RT Journal Article SR Electronic T1 Naturally occurring variants of human aldo-keto reductases with reduced in vitro metabolism of daunorubicin and doxorubicin JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP jpet.110.173179 DO 10.1124/jpet.110.173179 A1 Onkar S Bains A1 Thomas A Grigliatti A1 Ronald E Reid A1 K. Wayne Riggs YR 2010 UL http://jpet.aspetjournals.org/content/early/2010/09/13/jpet.110.173179.abstract AB Doxorubicin (DOX) and daunorubicin (DAUN) are effective anti-cancer drugs; however, considerable inter-patient variability exists in their pharmacokinetics. This may be due to altered metabolism by non-synonymous single nucleotide polymorphisms (ns-SNPs) in genes encoding aldo-keto reductases (AKRs) and carbonyl reductases (CBRs). This study examined the effect of 27 ns-SNPs, in 8 human genes, on the in vitro metabolism of both drugs to their major metabolites, doxorubicinol (DOXol) and daunorubicinol (DAUNol). Kinetic assays measured metabolite levels by HPLC separation with fluorescence detection using purified, histidine-tagged, human wild-type and variant enzymes. Maximal rate of activity (Vmax), substrate affinity (Km), turnover rate (kcat), and catalytic efficiency (kcat/Km) were determined. Using DAUN as substrate, variants for 3 genes exhibited significant differences in these parameters compared to their wild-type counterparts: the A106T, R170C, and P180S variants significantly reduced metabolism compared to the AKR1C3 wild-type (Vmax: 23-47% decrease; kcat: 22-47%, kcat/Km: 38-44%); the L311V variant of AKR1C4 significantly decreased Vmax (47% lower), as well as kcat and kcat/Km (both 43% lower); and the A142T variant of AKR7A2 significantly affected all kinetic parameters (Vmax and kcat: 61% decrease; Km: 156% increase; kcat/Km: 85% decrease). With DOX, the R170C and P180S variants of AKR1C3 showed significantly reduced Vmax (41-44% decrease), kcat (39-45%), and kcat/Km (52-69%), while the A142T variant significantly altered all kinetic parameters for AKR7A2 (Vmax: 41% decrease; kcat: 44% decrease; Km: 47% increase; kcat/Km: 60% decrease). These findings suggest that ns-SNPs in human AKR1C3, AKR1C4, and AKR7A2 significantly decrease the in vitro metabolism of DOX and DAUN.