This study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1D1A3B03035662); and Hallym University Research Fund, 2017 (HRF-201703-003).

1. Mature MicroRNA (miRNA) Expression Analysis
<ol>
	<li>Mature miRNA complementary DNA (cDNA) synthesis
	<ol>
		<li>Add 254 ng of total RNA and 4.5 &#181;L of deoxyribonuclease I (DNase I) mixtures, and then add ultrapure water into PCR strip-tubes to make up to 18 &#181;L (Figure 2A). Prepare the reaction for each total RNA sample purified from several cell lines using enough amount of DNase I mixtures based on the total number of reactions. 
		NOTE:</strong...

<ol>
	<li>He, L., Hannon, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs:+small+RNAs+with+a+big+role+in+gene+regulation.">MicroRNAs: small RNAs with a big role in gene regulation.</a> Nature Reviews Genetics. 5 (7), 522-531 (2004).</li><li>Park, J. K., Doseff, A. I., Schmittgen, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs+Targeting+Caspase-3+and+-7+in+PANC-1+Cells.">MicroRNAs Targeting Caspase-3 and -7 in PANC-1 Cells.</a> International Journal of Molecular Sciences. 19 (4), (2018).</li><li>Park, J. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs-103/107+coordinately+regulate+macropinocytosis+and+autophagy.">MicroRNAs-103/107 coordinately regulate macropinocytosis and autophagy.</a> Journal of Cell Biology. 215 (5), 667-685 (2016).</li><li>Henry, J. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=miR-199a-3p+targets+CD44+and+reduces+proliferation+of+CD44+positive+hepatocellular+carcinoma+cell+lines.">miR-199a-3p targets CD44 and reduces proliferation of CD44 positive hepatocellular carcinoma cell lines.</a> Biochemical and Biophysical Research Communications. 403 (1), 120-125 (2010).</li><li>Hoefert, J. E., Bjerke, G. A., Wang, D., Yi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+microRNA-200+family+coordinately+regulates+cell+adhesion+and+proliferation+in+hair+morphogenesis.">The microRNA-200 family coordinately regulates cell adhesion and proliferation in hair morphogenesis.</a> Journal of Cell Biology. 217 (6), 2185-2204 (2018).</li><li>Anfossi, S., Fu, X., Nagvekar, R., Calin, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs,+Regulatory+Messengers+Inside+and+Outside+Cancer+Cells.">MicroRNAs, Regulatory Messengers Inside and Outside Cancer Cells.</a> Advances in Experimental Medicine and Biology. 1056, 87-108 (2018).</li><li>Khoshinani, H. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Involvement+of+miR-155/FOXO3a+and+miR-222/PTEN+in+acquired+radioresistance+of+colorectal+cancer+cell+line.">Involvement of miR-155/FOXO3a and miR-222/PTEN in acquired radioresistance of colorectal cancer cell line.</a> Japanese Journal of Radiology. 35 (11), 664-672 (2017).</li><li>Gao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNA-155+increases+colon+cancer+chemoresistance+to+cisplatin+by+targeting+forkhead+box+O3.">MicroRNA-155 increases colon cancer chemoresistance to cisplatin by targeting forkhead box O3.</a> Oncology Letters. 15 (4), 4781-4788 (2018).</li><li>Catanzaro, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+miR-107,+miR-181c+and+miR-29a-3p+Promote+Activation+of+Notch2+Signaling+in+Pediatric+High-Grade+Gliomas+(pHGGs).">Loss of miR-107, miR-181c and miR-29a-3p Promote Activation of Notch2 Signaling in Pediatric High-Grade Gliomas (pHGGs).</a> International Journal of Molecular Sciences. 18 (12), (2017).</li><li>Akbari Moqadam, F., Pieters, R., den Boer, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hunting+of+targets:+challenge+in+miRNA+research.">The hunting of targets: challenge in miRNA research.</a> Leukemia. 27 (1), 16-23 (2013).</li><li>Brown, R. A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Total+RNA+extraction+from+tissues+for+microRNA+and+target+gene+expression+analysis:+not+all+kits+are+created+equal.">Total RNA extraction from tissues for microRNA and target gene expression analysis: not all kits are created equal.</a> BMC Biotechnology. 18 (1), (2018).</li><li>Kim, Y. K., Yeo, J., Kim, B., Ha, M., Kim, V. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short+structured+RNAs+with+low+GC+content+are+selectively+lost+during+extraction+from+a+small+number+of+cells.">Short structured RNAs with low GC content are selectively lost during extraction from a small number of cells.</a> Molecular Cell. 46 (6), 893-895 (2012).</li><li>Schmittgen, T. D., Livak, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analyzing+real-time+PCR+data+by+the+comparative+C(T)+method.">Analyzing real-time PCR data by the comparative C(T) method.</a> Nature Protocols. 3 (6), 1101-1108 (2008).</li><li>Livak, K. J., Schmittgen, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+relative+gene+expression+data+using+real-time+quantitative+PCR+and+the+2(-Delta+Delta+C(T))+Method.">Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method.</a> Methods. 25 (4), 402-408 (2001).