bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract LB-148: DDX5 promotes ARF gene expression and apoptosis induced by deregulated E2F1
Authors: Kurayoshi Kenta , Ohtani Kiyoshi 
Published: July 2016

Abstract
The transcription factor E2F, the main target of the tumor suppressor pRB, plays central roles not only in cell proliferation but also in tumor suppression. E2F promotes cell proliferation by activating growth-related genes in response to normal growth stimulation. On the other hand, E2F contributes to tumor suppression by activating pro-apoptotic and growth-suppressive genes such as ARF and TAp73 when deregulated from pRB upon dysfunction of pRB, a major oncogenic change. ARF is an upstream activator of the tumor suppressor p53, one of the two major tumor suppressors in addition to pRB. TAp73 is a member of the p53 family and activates p53-responsive genes. Importantly, physiological E2F activity induced by growth stimulation does not activate the latter genes, underscoring importance of deregulated E2F activity in tumor suppression upon oncogenic changes. However, the regulatory mechanism of deregulated E2F activity is not known in detail.
We found that deletion of N-terminal domain of E2F1 dramatically reduced its ability to activate ARF and TAp73 promoter, suggesting that E2F1 interacts with a factor(s) through its N-terminal domain to activate the tumor suppressor genes. Hence we explored novel E2F1-interacting factors using co-immunoprecipitation and LC/MS. Among the candidates, we found DEAD box 5 (DDX5) that functions not only RNA helicase but also transcriptional coactivator. DDX5 is reported to function as a coactivator for p53. Furthermore, E2F1 activity is regulated in similar manners as p53 such as by Chk1 and PRMT5. These observations suggest that DDX5 enhances not only p53 activity but also deregulated E2F1 activity. We thus examined effect of DDX5 on deregulated E2F1 activity induced by overexpression of E2F1.
DDX5 enhanced E2F1 activation of ARF promoter depending on the integrity of N-terminal domain of E2F1. DDX5 mutant lacking RNA helicase activity retained the ability to enhance E2F1 activation of ARF promoter, indicating that the enhancement is independent of helicase activity. Furthermore, DDX5 enhanced endogenous ARF gene expression and apoptosis induced by E2F1 without affecting E2F1 expression level. Finally, knock down of DDX5 reduced E2F1-mediated activation of ARF promoter and ARF gene expression. These results suggest that DDX5 upregulates deregulated E2F1 activity and contributes to E2F1-induced apoptosis to protect cells from tumorigenesis.
Citation Format: Kenta Kurayoshi, Kiyoshi Ohtani. DDX5 promotes ARF gene expression and apoptosis induced by deregulated E2F1. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-148.
Abstract LB-149: LYAR promotes cell proliferation by repressing CHAC1 expression in neuroblastoma
Authors: Sun Yuting , Atmadibrata Bernard , Liu Bing , Liu Tao 
Published: July 2016

Abstract
Introduction: Neuroblastoma is a cancer of the sympathetic nervous system occurring mostly in infants and young children. Despite considerable progress in the treatment of neuroblastoma, 5-year survival rates have remained less than 50% for the majority of children with high-risk disease. Amplification of the MYCN oncogene and consequent overexpression of the N-Myc oncoprotein is a major prognostic indicator in neuroblastoma, which is strongly associated with aggressive tumour behaviour and poor patient outcome. N-Myc oncoprotein induces neuroblastoma by modulating gene and protein expression and consequently causing cell proliferation. LYAR (Ly-1 antibody reactive clone), a novel nucleolar protein with zinc finger DNA-binding motifs, is mostly involved in cell growth regulation in many cancers.
Results: Here we showed that N-Myc up-regulated LYAR expression in neuroblastoma cells. Conversely, LYAR up-regulated N-Myc expression. Affymetrix gene array studies revealed that the gene most significantly repressed by LYAR siRNAs was ChaC glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1). Consistent with this finding, RT-PCR and immunoblot confirmed that LYAR siRNAs increased CHAC1 gene and protein expression. Alamar blue assays and cell cycle analyses demonstrated that LYAR induced MYCN-amplified neuroblastoma cell proliferation in a CHAC1-depedent manner. Additionally, high levels of LYAR gene expression in human neuroblastoma tissues were associated with MYCN gene expression and predicted poor patient survival independent of patient age and disease stage.
Conclusions: Our data demonstrate LYAR as a potential target in neuroblastoma oncogenesis, and provide critical evidence to support the application of LYAR inhibitors for the therapy of neuroblastoma patients.
Citation Format: Yuting Sun, Bernard Atmadibrata, Bing Liu, Tao Liu. LYAR promotes cell proliferation by repressing CHAC1 expression in neuroblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-149.
Abstract LB-157: Chromatin alterations induce C-MYC and BRD4 downregulation in pediatric sarcoma
Authors: Da Costa Elodie , Armaos Gregory , Jacques-Ricard Simon , Beaudry Annie , Raynal. Noël 
Published: July 2016

