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1.
Aberrant activation of MAP kinase signaling pathway and loss of tumor suppressor LKB1 have been implicated in lung cancer development and progression. Although oncogenic KRAS mutations are frequent, BRAF mutations (BRAFV600E) are found in 3% of human non-small cell lung cancers. Contrary to KRAS mutant tumors, BRAFV600E-induced tumors are benign adenomas that fail to progess. Interestingly, loss of tumor supressor LKB1 coexists with KRAS oncogenic mutations and synergizes in tumor formation and progression, however, its cooperation with BRAFV600E oncogene is unknown. Our results describe a lung cell population in neonates mice where expression of BRAFV600E leads to lung adenoma development. Importantly, expression of BRAFV600E concomitant with the loss of only a single-copy of Lkb1, overcomes senencence–like features of BRAFV600E-mutant adenomas leading malignization to carcinomas. These results posit LKB1 haploinsufficiency as a risk factor for tumor progression of BRAFV600E mutated lung adenomas in human cancer patients.  相似文献   

2.
Aberrant signaling of the Ras-Raf-MEK-ERK (MAP kinase) pathway driven by the mutant kinase BRAFV600E, as a result of the BRAFT1799A mutation, plays a fundamental role in thyroid tumorigenesis. This study investigated the therapeutic potential of a BRAFV600E-selective inhibitor, PLX4032 (RG7204), for thyroid cancer by examining its effects on the MAP kinase signaling and proliferation of 10 thyroid cancer cell lines with wild-type BRAF or BRAFT1799A mutation. We found that PLX4032 could effectively inhibit the MAP kinase signaling, as reflected by the suppression of ERK phosphorylation, in cells harboring the BRAFT1799A mutation. PLX4032 also showed a potent and BRAF mutation-selective inhibition of cell proliferation in a concentration-dependent manner. PLX4032 displayed low IC50 values (0.115–1.156 μM) in BRAFV600E mutant cells, in contrast with wild-type BRAF cells that showed resistance to the inhibitor with high IC50 values (56.674–1349.788 μM). Interestingly, cells with Ras mutations were also sensitive to PLX4032, albeit moderately. Thus, this study has confirmed that the BRAFT1799A mutation confers cancer cells sensitivity to PLX4032 and demonstrated its specific potential as an effective and BRAFT1799A mutation-selective therapeutic agent for thyroid cancer.  相似文献   

3.
4.
Although BRAFV600E is well known to play an important role in the tumorigenesis of melanoma, its molecular mechanism, particularly the epigenetic aspect, has been incompletely understood. Here, we investigated the role of BRAFV600E signaling in altering gene methylation in the genome of melanoma cells using a methylated CpG island amplification/CpG island microarray system and searched for genes coupled to the BRAFV600E signaling through methylation aberrations. The results indicated that a wide range of genes with broad functions were linked to BRAFV600E signaling through their hyper- or hypomethylation. Expression of 59 genes hypermethylated upon BRAF knockdown was selectively tested and found to be largely correspondingly underexpressed, suggesting that these genes were naturally hypomethylated and overexpressed with BRAFV600E in melanoma. This BRAFV600E-promoted hypomethylation was confirmed on genes selectively examined in primary melanoma tumors. Some of these genes were functionally tested and demonstrated to play a role in melanoma cell proliferation and invasion. As a mechanism of aberrant gene methylation driven by BRAFV600E, expression of the DNA methyltransferase 1 and histone methyltransferase EZH2 was profoundly affected by BRAFV600E. We have thus uncovered a previously unrecognized prominent epigenetic mechanism in the tumorigenesis of melanoma driven by BRAFV600E. Many of the functionally important genes controlled by the BRAFV600E signaling through aberrant methylation may prove to be novel therapeutic targets for melanoma.Key words: BRAF mutation, DNA methylation, melanoma, MAP kinase pathway, gene hypomethylation, gene hypermethylation  相似文献   