</li><li>Park, J. K., Seo, J. S., Lee, S. K., Chan, K. K., Kuh, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combinatorial+Antitumor+Activity+of+Oxaliplatin+with+Epigenetic+Modifying+Agents,+5-Aza-CdR+and+FK228,+in+Human+Gastric+Cancer+Cells.">Combinatorial Antitumor Activity of Oxaliplatin with Epigenetic Modifying Agents, 5-Aza-CdR and FK228, in Human Gastric Cancer Cells.</a> Biomolecules &amp; Therapeutics. 26 (6), 591-598 (2018).</li><li>Xia, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Downregulation+of+miR-301a-3p+sensitizes+pancreatic+cancer+cells+to+gemcitabine+treatment+via+PTEN.">Downregulation of miR-301a-3p sensitizes pancreatic cancer cells to gemcitabine treatment via PTEN.</a> American Journal of Translational Research. 9 (4), 1886-1895 (2017).</li><li>Lee, K. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+silencing+of+MicroRNA+miR-107+regulates+cyclin-dependent+kinase+6+expression+in+pancreatic+cancer.">Epigenetic silencing of MicroRNA miR-107 regulates cyclin-dependent kinase 6 expression in pancreatic cancer.</a> Pancreatology. 9 (3), 293-301 (2009).</li><li>van Tonder, A., Joubert, A. M., Cromarty, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Limitations+of+the+3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium+bromide+(MTT)+assay+when+compared+to+three+commonly+used+cell+enumeration+assays.">Limitations of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay when compared to three commonly used cell enumeration assays.</a> BMC Research Notes. 8, 47 (2015).</li><li>Wang, P., Henning, S. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Let+me+count+the+ways:+mechanisms+of+gene+regulation+by+miRNAs+and+siRNAs.">Let me count the ways: mechanisms of gene regulation by miRNAs and siRNAs.</a> Molecular Cell. 29 (1), 1-7 (2008).</li><li>Jin, Y., Chen, Z., Liu, X., Zhou, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+the+microRNA+targeting+sites+by+luciferase+reporter+gene+assay.">Evaluating the microRNA targeting sites by luciferase reporter gene assay.</a> Methods in Molecular Biology. , 117-127 (2013).</li><li>Ma, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gamma-synuclein+binds+to+AKT+and+promotes+cancer+cell+survival+and+proliferation.">Gamma-synuclein binds to AKT and promotes cancer cell survival and proliferation.</a> Tumour Biology. 37 (11), 14999-15005 (2016).</li><li>Pan, Z. Z., Bruening, W., Giasson, B. I., Lee, V. M., Godwin, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gamma-synuclein+promotes+cancer+cell+survival+and+inhibits+stress-+and+chemotherapy+drug-induced+apoptosis+by+modulating+MAPK+pathways.">Gamma-synuclein promotes cancer cell survival and inhibits stress- and chemotherapy drug-induced apoptosis by modulating MAPK pathways.</a> Journal of Biological Chemistry. 277 (38), 35050-35060 (2002).</li><li>Martinez-Sanchez, A., Murphy, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNA+Target+Identification-Experimental+Approaches.">MicroRNA Target Identification-Experimental Approaches.</a> Biology (Basel). 2 (1), 189-205 (2013).</li><li>Lee, E. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+profiling+identifies+microRNA+signature+in+pancreatic+cancer.">Expression profiling identifies microRNA signature in pancreatic cancer.</a> International Journal of Cancer. 120 (5), 1046-1054 (2007).</li><li>Nuovo, G. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+methodology+for+the+combined+in+situ+analyses+of+the+precursor+and+mature+forms+of+microRNAs+and+correlation+with+their+putative+targets.">A methodology for the combined in situ analyses of the precursor and mature forms of microRNAs and correlation with their putative targets.</a> Nature Protocols. 4 (1), 107-115 (2009).</li><li>Schmittgen, T. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+PCR+quantification+of+precursor+and+mature+microRNA.">Real-time PCR quantification of precursor and mature microRNA.</a> Methods. 44 (1), 31-38 (2008).</li><li>Diederichs, S., Haber, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual+role+for+argonautes+in+microRNA+processing+and+posttranscriptional+regulation+of+microRNA+expression.">Dual role for argonautes in microRNA processing and posttranscriptional regulation of microRNA expression.</a> Cell. 131 (6), 1097-1108 (2007).</li><li>Orellana, E. A., Kasinski, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulforhodamine+B+(SRB)+Assay+in+Cell+Culture+to+Investigate+Cell+Proliferation.">Sulforhodamine B (SRB) Assay in Cell Culture to Investigate Cell Proliferation.</a> Bio Protocol. 6 (21), (2016).</li><li>Lawrie, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs+in+hematological+malignancies.">MicroRNAs in hematological malignancies.</a> Blood Reviews. 27 (3), 143-154 (2013).</li><li>Quah, B. J., Warren, H. S., Parish, C. 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The authors have nothing to disclose.

