BRAF silencing by short hairpin RNA or chemical blockade by PLX4032 leads to different responses in melanoma and thyroid carcinoma cells
BRAF silencing by short hairpin RNA or chemical blockade by PLX4032 leads to different responses in melanoma and thyroid carcinoma cells
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DOI：
10.1158/1541-7786.mcr-07-2001
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发表时间：
2008-05-01
影响因子：
5.2
通讯作者：
Gambacorti-Passerini, Carlo
中科院分区：
文献类型：
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作者：
Sala, Elisa;Mologni, Luca;Gambacorti-Passerini, Carlo
据报道，多种类型的癌症都存在 BRAF 激活突变，包括黑色素瘤（约占 70% 的病例）、甲状腺癌（30-70%）、卵巢癌（15-30%）和结直肠癌（5-20%）。突变体 BRAF 具有组成型激酶活性，并导致丝裂原激活蛋白激酶途径过度激活。 BRAF 沉默可诱导黑色素瘤异种移植物消退，表明 BRAF 对细胞存活的重要作用。我们建立了一个可诱导的短发夹 RNA 系统来比较致癌 BRAF 在甲状腺癌和黑色素瘤细胞中的作用。尽管 BRAF 敲低导致黑色素瘤细胞系 A375 细胞凋亡，但间变性甲状腺癌细胞 ARO 在沉默后出现生长停滞，几乎没有或没有细胞死亡。长期沉默后，诱导甲状腺分化标志物碘化钠同向转运蛋白的重新表达。两种细胞系中 BRAF 下调的不同结果与响应 BRAF 有丝分裂信号阻断的 p21(CIP1/WAF1) 表达水平的相反调节有关。这些结果得到了特定 BRAF 小分子抑制剂 PLX4032 的证实。 p21（CIP1/WAF1）表达的恢复使黑色素瘤细胞免于死亡。总而言之，我们的数据表明，致癌 BRAF 抑制可能对细胞命运产生不同的影响，具体取决于细胞类型。此外，我们认为间变性甲状腺癌细胞中存在不依赖于 BRAF 的细胞存活机制。
BRAF-activating mutations have been reported in several types of cancer, including melanoma (similar to 70% of cases), thyroid (30-70%), ovarian (15-30%), and colorectal cancer (5-20%). Mutant BRAF has constitutive kinase activity and causes hyperactivation of the mitogen-activated protein kinase pathway. BRAF silencing induces regression of melanoma xenografts, indicating the essential role of BRAF for cell survival. We set up an inducible short hairpin RNA system to compare the role of oncogenic BRAF in thyroid carcinoma versus melanoma cells. Although BRAF knockdown led to apoptosis in the melanoma cell line A375, the anaplastic thyroid carcinoma cell ARO underwent growth arrest upon silencing, with little or no cell death. Reexpression of the thyroid differentiation marker, sodium iodide symporter, was induced after long-term silencing. The different outcome of BRAF down-regulation in the two cell lines was associated with an opposite regulation of p21(CIP1/WAF1) expression levels in response to the block of the BRAF mitogenic signal. These results were confirmed using a specific BRAF small-molecule inhibitor, PLX4032. Restoration of p21(CIP1/WAF1) expression rescued melanoma cells from death. Altogether, our data indicate that oncogenic BRAF inhibition can have a different effect on cell fate depending on the cellular type. Furthermore, we suggest that a BRAF-independent mechanism of cell survival exists in anaplastic thyroid cancer cells.