ORIGINAL ARTICLE
Wanida Chearwae Æ Chung-Pu Wu Æ H. -Y. Chu
T. Randall Lee Æ Suresh V. Ambudkar
Pornngarm Limtrakul
Curcuminoids purified from turmeric powder modulate the function
of human multidrug resistance protein 1 (ABCC1)
Received: 9 February 2005 / Accepted: 2 May 2005 / Published online: 14 July 2005
Ó Springer-Verlag 2005
Abstract Multidrug resistance is a major cause of che-
motherapy failure in cancer patients. One of the resis-
tance mechanisms is the overexpression of drug efflux
pumps such as P-glycoprotein and multidrug resistance
protein 1 (MRP1, (ABCC1)). In this study, curcumin
mixture and three major curcuminoids purified from
turmeric (curcumin I, II, and III) were tested for their
ability to modulate the function of MRP1 using HEK293
cells stably transfected with MRP1-pcDNA3.1 and
pcDNA3.1 vector alone. The IC
50
of curcuminoids in
these cell lines ranged from 14.5–39.3 lM. Upon treating
the cells with etoposide in the presence of 10 lM curc-
uminoids, the sensitivity of etoposide was increased by
several folds only in MRP1 expressing and not in
pcDNA3.1-HEK 293 cells. Western blot analysis showed
that the total cellular level of MRP1 protein level was not
affected by treatment with 10 lM curcuminoids for three
days. The modulatory effect of curcuminoids on MRP1
function was confirmed by the inhibition of efflux of two
fluorescent substrates, calcein-AM and fluo4-AM. Al-
though all the three curcuminoids increased the
accumulation of fluorescent substrates in a concentra-
tion-dependent manner, curcumin I was the most
effective inhibitor. In addition, curcuminoids did not
affect 8-azido[aÀ
32
P]ATP binding, however they did
stimulate the basal ATPase activity and inhibited the
quercetin-stimulated ATP hydrolysis of MRP1 indicat-
ing that these bioflavonoids interact most likely at the
substrate-binding site(s). In summary, these results
demonstrate that curcuminoids effectively inhibit MRP1-
mediated transport and among curcuminoids, curcumin
I, a major constituent of curcumin mixture, is the best
modulator.
Keywords Curcumin I Æ Curcumin II Æ Curcumin III Æ
Modulator Æ Multidrug resistance (MDR) Æ Multidrug
resistance related protein (MRP1)
Introduction
Drug resistance is a major impediment to the treatment
of cancer patients receiving single or multiple drugs.
Efforts to reverse drug resistance of tumor cells have
been largely unsuccessful [25]. In recent years, consid-
erable research has been directed toward understanding
the underlying mechanisms that confer drug resistance.
One of the major mechanisms of Multidrug resistance
(MDR) is the enhanced ability of tumor cells to ac-
tively efflux drugs leading to a decrease in cellular drug
accumulation below toxic levels [13]. Active drug efflux
is mediated by several members of the ATP-binding
cassette (ABC) superfamily. The first of ABC trans-
porter to be identified and characterized was the
170 kDa P-glycoprotein (P-gp) [1, 2] and then Multi-
drug Resistance Protein 1 (MRP1) was discovered in
1992 [10]. In contrast to P-gp, MRP1 is primarily an
active transporter of GSH, oxidized GSH, glucuronate
and sulfate conjugated organic anions [6, 11]. Many
chemicals are known to inhibit MRP1-mediated
transport, such as MK571, ONO-178 and glibencla-
mide, however mostly specific inhibitors are still under
development [9].
Turmeric belongs to the Zingiberaceae family and is
distributed throughout tropical and subtropical regions
around the world. It is widely used as a food flavoring
and coloring agent (e.g., in curry) as well as in tradi-
W. Chearwae Æ P. Limtrakul (&)
Department of Biochemistry, Faculty of Medicine,
Chiang Mai University, Chiang Mai, Thailand50200
E-mail: plimtrak@mail.med.cmu.ac.th
Tel.: +66-53-945323
Fax: +66-53-217144
C.-P. Wu Æ W. Chearwae Æ S. V. Ambudkar (&)
Laboratory of Cell Biology, Center for Cancer Research,
National Cancer Institute, NIH, DHHS, Bethesda, MD,
20892-4256 USA
E-mail: ambudkar@mail.nih.gov
Tel.: +1-301-4024178
Fax: +1-301-4358188
H. -Y. Chu Æ T. R. Lee
Department of Chemistry, University of Houston,
4800 Calhoun Road, Houston, TX, 77204-5003 USA
Cancer Chemother Pharmacol (2006) 57: 376–388
DOI 10.1007/s00280-005-0052-1