bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract 6: A triple-helix forming oligonucleotide targeting a genomic locus is capable of sequence specific mutagenesis in human lymphoblastoid TK6 cells
Authors: Reshat Reshat , Priestley Catherine , Gooderham Nigel J. 
Published: February 2011

Abstract
It has been reported that DNA triplex formation induces mutagenesis as determined using plasmid-based reporter constructs (Wang et al 1996, Science, 271, p802). Triplex mediated mutagenesis has been shown to include point mutations, deletions, small insertions and homologous recombination. To the best of our knowledge, no study has successfully examined the mutagenic potential of a non-conjugated triplex-forming oligonucleotide (TFO) targeting a genomic sequence. In this study, we have designed a TFO that targets the hemizygous hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus, in the human lymphoblastoid TK6 cell line, and assessed mutagenicity through resistance to 6-thioguanine.
Our TFO, TFO27, has been designed to form a triplex with a purine tract in exon 3 of the HPRT gene. Triplex formation at the target motif was shown to occur at nanomolar concentrations, confirmed by Electrophoretic Mobility Shift Assays. A scrambled oligonucleotide, SCR27, failed to form a triplex at the target motif. A range of transfection reagents were evaluated for facilitated delivery of TFO27, and resulted in variable cellular toxicity. Transfection of high concentrations of oligonucleotide, with acceptable levels of cytotoxicity, resulted in HPRT mutation with TFO27 but not SCR27. Similar experiments failed to result in mutation at the non-targeted thymidine kinase (TK) locus, suggesting locus specificity for the mode of action of TFO27. The target specificity and sequence context of these mutagenic events is being determined to establish the mechanism of mutation.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 6.
Abstract 604: Erucin treatment through induction of thioredoxin reductase may alter tamoxifen resistance in LCC2 cells
Authors: Penney Rosalind B. , Felty Quentin , Slingerland Joyce , Roy Deodutta 
Published: February 2011

Abstract
Tamoxifen-resistant growth is a considerable problem in the treatment of estrogen receptor-positive breast cancer. While the mechanisms of tamoxifen do not rely on an increase in oxidants, reactive oxygen species have been shown to increase with tamoxifen treatment, and tamoxifen-resistance coincides with a high intracellular oxidant state. We postulate that the chronic use of tamoxifen leads to a pro-oxidant environment in cells, leading to tamoxifen resistance. Here we present data that show that increasing a reduced state in the cell through an induction of thioredoxin reductase and subsequent reduction of oxidized thioredoxin, may restore tamoxifen sensitivity to previously resistant LCC2 cells. The isothiocyanate erucin has been found to increase thioredoxin reductase in MCF-7 cells. As such, we tested this in the MCF-7 derivative cell line LCC2, which is sensitive to fulvestrant but resistant to tamoxifen. We found that erucin not only increases expression of thioredoxin reductase, but also increased expression of thioredoxin in LCC2 cells. Erucin treatment led to a decrease in DNA synthesis, as measured by BrdU incorporation. In vitro tumor formation, as measured by colony count with soft agar colony formation assay, was also decreased in tamoxifen-treated cells after erucin treatment. Western blotting shows an increase in p27 with erucin treatment, and probing for p27 in a Jab1 immunoprecipitation shows a decrease in p27/Jab1 interactions after erucin treatment, similar to the effects of fulvestrant in these cells. These data support our hypothesis that altering thioredoxin's redox status can affect the sensitivity of tamoxifen to previously resistant cells, and this alteration may be through the p27/Jab1/thioredoxin pathway.
Supported by BCRP-funded project W81XWH-07-1-0417, BC060125.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 604.
Abstract 606: Heat shock protein 90 inhibitors: New mode of therapy to overcome aromatase inhibitor resistance
Authors: Wong Cynthie , Chen Shiuan 
Published: February 2011

