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      TMZ-BioShuttle – a reformulated Temozolomide

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          Abstract

          There is a large number of effective cytotoxic drugs whose side effect profile, efficacy, and long-term use in man are well understood and documented over decades of use in clinical routine e.g. in the treatment of recurrent glioblastoma multiforme (GBM) and the hormone-refractory prostate cancer (HRPC). Both cancers are insensitive against most chemotherapeutic interventions; they have low response rates and poor prognoses. Some cytotoxic agents can be significantly improved by using modern technology of drug delivery or formulation. We succeeded to enhance the pharmacologic potency with simultaneous reduction of unwanted adverse reactions of the highly efficient chemotherapeutic temozolomide (TMZ) as an example. The TMZ connection to transporter molecules (TMZ-BioShuttle) resulted in a much higher pharmacological effect in glioma cell lines while using reduced doses. This permits the conclusion that a suitable chemistry could realize the ligation of pharmacologically active, but sensitive and highly unstable pharmaceutical ingredients without functional deprivation. The re-formulation of TMZ to TMZ-BioShuttle achieved a nearly 10-fold potential of the established pharmaceutic TMZ far beyond the treatment of brain tumors cells and results in an attractive reformulated drug with enhanced therapeutic index.

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          Most cited references44

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          Correlation of O6-methylguanine methyltransferase (MGMT) promoter methylation with clinical outcomes in glioblastoma and clinical strategies to modulate MGMT activity.

          Resistance to alkylating agents via direct DNA repair by O(6)-methylguanine methyltransferase (MGMT) remains a significant barrier to the successful treatment of patients with malignant glioma. The relative expression of MGMT in the tumor may determine response to alkylating agents, and epigenetic silencing of the MGMT gene by promoter methylation plays an important role in regulating MGMT expression in gliomas. MGMT promoter methylation is correlated with improved progression-free and overall survival in patients treated with alkylating agents. Strategies to overcome MGMT-mediated chemoresistance are being actively investigated. These include treatment with nontoxic pseudosubstrate inhibitors of MGMT, such as O(6)-benzylguanine, or RNA interference-mediated gene silencing of MGMT. However, systemic application of MGMT inhibitors is limited by an increase in hematologic toxicity. Another strategy is to deplete MGMT activity in tumor tissue using a dose-dense temozolomide schedule. These alternative schedules are well tolerated; however, it remains unclear whether they are more effective than the standard dosing regimen or whether they effectively deplete MGMT activity in tumor tissue. Of note, not all patients with glioblastoma having MGMT promoter methylation respond to alkylating agents, and even those who respond will inevitably experience relapse. Herein we review the data supporting MGMT as a major mechanism of chemotherapy resistance in malignant gliomas and describe ongoing studies that are testing resistance-modulating strategies.
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            Click Chemistry: Diverse Chemical Function from a Few Good Reactions.

            Examination of nature's favorite molecules reveals a striking preference for making carbon-heteroatom bonds over carbon-carbon bonds-surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water. Nucleic acids, proteins, and polysaccharides are condensation polymers of small subunits stitched together by carbon-heteroatom bonds. Even the 35 or so building blocks from which these crucial molecules are made each contain, at most, six contiguous C-C bonds, except for the three aromatic amino acids. Taking our cue from nature's approach, we address here the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compounds and combinatorial libraries through heteroatom links (C-X-C), an approach we call "click chemistry". Click chemistry is at once defined, enabled, and constrained by a handful of nearly perfect "spring-loaded" reactions. The stringent criteria for a process to earn click chemistry status are described along with examples of the molecular frameworks that are easily made using this spartan, but powerful, synthetic strategy.
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              Isolation of a human prostate carcinoma cell line (DU 145).

              A long-term tissue culture cell line has been derived from a human prostate adenocarcinoma metastatic to the brain. The cell line, DU 145, has been passaged 90 times in vitro over a period of 2 years. The cells are epithelial, grow in isolated islands on plastic Petri dishes, and form colonies in soft agar suspension culture. Karyotypic analysis demonstrates an aneuploid human karyotype with a modal chromosome number of 64. Distinctive marker chromosomes (a translocation Y chromosome, metacentric minute chromosomes and three large acrocentic chromosomes) have been identified. Electron microscopy of the original tumor tissue and of the tissue culture cell line show a remarkable similarity in cell organelle structure.
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                Author and article information

                Journal
                Int J Med Sci
                ijms
                International Journal of Medical Sciences
                Ivyspring International Publisher (Sydney )
                1449-1907
                2008
                15 September 2008
                : 5
                : 5
                : 273-284
                Affiliations
                1. German Cancer Research Center, Division of Biophysics of Macromolecules, INF 580, D-69120 Heidelberg, Germany
                2. German Cancer Research Center, Dept. of Molecular Toxicology, INF 280, D-69120 Heidelberg, Germany
                3. University of Heidelberg, Institute of Pathology, INF 220, D-69120 Heidelberg, Germany
                4. German Cancer Research Center, Central Peptide Synthesis Unit, INF 580, D-69120 Heidelberg, Germany
                5. German Cancer Research Center, Dept. of Structural Analysis of Gene Structure and Function, INF 280, D-69120 Heidelberg, Germany
                6. University of Heidelberg, Dept. of Radiation Oncology, INF 400, D-69120 Heidelberg, Germany
                Author notes
                ✉ Correspondence to: Dr. Klaus Braun, German Cancer Research Center (DKFZ), Dept. Molecular Toxicology, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany. Phone: +49 6221-42 2495; Fax: +49 6221-42 3375; e-mail: k.braun@ 123456dkfz.de

                Conflict of Interest: We declare no conflicts of interest.

                Article
                ijmsv05p0273
                2536715
                18797509
                bb5152b9-d710-45a3-9566-dfd1244c46f6
                © Ivyspring International Publisher. This is an open-access article distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by-nc-nd/3.0/). Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited.
                History
                : 18 August 2008
                : 12 September 2008
                Categories
                Research Paper

                Medicine
                bioshuttle,drug delivery,carrier molecules,facilitated transport,reformulation,temozolomide (tmz),glioblastoma multiforme (gbm)

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