Design, synthesis, and biological activity of hybrid compounds between uramustine and DNA minor groove binder distamycin A.
The design, synthesis, characterization, DNA binding properties, and cytotoxic activity of a novel series of hybrids, namely, a molecular combination of the natural antibiotic distamycin A and the antineoplastic agent uramustine, are reported, and the structure-activity relationships are discussed. This homologous series 29-34 consisted of the minor groove binder distamycin A joined to uramustine (uracil mustard) by suitable aliphatic carboxylic acid moieties containing a flexible polymethylene chain that is variable in length [(CH(2))(n)(), where n = 1-6). All the hybrid compounds in this series exhibit enhanced activity compared to both distamycin A and uramustine derivatives 22-27 used for conjugation, giving IC(50) values in the range 7.26-0.07 microM following a 1 h exposure of human leukemic K562 cells, with maximal activity shown when n = 6. The distance between the uramustine and distamycin frame is crucial for the cytotoxicity, with compounds having linker lengths of four to six being at least 20-fold more cytotoxic than linker lengths one to three. Taq polymerase stop experiments demonstrated selective covalent binding of uramustine-distamycin hybrids to A/T rich DNA sequences, which was again more efficient with compounds 32-34 with a longer linker length. Two consequences can be derived from our study: (a) the distamycin moiety directs binding to the minor groove of A/T rich DNA sequences and, consequently, is responsible for the alkylation regioselectivity found in footprinting studies; (b) the higher flexibility due to a longer linker between the distamycin and uracil moieties allows the formation of complexes with the mustard moiety situated more deeply in the minor groove and, hence, with better alkylating properties.
Baraldi
Pier Giovanni
PG
Dipartimento di Scienze Farmaceutiche, Università di Ferrara, 44100 Ferrara, Italy. pgb@ifeuniv.unife.it
Romagnoli
Romeo
R
Guadix
Antonio Entrena
AE
Pineda de las Infantas
Maria Josè
MJ
Gallo
Miguel Angel
MA
Espinosa
Antonio
A
Martinez
Alberto
A
Bingham
John P
JP
Hartley
John A
JA
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D004247:DNA / Q000737:chemistry*; D004214:Distamycins / Q000737:chemistry*; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured; D014499:Uracil Mustard / Q000737:chemistry*
D000900:Anti-Bacterial Agents; D000970:Antineoplastic Agents; D004214:Distamycins; C030000:stallimycin; D004247:DNA; D014499:Uracil Mustard