Abstract
Results from several major trials have revealed that aromatase inhibitors (AIs) are superior to tamoxifen with regard to disease progression, incidences of locoregional and distant relapses, and contralateral breast cancers. Although AIs are highly effective drugs (with outstanding specificity and potency), unfortunately, a significant number of AI-treated breast cancer patients will eventually develop disease progression due to acquired resistance. Hormone refractory breast cancers result from complex molecular changes and are challenging to cure. Recently, we examined whether the heat shock protein 90 (HSP90) inhibitor 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG) can inhibit the growth of AI-resistant breast cancers and the mechanisms by which 17-DMAG affects proliferation. AI-responsive MCF-7aro and AI-resistant LTEDaro breast epithelial cells were used in this study. We observed that 17-DMAG inhibited proliferation in both MCF-7aro and LTEDaro cells in a dose-dependent manner. 17-DMAG induced apoptosis and G2 cell cycle arrest in both cell lines. Although inhibition of HSP90 decreased the levels of ERα, the ERα transcriptional activity was not affected when cells were treated with 17-DMAG together with estradiol. Moreover, detailed mechanistic studies suggested that 17-DMAG inhibits cell growth via degradation of HSP90 client proteins AKT and HER2. Furthermore, our experiments using AI responsive MCF-7aro cells have revealed that HSP90 inhibitors such as 17-DMAG and AIs such as letrozole can suppress the proliferation of hormone-dependent breast cancer cells in a synergistic manner.
To study de novo AI-resistance, our lab has generated MCF-7 cell models to overexpress both aromatase and either Akt (MCF-7Aktaro) or HER2 (MCF-7aroHER2). We have found that HSP90 inhibitor 17-DMAG is also effective on suppressing the proliferation of these de novo AI resistant cells. Collectively, results from this study provide data to support the theory that HSP90 inhibitors may be an effective therapy to delay and treat AI-resistant breast cancers (This research was supported by the NIH grant CA44735).
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 606.
Abstract 607: Loss of pigment epithelium derived-factor (PEDF) is associated with breast cancer progression and antihormone drug resistance
Authors: Wambi Joan S. , Kim Helen , Jordan V. Craig 
Published: February 2011

Abstract
Despite the benefits of antihormones in treating estrogen receptor (ER)-positive breast cancer, many tumors develop resistance. Pigment epithelium-derived factor (PEDF) is an endogenous antiangiogenic protein that is showing promise as a potential anticancer agent. PEDF is considered a potential tumor suppressor because its expression is very high in normal tissues but is loss or reduced in various types of malignancies. Previously, it was reported that PEDF expression was signficantly reduced in human breast cancer and that a lack of PEDF expression was a potent factor for the enhancement of tumor growth and angiogenesis. At present however, there are no studies which have examined whether PEDF plays a role in antihormone resistance. In this study, we have characterized the role of PEDF in breast cancer progression and assessed whether PEDF, through a possible interaction with the ER, plays a role in antihormone drug resistance. We found that PEDF expression was dramatically reduced in antihormone-resistant breast cancer cells compared to antihormone-sensitive cells and that reexpression of PEDF in these cells resensitized them to antiestrogens. In addition, we found that treatment of antihormone resistant breast cancer cells with recombinant PEDF significantly reduced the growth of these cells by inducing apoptosis and it reduced the ability of these cells to migrate and invade through an artificial basement membrane. Interestingly, we also found that PEDF expression was dramatically reduced in ER-negative versus ER-positive breast cancer cells; however, there was no significant correlation between PEDF expression and ER in our antihormone resistant cells which continued to expressed high levels of ER despite their PEDF-negative status. Overall, these observations support the hypothesis that a loss of PEDF expression plays an important role in antihormone resistance in breast cancer and they suggest that the presence of PEDF might be an important indicator of antihormonal responsiveness.
This work was supported by the NIH Career Development Grant K01CA120051-01A2, the American Cancer Society Grant IRG-92-027-14; and the Hollenbach Family Fund.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 607.
Abstract 608: HOXB7 as a key regulator in the development of tamoxifen resistance
Authors: Jin Kideok , Zhu Tao , Shah Tariq , Bhujwalla Zaver M. , Sukumar Saraswati 
Published: February 2011

