bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract LB-211: beta1 integrin targeting results in radiosensitization by controlling DNA repair mechanisms and chromatin organization
Authors: Dickreuter Ellen , Storch Katja , Eke Iris , Krause Mechthild , Baumann Michael , Cordes Nils
Published: August 2012

Integrin-mediated cell-extracellular matrix (ECM) interactions confer cancer cell resistance to therapy. Our own data and data of others generated in three-dimensional (3D) ECM-based cell cultures and in vivo provided evidence that particularly beta1 integrin targeting potently reduces this resistance involving downstream integrin signaling mediators like focal adhesion kinase, cortactin and JNK1. However, it remains unknown whether beta1 integrin inhibition affects the repair of radiation-induced DNA double strand breaks (DSB) and their distribution in eu- and heterochromatic DNA regions. Here, we show that 3D growth (cell culture, xenograft models) increased the amount of heterochromatin in human head and neck squamous cell (HNSCC) and lung carcinoma cell lines relative to 2D, induced higher radioresistance, reduced the number of chromosomal aberrations and gammaH2AX/53BP1-positive foci, which was accompanied by a shift of the euchromatin-to-heterochromatin DSB distribution from a 2:1 (2D) to a 1:1 (3D). Upon beta1 integrin inhibition using the inhibitory monoclonal antibody AIIB2 or siRNA, cells grown in 3D or as xenografts in nude mice were radiosensitized or showed a significant growth delay, respectively. The disruption of beta1 integrin-mediated cell-ECM interactions induced an increase in heterochromatin levels indicated by HP1alpha and H3K9me3 elevation. In line with these findings was a strong impairment of both ATM and DNA-PK and their associated downstream signaling pathways (e.g. Chk2, Mre11, Nbs1, Rad50) in beta1 integrin inhibited, irradiated cells relative to IgG isotype controls. In contrast to unchanged number of heterochromatic foci identified in stably transfected HP1alpha cells, kinetic DSB measurements revealed an increased number of euchromatic foci upon beta1 integrin blocking, which evidently showed strongly perturbed DSB repair. In conclusion, our data generated in 3D cell culture and tumor xenograft models suggest a regulatory function of beta1 integrin signaling in the repair of radiogenic DSBs and the organization of chromatin. In addition to our understanding of the initial steps deactivated upon beta1 integrin blocking, these findings bridge membrane bound integrin function to nuclear DNA repair processes, thus providing further insights into how integrins confer cancer cell radioresistance and why integrin targeting is potentially useful as adjuvant to conventional radio- and radiochemotherapy.

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 LB-211. doi:1538-7445.AM2012-LB-211
Abstract LB-247: mTORC1 enhances bortezomib-induced death in TSC-null cells by a c-MYC-dependent induction of the unfolded protein response
Authors: Babcock Justin T. , Nguen Hoa B. , He Yujun , Wek Ronald C. , Quilliam Lawrence A.
Published: August 2012

The ability of the proteasome inhibitor bortezomib to induce apoptosis of cancer cells is influenced by a variety of signaling pathways. We have found that control of c-MYC expression by the mammalian target of rapamycin complex-1 (mTORC1) plays a key role in determining drug sensitivity. Bortezomib treatment of Elt3 (rat TSC2-null leiomyoma) cells, that have high mTORC1 activity, activates the unfolded protein response (UPR) and apoptosis. Both effects were prevented by pretreatment of cells with the mTORC1 inhibitor, rapamycin, indicating mTORC1 dependence. Bortezomib also induced c-MYC expression in Elt3 cells in an mTORC1-dependent manner. c-MYC bound to the promoters of the UPR-induced transcription factors ATF4 and CHOP during bortezomib treatment. These data suggest direct involvement of an mTORC1/c-MYC-driven signaling pathway in the activation of the UPR. Consistent with this notion, overexpression of c-MYC in the presence of rapamycin was sufficient to rescue bortezomib induced CHOP and ATF4 expression, as well as apoptosis. These findings demonstrate that the induction ATF4/CHOP expression by mTORC1 via regulation of c-MYC is a major determinant in the ability of bortezomib to induce apoptosis of tumor cells. Since hypoxia and low nutrient levels in poorly vascularized tumors may contribute to down regulation of mTORC1, our data may help explain some of the difficulties in treating solid tumors with bortezomib and caution against the use of rapamycin in combination with proteasome inhibitors in cancer treatment.

