Roles of DNA Target in Cancer Cell-Selective Cytotoxicity by Dicopper Complexes with DNA Target/Ligand Conjugates

The DNA target/ligand conjugates (HLX, X =Pn and Mn, n =1-3)were synthesized where various lengths of -CONH(CH2CH2O)( n )CH2CH2NHCO- linkers with a 9-phenanthrenyl (P) or methyl(M) terminal as DNA targets replace the methyl group of 2,6-di(amide-tethercyclen)-p-cresol ligand (HL). DNA binding, DNA cleavage,cellular uptake, and cytotoxicity of [Cu-2(& mu;-OH)(L-X)](ClO4)(2) (1(X) ) are examined and compared with those of [Cu-2(& mu;-OH)(L)](ClO4)(2) (1) to clarify roles of DNA targets.Upon reaction of 1(X) with H2O2, & mu;-1,1-O2H complexes are formed for DNAcleavage. 1(P1) , 1(P2) , and 1(P3) are 22-, 11-, 3-fold more activefor conversion of Form II to III in the cleavage of supercoiled plasmidDNA with H2O2 than 1, where theshort P-linker may fix a dicopper moiety within a small number ofbase pairs to facilitate DNA double-strand breaks (dsb). This enhancesthe proapoptotic activity of 1(P1) , 1(P2) , and 1(P3) , which are 30-,12-, and 9.9-fold cytotoxic against HeLa cells than 1. DNA dsb and cytotoxicity are 44% correlated in 1(P1-3) but 5% in 1(M1-3) , suggestingspecific DNA binding of P-linkers and nonspecific binding of M-linkersin biological cells. 1(P1-3) exert cancercell-selective cytotoxicity against lung and pancreas cancer and normalcells where the short P-linker enhances the selectivity, but 1(M1-3) do not. Intracellular visualization,apoptosis assay, and caspase activity assay clarify mitochondrialapoptosis caused by 1(P1-3) . The highestcancer cell selectivity of 1(P1) may be enabledby the short P-linker promoting dsb of mitochondrial DNA with H2O2 increased by mitochondrial dysfunction in cancercells.

Automated summary

The DNA target/ligand conjugates were synthesized with various lengths of linkers and examined for DNA binding, DNA cleavage, cellular uptake, and cytotoxicity. Short P-linkers were found to enhance the activity and cytotoxicity of the conjugates against cancer cells. Moreover, the conjugates with P-linkers showed specific DNA binding and selectivity towards cancer cells, while those with M-linkers exhibited non-specific binding. Overall, the conjugates with short P-linkers exhibited promising potential for cancer treatment.