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1.
Cancer Cell Int ; 18: 209, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30574018

RESUMO

BACKGROUND: It has been demonstrated that bufadienolides exert potent anti-cancer activity in various tumor types. However, the mechanisms that underlie their anti-cancer properties remain unclear. Yes-associated protein, a key effector of Hippo signaling, functions as a transcription coactivator, plays oncogenic and tumor suppressor roles under different conditions. Here, we report that arenobufagin (ABF), a representative bufadienolide, induced breast cancer MCF-7 cells to undergo apoptosis, which occurred through the JNK-mediated multisite phosphorylation of YAP. METHODS: Cytotoxicity was examined using an MTT assay. ABF-induced apoptosis was measured with a TUNEL assay and Annexin V-FITC/PI double staining assay. Western blotting, immunofluorescence, qRT-PCR and coimmunoprecipitation were employed to assess the expression levels of the indicated molecules. Lose-of-function experiments were carried out with siRNA transfection and pharmacological inhibitors. ABF-induced phosphopeptides were enriched with Ti4+-IMAC chromatography and further subjected to reverse-phase nano-LC-MS/MS analysis. RESULTS: ABF significantly reduced the viability of MCF-7 cells and increased the percentage of early and late apoptotic cells in a concentration- and time-dependent manner. Following ABF treatment, YAP accumulated in the nucleus and bound to p73, which enhanced the transcription of the pro-apoptotic genes Bax and p53AIP1. YAP knock-down significantly attenuated ABF-induced apoptotic cell death. Importantly, we found that the mobility shift of YAP was derived from its phosphorylation at multiple sites, including Tyr357. Moreover, mass spectrometry analysis identified 19 potential phosphorylation sites in YAP, with a distribution of 14 phosphoserine and 5 phosphothreonine residues. Furthermore, we found that the JNK inhibitor SP600125 completely diminished the mobility shift of YAP and its phosphorylation at Tyr357, the binding of YAP and p73, the transcription of Bax and p53AIP1 as well as the apoptosis induced by ABF. These data indicate that ABF induced YAP multisite phosphorylation, which was associated with p73 binding, and that apoptosis was mediated by the JNK signaling pathway. CONCLUSIONS: Our data demonstrate that ABF suppresses MCF-7 breast cancer proliferation by triggering the pro-apoptotic activity of YAP, which is mediated by JNK signaling-induced YAP multisite phosphorylation as well as its association with p73. The present work not only provides additional information on the use of ABF as an anti-breast cancer drug, but also offers evidence that the induction of the tumor suppressor role of YAP may be a therapeutic strategy.

2.
Am J Transl Res ; 10(11): 3664-3676, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30662617

RESUMO

Cyclin-dependent kinase 7 (CDK7) is a member of the CDK family, which forms the CDK activating kinase complex with Cyclin H and RING finger protein Mat1 to control cell cycle progression and transcription by phosphorylating other CDKs and RNA polymerase II. In this study, we analyzed TCGA data and found that upregulation of CDK7 frequently occurred in human gastric cancer. A potent and selective irreversible CDK7 inhibitor THZ2 was able to induce cell growth inhibition, cell cycle arrest at G2/M phase and apoptosis with the increasing intracellular reactive oxidative species (ROS) levels in gastric cancer cells. Pretreatment with ROS scavenger N-acety-L-cysteine partially reversed cell apoptosis induced by THZ2. In the nude mice, THZ2 also suppressed the growth of xenograft tumors of gastric cancer. Overall, our data showed that inhibition of CDK7 with THZ2 in gastric cancer presented outstanding anticancer effect in vitro and in vivo, suggesting that CDK7 is a potential therapeutic target for gastric cancer patients.

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