1. BASIC SCIENCE

ANNUAL REPORT FOR JOINT PROJECT

  1. Title of Project: Biological and structural studies on non-covalent interactions between novel platinum anticancer drugs and bio-molecules
  2. Duration: April 1, 2004 — March 31, 2006
  3. Project Organization
    1. Japanese Principal Investigator (JPI)
      Dr. Akira Odani (Associate Professor, Research Center for Materials Science, Nagoya University)
    2. U.S. Principal Investigator (USPI)
      Dr. Nicholas P. Farrell (Professor, Chemistry, Virginia Commonwealth University)
    3. Research Associate (Japanese / U.S.)
      Seiji Komeda, Ph. D ( JSPS Post-Doctral Fellow, Pharmacy, Osaka University of Pharmaceutical Sciences)
  4. Number of Participants
    1) Japanese side:  6  persons   2) US side:  6  persons
  5. Number of Exchanges in JFY 2004
    1. from Japan to US
      Seiji Komeda (Osaka University of Pharmaceutical Sciences)
        Duration: 2004.4.18-7.15
        Host Institution: Georgia Institute of Technology
      Akira Odani (Nagoya University)
        Duration: 2004.6.25-7.4
        Host Institution: Georgia Institute of Technology, Case Western Reserve University, University of California
    2. from US to Japan: None
  6. Activities of RA in JFY2004
    At Georgia Institute of Technology, the RA performed co-crystallization of DNA with cationic platinum(II) complexes and obtained more than 15 different drug-DNA crystals. X-ray crystal analysis on these single crystals has clearly revealed drug binding positions and the resulting DNA structures with super high resolution (1.07 — 1.5 A).
    A preliminary result was presented at 7th European Biological Inorganic Chemistry Conference (EUROBIC 7, Aug. 29 — Sep. 2, Garmisch-PartenKirchen, Germany).
  7. Status Report of Project Implementation and Scientific Achievements
    The objectives of this project are to develop cationic Pt(II) based anticancer drugs with potentially less side effects than currently used agents, in order to improve patient’s quality of life (QOL), and to elucidate a part of their anticancer mechanism. It is the foundation of this proposal that novel cellular uptake mechanisms as well as profiles of DNA binding by cationic platinum complexes differ significantly from that of neutral cisplatin and congeners. These differences can be used to develop new platinum-based drugs with a clinical profile complementary to cisplatin.
    Each of the groups (Nagoya Univ, Osaka Univ Pharma Sci, and Kansai Univ) have independently developed different types of cationic Pt(II) complexes, which are found to be highly active in in vitro cytotoxicity. Because of their positive charge, these cationic derivatives may initially react in a non-covalent manner with biomolecules through hydrogen-bonding and electrostatic interactions. For a more sophisticated interpretation of their structure-activity relationships, we plan to prepare new derivatives which are designed to only interact in a non-covalent manner with important biomolecules. Up to thirty derivatives of the cationic mono- and polynuclear Pt(II) complexes based on the structural formulas such as ternary [Pt(diimine)2]2+, [Ru(diimine)3]24+, cis-[Pt(Am)2(diphosphonate)]2-, [{cis-Pt(Am)2}2(μ-azolate)(μ-hydroxo)]2+ (Am = amine), are synthesized and characterized. The structure-activity dependence of the non-covalent interactions in Pt(II) complexes are studied at Nagoya Univ. The comparison across different types will allow the most important features contributing to antitumor activity to be identified and will be used to produce a profile of the most likely new drug candidate to emerge from this work.
    In order to choose biologically relevant Pt(II) complexes from those newly prepared by each group and to construct their structure-activity relationships, the Pt(II) complexes are biologically assessed by performing in vitro cytotoxicity assay, in vitro apoptosis induction assay, cellular uptake and cell cycle analysis. Osaka Univ Pharma Sci are basically responsible for these biological evaluation assays. Selected derivatives will be processed for in vivo anticancer activity in human xenograft models. New intellectual property stemming from the most promising selected Pt(II) complexes will be patented to ensure commercial interest for development.
    In parallel with the cytotoxicity and in vivo assays, investigations about the influence of Pt(II) complexes on relevant bio-molecules are to be expedited to find out insights of their anticancer mechanisms, since we believe the significant roles of the Pt(II) complexes lie in their non-covalent interactions with DNA and/or specific enzymes. To elucidate the minimal DNA binding affinity required for meaningful anticancer activity of non-covalent compounds, the significant DNA conformational changes induced by their non-covalent association are to be investigated using NMR and UV, CD spectroscopy. To examine other possible targets besides DNA, a specific enzyme-inhibition assay is performed on selected probable target molecules such as protein kinase and topoisomerase. Correlations between their biological activities and non-covalent DNA binding properties are to be discussed comprehensively.
    A preliminary crystallographic experiment on small fragments of double-stranded DNA co-crystallized with each of the selected Pt(II) complexes is studied at GA Tech. The purpose for this study is to unambiguously find out their specific DNA-binding positions of the selected cationic Pt(II) complexes and the resulting DNA conformations. A part of the results obtained from the above-mentioned studies bring us considerable information on biological activities and biochemical functions against bio-molecules such as specific DNA binding modes and significant structural changes. Osaka Univ Pharma Sci confirmed the same structure in both solid and solution by NMR spectroscopy. Accordingly, we will be able to elucidate the decisive factors needed to trigger cell death and acquire a novel interpretation of anticancer mechanisms.
  8. Any Comments
    AO hope closer connection between JSPS and NCI. It is desirable that JSPS get the information in NCI side because it looks the top of NCI decides the financial support. As he looks very busy, it is not easy to catch him. Though there was such a difficulty, we become to feel that we have a nice collaboration though this project because we get some DNA-Pt adduct crystal structures which were not expected before. AO would like to appreciate the support by JSPS and NCI.