title: A ruthenium polypyridyl intercalator stalls DNA replication forks, radiosensitizes human cancer cells and is enhanced by Chk1 inhibition.
abstract: Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing.
authors: CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.
authors: Martin R
authors: MR
authors: Gill
authors: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Malaysia.
authors: Siti Norain
authors: SN
authors: Harun
authors: CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.
authors: Swagata
authors: S
authors: Halder
authors: CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.
authors: Ramon A
authors: RA
authors: Boghozian
authors: CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.
authors: Kristijan
authors: K
authors: Ramadan
authors: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Malaysia.
authors: Haslina
authors: H
authors: Ahmad
authors: CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK.
authors: Katherine A
authors: KA
authors: Vallis
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D000071877:Checkpoint Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D056831:Coordination Complexes / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D004247:DNA / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D007364:Intercalating Agents / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D010766:Phosphorylation / Q000187:drug effects; D011804:Quinolines / Q000633:toxicity; D011812:Quinuclidines / Q000633:toxicity; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; C518919:CHIR-124; D056831:Coordination Complexes; C468783:H2AX protein, human; D006657:Histones; D007364:Intercalating Agents; D011804:Quinolines; D011812:Quinuclidines; D011838:Radiation-Sensitizing Agents; D012428:Ruthenium; D004247:DNA; C427203:calf thymus DNA; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1