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 LB-247. doi:1538-7445.AM2012-LB-247
Abstract LB-256: Targeting MLL1 methyltransferase activity for treatment of acute leukemia with MLL1 rearrangement
Authors: Townsend Elizabeth C. , Cao Fang , Karatas Hacer , Wang Shao-Meng , Dou Yali
Published: August 2012

Translocation of the MLL1 gene, which encodes for the histone methyltransferase, MLL1, is found in approximately 10% of all cases of acute leukemia and is generally associated with poor patient outcomes. Recent research has pointed to an essential function for the wild-type copy of MLL1 in these leukemias. In these cells, abnormal upregulation of MLL1-directed histone methylation and subsequent overexpression of MLL1 gene targets is an essential step in the development and progression of leukemia. Efficient MLL1-catalyzed histone methylation can only be achieved when MLL1 associates with the complex of WDR5, RbBP5 and Ash2L. MLL1 complex assembly is nucleated by a highly conserved interaction between the MLL1 SET domain and WDR5. We hypothesize that blocking histone methyltransferase activity of wild-type MLL1 through inhibition of the essential WDR5-MLL1 interaction will prevent abnormal gene upregulation and transformation in leukemias with MLL1 rearrangement. Using rational design, we have developed potent inhibitors for WDR5. We have demonstrated that the lead compound, MM-401, can disrupt the interaction of MLL1 with WDR5, and prevent assembly of the MLL1 complex. We have also shown that MM-401 specifically inhibits MLL1 complex activity, with an IC50=320nM. Using MLL1 fusion-transduced mouse bone marrow cells as a model, we have shown that treating leukemia cells with MM-401 inhibits expression of the MLL1 target oncogene, HoxA9, in a concentration-dependent fashion. Treatment of these cells with MM-401 also promotes differentiation of leukemia blasts in a dose dependent manner. Furthermore, MM-401 specifically impairs cell growth and viability of human leukemia cell lines with MLL1 rearrangement but does not alter growth of leukemia cell lines with mutations or translocations targeting other oncogenes. In conclusion, we have developed a potent inhibitor MM-401, which is the first in a novel class of inhibitors designed to target MLL1 methyltransferase activity, one of the most important chromatin modifying enzymes for transcription activation. We have further demonstrated that pharmacological inhibition of the MLL1 methyltransferase activity specifically targets leukemias with MLL1 rearrangement, and shifts leukemia cells away from the undifferentiated, rapidly proliferating state that is characteristic of aggressive AMLs. These results point to a promising new therapeutic target for leukemia treatment.

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 LB-256. doi:1538-7445.AM2012-LB-256
Abstract LB-26: The N-terminal projection domain of the microtubule associated protein Tau inhibits TNFα signaling
Authors: Debnath Shawon , Hannon Peter , Toropova Kristina , Nunez-Rodriguez Nelson , Alonso Alejandra , Fata Jimmie E.
Published: August 2012

Tumor Necrosis Factor-alpha (TNFα) is a multifunctional pro-inflammatory cytokine implicated in inducing both tumor promotion and tumor inhibition. This paradoxical effect can be partly explained by the fact that TNFα acts as a regulator of both proliferation and apoptosis; however the mechanisms and factors associated with how or whether a tumor cell responds to a microenvironment rich in TNFα have not been fully resolved. Here we provide evidence that the microtubule associate protein Tau inhibits TNFα signaling through its N-terminal domain and implicate it as a novel regulator of the cellular response to this key cytokine. Our findings indicate that over-expression of Tau in the human breast cancer cell lines MCF7, SkBr3 and in the pheochromocytoma cell line PC12 suppresses TNFα-induced apoptosis evident in the control cells. TNFα-induced cell apoptosis in control cells is triggered as early as 6 hrs post-treatment with hallmark features of cell shrinkage, membrane blebbing, disruption of tubulin architecture and caspase-3 activation. While over-expression of wild type full length Tau isoform in these cell lines, completely abrogates all TNFα-associated apoptotic phenotypes. Aside from inhibiting TNFα-induced apoptosis, Tau over-expression also interferes with TNFα-induced NFKB activation. This is evident by a significant decrease in NFKB nuclear translocation in Tau over-expressed cells compared to controls. Suppression of TNFα-signaling by Tau is not associated with its tubulin interaction since a truncated N-terminal projection domain lacking all microtubule binding domains still provides resistance to TNFα-induced apoptosis and NFKB activation. These findings lead us to conclude that the functional domain of Tau that regulates TNFα response lies within its N-terminal region and current studies investigating regions within this domain are ongoing. Our data provide direct evidence that the N-terminal domain of the microtubule associated protein Tau can inhibit TNFα signaling in tumor cells. These findings indicate a novel function for Tau and add to our knowledge of how a tumor cell responds to TNFα-signaling.

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 LB-26. doi:1538-7445.AM2012-LB-26
Abstract LB-268: Loss of HPV16 E2 protein expression and transcriptional modulation of cellular and viral genes correlate with progression to cervical carcinoma
Authors: Thierry Francoise
Published: August 2012

