahadev , Zhang Yuwei , Schrump David 
Published: February 2011

Abstract
Polycomb group (PcG) proteins, which are global epigenetic gene silencers, play key roles in the maintenance of stem cell pluripotency, multicellular development, and tumorigenesis. EZH2, a core component of PcG and H3K27 methyltranferase, is highly expressed during embryogenesis and malignant transformation. Presently the mechanism by which EZH2 mediates tumorigenesis and metastasis are unclear. Our recent studies indicate that cigarette smoke condensate (CSC) increases EZH2 expression and global levels of H3K27Me3 in immortalized human bronchial epithelial cells (HBEC). In the present study, we sought to further investigate the role of EZH2 in modulating the malignant phenotype of lung cancer cells. Western blot experiments demonstrated that EZH2 was significantly over-expressed in lung cancer cell lines but not in normal human bronchial epithelial cells (NHBE) or small airway epithelial cells (SAEC). EZH2-shRNA lentiviral vectors were used to knockdown EZH2 in A549 and Calu-6 lung cancer cells as well as CSC-treated HBEC. Knockdown of EZH2 decreased H3K27Me3 levels, and diminished proliferation and clonogenicity of these cells in soft agar. These observations coincided with down-regulation of Cyclin D1. Additional western blot and flow cytometry experiments are underway to examine the impact of EZH2 knockdown on cell cycle progression and apoptosis in lung cancer cells. Illumina gene expression array experiments are also in progress to identify PcG target genes upregulated by knockdown of EZH2 that correlate with reduced proliferation and decreased clonogenicity of these cells. Collectively, these data indicate that knockdown of EZH2 inhibits the malignant phenotype of lung cancer cells, and suggest that EZH2 is a promising target for lung cancer therapy.
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 4886.
Abstract 489: Selective inhibitor of STAT1 sensitizes breast cancer cells to radiation therapy
Authors: Timofeeva Olga A. , Tarasova Nadya , Wang Honghe , Perantoni Alan , Dritschilo Anatoly 
Published: February 2011

Abstract
About 70% of breast cancer patients with progressive disease are resistant to conventional cancer treatments such as adjuvant chemotherapy and/or radiation therapy. Recently, the STAT1 signaling pathway has been identified as a predictive marker of poor outcome in breast cancer patients and as a factor responsible for radiation and chemotherapy resistance. STAT1 was initially considered as a tumor suppressor, since it causes growth arrest and apoptosis after stimulation with interferons and in response to DNA damage. However, constitutive activation/overexpression of STAT1 results in pro-survival cellular signaling via enhancement of expression of pro-survival proteins Mcl-1 and Hsp27 that might be responsible for observed radiation resistance of breast cancer cells. It may therefore be beneficial to sensitize patients with resistant disease to radiation or chemotherapy by inhibiting STAT1 signaling, yet there has been little effort to develop direct inhibitors of STAT1.
We have recently developed a selective inhibitor ST1-Hel2A-2 that directly binds to the N-terminal domain of STAT1, but not other STAT family members, and inhibits STAT1 transcriptional activity (ACS Chem Biol, 2007. 2(12): 799). The inhibitor kills breast cancer cells at nanomolar concentrations but does not effect survival of normal mammary epithelial cells. We have now found that inhibition of STAT1 N-domain can further sensitize breast cancer cells to ionizing radiation. The mechanism for observed sensitization at least partially depends on down-regulation of STAT1 target genes, including pro-survival Hsp27. In addition, ST1-Hel2A-2 is capable of disrupting the STAT1 N-domain protein-protein interactions. Yeast two-hybrid screening has revealed that the STAT1 N-domain associates with double-stranded RNA-activated protein kinase (PKR) and DNA glycosylase NEIL1. Both PKR and NEIL1 facilitate DNA repair after ionizing radiation and protect mammalian cells from radiation-mediated cell death. ST1-Hel2A-2 disrupts STAT1 interactions with both proteins resulting in a reduced DNA repair capacity.
Our data suggest that a novel inhibitor of STAT1 decreases radiation resistance of breast cancer cells through downregulation of pro-survival genes and inhibition of DNA repair. Inhibition of STAT1 signaling appears to be a promising strategy in overcoming radiation resistance and can be used as an effective treatment of metastatic breast cancer when combined with conventional 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 489.
Abstract 4890: ING2, a p53- and chromatin-interacting protein, is essential to mammalian spermatogenesis: Implications in male infertility in humans
Authors: Saito Motonobu , Kumamoto Kensuke , Horikawa Izumi , Robles Ana I. , Furusato Bungo , Okamura Shu , Goto Akiteru , Yamashita Taro , Nagashima Makoto , Lee Tin-Lap , Baxendale Vanessa , Rennert Owen M. , Takenoshita Seiichi , Yokota Jun , Sesterhenn Isabell A. , Trivers Glenwood E. , Hussain Perwez , Harris Curtis C. 
Published: February 2011