Strategies for the determination of bona fide miRNA targets with the functions of a miRNA of interest are indispensable for the understanding of multiple roles of miRNAs. Identification of miRNA target genes can be a guideline for interpreting the cell signaling events modulated by miRNAs in a cell. An unveiling of functionally important target genes of miRNAs can provide the fundamental knowledge to develop a miRNA-based therapy in cancer.
Several methods such as microarrays, small RNA librar...

MicroRNAs (miRNAs) are the small regulatory RNAs that mainly modulate the process of translation and degradation of messenger RNAs (mRNAs) by reacting to the 3&#8217; untranslated regions (3&#8217; UTR) in bona fide target genes1. Expression of miRNAs can be regulated by transcriptional and post-transcriptional mechanisms. The imbalance of such regulatory mechanisms brings uncontrolled and distinctive miRNAs expression levels in numerous diseases including cancers2. A single miRNA can have multiple interactions with diverse mRNAs. Correspondingly, an individual mRNA can be controlled by various miRNAs. Therefore, intracellular signaling networks are intricately influenced by distinctively expressed miRNAs by which physiological disorders and diseases can be initiated and deteriorated2,3,4,5,6. Although the altered expression of miRNAs has been observed in various types of cancers, the molecular mechanisms that modulate the manners of cancer cells in conjunction with miRNAs are still largely unknown.
Accumulating evidence has been showing that the oncogenic or tumor-suppressive roles of miRNAs depend on the types of cancers. For example, by targeting forkhead box o3 (FOXO3), miR-155 promotes the cell proliferation, metastasis, and chemoresistance of colorectal cancer7,8. In contrast, the restriction of glioma cell invasion is induced by miR-107 via the regulation of neurogenic locus notch homolog protein 2 (NOTCH2) expression9. The assessment of miRNA-target interactions in connection with miRNA functions is an indispensable part to better understand how miRNAs regulate various biological processes in both healthy and diseased states10. In addition, the discovery of bona fide target(s) of miRNAs can further provide a fine-tuned strategy for a miRNA-based therapy with various anti-cancer drugs. However, the main challenge in the field of miRNAs is the identification of direct targets of miRNAs. Here, detailed methods are presented as reproducible experimental approaches for the miRNA target gene determination. Successful experimental design for the miRNA target identification involves various steps and considerations (Figure 1). Comparison of mature miRNA levels in tumor cells and normal cells can be one of the common procedures to select a miRNA of interest (Figure 1A). The functional study of a selected miRNA to detect the effects of a miRNA on cell proliferation is important to narrow down the list of best potential candidate targets of a miRNA of interest (Figure 1B). Based on the experimentally validated functions of miRNAs, a systematic review of literature and database in company with a miRNA target prediction program is required to search the most relevant information on gene functions (Figure 1C). The identification of real target genes of a miRNA of interest can be achieved by implementing experiments such as the luciferase assay along with the cloning of 3&#8217; UTR of a gene, real-time PCR, and western blotting (Figure 1D). The goal of the current protocol is to provide comprehensive methods of key experiments, the probe-based real-time polymerase chain reaction (PCR), sulforhodamine B (SRB) assay following a miRNA mimic transfection, dose-response curve generation, and luciferase assay along with the cloning of 3&#8217; UTR of a gene. The current protocol can be useful for a better understanding of the functions of individual miRNAs and the implication of a miRNA in cancer therapy.

