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S100A7 induction is repressed by YAP via the Hippo pathway in A431 cells.

ABSTRACT: YAP is an oncogenic transcriptional co-activator and is inhibited by the Hippo pathway. Recent studies have revealed that YAP is also a sensor of cell morphology and cell density and can be phosphorylated by cytoskeleton reorganization. Our previous study demonstrated that S100A7 was upregulated in several squamous cell carcinoma (SCC) specimens and was dramatically induced in SCC cells by suspension and dense culture as well as in xenografts. However, little is known about how S100A7 induction occurs in cancer cells. Here, we identify that S100A7 induction is accompanied by YAP phosphorylation in both suspended and dense A431 cells. This correlation reverses after recovery of cell attachment or relief from dense culture. Further examination finds that S100A7 induction is repressed by nuclear YAP, which is further validated by activation or inhibition of the Hippo pathway via loss- and/or gain-of- LATS1 and MST1 function. Strikingly, disruption of the F-actin promotes S100A7 expression via YAP by activation of the Hippo pathway. Furthermore, we demonstrate that repression of S100A7 by YAP required TEAD1 transcriptional factor. Taken together, our findings demonstrate for the first time that S100A7 is repressed by YAP via the Hippo pathway.

SUBMITTER: Li Y

PROVIDER: S-EPMC5122377 | biostudies-other | 2016 Jun

REPOSITORIES: biostudies-other

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S100A7 induction is repressed by YAP via the Hippo pathway in A431 cells.

Li Yunguang Y Kong Fei F Wang Junhao J Hu Enze E Wang Rui R Liu Jin J Xiao Qianqian Q Zhang Weiqing W He Dacheng D Xiao Xueyuan X

Oncotarget 20160601 25

YAP is an oncogenic transcriptional co-activator and is inhibited by the Hippo pathway. Recent studies have revealed that YAP is also a sensor of cell morphology and cell density and can be phosphorylated by cytoskeleton reorganization. Our previous study demonstrated that S100A7 was upregulated in several squamous cell carcinoma (SCC) specimens and was dramatically induced in SCC cells by suspension and dense culture as well as in xenografts. However, little is known about how S100A7 induction ...[more]

PMID: 27203549

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Project description:BackgroundOsteosarcoma (OS) is the most prevalent primary bone malignancy affecting adolescents, yet the emergence of chemoradiotherapeutic resistance has limited efforts to cure affected patients to date. Pyropheophorbide-α methyl ester-mediated photodynamic therapy (MPPa-PDT) is a recently developed, minimally invasive treatment for OS that is similarly constrained by such therapeutic resistance. This study sought to explore the mechanistic basis for RhoA-activated YAP1 (YAP)-mediated resistance in OS.MethodsThe relationship between YAP expression levels and patient prognosis was analyzed, and YAP levels in OS cell lines were quantified. Immunofluorescent staining was used to assess YAP nuclear translocation. OS cell lines (HOS and MG63) in which RhoA and YAP were knocked down or overexpressed were generated using lentiviral vectors. CCK-8 assays were used to examine OS cell viability, while the apoptotic death of these cells was monitored via Hoechst staining, Western blotting, and flow cytometry. Tumor-bearing nude mice were additionally used to assess the relationship between lentivirus-mediated alterations in RhoA expression and MPPa-PDT treatment outcomes. TUNEL and immunohistochemical staining approaches were leveraged to assess apoptotic cell death in tissue samples.ResultsOS patients exhibited higher levels of YAP expression, and these were correlated with a poor prognosis. MPPa-PDT induced apoptosis in OS cells, and such MPPa-PDT-induced apoptosis was enhanced following YAP knockdown whereas it was suppressed by YAP overexpression. RhoA and YAP expression levels were positively correlated in OS patients, and both active and total RhoA protein levels rose in OS cells following MPPa-PDT treatment. When RhoA was knocked down, levels of unphosphorylated YAP and downstream target genes were significantly reduced, while RhoA/ROCK2/LIMK2 pathway phosphorylation was suppressed, whereas RhoA overexpression resulted in the opposite phenotype. MPPa-PDT treatment was linked to an increase in HMGCR protein levels, and the inhibition of RhoA or HMGCR was sufficient to suppress RhoA activity and to decrease the protein levels of YAP and its downstream targets. Mevalonate administration partially reversed these reductions in the expression of YAP and YAP target genes. RhoA knockdown significantly enhanced the apoptotic death of OS cells in vitro and in vivo following MPPa-PDT treatment, whereas RhoA overexpression had the opposite effect.ConclusionsThese results suggest that the mevalonate pathway activates RhoA, which in turn activates YAP and promotes OS cell resistance to MPPa-PDT therapy. Targeting the RhoA/ROCK2/LIMK2/YAP pathway can significantly improve the efficacy of MPPa-PDT treatment for OS.

Dataset Information

S100A7 induction is repressed by YAP via the Hippo pathway in A431 cells.

Publications

S100A7 induction is repressed by YAP via the Hippo pathway in A431 cells.

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