Open Access Highly Accessed Research article

Anti-tumor activity of olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, in cultured endometrial carcinoma cells

Aki Miyasaka1, Katsutoshi Oda1*, Yuji Ikeda1, Osamu Wada-Hiraike1, Tomoko Kashiyama1, Atsushi Enomoto2, Noriko Hosoya2, Takahiro Koso1, Tomohiko Fukuda1, Kanako Inaba1, Kenbun Sone1, Yuriko Uehara1, Reiko Kurikawa1, Kazunori Nagasaka1, Yoko Matsumoto1, Takahide Arimoto1, Shunsuke Nakagawa3, Hiroyuki Kuramoto4, Kiyoshi Miyagawa2, Tetsu Yano5, Kei Kawana1, Yutaka Osuga1 and Tomoyuki Fujii1

Author Affiliations

1 Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8655, Japan

2 Laboratory of Molecular Radiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

3 Department of Obstetrics and Gynecology, Faculty of Medicine, Teikyo University, Tokyo, Japan

4 Kanagawa Health Service Association, Kanagawa, Japan

5 Department of Obstetrics and Gynecology, National Center for Global Health and Medicine, Tokyo, Japan

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BMC Cancer 2014, 14:179  doi:10.1186/1471-2407-14-179

Published: 13 March 2014

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.

Keywords:
PARP inhibitor; Homologous recombination; Endometrial cancer; PTEN; RAD51