Carbonyl reduction of the potential cytostatic drugs benfluron and 3,9-dimethoxybenfluron in human in vitro.
Benfluron (B, [5-(2-N-oxo-2-N',N"-dimethylaminoethoxy)-7-oxo-7H-benzo[c]fluorene]) is a potential benzo[c]fluorene antineoplastic agent with high activity against a broad spectrum of experimental tumors in vitro and in vivo. The structure of B has been modified to repress its rapid deactivation through carbonyl reduction on C7. 3,9-Dimethoxybenfluron (D, [3,9-dimethoxy-5-(2-N-oxo-2-N',N"-dimethylaminoethoxy)-7-oxo-7H-benzo[c]fluorene]) is one of the B derivatives developed. The present paper was designed to compare the C7 carbonyl reduction of B and D in microsomes, cytosol and hepatocytes from human liver. Two purified human enzymes, microsomal 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD 1) and cytosolic carbonyl reductase, were tested if they are responsible for B and D carbonyl reduction in the respective fractions. Indeed, carbonyl reduction of D in comparison to that of B was 4 and 6-10 times less extensive in human liver microsomes and cytosol, respectively. Moreover, about 10-20 times higher amounts of dihydro B than dihydro D were detected in primary culture of human hepatocytes. 11beta-HSD 1 was shown to be able to reduce B and D. For this enzyme, about 10 times higher rates of carbonyl reduction were observed for B than for D. Likewise, CR participates in B and D carbonyl reduction, although smaller amounts of both reduced metabolites were detected. In summary, carbonyl reduction of D was significantly less extensive than that of B in all in vitro experiments. This lower rate of D inactivation was especially pronounced in hepatocytes which represent a close to in vivo situation. Our results clearly demonstrate that dimethoxy substitution protects the carbonyl group of the benzo[c]fluorene moiety against the deactivation by microsomal and cytosolic reductases. Detailed knowledge on the participating enzymes may serve as a basis for the co-application of specific inhibitors in chemotherapy to further improve the pharmacokinetics of benzo[c]fluorene derivatives.
Department of Biochemical Sciences, Faculty of Pharmacy, Charles University, Research Centre LN00B12, Heyrovského 1203, CZ-500 05 Hradec Králové, Czech Republic.
Lenka
L
Skálová
Milan
M
Nobilis
Barbora
B
Szotáková
Eliska
E
Kondrová
Michal
M
Savlík
Vladimír
V
Wsól
Lydiane
L
Pichard-Garcia
Edmund
E
Maser
D042842:11-beta-Hydroxysteroid Dehydrogenases; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D005449:Fluorenes / Q000737:chemistry / Q000378:metabolism*; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions
C405005:3,9-dimethoxybenfluron; D000970:Antineoplastic Agents; D005449:Fluorenes; C034234:VUFB 13468; D000429:Alcohol Oxidoreductases; D006913:Hydroxysteroid Dehydrogenases; D042842:11-beta-Hydroxysteroid Dehydrogenases