The Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, Oxford University, Oxford, United Kingdom.
PLoS Pathog. 2011 Feb;7(2):e1001305. doi: 10.1371/journal.ppat.1001305. Epub 2011 Feb 24.
Notwithstanding the well-characterised roles of a number of oncogenes in neoplastic transformation, microRNAs (miRNAs) are increasingly implicated in several human cancers. Discovery of miRNAs in several oncogenic herpesviruses such as KSHV has further highlighted the potential of virus-encoded miRNAs to contribute to their oncogenic capabilities. Nevertheless, despite the identification of several possible cancer-related genes as their targets, the direct in vivo role of virus-encoded miRNAs in neoplastic diseases such as those induced by KSHV is difficult to demonstrate in the absence of suitable models. However, excellent natural disease models of rapid-onset Marek's disease (MD) lymphomas in chickens allow examination of the oncogenic potential of virus-encoded miRNAs. Using viruses modified by reverse genetics of the infectious BAC clone of the oncogenic RB-1B strain of MDV, we show that the deletion of the six-miRNA cluster 1 from the viral genome abolished the oncogenicity of the virus. This loss of oncogenicity appeared to be primarily due to the single miRNA within the cluster, miR-M4, the ortholog of cellular miR-155, since its deletion or a 2-nucleotide mutation within its seed region was sufficient to inhibit the induction of lymphomas. The definitive role of this miR-155 ortholog in oncogenicity was further confirmed by the rescue of oncogenic phenotype by revertant viruses that expressed either the miR-M4 or the cellular homolog gga-miR-155. This is the first demonstration of the direct in vivo role of a virus-encoded miRNA in inducing tumors in a natural infection model. Furthermore, the use of viruses deleted in miRNAs as effective vaccines against virulent MDV challenge, enables the prospects of generating genetically defined attenuated vaccines.
尽管许多癌基因在肿瘤转化中具有明确的作用，但 microRNAs（miRNAs）越来越多地与几种人类癌症有关。在几种致癌疱疹病毒（如 KSHV）中发现 miRNAs，进一步强调了病毒编码的 miRNAs 可能有助于其致癌能力。然而，尽管已经确定了几种可能的癌症相关基因作为它们的靶标，但在缺乏合适模型的情况下，病毒编码的 miRNAs 在肿瘤疾病中的直接体内作用，如 KSHV 诱导的肿瘤疾病，很难证明。然而，鸡中快速发作的马立克氏病（MD）淋巴瘤的极好的天然疾病模型允许检查病毒编码的 miRNAs 的致癌潜力。使用通过传染性 BAC 克隆的反向遗传修饰的病毒，我们发现从病毒基因组中删除六个 miRNA 簇 1 会消除病毒的致癌性。这种致癌性的丧失似乎主要是由于簇内的单个 miRNA，miR-M4，细胞 miR-155 的同源物，因为其缺失或其种子区域内的 2 个核苷酸突变足以抑制淋巴瘤的诱导。该 miR-155 同源物在致癌性中的明确作用通过表达 miR-M4 或细胞同源物gga-miR-155 的回复病毒来拯救致癌表型进一步得到证实。这是第一个在天然感染模型中直接证明病毒编码的 miRNA 在诱导肿瘤中的体内作用的证明。此外，使用缺失 miRNA 的病毒作为针对强毒 MDV 挑战的有效疫苗，为生成遗传定义的减毒疫苗开辟了前景。
