Identification of cell cycle-targeting microRNAs through genome-wide screens

Concepts and Design of Introducing Synthetic MicroRNAs into Mammalian Cells

MicroRNAs are pleiotropic gene modulators affecting numerous cellular processes in development and disease. Due to their small size, microRNAs can easily be synthesized for the purpose of mechanistic or therapeutic studies in biological processes, including autophagy. Depending on the biological question posed, approaches of modulating microRNAs involve either microRNA mimic or inhibitory nucleic acid molecules. This protocol outlines the detailed methodological steps to introduce synthetic microRNA drugs into target cells in vitro and in vivo and how to monitor their function. In addition, it provides insights on how to control the adverse effects when ectopically expressing synthetic microRNA mimic molecules.

Construction of a Full-Length 3'UTR Reporter System for Identification of Cell-Cycle Regulating MicroRNAs

Three prime untranslated region (3'UTR) reporter constructs are widely used by the scientific community to functionally link microRNAs (miRNAs) to suppression of mRNA expression. However, full-length 3'UTR vectors are rarely employed due to labor-intensive cloning work. Instead, 3'UTR fragments containing putative miRNA binding sites are commonly utilized to mechanistically validate miRNAs. Assaying truncated 3'UTRs may falsely validate miRNAs due to altered positioning of binding sites in respect to 3'UTR length and RNA secondary structure. Here we present a detailed protocol for the construction of full-length 3'UTR luciferase reporter constructs that was used to unveil miRNAs regulating multiple cell-cycle factors.

PCAT1 induced by transcription factor YY1 promotes cholangiocarcinoma proliferation, migration and invasion by sponging miR-216a-3p to up-regulate oncogene BCL3

This study was designed to illustrate the function and role of PCAT1 in CCA. The relative expression was confirmed by RT-qPCR and western blot. The biological function of PCAT1 was evaluated by CCK8, EdU, colony formation, wound healing, transwell, and subcutaneous tumor formation assays. Protein levels of EMT markers were measured by western blot. The binding relationship was predicted by JASPAR and starBase. The binding of YY1 to PCAT1 promoter was assessed by ChIP and luciferase reporter. The binding capacity between miR-216a-3p and PCAT1 as well as BCL3 was assessed by luciferase reporter and AGO2-RIP assays. In this study, we found that PCAT1 was up-regulated in CCA tissues and cells, and the PCAT1 overexpression was associated with poor prognosis. Moreover, PCAT1 was assessed as an independent risk factor of prognosis for CCA patients. Amplified PCAT1 was found to promote tumor proliferation, migration, invasion and EMT process, whereas PCAT1 knockdown inhibited these malignant phenotypes. Mechanistically, PCAT1 was predominantly localized in the cytoplasm and competitively bound miR-216a-3p to increase BCL3 expression. In addition, PCAT1 was activated by transcription factor YY1. This study revealed that PCAT1 acted as an oncogene in CCA, and the YY1/PCAT1/miR-216a-3p/BCL3 axis exhibited critical functions in CCA progression.

Upregulation of the Coatomer Protein Complex Subunit beta 2 (COPB2) Gene Targets microRNA-335-3p in NCI-H1975 Lung Adenocarcinoma Cells to Promote Cell Proliferation and Migration

BACKGROUND The coatomer protein complex subunit beta 2 (COPB2) gene is upregulated and promotes cell proliferation in some cancer cells. This study aimed to investigate the role of microRNA (miRNA) targeting by COPB2 gene expression in human lung adenocarcinoma cell lines, including NCI-H1975 cells. MATERIAL AND METHODS COPB2 expression in normal human bronchial epithelial cells and lung adenocarcinoma cells was measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. NCI-H1975 human lung adenocarcinoma cells were transfected with short-interfering COPB2 (siCOPB2). Cell apoptosis and cell proliferation were evaluated by flow cytometry and Cell Counting Kit-8 (CCK-8) assays, respectively. The transwell assay evaluated cell migration. Targeting of miR-335-3p by COPB2 was predicted using TargetScan 7.2 and verified using a dual-luciferase reporter assay in NCI-H1975 cells. MiR-335-3p mimics were transfected into NCI-H1975 cells. The further functional analysis included detection of protein expression for cyclin D1, tissue inhibitor matrix metalloproteinase-1 (TIMP-1), matrix metallopeptidase 9 (MMP9), Bcl-2, and Bax, to verify the role of miR-335-3p targeting by COPB2 in lung adenocarcinoma cells. RESULTS COPB2 was upregulated in lung adenocarcinoma cells and was a direct target of miR-335-3p mimics. COPB2 knockdown promoted cell apoptosis, inhibited cell migration and proliferation in NCI-H1975 cells. The effects of COPB2 knockdown on NCI-H1975 cells were increased by miR-335-3p mimics, which also further reduced the expression levels of cyclin D1, MMP9, and Bcl-2 and further increased TIMP-1 and Bax by siCOPB2. CONCLUSIONS This study showed that COPB2 was the functional target of miR-335-3p in NCI-H1975 human adenocarcinoma cells.

miR-100-5p confers resistance to ALK tyrosine kinase inhibitors Crizotinib and Lorlatinib in EML4-ALK positive NSCLC

Lung cancer causes the highest number of cancer-related deaths worldwide. Resistance to therapy is a major clinical issue contributing to the poor prognosis of lung cancer. In recent years, targeted therapy has become a concept where subgroups of non-small cell lung cancer (NSCLC) with genetically altered receptor tyrosine kinases are targeted by tyrosine kinase inhibitors (TKIs). One such subgroup harbors a gene fusion of echinoderm microtubule-associated protein-like 4 (EML4) with anaplastic lymphoma kinase (ALK). Although most NSCLC patients with EML4-ALK fusions initially respond to ALK TKI-therapy they eventually develop resistance. While ALK kinase domain mutations contribute to ALK TKI-refractoriness, they are only present in a fraction of all ALK TKI-resistant tumors. In this study we sought to explore a possible involvement of microRNAs (miRNAs) in conferring resistance to ALK TKIs in ALK TKI-refractory NSCLC cell lines. We subjected our ALK TKI-refractory cancer cells along with parental cancer cells to systematic miRNA expression arrays. Furthermore, ALK TKI-refractory cancer cells were exposed to a synthetic miRNA inhibitory Locked Nucleic Acid (LNA)-library in the presence of ALK TKIs Crizotinib or Lorlatinib. The outcome of the combined approaches uncovered miR-100-5p to confer resistance to Crizotinib and Lorlatinib in EML4-ALK NSCLC cells and to be a potential therapeutic target in drug resistance.

miR-126-5p targets Malate Dehydrogenase 1 in non-small cell lung carcinomas

Malate Dehydrogenase (MDH) 1 has recently been shown to be highly expressed and display prognostic value in non-small cell lung carcinomas (NSCLCs). However, it is not known how MDH1 expression is regulated and there is no current molecular or chemical strategy that specifically targets MDH1. This may be due to structural and enzymatic similarities with its isoenzyme, malate dehydrogenase 2 (MDH2). However, MDH1 and MDH2 are encoded by distinct genes and this opens up the possibility for modulation at the expression level. Here, we screened in silico for microRNAs (miRs) that selectively targets the 3'UTR region of MDH1. These analyses revealed that mir-126-5p has three binding sites in the 3'UTR region of MDH1. Additionally, we show that expression of miR-126-5p suppresses the enzymatic activity of MDH1, mitochondrial respiration and caused cell death in NSCLC cell lines.