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Pancreatic tumor suppression by benzyl isothiocyanate is associated with inhibition of PI3K/AKT/FOXO pathway.

ABSTRACT: Our previous studies have shown that benzyl isothiocyanate (BITC) suppress pancreatic cancer growth by inducing apoptosis but the molecular mechanism was unclear. In this study we hypothesized the involvement of PI3K/AKT/FOXO pathway in BITC-induced apoptosis.Mice were implanted BxPC-3 tumor xenografts and orally gavaged with 12 ?mol BITC. Plasma and tumor BITC concentration was estimated by liquid chromatography/tandem mass spectrometry. BxPC-3 and PanC-1 cells were used to elucidate PI3K/AKT/FOXO pathway. Electrophoretic mobility shift assay (EMSA), DNA binding activity, immunofluorescence, and gene transfection were used to delineate the mechanism.BITC-treated mice showed 43% less tumor growth as compared with control mice and correlated well with the therapeutic concentrations of 6.5 ?mol/L BITC achieved in plasma and 7.5 ?mol/g BITC in tumor tissue. Western blot analyses and immunohistochemistry revealed that tumors from BITC-treated mice showed reduced phosphorylation of PI3K, AKT, PDK1, mTOR, FOXO1, and FOXO3a and increased apoptosis. Complementing our in vivo results, we made similar observations in a dose- and time-dependent manner in BITC-treated BxPC-3 and Panc-1 cells. Binding of FOXO1 with 14-3-3 proteins was also reduced drastically by BITC treatment indicating nuclear retention of FOXO1 and this observation was further confirmed with EMSA, immunofluorescence, DNA binding, and upregulation of FOXO-responsive proteins Bim, p27, and p21 in BxPC-3 cells. Overexpression of AKT by transient transfection significantly blocked the modulation of FOXO proteins and protected the cells from BITC-mediated apoptosis and growth suppression.Our results provide convincing evidence on the involvement of PI3K/AKT/FOXO pathway in BITC-mediated pancreatic tumor growth suppression.

SUBMITTER: Boreddy SR

PROVIDER: S-EPMC3076680 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Pancreatic tumor suppression by benzyl isothiocyanate is associated with inhibition of PI3K/AKT/FOXO pathway.

Boreddy Srinivas Reddy SR Pramanik Kartick C KC Srivastava Sanjay K SK

Clinical cancer research : an official journal of the American Association for Cancer Research 20110224 7

<h4>Purpose</h4>Our previous studies have shown that benzyl isothiocyanate (BITC) suppress pancreatic cancer growth by inducing apoptosis but the molecular mechanism was unclear. In this study we hypothesized the involvement of PI3K/AKT/FOXO pathway in BITC-induced apoptosis.<h4>Experimental design</h4>Mice were implanted BxPC-3 tumor xenografts and orally gavaged with 12 μmol BITC. Plasma and tumor BITC concentration was estimated by liquid chromatography/tandem mass spectrometry. BxPC-3 and Pa ...[more]

