Dataset Information

The splicing-factor oncoprotein SF2/ASF activates mTORC1.

ABSTRACT: The splicing factor SF2/ASF is an oncoprotein that is up-regulated in many cancers and can transform immortal rodent fibroblasts when slightly overexpressed. The mTOR signaling pathway is activated in many cancers, and pharmacological blockers of this pathway are in clinical trials as anticancer drugs. We examined the activity of the mTOR pathway in cells transformed by SF2/ASF and found that this splicing factor activates the mTORC1 branch of the pathway, as measured by S6K and eIF4EBP1 phosphorylation. This activation is specific to mTORC1 because no activation of Akt, an mTORC2 substrate, was detected. mTORC1 activation by SF2/ASF bypasses upstream PI3K/Akt signaling and is essential for SF2/ASF-mediated transformation, as inhibition of mTOR by rapamycin blocked transformation by SF2/ASF in vitro and in vivo. Moreover, shRNA-mediated knockdown of mTOR, or of the specific mTORC1 and mTORC2 components Raptor and Rictor, abolished the tumorigenic potential of cells overexpressing SF2/ASF. These results suggest that clinical tumors with SF2/ASF up-regulation could be especially sensitive to mTOR inhibitors.

SUBMITTER: Karni R

PROVIDER: S-EPMC2563124 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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The splicing-factor oncoprotein SF2/ASF activates mTORC1.

Karni Rotem R Hippo Yoshitaka Y Lowe Scott W SW Krainer Adrian R AR

Proceedings of the National Academy of Sciences of the United States of America 20081001 40

The splicing factor SF2/ASF is an oncoprotein that is up-regulated in many cancers and can transform immortal rodent fibroblasts when slightly overexpressed. The mTOR signaling pathway is activated in many cancers, and pharmacological blockers of this pathway are in clinical trials as anticancer drugs. We examined the activity of the mTOR pathway in cells transformed by SF2/ASF and found that this splicing factor activates the mTORC1 branch of the pathway, as measured by S6K and eIF4EBP1 phospho ...[more]

PMID: 18832178

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Project description:Our previous study revealed that microRNA (miR) ‑30c represents a potential tumor suppressor gene, the expression of which is associated with decreased oncogenic potential in prostate cancer (PCa) cell lines. However, the functional role and underlying mechanisms of miR‑30c in PCa remain to be fully elucidated. Reverse transcription‑quantitative polymerase chain reaction and immunohistochemical analysis were used to detect the expression levels of alternative splicing factor/splicing factor 2 (ASF/SF2) in PCa tissues. A luciferase reporter assay was used to investigate whether ASF/SF2 may be a direct target gene of miR‑30c. In addition, the effects of miR‑30c on the proliferation and apoptosis of PCa cell lines were examined, following transfection with miR‑30c mimics. Furthermore, correlation analysis was performed to investigate the relationship between the expression of miR‑30c and ASF/SF2 and various clinicopathological parameters of patients with PCa. The present results demonstrated that PCa tissues exhibited higher levels of alternative splicing factor/splicing factor 2 (ASF/SF2), compared with normal tissues. In addition, miR‑30c was revealed to targete the 3'‑untranslated region of the ASF/SF2 gene, causing a decrease in the mRNA and protein levels of ASF/SF2. Furthermore, miR‑30c was reported to decrease cell proliferation, increase the percentage of cells in the G1 cell cycle phase, and promote apoptosis through the inhibition of ASF/SF2. Following correlation analysis using patient samples, the expression of ASF/SF2 was revealed to be tightly correlated with the pathological stage of PCa and biochemical recurrence (BCR). In addition, patients with PCa exhibiting low expression levels of miR‑30c and high expression of ASF/SF2 had significantly lower rates of BCR‑free survival. In conclusion, the present study suggested that the tumor suppressor miR‑30c may be involved in PCa tumorigenesis, possibly via targeting ASF/SF2. The combined analysis of the expression of ASF/SF2 and miR‑30c may be a valuable tool for early prediction of BCR in patients with PCa following radical prostatectomy.

Dataset Information

The splicing-factor oncoprotein SF2/ASF activates mTORC1.

Publications

The splicing-factor oncoprotein SF2/ASF activates mTORC1.

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