Proliferation and Tumorigenesis of a Murine Sarcoma Cell Line in the Absence of Dicer. Mus musculus

MicroRNAs are a class of short ~22 nucleotide RNAs predicted to regulate nearly half of all protein-coding genes, including many involved in basal cellular processes and organismal development. Although both increases and decreases in the levels of specific miRNAs have been shown to promote tumor development, a global reduction in miRNAs is commonly observed in various human tumors. However, complete loss has not been documented, suggesting an essential function for miRNAs in tumorigenesis. Here we present the finding that transformed or immortalized Dicer-null somatic cells can be isolated readily in vitro, maintain the characteristics of Dicer-expressing controls and remain stably proliferative. Furthermore, Dicer-null cells from a sarcoma cell line, though depleted of miRNAs, are competent for tumor formation. Hence, miRNA levels in cancer may be maintained in vivo by a complex stabilizing selection in the intratumoral environment. Overall design: Small RNAs from tumor cell lines (murine sarcoma KrasG12D, p53 -/-) with and without Dicer (Dicer f/-, Dicer -/-) were analyzed.

微小RNA（MicroRNAs）是一类长度约为22个核苷酸的RNA分子，被预测可调控近半数的蛋白编码基因，其中包含诸多参与基础细胞过程及机体发育的基因。尽管已有研究证实，特定miRNA的表达上调或下调均可促进肿瘤发生，但在多种人类肿瘤中普遍存在miRNA整体水平降低的现象。然而目前尚无完全缺失miRNA的报道，这提示miRNA在肿瘤发生过程中具有不可或缺的功能。本研究发现，转化或永生化的Dicer敲除体细胞可在体外轻松分离获得，其能够维持表达Dicer的对照细胞的特征，并保持稳定的增殖能力。此外，来自肉瘤细胞系的Dicer敲除细胞即使完全缺失miRNA，仍具备成瘤能力。由此可见，肿瘤微环境中的复杂稳定选择机制，或可在体内维持癌症组织中的miRNA水平。总体实验设计：对带有或不带有Dicer（Dicer f/-, Dicer -/-）的肿瘤细胞系（小鼠肉瘤KrasG12D、p53 -/-）中的小分子RNA进行了分析。