Co-inhibition of pol θ and HR genes efficiently synergize with cisplatin to suppress cisplatin-resistant lung cancer cells survival
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Chun-Hua Dai1, Ping Chen2, Jian Li2, Tin Lan3, Yong-Chang Chen3, Hai Qian3, Kang Chen2, Mei-Yu Li2
1Department of Radiation Oncology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
2Department of Pulmonary Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, China
3Institute of Medical Science, Jiangsu University, Zhenjiang, China
Jian Li, email: firstname.lastname@example.org
Keywords: lung cancer cells, cisplatin-resistance, translesion synthesis, pol θ, homologous recombination
Received: March 05, 2016 Accepted: July 18, 2016 Published: August 11, 2016
Cisplatin exert its anticancer effect by creating intrastrand and interstrand DNA cross-links which block DNA replication and is a major drug used to treat lung cancer. However, the main obstacle of the efficacy of treatment is drug resistance. Here, we show that expression of translesion synthesis (TLS) polymerase Q (POLQ) was significantly elevated by exposure of lung cancer cells A549/DR (a cisplatin-resistant A549 cell line) to cisplatin. POLQ expression correlated inversely with homologous recombination (HR) activity. Co-depletion of BRCA2 and POLQ by siRNA markedly increased sensitivity of A549/DR cells to cisplatin, which was accompanied with impairment of double strand breaks (DSBs) repair reflected by prominent cell cycle checkpoint response, increased chromosomal aberrations and persistent colocalization of p-ATM and 53BP1 foci induced by cisplatin. Thus, co-knockdown of POLQ and HR can efficiently synergize with cisplatin to inhibit A549/DR cell survival by inhibiting DNA DSBs repair. Similar results were observed in A549/DR cells co-depleted of BRCA2 and POLQ following BMN673 (a PARP inhibitor) treatment. Importantly, the sensitization effects to cisplatin and BMN673 in A549/DR cells by co-depleting BRCA2 and POLQ was stronger than those by co-depleting BRCA2 and other TLS factors including POLH, REV3, or REV1. Our results indicate that there is a synthetic lethal relationship between pol θ-mediated DNA repair and HR pathways. Pol θ may be considered as a novel target for lung cancer therapy.
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