bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 2157: A novel role for Giα proteins in differentially regulating activation of RTK-mediated signaling
Authors: Chu Wen-Ming , Wang Zhanwei , cruz Rica Dela , Chu Catherine , Zhang Jianhua , Jiang Meisheng 
Published: August 2012

Abstract
The activation of the extracellular-signal-regulated protein kinase (ERK) pathway and the PI3K/Akt/mTORC pathway by growth factors is mediated by the receptor tyrosine kinases (RTKs), and plays a crucial role in physiological and pathological processes including cell proliferation, growth, survival, migration, tumorigenesis and metastasis. We previously reported that the activation of the PI3K/Akt/mTORC1 in mouse embryonic fibroblasts (MEFs) by epidermal growth factor (EGF) and its family growth factors is mediated by the heterotrimeric G protein alpha inhibitory (Giα). Herein we demonstrated that Giα proteins are able to differentially regulate RTKs-mediated activation of the ERK and the Akt/mTORC1 pathways. Loss of Giα proteins in MEFs impaired activation of the ERK pathway by EGF, insulin-like growth factor (IGF) and Insulin, but not basic fibroblast growth factor (bFGF). Intriguingly, while activation of the Akt/mTORC1 pathway by EGF and bFGF was severely defective in Giα protein deficient cells, this activation was only slightly reduced in response to insulin and IGF. Also, Giα proteins were able to alter activation of the Akt/mTORC1 and the ERK pathways by serum and platelet-derived growth factor (PDGF) in a dose dependent manner. To further understand that how Giα proteins differentially regulate RTK-mediated activation of the Akt/mTORC1 and ERK pathways, we performed an immuno-precipitation study. Our results showed that growth factors were able to induce the association of Giα proteins with growth factor receptors and their downstream adaptor proteins. Loss of Giα proteins in MEFs impaired the association of growth factor receptors with their adaptor proteins indicating that Giα proteins act downstream of RTKs but upstream of the adaptor proteins. Finally, we examined a role of Giα proteins in cancer biology. Similar to results obtained from Giα deficient MEFs, knockdown of Giα proteins in several human cancer cell lines diminished activation of the Akt/mTORC1 and the ERK pathways by growth factors. As a result, Giα protein deficiency inhibited cancer cell growth and migration. Given the fact that growth factors and their receptor pathways play pivotal roles in tumorigenesis and metastasis of cancer, our findings may promote further understanding the molecular mechanism underline RTK signaling regulation in cancer biology and may have implications for cancer therapy. Supported by Department of Defense, Leukemia and Lymphoma Society and NIH.
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 2157. doi:1538-7445.AM2012-2157
Abstract 2163: RSK signaling in HER2-positive breast cancer cells
Authors: Fink Marc Y. , Singh Shawn , Cho Yohan , Mestry Daksha 
Published: August 2012

Abstract
Heregulin (HRG) is a soluble growth factor involved in the control of proliferation, survival, invasion, and differentiation of normal and malignant mammary epithelial cells. HRG binds its receptor, HER3, leading to activation of the HER2-HER3 heterodimer, which acts as an oncogenic factor in breast cancers. Pharmacological inhibitors to HER2 are currently being used in the clinic to treat HER2-positive breast cancer, however, they are associated with resistance after one year of therapy. A more comprehensive understanding of the signaling network downstream of HRG, in HER2-positive breast cancer cells, will be crucial for further development of inhibitors that do not elicit resistance. This study assessed HRG signaling in the HER2-positive breast cancer cell lines BT474 and SKBR3. The RSK (p90 ribosomal S6 Kinase) pathway was activated in an ERK-dependent manner. HRG stimulation increased phosphorylation of RSK at S380, T359, and S363. HRG stimulated the phosphorylation of CREB (cAMP Response-Element Binding Protein), an established substrate of RSK, at S133 and this was blocked by pharmacological inhibition of RSK. HRG induced the expression of c-FOS in an RSK-dependent manner. These data demonstrate that RSK has an important role in transducing HRG signaling to the gene expression program and suggest that inhibitors of RSK may be useful in the treatment of HER2-positive breast 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 2163. doi:1538-7445.AM2012-2163
Abstract 2186: Function and regulation of Polo-like Kinase 3 in human pancreatic cancer
Authors: Li Zhongkui , Chang Zhe , Chiao Paul J. 
Published: August 2012

