Oncotarget

Research Papers:

Triptolide has anticancer and chemosensitization effects by down-regulating Akt activation through the MDM2/REST pathway in human breast cancer

Jing Xiong, Tiefen Su, Zhiling Qu, Qin Yang, Yu Wang, Jiansha Li and Sheng Zhou _

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Oncotarget. 2016; 7:23933-23946. https://doi.org/10.18632/oncotarget.8207

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Abstract

Jing Xiong1, Tiefen Su1, Zhiling Qu1, Qin Yang1, Yu Wang1, Jiansha Li1, Sheng Zhou1

1Institute of Pathology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China

Correspondence to:

Sheng Zhou, e-mail: zhou71@163.com

Keywords: breast neoplasms, MDM2, Akt, triptolide, REST

Received: August 04, 2015     Accepted: March 02, 2016     Published: March 19, 2016

ABSTRACT

Triptolide has been shown to exhibit anticancer activity. However, its mechanism of action is not clearly defined. Herein we report a novel signaling pathway, MDM2/Akt, is involved in the anticancer mechanism of triptolide. We observed that triptolide inhibits MDM2 expression in human breast cancer cells with either wild-type or mutant p53. This MDM2 inhibition resulted in decreased Akt activation. More specifically, triptolide interfered with the interaction between MDM2 and the transcription factor REST to increase expression of the regulatory subunit of PI3-kinase p85 and consequently inhibit Akt activation. We further showed that, regardless of p53 status, triptolide inhibited proliferation, induced apoptosis, and caused G1 phase cell cycle arrest. Triptolide also enhanced the cytotoxic effect of doxorubicin. MDM2 inhibition plays a causative role in these effects. The inhibitory effect of triptolide on MDM2-mediated Akt activation was eliminated with MDM2 overexpression. MDM2-overexpressing tumor cells, in turn, were less susceptible to the anticancer and chemosensitization effects of triptolide than control cells. Triptolide also exhibited anticancer and chemosensitization effects in nude mouse xenograft model. When it was administered to tumor-bearing nude mice, triptolide inhibited tumor growth and enhanced the antitumor effects of doxorubicin. In summary, triptolide has anticancer and chemosensitization effects by down-regulating Akt activation through the MDM2/REST pathway in human breast cancer. Our study helps to elucidate the p53-independent regulatory function of MDM2 in Akt signaling, offering a novel view of the mechanism by which triptolide functions as an anticancer agent.


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