Molecular Characterization of Lung Dysplasia Induced by c-Raf-1

Rohrbeck, Astrid; Müller, Volker; Borlak, Jürgen

doi:10.1371/journal.pone.0005637

Cited by 18 publications

(29 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, increased C-Raf expression has been documented in acute myeloid leukemia (AML) [45], primitive neuroectodermal tumors (PNETs) [46], non-small cell lung cancer (NSCLC) [47], ovarian cancer [48], thyroid [49] and gliomas [49]. In addition, though early studies asserted that overexpression of wildtype C-Raf or MEK are not tumorigenic, more recent work indicates that targeted overexpression of wildtype C-Raf in the lung could lead to lung cancer [50–54], suggesting that overexpression of wildtype C-Raf is sufficient for inducing cellular transformation. Our findings are of special significance since they imply that mutations along the pathway may not be necessary for constitutive pathway activation, but rather co-overexpression of C-Raf with MEK could suffice.…”

Section: Discussionmentioning

confidence: 99%

MEK-1 activates C-Raf through a Ras-independent mechanism

Leicht

Balan

Zhu

et al. 2013

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

View full text Add to dashboard Cite

C-Raf is a member of the Ras-Raf-MEK-ERK mitogen-activated protein kinase (MAPK) signaling pathway that plays key roles in diverse physiological processes and is upregulated in many human cancers. C-Raf activation involves binding to Ras, increased phosphorylation and interactions with co-factors. Here, we describe a Ras-independent in vivo pathway for C-Raf activation by its downstream target MEK. Using 32P-metabolic labeling and 2D-phosphopeptide mapping experiments, we show that MEK increases C-Raf phosphorylation by up-to 10-fold. This increase was associated with C-Raf kinase activation, matching the activity seen with growth factor stimulation. Consequently, coexpression of wildtype C-Raf and MEK was sufficient for full and constitutive activation of ERK. Notably, the ability of MEK to activate C-Raf was completely Ras independent, since mutants impaired in Ras binding that are irresponsive to growth factors or Ras were fully activated by MEK. The ability of MEK to activate C-Raf was only partially dependent on MEK kinase activity but required MEK binding to C-Raf, suggesting that the binding results in a conformational change that increases C-Raf susceptibility to phosphorylation and activation or in the stabilization of the phosphorylated-active form. These findings propose a novel Ras-independent mechanism for activating C-Raf and the MAPK pathway without the need for mutations in the pathway. This mechanism could be of significance in pathological conditions or cancers overexpressing C-Raf and MEK or in conditions where C-Raf-MEK interaction is enhanced due to the downregulation of RKIP and MST2.

show abstract

Section: Discussionmentioning

confidence: 99%

MEK-1 activates C-Raf through a Ras-independent mechanism

Leicht

Balan

Zhu

et al. 2013

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

View full text Add to dashboard Cite

show abstract

“…Mouse 430 2.0 microarray chip from Affymetrix was used to perform 3′IVT array according to manufacturer’s instruction and protocol as per discussed in detail in our previous publications [16], [17].…”

Section: Methodsmentioning

confidence: 99%

A Cross-Platform Comparison of Genome-Wide Expression Changes of Laser Microdissected Lung Tissue of C-Raf Transgenic Mice Using 3′IVT and Exon Array

Londhe

Borlak

2012

PLoS ONE

View full text Add to dashboard Cite

Microarrays are widely used to study genome-wide gene expression changes in different conditions most notably disease, growth, or to investigate the effects of drugs on entire genomes. While the number and gene probe sequences to investigate individual gene expression changes differs amongst manufactures, the design for all of the probes is biased towards the 3′ region. With the advent of exon arrays, transcripts of any known or predicted exon can be investigated to facilitate the study of genome-wide alternative splicing events. Thus, the use of exon arrays provides unprecedented opportunities in gene expression studies. However, it remains a major challenge to directly compare gene expression data derived from oligonucleotide to exon arrays. In the present study, genome-wide expression profiling of Laser Micro-dissected Pressure Catapulted (LMPC) samples of c-Raf mouse lung adenocarcinoma, dysplasia, unaltered transgenic and non-transgenic tissues was performed using the Affymetrix GeneChip Mouse Genome 430 2.0 Array and whole genome Mouse Exon 1.0 ST Array. Based on individual group comparisons 52 to 83% of regulated genes were similar in direction, but fold changes of regulated genes disagreed when data amongst the two platforms were compared. Furthermore, for 27 regulated genes opposite direction of gene expression was observed when the two platforms were compared pointing to the need to assess alternative splicing events at the 3′ end. Taken collectively, exon arrays can be performed even with laser microdissected samples but fold change gene expression changes differ considerably between 3′IVT array and exon arrays with alternative splicing events contributing to apparent differences in gene expression changes.

show abstract

“…Lung samples in GSE13963 and GSE14277 were obtained using a transgenic mouse model where targeted expression of c-Raf in respiratory epithelium results in dysplasia and subsequent adenocarcinoma (41, 42). Dataset GSE13963 examines differences in dysplastic epithelium compared to normal epithelium and GSE14277 compares cancer cells to normal epithelium.…”

Section: Resultsmentioning

confidence: 99%

SIRT1 Pathway Dysregulation in the Smoke-Exposed Airway Epithelium and Lung Tumor Tissue

Beane

Cheng²,

Soldi³

et al. 2012

Cancer Research

View full text Add to dashboard Cite

Cigarette smoke produces a molecular “field of injury” in epithelial cells lining the respiratory tract. However, the specific signaling pathways that are altered in the airway of smokers and the signaling processes responsible for the transition from smoking-induced airway damage to lung cancer remain unknown. In this study, we use a genomic approach to study the signaling processes associated with tobacco smoke exposure and lung cancer. First, we developed and validated pathway-specific gene expression signatures in bronchial airway epithelium that reflect activation of signaling pathways relevant to tobacco-exposure including ATM, BCL2, GPX1, NOS2, IKBKB, and SIRT1. Using these profiles and four independent gene expression datasets, we found that SIRT1 activity is significantly up-regulated in cytologically normal bronchial airway epithelial cells from active smokers compared to non-smokers. In contrast, this activity is strikingly down-regulated in non-small cell lung cancer. This pattern of signaling modulation was unique to SIRT1, and down-regulation of SIRT1 activity is confined to tumors from smokers. Decreased activity of SIRT1 was validated using genomic analyses of mouse models of lung cancer and biochemical testing of SIRT1 activity in patient lung tumors. Together, our findings indicate a role of SIRT1 in response to smoke and a potential role in repressing lung cancer. Further, our findings suggest that the airway gene-expression signatures derived in this study can provide novel insights into signaling pathways altered in the “field of inury” induced by tobacco smoke and thus may impact strategies for prevention of tobacco-related lung cancer.

show abstract

Molecular Characterization of Lung Dysplasia Induced by c-Raf-1

Cited by 18 publications

References 66 publications

MEK-1 activates C-Raf through a Ras-independent mechanism

MEK-1 activates C-Raf through a Ras-independent mechanism

A Cross-Platform Comparison of Genome-Wide Expression Changes of Laser Microdissected Lung Tissue of C-Raf Transgenic Mice Using 3′IVT and Exon Array

SIRT1 Pathway Dysregulation in the Smoke-Exposed Airway Epithelium and Lung Tumor Tissue

Contact Info

Product

Resources

About