5.
6.
A CpG island methylator phenotype (CIMP) is displayed by a distinct subset of colorectal cancers with a high frequency of DNA hypermethylation in a specific group of CpG islands. Recent studies have shown that an activating mutation of BRAF (BRAFV600E) is tightly associated with CIMP, raising the question of whether BRAFV600E plays a causal role in the development of CIMP or whether CIMP provides a favorable environment for the acquisition of BRAFV600E. We employed Illumina GoldenGate DNA methylation technology, which interrogates 1,505 CpG sites in 807 different genes, to further study this association. We first examined whether expression of BRAFV600E causes DNA hypermethylation by stably expressing BRAFV600E in the CIMP-negative, BRAF wild-type COLO 320DM colorectal cancer cell line. We determined 100 CIMP-associated CpG sites and examined changes in DNA methylation in eight stably transfected clones over multiple passages. We found that BRAFV600E is not sufficient to induce CIMP in our system. Secondly, considering the alternative possibility, we identified genes whose DNA hypermethylation was closely linked to BRAFV600E and CIMP in 235 primary colorectal tumors. Interestingly, genes that showed the most significant link include those that mediate various signaling pathways implicated in colorectal tumorigenesis, such as BMP3 and BMP6 (BMP signaling), EPHA3, KIT, and FLT1 (receptor tyrosine kinases) and SMO (Hedgehog signaling). Furthermore, we identified CIMP-dependent DNA hypermethylation of IGFBP7, which has been shown to mediate BRAFV600E-induced cellular senescence and apoptosis. Promoter DNA hypermethylation of IGFBP7 was associated with silencing of the gene. CIMP-specific inactivation of BRAFV600E-induced senescence and apoptosis pathways by IGFBP7 DNA hypermethylation might create a favorable context for the acquisition of BRAFV600E in CIMP+ colorectal cancer. Our data will be useful for future investigations toward understanding CIMP in colorectal cancer and gaining insights into the role of aberrant DNA hypermethylation in colorectal tumorigenesis.  相似文献   

7.

Background

We evaluated the usefulness of follow-up BRAFV600E mutation analysis using ultrasonography-guided fine-needle aspiration (US-FNA) in diagnosis of thyroid nodules showing negative BRAFV600E mutation on prior analysis.

Methodology/Principal Finding

A total of 49 patients (men: 6, women: 43, mean age: 50.4 years) with 49 thyroid nodules were included. Patients had undergone initial and follow-up US-FNA and subsequent BRAFV600E mutation analysis from US-FNA aspirates. All patients had negative results on initial BRAFV600E mutation analysis. Clinicopathologic findings, US assessment, and BRAFV600E mutation results were analyzed according to the final pathology. Of the 49 nodules, 12 (24.5%) were malignant and 37 (75.5%) were benign. Seven (58.3%) of the 12 malignant nodules were positive for BRAFV600E mutation on follow-up, all showing suspicious US features. Initial US-FNA cytology of the 7 nodules were non-diagnostic (n = 2), benign (n = 2), or atypia (n = 3), while follow-up were benign (n = 1), indeterminate (n = 1), suspicious for malignancy (n = 4), and malignancy (n = 1).

Conclusions/Significance

Follow-up BRAFV600E mutation analysis may be helpful in the diagnosis of selected thyroid nodules negative for BRAFV600E mutation on initial analysis, which are assessed as suspicious malignant on US, diagnosed as non-diagnostic, benign or atypia on follow-up US-FNA.  相似文献   

8.
9.
Bisphenol A (BPA), a ubiquitous endocrine-disrupting chemical, alters the function of endocrine system and enhances the susceptibility to tumorigenesis in several hormone-dependent tumours as thyroid carcinoma. About 50% of papillary thyroid cancers (PTC), the most common type of thyroid malignancy, harbours the BRAFV600E mutation. This study aimed to investigate a potential combined effect of BPA exposure and BRAFV600E mutation on epithelial-mesenchymal transition (EMT) in PTC. Firstly, the level of BPA in plasma, the evaluation of BRAFV600E mutation and the level of EMT-related proteins in PTC samples were individually determined. Additionally, the migration, invasion, colony formation capacity and the expression of EMT-related proteins after exposure to BPA were precisely analysed in vitro thyroid cells genetically modified by the introduction of BRAFV600E mutation. Moreover, ERK-Cox2 signalling pathway was also introduced to explore the possible mechanism in PTC development. As expected, whether the clinical investigation or cultured thyroid cells demonstrated that BPA at a concentration compatible with human exposed levels (10-7 M) synergized with the BRAFV600E mutation promoted EMT via the activation of ERK-Cox2 signalling pathway. Our findings offer some evidence that BPA as an environmental risk factor can facilitate the progression of PTC harbouring BRAFV600E mutation.  相似文献   

