bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2134: Unique and redundant roles of human RecQ homologs in cellular response to oxidative DNA damage
Authors: Sharma Sudha , Phatak Pornima , Stortchevoi Alexei , LaRocque Jeanine , Jasin Maria 
Published: August 2012

Abstract
RecQ helicases contribute diverse activities towards genome maintenance in response to a variety of DNA lesions. Human RecQ homologs include RECQ1, BLM, WRN, RECQL4, and RECQ5α. Although these RecQ proteins are similar in their catalytic core and share certain biochemical properties in vitro, mutations in BLM, WRN and RecQ4 lead to clinically distinct diseases of cancer predisposition. This suggests that each human RecQ protein functions in distinct molecular events, but their specialized functions are only vaguely understood. RECQ1 is the most abundant but poorly characterized RecQ homolog in humans. Biochemically, RECQ1 displayed distinct substrate specificities from WRN and BLM, indicating that these helicases likely perform non-overlapping functions. Cellular studies imply that RECQ1 is involved in cellular proliferation and maintenance of genomic stability. We have obtained key preliminary evidence suggesting a unique role of RECQ1 in repair of oxidative DNA damage. RECQ1 is quickly recruited to the chromatin when cells are exposed to hydrogen peroxide (H2O2). Remarkably, the chromatin localization of RECQ1 is more robust and rapid than that of WRN helicase which has been shown to function in oxidative DNA damage repair. Deficiency in WRN or BLM helicase result in reduced homologous recombination and over-activation of PARP under basal condition; however, RECQ1-deficiency did not lead to PARP activation in undamaged cells and resulted in a comparatively modest, but significant, reduction in relative homologous recombination repair. In stark contrast to what is seen in WRN-deficiency, RECQ1-depleted cells over-activate PARP in a specific response to H2O2 treatment. Nonetheless, similar to WRN, RECQ1 associates with PARP-1 in human cells. Our results suggest a novel and non-overlapping role of RecQ1 in exogenously induced-oxidative DNA damage repair via modulation of PARP-1. Given that several RecQ proteins exhibit interaction with PARP-1, this study should provide a paradigm to delineate specialized and redundant functions of human RecQ homologs in DNA repair mechanisms.
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 2134. doi:1538-7445.AM2012-2134
Abstract 2135: Proline, glutamic acid, leucine rich protein 1 (PELP1) is essential for optimal p53-mediated DNA damage response
Authors: Nair Binoj C. , Krishnan Samaya R. , Sareddy Gangadhara R. , Mann Monica , Xu Bo , Natarajan Mohan , Tekmal Rajeshwar Rao , Vadlamudi Ratna K. 
Published: August 2012

Abstract
DNA Damage Response (DDR) is a vital ameliorative action undertaken by cells against various intrinsic and extrinsic genotoxic agents. p53 is an important transcription factor that plays a critical role in mediating cell cycle arrest or apoptosis upon DNA damage. PELP1 is a proto-oncogene and scaffolding protein that functions as a coregulator for a number of nuclear receptors such ERα and transcription factors such as E2F1. In this study, we discovered that PELP1 plays a vital role in p53-mediated DNA damage response. Using p53 wild-type breast cancer cells and PELP1-specific shRNAs, we show that cells lacking PELP1 are less sensitive to various genotoxic agents including etoposide, cisplatin, camptothecin or α-irradiation. PELP1 interacts with p53 upon DNA damage and ChIP analysis revealed that PELP1 is recruited to p53 target gene promoters. Reporter gene assays demonstrated that PELP1 functions as a coactivator of p53 and is required for optimal activation of p53 target genes under genomic stress. Mechanistic studies revealed that resistance to cell death in PELP1-depleted cells upon genotoxic stress was due to significant decrease in expression of p53 target genes. Furthermore, we demonstrated that PELP1 is phosphorylated at Serine 1033 upon DNA damage. Using a novel