bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abstract P6-15-04: Targeting the PI3K Pathway Enhances the Effect of PARP-1 Inhibition in BRCA1 Deficient Breast Cancer Cells
Authors: Kimbung S , Aaltonen K , Gruvberger-Saal S , Berglund P , Hedenfalk I. 
Published: April 2011

Abstract
Background: Available targeted therapies have improved the prognosis for many women diagnosed with breast cancer. However, more than 15% of cases do not benefit from these targeted agents. Amongst these are tumours with Breast cancer 1 (BRCA1) dysfunction, triple-negative and basal-like breast cancers, which remain a treatment challenge and are associated with a poor outcome. New approaches to specifically target these groups of breast tumors are needed. The DNA damage repair defects associated with lack of BRCA1 confers sensitivity to poly-(ADP-ribose) polymerase 1 (PARP-1) inhibitors. Furthermore, most BRCA1 mutated tumours do not express the phosphatase and tensin homolog (PTEN) implying activation of the phosphatidylinositol-3 kinase (PI3K) pathway which promotes cell survival and resistance to apoptosis. The aim of this study was to investigate if co-targeting the PI3K pathway can improve the response of BRCA1 mutated cells to PARP-1 inhibition.
Material and methods:, Two BRCA1 and PTEN deficient breast cancer cell lines; MDA-MB-436 and SUM149, were treated with the PARP-1 inhibitor AG14361 (1-(4-dimethylaminomethyl-phenyl)-8-9-dihydro-7H-2,7,9a-benzo[cd]azulen-6-one) and the PI3K inhibitor LY294002 (2-(4-morpholinyl)-8-phenyl-chromone), as single agents and in combination. Cytotoxicity was estimated using the sulpho-rhodamine B assay while cell cycle phase distribution and DNA integrity were analyzed by flow cytometry.
Results: AG14361 induced DNA damage leading to G2/M arrest and decreased viability. LY294002, on the other hand, affected the cell cycle by arresting cells in G1. Importantly, combining AG14361 with LY294002 further decreased survival (P&lt;0.001) with a concomitant decrease in G2/M (P&lt;0.05).
Discussion: This observation may indicate a combination specific up-regulation of apoptosis and suggests that LY294002 potentiates the effects of AG14361. Our results may represent an improved selective targeted treatment strategy for BRCA1 deficient breast cancers and other cancers with DNA damage repair defects and activated PI3K signalling.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-04.
Abstract P6-15-05: A Cyclin-Dependent Kinase Inhibitor P276 Inhibits Growth of Breast Cancer Cell Lines Including Basal-Type/Triple-Negative Alone and in Combination with Chemotherapeutic Drugs
Authors: Sharma S , Rathos M , Manohar S , Joshi K , Badhwar A , Kharas F , Sonawane V , Chaudhuri U , Joshi K. 
Published: April 2011

Abstract
Background: Development of novel agents and drug combinations are urgently needed for the treatment of breast cancer especially triple negative breast cancer (TNBC). P276 is a potent cyclin-dependent kinase inhibitor with excellent antiproliferative activity against various human cancer cell lines. Here, we report the activity of P276, as a single agent and in combination with paclitaxel or gemcitabine/carboplatin in TNBC cell lines.
Material and Methods: In vitro effect of P276 on breast cancer cell lines was determined by cytotoxicity assay, flow cytometry, western blotting and immunofluorescence studies. The antiangiogenic potential of P276 was evaluated using HIF-1 a and VEGF inhibition assay, wound healing and tube formation. In vivo efficacy was studied using human xenograft models in SCID and nude mice.
Results: Human breast cancer cell lines including TNBC, treated with P276 were found to be highly susceptible with IC50 ranging from 0.3 to 1.0 mM. In MCF-7 (Her2-, BRCA+/−) and MDA-MB-231 (ER-, PR-, Her2-). P276 significantly down regulated cell cycle proteins pRbser780, cyclin D1, Cdk4 and antiapoptotic protein Bcl-2 followed by 80-85% apoptosis. P276 treatment also lead to the inhibition of PARP enzyme activity or PARP cleavage depending on the cell type. Interestingly, P276 inhibited the key angiogenic mediators HIF-1 a and VEGF with IC50 of 0.095mM and 0.31mM respectively in reporter gene based assays. These antiangiogenic effects were confirmed by immunofluorescence and migration studies in TNBC cell lines and endothelial tube formation. In breast cancer patient derived tumor cell line MAXF 401 (basal like) xenografts in nude mice, cyclical dosing of P276 showed growth inhibition of 71%. Moreover, combination studies of P276 with paclitaxel or gemcitabine plus carboplatin showed synergistic effect in TNBC cell lines. Discussion: Our studies provide compelling evidence for the clinical development of P276 for the treatment of triple negative breast cancer either as monotherapy or in combination with paclitaxel or gemcitabine/carboplatin.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-05.
Abstract P6-15-10: Targeting Delta-Like 4 Ligand (DLL4)/Notch Signaling by a Novel Anti-DLL4 Antibody Inhibits Tumor Growth through Altering Cancer Stem Cell and Epithelial-to-Mesenchymal Transition-Associated Genes in Triple Negative Breast Cancer
Authors: Yen W-C , Fischer M , Beviglia L , Yeung P , Kapoun A , Wang M , Lewicki J , Gurney A , Hoey T. 
Published: April 2011