10.
The BRAF gene is frequently mutated in cancer. The most common genetic mutation is a single nucleotide transition which gives rise to a constitutively active BRAF kinase (BRAFV600E) which in turn sustains continuous cell proliferation. The study of BRAFV600E murine models has been mainly focused on the role of BRAFV600E in tumor development but little is known on the early molecular impact of BRAFV600E expression in vivo. Here, we study the immediate effects of acute ubiquitous BRAFV600E activation in vivo. We find that BRAFV600E elicits a rapid DNA damage response in the liver, spleen, lungs but not in thyroids. This DNA damage response does not occur at telomeres and is accompanied by activation of the senescence marker p21CIP1 only in lungs but not in liver or spleen. Moreover, in lungs, BRAFV600E provokes an acute inflammatory state with a tissue-specific recruitment of neutrophils in the alveolar parenchyma and macrophages in bronchi/bronchioles, as well as bronchial/bronchiolar epithelium transdifferentiation and development of adenomas. Furthermore, whereas in non-tumor alveolar type II (ATIIs) pneumocytes, acute BRAFV600E induction elicits rapid p53-independent p21CIP1 activation, adenoma ATIIs express p53 without resulting in p21CIP1 gene activation. Conversely, albeit in Club cells BRAFV600E-mediated proliferative cue is more exacerbated compared to that occurring in ATIIs, such oncogenic stimulus culminates with p21CIP1-mediated cell cycle arrest and apoptosis. Our findings indicate that acute BRAFV600E expression drives an immediate induction of DNA damage response in vivo. More importantly, it also results in rapid differential responses of cell cycle and senescence-associated proteins in lung epithelia, thus revealing the early molecular changes emerging in BRAFV600E-challenged cells during tumorigenesis in vivo.Subject terms: Lung cancer, Senescence  相似文献   

11.
ERK1/2 signaling is frequently dysregulated in tumors through BRAF mutation. Targeting mutant BRAF with vemurafenib frequently elicits therapeutic responses; however, durable effects are often limited by ERK1/2 pathway reactivation via poorly defined mechanisms. We generated mutant BRAFV600E melanoma cells that exhibit resistance to PLX4720, the tool compound for vemurafenib, that co-expressed mutant (Q61K) NRAS. In these BRAFV600E/NRASQ61K co-expressing cells, re-activation of the ERK1/2 pathway during PLX4720 treatment was dependent on NRAS. Expression of mutant NRAS in parental BRAFV600 cells was sufficient to by-pass PLX4720 effects on ERK1/2 signaling, entry into S phase and susceptibility to apoptosis in a manner dependent on the RAF binding site in NRAS. ERK1/2 activation in BRAFV600E/NRASQ61K cells required CRAF only in the presence of PLX4720, indicating a switch in RAF isoform requirement. Both ERK1/2 activation and resistance to apoptosis of BRAFV600E/NRASQ61K cells in the presence of PLX4720 was modulated by SHOC-2/Sur-8 expression, a RAS-RAF scaffold protein. These data show that NRAS mutations confer resistance to RAF inhibitors in mutant BRAF cells and alter RAF isoform and scaffold molecule requirements to re-activate the ERK1/2 pathway.  相似文献   

12.

Objective

To evaluate the association of the BRAFV600E mutation with sonographic features and clinicopathologic characteristics in a large population with conventional papillary thyroid carcinoma (PTC).

Methods

We retrospectively reviewed the sonographic features, clinicopathologic characteristics, and presence of the BRAFV600E mutation in 688 patients who underwent thyroidectomy for conventional PTC between January and July 2010 at a single institution. The incidence of the BRAFV600E mutation was calculated. The sonographic features and clinicopathologic characteristics were compared between BRAF-positive and BRAF-negative patients. BRAF-positive patients were subdivided into those with papillary thyroid microcarcinoma (the PTMC group) and those with PTC larger than 10 mm (the PTC>10 mm group), and their sonographic features were compared.

Results

The BRAFV600E mutation was detected in 69.2% of patients (476 of 688). Sonographic features were not significantly different between BRAF-positive and BRAF-negative PTC, nor between PTMC and PTC>10 mm groups. The BRAFV600E mutation was associated with male sex (P = 0.028), large tumor size, extrathyroidal extension, central and lateral lymph node metastasis, and advanced tumor stage (P<0.0001).

Conclusion

The BRAFV600E mutation was significantly associated with several poor clinicopathologic characteristics, but was not associated with sonographic features, regardless of tumor size. We recommend that patients with a thyroid nodule with any suspicious sonographic feature undergo preoperative BRAFV600E testing for risk stratification and to guide the initial surgical approach in PTC.  相似文献   

