BRAF mediates RET/PTC-induced mitogen-activated protein kinase activation in thyroid cells: functional support for requirement of the RET/PTC-RAS-BRAF pathway in papillary thyroid carcinogenesis
| Autor: | Cleo Mesa, Norisato Mitsutake, Jeffrey A. Knauf, Shin Mitsutake, James A. Fagin, Makoto Miyagishi, Nagako Akeno, Lei Zhang, Kazunari Taira |
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| Rok vydání: | 2005 |
| Předmět: |
Sodium-iodide symporter
MAPK/ERK pathway Proto-Oncogene Proteins B-raf endocrine system medicine.medical_specialty Small interfering RNA endocrine system diseases Oncogene Proteins Fusion Thyroid Gland Endocrinology Internal medicine medicine Animals Gene Silencing Thyroid Neoplasms Extracellular Signal-Regulated MAP Kinases neoplasms Cells Cultured Regulation of gene expression Gene knockdown biology Gene Expression Profiling Proto-Oncogene Proteins c-ret Protein-Tyrosine Kinases Molecular biology digestive system diseases Carcinoma Papillary Clone Cells Rats Enzyme Activation Gene Expression Regulation Neoplastic Isoenzymes Proto-Oncogene Proteins c-raf enzymes and coenzymes (carbohydrates) Mitogen-activated protein kinase biology.protein Cancer research RNA ARAF |
| Zdroj: | Endocrinology. 147(2) |
| ISSN: | 0013-7227 |
| Popis: | In human papillary thyroid cancers (PTCs), mutations of RET/PTC, NTRK, RAS, or BRAF are found in about two thirds of cases with practically no overlap, providing genetic evidence that constitutive signaling along RET-RAS-BRAF-MAPK is key to their development. The requirement for BRAF in RET/PTC-mediated MAPK activation and gene expression has not been tested functionally. There are three RAF isoforms: ARAF, BRAF, and CRAF. Compared with the others, ARAF is a much weaker stimulator of MAPK. To determine the key RAF isoform mediating RET/PTC-induced ERK phosphorylation, we stably transfected doxycycline-inducible RET/PTC3-expressing thyroid PCCL3 cells with small interfering RNA vectors to induce selective knockdown of BRAF or CRAF. Conditional RET/PTC3 expression induced comparable ERK phosphorylation in CRAF knockdown and control cells but negligible ERK phosphorylation in BRAF knockdown cells. Selective knockdown of BRAF prevented RET/PTC-dependent down-regulation of the sodium iodide symporter, a gene that confers key biological effects of RET/PTC in PTCs. Moreover, microarray analysis revealed numerous RET/PTC-regulated genes showing requirement of BRAF for appropriate expression. These data indicate that BRAF is required for RET/PTC-induced MAPK activation in thyroid cells and support the notion that BRAF inactivation may be an attractive target for PTCs. |
| Databáze: | OpenAIRE |
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