Abstract
Triple negative breast cancer (TNBC, ER-, PR-Her2-) accounts for 10% of all types of breast cancer and is known to be particularly aggressive and refractory to current therapies. Chemotherapeutic agents, such as taxanes, are currently the only treatment option for this type of breast cancer. However, these treatments often result in local and systemic relapse. While several promising targeted agents have improved the relapse rate in the combination with chemotherapy in patients with pathologic complete response, those who do not achieve pathologic complete response still have a poor prognosis. We previously demonstrated that interfering with Deltalike 4 ligand (DLL4)/Notch signaling by an anti-DLL4 antibody decreased tumor growth and delayed tumor recurrence following paclitaxel treatment through reducing breast cancer stem cell fraction and tumorigenicity (Proc Am Asso Cancer Res. 51:4, 2010). CD44+/CD24low cells have been demonstrated to be highly tumorigenic in breast tumors and are associated with treatment resistance (PNAS U S A, 106: 13820-13825, 2009). To gain insights into the mechanism of action of anti-DLL4-mediated TNBC growth inhibition, we evaluated the effect of anti-DLL4 on breast cancer CD44+/CD24low the expression patterns of a list of genes involved in sternness, differentiation, and key stem cell signaling pathways in TNBC xenograft tumors following paclitaxel with and without antibody treatment in vivo. Our data showed that paclitaxel treatment resulted in significant changes of gene expression patterns in the CD44+/CD24low cells in the residual tumors. We further analyzed these genes and identified several genes related to Notch signaling, stem cell maintenance and epithelial-to-mesenchymal transition that were modulated differentially by treatment with paclitaxel and/or anti-DLL4. In a metastatic TNBC orthotopic tumor model, the anti-DLL4 treatment resulted in tumor growth inhibition at the primary site and distant organs. Taken together, our findings suggest that targeting DLL4 may improve the efficacy of current treatments, delay tumor recurrence, and reduce metastatic growth in TNBC.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-10.
Abstract P6-15-14: Inhibit SIAH E3 Ligase, a Downstream Signaling Module Required for the HER2/EGFR/RAS Signal Transduction, To Block Tumorigenesis and Metastasis of Highly Invasive Human Breast Cancers
Authors: Tang AH , Park CH , Liao Y , Ahmed AU , Reed NR , Hesse SE , Lingle WL , Jimenez RE , Tang AH. 
Published: April 2011

Abstract
The central importance of the HER2/Neu/EGFR/RAS signaling pathway has been well established in the growth, invasion and metastasis of human breast cancer, even though oncogenic RAS mutations are rare in breast cancer, activation of the tumor-promoting ERBB/RAS/MEK/MAPK pathway has been consistently documented in high-grade breast tumors. As such, novel approaches to inhibit activated ERBB/RAS signals constitute important measures to block tumor growth and metastasis in mammary tumors. In this study, instead of targeting an upstream signaling component such as HER2/EGFR/RAS, we targeted the most downstream signaling module identified in the RAS pathway — the SIAH proteolytic machinery. SIAH is an evolutionarily conserved RING E3 ligase that is a critical “gatekeeper” required for RAS signal transduction in human cancer cells. SIAH is specifically expressed in tumor cells in 120 human breast cancer patients examined so far. The increased SIAH expression is correlated with increased grades and aggressiveness of human breast cancer. We then asked whether inhibiting the gatekeeper function of SIAH would be effective in blocking mammary tumorigenesis and metastasis in human breast cancer. Our results indicated that SIAH2-deficiency successfully abolished tumor growth of three breast cancer cell lines (MDA-MB-231, MDA-MB-435 and MDA-MB-468) in soft agar assays as well as in athymic nude mice. Importantly, by inhibiting SIAH2 function in highly aggressive human breast cancer cells, we are able to completely block tumorigenesis and metastasis of two highly invasive and metastatic human breast cancer cell lines (MDA-MB-231 and MDA-MB-435). These findings suggest that SIAH2 may be an attractive new therapeutic target for novel breast cancer therapy and developing anti-SIAH molecules will aid in expanding our arsenal of effective anticancer therapies. More effective breast cancer treatments may be obtained by multi-pronged synergistic inhibitions at upstream (HER2/EGFR membrane receptors), midstream (RAS/RAF/MEK/mTOR) and downstream (SIAH E3 ligase) signaling modules in the HER2/EGFR/RAS pathway in parallel. Thus, by attacking the growth-promoting ERBB/RAS pathway at multiple signaling modules simultaneously, we may be in a great position to halt the genesis, progression and metastasis of human breast cancer.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-14.
Abstract P6-15-16: LIV-1 Antibody-Drug Conjugate: A Novel Therapeutic Agent for Breast Cancer
Authors: Smith LM , Sussman D , Nesterova A , Westendorf L , Duniho S , Anderson M , Mbow B , Gregoire A , Hunter J , Whiting N , Law CL , Benjamin DR. 
Published: April 2011