Abstract
Pancreatic cancer is currently the fourth leading cause of cancer death in the United States. Despite the recent advances in pancreatic cancer research, patients with this devastating disease still have a poor prognosis. Therefore, deciphering pancreatic cancer-related gene expression and defining the individual gene's specific functions will make a significant impact on the diagnosis and treatment of pancreatic cancer. Recently, our lab has demonstrated the tumorigenic transformation in an immortalized pancreatic cell line, HPNE/hTERT by sequential introduction of multiple genetic alterations. We found that Polo-like kinase 3 (Plk3) is significantly down-regulated in transformed tumor cell lines. Plk3 belongs to the Polo-like kinase family and is a multi-functional kinase. We previously reported that Plk3 played a pro-apoptotic role in pancreatic cancer lines when it was overexpressed. Plk3 down-regulation in transformed HPNE cells suggests that Plk3 may have tumor suppression function during pancreatic tumor development. In addition, we found Plk3 expression is regulated by Pten. In Pten-knockout MEF cells, Plk3 expression was significantly down-regulated. So Plk3 may be downstream of Pten in the tumor suppression pathway. These data suggest that Plk3 play an important role in pancreatic cancer development.
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 2186. doi:1538-7445.AM2012-2186
Abstract 2189: Novel transcriptional regulation of Notch1 by EZH2 in mammary stem cells
Authors: Gonzalez Maria E. , Li Xin , Kruger Heather , Toy Kathy , Kleer Celina G. 
Published: August 2012

Abstract
Background: EZH2 has oncogenic functions in the breast and other organs, and has been recently shown to regulate the differentiation of tissue specific stem cells. However, the underlying mechanisms are largely unknown. We hypothesized that EZH2 may regulate mammary stem cells by transcriptional mechanisms of key signaling pathways. Methods: We developed EZH2 KD in SUM149 breast cancer cells, and an inducible and transient cell culture model of EZH2 overexpression, (EZH2-OV), and its deletion mutants in MCF10A and in primary breast cells. Mammary stem cells were identified using ALDH1+ and CD44+/CD24- by FACS. ChIP assays were used to determine EZH2 recruitment to specific areas in NOTCH1 promoter. Ectopic expression of EZH2 and deletion mutants leads to identify the EZH2 domain responsible for the transcription up regulation of NOTCH1. Results: We identified that EZH2 KD in SUM149 significantly decreased NOTCH1 signaling in the stem cell population. We observed preferential expression of EZH2 in the stem cell population of normal primary breast cells compared to non-stem cells. In MCF10A cells, EZ-OV was predominantly increased in the ALDH-1+ population. We found that EZH2-OV increased the stem cell population of MCF10A cells. Consistently, EZH2-OV in MCF10A and primary breast cells increased Notch1 mRNA specifically in the ALDH1+ population. EZH2-OV increased Notch1 protein levels and promoter activity in MCF10A and primary cells. Mechanistically, Notch1 inhibition by GSI reversed the effect of EZH2-OV in the stem cell population of MCF10A cells. ChIP assays revealed that EZH2 is recruited to specific regions of the NOTCH1 promoter depending on EZH2 specific context. Moreover, ChIP assays with EZH2 deletion mutants identify that the Nter- EZH2 HII domain is responsible for the NOTCH1 promoter transcriptional up regulation and that this function is independent of the SET domain (methytransferase activity) and as shown by comparing the EZH2 tri-methylation mark (3H3K27) in the NOTCH1 promoter. Conclusion: Collectively, these results indicate that EZH2 regulates mammary stem cells and requires, at least in part the activation of Notch1 signaling by recruitment of EZH2 to the NOTCH1 promoter through the Nter domain.
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 2189. doi:1538-7445.AM2012-2189
Abstract 2212: C-terminus-truncated hepatitis B virus X protein enhances cell invasiveness in hepatocellular carcinoma
Authors: Sze Karen Man-Fong , Chu Glanice Kin-Yan , Ng Irene Oi-Lin 
Published: August 2012