Abstract
Multiple factors including long term treatment with tamoxifen are involved in the development of selective estrogen receptor modulator resistance of ERα positive breast cancer. It is well known in the endocrinology field that increased levels of ErbB/HER family members can also directly alter the cellular response to tamoxifen, but the mechanisms underlying increased expression of ErbB/HERs are not clear. In this report we show that HOXB7 is an ERα responsive gene and the downregulation of HOXB7 expression by estradiol is abrogated by tamoxifen in MCF7 cells. HOXB7 overexpression renders MCF-7 cells resistant to tamoxifen via cross-talk between receptor tyrosine kinases and ERα signaling. EGFR and HER2 expression is upregulated by overexpression of HOXB7, while knockdown of HOXB7 with siRNA in tamoxifen-resistant cell lines causes decrease of EGFR and HER2 expression and loss of tamoxifen resistance. In addition, our work demonstrates that to mediate upregulation of EGFR and HER2, HOXB7 binds to ER-alpha and promotes HER2 transcription activity through direct binding to the HER2 enhancer region by competing with other cofactors. Also, HOXB7 enhances EGFR transcription activity via binding to EGFR promoter region. However, depletion of HOXB7 affects the binding affinity of HOXB7 and the cofactors to the HER2 enhancer element. Higher expression levels of HOXB7 significantly correlated with poorer disease free survival in ERα positive breast cancer patients on adjuvant tamoxifen monotherapy. These findings implicate overexpression of HOXB7 as a key event in the initiation and maintenance of tamoxifen resistance. These studies suggest that HOXB7 acts as a key regulator orchestrating two major groups of target molecules in the oncogene heirarchy. Functional antagonism of HOXB7 could circumvent tamoxifen resistance.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 608.
Abstract 610: Metformin augments rituximab and chemotherapeutic agents-induced apoptosis via mTOR inhibition in rituximab-resistant B lymphoma cell lines
Authors: Kim Min Kyoung , Yoo Eun Kyung , Kim Nam-Yi , Lee Kyung Hee , Hyun Myung Soo , Kang Min Kyu , Lee ChuHee 
Published: February 2011

Abstract
With elusive mechanisms, a subgroup of NHL patients who treated with rituximab in combination with cytotoxic chemotherapeutic agents becomes unresponsive. Patients who relapsed lymphoma are known to have poorer outcome when treated with rituximab compared with treated without rituximab. Since activation of mTOR pathway has been recently suggested for progression of NHL, especially in salvage setting, we'd like to examine the effect of metformin which inhibits mTOR pathway in rituximab-resistant NHL. Three lymphoma cell lines (Raji, Raji-2R, Raji-4RH) were used, which were kindly given by Dr Czuczman MS from Rosewell Park Cancer Institute (Ref. Czuczmana MS et al. Clin Cancer Res 2008;14:1561, 2008;14:1550). These cells were treated with cisplatin, adriamycin, vincristine and rituximab in the absence or presence of metformin for 24, 48, 72 hrs. Cell growth and proliferation was evaluated by MTT assay and cell cycle progression was determined FACS analysis. To characterize molecular mechanisms involved in metformin-induced inhibition of cell proliferation, the level of BAX, BAK, Bcl-2, Bcl-XL, Mcl-1, AMPK, pAMPK, pACC, mTOR, p70S6K and S6K was determined by western blot analysis.
Compared with rituximab-sensitive cell line (RSCL) which is parental lymphoma cell, Raji, rituximab-resistant cell lines (RRCLs), that are Raji-2R and Raji-4RH, have shown decreased cytotoxicity in response to chemotherapeutic agents including cisplatin, adriamycin and vincristine as well as rituximab. However, cytotoxic effect of these chemotherapeutic agents and rituximab was improved in combination of metformin in both RSCL and RRCLs. To us surprise, a better synergistic inhibition of cell proliferation was found in RRCLs as a result of combination of metformin and chemotherapeutic agents or rituximab, suggesting that intracellular signaling pathway induced by metformin might not be overlapped to that by chemotherapeutic agent and rituximab. Notably, it has known that in RRCLs, the level of proapototic proteins, BAX, BAK, is relatively low compared to in RSCL decreased, but the expression of anti-apoptotic protein and AMPK activity is increased and dysregulation of mTOR pathway is found. Our data showed that metformin restored dysregulation of mTOR pathway in RRCLs, since activation of p70S6K and S6K posphorylation was decreased. At the same time, expression of BAX and BAK was increased and that of anti-apoptotic proteins was decreased.
Metformin enhances rituximab-induced and chemotherapy-induced apoptosis via mTOR inhibition in rituximab-resistant NHL.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 610.
Abstract 614: ErbB-2 Suppresses Notch-1 Signaling by Regulating Jagged-1 Localization in ErbB-2 positive breast cancer
Authors: Mehta Kinnari , Meeke Kathleen , Patel Parul , Miele Lucio , Osipo Clodia 
Published: February 2011

