Research Papers:

Gamabufotalin triggers c-Myc degradation via induction of WWP2 in multiple myeloma cells

Zhenlong Yu, Tao Li, Chao Wang, Sa Deng, Baojing Zhang, Xiaokui Huo, Bo Zhang _, Xiaobo Wang, Yuping Zhong and Xiaochi Ma

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Oncotarget. 2016; 7:15725-15737. https://doi.org/10.18632/oncotarget.7398

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Zhenlong Yu1,*, Tao Li2,*, Chao Wang1, Sa Deng1, Baojing Zhang1, Xiaokui Huo1, Bo Zhang3, Xiaobo Wang1, Yuping Zhong4, Xiaochi Ma1

1College of Pharmacy, Academy of Integrative Medicine, Dalian Medical University, Dalian, China

2Department of Biology, College of Chemistry and Life Sciences, Zhejiang Normal University, Zhejiang, China

3Department of Neurosurgery, The Second Affiliated Hospital of Dalian Medical University, Dalian, China

4Department of Hematology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

*These authors contributed equally to this work

Correspondence to:

Bo Zhang, e-mail: Zhangbodl@126.com

Xiaochi Ma, e-mail: maxc1978@163.com

Keywords: gamabufotalin, multiple myeloma, c-Myc, degradation, WWP2

Received: October 13, 2015     Accepted: February 05, 2016     Published: February 15, 2016


Deciding appropriate therapy for multiple myeloma (MM) is challenging because of the occurrence of multiple chromosomal changes and the fatal nature of the disease. In the current study, gamabufotalin (GBT) was isolated from toad venom, and its tumor-specific cytotoxicity was investigated in human MM cells. We found GBT inhibited cell growth and induced apoptosis with the IC50 values <50 nM. Mechanistic studies using functional approaches identified GBT as an inhibitor of c-Myc. Further analysis showed that GBT especially evoked the ubiquitination and degradation of c-Myc protein, thereby globally repressing the expression of c-Myc target genes. GBT treatment inhibited ERK and AKT signals, while stimulating the activation of JNK cascade. An E3 ubiquitin-protein ligase, WWP2, was upregulated following JNK activation and played an important role in c-Myc ubiquitination and degradation through direct protein-protein interaction. The antitumor effect of GBT was validated in a xenograft mouse model and the suppression of MM-induced osteolysis was verified in a SCID-hu model in vivo. Taken together, our study identified the potential of GBT as a promising therapeutic agent in the treatment of MM.

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