phospho-specific PELP1 antibody that specifically recognizes phosphorylated Serine 1033 on PELP1, we show that various genomic insults can induce PELP1 phosphorylation in vivo. Using cell lines that are either proficient or deficient in DDR kinases like ATM, ATR or DNAPKc, we have also established that PELP1 is phosphorylated by all three kinases depending on the type of DNA damage. Interestingly, we also found that the phosphorylation of PELP1 at Ser-1033 is important for optimal p53's transcriptional functions and that the phosphorylated form of PELP1 is recruited to the site of DNA damage when analyzed by laser micro-irradiation and confocal imaging, suggesting a potential role of PELP1 in the DNA repair process. Overall, these studies established a previously uncharacterized role of PELP1 in DNA damage response. Since PELP1 is as proto-oncogene with deregulated expression in many cancers, these findings will have implications in our understanding of cancer progression and 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 2135. doi:1538-7445.AM2012-2135
Abstract 2137: Using Rac1 isogenic cells to model tumor metastasis
Authors: Wiggins Ceri , Astley Holly , Mahoney Claire , Sorrell David , Torrance Chris , Foster Rebecca 
Published: August 2012

Abstract
The Rho family of GTPases regulate a wide range of normal cellular functions including cell growth and cytoskeleton dynamics, but it is becoming increasingly apparent that when deregulated, proteins such as Rac1 contribute to tumorigensis, tumour invasion and metastasis. Overexpression of Cdc42 and Rac1 have been reported in human breast cancer, and coincide with breast cancer progression, metastasis and resistance to chemotherapy. The aim of this study was to generate a model system to investigate how Rac1 activation affects the migratory propensity of human breast epithelial cells. We utilised X-MAN isogenic cells derived from MCF10A mammary epithelial cells which harbour a single Q61L Rac1 mutation introduced by AAV-mediated homologous recombination, paired with a parental cell line expressing the wildtype allele. This system offers several advantages over conventional methods; protein expression is driven from endogenous promoters, thereby eliminating the caveats associated with transfection-based approaches. Using the X-MAN isogenic cells we showed that introduction of the Rac1Q61L mutation results in a profound effect on cell morphology. The most striking phenotype was the appearance of large intracellular vacuoles, but immunofluorescence studies also revealed cytoskeletal abnormalities with Rac1Q61L cells showing evidence of microtubule disorganisation and accumulation of newly polymerised actin fibers. These observations, in conjunction with previous reports that activated Rac is associated with cell migration, prompted us to address whether these cells may also have a migratory phenotype. Using Transwell and scratch assays, we confirmed that Rac1Q61L cells are more motile than their parental counterparts, and this correlated with increased adhesive properties. Pathway analysis revealed Rac1Q61L cells express higher basal levels of activated MEK and ERK, both of which have been implicated in the migration of numerous cell types. In conclusion, we have generated a pair of isogenic cell lines to demonstrate how constitutive Rac1 activation results in cytoskeletal changes and increased motility. Our data highlights the advantages of being able to study clinically-relevant pathways in a phenotypically-relevant assay, and how this platform could be exploited to profile molecularly targeted agents aimed at reducing tumour invasion and metastasis.
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 2137. doi:1538-7445.AM2012-2137
Abstract 2140: Regulator of G-protein signaling 2 blunts cellular viability mediated by a stabilized lysophosphatidic acid analogue (2S-OMPT) in the presence of chemotherapy in an ovarian cancer cell model of chemoresistance
Authors: Altman Molly K. , Ali Mourad W. , Callihan Phillip C. , Hooks Shelley B. , Murph Mandi M. 
