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Cyclopeptide RA-V Inhibits Organ Enlargement and Tumorigenesis Induced by YAP Activation.

ABSTRACT: The Hippo pathway restricts organ size during development and its inactivation plays a crucial role in cancer. Yes-associated protein (YAP) and its paralog transcriptional coactivator with PSD-95/Dlg/ZO-1 (PDZ)-binding motif (TAZ) are transcription co-activators and effectors of the Hippo pathway mediating aberrant enlargement of organs and tumor growth upon Hippo pathway inactivation. It has been demonstrated that genetic inactivation of YAP could be an effective approach to inhibit tumorigenesis. In order to identify pharmacological inhibitors of YAP, we screened a library of 52,683 compounds using a YAP-specific reporter assay. In this screen we identified cyclopeptide RA-V (deoxybouvardin) as a specific inhibitor of YAP and TAZ but not other reporters. Unexpectedly, later experiments demonstrated that RA-V represses the protein but not mRNA levels of YAP target genes. Nevertheless, RA-V strongly blocks liver enlargement induced by Mst1/2 knockout. Furthermore, RA-V not only inhibits liver tumorigenesis induced by YAP activation, but also induces regression of established tumors. We found that RA-V inhibits dedifferentiation and proliferation, while inducing apoptosis of hepatocytes. Furthermore, RA-V also induces apoptosis and inhibits proliferation of macrophages in the microenvironment, which are essential for YAP-induced tumorigenesis. RA-V is thus a drug candidate for cancers involving YAP/TAZ activation.

SUBMITTER: Ji X

PROVIDER: S-EPMC6265802 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Cyclopeptide RA-V Inhibits Organ Enlargement and Tumorigenesis Induced by YAP Activation.

Ji Xinyan X Song Lihua L Sheng Li L Gao Anhui A Zhao Yang Y Han Shixun S Zhang Yuchao Y Zhu Chu C Zhao Simeng S Wang Zhe Z Xu Bohan B Li Li L Li Jia J Tan Ninghua N Zhao Bin B

Cancers 20181116 11

The Hippo pathway restricts organ size during development and its inactivation plays a crucial role in cancer. Yes-associated protein (YAP) and its paralog transcriptional coactivator with PSD-95/Dlg/ZO-1 (PDZ)-binding motif (TAZ) are transcription co-activators and effectors of the Hippo pathway mediating aberrant enlargement of organs and tumor growth upon Hippo pathway inactivation. It has been demonstrated that genetic inactivation of YAP could be an effective approach to inhibit tumorigenes ...[more]

PMID: 30453531

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Project description:The hallmark of Kaposi’s sarcoma (KS), the most common cancer in HIV-infected patients caused by Kaposi’s sarcoma-associated herpesvirus (KSHV) infection, is hyperinflammation. However, the role of inflammation and the mechanism of induction of inflammation in KSHV-induced cancer remain unclear. In a previous high-throughput screening against KSHV-induced oncogenesis, over half of the identified candidates were anti-inflammatory agents. Among them, dexamethasone, a common anti-inflammatory corticosteroid, functions through binding to and activating glucocorticoid receptor (GR). In this study, we examined the mechanism mediating KSHV-induced inflammation. We found that numerous inflammatory pathways were activated in KSHV-transformed cells. Particularly, the interleukin-1 alpha (IL-1α) and IL-1 receptor antagonist (IL-1Ra) from the IL-1 family, implicated in a wide variety of inflammatory diseases, were the most induced and suppressed cytokines in KSHV-transformed KMM cells compared to the matched primary MM cells, respectively. By using reverse genetics, we showed that KSHV-encoded miRNAs mediated IL-1α induction while both miRNAs and vFLIP mediated IL-1Ra suppression. Furthermore, the GR signaling was inhibited in KSHV-transformed cells, which was mediated by vFLIP and vCyclin. Importantly, dexamethasone treatment inhibited cell proliferation, and colony formation in softagar of KMM cells but had a minimal effect on MM cells. Consequently, dexamethasone suppressed the initiation and growth of KS-like KMM tumors in mice. Mechanistically, dexamethasone suppressed IL-1α expression but induced IL-1Ra expression. Treatment with recombinant IL-1α protein was sufficient to rescue the inhibitory effect of dexamethasone while overexpression of IL-1Ra alone caused a weak growth inhibition of KMM cells. Furthermore, dexamethasone induced IκBα expression resulting in the inhibition of the classical and alternative NF-kB pathways and IL-1α expression. Taken together, these results revealed the important role of IL-1 signaling pathway in KSHV-induced inflammation and oncogenesis, which can be inhibited by dexamethasone-activated GR signaling. This study determined the mechanism of inflammation in KSHV-induced oncogenesis and identified IL-1-mediated inflammation as a potential therapeutic target for KSHV-induced malignancies.

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Cyclopeptide RA-V Inhibits Organ Enlargement and Tumorigenesis Induced by YAP Activation.

Publications

Cyclopeptide RA-V Inhibits Organ Enlargement and Tumorigenesis Induced by YAP Activation.

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