Abstract
LIV-1, also known as SLC39A6 or ZIP6, is a member of the zinc transporter family and was first identified as an estrogen-inducible gene in breast cancer. LIV-1, as a downstream target of STAT3, promotes the epithelial to mesenchymal transition that is important in the malignant progression to metastasis. Consistent with its role in cancer, we determined by immunohistochemical (IHC) analysis that LIV-1 is expressed in 86% (n=22) of estrogen receptor-positive (ER+), hormone-treated tumors (both primary and metastatic sites), and in 65% (n=20) of ER-/PR-/Her2- (triple-negative) breast cancers. In healthy human tissues, LIV-1 expression is limited to hormonally-regulated organs (prostate, uterus, and breast). We generated an antibody-drug conjugate (ADC) consisting of a humanized anti-LIV-1 mAb conjugated to the antitubulin agent monomethyl auristatin E (MMAE), via a plasma stable, enzyme-cleavable linker (vc). The humanized LIV-1 mAb bound with high affinity to both human and cynomolgous LIV-1 (2-4 nM). In vitro, anti-LIV-1-vcMMAE showed specific cytotoxic activity against a MCF-7 cell line with an IC50= 78 ng/ml. In vivo studies also demonstrated antitumor activity of anti-LIV-1-vcMMAE in preclinical xenograft models, including MCF-7 breast cancer cell line, with significant delay of tumor growth compared to control groups. The broad expression of LIV-1 in both hormonally-treated and triple-negative tumors and the limited expression in vital organs make LIV-1 an excellent target for an ADC. These findings support the further development of anti-LIV-1-vcMMAE as a promising therapeutic agent for the treatment of ER+ and triple-negative breast cancers.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-16.
Abstract P6-15-20: Development of PEA-15-Based Therapy in Breast Cancer in a Preclinical Study
Authors: Xie X , Bartholomeusz C , Maxwell DS , Peng Z , Kazansky A , Bornmann WG , Ueno NT. 
Published: April 2011