<table>
	<tbody>
		<tr>
			<td>15 mL conical tube</td>
			<td>SPL Life Sciences</td>
			<td>50015</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well plate</td>
			<td>Thermo Scientific</td>
			<td>142475</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL conical tube</td>
			<td>SPL Life Sciences</td>
			<td>50050</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plate</td>
			<td>Falcon</td>
			<td>353046</td>
			<td></td>
		</tr>
		<tr>
			<td>6X DNA loading dye</td>
			<td>Real Biotech Corporation</td>
			<td>RD006</td>
			<td>1 mL</td>
		</tr>
		<tr>
			<td>8-cap strip</td>
			<td>Applied Biosystems</td>
			<td>N8010535</td>
			<td>For cDNA synthesis</td>
		</tr>
		<tr>
			<td>8-tube strip</td>
			<td>Applied Biosystems</td>
			<td>N8010580</td>
			<td>For cDNA synthesis</td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>Falcon</td>
			<td>353072</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma</td>
			<td>A6283-1L</td>
			<td>1 L</td>
		</tr>
		<tr>
			<td>Agarose A</td>
			<td>Bio Basic</td>
			<td>D0012</td>
			<td>500 g</td>
		</tr>
		<tr>
			<td>Alkaline phosphatase</td>
			<td>New England Biolabs</td>
			<td>M0290S</td>
			<td>10,000 U/mL</td>
		</tr>
		<tr>
			<td>Ampicillin</td>
			<td>Bio basic Canada Inc</td>
			<td>AB0028</td>
			<td>25 g</td>
		</tr>
		<tr>
			<td>AriaMx 96 tube strips</td>
			<td>Agilent Technologies</td>
			<td>401493</td>
			<td>For real time PCR</td>
		</tr>
		<tr>
			<td>AriaMx real-time PCR system</td>
			<td>Agilent Technologies</td>
			<td>G8830A</td>
			<td>qPCR amplification, detection, and data analysis</td>
		</tr>
		<tr>
			<td>AsiSI</td>
			<td>New England Biolabs</td>
			<td>R0630</td>
			<td>10,000 units/mL</td>
		</tr>
		<tr>
			<td>CAPAN-1 cells</td>
			<td>ATCC</td>
			<td>HTB-79</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture hood</td>
			<td>Labtech</td>
			<td></td>
			<td>Model: LCB-1203B-A2</td>
		</tr>
		<tr>
			<td>Counting chambers with V-slash</td>
			<td>Paul Marienfeld</td>
			<td>650010</td>
			<td>Cells counter</td>
		</tr>
		<tr>
			<td>CutSmart buffer</td>
			<td>New England Biolabs</td>
			<td>B7204S</td>
			<td>10X concentration</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco</td>
			<td>11965-092</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>DNA gel extraction kit</td>
			<td>Bionics</td>
			<td>DN30200</td>
			<td>200 prep</td>
		</tr>
		<tr>
			<td>DNA ladder</td>
			<td>NIPPON Genetics EUROPE</td>
			<td>MWD1</td>
			<td>1 Kb ladder</td>
		</tr>
		<tr>
			<td>DNase I</td>
			<td>Invitrogen</td>
			<td>18068015</td>
			<td>100 units</td>
		</tr>
		<tr>
			<td>Dual-luciferase reporter assay system</td>
			<td>Promega</td>
			<td>E1910</td>
			<td>100 assays</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Gibco</td>
			<td>26140-079</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>HIT competent cells</td>
			<td>Real Biotech Corporation(RBC)</td>
			<td>RH617</td>
			<td>Competent cells</td>
		</tr>
		<tr>
			<td>HPNE cells</td>
			<td>ATCC</td>
			<td>CRL-4023</td>
			<td></td>
		</tr>
		<tr>
			<td>LB agar broth</td>
			<td>Bio Basic</td>
			<td>SD7003</td>
			<td>250 g</td>
		</tr>
		<tr>
			<td>Lipofectamine 2000</td>
			<td>Invitrogen</td>
			<td>11668-027</td>
			<td>0.75 mL</td>
		</tr>
		<tr>
			<td>Lipofectamine RNAiMax</td>
			<td>Invitrogen</td>
			<td>13778-075</td>
			<td>0.75 mL</td>
		</tr>
		<tr>
			<td>Luminometer</td>
			<td>Promega</td>
			<td></td>
			<td>Model: E5311</td>
		</tr>
		<tr>
			<td>Microcentrifuge tube</td>
			<td>Eppendorf</td>
