title: Glutathione-S-transferase activates novel alkylating agents.
abstract: Alkylating agents which are activated by glutathion-S-transferases (GSTs) have been designed and synthesized. The model compound gamma-glutamyl-alpha-amino-beta-[(2-ethyl N,N,N',N'-tetraethylphosphorodiamidate) sulfonyl]propionylglycine (1) and the nitrogen mustards gamma-glutamyl-alpha- amino-beta-[[2-ethyl N,N,N',N'-tetrakis (2-chloroethyl)phosphorodiamidate] sulfonyl]propionylglycine (2) and gamma-glutamyl-alpha-amino-beta-[[2-ethyl-N,N,N',N'-tetrakis(2- chloroethyl)phosphorodiamidate]sulfonyl]-propionyl-(R)-(-)-phenylg lycine (3) were prepared via multistep chemical synthesis. The compounds were tested with recombinant human A1-1, M1a-1a and P1-1 GSTs. HPLC studies showed that the compounds were differentially and catalytically cleaved by biologically relevant concentrations of the GSTs. Mass spectral studies of the cleavage mixture of 2 showed that M1a-1a GST liberated the cytotoxic phosphate moiety needed for efficacy as an alkylating agent. Cell culture studies with MCF-7 breast cancer cells showed that 1 was not toxic at 200 microM, while 2 and 3 showed IC50S of 40.6 and 37.5 microM, respectively, for the same cell line. MCF-7 cells transfected to overexpress P1-1 GST showed enhanced sensitivity with 2 and 3, with IC50S of 20.9 and 9.5 microM, respectively. This result correlates well with the rates of cleavage of 2 and 3 by P1-1 GST observed in vitro and demonstrates that higher levels of cellular P1-1 GST will give increased sensitivity to these drugs.
authors.affiliation: Terrapin Technologies, South San Francisco, California 94080.
authors.forename: M H
authors.initials: MH
authors.lastname: Lyttle
authors.forename: A
authors.initials: A
authors.lastname: Satyam
authors.forename: M D
authors.initials: MD
authors.lastname: Hocker
authors.forename: K E
authors.initials: KE
authors.lastname: Bauer
authors.forename: C G
authors.initials: CG
authors.lastname: Caldwell
authors.forename: H C
authors.initials: HC
authors.lastname: Hui
authors.forename: A S
authors.initials: AS
authors.lastname: Morgan
authors.forename: A
authors.initials: A
authors.lastname: Mergia
authors.forename: L M
authors.initials: LM
authors.lastname: Kauvar
mesh_terms: D000477:Alkylating Agents / Q000378:metabolism* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000378:metabolism* / Q000494:pharmacology; D001711:Biotransformation; D002384:Catalysis; D005982:Glutathione Transferase / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D013058:Mass Spectrometry; D014407:Tumor Cells, Cultured
chemical_list: D000477:Alkylating Agents; D000970:Antineoplastic Agents; D007527:Isoenzymes; D005982:Glutathione Transferase