Cytotoxicity of the organic ruthenium anticancer drug Nami-A is correlated with DNA binding in four different human tumor cell lines.
OBJECTIVE
The cytotoxicity, intracellular accumulation and DNA adduct formation of the ruthenium complex imidazolium trans-imidazoledimethylsulfoxide tetrachlororuthenate (ImH[ trans-RuCl(4)(DMSO)Im], Nami-A) were compared in vitro with those of cisplatin in four human tumor cell lines: Igrov-1, 2008, MCF-7, and T47D.


METHODS
Cytotoxicity was assessed in vitro using a growth inhibition assay. Accumulation was determined by flameless atomic absorption spectroscopy (AAS). GG and AG intrastrand adducts were measured using the (32)P-postlabeling assay.


RESULTS
Nami-A was on average 1053 times less cytotoxic than cisplatin. The cytotoxicity of cisplatin was linearly related to both intracellular platinum accumulation and DNA binding, while the cytotoxicity of Nami-A was significantly related only to DNA binding and not to intracellular ruthenium accumulation. The levels of accumulation of Nami-A measured as ruthenium and of cisplatin measured as platinum were correlated linearly with the incubation concentration over a concentration range of 0 to 600 micro M of both drugs. Ruthenium intracellular accumulation and DNA binding were on average 4.8 and 42 times less, respectively, than those of cisplatin. In addition, the numbers of GG and AG intrastrand adducts induced by Nami-A were 418 and 51 times fewer, respectively. Nami-A and cisplatin had the same binding capacity to calf thymus DNA. Nami-A was 25-40% less bound to cellular proteins than cisplatin.


CONCLUSIONS
There was no saturation of the uptake and DNA binding capacity of either Nami-A or cisplatin. Furthermore, the low binding of Nami-A to cellular DNA cannot simply be explained by a lower capacity to bind to DNA, because the absolute level of binding in vitro to calf thymus DNA was the same for Nami-A and cisplatin. Finally, the lower cytotoxicity of Nami-A on a molar basis than that of cisplatin can at least partly be explained by its reduced reactivity to DNA in intact cells.
Pluim
Dick
D
Division of Experimental Therapy and Medical Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands.
van Waardenburg
Robert C A M
RC
Beijnen
Jos H
JH
Schellens
Jan H M
JH
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002417:Cattle; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D018736:DNA Adducts; D004121:Dimethyl Sulfoxide / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000633:toxicity*; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D009942:Organometallic Compounds / Q000494:pharmacology* / Q000633:toxicity*; D017975:Ruthenium Compounds; D013950:Thymus Gland
D000970:Antineoplastic Agents; D018736:DNA Adducts; D009942:Organometallic Compounds; D017975:Ruthenium Compounds; C113661:imidazolium-bis(imidazole)dimethylsulfoxideimidazotetrachlororuthenate(III); D002945:Cisplatin; D004121:Dimethyl Sulfoxide