Induction of apoptosis and modulation of homologous recombination DNA repair pathway in prostate cancer cells by the combination of AZD2461 and valproic acid
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Date
2019-07-08
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Abstract
Cancer therapies using defects in homologous recombination (HR) DNA repair pathway of tumor cells are not yet
approved to be applicable in patients with malignancies other than BRCA1/2-mutated tumors. This study was
designed to determine the efficacy of
combination therapy of a histone deacetyl
ase inhibitor, valproic acid (VPA)
and a novel PARP inhibitor AZD2461 in both PC-3 (PTEN-mutated) and DU145 (PTEN-unmutated) prostate
cancer cell lines. The Trypan blue dye exclusion assay an
d the tetrazolium-based colorimetric (MTT) assay were
performed to measure the cytotoxicity while combination
effects were assessed based on Chou-Talalay's princi-
ples.
Flow-cytometric assay determined the type of cell deat
h. The real-time PCR analysis was used to evaluate
the alterations in mRNA levels of HR-related genes while their protein levels were measured using the ELISA
method.
γ
-H2AX levels were determined as a marker of DNA damage. We observed a synergistic relationship
between VPA and AZD2461 in all affected fractions of PC-3 cells (CI<0.9), but not in DU145 cells (CI>1.1).
Annexin-V staining analysis revealed a significant induction of apoptosis when PC-3 cells were treated with
VPA+AZD2461 (
p<0.05
). Both mRNA and protein levels of
Rad51
and
Mre11
were significantly decreased in
PC-3 cells co-treated with VPA+AZD2461 while enhanced
H2AX phosphorylation was found in PC-3 cells after
12 and 24 hours of co-treatment (
p<0.05
). Our findings established a preclinical rationale for selective targeting
of HR repair pathways by a combination of VPA and
AZD2461 as a mechanism for
reducing the HR pathway
sufficiency in
PTEN
-mutated prostate cancer cells.
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Keywords
AZD2461, Drug combination, Prostate cancer, PTEN, Valproic acid