Abstract
Hepatocellular carcinoma (HCC) is the fifth of major malignancies worldwide and chronic hepatitis B virus (HBV) infection is one of its well known risk factors. Random integration of the HBV DNA into host genome is frequent in human HCCs and this leads to truncation of the HBV DNA, particularly at the C-terminal end of the HBV X protein (HBx). In this study, we investigated the frequency of this C-terminal truncation of HBx in human HCCs and its functional significance in HCC cells. In the 51 HBV-positive patients with HCC, full-length HBx was detected in all of the non-tumorous livers. Interestingly, natural COOH-truncated HBx was found in 47% tumours. Upon clinicopathological analysis, presence of natural COOH-truncated HBx significantly correlated with the presence of venous invasion, a hallmark of metastasis (p &lt; 0.01). Doxycycline- inducible stable expression of the full-length HBx and C-terminal truncated forms of HBx in HepG2 cells was employed for in vitro cell invasion assay and cell signalling analysis involved in cell invasiveness. Inducible expression of COOH-truncated HBx protein (with 24 amino acids truncated at C-terminal end) in HepG2 cells enhanced cell invasiveness, and C-Jun transcriptional activity, and increased MMP10 transcription production, as compared with the full-length HBx. The activation of the MMP10 promoter by the COOH-truncated HBx was abolished when the AP-1 binding sites were mutated. Our data suggest that COOH-truncation of HBx may play a significant role in enhancing cell invasiveness and metastasis in HCC, possibly via activation of the MMP10 through C-Jun signaling pathway. (This study was supported by a Hong Kong Government RFCID grant 05050022)
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 2212. doi:1538-7445.AM2012-2212
Abstract 2215: Glucocorticoid receptor function is essential for SOCS2-mediated negative regulation of hepatic GHR signaling
Authors: Mueller Kristina M. , Kornfeld Jan-Wilhelm , Schuetz Guenther , Moriggl Richard 
Published: August 2012

Abstract
GHR signaling plays an essential role in somatic growth and development as well as in the maintenance of metabolic homeostasis. Target tissue responsiveness to GH is dependent on postreceptor mechanisms to circumvent unphysiological and off-target effects due to prolonged GHR activation. GHR signals amongst others through the JAK2/STAT5 pathway. SOCS2, a GH-STAT5-regulated gene, is a key negative regulator of GHR sensitivity. Transcription of distinct GH-STAT5-dependent gene subsets requires coactivator function of the glucocorticoid receptor (GR). This mechanism was shown to involve direct binding of GR to the STAT5 N-terminus. Earlier studies have implied that regulation of SOCS2 also requires synergistic action of STAT5 and GR. Therefore, our aim is to investigate the molecular interaction between STAT5 and GR to regulate SOCS2 expression. Hepatocyte-specific deletion of the GR causes reduced hepatic Socs2 mRNA expression approximately to the same extent as STAT5-deficient livers. Furthermore, STAT5 activity was increased and prolonged in GR-deficient livers upon exogenous GH administration. Genes which are dependent on functional STAT5-GR protein interaction often harbor potential STAT5 oligomer binding sites in their promoter regions. Using bioinformatic screening, we found three STAT5 oligomer binding sites in the murine distal Socs2 promoter region. First, binding of activated STAT5 to the putative binding sites was confirmed by DNA binding assays. Subsequently, we performed transactivation studies using a luciferase reporter construct containing the relevant region of the Socs2 promoter and an additional 3′ region to assess the requirement for putative enhancer sequences. Maximum luciferase activity was observed in the presence of activated STAT5b and GR only. However, this pronounced transactivation was severely impaired upon transfection of the aminoterminally truncated STAT5 isoform (STAT5ΔN). Additionally, direct physical interaction of activated STAT5 and GR on the Socs2 promoter was detected in GH/dexamethasone-treated control livers by re-ChIP assays. We demonstrate that full Socs2 transactivation requires STAT5-GR protein-protein interaction in hepatocytes. As the liver represents a primary site of GH-mediated STAT5 activation, deregulated GR signaling could lead to imbalanced liver GH sensitivity due to aberrant SOCS2-mediated feedback inhibition.
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 2215. doi:1538-7445.AM2012-2215
Abstract 2219: Mechanism of trancriptional repression by EWS/FLI in Ewing's sarcoma
Authors: Sankar Savita , Lessnick Stephen L. 
Published: August 2012

