Research Papers:

Proton pump inhibitors enhance the effects of cytotoxic agents in chemoresistant epithelial ovarian carcinoma

Yoo-Young Lee, Hye-Kyung Jeon, Ji Eun Hong, Young Jae Cho, Ji Yoon Ryu, Jung-Joo Choi, Sang Hoon Lee, Gun Yoon, Woo Young Kim, In-Gu Do, Min Kyu Kim, Tae-Joong Kim, Chel Hun Choi, Jeong-Won Lee _, Duk-Soo Bae and Byoung-Gie Kim

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Oncotarget. 2015; 6:35040-35050. https://doi.org/10.18632/oncotarget.5319

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Yoo-Young Lee1,*, Hye-Kyung Jeon1,*, Ji Eun Hong1, Young Jae Cho1, Ji Yoon Ryu1, Jung-Joo Choi1, Sang Hoon Lee2, Gun Yoon3, Woo Young Kim4, In-Gu Do5, Min Kyu Kim6, Tae-Joong Kim1, Chel Hun Choi1, Jeong-Won Lee1, Duk-Soo Bae1, Byoung-Gie Kim1

1Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

2Department of Obstetrics and Gynecology, Chung-Ang University School of Medicine, Seoul, Korea

3Department of Obstetrics and Gynecology, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea

4Department of Obstetrics and Gynecology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea

5Pathology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea

6Department of Obstetrics and Gynecology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea

*These authors have contributed equally to this work

Correspondence to:

Jeong-Won Lee, e-mail: [email protected]

Byoung-Gie Kim, e-mail: [email protected]

Keywords: epithelial ovarian cancer, microenvironment, V-ATPase, omeprazole, clear cell carcinoma

Received: April 27, 2015     Accepted: September 07, 2015     Published: September 19, 2015


This study was designed to investigate whether proton pump inhibitors (PPI, V-ATPase blocker) could increase the effect of cytotoxic agents in chemoresistant epithelial ovarian cancer (EOC). Expression of V-ATPase protein was evaluated in patients with EOC using immunohistochemistry, and patient survival was compared based on expression of V-ATPase mRNA from a TCGA data set. In vitro, EOC cell lines were treated with chemotherapeutic agents with or without V-ATPase siRNA or PPI (omeprazole) pretreatment. Cell survival and apoptosis was assessed using MTT assay and ELISA, respectively. In vivo experiments were performed to confirm the synergistic effect with omeprazole and paclitaxel on tumor growth in orthotopic and patient-derived xenograft (PDX) mouse models. Expression of V-ATPase protein in ovarian cancer tissues was observed in 44 patients (44/59, 74.6%). Higher expression of V-ATPase mRNA was associated with poorer overall survival in TCGA data. Inhibition of V-ATPase by siRNA or omeprazole significantly increased cytotoxicity or apoptosis to paclitaxel in chemoresistant (HeyA8-MDR, SKOV3-TR) and clear cell carcinoma cells (ES-2, RMG-1), but not in chemosensitive cells (HeyA8, SKOV3ip1). Moreover, the combination of omeprazole and paclitaxel significantly decreased the total tumor weight compared with paclitaxel alone in a chemoresistant EOC animal model and a PDX model of clear cell carcinoma. However, this finding was not observed in chemosensitive EOC animal models. These results show that omeprazole pretreatment can increase the effect of chemotherapeutic agents in chemoresistant EOC and clear cell carcinoma via reduction of the acidic tumor microenvironment.

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