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RasGRP3 contributes to formation and maintenance of the prostate cancer phenotype.

ABSTRACT: RasGRP3 mediates the activation of the Ras signaling pathway that is present in many human cancers. Here, we explored the involvement of RasGRP3 in the formation and maintenance of the prostate cancer phenotype. RasGRP3 expression was elevated in multiple human prostate tumor tissue samples and in the human androgen-independent prostate cancer cell lines PC-3 and DU 145 compared with the androgen-dependent prostate cancer cell line LNCaP. Downregulation of endogenous RasGRP3 in PC-3 and DU 145 cells reduced Ras-GTP formation, inhibited cell proliferation, impeded cell migration, and induced apoptosis. Anchorage-independent growth of the PC-3 cells and tumor formation in mouse xenografts of both cell lines were likewise inhibited. Inhibition of RasGRP3 expression reduced AKT and extracellular signal-regulated kinase 1/2 phosphorylation and sensitized the cells to killing by carboplatin. Conversely, exogenous RasGRP3 elevated Ras-GTP, stimulated proliferation, and provided resistance to phorbol 12-myristate 13-acetate-induced apoptosis in LNCaP cells. RasGRP3-overexpressing LNCaP cells displayed a markedly enhanced rate of xenograft tumor formation in both male and female mice compared with the parental line. Suppression of RasGRP3 expression in these cells inhibited downstream RasGRP3 responses, caused the cells to resume the LNCaP morphology, and suppressed growth, confirming the functional role of RasGRP3 in the altered behavior of these cells. We conclude that RasGRP3 contributes to the malignant phenotype of the prostate cancer cells and may constitute a novel therapeutic target for human prostate cancer.

SUBMITTER: Yang D

PROVIDER: S-EPMC2955810 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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RasGRP3 contributes to formation and maintenance of the prostate cancer phenotype.

Yang Dazhi D Kedei Noemi N Li Luowei L Tao Juan J Velasquez Julia F JF Michalowski Aleksandra M AM Tóth Balázs I BI Marincsák Rita R Varga Attila A Bíró Tamás T Yuspa Stuart H SH Blumberg Peter M PM

Cancer research 20100928 20

RasGRP3 mediates the activation of the Ras signaling pathway that is present in many human cancers. Here, we explored the involvement of RasGRP3 in the formation and maintenance of the prostate cancer phenotype. RasGRP3 expression was elevated in multiple human prostate tumor tissue samples and in the human androgen-independent prostate cancer cell lines PC-3 and DU 145 compared with the androgen-dependent prostate cancer cell line LNCaP. Downregulation of endogenous RasGRP3 in PC-3 and DU 145 c ...[more]

PMID: 20876802

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Project description:IntroductionRas guanine nucleotide exchange factors (RasGEFs) mediate the activation of the Ras signaling pathway that is over activated in many human cancers. The RasGRP3, an activator of H-Ras and R-Ras protein exerts oncogenic effects and the overexpression of the protein is observed in numerous malignant cancer types. Here, we investigated the putative alteration of expression and potential function of RasGRP3 in the formation and progression of human breast cancer.MethodsThe RasGRP3 and phosphoRasGRP3 expressions were examined in human invasive ductal adenocarcinoma derived samples and cell lines (BT-474, JIMT-1, MCF7, SK-BR-3, MDA-MB-453, T-47D) both in mRNA (Q-PCR) and protein (Western blot; immunohistochemistry) levels. To explore the biological function of the protein, RasGRP3 knockdown cultures were established. To assess the role of RasGRP3 in the viability of cells, annexin-V/PI staining and MitoProbe™ DilC1 (5) assay were performed. To clarify the function of the protein in cell proliferation and in the development of chemotherapeutic resistance, CyQuant assay was performed. To observe the RasGRP3 function in tumor formation, the Severe combined immunodeficiency (SCID) mouse model was used. To investigate the role of the protein in Ras-related signaling Q-PCR and Western blot experiments were performed.ResultsRasGRP3 expression was elevated in human breast tumor tissue samples as well as in multiple human breast cancer cell lines. Down-regulation of RasGRP3 expression in breast cancer cells decreased cell proliferation, induced apoptosis in MCF7 cells, and sensitized T-47D cells to the action of drugs Tamoxifen and trastuzumab (Herceptin). Gene silencing of RasGRP3 reduced tumor formation in mouse xenografts as well. Inhibition of RasGRP3 expression also reduced Akt, ERK1/2 and estrogen receptor alpha phosphorylation downstream from IGF-I insulin like growth factor-I (IGF-I) or epidermal growth factor (EGF) stimulation confirming the functional role of RasGRP3 in the altered behavior of these cells.ConclusionsTaken together, our results suggest that the Ras activator RasGRP3 may have a role in the pathological behavior of breast cancer cells and may constitute a therapeutic target for human breast cancer.

