Amaar Yousef G, Reeves Mark E
Surgical Oncology Laboratory, Loma Linda VA Medical Center, Loma Linda, CA, USA.
Loma Linda University Cancer Center, Loma Linda, CA, USA.
Oncotarget. 2019 Jan 4;10(2):123-132. doi: 10.18632/oncotarget.26498.
RASSF1C functions as an oncogene in lung cancer cells by stimulating proliferation and migration, and reducing apoptosis. Further, RASSF1C up-regulates important protein-coding and non-coding genes involved in lung cancer cell growth, including the stem cell self-renewal gene, , and small noncoding PIWI-interacting RNAs (piRNAs). In this article, we report the identification of microRNAs (miRNAs) that are modulated in lung cancer cells over-expressing RASSF1C. A lung cancer-specific miRNA PCR array screen was performed to identify RASSF1C target miRNA-coding genes using RNA isolated from the lung cancer cell line H1299 stably over-expressing RASSF1C and corresponding control. Several modulated miRNA genes were identified that are important in cancer cell proliferation and survival. Among the miRNAs down-regulated by RASSF1C is miRNA-33a-5p (miRNA-33a), which functions as a tumor suppressor in lung cancer cells. We validated that over-expression of RASSF1C down-regulates miR-33a expression and RASSF1C knockdown up-regulates miR-33a expression. We found that RASSF1C over-expression also increases β-catenin, vimentin, and snail protein levels in cells over-expressing miR-33a. In addition, we found that RASSF1C up-regulates the expression of ABCA1 mRNA which is a known target of miR-33a. Our findings suggest that RASSF1C may promote lung epithelial mesenchymal transition (EMT), resulting in the development of a lung cancer stem cell phenotype, progression, and metastasis, in part, through modulation of miR-33a expression. Our findings reveal a new mechanistic insight into how RASSF1C functions as an oncogene.
RASSF1C通过刺激增殖和迁移以及减少凋亡在肺癌细胞中发挥癌基因的作用。此外，RASSF1C上调参与肺癌细胞生长的重要蛋白质编码和非编码基因，包括干细胞自我更新基因以及小的非编码PIWI相互作用RNA（piRNA）。在本文中，我们报道鉴定了在过表达RASSF1C的肺癌细胞中受到调控的微小RNA（miRNA）。使用从稳定过表达RASSF1C的肺癌细胞系H1299和相应对照中分离的RNA，进行肺癌特异性miRNA PCR阵列筛选以鉴定RASSF1C靶miRNA编码基因。鉴定出了几个在癌细胞增殖和存活中起重要作用的受调控的miRNA基因。在被RASSF1C下调的miRNA中，miRNA-33a-5p（miRNA-33a）在肺癌细胞中起肿瘤抑制作用。我们验证了RASSF1C的过表达下调miR-33a的表达，而RASSF1C的敲低上调miR-33a的表达。我们发现RASSF1C的过表达还增加了过表达miR-33a的细胞中β-连环蛋白、波形蛋白和蜗牛蛋白的水平。此外，我们发现RASSF1C上调ABCA1 mRNA的表达，ABCA1是已知的miR-33a靶标。我们的研究结果表明，RASSF1C可能促进肺上皮间质转化（EMT），部分通过调节miR-33a的表达导致肺癌干细胞表型的发展、进展和转移。我们的研究结果揭示了RASSF1C作为癌基因发挥作用的新机制。
