Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical College, Asahikawa, Japan.
Oncogene. 2014 Oct 2;33(40):4847-56. doi: 10.1038/onc.2013.429. Epub 2013 Oct 28.
It is well known that microRNAs (miRs) are abnormally expressed in various cancers and target the messenger RNAs (mRNAs) of cancer-associated genes. While (miRs) are abnormally expressed in various cancers, whether miRs directly target oncogenic proteins is unknown. The present study investigated the inhibitory effects of miR-18a on colon cancer progression, which was considered to be mediated through its direct binding and degradation of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). An MTT assay and xenograft model demonstrated that the transfection of miR-18a induced apoptosis in SW620 cells. A binding assay revealed direct binding between miR-18a and hnRNP A1 in the cytoplasm of SW620 cells, which inhibited the oncogenic functions of hnRNP A1. A competitor RNA, which included the complementary sequence of the region of the miR-18a-hnRNP A1 binding site, repressed the effects of miR-18a on the induction of cancer cell apoptosis. In vitro single and in vivo double isotope assays demonstrated that miR-18a induced the degradation of hnRNP A1. An immunocytochemical study of hnRNP A1 and LC3-II and the inhibition of autophagy by 3-methyladenine and ATG7, p62 and BAG3 siRNA showed that miR-18a and hnRNP A1 formed a complex that was degraded through the autophagolysosomal pathway. This is the first report showing a novel function of a miR in the autophagolysosomal degradation of an oncogenic protein resulting from the creation of a complex consisting of the miR and a RNA-binding protein, which suppressed cancer progression.
众所周知，微小 RNA（miRs）在各种癌症中异常表达，靶向癌症相关基因的信使 RNA（mRNAs）。虽然（miRs）在各种癌症中异常表达，但 miRs 是否直接靶向致癌蛋白尚不清楚。本研究探讨了 miR-18a 对结肠癌进展的抑制作用，认为这是通过其直接结合和降解异质核核糖核蛋白 A1（hnRNP A1）介导的。MTT 检测和异种移植模型表明，miR-18a 的转染诱导 SW620 细胞凋亡。结合测定显示 miR-18a 与 SW620 细胞质中的 hnRNP A1 直接结合，抑制 hnRNP A1 的致癌功能。包括 miR-18a-hnRNP A1 结合位点互补序列的竞争 RNA 抑制了 miR-18a 对诱导癌细胞凋亡的作用。体外单同位素和体内双同位素测定表明，miR-18a 诱导 hnRNP A1 的降解。hnRNP A1 和 LC3-II 的免疫细胞化学研究以及 3-甲基腺嘌呤和 ATG7、p62 和 BAG3 siRNA 对自噬的抑制作用表明，miR-18a 和 hnRNP A1 形成复合物，通过自噬溶酶体途径降解。这是第一个报道显示 miR 在致癌蛋白的自噬溶酶体降解中的新功能，这是由 miR 和 RNA 结合蛋白形成的复合物引起的，该复合物抑制了癌症的进展。
