title: Identification of human intestinal carboxylesterase as the primary enzyme for activation of a doxazolidine carbamate prodrug.
abstract: Doxazolidine (Doxaz), a formaldehyde-doxorubicin (Dox) conjugate, exhibits markedly increased tumor toxicity with respect to Dox without a concurrent increase in toxicity to cardiomyocytes. Pentyl PABC-Doxaz (PPD) is a Doxaz carbamate prodrug that is hydrolyzed by carboxylesterases. Here, we identify human intestinal carboxylesterase (hiCE) as the agent of activation for PPD. Upon prodrug treatment, cells that express higher levels of hiCE responded with lower IC50 values for growth inhibition. Exposing MCF-7 human breast cancer cells, which respond poorly and express little hiCE, to PPD together with hiCE resulted in a dramatic decrease in the IC50, a decrease that was absent when human carboxylesterase 1 was added to prodrug treatment. Finally, U373MG glioblastoma cells overexpressing hiCE displayed approximately 100-fold reduction in the IC50 for PPD compared to cells lacking the carboxylesterase. Overall, our studies indicate that PPD is selectively hydrolyzed to the active metabolite by hiCE.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Barthel
authors.forename: Renee C
authors.initials: RC
authors.lastname: Torres
authors.forename: Janice L
authors.initials: JL
authors.lastname: Hyatt
authors.forename: Carol C
authors.initials: CC
authors.lastname: Edwards
authors.forename: M Jason
authors.initials: MJ
authors.lastname: Hatfield
authors.forename: Philip M
authors.initials: PM
authors.lastname: Potter
authors.forename: Tad H
authors.initials: TH
authors.lastname: Koch
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism* / Q000494:pharmacology; D002219:Carbamates / Q000378:metabolism* / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007422:Intestines / Q000201:enzymology*; D011355:Prodrugs / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D002219:Carbamates; D011355:Prodrugs; D011994:Recombinant Proteins; C517056:pentyl 4-(N-doxazolidinylcarbonyloxymethyl)phenylcarbamate; D004317:Doxorubicin; D002265:Carboxylic Ester Hydrolases; C474609:CES1 protein, human