Abstract
ING2 (inhibitor of growth family, member 2) plays pivotal roles in the regulation of cellular senescence, apoptosis, DNA damage repair, gene transcription and chromatin modification. Our previous in vitro studies on cellular senescence suggested that ING2 functionally interplays with the p53 tumor suppressor protein in two different manners: endogenous ING2 inhibits senescence and the transcriptional repression of ING2 by p53 abrogates this inhibition; and overexpressed ING2 enhances p53 acetylation and stability to induce senescence. ING2, as a subunit of the mSin3A-HDAC1 (histone deacetylase 1) complex, specifically binds to tri-methylated lysine 4 of histone H3 (H3K4me3) via its plant homeodomain (PHD) finger and regulates gene expression through chromatin modifications in response to DNA damage. This study investigates the in vivo developmental and physiological functions of ING2. Abundant expression of ING2 in mouse and human testes and its decreased expression associated with male infertility and defective spermatogenesis in humans suggested an essential role of ING2 in spermatogenesis, which is a process tightly regulated by chromatin modifications. Consistently, male mice deficient for Ing2 were infertile. Their testes had degeneration of seminiferous tubules, which became more severe with age, and showed enhanced p53-dependent and -independent apoptosis. Spermatogenesis arrest at meiotic phase in Ing2−/− testes was due to impaired HDAC1 accumulation and deregulated chromatin acetylation. This study establishes ING2 as a novel mammalian regulator of spermatogenesis, suggests that an HDAC1/ING2/H3K4me3-regulated, stage-specific coordination of chromatin modifications is essential to normal spermatogenesis, and provides a model system to study idiopathic and iatrogenic infertility in men, including those who had cancer chemotherapy and radiotherapy. Spontaneous tumor incidence and spectrum were similar in wild-type and Ing2-deficient mice.
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 4890.
Abstract 4898: Polycomb group molecule PHC3 regulates polycomb complex composition and prognosis of osteosarcoma
Authors: Iwata Shintaro 
Published: February 2011

Abstract
PHC3 is a member of the human polycomb complex and has been regarded as a candidate tumor suppressor of osteosarcoma. We performed a mutation survey and PHC3 expression analysis by quantitative real-time PCR using ten osteosarcoma cell lines and 42 primary osteosarcoma samples. Relative PHC3 expression values of clinical samples were analyzed with clinical outcomes, and it was suggested that lower PHC3-expressing patients had significantly worse overall survival. Relative PHC3 values of clinical samples were less than those of normal bone tissues, whereas greater than those of cell lines. By denaturing high performance liquid chromatography analysis and direct sequencing, we found a PHC3 missense mutation in U2OS cells, which resulted in arginine56 to proline substitution. The same point mutation existed in four of 42 primary osteosarcoma samples. Regarding functional analysis, PHC3 expression significantly suppressed colony formation of tumor cells. Intriguingly, polycomb repressive complex 1 members, Bmi1 and Ring1b proteins, were reduced in PHC3-expressing cells. Deletion mutant PHC3 expression suggested that the carboxyl terminus of PHC3 has a role in suppression; the above-mentioned point mutation of PHC3 also lost inhibitory activities. Conversely, Bmi1 expression reduced PHC3 at the mRNA level and induced the proliferation of osteosarcoma cells. Taken together, we confirmed the role of PHC3 as a tumor suppressor in osteosarcoma cells and found that PHC3-dependent tumor suppression may be caused by modification of the composition of polycomb repressive complex 1 in 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 4898.
Abstract 4901: Polycomb group proteins in myelodysplastic syndromes and its progression to acute myeloid leukemia
Authors: Chen Zi-Xing , Shen Hong-jie , Cen Jian-nong , Wang yuan-yuan , He Jun , Qi Xiao-fei 
Published: February 2011

Abstract
Polycomb group BMI-1 and EZH2 in addition to SALL4 and P16 were detected in 89 MDS bone marrow including 49 newly diagnosed MDS and 40 treated MDS by using qRT-PCR. We found the expression level of BMI-1, EZH2, SALL4 and P16 were remarkably higher than that in non-MDS cytopenias, such as iron-deficiency anemia (P&lt;0.05). BMI1 expression level has an increasing tendency from MDS-RA to MDS-RAEB without statistically significant. On the contrary, the EZH2 expression level of MDS-RAEB is lower than that of MDS-RA (P&lt;0.05). Although BMI1 expression level was down-regulated when MDS patients were in morphological remission, EZH2, SALL4 and P16 expression levels still remain abnormally high level (P&lt;0.05). We also found that BMI-1 expression level in MDS CD34+ cells was correlated with International Prognostic Scoring System (IPSS) score (R=0.712, P=0.012). BMI-1 had the highest positive rate in MDS-AML. To explore the function of BMI-1 and its possible role in the pathogenesis of MDS transformation into acute leukemia. We have cloned cDNA of BMI-1 and transfected into U937, K562 leukemic cells mediated by MSCV retroviral vector. The viability In vitro of BMI1 transfected cell was higher than control and BMI1 transfected cell also inhibited As2O3-induced apoptosis. Furthermore, BMI1 repressed the expression of EZH2, PTEN and P16 in U937, and repressed the expression of EZH2 and PTEN in K562. Our results provide evidence suggesting that the clonal disorder of MDS patients remained in molecular aberration even after achieving clinical remission. The In vitro results suggest that BMI-1 may play a key role in MDS progression via P16 pathway or PTEN pathway.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
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 4901.
Abstract 4902: Methylation profiles in head and neck cancer
Authors: Demokan Semra , Yalniz Zubeyde , Suoglu Yusufhan , Ulusan Murat , Dalay Nejat 
Published: February 2011

