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BRAF activation initiates but does not maintain invasive prostate adenocarcinoma.

ABSTRACT: Prostate cancer is the second leading cause of cancer-related deaths in men. Activation of MAP kinase signaling pathway has been implicated in advanced and androgen-independent prostate cancers, although formal genetic proof has been lacking. In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF(V600E)--a mutation found in approximately 10% of human prostate tumors--was targeted to the epithelial compartment of the prostate gland on the background of Ink4a/Arf deficiency. These GEM mice developed prostate gland hyperplasia with progression to rapidly growing invasive adenocarcinoma without evidence of AKT activation, providing genetic proof that activation of MAP kinase signaling is sufficient to drive prostate tumorigenesis. Importantly, genetic extinction of BRAF(V600E) in established prostate tumors did not lead to tumor regression, indicating that while sufficient to initiate development of invasive prostate adenocarcinoma, BRAF(V600E) is not required for its maintenance.

SUBMITTER: Jeong JH

PROVIDER: S-EPMC2597248 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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BRAF activation initiates but does not maintain invasive prostate adenocarcinoma.

Jeong Joseph H JH Wang Zhenxiong Z Guimaraes Alexander S AS Ouyang Xuesong X Figueiredo Jose L JL Ding Zhihu Z Jiang Shan S Guney Isil I Kang Gyeong Hoon GH Shin Eyoung E Hahn William C WC Loda Massimo F MF Abate-Shen Cory C Weissleder Ralph R Chin Lynda L

PloS one 20081216 12

Prostate cancer is the second leading cause of cancer-related deaths in men. Activation of MAP kinase signaling pathway has been implicated in advanced and androgen-independent prostate cancers, although formal genetic proof has been lacking. In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF(V600E)--a mutation found in approximately 1 ...[more]

PMID: 19079609

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Project description:The MaxiK potassium channel is regulated by voltage and intracellular calcium, and plays a critical role in regulating intracellular calcium concentration ([Ca(2+) ](i)), which is the ultimate determinant of smooth muscle tone. Tight control of corpus cavernosum smooth muscle (CCSM) tone is critically important and misregulation can result in erectile dysfunction.Because of the tight functional linkage of MaxiK and calcium channel activity, the aim of this study was to determine the effects of silencing and pharmacological inhibition of MaxiK on calcium homeostasis and intercellular calcium signaling in CCSM cells.We compared changes in the basal intracellular [Ca(2+) ](i) and parameters defining intercellular calcium wave (ICW) spread in 48 hours MaxiK silenced CCSM cells vs. acute blockade of the channel with iberiotoxin. To analyze changes occurring in gene expression we performed micro-array analysis following MaxiK silencing for 48 hours.Changes in Fura-2 fluorescence intensities were measured to evaluate basal [Ca(2+) ](i) levels and ICW parameters. Microarray analysis of global gene expression was performed.Forty-eight hours after MaxiK silencing the basal [Ca(2+) ](i) , the ICW amplitude and spread among CCSM cells were not markedly different in silenced compared to mock transfected controls, whereas short-term blockade significantly increased basal [Ca(2+) ](i) level and amplified Ca(2+) signaling among CCSM cells. Micro-array analysis showed that several genes within Ca(2+) homeostasis and smooth muscle tone regulation pathways had significantly altered expression.Our results indicate that while short-term blockade of the MaxiK channel is associated with an increase in basal [Ca(2+) ](i), Ca(2+) homeostasis is restored during the 48 hours period following silencing. We hypothesize that the different pathways regulating [Ca(2+) ](i) and CCSM tone are linked through molecular crosstalk and that their coordinated regulation is part of a compensatory mechanism aimed to maintain Ca(2+) homeostasis and CCSM tone.

Project description:BackgroundBRAF is a critical member of proliferation pathways in cancer, and a mutation is present in only 2-4% of lung adenocarcinomas (LADC). There is no data available on the expression pattern of BRAF RNA that might result in enhanced signalling and drug resistance.MethodsLADC tissue samples (n=64) were fixed and processed into paraffin blocks. Tissue microarrays (TMA) were constructed, and RNAScope® in situ hybridization (ISH) assay was performed for wild-type (WT) BRAF RNA. Apart from pathological assessment of tumor samples (grade, necrosis, vascular involvement and peritumoral infiltration), anti-programmed death ligand 1 (PD-L1) and anti-programmed death 1 (PD-1) immunohistochemistry and validation in public databases [The Cancer Genome Atlas (TCGA), Human Protein Atlas (HPA)] were carried out.ResultsWT BRAF RNA is expressed in LADC, with no significant expressional difference between early-stage (I-II) and advanced-stage (III-IV) patients (P=0.317). Never smokers exhibited significantly increased BRAF expression (compared to current and ex-smokers, P<0.01) and tumor necrosis correlated significantly with BRAF expression (P=0.014). PD-L1 expression was assessed on tumor cells and immune cells, PD-1 expression was evaluated on immune cells. There was no significant difference in BRAF RNA expression between tumor cell PD-L1-high vs. low patients (P=0.124), but it was decreased in immune cell PD-L1-high patients (P=0.03). Kaplan-Meier survival analysis showed that high BRAF expression was associated with significantly decreased OS (P<0.01) and was an independent negative prognostic factor according to multivariate Cox hazard regression (P=0.024). TCGA validation cohort confirmed our findings regarding OS in early-stage patients (P=0.034).ConclusionsWe found an increased expression of BRAF RNA in all stages in LADC. High BRAF expression was associated with tumor necrosis, distinct immune checkpoint biology and outcomes. We recommend further evaluating the potential of targeting overexpressed BRAF pathways in LADC.

Dataset Information

BRAF activation initiates but does not maintain invasive prostate adenocarcinoma.

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BRAF activation initiates but does not maintain invasive prostate adenocarcinoma.

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