Project description:BackgroundThis study was undertaken to investigate the expression of guanyl nucleotide-releasing protein for Ras 3 (RasGRP3) in the cell lines and tissues in BPH and prostate cancer (PCa), as well as its associations with cancer invasion and prognosis in prostate carcinomas.MethodsExpression analysis of RasGRP3 was accomplished using immunohistochemical staining of PCa and BPH tissues. Pearson's χ2 test was used to analyze the association between RasGRP3 expression and specific clinical parameters. Survival and PSA relapse curves were evaluated using the Kaplan-Meier curves and log-rank tests, and the differences were assessed using the Cox regression methods. In addition, human PCa cell lines PC-3, DU145, LNCaP, PC3M-1E8, PC3M-2B4 and BPH-1 were examined for expression of RasGRP3 using western blot and quantitative polymerase chain reaction (Q-PCR) analysis. After PC-3 cells were transfected by small interfering RNA targeting RasGRP3, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and migratory assays were employed to determine the vitality and aggressive capability of tumor cell in vitro.ResultsExpression of RasGRP3 was significantly correlated (P=0.038 and P=0.021) with Gleason score (< or =6 versus > or =7) and T stage (T1-T2 versus T3-T4), respectively. PCa with RasGRP3-positive expression may increase the risk of PSA recurrence and decrease cancer-specific survival (P=0.0291 and P=0.0044). The expression of RasGRP3 was also associated with PSA recurrence and cancer-specific survival in univariate (P<0.001 and P<0.001) and multivariate analyses (P<0.001 and P=0.003). RasGRP3 mRNA and proteins were found to be positively expressed in PCa cell lines. There was higher expression of RasGRP3 in PC-3, DU145 and PC3M-1E8 than in LNCaP, PC3M-2B4 and BPH-1. Knockdown of RasGRP3 inhibited the proliferation, migration and invasion capabilities of PC-3 cells.ConclusionsThese data suggested that elevated RasGRP3 expression may play a key role in the malignant progression of PCa, especially in invasion and metastasis, and may be a potential marker of biochemical recurrence.

Project description:BackgroundDysfunction of microRNAs (miRNAs) is a major cause of aberrant expression of inflammatory cytokines and contributes to macrophage polarization. Proinflammatory M1 macrophages promote T helper (Th) 1 responses and show tumoricidal activity, whereas M2 macrophages display regulatory functions in tissue repair and remodeling and promote Th2 immune responses. Previous studies have shown that miRNA let-7 is associated with cellular differentiation and that the expression of let-7b-5p is significantly augmented in M2 macrophages. However, the mechanism by which let-7b-5p regulates macrophage differentiation in prostate cancer (PCa) remains largely unknown.MethodsHuman macrophages were induced by blood monocytes from healthy male donors, and M1 macrophages were polarized by stimulating them overnight with 100 ng/ml of lipopolysaccharides and 100 ng/ml of IFN-γ. Conditioned medium from PC-3 cells was used to induce prostatic macrophages (M-CMs) in vitro, and we then transfected let-7b-5p mimics or inhibitors into M1 and M-CMs for 72 h. The expression of cluster of differentiation 206 (CD206) in each group was detected with the High-Throughput Connotation of Imaging System. We used quantitative real-time polymerase chain reaction (qRT-PCR) to examine the expression of the inflammatory cytokines IL-10, IL-12, IL-13, TNF-alpha, and let-7b in macrophages. SOCS1 protein levels were evaluated by ELISA, and the phosphorylation difference in STAT family member proteins was analyzed using CST signal-pathway chip. Phagocytosis by macrophages and the effect of macrophages on the proliferation of prostate cancer PC-3 cells were evaluated with phagocytosis assay or the Cell Counting Kit-8 (CCK-8) and colony formation assay. The relationship between SOCS1 and let-7b-5p was confirmed with a dual-luciferase reporter.ResultsThe expression of cluster of differentiation 206 (CD206, a M2-like macrophage surface molecule) was significantly increased in M1 macrophages treated with let-7b-5p mimics, while CD206 expression was decreased in M-CMs treated with let-7b-5p inhibitors. Overexpression or knockdown of let-7b-5p significantly affected the expression of inflammatory factors in macrophages-including interleukin 10 (IL-10), IL-12, IL-13, and tumor necrosis factor alpha. Let-7b-5p downregulated the expression of suppressor of cytokine signaling 1 (SOCS1) and increased the phosphorylation of signal transducer and activator of transcription 1 (STAT1), STAT3, and STAT5a proteins in M-CMs and M1 macrophages with let-7b-5p mimics relative to the other groups. In addition, with the elevated expression of let-7b-5p, the phagocytosis by macrophages showed a commensurate and significant decrease. As a result, M-CMs treated with let-7b-5p inhibitors reduced the proliferation of PC-3 PCa cells.ConclusionsCollectively, these data indicated that let-7b-5p may regulate M2 polarization through the SOCS1/STAT pathway and that reversal of M2 differentiation by let-7b-5p inhibitors enhanced macrophage phagocytosis, ultimately inhibiting the proliferation of PCa cells.

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RasGRP3 contributes to formation and maintenance of the prostate cancer phenotype.

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RasGRP3 contributes to formation and maintenance of the prostate cancer phenotype.

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