Abstract
Purpose: Among human malignancies, head and neck cancer (HNSCC) is the sixth most common cancer type in the world. Multiple genetic and epigenetic changes may contribute to the development of HNSCC. One of the epigenetic alterations, aberrant methylation in the promoter regions of multiple genes that lead to transcriptional silencing, has been shown in various cancer types including HNSCC. In this study we aimed to evaluate the epigenetic changes specific to HNSCC by investigating aberrant promoter hypermethylation of a panel of 24 tumor suppressor genes.
Experimental Design: We investigated methylation of the promoter regions by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA). The methylation status of the selected genes were analyzed in 126 patients with HNSCC. Tumor and corresponding normal tissue samples were obtained during surgical resection. Probes added to the samples hybridized with their target sequence and were amplified by PCR depending on the methylation status of the target. The amplified products were detected by sequence type capillary electrophoresis. Peak sizes and areas were normalized and the relative signal peaks were compared to determine the methylation status.
Results: 18 of 24 (75 %) genes displayed methylation in the tumor samples while none of the corresponding normal tissue samples were methylated. In 67.5 % (85/126) of the tumors the promoter regions were hypermethylated in at least one of the genes. The most frequently methylated genes were RARB (retinoic acid receptor beta), CHFR (checkpoint with forkhead and ring-finger domains) and CDH13 (Cadherin 13) genes. In 50 (39.7 %) patients, methylation was observed in more than one gene.
Conclusions: Methylation of the CHFR, RARB and CDH13 gene promoters is a frequent event in HNSCC, demonstrating potential for these genes as biomarkers in detection strategies.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
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 4902.
Abstract 491: The roles of homologous recombination repair and cell cycle checkpoints in radiosensitization by the Chk1/2 inhibitor, AZD7762
Authors: Morgan Meredith Ann , Parsels Leslie , Zhao Lili , Parsels Joshua , Davis Mary , Arumugarajah Sankari , Canman Christine , Zabludoff Sonya , Maybaum Jonathan , Lawrence Theodore 
Published: February 2011

Abstract
The combination of gemcitabine and radiation is superior to gemcitabine alone for locally advanced pancreatic cancer however the median survival is only approximately one year. We have previously demonstrated that inhibition of Chk1 (checkpoint kinase 1) sensitizes pancreatic cancer cell lines, as well as patient-derived tumor xenografts, to both radiation and gemcitabine-radiation. The exact mechanism(s) for this sensitization, however, remains unclear. Based on the abilities of Chk1 to induce cell cycle arrest and promote HRR (homologous recombination repair) in response to DNA damage, we set out to determine the relevance of these mechanisms to radiosensitization by AZD7762, an AstraZenca Chk1/2 inhibitor currently in Phase I clinical trials. We tested the effects of AZD7762 on survival, cell cycle checkpoints, Rad51 focus formation and HRR activity in response to radiation and gemcitabine-radiation in two pancreatic cancer cell lines, Panc-1 and MiaPaCa-2. We began this study with the observation that AZD7762 sensitized MiaPaCa-2 cells to radiation and gemcitabine-radiation with enhancement ratios of 1.5 ± 0.08 (AZD7762), 1.2 ± 0.07 (50 nM gemcitabine), and 1.9 ± 0.16 (AZD7762 + 50 nM gemcitabine) but did not sensitize Panc-1 cells where enhancement ratios were 1.0 ± 0.03 (AZD7762), 1.5 ± 0.11 (100 nM gemcitabine), and 1.4 ± 0.05 (AZD7762 + 100 nM gemcitabine). AZD7762 inhibited Chk1 in both cell lines as evidenced by accumulation of Cdc25A and abrogation of the radiation-induced G2 arrest. To begin to determine the contribution of HRR to radiosensitization by AZD7762, we utilized a DR-GFP reporter assay which measures homology directed repair of an I-SceI endonuclease-induced DNA double strand break in an integrated GFP reporter gene in MiaPaCa-2 and Panc-1 cells. Treatment of cells expressing the DR-GFP reporter with 100 nM AZD7762 produced a 2- to 3-fold (P&lt;0.05) inhibition of HRR activity in MiaPaCa-2 cells but minimal to no inhibition in Panc-1 cells. Inhibition of HRR by AZD7762 was accompanied by a reduction in the number of MiaPaCa-2 cells which stained positive for Rad51 foci in response to radiation (32 ± 3% versus 9 ± 3%; P&lt;0.05). Taken together these results suggest that inhibition of HRR may play a role in the mechanism(s) of radiosensitization by Chk1 inhibition. It will be important in future studies to further decipher the contributions of cell cycle checkpoint abrogation and HRR inhibition to the mechanisms of radiosensitization by 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 491.