			<td>22431021</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>TECAN</td>
			<td></td>
			<td>Infinite F50</td>
		</tr>
		<tr>
			<td>miRNA control mimic</td>
			<td>Ambion</td>
			<td>4464058</td>
			<td>5 nmole</td>
		</tr>
		<tr>
			<td>miRNA-107 mimic</td>
			<td>Ambion</td>
			<td>4464066</td>
			<td>5 nmole</td>
		</tr>
		<tr>
			<td>miRNeasy Mini Kit</td>
			<td>Qiagen</td>
			<td>217004</td>
			<td>50 prep</td>
		</tr>
		<tr>
			<td>Mupid-2plus (electrophoresis system)</td>
			<td>TaKaRa</td>
			<td></td>
			<td>Model: AD110</td>
		</tr>
		<tr>
			<td>NotI</td>
			<td>New England Biolabs</td>
			<td>R3189</td>
			<td>20,000 units/mL</td>
		</tr>
		<tr>
			<td>Oligo explorer program</td>
			<td>GeneLink</td>
			<td></td>
			<td>For primer design</td>
		</tr>
		<tr>
			<td>Optical tube strip caps (8X Strip)</td>
			<td>Agilent Technologies</td>
			<td>401425</td>
			<td>For real time PCR</td>
		</tr>
		<tr>
			<td>Opti-MEM</td>
			<td>Gibco</td>
			<td>31985-070</td>
			<td>500 Ml</td>
		</tr>
		<tr>
			<td>PANC-1 cells</td>
			<td>ATCC</td>
			<td>CRL-1469</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/streptomycin</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>Phosphate buffer saline</td>
			<td>Gibco</td>
			<td>14040117</td>
			<td>1000 mL</td>
		</tr>
		<tr>
			<td>Plasmid DNA miniprep S&#38; V kit</td>
			<td>Bionics</td>
			<td>DN10200</td>
			<td>200 prep</td>
		</tr>
		<tr>
			<td>PrimeSTAR GXL DNA polymerase</td>
			<td>TaKaRa</td>
			<td>R050A</td>
			<td>250 units</td>
		</tr>
		<tr>
			<td>Shaker</td>
			<td>TECAN</td>
			<td></td>
			<td>Shaking platform</td>
		</tr>
		<tr>
			<td>Shaking incubator</td>
			<td>Labtech</td>
			<td></td>
			<td>Model: LSI-3016A</td>
		</tr>
		<tr>
			<td>Sigmaplot 14 software</td>
			<td>Systat Software Inc</td>
			<td></td>
			<td>For dose-response curve generation</td>
		</tr>
		<tr>
			<td>Sulforhodamine B powder</td>
			<td>Sigma</td>
			<td>S1402-5G</td>
			<td>5 g</td>
		</tr>
		<tr>
			<td>SYBR green master mix</td>
			<td>Smobio</td>
			<td>TQ12001805401-3</td>
			<td>Binding fluorescent dye for dsDNA</td>
		</tr>
		<tr>
			<td>T4 DNA ligase</td>
			<td>TaKaRa</td>
			<td>2011A</td>
			<td>25,000 U</td>
		</tr>
		<tr>
			<td>TaqMan master mix</td>
			<td>Applied Biosystems</td>
			<td>4324018</td>
			<td>200 reactions, no AmpErase UNG</td>
		</tr>
		<tr>
			<td>TaqMan microRNA assay (hsa-miR-107)</td>
			<td>Applied Biosystems</td>
			<td>4427975</td>
			<td>Assay ID: 000443 (50RT, 150 PCR rxns)</td>
		</tr>
		<tr>
			<td>TaqMan microRNA assay (hsa-miR-301)</td>
			<td>Applied Biosystems</td>
			<td>4427975</td>
			<td>Assay ID: 000528 (50RT, 150 PCR rxns)</td>
		</tr>
		<tr>
			<td>TaqMan miR RT kit</td>
			<td>Applied Biosystems</td>
			<td>4366597</td>
			<td>1000 reactions</td>
		</tr>
		<tr>
			<td>Thermo CO2 incubator (BB15)</td>
			<td>ThermoFisher Scientific</td>
			<td></td>
			<td>37 &#176;C and 5% CO2 incubation</td>
		</tr>
		<tr>
			<td>Trichloroacetic acid</td>
			<td>Sigma</td>
			<td>91228-100G</td>
			<td>100 g</td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma</td>
			<td>T4661-100G</td>
			<td>100 g</td>
		</tr>
		<tr>
			<td>Ultrapure water</td>
			<td>Invitrogen</td>
			<td>10977-015</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>Veriti 96 well thermal cycler</td>
			<td>Applied Biosystems</td>
			<td></td>
			<td>For amplification of DNA (or cDNA)</td>
		</tr>
		<tr>
			<td>XhoI</td>
			<td>New England Biolabs</td>
			<td>R0146</td>
			<td>20,000 units/mL</td>
		</tr>
	</tbody>
</table>

