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microRNA-21 governs TORC1 activation in renal cancer cell proliferation and invasion.

Dey N, Das F, Ghosh-Choudhury N, Mandal CC, Parekh DJ, Block K, Kasinath BS, Abboud HE, Choudhury GG - PLoS ONE (2012)

Bottom Line: Metastatic renal cancer manifests multiple signatures of gene expression.Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation.Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.

ABSTRACT
Metastatic renal cancer manifests multiple signatures of gene expression. Deviation in expression of mature miRNAs has been linked to human cancers. Importance of miR-21 in renal cell carcinomas is proposed from profiling studies using tumor tissue samples. However, the role of miR-21 function in causing renal cancer cell proliferation and invasion has not yet been shown. Using cultured renal carcinoma cells, we demonstrate enhanced expression of mature miR-21 along with pre-and pri-miR-21 by increased transcription compared to normal proximal tubular epithelial cells. Overexpression of miR-21 Sponge to quench endogenous miR-21 levels inhibited proliferation, migration and invasion of renal cancer cells. In the absence of mutation in the PTEN tumor suppressor gene, PTEN protein levels are frequently downregulated in renal cancer. We show that miR-21 targets PTEN mRNA 3'untranslated region to decrease PTEN protein expression and augments Akt phosphorylation in renal cancer cells. Downregulation of PTEN as well as overexpression of constitutively active Akt kinase prevented miR-21 Sponge-induced inhibition of renal cancer cell proliferation and migration. Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation. Finally, we demonstrate that expression of constitutively active TORC1 attenuated miR-21 Sponge-mediated suppression of proliferation and migration of renal cancer cells. Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

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Expression of PTEN in HK2 and ACHN cells.(A) The lysates of cells from three independent wells of HK2 and ACHN cells were immunoblotted with PTEN and actin antibodies. (B) The same cell lysates were immunoblotted with phospho-Akt (Thr-308), phospho-Akt (Ser-473) and Akt antibodies.
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pone-0037366-g003: Expression of PTEN in HK2 and ACHN cells.(A) The lysates of cells from three independent wells of HK2 and ACHN cells were immunoblotted with PTEN and actin antibodies. (B) The same cell lysates were immunoblotted with phospho-Akt (Thr-308), phospho-Akt (Ser-473) and Akt antibodies.

Mentions: Mutation in PTEN tumor suppressor gene or its reduced expression contribute to tumorigenesis and metastasis of many cancers [27], [28]. However, PTEN mutation is not frequently found in renal cell carcinoma [29]. PTEN has been validated to be a target of miR-21 [30]. We investigated the levels of PTEN in ACHN renal cancer cells. As shown in Fig. 3A, the abundance of PTEN in ACHN was significantly reduced as compared to that in HK2 cells. Identical results were obtained in Caki-2 renal carcinoma cell line (Fig. S5A). PTEN reduces the levels of PIP3, which controls the phosphorylation/activation of Akt [27], [31], [32]. Reduced PTEN levels in ACHN and Caki-2 cells were associated with increased phosphorylation of Akt at Thr-308 and Ser-473 (Fig. 3B and Fig. S5B), indicating its activation [32].


microRNA-21 governs TORC1 activation in renal cancer cell proliferation and invasion.

Dey N, Das F, Ghosh-Choudhury N, Mandal CC, Parekh DJ, Block K, Kasinath BS, Abboud HE, Choudhury GG - PLoS ONE (2012)

Expression of PTEN in HK2 and ACHN cells.(A) The lysates of cells from three independent wells of HK2 and ACHN cells were immunoblotted with PTEN and actin antibodies. (B) The same cell lysates were immunoblotted with phospho-Akt (Thr-308), phospho-Akt (Ser-473) and Akt antibodies.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368259&req=5

pone-0037366-g003: Expression of PTEN in HK2 and ACHN cells.(A) The lysates of cells from three independent wells of HK2 and ACHN cells were immunoblotted with PTEN and actin antibodies. (B) The same cell lysates were immunoblotted with phospho-Akt (Thr-308), phospho-Akt (Ser-473) and Akt antibodies.
Mentions: Mutation in PTEN tumor suppressor gene or its reduced expression contribute to tumorigenesis and metastasis of many cancers [27], [28]. However, PTEN mutation is not frequently found in renal cell carcinoma [29]. PTEN has been validated to be a target of miR-21 [30]. We investigated the levels of PTEN in ACHN renal cancer cells. As shown in Fig. 3A, the abundance of PTEN in ACHN was significantly reduced as compared to that in HK2 cells. Identical results were obtained in Caki-2 renal carcinoma cell line (Fig. S5A). PTEN reduces the levels of PIP3, which controls the phosphorylation/activation of Akt [27], [31], [32]. Reduced PTEN levels in ACHN and Caki-2 cells were associated with increased phosphorylation of Akt at Thr-308 and Ser-473 (Fig. 3B and Fig. S5B), indicating its activation [32].

Bottom Line: Metastatic renal cancer manifests multiple signatures of gene expression.Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation.Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.

ABSTRACT
Metastatic renal cancer manifests multiple signatures of gene expression. Deviation in expression of mature miRNAs has been linked to human cancers. Importance of miR-21 in renal cell carcinomas is proposed from profiling studies using tumor tissue samples. However, the role of miR-21 function in causing renal cancer cell proliferation and invasion has not yet been shown. Using cultured renal carcinoma cells, we demonstrate enhanced expression of mature miR-21 along with pre-and pri-miR-21 by increased transcription compared to normal proximal tubular epithelial cells. Overexpression of miR-21 Sponge to quench endogenous miR-21 levels inhibited proliferation, migration and invasion of renal cancer cells. In the absence of mutation in the PTEN tumor suppressor gene, PTEN protein levels are frequently downregulated in renal cancer. We show that miR-21 targets PTEN mRNA 3'untranslated region to decrease PTEN protein expression and augments Akt phosphorylation in renal cancer cells. Downregulation of PTEN as well as overexpression of constitutively active Akt kinase prevented miR-21 Sponge-induced inhibition of renal cancer cell proliferation and migration. Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation. Finally, we demonstrate that expression of constitutively active TORC1 attenuated miR-21 Sponge-mediated suppression of proliferation and migration of renal cancer cells. Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

Show MeSH
Related in: MedlinePlus