Integration of the viral DNA in the cellular genome has been suggested to be critical in carcinogenic progression of HPV-associated cervical neoplasia. This event can be accompanied by disruption of the open reading frame (ORF) encoding the E2 repressor, thus leading to transcriptional up-regulation of the E6 and E7 viral oncogenes. At this stage, it is unclear whether disruption of the E2 ORF is mandatory for carcinogenic progression. We measured E2 RNA and protein expression in clinical samples of various grades of HPV16-associated cervical neoplasia and compared it with the status of the viral genome. RNA extracted from paraffin embedded tissues was hybridized to specific probes and quantified by the NanoString technology. Protein expression was appreciated by immunohistochemistry and the status of viral DNA was determined by in situ hybridization, all performed on serial sections of the same samples. E2 protein was found highly expressed in CIN2 lesions where the HPV DNA was highly replicating, while it was decreased in more advanced grade lesions where replication is decreased or lost (CIN3 and SCC). Our data demonstrate that integration of the viral DNA in the cellular genome is always accompanied by drastic reduction of expression of the E2 protein, even when the E2 ORF is not disrupted by integration. The viral genes appear differentially expressed during progression as transcription of the HPV16 E6/E7 oncogenes, only when compared to E2-E4, is significantly higher in high grade lesions than in CIN2. In addition, transcription of 400 cellular genes of the cell cycle and immune-response were also studied in 20 clinical samples that show modulation during progression. We will discuss the establishment of a transcriptional signature for progression in cervical cancer and the role of local immune response in the fate of cervical lesions associated with HPV16.

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 LB-268. doi:1538-7445.AM2012-LB-268
Abstract LB-281: Hodgkin Lymphoma requires stabilized NIK and constitutive RelB expression for survival
Authors: Ranuncolo Stella M. , Xiao Wenming , Wright George , Abu-Asab Mones , Pittaluga Stefania , Jaffe Elaine S. , Lewis Brian
Published: August 2012

The REL family of transcription factors plays major roles in diverse cell processes and tumor etiology. Despite considerable evidence supporting the role of the REL members in the immune system and lymphomagenesis, it is not clear whether each REL controls unique targets in distinct subsets of B cell-derived lymphomas or whether each is redundant. We delivered specific shRNAs to knock down each REL member in representative non-Hodgkin (NHL) and Hodgkin lymphoma (HL) cell lines. All NHL and HL cell lines were dependent on RelA and c-Rel for survival but only HL cells were sensitive to RelB depletion. ChIP-seq analysis uncovered an extensive nonoverlapping REL networks and that RelB directly controlled cell cycle regulators and apoptosis inhibitors including BCL2 and BCLx. However, the RelB shRNA in HL cells does not kill these cells by apoptosis. Electron microscopy revealed intact nuclei with considerable numbers of cytosolic vacuoles, indicative of autophagy. Secondly, ATG7, a key player in the autophagosomes development, is induced. We found that HL cell lines and primary tumors stably expressed NIK and that HL cell lines are missing either TRAF2 or TRAF3 protein (negative regulators of NIK). Unexpectedly, RelB shRNA resulted in the re-expression of TRAF2 and degradation of NIK protein. Lastly, both NIK shRNA and a small molecule inhibitor of NIK had the same phenotype as the relB shRNA. These data shed light on unexplored aspects of HL biology. We found that HL is the only GC B-cell derived malignancy that relies on RelB for viability, and thus differentiates Hodgkin lymphoma from non-Hodgkin lymphomas. These data argue that each REL member has specific and unique functions and gene targets, as we predicted from the lack of similarities in their transactivation domains. Furthermore, the RelB dependency in HL suggests that NIK is an attractive therapeutic target and the possibility of targeting NIK enzymatic activity in HL patients with diminishing side effects.

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 LB-281. doi:1538-7445.AM2012-LB-281
Abstract LB-283: Aurora B binds p53 during both interphase and mitosis, phosphorylates it and promotes its degradation
Authors: Fuentes-Mattei Enrique , Gully Christopher , Velazquez-Torres Guermarie , Shin Ji-Hyun , Chen Jiun-Sheng , Choi Hyun Ho , Chou Ping-Chieh , Adams Henry P. , Phan Liem , Yang Tsung-Ying , Yeung Sai-Ching J. , Lee Mong-Hong
Published: August 2012

Aurora B (AurB) is a mitotic checkpoint kinase that plays a pivotal role in the cell cycle, ensuring correct chromosome segregation and normal progression through mitosis. Tumor suppressor p53 is a genome guardian and an important negative regulator of the cell cycle. Although overexpression of AurB and loss or degradation of p53 have been described in many types of human cancers, it is not known whether AurB and p53 are coordinately regulated during the cell cycle. Recently has been shown that NIR, which is a transcriptional co-repressor of histone acetyltransferase activity, interact with and suppress p53 via interaction with AurB. Our results show that AurB directly interacts with p53 in a NIR-independent matter. To prove direct molecular interaction between AurB and p53 in whole cells, we employed the method of bimolecular fluorescent complementation (BiFC). AurB-p53 interaction occurs at the nucleus in interphase and at the centromeres in prometaphase of mitosis. We observed that AurB-p53 interaction co-localized with Survivin and CENP-A, suggesting that AurB and p53 interact at the centromeres. Our results also show that Aurora B phosphorylates p53 to accelerate p53's degradation through the polyubiquitination-proteasome pathway, thus functionally suppressing the expression of p53 target genes involved in cell cycle inhibition and apoptosis. Inhibition of Aurora B in cancer cells with wild-type p53 increased p53 protein level and expression of p53 target genes to inhibit tumor growth. Together, these results give a new insight of a novel mechanism of p53 inactivation during the cell cycle and imply that oncogenic hyperactivation or overexpression of AurB may compromise p53's tumor suppressor function.