Abstract
Sarcoma accounts for 15% of all pediatric cancers diagnosed every year. Refractory patients have a poor prognosis with a 5-year survival rate of 10%, demonstrating the need for development of new therapeutic approaches. Epigenetic events, including DNA methylation and post-translational histone modifications (such as histone acetylation), are responsible for silencing tumor suppressor genes and overexpressing oncogenes. In sarcomas, a better understanding of epigenetic alterations is needed to develop new epigenetic targeted therapies. Several epigenetics drugs have demonstrated anticancer activity against sarcoma cell lines but the identification of a specific target is still missing. We demonstrated that targeting histone acetylation may represent a specific
epigenetic mark in pediatric sarcomas. We identified that proscillaridin A, a newly defined epigenetic drug, has epigenetic and anticancer effects on osteosarcoma (U2OS) and rhabdomyosarcoma (RD) cell lines. Our findings show a decrease of histone 3 acetylation on specific lysine residues after a 48h-treatment with proscillaridin A at 5 nM, a clinically relevant dose. These effects correlate with downregulation of histone acetylation associated proteins such as bromodomain BRD4 and oncogene C-MYC. A 48h-treatment with proscillaridin A produces a G2/M block and a reduction in the clonogenic potential of both U2OS and RD cells with IC50 value of approximately 6 nM. Interestingly, remaining colonies of RD cells fully lost their abilities to growth after drug removal, suggesting a long-term epigenetic reprograming. We demonstrated that proscillaridin A epigenetic effects occurred through calcium signaling since its mechanism of action may be dependent on calcium-calmodulin kinase activity.These promising results illustrate the epigenetic and anticancer potential of proscillaridin A against pediatric sarcoma. Additional experiments are currently ongoing in order to further characterize the mechanism of action of proscillaridin A in vitro and in vivo.
Citation Format: Elodie Da Costa, Gregory Armaos, Simon Jacques-Ricard, Annie Beaudry, Noël Raynal. Chromatin alterations induce C-MYC and BRD4 downregulation in pediatric sarcoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-157.
Abstract LB-162: BRCA2, and not BRCA1, dependent crosstalk between replication stress suppression and nucleotide excision repair - Clinical implications
Authors: Pathania Shailja , Reed Rachel , Duan Haohui , Culhane Aedin , Garber Judy 
Published: July 2016

Abstract
BRCA2, a breast and ovarian tumor suppressor, is required for replication stress suppression through its role in repair of stalled replication forks. Here we report that inefficient resolution of stalled replication forks in absence of BRCA2 results in persistent accumulation of mostly un-phosphorylated RPA32 (at S33, T21 and S4/S8) at stalled replication forks. Furthermore, this ‘persistent’ accumulation of RPA32 coated ssDNA not only results in fork collapse, as marked by increased accumulation of both 53BP1 and Mre11 at the site of stalling, but also leads to suppression of nucleotide excision repair (NER), especially in S phase population. No such persistent RPA32 coated ssDNA is observed in BRCA1 depleted cells, suggesting that this intermediate is exclusive to BRCA2 deficiency. Furthermore, generation of this intermediate was not dependent on Mre11 implying that persistent accumulation of RPA32 coated ssDNA was not a result of excessive DNA processing by Mre11 exonuclease in absence of BRCA2. This is the first report of differences between BRCA1 and BRCA2 role at stalled replication forks. In this report, we also show that BRCA2 heterozygous primary mammary epithelial cells, and not BRCA1 heterozygous cells, are haploinsufficient for nucleotide excision repair. This would imply higher predisposition to skin lesions, including melanoma in BRCA2 mutation carriers. Risk for melanoma is indeed higher in BRCA2 mutation carriers compared to BRCA1 mutation carriers. We further confirmed that there exists a difference in mutational signature in whole genome sequences derived from BRCA1 and BRCA2 tumors, in line with the kind of differences expected if there is an increased NER defect in BRCA2 mutated cells when compared to BRCA1 mutated cells.
Our findings provide first such DNA repair mechanism based evidence that could potentially explain the differences in BRCA1 and BRCA2 mutation driven risk for melanoma. This mechanistic difference between BRCA1 and BRCA2 response at stalled replication forks, and subsequently a crosstalk with nucleotide excision repair, might also contribute towards other clinical differences observed in BRCA1 and BRCA2 mutation driven breast cancer.
Citation Format: Shailja Pathania, Rachel Reed, Haohui Duan, Aedin Culhane, Judy Garber. BRCA2, and not BRCA1, dependent crosstalk between replication stress suppression and nucleotide excision repair - Clinical implications. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-162.
Abstract LB-165: Multiple mechanisms disrupt let-7 miRNA biogenesis and function in neuroblastoma
Authors: Powers John T. , Tsanov Kaloyan , Roels Frederik , Spina Catherine , Ebright Richard , Seligson Marc , de Soysa Yvanka , Cahan Patrick , Pearson Daniel , Theißen Jessica , Tu Ho-Chou , LaPier Grace , Osborne Jihan , Ross Samantha , Collins James , Berthold Frank , Daley George 
Published: July 2016

