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Novel HER2 Aptamer Selectively Delivers Cytotoxic Drug to HER2-positive Breast Cancer Cells in Vitro

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      Abstract

      BackgroundAptamer-based tumor targeted drug delivery system is a promising approach that may increase the efficacy of chemotherapy and reduce the related toxicity. HER2 protein is an attractive target for tumor-specific drug delivery because of its overexpression in multiple malignancies, including breast, gastric, ovarian, and lung cancers.MethodsIn this paper, we developed a new HER2 aptamer (HB5) by using systematic evolution of ligands by exponential enrichment technology (SELEX) and exploited its role as a targeting ligand for delivering doxorubicin (Dox) to breast cancer cells in vitro.ResultsThe selected aptamer was an 86-nucleotide DNA molecule that bound to an epitope peptide of HER2 with a Kd of 18.9 nM. The aptamer also bound to the extracellular domain (ECD) of HER2 protein with a Kdof 316 nM, and had minimal cross reactivity to albumin or trypsin. In addition, the aptamer was found to preferentially bind to HER2-positive but not HER2-negative breast cancer cells. An aptamer-doxorubicin complex (Apt-Dox) was formulated by intercalating Dox into the DNA structure of HB5. The Apt-Dox complex could selectively deliver Dox to HER2-positive breast cancer cells while reducing the drug intake by HER2-negative cells in vitro. Moreover, Apt-Dox retained the cytotoxicity of Dox against HER2-positive breast cancer cells, but reduced the cytotoxicity to HER2-negative cells.ConclusionsThe results suggest that the selected HER2 aptamer may have application potentials in targeted therapy against HER2-positive breast cancer cells.

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      Efficacy and safety of trastuzumab as a single agent in first-line treatment of HER2-overexpressing metastatic breast cancer.

      To evaluate the efficacy and safety of first-line, single-agent trastuzumab in women with HER2-overexpressing metastatic breast cancer. One hundred fourteen women with HER2-overexpressing metastatic breast cancer were randomized to receive first-line treatment with trastuzumab 4 mg/kg loading dose, followed by 2 mg/kg weekly, or a higher 8 mg/kg loading dose, followed by 4 mg/kg weekly. The objective response rate was 26% (95% confidence interval [CI], 18.2% to 34.4%), with seven complete and 23 partial responses. Response rates in 111 assessable patients with 3+ and 2+ HER2 overexpression by immunohistochemistry (IHC) were 35% (95% CI, 24.4% to 44.7%) and none (95% CI, 0% to 15.5%), respectively. The clinical benefit rates in assessable patients with 3+ and 2+ HER2 overexpression were 48% and 7%, respectively. The response rates in 108 assessable patients with and without HER2 gene amplification by fluorescence in situ hybridization (FISH) analysis were 34% (95% CI, 23.9% to 45.7%) and 7% (95% CI, 0.8% to 22.8%), respectively. Seventeen (57%) of 30 patients with an objective response and 22 (51%) of 43 patients with clinical benefit had not experienced disease progression at follow-up at 12 months or later. The most common treatment-related adverse events were chills (25% of patients), asthenia (23%), fever (22%), pain (18%), and nausea (14%). Cardiac dysfunction occurred in two patients (2%); both had histories of cardiac disease and did not require additional intervention after discontinuation of trastuzumab. There was no clear evidence of a dose-response relationship for response, survival, or adverse events. Single-agent trastuzumab is active and well tolerated as first-line treatment of women with metastatic breast cancer with HER2 3+ overexpression by IHC or gene amplification by FISH.
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        Multinational study of the efficacy and safety of humanized anti-HER2 monoclonal antibody in women who have HER2-overexpressing metastatic breast cancer that has progressed after chemotherapy for metastatic disease.

        Overexpression of the HER2 protein occurs in 25% to 30% of human breast cancers and leads to a particularly aggressive form of the disease. Efficacy and safety of recombinant humanized anti-HER2 monoclonal antibody as a single agent was evaluated in women with HER2-overexpressing metastatic breast cancer that had progressed after chemotherapy for metastatic disease. Two hundred twenty-two women, with HER2-overexpressing metastatic breast cancer that had progressed after one or two chemotherapy regimens, were enrolled. Patients received a loading dose of 4 mg/kg intravenously, followed by a 2-mg/kg maintenance dose at weekly intervals. Study patients had advanced metastatic disease and had received extensive prior therapy. A blinded, independent response evaluation committee identified eight complete and 26 partial responses, for an objective response rate of 15% in the intent-to-treat population (95% confidence interval, 11% to 21%). The median duration of response was 9.1 months; the median duration of survival was 13 months. The most common adverse events, which occurred in approximately 40% of patients, were infusion-associated fever and/or chills that usually occurred only during the first infusion, and were of mild to moderate severity. These symptoms were treated successfully with acetaminophen and/or diphenhydramine. The most clinically significant adverse event was cardiac dysfunction, which occurred in 4.7% of patients. Only 1% of patients discontinued the study because of treatment-related adverse events. Recombinant humanized anti-HER2 monoclonal antibody, administered as a single agent, produces durable objective responses and is well tolerated by women with HER2-overexpressing metastatic breast cancer that has progressed after chemotherapy for metastatic disease. Side effects that are commonly observed with chemotherapy, such as alopecia, mucositis, and neutropenia, are rarely seen.
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          Structure of the extracellular region of HER2 alone and in complex with the Herceptin Fab.

          HER2 (also known as Neu, ErbB2) is a member of the epidermal growth factor receptor (EGFR; also known as ErbB) family of receptor tyrosine kinases, which in humans includes HER1 (EGFR, ERBB1), HER2, HER3 (ERBB3) and HER4 (ERBB4). ErbB receptors are essential mediators of cell proliferation and differentiation in the developing embryo and in adult tissues, and their inappropriate activation is associated with the development and severity of many cancers. Overexpression of HER2 is found in 20-30% of human breast cancers, and correlates with more aggressive tumours and a poorer prognosis. Anticancer therapies targeting ErbB receptors have shown promise, and a monoclonal antibody against HER2, Herceptin (also known as trastuzumab), is currently in use as a treatment for breast cancer. Here we report crystal structures of the entire extracellular regions of rat HER2 at 2.4 A and human HER2 complexed with the Herceptin antigen-binding fragment (Fab) at 2.5 A. These structures reveal a fixed conformation for HER2 that resembles a ligand-activated state, and show HER2 poised to interact with other ErbB receptors in the absence of direct ligand binding. Herceptin binds to the juxtamembrane region of HER2, identifying this site as a target for anticancer therapies.
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            Author and article information

            Affiliations
            [1 ]Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China
            [2 ]Cancer Institute & Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100021, China
            [3 ]Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100073, China
            Contributors
            Journal
            J Transl Med
            J Transl Med
            Journal of Translational Medicine
            BioMed Central
            1479-5876
            2012
            20 July 2012
            : 10
            : 148
            22817844
            3583217
            1479-5876-10-148
            10.1186/1479-5876-10-148
            Copyright ©2012 Liu et al.; licensee BioMed Central Ltd.

            This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

            Categories
            Research

            Medicine

            aptamer, her2, breast cancer, tumor targeted therapy

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