Abstract
Objective: Ewing's sarcoma is a highly aggressive bone-associated malignancy affecting children and young adults with most cases harboring a somatic translocation that encodes the EWS/FLI oncoprotein. EWS/FLI is an aberrant transcription factor. Most studies indicate that EWS/FLI functions as a transcriptional activator. However, recent genome-wide transcriptional studies have raised the possibility that EWS/FLI may also repress target genes, although the mechanistic basis for this repression is unknown. We sought to test the hypothesis that EWS/FLI functions as a direct transcriptional repressor at some genetic loci, and that transcriptional repression is required for the oncogenic function of EWS/FLI. Furthermore, we sought to define relevant domains and corepressors that are involved in this activity. Methods: RNAi based microarray combined with genome-wide ChIP-Chip analyses were used to identify direct repressed target genes of EWS/FLI. Soft agar and xenograft tumor formation assays were performed to assess oncogenic transformation. Deletion mutants of EWS/FLI were constructed and used to map the repression domain. Co-immunoprecipitations were performed to validate the interaction of EWS/FLI with transcriptional co-repressors. Luciferase reporter assays and gel shift assays were utilized to characterize the binding site for EWS/FLI at repressed gene promoters. Results: We identified a subset of EWS/FLI-repressed target genes that are directly bound by the protein. Using these target genes, we identified domains in EWS/FLI necessary and sufficient for repression. Interestingly, these repression domains are also necessary for oncogenic transformation. We identified two HDACs that are involved in this repression, and identified a likely candidate transcriptional repression complex that binds EWS/FLI and contributes to its repressive function. Finally, we found that transcriptional repression is absolutely required for the oncogenic function of EWS/FLI, as two downregulated targets function as suppressors of Ewing's sarcoma oncogenesis. Conclusion: Transcriptional deregulation by EWS/FLI is a key oncogenic event in Ewing's sarcoma pathogenesis. Our data demonstrated that, in addition to transcriptional activation, EWS/FLI mediated transcriptional repression is also critical in Ewing's sarcoma oncogenesis. This is the first time that a detailed molecular mechanism of EWS/FLI mediated direct repression is reported, and has important implications for therapeutic targeting of EWS/FLI in Ewing's sarcoma.
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 2219. doi:1538-7445.AM2012-2219
Abstract 2231: The over-activation of Akt1 oncogene heightens the Glypican-3 (GPC3) effects on metastatic progression of murine mammary tumor cells
Authors: Romero Silvina A. , Huvelle Maria A. Lago , Peluffo Guillermo D. , de Kier Joffe Elisa Bal , Urtreger Alejandro J. , Peters Maria G. 
Published: August 2012

Abstract
It is known that Akt kinases 1, 2 and 3 have critical roles in regulating survival, metabolism and other cellular activities. However, their functions on migratory potential and metastasis development are less clear. GPC3 is a proteoglycan downregulated in breast tumors. We have previously shown that GPC3 reexpression inhibits metastatic capacity in vivo of the LM3 murine mammary adenocarcinoma cells. Moreover, this phenomenon was associated with a partial reversion of the epithelial-to-mesenchymal transition as shown in vitro. On the other hand, we have also determined that GPC3 modulates Akt signaling pathway in LM3 cells. The aim of this work was to investigate the role of Akt1 on the invasive/metastatic behavior of GPC3 reexpressing cells. First, we have confirmed that LM3-GPC3 cells present higher Akt1 levels than LM3-vector ones by western blot. To elucidate the function of this isoform, LM3-GPC3 clones were infected with viruses carrying a constitutively active variant of Akt1 (CA Akt1). Although there were no changes in the actin cytoskeleton organization, we could determine by a wound healing assay that LM3-GPC3-CA Akt1 cells were less migrant than their controls (Wound coverage: LM3-GPC3 control=50% vs. LM3-GPC3-CA Akt1=30%, p&lt;0.05). To address an in vivo effect, different clones were injected s.c. into syngeneic female BALB/c mice. We found that these tumors did not differ in their growth rate, reaching a similar size at 30 days post inoculation (LM3-vector= 189±25, LM3-GPC3= 181±40, LM3-GPC3-CA Akt1= 200±51 mm3). No differences were found in either tumor incidence or in tumor latency. In order to study the experimental metastatic ability, all cell lines were i.v. inoculated. We observed that LM3-GPC3-CA Akt1 tumors developed fewer lung metastases than controls (Median [Range]: LM3-GPC3 control=9 [3-29] vs. LM3-GPC3 CA Akt1=0.5 [0-10], p&lt;0.05). Moreover, the LM3-GPC3-CA Akt1 metastatic nodes were also of a smaller size (&lt;0.5 mm). In sum, our results suggest that Akt1 expression and signaling could be mediating GPC3 inhibitory effect on the metastatic dissemination. The over-activation of this oncogene would exacerbate or heighten GPC3 effects, preventing the metastasis progression through the reduction of cell migration.
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 2231. doi:1538-7445.AM2012-2231
Abstract 2239: The effect combining the KIT inhibitor Imatinib with the PI3K inhibitor BKM120 or the dual PI3K/mTOR inhibitor BEZ235 on the proliferation of gastrointestinal stromal tumor cell lines
Authors: Li Fang , Growney Joseph , Battalagine Linda , Qiu Shumei , Manley Paul , Monahan John 
Published: August 2012

