Biophysical analysis of natural, double-helical DNA modified by anticancer heterocyclic complexes of ruthenium(III) in cell-free media

Abstract

Modifications of natural DNA by three anticancer heterocyclic ruthenium(III) compounds were studied by methods of molecular biophysics. These methods included DNA binding studies using atomic absorption spectrophotometry, inhibition of restriction endonucleases, mapping of DNA adducts by transcription assay, interstrand cross-linking employing gel electrophoresis under denaturing conditions, DNA unwinding studied by gel electrophoresis, circular dichroism analysis of the B-->Z transition in DNA, and DNA melting curves measured by absorption spectrophotometry. The results indicate that the complexes HIm[trans-Cl4Im2RuIII], HInd[trans-Cl4Ind2RuIII], and Na[trans-Cl4Im(Me2SO)RuIII] (Im and Ind stand for imidazole and indazole, respectively) coordinate irreversibly to DNA. Their DNA binding mode is, however, different from that of cisplatin. Interestingly, Na[trans-Cl4Im(Me2SO)RuIII] binds to DNA considerably faster than the other two ruthenium compounds and cisplatin. In addition, when Na[trans-Cl4Im(Me2SO)RuIII] binds to DNA it exhibits an enhanced base sequence specificity in comparison with the other two ruthenium complexes. Na[trans-Cl4Im(Me2SO)RuIII] also forms bifunctional intrastrand adducts on double-helical DNA which are capable of terminating RNA synthesis in vitro, while the capability of the other two ruthenium compounds to form such adducts is markedly lower. This observation has been interpreted to mean that the bifunctional adducts of HInd[trans-Cl4Ind2RuIII] and Na[trans-Cl4Im2RuIII] formed on rigid double-helical DNA are sterically more crowded by their octahedral geometry than those of Na[trans-Cl4Im(Me2SO)RuIII]. In addition, the adducts of all three ruthenium compounds affect the conformation of DNA, Na[trans-Cl4Im(Me2SO)RuIII] being most effective. It has been suggested that the altered DNA binding mode of ruthenium compounds in comparison with cisplatin might be an important factor responsible for the altered cytostatic activity of this class of ruthenium compounds in tumor cells.

Antiangiogenic properties of selected ruthenium(III) complexes that are nitric oxide scavengers

“…In conclusion, this study demonstrates that ruthenium(III) compounds inhibit NO-dependent angiogenesis, and highlights a rather innovative mechanism of action for heavy metal-based compounds, which are currently hypothesised to act via DNAbinding (Malina et al, 2001). The antimetastatic activity of these metallodrugs might be multiple, interfering with the endothelial cell functions during angiogenesis, angiogenic factor overexpression, the vasodilating state of tumours and probably tumour cell invasiveness, each event being demonstrated by different groups as NO-dependent (Fukumura et al, 1997;Gallo et al, 1998;Jadeski and Lala, 1999;Orucevic et al, 1999;Jadeski et al, 2000;Morbidelli et al, 2001;Feng et al, 2002).…”

KP1019, A New Redox‐Active Anticancer Agent – Preclinical Development and Results of a Clinical Phase I Study in Tumor Patients

“…1% of total DNA adducts, ca. six times less than cisplatin) was found in cell-free assays [84], and the unwinding of negatively supercoiled plasmid DNA was less pronounced (ca. 78 vs. 138 per adduct).…”

“…78 vs. 138 per adduct). The DNA adducts of KP1019 displayed only a low capacity of terminating transcription [84].…”

Cytotoxicity of cyclometallated ruthenium complexes: the role of ligand exchange on the activity

“…Such activation can be used to increase the specificity towards tumours, because only the affected areas are irradiated selectively, thus decreasing the adverse side effects observed with thermally activated drugs, such as cisplatin [15][16][17][18][19]. It should be noted that related complexes have been shown to reach the cellular nucleus and, upon irradiation with visible light, to cross-link the nuclear proteins p53 and PCNA, as well as to form protein-DNA adducts, and to inhibit DNA replication [21]; moreover, other ruthenium complexes are undergoing clinical trials [22][23][24][25][26][27][28][29][30][31][32].…”