Signal Transduction Laboratory, University of Luxembourg, 162A Avenue de la Faïencerie, Luxembourg, L-1511, Luxembourg.
Cell Commun Signal. 2012 Dec 17;10(1):41. doi: 10.1186/1478-811X-10-41.
The type-II-cytokine IFN-γ is a pivotal player in innate immune responses but also assumes functions in controlling tumor cell growth by orchestrating cellular responses against neoplastic cells. The role of IFN-γ in melanoma is not fully understood: it is a well-known growth inhibitor of melanoma cells in vitro. On the other hand, IFN-γ may also facilitate melanoma progression. While interferon-regulated genes encoding proteins have been intensively studied since decades, the contribution of miRNAs to effects mediated by interferons is an emerging area of research.We recently described a distinct and dynamic regulation of a whole panel of microRNAs (miRNAs) after IFN-γ-stimulation. The aim of this study was to analyze the transcriptional regulation of miR-29 family members in detail, identify potential interesting target genes and thus further elucidate a potential signaling pathway IFN-γ → Jak→ P-STAT1 → miR-29 → miR-29 target genes and its implication for melanoma growth.
Here we show that IFN-γ induces STAT1-dependently a profound up-regulation of the miR-29 primary cluster pri-29ab-1 in melanoma cell lines. Furthermore, expression levels of pri-29ab-1 and mature miR-29a and miR-29b were elevated while the pri-29b-2~c cluster was almost undetectable. We observed an inverse correlation between miR-29a/b expression and the proliferation rate of various melanoma cell lines. This finding could be corroborated in cells transfected with either miR-29 mimics or inhibitors. The IFN-γ-induced G1-arrest of melanoma cells involves down-regulation of CDK6, which we proved to be a direct target of miR-29 in these cells. Compared to nevi and normal skin, and metastatic melanoma samples, miR-29a and miR-29b levels were found strikingly elevated in certain patient samples derived from primary melanoma.
Our findings reveal that the miR-29a/b1 cluster is to be included in the group of IFN- and STAT-regulated genes. The up-regulated miR-29 family members may act as effectors of cytokine signalling in melanoma and other cancer cells as well as in the immune system.
II 型细胞因子 IFN-γ 是先天免疫反应的关键因子，但通过协调细胞对肿瘤细胞的反应，它也具有控制肿瘤细胞生长的功能。IFN-γ 在黑色素瘤中的作用尚未完全阐明：它是体外黑色素瘤细胞的一种众所周知的生长抑制剂。另一方面，IFN-γ 也可能促进黑色素瘤的进展。虽然干扰素调节基因编码的蛋白质已被研究了几十年，但 miRNA 对干扰素介导的作用的贡献是一个新兴的研究领域。我们最近描述了 IFN-γ 刺激后整个 miRNA （miRNA） 面板的独特和动态调节。本研究的目的是详细分析 miR-29 家族成员的转录调控，鉴定潜在的有趣靶基因，并进一步阐明 IFN-γ→Jak→P-STAT1→miR-29→miR-29 靶基因及其对黑色素瘤生长的潜在信号通路。
在这里，我们表明 IFN-γ 诱导 STAT1 依赖性地在黑色素瘤细胞系中显著上调 miR-29 初级簇 pri-29ab-1。此外，pri-29ab-1 和成熟 miR-29a 和 miR-29b 的表达水平升高，而 pri-29b-2~c 簇几乎无法检测到。我们观察到各种黑色素瘤细胞系中 miR-29a/b 表达与增殖率之间存在反比关系。这一发现可以在转染 miR-29 模拟物或抑制剂的细胞中得到证实。IFN-γ 诱导的黑色素瘤细胞 G1 期阻滞涉及 CDK6 的下调，我们证明 CDK6 是这些细胞中 miR-29 的直接靶标。与痣和正常皮肤以及转移性黑色素瘤样本相比，某些源自原发性黑色素瘤的患者样本中 miR-29a 和 miR-29b 的水平明显升高。
我们的研究结果表明，miR-29a/b1 簇被纳入 IFN 和 STAT 调节基因组。上调的 miR-29 家族成员可能作为细胞因子信号在黑色素瘤和其他癌细胞以及免疫系统中的效应子发挥作用。
