Department of Surgical Oncology, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu 501-1194, Japan.
Department of General and Gastroenterological Surgery, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
Int J Mol Sci. 2018 Jul 9;19(7):2005. doi: 10.3390/ijms19072005.
The human DEAD/H-box RNA helicase DDX6 (RCK/p54) is a protein encoded by the fusion gene from the t(11;14)(q23;q32) chromosomal translocation observed in human B-cell lymphoma cell line RC-K8. DDX6 has a variety of functions such as translation initiation, pre-mRNA splicing, and ribosome assembly. However, details of the regulatory mechanism governing DDX6 and the functions of DDX6 are largely unknown. Previously, we reported that DDX6 is overexpressed in most malignant cell lines and clinical colorectal tumor samples and that DDX6 positively contributes to the pathogenesis of various cancers. In the current study, we aimed at revealing the function of DDX6 in HER2 and FGFR2 related human gastric cancer (GC) by using clinical samples and GC cell lines. DDX6 protein was overexpressed in about 60% of the clinical samples; HER2, in 35%; and FGFR2, in 30%, ( = 20). Interestingly, the DDX6 protein was overexpressed in all HER2-positive samples ( = 7), and in 83% (5 of 6) of the FGFR2-positive samples, which could reflect the contribution of DDX6 to the expression of HER2 and FGFR2. In the GC cell line MKN7, which has amplification, the knockdown of by siR-DDX6 led to the decreased expression of the HER2 protein. On the other hand, the knockdown of did not influence the DDX6 expression. Similar results were also obtained for the KATO-III and HSC39 cell lines having amplified FGFR2 expression. The increased expression of DDX6 induced a significantly increased expression of the HER2 protein without increasing the mRNA expression. The results of an RNP Immunoprecipitation (RIP)-assay using GC cells indicated that the DDX6 protein acted as an RNA-binding protein for and FGFR2 mRNAs and positively regulated their post-transcriptional processes. These findings demonstrated that DDX6 was an upstream molecule that positively regulated the expression of HER2 and FGFR2 at the post-transcriptional step in GC cells.
人类 DEAD/H-box RNA 解旋酶 DDX6（RCK/p54）是一种由人 B 细胞淋巴瘤细胞系 RC-K8 中观察到的 t（11;14）（q23;q32）染色体易位融合基因编码的蛋白质。DDX6 具有多种功能，如翻译起始、前体 mRNA 剪接和核糖体组装。然而，DDX6 的调控机制及其功能的详细信息在很大程度上仍是未知的。先前，我们报道 DDX6 在大多数恶性细胞系和临床结直肠肿瘤样本中过表达，并且 DDX6 正向促进各种癌症的发病机制。在本研究中，我们旨在通过使用临床样本和 GC 细胞系揭示 DDX6 在 HER2 和 FGFR2 相关人类胃癌（GC）中的功能。DDX6 蛋白在约 60%的临床样本中过表达；HER2 在 35%；FGFR2 在 30%，（=20）。有趣的是，DDX6 蛋白在所有 HER2 阳性样本中过表达（=7），并且在 83%（5/6）的 FGFR2 阳性样本中过表达，这反映了 DDX6 对 HER2 和 FGFR2 表达的贡献。在具有扩增的 GC 细胞系 MKN7 中，通过 siR-DDX6 敲低导致 HER2 蛋白表达降低。另一方面，敲低并不影响 DDX6 的表达。在具有扩增 FGFR2 表达的 KATO-III 和 HSC39 细胞系中也获得了类似的结果。DDX6 表达的增加诱导 HER2 蛋白的表达显著增加，而不会增加 mRNA 表达。使用 GC 细胞进行的 RNP 免疫沉淀（RIP）测定的结果表明，DDX6 蛋白作为 和 FGFR2 mRNA 的 RNA 结合蛋白，正向调节它们的转录后过程。这些发现表明，DDX6 是 GC 细胞中 HER2 和 FGFR2 表达的正调控的转录后步骤的上游分子。