Abstract
The let-7 microRNA family are known tumor suppressors often deregulated in cancer, yet the underlying mechanisms of let-7 disruption remain poorly understood. Neuroblastoma, a neural crest derived tumor, is defined in part by poor prognosis associated with genetic amplification of MYCN, itself a let-7 target. The let-7 biogenesis inhibitor LIN28B has recently been implicated as a critical regulator of MYCN, but through CRISPR-mediated gene disruption we show that LIN28B is dispensable for both MYCN protein expression and growth of MYCN-amplified neuroblastoma cell lines despite robust de-repression of let-7, prompting us to explore additional mechanisms for let-7 disruption. Consequently, we have found a novel non-coding role for amplified MYCN mRNA as a potent let-7 sponge that through exceptionally high expression defines a sub-class of self-sponging amplified-competing-endogenous-RNA (aceRNA) and reconciling the dispensability of LIN28B in neuroblastoma cell lines. Furthermore, by analyzing a large cohort of tumor samples from patients, we observe frequent genomic loss of let-7 that inversely associates with MYCN-amplification, providing a functional explanation for the known MYCN-amplification-independent pattern of chromosome 3p and 11q loss, which harbor let-7g and let-7a2, respectively. We thus propose a model whereby let-7 disruption by genetic loss, LIN28B expression, or aceRNA sponging is a unifying mechanism of neuroblastoma pathogenesis. Indeed, our data show that the majority of neuroblastomas have at least one let-7 disruption event and that genetic loss in non-MYCN-amplified tumors marks decreased survival, further underscoring its importance. The inverse selective relationship between allelic loss and sponging of let-7 from highly expressed or amplified oncogenes may have broad implications for oncogenesis.
Citation Format: John T. Powers, Kaloyan Tsanov, Frederik Roels, Catherine Spina, Richard Ebright, Marc Seligson, Yvanka de Soysa, Patrick Cahan, Daniel Pearson, Jessica Theißen, Ho-Chou Tu, Grace LaPier, Jihan Osborne, Samantha Ross, James Collins, Frank Berthold, George Daley. Multiple mechanisms disrupt let-7 miRNA biogenesis and function in neuroblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-165.
Abstract LB-168: MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer
Authors: Edmonds Mick D. , Boyd Kelli L. , Moyo Tamara K. , Mitra Ramkrishna , Duszynski Robert J. , Arrate Maria P. , Chen Xi , Zhao Zhongming , Blackwell Timothy S. , Eischen Christine M. 
Published: July 2016

Abstract
Lung cancer is the leading cause of cancer deaths and yet the genes that drive this malignancy are not entirely known. MicroRNA (miRNA) are important regulators of gene expression and aberrant miRNA expression has been linked to lung oncogenesis; however, little known about their contribution in tumor initiation. We’ve determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. miR-31 promotes lung cell proliferation and adenocarcinoma growth in vivo. We also developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. We identified 6 negative regulators of RAS/MAPK signaling (RASA1, SPRED1, SPRED2, SPRY1, SPRY3, SPRY4) as direct targets of miR-31. Analysis of human lung adenocarcinoma revealed that high miR-31 expression correlated to decreased target mRNA expression. miR-31 overexpression in lung cells results in increased RAS signaling and pharmacologic inhibition of MEK ablates miR-31 induced lung cell proliferation. Induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. Our study demonstrates for the first time that a miRNA can drive an epithelial cancer. Specifically we identified miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and demonstrate that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling.
Citation Format: Mick D. Edmonds, Kelli L. Boyd, Tamara K. Moyo, Ramkrishna Mitra, Robert J. Duszynski, Maria P. Arrate, Xi Chen, Zhongming Zhao, Timothy S. Blackwell, Christine M. Eischen. MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-168.
Abstract LB-169: Ovarian cancer cells selectively release exosomes containing tumor suppressor miRNAs to maintain SRC-mediated oncogenic activities
Authors: Rashed Mohammed H. , Kanlikilicer Pinar , Rodriguez Aguayo Cristian , Kabil Nashwa N. , Pichler Martin , Bayraktar Recep , Bayraktar Emine , Ivan Cristina , Mitra Rahul , Calin George A. , Sood Anil K. , Abd-Ellah Mohamed F. , Helal Gouda K. , Lopez Berestein Gabriel 
Published: July 2016