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 LB-283. doi:1538-7445.AM2012-LB-283
Abstract LB-294: Transforming growth factor beta 3 (TGF-ß3) contributes to epithelial-mesenchymal transitions (EMT) in human prostate cancer
Authors: Zhang Qiang , Lin Xiao , Helfand Brian , Chen Lin , Kozlowski James , Yang Ximing J , Zhu Lihua J , Lee Chung
Published: August 2012

Introduction and Objective: TGF-ß3 is considered as an important endogenous mediator of normal developmental and cellular repair, but its role in cancer is not well characterized. We recently reported that over-production of TGF-ß1 by tumor cells is involved in the epithelial-mesenchymal transition (EMT) in cancer cells. Based upon our prior findings, we hypothesized that, in addition to TGF-ß1, TGF-ß3 may also be involved in the EMT and contribute to prostate cancer (PCa) progression. In the present study, we explored the relationship between TGF-ß3 and TGF-ß1 induced EMT pathway in PCa. Methods: We studied 287 prostatectomy specimens obtained from the Northwestern University Prostate SPORE tissue bank. 165 specimens had low Gleason score (≤6, LGS), 55 had intermediate Gleason score (7, IGS), and 67 had high Gleason score (8-10, HGS). The median follow-up was 60 months (range 22-82). Levels of TGF-ß 1, TGF-ß 3, NF-kB and vimentin were analyzed using a high-throughput tissue microarray analysis and immunohistochemistry staining. Clinical correlation was performed based on patient follow-up information from the Prostate SPORE clinical-linked database which includes pre- and post-operative serum PSA levels. Results: High levels of TGF-ß3 expression were identified in 33.8%, 2.8% and 1.1% of HGS, IGS and LGS tumors, respectively, while high levels of vimentin expression occurred in 23.9%, 3.6% and 1.8% of HGS, IGS and LGS tumors, respectively. Expression of vimentin was significantly associated with high levels of TGF- ß3 (P=3.22E-06). Furthermore, TGF- ß3 overexpression was significantly associated with more aggressive tumors with high Gleason score (P=9.76E-09). Furthermore, there was a positive and significant correlation between expression of TGF- ß 3 and TGF-ß1 (P=2.29E-07), and between the expression levels of TGF- ß3 and NF-kB (P=7.52E-12), which were previously reported to be important mediators of the EMT in PCa. Conclusion: Our results firstly demonstrate that TGF-ß3 has a close correlation with TGF-ß 1 mediated overexpression of vimentin in PCa, which highly suggests that TGF-ß3 may play a critical role in the TGF- ß1 induced NF-kB mediated EMT signaling pathway. This pathway was reported to play a dramatic effect on the progression of human PCa and disease recurrence after prostatectomy. Consideration of TGF- ß3 tissue immunohistochemistry should be considered as a novel potential biomarker for EMT of PCa in clinic.

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 LB-294. doi:1538-7445.AM2012-LB-294
Abstract LB-297: The EMT inhibitor AB-16B5 interacts with specific isoforms of secreted clusterin
Authors: Tremblay Gilles B. , Viau Elisabeth , Filion Mario
Published: August 2012

Secreted clusterin (sCLU) exhibits elevated expression in several cancer indications. sCLU plays a pro-survival role in tumors and, more recently, it was found to be a potent stimulator of the epithelial-to-mesenchymal transition (EMT). These findings led to the development of a monoclonal antibody, AB-16B5, that interacts with a specific EMT-inducing domain in sCLU resulting in abrogation of migration and invasion of many types of cancer cells. We previously showed that blocking tumor-associated sCLU with AB-16B5 reduced the expression of mesenchymal markers and restored the expression of epithelial markers in human tumor xenografts, observations that were in line with inhibition of EMT in vivo. Consequently, this resulted in reduced metastatic invasion and increased response to cytotoxic agents in animal models of human cancer. We now report new results that shed light on the biochemical differences between sCLU that is secreted by tumor cells or normal cells. Using two-dimensional gel electrophoresis, we found that there was a difference in the number and composition of sCLU isoforms present in the plasma of cancer patients compared with those expressed in healthy individuals. In particular, the post-translational modifications were more complex on sCLU secreted from tumor cells compared with those present in sCLU from healthy individuals. Moreover, AB-16B5 was found to specifically interact with several of the isoforms expressed from tumor cells but exhibited a reduced ability to interact with sCLU from plasma from healthy individuals. We also examined the interaction between AB-16B5 and tumor-associated sCLU in vivo. In these studies, injection of AB-16B5 conjugated to a fluorophore in mice harboring sub-cutaneously implanted human pancreatic tumor xenografts resulted in a rapid enrichment of fluorescence signal in the tumors. Interestingly, administration of high concentrations of human recombinant sCLU immediately prior to injection of the AB-16B5 fluorophore-conjugate still resulted in enrichment of fluorescence signal in the tumors, albeit at slightly lower intensity than was observed in the absence of recombinant sCLU. Our findings indicate that AB-16B5 can efficiently interact with tumor-associated sCLU despite the presence of excess concentrations of sCLU in the circulation. Taken together, our results suggest that AB-16B5 has increased affinity for sCLU isoforms that are specifically expressed from tumor cells that have undergone an EMT.

