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.

On the binding modes of metal NHC complexes with DNA secondary structures: implications for therapy and imaging

“…Recent proofof-principle studies on organometallic NHC anticancer agents showed that this class of compounds is able to target several canonical and non-canonical DNA secondary structures. In detail, metal NHC complexes were shown to interact with duplex, mismatched and Gquadruplex DNA, while examples of other classes of metal-based anticancer agents exist that inhibit replication forks, 89 by interacting with DNA three-way junctions, 90 spectroscopy and isotope-specific mass spectrometry would allow to follow not only the compounds distribution in cells, but also the structural integrity of the compound, e.g. with regard to ligand exchange reactions.…”

Recent developments in the nanostructured materials functionalized with ruthenium complexes for targeted drug delivery to tumors

“…Hence, the potential benefits and application of these complexes in combination therapy for cancer treatment warrants further investigation. 22 Recently, Koceva-Chyła et al evaluated the in vitro anticancer activity of dinuclear trithiolato-bridged arene ruthenium complex diruthenium-1 (DiRu-1) against a panel of human cancer cell lines including HepG2 (hepatocellular carcinoma), MCF-7 (estrogen-responsive breast adenocarcinoma), and MDA-MB-231 (triple-negative breast adenocarcinoma) cells. DiRu-1 was found to be extremely toxic to these cell lines, with half-maximal inhibitory concentration (IC 50 ) values in the low-nanomolar range.…”

Photo-induced cytotoxicity and anti-metastatic activity of ruthenium(ii)–polypyridyl complexes functionalized with tyrosine or tryptophan

“…11,10,53,54 Many researchers have suggested that effective therapy for cancer or efficient ways of treating a cancer patient essentially depends on the antimetastatic activity of the chemotherapeutic PS drugs. 3,10 from the MTT assay, it is evident that these two complexes have good potential for interrupting cancer cell proliferation in the presence of visible light.…”

“…8,9 The possibility of achieving high solubility by choosing appropriate counter anions or through appropriate functionalization of the coordinated ligands has led to the design of new Ru(II)-polypyridyl complexes for use of anti-cancer and antimetastatic drugs. 10,11 These complexes are attractive choices for use as photodynamic therapeutic reagents and they also possesses visible light excitation, reasonably long-lived triplet excited states, and higher stability towards photobleaching. 7 Recent reports suggested that the conjugation of biologically relevant molecules to the Ru(II)-polypyridyl complexes can improve cellular internalization.…”

“…3) For PDT application, relatively high quantum yield of 1 O 2 (~0.5) is desired. 10 We utilized the N,N-dimethyl-4-nitrosoaniline (RNO)/imidazole assay for evaluating the relative quantum yield efficiency for 1 O 2 generation by complexes 1 and 2 on irradiation with a visible light source having λ ≥ 450 nm (table 2, Fig. S4).…”