an in vitro protocol for evaluating microrna levels, functions, and associated target genes in tumor cells

MicroRNAs (miRNAs) are small regulatory RNAs which are recognized to modulate numerous intracellular signaling pathways in several diseases including cancers. These small regulatory RNAs mainly interact with the 3&#8217; untranslated regions (3&#8217; UTR) of their target messenger RNAs (mRNAs) ultimately resulting in the inhibition of decoding processes of mRNAs and the augmentation of target mRNA degradations. Based on the expression levels and intracellular functions, miRNAs are able to serve as regulatory factors of oncogenic and tumor-suppressive mRNAs. Identification of bona fide target genes of a miRNA among hundreds or even thousands of computationally predicted targets is a crucial step to discern the roles and basic molecular mechanisms of a miRNA of interest. Various miRNA target prediction programs are available to search possible miRNA-mRNA interactions. However, the most challenging question is how to validate direct target genes of a miRNA of interest. This protocol describes a reproducible strategy of key methods on how to identify miRNA targets related to the function of a miRNA. This protocol presents a practical guide on step-by-step procedures to uncover miRNA levels, functions, and related target mRNAs using the probe-based real-time polymerase chain reaction (PCR), sulforhodamine B (SRB) assay following a miRNA mimic transfection, dose-response curve generation, and luciferase assay along with the cloning of 3&#8217; UTR of a gene, which is necessary for proper understanding of the roles of individual miRNAs.