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 LB-297. doi:1538-7445.AM2012-LB-297
Abstract LB-426: Potent inhibitors of RAS pathways that bind directly to Ras proteins
Authors: Johannessen Liv , Remsberg Jarrett R. , Ivanova Alla , Gaponenko Vadim , Khavrutskii Lyuba , Tarasov Sergey G. , Dean Michael , Kates Joseph , Tarasova Nadya I.
Published: August 2012

RAS genes are the most frequently mutated oncogenes in human cancer. Although they are believed to be among the most important drug targets in oncology, no synthetic molecules that directly target any member of the family and inhibit its function with appreciable in vivo or even in vitro activity have been identified. We have utilized a previously developed approach of peptide structural stabilization by membrane anchoring for the development of potent inhibitors of Ras proteins. We have tested lipopeptide analogs of different parts of Ras proteins and their interaction partners and have found lipopeptide analogs of hypervariable regions and of the C-terminal alpha helix (helix 6) of Ras proteins to be the most effective in interfering with Ras function and inhibiting Ras-dependent, but not Ras-independent growth of cancer cells. Direct binding of inhibitors to recombinant K-Ras (1-166) was detected by Microscale Thermophoresis (MST), and circular dichroism spectroscopy. NMR titration data revealed a localized interaction of helix 6 analogs with the Switch I region of K-Ras with the most significant chemical shift perturbations found in residues Q25, N26, S32, T35, and E37. Compounds inhibit the formation of active RasGTP and prevent Ras signaling to downstream effectors. Structural optimization of helix 6 analogs resulted in a metabolically stable, 12 amino acid residues long peptide made of all-D amino acids that inhibited the growth Ras-dependent cancer cell lines with GI50 below 1 nM. MST studies have shown that a fluorescently-labeled version of the compound binds to recombinant GDP-loaded K-Ras (1-166) with KD= 86 ±8 nM. Derivatives of K-Ras4B hypervariable region exert their activity by a significantly different mechanism: they cause degradation of Ras protein. Partially optimized compound of the series inhibit growth of cancer cells with GI 50 in submicromolar range and bind to recombinant K-Ras (1-166) with KD=1250±140nM (as determined in MST assay). CD spectroscopy data suggest that binding of compounds of both classes to K-Ras is accompanied by significant changes in protein secondary structure. In mice, inhibitors potently inhibited growth of H358 human lung tumor xenograft and Lewis lung carcinoma when injected subcutaneously every second day. The compounds are promising drug candidates for the treatment of many tumor types.

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 LB-426. doi:1538-7445.AM2012-LB-426
Abstract LB-450: Necrosis predicts benefit from hypoxia-modifying therapy in urothelial cell carcinoma of the bladder
Authors: Irlam-Jones Joely J. , Williamson Amanda , Taylor Janet , Denley Helen , Agrawal Shailesh , Choudhury Ananya , Ryder David , Rojas Ana M. , Hoskins Peter J. , Miller Crispin J. , Ord Jonathan J. , Harris Adrian L. , West Catharine M.L.
Published: August 2012

To investigate the ability of tumor necrosis to predict benefit following radiotherapy with and without hypoxia-modifying treatment in high grade urothelial cell carcinoma of the urinary bladder. Background: There is no predictive marker of hypoxia-modifying therapy in cancer patients in routine clinical use. Methods: We identified 231 patients who participated in the BCON phase III randomised trial comparing radical radiotherapy (RT) with and without carbogen and nicotinamide (CON) in patients with urothelial cell carcinoma of the bladder who were suitable for this retrospective study. Tumor necrosis was scored on whole tissue sections as absent or present. Results: Tumor necrosis was identified in 121 of the 231 patients (52%). 5-year overall survival estimates were 41% for the RT arm and 48% for the CON arm (log rank p=0.14). When stratified using tumor necrosis, the 5-year overall survival estimates were 48% (RT) and 39% (CON) (log rank p =0.32) in patients with no evident tumor necrosis, and 34% (RT) and 56% (CON) (log rank p=0.004) in patients with tumor necrosis. Multivariate analyses showed that the presence of tumor necrosis was a significant predictor of benefit from CON with the risk of dying 57% lower compared to RT alone (HR 0.43, 95% CI 0.25-0.73, p=0.002). This trend was not observed when there is no evident tumour necrosis (HR 1.64, 95% CI 0.95-2.85, p=0.08). Test for heterogeneity in treatment effect by necrosis strata (p=0.007 unadjusted, p=0.001 adjusted). Conclusions: Tumor necrosis significantly predicts benefit from radiotherapy with hypoxia-modifying treatment. Independent validation in a prospective trial is warranted.