Abstract
Gastrointestinal stromal tumors (GIST) are the most common type of sarcoma found in the gastrointestinal tract, with 5,000-6,000 cases per year diagnosed in the United States. Activating mutations in KIT, or occasionally in PDGFR are present in up to 90% of GISTs. The PI3K/AKT pathway has been demonstrated to be a crucial survival pathway in imatinib-resistant GISTs. In this study, we evaluated single agent activities of the KIT inhibitor imatinib, the PI3K inhibitor BKM120 and the dual PI3K/mTOR inhibitor BEZ235, as well as the synergistic activity of the combination of imatinib with BKM120 and imatinib with BEZ235 in a panel of GIST cell lines. For example, when the antiproliferative effects of imatinib and BKM120 were evaluated in combination at concentrations from 0.37 µM to 3.3 µM, growth suppression was observed in excess of the percent inhibition achieved by imatinib or BKM120 single agent treatment in the GIST882 and GIST430 cell lines. Our results suggest that combining imatinib with BKM120 or BEZ235 may provide a therapeutic strategy for imatinib-resistant GISTs.
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 2239. doi:1538-7445.AM2012-2239
Abstract 2245: The role of STAT3α in Pten-dependent hematopoietic malignancy
Authors: Mizutani Tatsuaki , Casanova Emilio , Stoiber Dagmar 
Published: August 2012

Abstract
Dysregulation of the Janus kinase (Jak) - signal transducer and activator of transcription (Stat) signaling pathway is often associated with cancer. Persistent Stat3 activation has been described in many hematological malignancies. Two isoforms due to alternative splicing have been described for Stat3: Stat3α and Stat3α. Both isoforms exhibit overlapping but distinct biochemical properties. Interestingly, Stat3α has been found in the bone marrow of patients with acute myeloid leukemia (AML) and in several AML cell lines. The role of Stat3α in leukemia development remained elusive so far. To test for an impact of Stat3α in leukemia formation, transgenic mice overexpressing Stat3α have been generated. The expression of the transgene depends on Cre-recombinase activity therefore the mice were intercrossed with Mx-Cre transgenic animals, which enables activation of Cre recombinase in the hematopoietic compartment. This was verified by detection of the reporter protein eYFP in bone marrow cells upon treatment with poly I/C. The Stat3αtgMx-Cretg compound mice were further bred with Ptenfl/fl mice, since loss of Pten in hematopoietic stem cells of mice was reported to lead to myeloproliferative disorder (MPD) that later on progresses to an AML or ALL like disease. Upon poly I/C treatment Stat3αtgMx-CretgPtenfl/fl compound mice diseased with significantly enhanced latency when compared to Mx-CretgPtenfl/fl mice. Accordingly, 20 days after poly I/C injection Stat3αtgMx-CretgPtenfl/fl animals displayed also far less Mac1+Gr1+ myeloid cells than Mx-CretgPtenfl/fl mice. Taken together, our findings suggest that Stat3α acts as a tumor suppressor to prevent Pten dependent MPD/leukemia.
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 2245. doi:1538-7445.AM2012-2245