Induction of the oxidative catabolism of retinoid acid in MCF-7 cells.
Cytochrome P450-dependent oxidation is a pathway for all-trans-retinoic acid (all-trans-RA) catabolism. Induction of this catabolic pathway was studied in MCF-7 breast cancer cells. MCF-7 cells showed low constitutive all-trans-RA catabolism. Concentration-dependent induction was obtained by preincubation of the cells with all-trans-RA (10(-9) to 10(-6) M). Onset of induction was fast, being detectable within 60 min, with maximal induction (45-fold) obtained after 16 h. Enzymatic characterization of induced all-trans-RA catabolism showed an estimated Km value (Michaelis-Menten constant) of 0.33 microM and a Vmax value (maximal velocity of an enzyme-catalysed reaction) of 54.5 fmol polar all-trans-RA metabolites 10(6) cells(-1) h(-1). These kinetic parameters represent the overall formation of polar metabolites from all-trans-RA. Induction of all-trans-RA catabolism was also obtained with other retinoids, CH55 >> 13-cis-RA = all-trans-RA > 9-cis-RA > 4-keto-all-trans-RA > 4-keto-13-cis-RA > retinol. The potency of the retinoids to induce all-trans-RA catabolism was correlated to their retinoic acid receptor affinity (Crettaz et al, 1990; Repa et al, 1990; Sani et al, 1990). Induction of all-trans-RA catabolism was inhibited by actinomycin D. Furthermore, all-trans-RA did not increase cytosolic retinoic acid-binding protein (CRABP) mRNA levels. These data suggest that induction of all-trans-RA catabolism in MCF-7 cells is a retinoic acid receptor-mediated gene transcriptional event. Induced all-trans-RA catabolism was inhibited by various retinoids with decreasing potency in the order: all-trans-RA > 4-keto-all-trans-RA > 13-cis-RA > 9-cis-RA > 4-keto-13-cis-RA > retinol > CH55. The antitumoral compound liarozole-fumarate inhibited all-trans-RA catabolism with a potency similar to that of all-trans-RA.
Krekels
M D
MD
Janssen Research Foundation, Department of Oncology, Beerse, Belgium.
Verhoeven
A
A
van Dun
J
J
Cools
W
W
Van Hove
C
C
Dillen
L
L
Coene
M C
MC
Wouters
W
W
D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007641:Keratolytic Agents / Q000378:metabolism*; D010084:Oxidation-Reduction; D015203:Reproducibility of Results; D012176:Retinoids / Q000494:pharmacology*; D012177:Retinol-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D014212:Tretinoin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D018931:Antineoplastic Agents, Hormonal; D007093:Imidazoles; D007641:Keratolytic Agents; D012176:Retinoids; D012177:Retinol-Binding Proteins; D014212:Tretinoin; C061121:liarozole