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 LB-450. doi:1538-7445.AM2012-LB-450
Abstract LB-465: The miRNA cluster 424/503 is an integral part of the TGFb-mediated cytostatic response in human mammary epithelial cells
Authors: Navas David Llobet
Published: August 2012

TGF-beta plays a major role during development and normal tissue homeostasis. Indeed and focusing in mammary tissue biology TGF-beta has been unmasked as a key component during epithelium cell proliferation, lactancy and involution. However, and despite most of the TGF-beta actions are well known for decades, its dichotomic effects depending on cell type, context and disease states and the mechanisms that lie underneath are still not fully understood. In this study we uncover a novel player in the mechanism through which TGF-beta induces cell cycle arrest in mammary epithelial cells. Using microRNA array expression profile we found a strong correlation between the expression of miRs 424 and 503 and TGF-beta treatment in MCF10A cells. Interestingly, this microRNAs are located clustered in the long arm of the X chromosome, regulated by a region located upstream containing a canonical SMAD3/4 binding site and expressed as a policistronic pri-miRNA. Ectopic upregulation of miR-424/503 induces cell cycle arrest at G1 phase mimicking TGF-beta actions. Our mechanistic studies have unveiled that this miRNA cluster exerts its function by modulating the expression of CDC25A through binding to its 3′UTR. Altogether our results point to miRs 424/503 as a new player in the cytostatic program mediated by TGF-beta in mammary epithelial cells.

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 LB-465. doi:1538-7445.AM2012-LB-465
Abstract LB-470: Tumor suppressor role of microRNA-18b in melanoma
Authors: Dar Altaf A. , Majid Shahana , de Semir David , Bezrookove Vladimir , Nosrati Mehdi , Kashani-Sabet Mohammed
Published: August 2012

MicroRNAs play important roles in gene regulation, and their expression is frequently dysregulated in various tumors. Here, we report that expression of miR-18b is significantly suppressed in melanoma specimens when compared with nevi. miR-18b is silenced in melanoma cell lines due to hypermethylation and is re-expressed by 5-AZA-deoxycytidine (5-AZA) in melanoma cell lines. miR-18b overexpression suppressed cell survival, colony formation, invasiveness and migratory ability and induced apoptosis in melanoma cell lines. Stable overexpression of miR-18b suppressed melanoma cell proliferation, colony formation, and tumor cell growth in-vivo. miR-18b reverses epithelial-to-mesenchymal transition in melanoma cell lines and its expression was induced by the chemotherapeutic drug cisplatin. These results demonstrate a novel role for miR-18b as a tumor suppressor in melanoma.

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 LB-470. doi:1538-7445.AM2012-LB-470
Abstract LB-475: 3′UTR polymorphisms affect expression and activity of IGF1R, a therapeutic target in pediatric neuroblastoma
Authors: Sotillo-Piñeiro Elena , Xu Liu , Nguyen Le , Laver Travis , Attiyeh Edward , Cole Kristina , Diskin Sharon , Maris John , Thomas-Tikhonenko Andrei
Published: August 2012

For patients with high-risk neuroblastoma (NB) survival remains below 40%, and survivors suffer from life-long treatment-related disabilities. This necessitates the development of oncogene-specific targeted therapies. We and others observed that small-molecule inhibitors of IGF1R exhibit anti-proliferative effects against NB cells in vitro and in vivo. Yet given the apparent lack of somatic mutations in the IGF1R gene, it remains to be determined what subset of NB patients would benefit from this approach. We hypothesized that IGF1R expression could be affected by alterations in the 3′UTR that prevent binding by microRNAs. Indeed, as evidenced by cancer gene sequencing data on 188 primary high-risk NBs, IGF1R was the gene by far most frequently affected by 3′UTR alterations. We initially focused on the genetic variant rs3833015, a small 2-nt deletion found in ∼50% of NB patients and overlapping with the putative miR-140 binding site. The positive effects of this 3′UTR variant on IGF1R expression were established using luciferase sensor assays, immunoblotting on commonly available NB cell lines, and transcriptome profiling of 28 primary neuroblastomas using Gene Set Enrichment Analysis. Additional 3′UTR variants that affect IGF1R expression and map in the proximity of miR-binding sites were identified using Expression Quantitative Trait Loci (eQTL) analysis. Our experimental data lead us to postulate that rs3833015 and other IGF1R 3′UTR variants help sustain IGF1 signaling, resulting in the “addiction” to this survival pathway and increased sensitivity to small-molecule IGF1R inhibitors.