Abstract
ErbB-2 is amplified and overexpressed in 20-30% of breast tumors. Today, ErbB-2 positive breast cancers are treated with trastuzumab plus chemotherapy. In spite of dramatic improvements in survival for women with ErbB-2+ breast tumors, resistance remains a major problem in metastatic disease. We have recently published that ErbB-2 suppresses Notch-1 activity and this is reversed by trastuzumab or a dual EGFR/ErbB-2 tyrosine kinase inhibitor similar to lapatinb. Furthermore, we demonstrated that trastuzumab resistance is reversed with a Notch-1 siRNA or a gamma-secretase inhibitor (GSI). Coincidentally, co-overexpression of Notch-1 and its ligand, Jagged-1, in breast cancer have been associated with the poorest overall survival. We know that activated Notch-1 plays an important role in ErbB-2 positive breast cancer and trastuzumab resistance; however, the precise mechanism by which Notch-1 is activated is not yet known. Thus, we hypothesized that overexpression of ErbB-2 inhibited expression and/or cell surface localization of Jagged-1 to suppress Notch-1 activity. This would be reversed in response to anti-ErbB-2 treatment. The results demonstrated that trastuzumab or lapatinib treatment of SKBr3 cells increased protein expression of Jagged-1 by Flow Cytometry. Notch-1 and Jagged-1 co-localized with early endosome antigen-1 (EEA-1) to submembraneous endosomes in ErbB-2 positive breast cancer cells as measured by confocal immunofluorescence. However upon trastuzumab treatment, Notch-1 and Jagged-1 exited EEA-1 positive vesicles and Notch-1 accumulated in the nucleus while Jagged-1 localized to the cell membrane. Cell surface biotinylation assays showed that Jagged-1 was enriched on the cell surface in response to trastuzumab treatment and this was mimicked by expression of K44A Dynamin. Cell surface accumulation of Jagged-1 was associated with an increase in Notch-1 transcriptional activity as measured by an increase in Deltex1 mRNA by real-time PCR. Conversely, knockdown of Jagged-1 by siRNA in SKbr3 and BT474 cells prevented the trastuzumab-induced increase in Deltex1 mRNA. Co-culture studies confirmed that culturing SKBr3 cells with fibroblast-expressing Jagged-1 or DLL4 increased Notch activity as measured by a CBF-1/Notch reporter assay. Taken together, these results suggest that ErbB-2 suppresses Notch-1 activity by retention of Jagged-1 or possibly other Notch ligands within early endosomes, which may be reversed by trastuzumab or lapatinib treatment.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 614.
Abstract 618: Role of multidrug resistance transporters in the biological response to trastuzumab-cytotoxic drug conjugates
Authors: Guo Jun , Li Guangmin , Phillips Gail D. Lewis 
Published: February 2011

