In Vitro Methods for Analyzing miRNA Roles in Cancer Cell Proliferation, Invasion, and Metastasis

MicroRNAs (miRNAs) are small noncoding, single-stranded RNAs consisting of 20-24 nucleotides (Bartel, Cell 116:281-297, 2004), which regulate target genes expression by interacting with 3'-untranslated regions (3'-UTRs) of target mRNAs, leading to translation repression or mRNA degradation (Filipowicz et al., Nat Rev Genet 9:102-114, 2008; Nilsen, Trends Genet 23:243-249, 2007). Accumulating evidence has elucidated them as oncogenes or tumor suppressors in cancers such as hepatocellular carcinoma, breast cancer, and lung cancer (Liu et al., Gastroenterology 136:683-693, 2009; Yu et al., Cell 131:1109-1123, 2007; Zhou et al., Sci Rep 7:42680, 2017; Iorio and Croce, Carcinogenesis 33:1126-1133, 2012). MiRNAs are involved in various biological processes, including cell proliferation (Liu et al., Mol Cancer Res 11:1314-1325, 2013), differentiation (Liu et al., Mol Cancer Res 11:1314-1325, 2013), apoptosis (Pan et al., Oncol Res 24:429-435, 2016), invasion and metastasis (Liu et al., Nat Commun 8:14270, 2017). Understanding the role of miRNAs in tumor gives new perspective on cancer diagnosis and therapy (Rupaimoole and Slack, Nat Rev Drug Discov 16:203-222, 2017; Berindan-Neagoe et al., CA Cancer J Clin 64:311-336, 2014). This chapter will focus on the in vitro methods for identifying miRNAs roles in cell proliferation, invasion, and metastasis in tumor development, which includes CCK-8 assay, Wound Healing assay, and Transwell assay.