INHIBITION OF CYTARABINE-INDUCED MDR1 (P-GLYCOPROTEIN) GENE ACTIVATION IN HUMAN TUMOR-CELLS BY FATTY-ACID POLYETHYLENE-GLYCOL FATTY-ACID DIESTERS, NOVEL INHIBITORS OF P-GLYCOPROTEIN FUNCTION
Pg. Komarov et al., INHIBITION OF CYTARABINE-INDUCED MDR1 (P-GLYCOPROTEIN) GENE ACTIVATION IN HUMAN TUMOR-CELLS BY FATTY-ACID POLYETHYLENE-GLYCOL FATTY-ACID DIESTERS, NOVEL INHIBITORS OF P-GLYCOPROTEIN FUNCTION, International journal of cancer, 68(2), 1996, pp. 245-250
Fatty acid ester surfactants Cremophor EL and Solutol HS 15 were descr
ibed earlier as modulators of multidrug resistance mediated by MDR1 P-
glycoprotein (Pgp). We have shown that the most active components of t
hese polydisperse surfactants are fatty acid-polyethylene glycol-fatty
acid diesters (FA-PEG-FA). A new generation of Pgp-surfactant inhibit
ors of defined structure was therefore synthesized. In the present stu
dy we show that these compounds are also able to inhibit upregulation
of MDR1 gene expression caused by cytarabine (ARA-C) and doxorubicin i
n human tumor cell lines H9 and KB 3-1, which express minimal levels o
f MDR1 mRNA. The surfactant inhibitors, however, had no effect on the
induction of MDR1 gene expression by protein kinase C agonists. Using
a set of FA-PEG-FA diesters with various fatty acids and different len
gths of the PEG domain, we demonstrated that the activity of diester p
reparations as inhibitors of drug-induced MDR1 activation was in propo
rtion to their activity as inhibitors of Pgp function. Oleic and stear
ic acid diesters with PEG 900 (20 ethylene oxide units) were the most
potent. The poloxamer analogs of these diesters demonstrated similar e
ffects. In contrast, the well-known, structurally unrelated inhibitors
of Pgp activity, verapamil, cyclosporin A and PSC 833, had no inhibit
ory effect on drug-induced MDR1 activation. The ability of FA-PEG-FA d
iesters to inhibit both Pgp function and drug-induced MDR1 activation
suggests that these chemomodulators may be uniquely useful for the pro
phylaxis of Pgp-mediated multidrug resistance in drug-treated tumors.
(C) 1996 Wiley-Liss, Inc.