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 LB-475. doi:1538-7445.AM2012-LB-475
Abstract LB-478: MiRNA as biomarkers to predict de novo chemoresistance to neoadjuvant chemotherapy in patients with muscle invasive bladder cancer
Authors: Vinall Ruth L. , Tepper Clifford , Z.Ripoll Alexandra , Gandour-Edwards Regina , Durbin-Johnson Blythe , White Ralph deVere
Published: August 2012

The primary goal of this study was to determine whether miRNA expression profiling can predict de novo chemoresistance to treatment with neoadjuvant chemotherapy in patients with muscle invasive bladder cancer (MI-BC). The relative expression of 9 miRNAs in 41 annotated, diagnostic MI-BC patient samples was determined by quantitative real-time PCR (qPCR) and correlated with patient response to neoadjuvant chemotherapy, p53 status (SSCP/sequencing) and pRb, p21 expression (IHC). These 9 miRNA were chosen based on a known link to either transitional cell carcinoma (TCC) progression and/or chemoresistance. Expression of these miRNA was also assessed in 8 paired pre- versus post-chemotherapy patient samples from non-responders. Patients with higher let-7c expression levels had significantly higher odds of responding to neoadjuvant chemotherapy (p = 0.023, OR 2.493, 95% CI 1.121, 5.546). The odds of response was not significantly different between patients with vs. without p53 mutations (p = 0.948, OR 0.955, 95% CI 0.231, 3.945). Post-chemotherapy samples expressed significantly higher levels of let-7c (geometric mean ratio = 3.5, P = 0.006). Lower let-7c expression levels appear to predict chemoresistance in TCC patients, prospective studies will be needed to validate this finding. Pre- versus post-chemotherapy patient sample analyses indicate increased let-7c expression plays a role in mediating disease progression following treatment with chemotherapy. Future studies will focus on determining the functional role played by let-7c in chemoresistance and disease progression.

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 LB-478. doi:1538-7445.AM2012-LB-478
Abstract LB-481: MicroRNAs as novel therapeutic targets to treat drug-resistant breast cancers
Authors: Chang Yao-Fu , Zoghi Behyar , Panneerdoss Subbarayalu , Pertsemlidis Alexander , Rao Manjeet K.
Published: August 2012

Acquired drug resistance continues to be a major clinical impediment to the successful treatment of cancer. For example, resistance to agents such as paclitaxel and trastuzumab accounts for treatment failure in more than 90% of patients with metastatic breast cancers. Understanding the mechanisms underlying such resistance is therefore crucial for the development of new, efficacious drugs against cancer. Unfortunately in spite of extensive inquiry in this field, little is known about the key molecules and signaling pathways that regulate this phenomenon. Recently, we have discovered that microRNAs (miRNAs) may play critical roles in mediating drug sensitivity/resistance in breast cancers. We have identified miRNAs that are differentially expressed between chemo-resistant and sensitive HER2+ breast cancer cells. Specifically, through high-throughput miRNA inhibitor library screens, we have identified miRNAs that sensitize drug-resistant breast cancer cells to paclitaxel and trastuzumab, a drug combination commonly used for the treatment of metastatic HER2+ breast cancers. MiRNA/s that alter/s the cellular response to these drugs may target a common signaling pathway. For example, resistance to paclitaxel/trastuzumab in breast cancer has been proposed to be a consequence of loss of PTEN expression, leading to altered AKT signaling. Our findings suggest that certain miRNAs are selectively cytotoxic in a drug-specific manner and that these miRNAs may provide novel adjuvant therapeutic tools for the treatment of drug-resistant metastatic breast cancers.

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 LB-481. doi:1538-7445.AM2012-LB-481
Abstract LB-488: Induction of autophagy by heat shock factor 1 promotes breast cancer resistance to chemotherapy
Authors: Desai Shruti , Liu Zixing , Fodstad Oystein , Tan Ming
Published: August 2012

Breast cancer is the most common type of cancer as well as one of the leading causes of cancer-related deaths in women. The increasing emergence of drug resistance to commonly used chemotherapeutic agents has warranted the development of novel and robust treatment options for cancer patients. Carboplatin, a DNA damaging agent, is one of the therapeutic agents which has shown promising results in breast cancer clinical trials. Carboplatin is a second generation platinum drug, increasingly used in clinic to treat cancer patients because of its reduced toxicity and side effects when compared to Cisplatin. Heat Shock Factor 1 (HSF1) is the master regulator of heat shock responses which has also been shown to regulate certain non-heat shock reponse genes. As a transcription factor HSF1 can function as both an activator and repressor of its target genes, resulting in regulation of critical cellular processes invovled in managing cellular stress. The focus of this study is to identify the role of HSF1 in Carboplatin mediated-sensitivity in breast cancer cells, to provide novel insights to improve treatment strategies for cancer patients. Carboplatin treatment in multiple breast cancer cell lines induced growth inhibition which was significantly enhanced upon HSF1 knockdown. Interestingly, the treatment also induced autophagy in these cells. Autophagy is a type II programmed cell death, which is induced in response to metabolic stress and has been demonstrated to mediate drug resistance, since it can play a protective role and allow cells to survive under stressful conditions. Knockdown of HSF1 along with inhibition of autophagy by 3-Methyladenine (3-MA) led to increase in apoptosis in these cells. Furthermore, HSF1 was required for the induction of autophagy in Carboplatin treated cells. Knockdown of HSF1 by siRNA (transient) and shRNA (stable), inhibited induction of autophagy in the presence of Carboplatin, as measured by the punctate EGFP-LC3 structures as well as acridine orange staining. Chromatin immunoprecipitation (ChIP) assay along with Real time- PCR analysis revealed that HSF1 can regulate autophagy by directly regulating the expression of autophagy related genes in the presence of Carboplatin. These findings indicate that HSF1 activates autophagy in response to the Carboplatin induced cellular stress thus leading to cell survival and reducing sensitivity to Carboplatin. Our data strongly support a critical role for HSF1 in promoting chemoresistance through induction of autophgy. This finding has important implications in the development of targeted therapeutics for overcoming Carboplatin resistance in 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 LB-488. doi:1538-7445.AM2012-LB-488
Abstract LB-493: Blocking the integrin αvβ3-CRAF axis with Cilengitide arrests glioblastoma cells in pro-metaphase
Authors: Franovic Aleksandra , Cheresh David A.
Published: August 2012

