TY - JOUR
T1 - Valproic acid sensitizes breast cancer cells to hydroxyurea through inhibiting RPA2 hyperphosphorylation-mediated DNA repair pathway
AU - Tian, Youjia
AU - Liu, Guochao
AU - Wang, Hui
AU - Tian, Zhujun
AU - Cai, Zuchao
AU - Zhang, Fengmei
AU - Luo, Yue
AU - Wang, Shue
AU - Guo, Gongshe
AU - Wang, Xiaowei
AU - Powell, Simon
AU - Feng, Zhihui
N1 - Funding Information:
This study was supported by grants from National Natural Science Foundation of China (No. 81472800 ), and Shandong University of Science and Technology of Shandong Province ( 2013GGE27052 , 2014GGH218010 ).
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/10
Y1 - 2017/10
N2 - It was reported that valproic acid (VPA, a histone deacetylase inhibitor) can sensitize cancer cells to hydroxyurea (HU, a ribonucleotide reductase inhibitor) for chemotherapy, although the mechanism of VPA-induced HU sensitization is unclear. In this study, we systematically characterized VPA-induced HU sensitization of breast cancer cells. Multiple breast cancer cell models were employed to investigate whether the safe concentration of 0.5 mM VPA and 2 mM HU can result in DNA double-strand breaks (DSBs) and impact cell survival. Furthermore, the underlying mechanism was explored through cell biology assays, including clonogenic survival, homologous recombination (HR) activity, immunoblot and immunofluorescence. We found that VPA and HU cooperatively suppressed cancer cell survival. VPA resulted in the accumulation of more DNA double-strand breaks (DSBs) in response to HU-induced replication arrest and was able to block HU-stimulated homologous recombination (HR) through inhibiting the activity of two key HR repair proteins by hyperphosphorylation of replication protein A2 (RPA2-p) and recombinase Rad51. However, apoptosis was not detected under this condition. In addition, the results from the survival fraction in the cells expressing defective RPA2-p showed that VPA disrupted the HU-induced RPA2-p-Rad51-mediated HR pathway. Importantly, these findings were further supported by analyzing primary-culture cells from the tissue of chemical carcinogen (DMBA)-induced breast cancer in rats. Thus, our data demonstrated that VPA and HU synergistically suppressed tumor cells via disturbing RPA2-p-mediated DNA repair pathway, which provides a new way for combining chemotherapeutic drugs to sensitize breast cancer cells.
AB - It was reported that valproic acid (VPA, a histone deacetylase inhibitor) can sensitize cancer cells to hydroxyurea (HU, a ribonucleotide reductase inhibitor) for chemotherapy, although the mechanism of VPA-induced HU sensitization is unclear. In this study, we systematically characterized VPA-induced HU sensitization of breast cancer cells. Multiple breast cancer cell models were employed to investigate whether the safe concentration of 0.5 mM VPA and 2 mM HU can result in DNA double-strand breaks (DSBs) and impact cell survival. Furthermore, the underlying mechanism was explored through cell biology assays, including clonogenic survival, homologous recombination (HR) activity, immunoblot and immunofluorescence. We found that VPA and HU cooperatively suppressed cancer cell survival. VPA resulted in the accumulation of more DNA double-strand breaks (DSBs) in response to HU-induced replication arrest and was able to block HU-stimulated homologous recombination (HR) through inhibiting the activity of two key HR repair proteins by hyperphosphorylation of replication protein A2 (RPA2-p) and recombinase Rad51. However, apoptosis was not detected under this condition. In addition, the results from the survival fraction in the cells expressing defective RPA2-p showed that VPA disrupted the HU-induced RPA2-p-Rad51-mediated HR pathway. Importantly, these findings were further supported by analyzing primary-culture cells from the tissue of chemical carcinogen (DMBA)-induced breast cancer in rats. Thus, our data demonstrated that VPA and HU synergistically suppressed tumor cells via disturbing RPA2-p-mediated DNA repair pathway, which provides a new way for combining chemotherapeutic drugs to sensitize breast cancer cells.
KW - Breast cancer cells
KW - HR
KW - HU
KW - RPA2-p
KW - VPA
UR - http://www.scopus.com/inward/record.url?scp=85027729016&partnerID=8YFLogxK
U2 - 10.1016/j.dnarep.2017.08.002
DO - 10.1016/j.dnarep.2017.08.002
M3 - Article
C2 - 28837865
AN - SCOPUS:85027729016
SN - 1568-7864
VL - 58
SP - 1
EP - 12
JO - DNA Repair
JF - DNA Repair
ER -