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Inhibition of Cell Death and Induction of G2 Arrest Accumulation in Human Ovarian Clear Cells by HNF-1β Transcription Factor: Chemosensitivity Is Regulated by Checkpoint Kinase CHK1

Shigetomi, Hiroshi MD*; Sudo, Tamotsu MD, PhD; Shimada, Keiji MD, PhD; Uekuri, Chiharu MD, PhD*; Tsuji, Yoriko MD, PhD*; Kanayama, Seiji MD, PhD*; Naruse, Katsuhiko MD, PhD*; Yamada, Yoshihiko MD, PhD§; Konishi, Noboru MD, PhD; Kobayashi, Hiroshi MD, PhD*

International Journal of Gynecological Cancer: June 2014 - Volume 24 - Issue 5 - p 838–843
doi: 10.1097/IGC.0000000000000136
Basic Science

Objective Appropriate cell cycle checkpoints are essential for the maintenance of normal cells and chemosensitivity of cancer cells. Clear cell adenocarcinoma (CCA) of the ovary is highly resistant to chemotherapy. Hepatocyte nuclear factor-1β (HNF-1β) is known to be overexpressed in CCA, but its role and clinical significance is unclear. We investigated the role of HNF-1β in regulation of the cell cycle in CCA.

Methods To clarify the effects of HNF-1β on cell cycle checkpoints, we compared the cell cycle distribution and the expression of key proteins involved in CCA cells in which HNF-1β had been stably knocked down and in vector-control cell lines after treatment with bleomycin. HNF-1β (+) cells were arrested in G2 phase because of DNA damage.

Results HNF-1β (−) cells died because of a checkpoint mechanism. G2 arrest of HNF-1β (+) cells resulted from sustained CHK1 activation, a protein that plays a major role in the checkpoint mechanism. HNF-1β (+) cells were treated with a CHK1 inhibitor after bleomycin treatment. Flow cytometric analysis of the cell cycle demonstrated that DNA damage–induced G2-arrested cells were released from the checkpoint and killed by a CHK1 inhibitor.

Conclusions The chemoresistance of CCA may be due to aberrant retention of the G2 checkpoint through overexpression of HNF-1β. This is the first study demonstrating cell cycle regulation and chemosensitization by a CHK1 inhibitor in CCA.

*Department of Obstetrics and Gynecology, Nara Medical University, Kashihara, Nara; †Section of Translational Research, Hyogo Cancer Center, Akashi, Hyogo; ‡Department of Pathology, Nara Medical University, Kashihara, Nara; and §Department of Obstetrics and Gynecology, Yao Municipal Hospital, Yao-city, Osaka, Japan.

Address correspondence and reprint requests to Hiroshi Kobayashi, MD, PhD, Department of Obstetrics and Gynecology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. E-mail:

The authors declare no conflicts of interest.

Received December 19, 2013

Accepted February 27, 2014

© 2014 by the International Gynecologic Cancer Society and the European Society of Gynaecological Oncology.