title: Synergistic effect of olaparib with combination of cisplatin on PTEN-deficient lung cancer cells.
abstract: PARP enzyme plays a key role in the cellular machinery responsible for DNA damage repair. PTEN is a tumor-suppressor gene deactivating PI3K downstream of EGFR signaling. We hypothesize that PTEN-deficient lung cancer cells suppressed DNA damage signaling and that the absence of PTEN can sensitize these cells to a concurrent treatment of a DNA-damaging agent (cisplatin) and a PARP inhibitor (olaparib). To investigate the effect of olaparib and cisplatin on PTEN-deficient lung tumors, two EGFR-mutant (deletion in exon19) non-small cell lung cancer (NSCLC) cell lines, PC-9 (PTEN wild-type) and H1650 (PTEN loss), were used. We transfected intact PTEN gene into H1650 cells (H1650(PTEN+)) and knocked down PTEN expression in the PC-9 cells (PC-9(PTEN-)) using short hairpin RNA (shRNA). Combination of cisplatin with olaparib showed a synergistic effect in vitro according to the combination index in H1650 cells. Restoration of PTEN in the H1650 cells decreased sensitivity to the combination. Ablation of PTEN in PC-9 cells increased sensitivity to olaparib and cisplatin. We also examined the effectiveness of cisplatin and olaparib in a xenograft model using H1650 and PC-9(PTEN-) cells. The combination of cisplatin with olaparib was more effective than each agent individually. This effect was not observed in a xenograft model using H1650(PTEN+) and PC-9 cells. Mechanistic investigations revealed that PTEN deficiency caused reductions in nuclear RAD51 and RPA focus formation and phosphorylated Chk1 and Mre11. Thus, genetic inactivation of PTEN led to the suppression of DNA repair.
authors.affiliation: Department of Hematology, Oncology, and Respiratory Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ciences, Okayama, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Minami
authors.forename: Nagio
authors.initials: N
authors.lastname: Takigawa
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Takeda
authors.forename: Minoru
authors.initials: M
authors.lastname: Takata
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ochi
authors.forename: Eiki
authors.initials: E
authors.lastname: Ichihara
authors.forename: Akiko
authors.initials: A
authors.lastname: Hisamoto
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Hotta
authors.forename: Mitsune
authors.initials: M
authors.lastname: Tanimoto
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kiura
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000008:administration & dosage / Q000494:pharmacology*; D004249:DNA Damage; D004260:DNA Repair; D004357:Drug Synergism; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D051059:PTEN Phosphohydrolase / Q000172:deficiency* / Q000378:metabolism; D010793:Phthalazines / Q000008:administration & dosage / Q000494:pharmacology*; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D010793:Phthalazines; D010879:Piperazines; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D002945:Cisplatin; C531550:olaparib