Combination of a novel HDAC inhibitor OBP-801/YM753 and a PI3K inhibitor LY294002 synergistically induces apoptosis in human endometrial carcinoma cells due to increase of Bim with accumulation of ROS
Highlights
► OBP-801/YM753 combined with LY294002 augments the growth-inhibitory effect in endometrial carcinoma cells with the synergistic induction of apoptosis. ► The apoptosis induced by the combination is dependent on the induction of Bim through the accumulation of ROS. ► The apoptosis-inducing effect of OBP-801/YM753 with LY294002 is more potent than that of SAHA with LY294002.
Introduction
Endometrial carcinoma is one of the most common cancers of the female genital tract. One hundred and fifty thousand women are newly diagnosed annually worldwide [1]. About 90% of endometrial carcinomas are sporadic, and about 10% are hereditary [2]. The majority of endometrial carcinomas have been diagnosed in postmenopausal women, but recently about 25–30% of cases are diagnosed in premenopausal women younger than 50 years [3]. So far, many clinical trials have been performed [4], [5], [6], [7], but there are few effective treatments for progressive or recurrent cases.
HDAC inhibitors are expected for the treatment of various cancers. Also in endometrial carcinoma cells, HDAC inhibitors have been reported to induce cell cycle arrest and apoptosis [8], [9], [10]. On the other hand, the PI3K/Akt pathway is known to be activated with mutations in PIK3CA and PTEN in most endometrial carcinomas [11], and PI3K inhibitors show a growth-inhibitory effect on the cancer cells [12], [13]. It has been reported that combined treatment with a HDAC inhibitor and a PI3K inhibitor is effective for other malignant tumor cells [14], [15], [16], [17].
In the present study, our objective was to examine the combined effect of a novel HDAC inhibitor OBP-801/YM753 and a PI3K inhibitor LY294002 against endometrial carcinoma cells with the elucidation of the molecular mechanisms by these drugs.
Section snippets
Cell culture
Human endometrial adenocarcinoma HEC-1A cells were maintained in RPMI medium, containing 10% fetal bovine serum at 37 °C in 5% CO2.
Reagents
OBP-801/YM753 was provided from Oncolys Biopharma (Japan). LY294002 was purchased from Cell Signaling Technology (Beverly, MA). SAHA was purchased from Biomol Research Laboratories (Plymouth Meeting, PA). N-acetyl-l-cysteine (NAC) was purchased from Nacalai Tesque, Inc. (Japan). The pan-caspase inhibitor zVAD-fmk was purchased from R&D Systems (Minneapolis, MN).
Cell viability assay
Cell
OBP-801/YM753 or LY294002 inhibits cell growth of human endometrial carcinoma HEC-1A cells
We investigated the effects of OBP-801/YM753 or LY294002 on the cell growth of human endometrial carcinoma HEC-1A cells. OBP-801/YM753 was originally identified as a novel HDAC inhibitor by us using a p21 promoter reporter assay [19]. OBP-801/YM753 showed the most potent HDAC-inhibitory activity among all HDAC inhibitors available; i.e., it showed about 50 times more effective activity than that of SAHA, the most clinically used HDAC inhibitor [19]. OBP-801/YM753 at 3.1 nM or more inhibited cell
Discussion
In endometrial carcinoma, an effective chemotherapeutic strategy has been required for recurrent and advanced cases [4], [5], [6], [7]. In this study, we showed the synergistic effect of combined treatment with a novel HDAC inhibitor OBP-801/YM753 and a PI3K inhibitor LY294002 against endometrial carcinoma cells. This is the first report to show the efficacy of the combination of HDAC and PI3K inhibitors against human endometrial carcinoma cells.
In the present data, we have first found that Bim
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Acknowledgments
We are grateful to Dr. M. Horinaka, Y. Sowa, and T. Mori for useful discussion. This study was partially supported by a grant-in-aid from the Japanese Ministry of Education, Culture, Sports, Science and Technology, and a grant-in-aid for the Encouragement of Young Scientists from the Japan Society for the Promotion of Science.
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