PMID: 21350002

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Project description:The early diagnosis and treatment of liver hepatocellular carcinoma (LIHC) remains a major challenge. Therefore, it is of great significance to strengthen basic research on LIHC in order to improve the prevention and treatment of the disease. Numerous studies have indicated that the PI3K/Akt and FoxO signaling pathways mediate proliferation, survival and migration during the development of LIHC. Therefore, they have become a target for LIHC treatment. Furthermore, let-7c has been demonstrated to repress cell proliferation, migration and invasion, and to induce G1 phase arrest and apoptosis of LIHC cells. However, the mechanism of its action is not clear. In the present study, the association between let-7c and the PI3K/Akt/FoxO signaling pathway, as well as their roles in the development of LIHC were investigated using The Cancer Genome Atlas and various public databases (Tumor-miRNA-Pathway, OncomiR, DIANA-TarBase v8, KOBAS 3.0, ONCOMINE, Kaplan-Meier plotter, LinkedOmics, UALCAN and cBioPortal). The effects of let-7c-5p on PI3K/Akt/FoxO signaling pathway-related target genes were analyzed following overexpression of let-7c-5p in the MHCC-97H cell line via reverse transcription-quantitative PCR, and the let-7c-5p target genes belonging to the PI3K/Akt/FOXO signaling pathway in LIHC were screened out. GO and KEGG enrichment analyses of these target genes was performed using g:Profiler, gOST. In addition, GeneMANIA and Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) databases were used to determine the gene-gene and protein-protein interaction networks, respectively. The data demonstrated that cyclin B2 (CCNB2), cyclin E2 (CCNE2), cyclin dependent kinase 4 (CDK4), homer scaffold protein 1 (HOMER1), heat shock protein 90 α family class A member 1 (HSP90AA1), neuroblastoma RAS viral oncogene homolog (NRAS), protein phosphatase 2 catalytic subunit α (PPP2CA), protein kinase AMP-activated catalytic subunit α2 (PRKAA2) and Rac family small GTPase 1 (RAC1) may be target genes of let-7c-5p. These genes, particularly CCNE2, were associated with poor overall survival and could be promising candidate biomarkers for disease and poor prognosis in LIHC. Among them, seven genes (CCNE2, CDK4, HSP90AA1, NRAS, PPP2CA, PRKAA2 and RAC1) belonged to the PI3K-Akt signaling pathway and four genes (CCNB2, HOMER1, NRAS and PRKAA2) belonged to the FoxO signaling pathway. The majority of these genes were closely associated with the cell cycle and their elevated expression may aggravate cell cycle disorders. Therefore, let-7c may be considered to be an anti-oncogene of LIHC. The present study may provide novel targets and strategies for the diagnosis and treatment of LIHC.

Project description:Background:Transcription factor 7-like 2 (TCF7L2), which previously known as TCF-4, is a major form of transcription factor involved in the downstream WNT signaling and exhibits the strongest association to diabetes susceptibility. Although we still do not know mechanistically how TCF7L2 exerts its physiological functions on pancreatic endocrine cells, it had been suggested that TCF7L2 may directly affect ?-cell function by regulating the activation of PI3K/AKT signaling pathway. Methods:MIN6 cells were transfected with TCF7L2 knockdown virus or lenti-TCF7L2 virus for 48 h to evaluate the contribution of TCF7L2 to the PI3K/AKT signaling pathway and pancreatic ?-cell function. This was confirmed by measuring the expression of PI3K p85 and p-Akt by western blotting and insulin secretion by enzyme-linked immunosorbent assay (ELISA), respectively. Chromatin immunoprecipitation (ChIP) and polymerase chain reaction (PCR) experiments were performed to explore the genomic distribution of TCF7L2-binding sites in the promoter of PIK3R1, the affinity between which was analyzed by the luciferase reporter assay. Results:In the present study, we strikingly identified that TCF7L2 could profoundly inhibit the expression of PIK3R1 gene and its encoding protein PI3K p85, which then could lead to the activation of PI3K/AKT signaling and stimulate insulin secretion in pancreatic ?-cells. However, the integrity and stability of evolutionarily conserved TCF7L2-binding motif plays a very crucial role in the binding events between transcription factor TCF7L2 and its candidate target genes. We also found that the affinity of TCF7L2 to the promoter region of PIK3R1 alters upon the specific binding sites, which further provides statistical validation to the necessity of TCF7L2-binding motif. Conclusions:This study demonstrated that TCF7L2 is closely bound to the specific binding regions of PIK3R1 promoter and prominently controls the transcription of its encoding protein p85, which further affects the activation of PI3K/AKT signaling pathway and insulin secretion.

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Pancreatic tumor suppression by benzyl isothiocyanate is associated with inhibition of PI3K/AKT/FOXO pathway.

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Pancreatic tumor suppression by benzyl isothiocyanate is associated with inhibition of PI3K/AKT/FOXO pathway.

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