Abstract
Trastuzumab-DM1 (T-DM1, TMAb-mcc-DM1, trastuzumab emtansine) is an antibody-cytotoxic drug conjugate that is composed of the maytansine derivative DM1 directly coupled, via a thioether SMCC linker, to trastuzumab. T-DM1 is currently undergoing clinical evaluation in metastatic HER2-positive breast cancer patients. T-DM1 has been shown to retain all of the mechanisms of action of trastuzumab and to deliver DM1 to HER2-overexpressing tumor cells. In the present study, we investigated potential mechanisms of resistance to T-DM1 and other trastuzumab conjugates, including a different class of anti-microtubule drugs, the auristatins (MMAE and MMAF). Expression of selected multi-drug resistance (MDR) transporters MDR1, MRP1, MRP3 and BCRP was determined by qRT-PCR (Taqman). MDR1 was expressed at moderate levels by only one line, while expression of MRP3 occurred in several HER2-overexpressing cell lines. Cell viability assays with either free drugs (DM1 or MMAE) or the respective trastuzumab conjugates showed that all lines were sensitive to treatment with these agents. The NCI-AdrRes line, which expresses high levels of MDR1, was transfected to overexpress HER2 and used as a positive control. This line was resistant to treatment with DM1 or MMAE, consistent with previous reports that these drugs are substrates for MDR1. Additional studies were performed with the clinical conjugate, T-DM1, on the HER2-amplified breast cancer line SK-BR-3 transfected to express either MDR1, MRP1, MRP3 or BCRP, focusing on the clinical conjugate, T-DM1. In cell proliferation assays, both NCI-AdrRes/HER2 and SK-BR-3/MDR1 were resistant to free DM1, and the addition of XR9051 (a specific MDR1 inhibitor) reversed this resistance. Although the sensitivity to T-DM1 for both cell lines was restored by the addition of XR9051, NCI-AdrRes/HER2 showed more resistance to T-DM1 in the absence of XR9051. SK-BR-3 cells expressing MRP1 or BCRP maintained sensitivity to free and conjugated drugs, while cells expressing MRP3 showed a very modest induction of resistance only at high drug concentrations. The effects of linker stability were also investigated by comparing trastuzumab conjugates comprised of stable vs. cleavable (reducible or protease-sensitive) linkers. MDR1 expressing cells showed relatively more resistance to conjugates with cleavable linkers, presumably due to efflux of free drug upon release after linker cleavage. Together, these data show that, of the MDR transporters studied, only MDR1 confers high level resistance to trastuzumab-cytotoxic drug conjugates comprised of DM1 or auristatins, and that linking the drug through a stable linker may allow evasion of drug efflux through MDR-mediated mechanisms.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 618.
Abstract 620: Addition of silibinin to EGFR-TKIs overcomes T790M-mediated drug resistance
Authors: Rho Jin Kyung , Choi Yun Jung , Choi Su Jin , Cheon Gi Jeong , Kim Hye-Ryoun , Kim Cheol Hyeon , Choi Chang-Min , Lee Jae Cheol 
Published: February 2011

Abstract
Although epidermal growth factor receptor EGFR tyrosine kinase inhibitors (EGFR-TKIs) produce an initially exhibit an initial dramatic response in lung cancer patients harboring a mutation in the EGFR gene, development of acquired resistanceis almost inevitable. The secondary mutation of T790M is associated with approximately one- half of the cases of acquired resistance. In this study, we investigated whether addition of silibinin to gefitinib or erlotinib could overcome T790M-mediated drug resistance considering that silibinin has various anti-tumor effects including EGFR modulation. Silibinin selectively reduced the activity of the EGFR family (EGFR, HER2 and ErbB3) in lung cancer cells with EGFR mutations, but not in those harboring wild type. In primary and acquired resistant cells with T790M, addition of silibinin enhanced the ability of EGFR-TKIs to down-regulate EGFR signals and to inhibit cell growth. Similarly, the combination of silibinin and erlotinib effectively suppressed the tumor growth in erlotinib resistance-bearing PC-9 xenografts. The results indicate that In conclusion, the addition of silibinin to EGFR-TKIs is can be a promising strategy to overcome T790M-mediated drug resistance.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 620.