Published: August 2012

Abstract
Lysophosphatidic acid (LPA) enhances growth, survival, viability and proliferation in numerous models. Thus, the receptors for LPA are also implicated in oncogenic signaling and represent a group of “druggable” therapeutic targets in cancer. Regulator of G protein Signaling 2 (RGS2) is a GTPase activating protein (GAP) that deactivates the G alpha subunits of heterotrimeric G proteins, turning off G protein-coupled receptor (GPCR) signaling. In our previous studies examining computational bioinformatics, we demonstrated that reduced RGS gene expression develops with the occurrence of drug resistance in ovarian cancer cell lines. The purpose of our study was to investigate whether the LPA receptors are also involved in mediating viability as a result of enhanced GPCR signaling due to reduced RGS proteins in this chemoresistance model. This is important since RGS proteins can deactivate G alpha subunits of many different GPCRs, and are not specific to merely the LPA receptors. If a “druggable” GPCR is mediating viability in chemoresistance, it is critical to identify which ones are responsible. To test this idea we used the metabolically stabilized LPA analogue L-sn-1-O-oleoyl-2-O-methylglyceryl-3-phosphothionate (2S-OMPT) as a potent non-hydrolyzable agonist for LPA receptors at a concentration (10 µM) sufficient to activate multiple LPA receptors. We hypothesized that if LPA signaling was not involved, then OMPT would override any contribution of RGS2 on modulating the viability response in the presence of chemotherapy. Using a tet-off promoter system, we generated an inducible stable model of RGS2-expressing HeyA8-MDR cells, which we have previously confirmed are resistant to taxanes. After 48 h OMPT pre-treatment, HeyA8-MDR-RGS2-inducible cells were exposed to cisplatin for 24 h and evaluated for viability. IC50 values for cisplatin were lower in the RGS2-induced HeyA8-MDR cells that were not pretreated with OMPT, a demonstration of enhanced sensitivity to cisplatin in the presence of RGS2. All conditions pre-treated with OMPT demonstrated enhanced viability even in the presence of chemotherapy; however, ovarian cancer cells that were pretreated with OMPT and cultured in tet-free medium to induce RGS2 expression showed a significant blunting of viability. This supports the interaction between LPA receptors and RGS2 in the control of drug sensitivity in ovarian cancer chemoresistance and provides a mechanism for our current and previous observations.
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 2140. doi:1538-7445.AM2012-2140
Abstract 2141: cAMP/PKA signaling enhances activity of Deleted in Liver Cancer 1 (DLC1) tumor suppressor in suppressing liver cancer tumorigenesis
Authors: Ko Chi Fat , Chan Lo Kong , Tse Edith Yuk-Ting , Yeung Yin-Shan , Sze Karen Man-Fong , Ng Irene Oi-Lin , Yam Judy Wai Ping 
Published: August 2012

Abstract
Deleted in Liver Cancer 1 (DLC1) which encodes a RhoGTPase-activating protein (RhoGAP) is a tumor suppressor frequently inactivated in a wide spectrum of human cancers. The RhoGAP activity has been shown to play a predominant role in the biological activities of DLC1. It has been shown that cells with silenced DLC1 exhibit increased active RhoA level. This finding provides evidence about the activation of RhoA as the consequence of deregulated DLC1 and points to the importance of RhoGAP activity in the biological activity of DLC1. In this regard, it is important to comprehend how RhoGAP activity of DLC1 is related. Here, we show that DLC1 was robustly phosphorylated by cyclic AMP (cAMP)/Protein kinase A (PKA) signaling in cells. Phosphorylation of DLC1 was enhanced by forskolin, a known activator of PKA while suppressed when H-89, an inhibitor of PKA was added. Direct phosphorylation of DLC1 by PKA was