Progesterone photoaffinity labels P-glycoprotein in multidrug-resistant human leukemic lymphoblasts.

MDR (multidrug-resistance) represents a major obstacle to successful cancer chemotherapy and is usually accomplished by overexpression of P-gp (P-glycoprotein). Much effort has been devoted to developing P-gp inhibitors to modulate MDR. However, none of the inhibitors on the market have been successful. 1416 [1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxyphenylethylamino)propane hydrochloride (phenoprolamine hydrochloride)] is a new VER (verapamil) analogue with a higher IC50 for blocking calcium channel currents than VER. In the present paper, we examined the inhibition effect of 1416 on P-gp both in vitro and in vivo. 1416 significantly enhanced cytotoxicity of VBL (vinblastine) in P-gp-overexpressed human multidrug-resistant K562/ADM (adriamycin) and KBV cells, but had no such effect on the parent K562 and KB cells. The MDR-modulating function of 1416 was further confirmed by increasing intracellular Rh123 (rhodanmine123) content in MDR cells. Human K562/ADM xenograft-nude mice model verified that 1416 potentiates the antitumour activity of VBL in vivo. RT-PCR (reverse transcriptase-PCR) and FACS analysis demonstrated that the expression of MDR1/P-gp was not affected by 1416 treatment. All these observations suggest that 1416 could be a promising agent for overcoming MDR in cancer chemotherapy.

Download Full-text

Structural Analysis of the Mousemdr1a (P-Glycoprotein) Promoter Reveals the Basis for Differential Transcript Heterogeneity in Multidrug-Resistant J774.2 Cells:

Molecular and Cellular Biology ◽

10.1128/mcb.10.11.6101 ◽

1990 ◽

Vol 10 (11) ◽

pp. 6101-6101

Keyword(s):

Structural Analysis ◽

Multidrug Resistant ◽

P Glycoprotein

Download Full-text

Multidrug resistant P-glycoprotein positive L1210/VCR cells are also cross-resistant to cisplatin via a mechanism distinct from P-glycoprotein-mediated drug efflux activity

General Physiology and Biophysics ◽

10.4149/pb_2009_04_391 ◽

2009 ◽

Vol 28 (4) ◽

pp. 391-403 ◽

Cited By ~ 10

Author(s):

L. Gibalová ◽

J. Sedlák ◽

M. Labudová ◽

M. Barančík ◽

A. Reháková ◽

...

Keyword(s):

Multidrug Resistant ◽

Drug Efflux ◽

P Glycoprotein

Download Full-text

The Fluorescent Probe Bodipy-FL-Verapamil Is a Substrate for Both P-glycoprotein and Multidrug Resistance-related Protein (MRP)-1

Journal of Histochemistry & Cytochemistry ◽

10.1177/002215540205000514 ◽

2002 ◽

Vol 50 (5) ◽

pp. 731-734 ◽

Cited By ~ 22

Author(s):

Enrico Crivellato ◽

Luigi Candussio ◽

Anna M. Rosati ◽

Fiora Bartoli-Klugmann ◽

Franco Mallardi ◽

...

Keyword(s):

Multidrug Resistance ◽

Drug Transport ◽

Mrna Level ◽

Fluorescent Microscopy ◽

Flow Cytometric Analysis ◽

Cell Types ◽

Multidrug Resistant ◽

Related Protein ◽

P Glycoprotein ◽

Multidrug Resistance Related Protein

Several fluorescent probes have been used in functional studies to analyze drug transport in multidrug-resistant cells by fluorescent microscopy. Because many of these molecules have some drawbacks, such as toxicity, nonspecific background, or accumulation in mitochondria, new fluorescent compounds have been proposed as more useful tools. Among these substances, Bodipy-FL-Verapamil, a fluorescent conjugate of the drug efflux blocker verapamil, has been used to study P-glycoprotein activity in different cell types. In this study we tested by fluorescent microscopy the accumulation of Bodipy-FL- Verapamil in cell lines that overexpress either P-glycoprotein (P-gp) or multidrug resistance-related protein 1 (MRP1). Expression of P-gp and MRP1 was evaluated at the mRNA level by RT-PCR technique and at the protein level by flow cytometric analysis using C219 and MRP-m6 monoclonal antibodies. Results indicate that Bodipy-FL-Verapamil is actually a substrate for both proteins. As a consequence, any conclusion about P-gp activity obtained by the use of Bodipy-FL-Verapamil as fluorescent tracer should be interpreted with caution.

Download Full-text

A possible role for a mammalian facilitative hexose transporter in the development of resistance to drugs.

Molecular and Cellular Biology ◽

10.1128/mcb.11.7.3407 ◽

1991 ◽

Vol 11 (7) ◽

pp. 3407-3418 ◽

Cited By ~ 14

Author(s):

J C Vera ◽

G R Castillo ◽

O M Rosen

Keyword(s):

Xenopus Oocytes ◽

Glucose Transporter ◽

Cytochalasin B ◽

Chinese Hamster ◽

Multidrug Resistant ◽

Xenopus Laevis Oocytes ◽

Hexose Transporter ◽

P Glycoprotein ◽

Glut1 Protein ◽

Facilitative Glucose Transporter

We show that D- but not L-hexoses modulate the accumulation of radioactive vinblastine in injected Xenopus laevis oocytes expressing the murine Mdr1b P-glycoprotein. We also show that X. laevis oocytes injected with RNA encoding the rat erythroid/brain glucose transport protein (GLUT1) and expressing the corresponding functional transporter exhibit a lower accumulation of [3H]vinblastine and show a greater capacity to extrude the drug than do control oocytes not expressing the rat GLUT1 protein. Cytochalasin B and phloretin, two inhibitors of the mammalian facilitative glucose transporters, can overcome the reduced drug accumulation conferred by expression of the rat GLUT1 protein in Xenopus oocytes but have no significant effect on the accumulation of drug by Xenopus oocytes expressing the mouse Mdr1b P-glycoprotein. These drugs also increase the accumulation of [3H]vinblastine in multidrug-resistant Chinese hamster ovary cells. Cytochalasin E, an analog of cytochalasin B that does not affect the activity of the facilitative glucose transporter, has no effect on the accumulation of vinblastine by multidrug-resistant Chinese hamster cells or by oocytes expressing either the mouse Mdr1b P-glycoprotein or the GLUT1 protein. In all three cases, the drug verapamil produces a profound effect on the cellular accumulation of vinblastine. Interestingly, although immunological analysis indicated the presence of massive amounts of P-glycoprotein in the multidrug-resistant cells, immunological and functional studies revealed only a minor increase in the expression of a hexose transporter-like protein in resistant versus drug-sensitive cells. Taken together, these results suggest the participation of the mammalian facilitative glucose transporter in the development of drug resistance.

Download Full-text