13.
Melanoma is one of the most aggressive cancers and its incidence is increasing worldwide. So far there are no curable therapies especially after metastasis. Due to frequent mutations in members of the mitogen-activated protein kinase (MAPK) signaling pathway, this pathway is constitutively active in melanoma. It has been shown that the SONIC HEDGEHOG (SHH)-GLI and MAPK signaling pathway regulate cell growth in many tumors including melanoma and interact with each other in the regulation of cell proliferation and survival.Here we show that the SHH-GLI pathway is active in human melanoma cell lines as they express downstream target of this pathway GLI1. Expression of GLI1 was significantly higher in human primary melanoma tissues harboring BRAFV600E mutation than those with wild type BRAF. Pharmacologic inhibition of BRAFV600E in human melanoma cell lines resulted in decreased expression of GLI1 thus demonstrating interaction of SHH-GLI and MAPK pathways. Inhibition of SHH-GLI pathway by the novel small molecule inhibitor of smoothened NVP-LDE225 was followed by inhibition of cell growth and induction of apoptosis in human melanoma cell lines, interestingly with both BRAFV600E and BRAFWild Type status. NVP-LDE225 was potent in reducing cell proliferation and inducing tumor growth arrest in vitro and in vivo, respectively and these effects were superior to the natural compound cyclopamine.Finally, we conclude that inhibition of SHH-GLI signaling pathway in human melanoma by the specific smoothened inhibitor NVP-LDE225 could have potential therapeutic application in human melanoma even in the absence of BRAFV600E mutation and warrants further investigations.  相似文献   

14.
Papillary thyroid carcinoma (PTC) is the most common endocrine and thyroid malignancy. The urokinase plasminogen activator receptor (uPAR) plays an important role in cancer pathogenesis, including breakdown of the extracellular matrix, invasion and metastasis. Additionally, there is increasing evidence that uPAR also promotes tumorigenesis via the modulation of multiple signaling pathways. BRAFV600E, the most common initial genetic mutation in PTC, leads to ERK1/2 hyperphosphorylation, which has been shown in numerous cancers to induce uPAR. Treatment of the BRAFV600E-positive PTC cell line, BCPAP, with the MEK/ERK inhibitor U0126 reduced uPAR RNA levels by 90%. siRNA-mediated downregulation of uPAR in BCPAP cells resulted in greatly decreased activity in the focal adhesion kinase (FAK)/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. This phenomenon was concurrent with drastically reduced proliferation rates and decreased clonigenic survival, as well as demonstrated senescence-associated nuclear morphology and induction of β-galactosidase activity. uPAR-knockdown BCPAP cells also displayed greatly reduced migration and invasion rates, as well as a complete loss of the cells'' ability to augment their invasiveness following plasminogen supplementation. Taken together, these data provide new evidence of a novel role for uPAR induction (as a consequence of constitutive ERK1/2 activation) as a central component in PTC pathogenesis, and highlight the potential of uPAR as a therapeutic target.Key words: urokinase plasminogen activator receptor (uPAR), papillary thyroid carcinoma, invasion, migration, proliferation, senescence, FAK, PI3K, Akt  相似文献   

15.
The V600E BRAF kinase mutation, which activates the downstream MAPK signaling pathway, commonly occurs in about 8% of all human malignancies and about 50% of all melanomas. In this study, we employed virtual screening and chemical synthesis to identify a series of N-(thiophen-2-yl) benzamide derivatives as potent BRAFV600E inhibitors. Structure–activity relationship studies of these derivatives revealed that compounds b40 and b47 are the two most potent BRAFV600E inhibitors in this series.  相似文献   

16.
Autophagy inhibition is a potential therapeutic strategy in central nervous system (CNS) tumors. The BRAFV600E mutation is known to affect autophagy. Our studies indicate CNS tumor cells with BRAFV600E mutant cells (but not wild type) display high rates of induced autophagy, are sensitive to autophagy inhibition, and display synergy when chloroquine is combined with the RAF kinase inhibitor vemurafenib or standard chemotherapeutics. Our studies also indicate chloroquine can improve vemurafenib sensitivity in intrinsically resistant cells and in a patient with induced-vemurafenib resistance. These findings suggest CNS tumors with BRAFV600E are autophagy-dependent and that identification of BRAFV600E may be a marker to identify pediatric patients with the best potential response to autophagy inhibition.  相似文献   

17.
《Autophagy》2013,9(11):2077-2078
Autophagy inhibition is a potential therapeutic strategy in central nervous system (CNS) tumors. The BRAFV600E mutation is known to affect autophagy. Our studies indicate CNS tumor cells with BRAFV600E mutant cells (but not wild type) display high rates of induced autophagy, are sensitive to autophagy inhibition, and display synergy when chloroquine is combined with the RAF kinase inhibitor vemurafenib or standard chemotherapeutics. Our studies also indicate chloroquine can improve vemurafenib sensitivity in intrinsically resistant cells and in a patient with induced-vemurafenib resistance. These findings suggest CNS tumors with BRAFV600E are autophagy-dependent and that identification of BRAFV600E may be a marker to identify pediatric patients with the best potential response to autophagy inhibition.  相似文献   