Abstract
Background: PEA-15 (phosphoprotein enriched in astrocytes, 15 kDa) has tumor suppressor properties in both breast and ovarian cancer cells. Overexpression of PEA-15 in MDA-MB-468 triple-negative breast cancer cells using adenoviral vector (Ad.PEA-15) inhibited cell growth by inducing apoptosis. Treatment with Ad.PEA-15 led to significant regression of tumors in mice, indicating that PEA-15 could have therapeutic potential in breast cancer. PEA-15 exerts its antitumor activity by binding to ERK in the cytoplasm and preventing its translocation into the nucleus, thereby inhibiting ERK-dependent transcription and cell proliferation. Because ERK inhibitors have been shown to be toxic, in this study, we developed PEA-15 mimetic peptides as a therapeutic agent in breast cancer. These peptides, which are expected to be less toxic because of their ability to mimic PEA-15, are proposed to inhibit cell proliferation by sequestering ERK in the cytoplasm.
Material and Methods: PEA-15 mimetic peptides were designed and synthesized based on structural analysis of linear segments from the C-terminal end of PEA-15, which is one of the two regions that are presumably critical for ERK binding, using nuclear magnetic resonance spectroscopy. These synthetic peptides were labeled with FAM to enable determination of their subcellular localization. The PULSin reagent was used as a delivery reagent for peptide penetration into cancer cells. The penetration ability of these peptides into HeLa and MDA-MB-468 cells was analyzed by fluorescence microscope and fluorescence-activated cell sorting. Their effect on ERK subcellular localization was examined by cell-fractionation analysis. Their impact on cell survival was determined by trypan blue viability assay and propidium iodide staining. Results: Ten peptides were designed and synthesized based on the C-terminal segments of PEA-15. Three of these FAM-labeled synthetic peptides delivered with the PULSin reagent were able to penetrate HeLa and MDA-MB-468 cells with 80-90% and 30-40% efficiency, respectively. Further, these peptides redirected ERK into the cytoplasm from the nucleus in MDA-MB-468 cells and caused 31% reduction in viability of HeLa cells as compared to the untreated control. Ongoing studies are evaluating PEA-15 peptides for their ability to interact with ERK using ELISA. In the future, we will also test their therapeutic efficacy and safety using a xenograft breast cancer model.
Discussion: Previous studies revealed that PEA-15 has antitumor activity against breast and ovarian cancer cells by sequestering ERK in the cytoplasm. Due to the toxicity of ERK enzymatic inhibitors, we developed PEA-15 mimetic peptides and demonstrated their therapeutic potential for breast cancer, which may provide opportunities for breast cancer patients who currently have limited treatment options.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-20.
Abstract PD01-05: A Combination of HDAC Inhibitor Entinostat (MS-275), All Trans Retinoic Acid (ATRA) and Chemotherapy Drug(s) Causes Regression of Established Xenografts of Triple Negative Breast Cancer
Authors: Nguyen NK , Korangath P , Sabnis G , Brodie A , Ordentlich P , Stearns V , Sukumar S. 
Published: April 2011

Abstract
Triple negative breast cancer (TNBC) is a subgroup of breast cancer that rapidly develops resistance to chemotherapy. Currently, TNBC patients are treated with anthracycline and taxane-based regimens. These treatments result in some improvements in the clinical outcomes; however, they are associated with poor prognosis. Also, endocrine therapies are ineffective since the tumors do not express the estrogen receptor. Recent studies have shown that histone deacetylase (HDAC) inhibitors could reverse the epigenetic profile of some genes, including ER, EGFR, and RAR≥2. We have recently shown that treatments that combine the HDAC inhibitor, Entinostat (MS-275), with the aromatase inhibitor, Letrozole, result in regression of xenografts of MDA-MB-231 breast cancer cells. Since RAR≥2 is re-expressed as well, we reasoned that combining epigenetic therapy using MS-275, with differentiation therapy using a RAR≥2 agonist (ATRA) will provide an effective combination of drugs against TNBC. We also examined possible potentiation of anticancer activity of these agents by low nontoxic doses of chemotherapy (doxorubicin and paclitaxel). In vitro, human TNBC cell lines, MDA-MB-231, HCC 1143, SUM159, SUM149 and BT20 responded significantly better to the triple combination compared to the drugs used singly or in combination with MS-275. Upon treatment, re-expression of the silenced RAR≥2 and downstream effectors was observed in the cell lines in vitro and in tumor xenografts of MDA-MB-231 cells. Subcutaneous tumor growth in immunodeficient mice was strongly inhibited (10/14 significant regression) using a combination of MS-275, ATRA and low dose Doxorubicin, compared to the drugs administered singly or in combination with MS-275. No significant weight loss was observed in any of the groups. This combination was then used to treat tumor xenografts of SUM159, another TNBC cell line, and gave a promising result. Furthermore, combination of MS-275, ATRA, and a clinical dose of Paclitaxel can effectively inhibit growth of MDA-MB-231 and SUM159 cells. These results suggest that combination of HDAC inhibitor and RAR≥2 agonist with low dose chemotherapy has the potential to be an effective treatment against TNBC. This study provides encouraging new information for a nontoxic, and novel combination of drugs which could be effective against TNBC.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD01-05.
Abstract PD02-01: Human Breast Cancer Lymphovascular Tumoral Emboli and Micrometastasis Recapitulate an In Vitro Mammosphere Stem Cell Phenotype
Authors: Barsky SH , Graham CE , Llewellyn AL , Ye Y , Yearsley K. 
Published: April 2011

