MicroRNA Involvement in Breast Cancer Multidrug Resistance Zhongxing
MicroRNA Involvement in Breast Cancer
Zhongxing Liang1, Hui Wu1, James Xia2, Yuhua Li1, Nick Wagar1, Aizhi Zhu1, Sijia Wang1, Dean Blevins1, Younghyoun Yoon1,
Santosh Reddy1, Jeanine Southerland1, Stefania Scala3, Susan E. Bates4, Hyunsuk Shim1.
1. Emory Univ., Atlanta, GA; 2. GenoSensor Corp., Tempe, AZ; 3. National Cancer Institute, Naples, Italy; 4. NCI/NIH, Frederick, MD
Fig. 3. Expression levels of miR-326 and miR-29C in
different human breast cancer tissues and normal
breast tissue. N, normal breast tissue; P1, early
breast cancer tissue without metastasis; P2, advanced
breast cancer tissue with metastasis; and P3 metastatic
breast cancer tissue.
Fig. 4. Expression alteration of miR-326 in MCF-7 cells and miR-
MATERIALS AND METHODS
Cell Lines. MCF-7 and its multidrug resistant sublines: MCF-7/Adr200, which
was selected by adriamycin, and MCF-7/TX200, which was selected by
etoposide. MCF-7/MX100, which was selected by mitoxantrone, were used in
microRNA microArry Hybridization. The miRNAs , purified and labeled by
using the related kits from GenoSenor. Hybridizations, image scans, and data
analysis were performed by our microarray core facility. In brief, the
hybridized slides were subjected to scanning with ScanArray Express HT
scanner and to image analysis with GE software.
Data Analysis. For data analysis, we used GeneSpring software.
Hierarchical clustering was performed by Average Linkage.
Real-time PCR. Expression levels of a cluster of the decreased expressive
miRNAs and a cluster of the elevated expressive miRNAs were confirmed by
real time reverse transcription polymerase chain reaction.
siRNA Transfection. The selected decreased expressive miRNAs were
upregulated by transfection of synthetic RNA encoding the miRNAs, and
conversely, the selected elevated expressive miRNAs were downregulated
by transfection of synthetic siRNAs against the precursors of these miRNAs.
MTT Cell Proliferation Assay. Drug resistance was tested by increasing the
concentration of the tested drugs and measuring the surviving cells with the
MTT cell proliferation assay.
Western Blot Analyses. The proteins were resolved by SDS/PAGE and
subjected to immunoblot analysis with MDR-1, MRP-1 and BCRP.
Statistical Analysis. All quantitative data from MTT, and real-time RT-PCR
were repeated at least 3 times and statistically analyzed with a t-test.
0.42 1.4 1
IV. microRNAs are involved in multidrug resistance
II. Altered expression of microRNAs in
multidrug resistant cells
Fig. 1. Expression of MDR-related genes of MCF-7 and its MDR sublines.
MCF-7/Adr200, which was selected by adriamycin (doxorubicin), overexpresses
MDR-1 but not BCRP and MRP-1; MCF-7/MX100, which was selected by
mitoxantrone , overexpresses BCRP but not MDR-1 and MRP-1; MCF-1/TX200,
which was selected by etoposide, overexpresses MRP-1 but not MDR-1 and
Table 2. Altered expression of microRNAs in various type of MDR sublines
Multidrug resistance (MDR) has been frequently associated
with elevated expression of one or more ATP binding cassette
(ABC) transporters such as three well-known drug efflux
proteins: P-glycoprotein (MDR-1), multidrug resistance
associated protein (MRP-1), and breast cancer resistance protein
(BCRP). However, the regulation of these transporters remains
controversial. A recently discovered class of small, functional,
noncoding RNAs, named microRNAs (miRNAs), has been
shown to function as regulatory molecules by inhibiting protein
translation and to play an important role in development,
differentiation, cell proliferation, and apoptosis. Very little is
currently known about how changes in certain miRNA
expression levels among drug resistant tumor cells affect breast
cancer multidrug resistance.
