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A screen for transcription factor targets of glycogen synthase kinase-3 highlights an inverse correlation of NF?B and androgen receptor signaling in prostate cancer.

ABSTRACT: Expression of Glycogen Synthase Kinase-3 (GSK-3) is elevated in prostate cancer and its inhibition reduces prostate cancer cell proliferation, in part by reducing androgen receptor (AR) signaling. However, GSK-3 inhibition can also activate signals that promote cell proliferation and survival, which may preclude the use of GSK-3 inhibitors in the clinic. To identify such signals in prostate cancer, we screened for changes in transcription factor target DNA binding activity in GSK-3-silenced cells. Among the alterations was a reduction in AR DNA target binding, as predicted from previous studies, and an increase in NF?B DNA target binding. Consistent with the latter, gene silencing of GSK-3 or inhibition using the GSK-3 inhibitor CHIR99021 increased basal NF?B transcriptional activity. Activation of NF?B was accompanied by an increase in the level of the NF?B family member RelB. Conversely, silencing RelB reduced activation of NF?B by CHIR99021. Furthermore, the reduction of prostate cancer cell proliferation by CHIR99021 was potentiated by inhibition of NF?B signaling using the IKK inhibitor PS1145. Finally, stratification of human prostate tumor gene expression data for GSK3 revealed an inverse correlation between NF?B-dependent and androgen-dependent gene expression, consistent with the results from the transcription factor target DNA binding screen. In addition, there was a correlation between expression of androgen-repressed NF?B target genes and reduced survival of patients with metastatic prostate cancer. These findings highlight an association between GSK-3/AR and NF?B signaling and its potential clinical importance in metastatic prostate cancer.

SUBMITTER: Campa VM

PROVIDER: S-EPMC4226675 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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A screen for transcription factor targets of glycogen synthase kinase-3 highlights an inverse correlation of NFκB and androgen receptor signaling in prostate cancer.

Campa Victor M VM Baltziskueta Eder E Bengoa-Vergniory Nora N Gorroño-Etxebarria Irantzu I Wesołowski Radosław R Waxman Jonathan J Kypta Robert M RM

Oncotarget 20140901 18

Expression of Glycogen Synthase Kinase-3 (GSK-3) is elevated in prostate cancer and its inhibition reduces prostate cancer cell proliferation, in part by reducing androgen receptor (AR) signaling. However, GSK-3 inhibition can also activate signals that promote cell proliferation and survival, which may preclude the use of GSK-3 inhibitors in the clinic. To identify such signals in prostate cancer, we screened for changes in transcription factor target DNA binding activity in GSK-3-silenced cell ...[more]

PMID: 25327559

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Project description:Glycogen synthase kinase-3? (GSK-3?), a serine/threonine protein kinase, may function as a tumor suppressor or an oncogene, depending on the tumor type. We sought to determine the biological function of GSK-3? in osteosarcoma, a rare pediatric cancer for which the identification of new therapeutic targets is urgent.We used cell viability assays, colony formation assays, and apoptosis assays to analyze the effects of altered GSK-3? expression in U2OS, MG63, SAOS2, U2OS/MTX300, and ZOS osteosarcoma cell lines. Nude mice (n = 5-8 mice per group) were injected with U2OS/MTX300, and ZOS cells to assess the role of GSK-3? in osteosarcoma growth in vivo and to evaluate the effects of inhibitors and/or anticancer drugs on tumor growth. We used an antibody array, polymerase chain reaction, western blotting, and a luciferase reporter assay to establish the effect of GSK-3? inhibition on the nuclear factor-?B (NF-?B) pathway. Immunochemistry was performed on primary tumor specimens from osteosarcoma patients (n = 74) to determine the relationship of GSK-3? activity with overall survival.Osteosarcoma cells with low levels of inactive p-Ser9-GSK-3? formed colonies in vitro and tumors in vivo more readily than cells with higher levels and cells in which GSK-3? had been silenced formed fewer colonies and smaller tumors than parental cells. Silencing or pharmacological inhibition of GSK-3? resulted in apoptosis of osteosarcoma cells. Inhibition of GSK-3? resulted in inhibition of the NF-?B pathway and reduction of NF-?B-mediated transcription. Combination treatments with GSK-3? inhibitors, NF-?B inhibitors, and chemotherapy drugs increased the effectiveness of chemotherapy drugs in vitro and in vivo. Patients whose osteosarcoma specimens had hyperactive GSK-3?, and nuclear NF-?B had a shorter median overall survival time (49.2 months) compared with patients whose tumors had inactive GSK-3? and NF-?B (109.2 months).GSK-3? activity may promote osteosarcoma tumor growth, and therapeutic targeting of the GSK-3? and/or NF-?B pathways may be an effective way to enhance the therapeutic activity of anticancer drugs against osteosarcoma.

Project description:miRNAs are predicted to control the activity of approximately 60% of all protein-coding genes participating in the regulation of several cellular processes and diseases, including cancer. Recently, we have demonstrated that miR-187 is significantly downregulated in prostate cancer (PCa) and here we propose a proteomic approach to identify its potential targets. For this purpose, PC-3 cells were transiently transfected with miR-187 precursor and miRNA mimic negative control. Proteins were analyzed by a two-dimensional difference gel electrophoresis (2D-DIGE) and defined as differentially regulated if the observed fold change was ±1.06. Then, MALDI-TOF MS analysis was performed after protein digestion and low abundance proteins were identified by LC-MS/MS. Peptides were identified by searching against the Expasy SWISS PROT database, and target validation was performed both in vitro by western blot and qRT-PCR and in clinical samples by qRT-PCR, immunohistochemistry and ELISA. DIGE analysis showed 9 differentially expressed spots (p<0.05) and 7 showed a down-regulated expression upon miR-187 re-introduction. Among these targets we identified aldehyde dehydrogenase 1A3 (ALDH1A3). ALDH1A3 expression was significantly downregulated in PC3, LNCaP and DU-145 cells after miR-187 re-introduction. Supporting these data, the expression of ALDH1A3 was found significantly (p<0.0001) up-regulated in PCa samples and inversely correlated (p<0.0001) with miR-187 expression, its expression being directly associated with Gleason score (p = 0.05). The expression of ALDH1A3 was measured in urine samples to evaluate the predictive capability of this biomarker for the presence of PCa and, at a signification level of 10%, PSA and also ALDH1A3 were significantly associated with a positive biopsy of PCa. In conclusion, our data illustrate for the first time the role of ALDH1A3 as a miR-187 target in PCa and provide insights in the utility of using this protein as a new biomarker for PCa.

Dataset Information

A screen for transcription factor targets of glycogen synthase kinase-3 highlights an inverse correlation of NF?B and androgen receptor signaling in prostate cancer.

Publications

A screen for transcription factor targets of glycogen synthase kinase-3 highlights an inverse correlation of NFκB and androgen receptor signaling in prostate cancer.

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