Mechanism of action of non-cisplatin type DNA-targeted platinum anticancer agents: DNA interactions of novel acridinylthioureas and their platinum conjugates.
The DNA binding of two novel acridinylthioureas, ACR-NH-(CH(2))(2)-C(S)-NHCH(3) (1) and ACR-N(CH(3))-C(S)-NHCH(3) (3), and their platinum conjugates 4 and 5-derived from [PtCl(2)(en)]-was studied in cell-free model systems using various physico-chemical and biophysical methods. These included: spectrophotometric drug-DNA titrations, ethidium-DNA fluorescence quenching, competitive drug displacement, high-resolution NMR spectroscopy, and unwinding of plasmid DNA monitored by agarose gel electrophoresis. The acridinium cation of 1 showed strong binding to native DNA with K(i)=1.5 x 10(6)M(-1) and an excluded site size (n) of 2bp (McGhee-von Hippel fits of absorbance data). Compound 3 showed no measurable association with DNA. Binding of 1 was an order of magnitude stronger than that of simple 9-methylaminoacridine (2). In alternating copolymers, 1 exhibited slight AT preference. In poly(dA-dT)(2), enhanced association was accompanied by an increased binding site (approximately 3bp), while parameters in poly(dG-dC)(2) were consistent with classical intercalation. Displacement of 1 by distamycin from calf thymus DNA was suggestive of non-intercalating thiourea in 1 being located in the minor groove of the duplex. 1H NMR data of d(GGAGCTCC)(2) modified with 1 indicated intercalative binding of planar acridine, based on upfield shifts of aromatic proton signals relative to those in unbound 1 (Deltadelta approximately equal to -0.5 to -1ppm). Finally, 4 and 5 were found to unwind negatively supercoiled pUC19 plasmid by 21 degrees and 7 degrees per adduct, respectively (electrophoretic gel mobility assays). The difference in DNA binding modes of 4 and 5 is discussed as the ultimate source of the distinctly different biological activities of the conjugates.
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109-7486, USA.
Hemanta
H
Baruah
Christopher L
CL
Rector
Susanne M
SM
Monnier
Ulrich
U
Bierbach
D000166:Acridines / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D002417:Cattle; D004247:DNA / Q000737:chemistry / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy; D009944:Organoplatinum Compounds / Q000737:chemistry / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence
C463059:1-(2-(acridin-9-ylamino)ethyl)-1,3-dimethylthiourea, platinum conjugate; C463060:1-acridin-9-yl-1,3-dimethylthiourea, platinum conjugate; D000166:Acridines; D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D004247:DNA