Carbonyl Reductase 1 Is a Predominant Doxorubicin Reductase in the Human Liver

Abstract

ABSTRACT:A first step in the enzymatic disposition of the antineoplastic drug doxorubicin (DOX) is the reduction to doxorubicinol (DOX-OL). Because DOX-OL is less antineoplastic but more cardiotoxic than the parent compound, the individual rate of this reaction may affect the antitumor effect and the risk of DOX-induced heart failure. Using purified enzymes and human tissues we determined enzymes generating DOX-OL and interindividual differences in their activities. Human tissues express at least two DOX-reducing enzymes. High-clearance organs (kidney, liver, and the gastrointestinal tract) express an enzyme with an apparent K m of ϳ140 M. Of six enzymes found to reduce DOX, K m values in this range are exhibited by carbonyl reductase 1 (CBR1) and aldo-keto reductase (AKR) 1C3. CBR1 is expressed in these three organs at higher levels than AKR1C3, whereas AKR1C3 has higher catalytic efficiency. However, inhibition constants for DOX reduction with 4-amino-1-tert-butyl-3-(2-hydroxyphenyl)pyrazolo[3,4-d]pyrimidine(an inhibitor that can discriminate between CBR1 and AKR1C3) were identical for CBR1 and human liver cytosol, but not for AKR1C3. These results suggest that CBR1 is a predominant hepatic DOX reductase. In cytosols from 80 human livers, the expression level of CBR1 and the activity of DOX reduction varied >70-and 22-fold, respectively, but showed no association with CBR1 gene variants found in these samples. Instead, the interindividual differences in CBR1 expression and activity may be mediated by environmental factors acting via recently identified xenobiotic response elements in the CBR1 promoter. The variability in the CBR1 expression may affect outcomes of therapies with DOX, as well as with other CBR1 substrates.

Effect of selected catechins on doxorubicin antiproliferative efficacy and hepatotoxicity in vitro

“…4). Protective effect of EGCG may depend on its ability to inhibit carbonyl reductase 1, the enzyme responsible for the formation of a more toxic DOX metabolite (21), and also on EGCG antioxidant and antiradical properties.…”

“…In rat, individual catechins and/or green tea extract exhibited protective effects against DOX-induced cardiovascular abnormalities (16), cardiomyocyte injury (17, 18), brain toxicity (19), and spermatogenic disorders (20). Moreover, catechins are able to inhibit carbonyl reductase 1, the main DOX deactivation enzyme (21), and in this way they enhanced DOX efficacy in tumor-bearing mice (22). On the other hand, antioxidant properties of catechins could decrease DOX--mediated oxidative stress in cancer cells, which is believed to contribute to DOX antiproliferative effect (8,12).…”

Up-Regulation of Carbonyl Reductase 1 Renders Development of Doxorubicin Resistance in Human Gastrointestinal Cancers

“…CBR1 exhibits reductase activity toward DOX and is considered to be the predominant DOX reductase in human liver, 49) whereas its K m value for DOX (167 49) or 540 µM 38) ) is substantially higher than the blood concentration (0.1 to 1 µM) detected in patients who received the chemotherapy. 53) Under our assay conditions using DOX at the low concentration (10 µM), recombinant CBR1 (less than 100 µg) and the overexpression into LoVo cells hardly reduced DOX into its C-13 alcohol metabolite DOXol.…”

“…Although the detailed mechanisms underlying the low responsiveness of the anticancer drugs in the cancers are ambiguous, one of the most convincing reasons might be high expressions of metabolic enzymes that conjugate and detoxify the drugs. Although CBR1 is ubiquitously distributed in normal human organs and its high expression is detected in the liver, kidney and gastrointestinal tract, 49) clinical investigation using tumor specimens indeed revealed overexpression of CBR1 in the hepatocellular carcinoma cells and colon cancer tissues. 16) In this study, we demonstrate that CBR1 is a diagnostic and prognostic biomarker for developing DOX resistance of gastrointestinal cancers.…”

“…6A), the major metabolic enzyme is not identified yet. Since three AKRs (1C1, 1C3 and 1B10) are reported to be also Nrf2-driven genes 56,57) and to reduce the anthracycline drugs into their corresponding alcohols, 38,49) further studies in our laboratory are underway to define pathophysiological roles of the four AKRs in development of the chemoresistant gastrointestinal cancer cells.…”