title: Anti-tumor activity of olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, in cultured endometrial carcinoma cells.
abstract: BACKGROUND
  PTEN inactivation is the most frequent genetic aberration in endometrial cancer. One of the phosphatase-independent roles of PTEN is associated with homologous recombination (HR) in nucleus. Poly (ADP-ribose) polymerase (PARP) plays key roles in the repair of DNA single-strand breaks, and a PARP inhibitor induces synthetic lethality in cancer cells with HR deficiency. We examined the anti-tumor activity of olaparib, a PARP inhibitor, and its correlation between the sensitivity and status of PTEN in endometrial cancer cell lines.
  
  
  METHODS
  The response to olaparib was evaluated using a clonogenic assay with SF50 values (concentration to inhibit cell survival to 50%) in 16 endometrial cancer cell lines. The effects of PTEN on the sensitivity to olaparib and ionizing radiation (IR) exposure were compared between parental HEC-6 (PTEN-null) and HEC-6 PTEN + (stably expressing wild-type PTEN) cells by clonogenic assay, foci formation of RAD51 and γH2AX, and induction of cleaved PARP. The effects of siRNA to PTEN were analyzed in cells with wild-type PTEN.
  
  
  RESULTS
  The SF50 values were 100 nM or less in four (25%: sensitive) cell lines; whereas, SF50 values were 1,000 nM or more in four (25%: resistant) cell lines. PTEN mutations were not associated with sensitivity to olaparib (Mutant [n = 12]: 746 ± 838 nM; Wild-type [n = 4]: 215 ± 85 nM, p = 0.26 by Student's t test). RAD51 expression was observed broadly and was not associated with PTEN status in the 16 cell lines. The number of colonies in the clonogenic assay, the foci formation of RAD51 and γH2AX, and the induction of apoptosis were not affected by PTEN introduction in the HEC-6 PTEN + cells. The expression level of nuclear PTEN was not elevated within 24 h following IR in the HEC-6-PTEN + cells. In addition, knocking down PTEN by siRNA did not alter the sensitivity to olaparib in 2 cell lines with wild-type PTEN.
  
  
  CONCLUSIONS
  Our results suggest that olaparib, a PARP inhibitor, is effective on certain endometrial cancer cell lines. Inactivation of PTEN might not affect the DNA repair function. Predictive biomarkers are warranted to utilize olaparib in endometrial cancer.
authors.forename: Aki
authors.initials: A
authors.lastname: Miyasaka
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8655, Japan. katsutoshi-tky@umin.ac.jp.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Oda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Osamu
authors.initials: O
authors.lastname: Wada-Hiraike
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kashiyama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Enomoto
authors.forename: Noriko
authors.initials: N
authors.lastname: Hosoya
authors.forename: Takahiro
authors.initials: T
authors.lastname: Koso
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Fukuda
authors.forename: Kanako
authors.initials: K
authors.lastname: Inaba
authors.forename: Kenbun
authors.initials: K
authors.lastname: Sone
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Uehara
authors.forename: Reiko
authors.initials: R
authors.lastname: Kurikawa
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nagasaka
authors.forename: Yoko
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Takahide
authors.initials: T
authors.lastname: Arimoto
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kuramoto
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Miyagawa
authors.forename: Tetsu
authors.initials: T
authors.lastname: Yano
authors.forename: Kei
authors.initials: K
authors.lastname: Kawana
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Osuga
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Fujii
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects* / Q000528:radiation effects; D016889:Endometrial Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000378:metabolism; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D010793:Phthalazines / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D011839:Radiation, Ionizing
chemical_list: D000970:Antineoplastic Agents; C468783:H2AX protein, human; D006657:Histones; D010793:Phthalazines; D010879:Piperazines; D051135:Rad51 Recombinase; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C531550:olaparib