further confirmed by the in vitro kinase assay. Using specific phospho-DLC1 antibodies, PKA was shown to phosphorylate DLC1 at S431 and S549. Functional assays demonstrate that phosphorylation at S549 plays a critical role in provoking the inhibitory activity of DLC1 in suppressing growth and motility of Ras-transduced p53 null mouse hepatoblasts. When compared with the stable clone of wild-type DLC1, stable clone of DLC1 phosphomimetic mutant, S549D, displayed a largely reduced growth of subcutaneous and orthotopic liver implanted tumors and an enhanced apoptosis. The migration and invasion rates of S549D cells were also significantly inhibited. Furthermore, S549D expression abolished stress fiber formation but failed to alter filopodia protrusions. These functional effects exerted by S549D were ascribed to the enhanced RhoGAP activity against RhoA. To further investigate the mechanism through which the RhoGAP activity is enhanced, we found that DLC1 dimerized upon S549 phosphorylation. Our findings have revealed for the first time about the regulation of RhoGAP activity of DLC1 via dimerization. Our study suggests a molecular link between PKA and DLC1/Rho pathways and underscores the importance of S549 phosphorylation in the regulation of RhoGAP activity of DLC1. (This study was funded by the Small Project Funding Program, The University of Hong Kong 200907176125)
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 2141. doi:1538-7445.AM2012-2141
Abstract 2146: The Rho GTPase RhoE is a p53-regulated candidate tumor suppressor
Authors: Bi Feng , Zhu Yajie , Tang Qiulin 
Published: August 2012

Abstract
Rho family proteins are prominent members of the well-known Ras superfamily and are deeply involved in almost all the malignant behaviors of cancer. As Small GTPases, Rho proteins can cycle between active GTP-bound state and GDP-bound state by regulating of GEFs, GAP and GDI. RhoE is a unique member of Rho family proteins that can bind but do not hydrolyze GTP, thus remain constitutively active upon expression without the need of regulation by the GTP/GDP conformational changes of other Rho GTPases. Previous studies have shown that RhoE may play a role opposite that of RhoA in regulating cell proliferation. Here, for the first time, we systematically investigate the expression patterns of RhoE by systemic immunocytochemistry analysis of 74, 32, 62, and 34 gastric, colorectal, lung, and breast carcinomas, respectively, and found that RhoE protein level was significantly decreased in most cancer cases compared with that of adjacent normal tissues. RhoE expression also appeared to inversely correlate with the clinical grade of gastric, colorectal, lung cancer tissues. Increasing RhoE expression in MKN45, SW480, HepG2 and SPCA1 cancer cell lines that have relatively low level of endogenous RhoE could markedly inhibit proliferation, migration and invasion activities and induced apoptosis of the cancer cells. Interestingly, p53 transcription activity was reduced in these RhoE under-expressed cancer cells that contain p53 mutations, and increasing p53 activity significantly increased RhoE expression in the cells. Significantly, p53 transcription activity, measured by the p53-responsive p21Cip1, MDM2, and GADD45 expressions, paralleled RhoE expression in gastric cancer tissues. Thus, RhoE may participate in human cancer progression as a candidate tumor suppressor under the regulation by p53. This work also enriches our knowledge in the role of small G protein network in cancer.
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 2146. doi:1538-7445.AM2012-2146
Abstract 2148: Exploitation of androgen receptor splice variant signaling by guanine nucleotide exchange factor Vav3 in castration resistant prostate cancer
Authors: Peacock Stephanie , Fahrenholtz Cale , Burnstein Kerry L. 
