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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.

Original publication

DOI

10.1038/srep31973

Type

Journal article

Journal

Sci Rep

Publication Date

25/08/2016

Volume

6

Keywords

Animals, Apoptosis, BRCA1 Protein, Cattle, Cell Line, Cell Proliferation, Checkpoint Kinase 1, Coordination Complexes, DNA, DNA Damage, DNA Repair, DNA Replication, G1 Phase Cell Cycle Checkpoints, Gene Expression, HeLa Cells, Histones, Humans, Intercalating Agents, Phosphorylation, Quinolines, Quinuclidines, Radiation, Ionizing, Radiation-Sensitizing Agents, Ruthenium