Reduced expression of the neuron restrictive silencer factor permits transcription of glycine receptor α1 subunit in small-cell lung cancer cells
Reduced expression of the neuron restrictive silencer factor permits transcription of glycine receptor α1 subunit in small-cell lung cancer cells
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DOI：
10.1038/sj.onc.1206790
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发表时间：
2003-08-28
期刊：
影响因子：
8
通讯作者：
Doeberitz, MV
中科院分区：
文献类型：
--
作者：
Gurrola-Diaz, C;Lacroix, J;Doeberitz, MV
小细胞肺癌 (SCLC) 细胞表达与神经元限制性沉默因子 (NRSF) 活性缺陷相关的各种神经元分化标志物。在这里，我们描述了 NRSF 靶基因在 SCLC 中上调的机制及其对细胞存活的功能影响。由于甘氨酸受体 (GlyR) α1 亚基基因 GLRA1 在其 5' UTR 内包含 NRSF 结合 (NRSE) 的序列基序，因此它可作为 NRSF 活性的细胞替代标记。 GLRA1 在非转化细胞中的表达主要限于脊髓、视网膜和脑干中的细胞。在此描述的实验中，我们在四分之三的 SCLC 衍生细胞系和从 SCLC 获得的五分之三的活检样本中检测到 GLRA1 转录本。相比之下，在 10 个非恶性和 15 个非小细胞肺癌活检中均未发现 GLRA1 转录本。与这一观察结果一致，NRSF 介导的对含有 GLRA1 (GLRA1 NRSE) 基因 NRSE 的表达构建体的抑制在四种“经典”SCLC 细胞系中的三种中受到损害，而在 NRSF 缺陷的 SCLC 细胞系中，NRSF 的外源过度表达重建了报告质粒的沉默。 NRSF 转录物的水平以及 NRSF 与 NRSE 特异性结合的水平与 SCLC 细胞系中 GLRA1 转录物的水平相关。编码截短的 NRSF 蛋白并在一些 SCLC 中表达的剪接变体不会拮抗含有 NRSE 的基因的抑制。最有趣的是，NRSF 表达的重建诱导 SCLC 细胞凋亡，这表明抑制 NRSF 活性是 SCLC 亚组致癌的关键步骤。
Small-cell lung cancer (SCLC) cells express various markers of neuronal differentiation associated with deficient activity of the neuron-restricted silencer factor (NRSF). Here, we characterize mechanisms by which NRSF target genes are upregulated in SCLC and their functional consequences for cell survival. Since the glycine receptor (GlyR) alpha1 subunit gene, GLRA1, contains a sequence motif for NRSF binding (NRSE) within its 5' UTR, it served as a cellular surrogate marker for NRSF activity. Expression of GLRA1 in nontransformed cells is largely restricted to cells in the spinal cord, retina and brain stem. In experiments described here, we detected GLRA1 transcripts in three out of four SCLC-derived cell lines and in three of five biopsy samples obtained from SCLCs. In contrast, no GLRA1 transcripts were found in 10 nonmalignant nor 15 non-small-cell lung cancer biopsies. Consistent with this observation, NRSF-mediated suppression of an expression construct harbouring the NRSE of the GLRA1 (GLRA1 NRSE) gene was impaired in three of four 'classic' SCLC cell lines, whereas exogenous overexpression of NRSF in NRSF-deficient SCLC cell lines reconstituted silencing of the reporter plasmid. The level of NRSF transcripts as well as the level of specifically bound NRSF to the NRSE correlated with the level of GLRA1 transcripts in SCLC cell lines. Splice variants encoding truncated NRSF proteins and expressed in some SCLC did not antagonize the repression of NRSE-containing genes. Most interestingly, reconstitution of NRSF expression induced apoptosis in SCLC cells, suggesting that inhibition of NRSF activity is a crucial step in the carcinogenesis of a subgroup of SCLC.