Published: August 2012

Abstract
The treatment for advanced or metastatic prostate cancer is androgen deprivation therapy. Patients inevitably relapse and the cancer is now termed androgen-independent or castration resistant (CRPC). CRPC remains dependent on androgen receptor (AR) signaling. One of the proteins implicated in the reactivation of AR transcriptional activity in CRPC is Vav3, a Rho GTPase guanine nucleotide exchange factor. Vav3 is up-regulated in human prostate cancer tumors compared to benign tissue and in preclinical models of prostate cancer progression to CRPC. Vav3 enhances AR activity at both physiological and as well as at subnanomolar androgen concentrations, similar to prostatic microenvironment levels demonstrated in CRPC. Vav3 confers castration resistant growth to a classically androgen dependent cell line in a mouse xenograft model. Thus, elevated levels of Vav3 seem to be pivotal in promoting continued AR signaling in CRPC. We examined the contributions of Vav3 to AR activity and cell proliferation in the CRPC cell lines CWR-22Rv1 and CWR-R1. Knockdown of Vav3 attenuated cell growth and reduced AR activity as compared to the shGFP control. However knockdown of full length AR had little effect, perhaps due to impaired ligand-mediated transcriptional activity of the mutated AR expressed in these cell lines. Because CWR-22Rv1 also express AR splice variants that lack the ligand binding domain and are proposed to underlie CRPC growth, we examined the possibility that Vav3 enhances AR splice variant signaling. The AR splice variant, ARV7 (also known as AR3), exhibits constitutive ligand independent activity and is linked to poor prognosis and survival. Depletion of ARV7 in 22Rv1 and CWR-R1 cell lines resulted in slowed growth and lowered AR activity. Soft agar assays revealed that knockdown of either Vav3 or ARV7 resulted in greatly decreased anchorage independent growth. Vav3 potently enhanced the activity of ARV7 in reporter gene assays. Further, knockdown of Vav3 resulted in lowered levels of nuclear AR splice variants in CWR-22Rv1. Co-immunoprecipitation revealed that ARV7 and Vav3 directly interact. These results suggest that Vav3 may enhance ARV7 activity through increased nuclear localization and that the interaction of Vav3 and ARV7 may be required for robust growth of CRPC cells. These novel data demonstrating interaction between a versatile AR coactivator and an AR splice variant provide insights into the possible mechanisms by which Vav3 exploits and enhances AR splice variant signaling in the progression of prostate cancer malignancy and castration resistance.
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 2148. doi:1538-7445.AM2012-2148
Abstract 2154: CDCP1 links RAS and Src signaling pathways as a common effector for the promotion of tumor metastasis
Authors: Sakai Ryuichi , Uekita Takamasa 
Published: August 2012

Abstract
The oncogenic RAS is one of the most intensively studied proteins which are well recognized as a master regulator of cancer initiation and progression, however rather limited information is available as for their contribution to the cell properties associated with tumor metastasis such as anoikis resistance, cell migration and invasion. We have revealed that CUB domain-containing protein 1 (CDCP1) protein, a substrate of Src family kinase (SFK), in solid cancers is involved in the regulation of anoikis resistance, cell migration and invasion. CDCP1 contributes significantly to the metastatic potential of various cancers including lung, stomach, and pancreatic cancers in a tyrosine phosphorylation dependent manner. It was recently observed that human lung cancer cell lines with K-RAS mutations show significantly higher expression of CDCP1 than those without, while the other common mutations such as EGFR, LKB1 and p53 did not show such relationship. The introduction of the activating mutation of K-RAS clearly induced the expression of CDCP1 and that this enhancement is also affected by the expression levels of Myc protein. Treatment of PD98059, an inhibitor of MEK downstream of Ras, as well as expression of dominant-negative Ras, reduced the expression of CDCP1, and at the same time suppressed cell survival in suspension culture, cell migration and invasion. However, these properties were rescued only when both CDCP1 and Fyn, a member of SFKs were expressed. On the contrary, metastatic potentials caused by expression of activated K-Ras in lung cancer cells was blocked by knockdown of in CDCP1 expression induced by Ras. Using three dimensional organotypic culture assay of human cervical keratinocytes (HCKs) which mimics in vivo tissue invasion of cervical cancers, marked expression of CDCP1 was detected at the site of cell invasion into the collagen raft. The treatment of CDCP1 siRNA or SFKs inhibitor PP2 repressed cell invasion into the collagen raft induced by Ras and Myc. As a summary, it was revealed that expression of CDCP1 is induced by oncogenic Ras, and upregulated CDCP1 triggers cancer invasion and metastasis when phosphorylated by SFKs. Metastatic potential induced by Ras is dependent on the CDCP1 induction, while CDCP1 is not responsive for proliferative change also induced by Ras. These findings demonstrated the central role of CDCP1 as the functional link between RAS and SFKs signaling during the progression of human malignant tumors.
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 2154. doi:1538-7445.AM2012-2154