Abstract
Background: The existence of stem cells in human cancers has been inferred by clonality experiments and marker studies in vitro and clinical observations in vivo concerning tumor recurrences and emerging drug resistance. We have studied the existence of stem cells in a human model of inflammatory breast cancer, termed MARY-X, a model which forms spheroids which are similar to normal tissue stem cell-derived mammospheres. Comparing MARY-X with common non-IBC breast carcinoma and normal cell lines, we found specific embryonal stem cell markers within the MARY-X spheroids. RT-PCR analyses of MARY-X also revealed the expression of transcriptional determinants essential for the pluripotency and self-renewal of human embryonal stem cells. Since MARY-X spheroids, when injected into mice, form tumors with florid lymphovascular emboli that give rise to micrometastases in numerous organs, we wondered whether tumor emboli and micrometastases from actual human cancers also recapitulated a mammosphere stem cell phenotype.
Material and Methods: We carried out laser capture microdissection of tumor emboli and lymph node micrometastases in 200 cases of human breast cancer including cases of both infiltrating ductal as well as lobular cancer. These cases included all of the common molecular classes of breast cancer including luminal A, luminal B, luminal C, Her-2/neu positive and triple negative including the basal subtype. The common denominator which was studied in all of these cases was the lymphovascular embolus and lymph node micrometastasis.
Results: By both RT-PCR and IHC, lymphovascular emboli and micrometastases exhibited five-ten fold higher stem cell markers including Stellar, H19, Rex-1, Nestin, CD133 and Aldehyde Dehydrogenase 1 (ALDH1) as well as stem cell transcriptional determinants including OCT4, SOX2, and Nanog than the non-embolic tumoral areas. In addition, stem cell signaling pathways specifically involved in self-renewal and pluripotency including Bmi-1, Hedgehog and Notch 3 were activated selectively within the lymphovascular tumor emboli and micrometastases.
These observations held true irrespective of the molecular class of breast cancer from which the embolus was derived and irrespective of the adhesion status (presence or absence of E-cadherin) of the embolus or micrometastasis.
Discussion: Our findings indicate that the lymphovascular embolus and micrometastasis is not simply a cellular fragment that detaches from the main tumor but rather represents a selection for a stem cell phenotype. This finding may explain the increased resistance of lymphovascular tumor emboli and micrometastases to chemotherapy and the decreased disease-free survival and poorer prognosis exhibited by patients with significant lymphovascular emboli and micrometastases.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD02-01.
Abstract PD02-05: Low Immunogenicity of Breast Cancer Stem Cells Leads to Selective Survival When Challenged with Trastuzumab and Natural Killer Cells
Authors: Honig A , Reim F , Becker K , Engel JB , Junker M , Dietl J , Wischhusen J. 
Published: April 2011

Abstract
Although trastuzumab (Herceptin) has substantially improved the overall survival of patients with mammary carcinomas, even initially well-responding tumors often become resistant. Considering that clinical efficacy of trastuzumab correlates with the infiltration of natural killer (NK) cells into the tumor site, we established a cell-culture-system to select for ovarian cancer and mammary carcinoma cells that survive a challenge by trastuzumab and NK cells. Under these conditions, NK cells can eliminate tumor cells either via antibody-dependent-cell-mediatedcytotoxicity (ADCC) or by direct recognition of tumor-associated ligands for NKG2D or DNAM-1. The most striking phenotypic alteration observed in immunoselected ovarian cancer cells was a down-regulation of HER2 expression, leading to an ADCC-resistant phenotype. All breast cancer cells tested (MCF7, SK-BR-3, MDA-MB231, BT474), however, failed to develop resistance in vitro. Instead, treatment with trastuzumab and polyclonal NK-cells resulted in the preferential survival of individual sphere-forming cells that displayed a CD44highCD24low ‘'cancer-stem-celllike” phenotype (CSC) and expressed significantly less HER2 compared with non-stem cells. Moreover, the molecular determinants for the direct recognition of transformed cells, most notably the NKG2D ligands MICA, MICB, ULBP1-4 and the DNAM-1 ligands CD112 and CD155, were virtually absent from CSC.
When immunoseleced breast cancer cells were then re-expanded, they mostly lost the observed phenotype and regenerated a tumor cell culture that displayed initial HER2 surface expression and ADCC susceptibility, but was enriched in CD44highCD24low CSC. This translated into increased clonogenicity in vitro and tumorigenicity in vivo. We provide evidence that recruition of NK-cells and induction of ADCC by trastuzumab may spare actual tumor-initiating-cells, which could explain clinical relapse. Moreover, our observation that “relapsed” in vitro cultures show identical HER2 surface expression and susceptibility toward ADCC suggests that administration of trastuzumab beyond relapse might be considered, especially when combined with proteasome inhibition which increase the expression of NKG2D ligands.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD02-05.