abstract
Highlights
- •GR
activation promotes cell survival in GR-positive high-grade serous
ovarian carcinoma (HGS-OvCa) cell lines treated with chemotherapy.
- •GR antagonism increases chemotherapy-induced cell death in a GR-positive HGS-OvCa xenograft model.
- •GR is expressed in the majority of primary HGS-OvCas examined.
Objectives
To
test the
hypothesis that glucocorticoid receptor (GR) activation
increases resistance to chemotherapy in
high-grade serous ovarian cancer
(HGS-OvCa) and that treatment with a
GR antagonist will improve
sensitivity to chemotherapy.
Methods
GR
expression was assessed in OvCa cell lines by qRT-PCR and Western blot
analysis and in xenografts and primary human tumors using
immunohistochemistry (IHC). We also examined the effect of GR activation
versus inhibition on chemotherapy-induced cytotoxicity in OvCa cell
lines and in a xenograft model.
Results
With
the exception of IGROV-1 cells, all OvCa cell lines tested had
detectable GR expression by Western blot and qRT-PCR analysis.
Twenty-five out of the 27 human primary HGS-OvCas examined expressed GR
by IHC. No cell line expressed detectable progesterone receptor (PR) or
androgen receptor (AR) by Western blot analysis.
In vitro assays showed that in GR-positive HeyA8 and SKOV3 cells, dexamethasone (100 nM) treatment upregulated the pro-survival genes
SGK1 and
MKP1/DUSP1
and inhibited carboplatin/gemcitabine-induced cell death. Concurrent
treatment with two GR antagonists,
either mifepristone (100 nM) or
CORT125134 (100 nM), partially reversed these effects. There was no
anti-apoptotic effect of
dexamethasone on chemotherapy-induced cell
death in IGROV-1 cells, which did not have detectable GR protein.
Mifepristone treatment alone was not cytotoxic in any cell line. HeyA8
OvCa
xenograft studies demonstrated that adding mifepristone to
carboplatin/gemcitabine increased tumor shrinkage by 48% compared to
carboplatin/gemcitabine treatment alone (P = 0.0004).
Conclusions
These results suggest that GR antagonism sensitizes GR
+ OvCa to chemotherapy-induced cell death through inhibition of GR-mediated cell survival pathways
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