18.
Although BRAFV600E is well known to play an important role in the tumorigenesis of melanoma, its molecular mechanism, particularly the epigenetic aspect, has been incompletely understood. Here, we investigated the role of BRAFV600E signaling in altering gene methylation in the genome of melanoma cells using a methylated CpG island amplification/CpG island microarray system and searched for genes coupled to the BRAFV600Esignaling through methylation aberrations. The results indicated that a wide range of genes with broad functions were linked to BRAFV600E signaling through their hyper- or hypomethylation. Expression of 59 genes hypermethylated upon BRAF knockdown was selectively tested and found to be largely correspondingly underexpressed, suggesting that these genes were naturally hypomethylated, and overexpressed with BRAFV600E in melanoma. This BRAFV600E-promoted hypomethylation was confirmed on genes selectively examined in primary melanoma tumors. Some of these genes were functionally tested and demonstrated to play a role in melanoma cell proliferation and invasion. As a mechanism of aberrant gene methylation driven by BRAFV600E, expression of the DNA methyltransferase 1 and histone methyltransferase EZH2 was profoundly affected by BRAFV600E. We have thus uncovered a previously unrecognized prominent epigenetic mechanism in the tumorigenesis of melanoma driven by BRAFV600E. Many of the functionally important genes controlled by the BRAFV600E signaling through aberrant methylation may prove to be novel therapeutic targets for melanoma.  相似文献   

19.
BRAF inhibitors have demonstrated improvement of overall survival in patients with metastatic melanoma and BRAFV600 mutations. In order to evaluate BRAF tumor heterogeneity between primary and metastatic site, we have evaluated the performance of immunohistochemistry (IHC) with an anti-BRAFV600E antibody in both localization by comparison with high resolution melting analysis followed by Sanger sequencing in a parallel blinded study. A total of 230 samples distributed as primary melanoma (n = 88) and different types of metastatic samples (n = 142) were studied in 99 patients with advanced or metastatic melanoma (stage III or IV). The prevalence of each BRAF mutation was c.1799T>A, BRAFV600E (45.2%), c.1799_1800TG>AA, BRAFV600E2 (3.0%), c.1798_1799GT>AA, BRAFV600K (3.0%), c.1801 A>G, BRAFK601E (1.3%), c.1789_1790CT>TC, BRAFL597S (0.4%), c.1780G>A, BRAFD594N (0.9%) respectively. IHC was positive in 109/112 samples harboring BRAFV600E/E2 mutations and negative in other cases. The cytoplasmic staining was either strongly positive in tumor cells of BRAFV600E mutated cases. It appeared strong brown, different from the vesicular grey cytoplasmic pigmentation of melanophages. Concordance between the two techniques was 96.4%. Sensitivity of IHC for detecting the BRAFV600E/E2 mutations was 97.3%, while specificity was 100%. Both our IHC and molecular study demonstrated homogeneity between primary and metastatic sites for BRAF status in melanoma. This study also provides evidence that IHC may be a cost-effective first-line method for BRAFV600E detection. Thereafter, molecular techniques should be used in negative, ambiguous or non-contributive cases.  相似文献   

20.
The limitations of revolutionary new mutation-specific inhibitors of BRAFV600E include the universal recurrence seen in melanoma patients treated with this novel class of drugs. Recently, our lab showed that simultaneous activation of the Wnt/β-catenin signaling pathway and targeted inhibition of BRAFV600E by PLX4720 synergistically induces apoptosis across a spectrum of BRAFV600E melanoma cell lines. As a follow-up to that study, treatment of BRAF-mutant and NRAS-mutant melanoma lines with WNT3A and the MEK inhibitor AZD6244 also induces apoptosis. The susceptibility of BRAF-mutant lines and NRAS-mutant lines to apoptosis correlates with negative regulation of Wnt/β-catenin signaling by ERK/MAPK signaling and dynamic decreases in abundance of the downstream scaffolding protein, AXIN1. Apoptosis-resistant NRAS-mutant lines can sensitize to AZD6244 by pretreatment with AXIN1 siRNA, similar to what we previously reported in BRAF-mutant cell lines. Taken together, these findings indicate that NRAS-mutant melanoma share with BRAF-mutant melanoma the potential to regulate apoptosis upon MEK inhibition through WNT3A and dynamic regulation of cellular AXIN1. Understanding the cellular context that makes melanoma cells susceptible to this combination treatment will contribute to the study and development of novel therapeutic combinations that may lead to more durable responses.  相似文献   

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