Abstract
Exosomes have emerged as an important mediator of diverse biological functions including tumor cell progression, invasion, immune escape, and cell-to-cell communication, through the release of molecules such as mRNAs, microRNAs, and proteins. Ovarian cancer (OC) is one of the lethal cancers with extensive local invasion, metastasis, and poor diagnosis. Thus, finding novel targets for OC therapy are urgently needed. Here, we isolated 30-140 nm exosomes from the supernatant of one normal and six different OC cells. In addition, RNAs were isolated from cells and exosomes, and profiles of two miRNA fractions were obtained using affymetrix microarray analysis. By comparing signal intensities of microarray data and validation using RT-PCR analysis, we found that miR-940 was abundant in exosomes from SKOV3IP1, HeyA8, and HeyA8-MDR. Ectopic expression of miR-940 inhibited proliferation, colony formation, invasion, migration, induced G0/G1 cell cycle arrest, and apoptosis in OC. Overexpression of miR-940 also inhibited tumor cell growth in vivo. The target gene of miRNA-940 and the downstream pathway were further investigated using several target prediction algorithms. We identified specific targeting sites for miR-940 in the 3’-untranslated region (3’-UTR) of SRC. We then experimentally validated miR-940 as a direct regulator of SRC using cell transfection and luciferase assays, and showed that miR-940 inhibited SRC expression at mRNA and protein levels. Following this reduction, the activity of proteins downstream of SRC, such as FAK, paxillin and Akt were also reduced. Collectively, our results suggest that OC cells selectively secreted the tumor suppressive miR-940 into the extracellular environment via exosomes, to maintain their invasiveness and tumorigenic phenotype.
Citation Format: Mohammed H. Rashed, Pinar Kanlikilicer, Cristian Rodriguez Aguayo, Nashwa N. Kabil, Martin Pichler, Recep Bayraktar, Emine Bayraktar, Cristina Ivan, Rahul Mitra, George A. Calin, Anil K. Sood, Mohamed F. Abd-Ellah, Gouda K. Helal, Gabriel Lopez Berestein. Ovarian cancer cells selectively release exosomes containing tumor suppressor miRNAs to maintain SRC-mediated oncogenic activities. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-169.
Abstract LB-171: Repression of miR-125b-1 by epigenetic mechanisms in breast cancer cell lines
Authors: Cisneros-Soberanis Fernanda , Andonegui Marco Alonso , Castro Clementina , Herrera Luis Alonso 
Published: July 2016

Abstract
miR-125b-1 downregulates targets as ERBB2, BAK1 and ETS1. These targets are involved in cell proliferation, apoptosis and cell migration, respectively. Previous studies on tumor cells reveal that downregulation of miR-125b-1 is associated with poor prognosis in breast cancer patients. DNA methylation of the miR-125b-1 promoter can repress its expression, in addition, this promoter is embedded in an intermediate CpG island thus, DNA methylation and histone modifications could also affect its transcription. Repression by DNA methylation has been well characterized, but there is no information about the role of histone modifications in the regulation of miR-125b-1 promoter. We evaluated the enrichment of two histone modifications involved in gene repression, H3K9me3 and H3K27me3, on the miR-125b-1 promoter of two breast cancer cell lines, a luminal A, MCF 7, and a triple negative, MDA-MB-231, compared with a non-transformed breast cell line, MCF 10A. We found that breast cancer cell lines are enriched with H3K27me3 and H3K9me3 in MCF 7 and MDA-MB-231, respectively. Then, we focused on reactivating miR-125b-1 in MCF 7 using an EZH2 inhibitor. After the treatment with the EZH2 inhibitor, we evaluated the transcriptional levels of the pri-miR-125b-1 and the mature miR-125b by qRT-PCR. Our results suggest that transcripts, pri-miRNA and mature miRNA, increase their expression levels after the treatment in the MCF7 cell line, but not in the MDA-MB-231 and MCF 10A cell lines. Subsequently, we evaluated the BAK1 expression and protein levels to investigate whether the miR-125b-1 reactivation could affect some targets. We observed a 60% and 70% decrease in the expression and protein levels of after treatment with the EZH2 inhibitor. To determine if the H3K9me3 is involved on miR-125b-1 silencing in MDA-MB-231, we over-expressed KDM4B/JMJD2B to reactivate this miRNA. Then, we evaluated the transcript. A three-fold increase was observed compared. We conclude that the miR-125b-1 can be repressed by different epigenetic mechanisms depending on the breast cancer subtype; the miR-125b-1 reactivation by removing the repression histone modification marks affect the expression of BAK1, a pro-apoptotic target.
Citation Format: Fernanda Cisneros-Soberanis, Marco Alonso Andonegui, Clementina Castro, Luis Alonso Herrera. Repression of miR-125b-1 by epigenetic mechanisms in breast cancer cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-171.