Flammiger Anna, Besch Robert, Cook Anthony L, Maier Tanja, Sturm Richard A, Berking Carola
Department of Dermatology and Allergology, Ludwig-Maximilian University, Munich, Germany.
J Invest Dermatol. 2009 Apr;129(4):945-53. doi: 10.1038/jid.2008.316. Epub 2008 Oct 16.
Nestin is an intermediate filament protein and a marker of neuroectodermal stem cells indicating multipotentiality and regenerative capability. In melanoma tissues, nestin re-expression was correlated with tumor progression. Activation of the nestin neural enhancer was shown to be dependent on the binding of class III POU transcription factors, with brain-2 (BRN2) suggested to play a key role. We found both nestin and BRN2 mRNA in almost all of 13 analyzed melanoma cell lines of different progression stages, but expression levels did not correlate. Nestin protein was detected in 11 of 13 and BRN2 protein in 7 of 13 melanoma cell lines independent of progression stage. Downregulation of BRN2 by small-interfering RNA did not alter nestin expression in melanoma cells. However, POU proteins, such as BRN2, commonly cooperate with transcription factors of the Sry-box (SOX) family by binding to a nearby DNA site necessary for their action. SOX9 and SOX10 have been shown to be expressed in melanocyte precursors, with SOX10 downregulated upon differentiation. We now demonstrate SOX9 and SOX10 protein expression in melanoma tissues and cell lines. Downregulation of SOX9 and of SOX10 markedly decreased nestin levels in melanoma cells in a cooperative manner. Thus, SOX9 and SOX10 but not BRN2 seem to be required for nestin expression in human melanoma.
巢蛋白是一种中间丝蛋白，是神经外胚层干细胞的标志物，表明其具有多能性和再生能力。在黑色素瘤组织中，巢蛋白的重新表达与肿瘤进展相关。巢蛋白神经增强子的激活被证明依赖于III类POU转录因子的结合，其中脑-2（BRN2）被认为起关键作用。我们在13个不同进展阶段的黑色素瘤细胞系中，几乎所有细胞系都检测到了巢蛋白和BRN2的mRNA，但表达水平并无相关性。在13个黑色素瘤细胞系中的11个检测到了巢蛋白蛋白，13个中的7个检测到了BRN2蛋白，且与进展阶段无关。用小干扰RNA下调BRN2并未改变黑色素瘤细胞中巢蛋白的表达。然而，POU蛋白，如BRN2，通常通过与Sry盒（SOX）家族转录因子结合到其作用所需的附近DNA位点来协同作用。SOX9和SOX10已被证明在黑素细胞前体中表达，分化时SOX10表达下调。我们现在证明了SOX9和SOX10蛋白在黑色素瘤组织和细胞系中的表达。下调SOX9和SOX10以协同方式显著降低了黑色素瘤细胞中巢蛋白的水平。因此，对于人黑色素瘤中巢蛋白的表达，似乎需要SOX9和SOX10而非BRN2。
