GTP bound RAS activates signaling cascades via binding and stimulating downstream

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GTP bound RAS activates signaling cascades via binding and stimulating downstream  Empty GTP bound RAS activates signaling cascades via binding and stimulating downstream

Post  huwan123456 on Wed Aug 13, 2014 8:26 am

In contrast, when the same ETS proteins were over expressed in RWPE KRAS cells, none of the oncogenic ETS proteins induced additional cell migration, suggesting that these ETS proteins and KRAS were functioning to activate the same pathway. KU-0063794 臨床試験 These findings are consistent with our model that oncogenic ETS proteins can mimic RAS activation in cell lines lacking RAS activity, and are distinct from ETS proteins expressed in normal prostate. A role for the PI3K AKT pathway in oncogenic ETS function To identify signaling pathways required for the onco genic function of ETS factors, a microarray analysis of ETV4 knockdown in PC3 prostate cancer cells was compared to the Connectivity Map database that contains microarray data of PC3 cells treated with 1309 small molecules, including many signaling pathway in hibitors.

Similarities between the gene expression profile of a signaling pathway inhibitor and ETV4 knockdown would predict a role for that pathway in oncogenic ETS function. The top two, and three of the top Lenalidomide 臨床試験 five small molecules that induced gene expression changes most similar to ETV4 knockdown were inhibitors of either PI3K or mTOR, a downstream effector of PI3K. These data suggest that in PC3 cells, PI3K and ETV4 ac tivate a similar gene expression program. To test if the PI3K pathway is required for an onco genic ETS protein to promote the cell migration pheno type, RWPE ERG and RWPE KRAS cells were treated with the PI3K inhibitor, LY294002. LY294002 reduced AKT phosphorylation in both lines, consistent with PI3K inhibition.

Strikingly, PI3K inhibition completely abrogated cell migration induced by ERG, but not cell migration induced by KRAS. In fact RWPE KRAS cells actually migrated more when PI3K was inhibited. This increased migration may be due to relief of RAF inhib ition by AKT, as RWPE KRAS cells had higher pMEK levels buy LY294002 after treatment by LY294002. To confirm the role of PI3K, a second PI3K inhibitor, ZSTK474, was also tested. Like LY294002, ZSTK474 significantly reduced migration of RWPE ERG cells, but not RWPE KRAS cells. Cell mi gration induced by other oncogenic ETS factors, ETV1, and ETV5, was also abrogated by PI3K inhibition. A second cell migration assay, the scratch assay, confirmed that PI3K inhibition re duced migration caused by ERG expression, but not migra tion caused by KRAS.

An AKT inhibitor had a similar effect, indicating that PI3K is functioning via AKT activation. These results indicate that overexpression of an oncogenic ETS gene can switch the control of prostate cell migration from the RAS ERK path way to the PI3K AKT pathway. We next tested if the PI3K pathway was regulating the ability of ERG to activate the transcription of RAS and ERG responsive target genes near enhancers that are co occupied by ETS and AP 1 proteins. The expression levels of two such genes, ARHGAP29, and SMAD3, were mea sured by quantitative reverse transcription PCR. Both ARHGAP29 and SMAD3 have roles in cell migration and or cell morphology, are direct targets of oncogenic ETS proteins and AP 1 by ChIP seq, and are activated by KRAS and oncogenic ETS expression. Similar to the cell migration phenotype, the activation of both genes was significantly attenuated by PI3K inhibition in RWPE ERG cells, but not in RWPE KRAS cells.


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