Glioblastoma multiforme (GBM) is the most prevalent brain tumor subtype, with a particularly high mortality rate due to frequent recurrence and poor response to standard therapies. Improving outcome for these patients will require new therapies which target the unique features of this disease. One such approach is geared toward integrin αvβ3, as high-grade GBM tumors express both the extracellular matrix protein vitronectin and its receptor integrin αvβ3 which drive several key cell signaling pathways to promote cell invasion and survival. Blocking the function of integrin αvβ3 with the antagonist Cilengitide shows potent anti-tumor activity in preclinical models and is currently completing the first Phase III trial for newly-diagnosed GBM. Understanding the mechanisms of activity for Cilengitide will be critical as this drug nears FDA-approval for GBM. Since αvβ3 is highly expressed in both the brain tumor vasculature and on glioma cells, it is not clear whether Cilengitide exerts its effects by disrupting tumor angiogenesis, tumor cell invasion and survival, or other hallmark tumor traits. Focusing on GBM cells, we have made the novel observation that αvβ3 ligation leads to phosphorylation of CRAF on serine 338, an event which we have recently linked to cell survival and cell cycle progression. Pharmacological inhibition or knockdown of integrin αvβ3 reduces activated CRAF levels, causes tumor cells to arrest in pro-metaphase, and suppresses the growth of orthotopic GBM in mice. Activating this pathway by expression of a phospho-mimetic CRAF S338D mutant independently drives cell cycle progression in vitro, accelerates tumor growth in vivo, and renders tumors resistant to the effects of Cilengitide. These findings reveal a previously unappreciated mechanism of action for Cilengitide. In addition to its well-known anti-angiogenic function, it also directly induces cell cycle arrest in GBM cells. The clinical implications of this observation are two-fold as it: 1) provides important insight that could aid in the design of combination treatment regimes; and 2) points at integrin αvβ3 and phosphorylated CRAF S338 expression as potential biomarkers which could serve to help identify the patient populations most likely to benefit from Cilengitide.

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 LB-493. doi:1538-7445.AM2012-LB-493
Abstract LB-69: Role of HDAC1 in epigenetic repression of E-cadherin after transient Epstein Barr virus infection
Authors: Queen Krista J. , Scott Rona S.
Published: August 2012

Epstein-Barr virus (EBV) is a gammaherpesvirus associated with a variety of lymphoid and epithelial tumors. Although EBV is a known tumor virus, incomplete association of EBV with any given tumor type has confounded its role in tumorigenesis. For example, only 15% of gastric carcinomas are EBV-positive compared to virtually all undifferentiated nasopharyngeal carcinomas. Upon entry into a cell, the viral genome is chromatinized and EBV rapidly shuts off its viral gene expression program via methylation of its viral promoters in an attempt to evade the host immune response. A similar restricted pattern of viral gene expression is present in EBV-positive tumors. We hypothesize that EBV infection of tumor cells results in virus-induced epigenetic alterations to host genes that remain after loss of the virus and may provide a selective advantage to the tumor cell. To identify virally induced epigenetic alterations, we established a transient model of infection to model the effects of viral redundancy and loss in carcinogenesis. Carcinoma cell lines were infected with recombinant EBV, passaged with selective pressure, and allowed to lose viral genomes by withdrawal of selection. Transient EBV infection of lung carcinoma cells resulted in numerous gene expression changes relative to uninfected controls suggestive of cellular epigenetic reprogramming. Two such gene expression changes, PYCARD and E-cadherin were found to be due to DNA methylation and loss of histone acetylation, respectively. To understand the mechanism behind loss of histone acetylation at the E-cadherin locus following transient EBV infection, we examined the role of histone deacetylases (HDACs) in mediating the epigenetic repression. We observed an increase in total HDAC activity in our transiently infected, EBV-negative clones. Through the use of specific inhibitors, we noted class I HDACs, specifically HDAC1, was involved in the repression of E-cadherin in transiently infected clones. EBV-modulation of HDAC1 activity may lead to host epigenetic alterations that are retained after loss of the virus. Future experiments are aimed at determining the viral and cellular players responsible for the epigenetic alterations that are seen in transiently infected, EBV-negative clones. These results suggest that EBV alters cellular gene expression in a heritable fashion in formerly infected cells, while its own contribution to the oncogenic process is masked.

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 LB-69. doi:1538-7445.AM2012-LB-69