1. Role
of
Casein
Kinase
2
Inhibi1on
in
Estrogen
Receptor
Posi1ve
Breast
Cancer
Thu Nguyen1, Marlon Williams1, Jamal Pratt1, Patrick Carriere1, Shawn Llopis1, Syreeta L. Tilghman1, Christopher Williams1
Division of Basic Pharmaceutical Sciences, College of Pharmacy1, Xavier University of Louisiana, New Orleans, LA 70125
Hypothesis
Methodology
Protein kinase CK2 is involved in ER-dependent cell cycle progression of breast cancer
cell proliferation.
Abstract
Background: De novo or acquired resistance to anti-estrogens in estrogen receptor (ER)+
breast cancer has been attributed to ligand independent activation of the ER. Cross-talk with
kinase signaling pathways may mediate ligand-independent activation of the ER, resulting in
tumor progression despite anti-estrogen therapy. Protein kinase CK2, a ubiquitously expressed
serine threonine kinase, has been shown to impact the transcriptional activity of nuclear
receptors. In this study, we sought to ascertain the impact of CK2 inhibition on gene expression
and impact of CK2 inhibition on ER dependent breast cancer cell proliferation.
Methods: In order to ascertain the impact of CK2 on estrogen dependent gene expression,
T47D breast cancer cells were cultured in the presence of tetrabromocinnamic acid (TBCA), a
selective inhibitor of CK2, and ERE-driven luciferase activity and estrogen responsive gene
expression (PR, cMYC, CCND1). Following exposure to TBCA in the presence or absence of
estradiol, cell cycle progression and stress-associated cellular senescence were assayed by
flow cytometry.
Results: TBCA treatment resulted in decreased estradiol-induced ERE-luciferase activity.
Interestingly, TBCA had gene specific effects on estrogen responsive genes, potentiating
estradiol induced activation of cMYC and PGR, while inhibiting induction of CCND1 expression.
Conclusions: These studies show, for the first time, that CK2 modulates ER transcriptional
activity in a gene specific manner, and that CK2 is involved in ER-dependent cell cycle
progression by supporting estrogen induced CCND1 expression. These studies suggest a role
for CK2 as nuclear receptor co-activator, and that CK2 inhibition may be a viable adjunct to
anti-estrogen therapy in the treatment of breast cancer.
Discussion Acknowledgments
Research Centers for Minority Institutions (RCMI)
Louisiana Cancer Research Consortium
Xavier University of Louisiana RCMI Grant 3G12MD007595-04
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
DMSO
800nM
CK2
Inh
400nM
CK2
Inh
200nM
CK2
Inh
1nM
E2
100nM
Tamoxifen
100nM
Tam
+
400nM
CK2
Inh
1nM
E2
+
400nM
CK2
Inh
%
Control
(DMSO)
Treatments
CK2
Inhibi:on
Decreases
ERE
Transcrip:onal
Ac:vity
Results
Figure 3. ERE-driven Luciferase activity of T47D breast cancer cells
T47D breast cancer cells were treated with varying concentrations of a selective CK2 inhibitor (TBCA), alone
or in combination with Tamoxifen or estradiol (E2) and the resultant activity is shown as percent control of
activity. Cells treated with TBCA showed a decrease in estradiol-induced ERE-luciferase activity.
0
1
2
3
4
5
6
7
8
Con
E2
Fold
Expression
PGR
(-­‐TCBA)
(+TBCA)
0
5
10
15
20
25
30
Con
E2
Fold
Expression
CMYC
(-­‐TCBA)
(+TBCA)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Con
E2
Fold
Expression
CCND1
(-­‐TCBA)
(+TBCA)
Figure 4. Gene expression of TBCA-treated T47D breast
cancer cells
Estrogen responsive genes were analyzed in cells treated with
CK2 inhibitor, TBCA. (Top panel) Cells treated with TBCA showed
an increase in progesterone receptor (PCR) independent of
estradiol. (Middle panel) Oncogene CMYC, which is typically
known as a cell cycle promoter, shows increased expression with
TBCA, agreeing with its paradoxical function as a cell cycle arrest
promoter. (Bottom panel) TBCA reduces the expression of
cyclin- D1 (CCND1).
Figure 1. Luciferase Assay Protocol to measure ERE-activity
Figure
2.
Chemical
Structure
of
CK2
inhibitor
TBCA
(E)-­‐3-­‐(2,3,4,5-­‐tetrabromophenyl)acrylic
acid
• CK2 modulates ER transcriptional activity in a gene specific
manner
• CK2 is involved in ER-dependent cell cycle progression
• CK2 has a possible role as a nuclear receptor co-activator