In order to determine whether expression of certain
miRNAs is altered in various breast cancer MDR cell lines, we
performed analyses of miRNA expression in MDR cell lines
(MCF7/Adr200, MCF7/TX200, MCF7/MX100) compared to
their parent cell line (MCF7) using a microarray containing 463
human mature and precursor miRNA probes. Specific miRNA
expression profiles in MDR cells were observed. The alteration
of expression of 115 miRNAs were found at least in one MDR
subline, fifteen of which were differentially expressed in all
three MDR sublines compared to their parental cells. We found
that there are two different profiles of microRNAs between
MCF-7/adr200 overexpressed MDR-1 and MCF-7/TX200
overexpressed MRP-1 as well as MCF-7/MX100 overexpressed
BCRP and they may be regulated by different microRNAs. miR326 and miR-26C have demonstrated the involvement in
multidrug resistance. We will further modulate the levels of
more selected miRNAs in MDR cells or in MCF7 cells to
determine whether these altered expression of miRNAs is
involved in breast cancer MDR. Our findings will be beneficial
for the prediction of multidrug resistance in patients as well as
the design of personalized therapy for breast cancer patients.
I. Expression of MDR-related genes in multidrug
III. microRNAs as potentially specific modulators of MDR-related genes:MDR-1,
MRP-1 and BCRP
ABSTRACT and INTRODUCTION
Table 1. miRNAs with changed expression
in all three MDR sublines
Fig. 2. miRNAs with changed expression in multidrug resistant cells compared
to their parental cells. Panel A, the Venn diagram shows relationship of number
of miRNAs with very significant change of expression between three MDR
sublines. Fifty-four miRNAs are constitutively differentially expressed in all three
MDR sublines compared to their parental cells. Sixteen miRNAs are differentially
expressed only in MCF-7/Adr200 cells compared to its parental cell line MCF-7. Five
miRNAs & 7 miRNAs are differentially expressed respectively only in MCF-7/TX200 and
In MCF-7/MX100. Panel B, Dendrogram of clustering analysis of significant miRNA
expression in three MDR cell sublines and their parental cell line. The names of cell
lines are listed on the bottom of the figure. The dendrogram of clustering cell lines with
microRNA files is placed on the top of this figure. Colors represent normalized median
value of miRNA expression according to their color legend on the right side of the figure
the range of the normalized median value was designated from 0 to 6 depending on
their colors from green to red. The dendrogram on the left shows clustering analysis
of miRNA expression. Panel C, The graph shows the fold number of expressive
difference of fifteen miRNAs with very significant change in MDR cells compared
those in their parental cells. The y-axis shows a different fold number of the normalized
median intensity of microRNA expression between MDR cells and their parental cells
26C in MCF-7/TX200 cells modulated multidrug resistance of
tumor cells. Panel A, expression levels miR-326 gene was
downregulated in MCF-7 cells with miR-326 siRNA and expression
levels of miR-29C was deregulated with siRNA against miR-29C.
Panel B, Effect of downregulation of miR-326 in MCF-7 (on the right)
or miR-29C in MCF-7/TX200 (on the left ) on multidrug resistance.
Each point is an average of triplicate determinations. Effect of
miRNA siRNAs (closed symbols) on the drug sensitivity of cells
compared to control siRNA (open symbols).
CONCLUSION and PLANS
Specific profile of miRNAs and significant miRNAs with
altered expression in MDR cells were found. These findings will
contribute further study of mechanism of multidrug resistance in
cancer therapy. In addition, these findings will be beneficial for
the prediction of multidrug resistance in patients as well as the
design of personalized therapy for breast cancer Patients.
We will further modulate the levels of more selected miRNAs
in MDR cells or in MCF7 cells to determine whether these
altered expressions of miRNAs are involved in breast cancer
MDR. The targeting genes of significant miRNAs will be
searched by bioinformatics and microarray.
This study was supported by DOD Breast Cancer Program Concept
Award and a research grant from Georgian Cancer coalition (to ZL) as
well as a Distinguished Cancer Scientist Development
Award from Georgia cancer Coalition (to HS).
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