Successful and accurate confirmation of miRNA levels is important for the interpretation of data by which the classification of miRNAs is possible based on the anticipated roles of miRNAs in the development and progression of a disease. The levels of miRNA-107 and miRNA-301 were measured in three pancreas cell lines using the probe-based quantitative PCR. The synthesis of cDNAs of both a specific miRNA and a reference gene in the same reaction can increase the reproducibility of data. PANC-1 and CAPAN-1 are human pancrea...

Watch this Scientific Journal Video about An In Vitro Protocol for Evaluating MicroRNA Levels, Functions, and Associated Target Genes in Tumor Cells at JoVE.com

An In Vitro Protocol for Evaluating MicroRNA Levels, Functions, and Associated Target Genes in Tumor Cells

This protocol uses a probe-based real-time polymerase chain reaction (PCR), a sulforhodamine B (SRB) assay, 3&#8217; untranslated regions (3&#8217; UTR) cloning, and a luciferase assay to verify the target genes of a miRNA of interest and to understand the functions of miRNAs.

MicroRNAs (miRNAs) are small regulatory RNAs which are recognized to modulate numerous intracellular signaling pathways in several diseases including ...

To access neural microRNA target interactions with MicroRNA functions is critical to understand how MicroRNAs regulate various biological processes in both healthy and diseased states. This protocol describes the reproduce through strategy to identify microRNA targets and the functional microRNAs as the validation of direct target of microRNAs is challenging. Our protocol can provide insights on the function of individual microRNAs and the implication of a microRNA in cancer therapy.Calculation of the half-maximal inhibitory concentration is an important method, not only for microRNA studies but for the efficacious evaluation of other anti-cancer drugs. Our protocol will be helpful to new researchers since we described the fundamental method to understand the level of microRNAs in a cell. To begin the protocol, count the cells with the cell counter.Plate the cells in a 96 well plate. The next day, prepare a set of transfection mixtures to transfect the cells in several final concentrations of microRNA control mimic, and microRNA-107 mimic. From a stock of 25 micromolar microRNA control mimic, or microRNA-107 mimic, dilute and add control mimic or microRNA-107 mimic in the reduced serum media along with the transfection reagent in microcentrifuge tubes.Gently mix the oligo-containing mixtures using a micropipette. After a 10 minute incubation in the cell culture hood, gently mix the oligo-containing mixtures again, and then add 50 microliters of the mixtures into each well. Keep the transfected cells in a cell culture incubator.Carefully aspirate the cell culture media in each well of the plate and promptly fill 100 microliters of 10%trichloroacetic acid, or TCA, into each well. Keep the plate containing 10%TCA at four degrees Celsius for one hour. Next, wash the plate several times by submerging it into a tub with tap water.Remove excess water from inside of the wells by tapping the plate until there is no water left, and dry the plate. Pipette 50 microliters of 0.4%SRB solution into each well including the blank wells. Gently shake the plate until the 0.4%SRB solution evenly covers the bottom of the wells.Then, incubate the plate for 40 to 60 minutes. After incubation, wash the plate with 1%acetic acid until the unbound dye is totally washed away. Pipette 100 microliters of 10 millimolar Tris base solution into the corresponding wells, including blank wells.Keep the plate on a shaker for 10 minutes. Measure the absorbance at 492 nanometers. Calculate the percentage of average absorbance and the standard deviation of each group using absorbance values of the SRB assay.Import the raw data including treatment concentrations, average absorbance, and standard deviation into the software by vertically aligning the data. Click the Create Graph tab and choose the Simple Scatter Error Bars. Select worksheet columns as Symbol values, and click next.In the Data Format panel, select X-Y pairs and click next. Select corresponding data columns in the Select Data panel. Click finish to create the plot.Double-click on the X-axis to modify the type of scale in the scaling of axis. Change the type of scale from linear to log. Modify the start and end range number to 0.01 and 200, respectively.Right-click on any scatter plot, choose Curve Fit, and go to the subcategory User Defined. Select dose response curve. Click the next buttons, and then click finish.Go to the report tab, and then check the n, k, and R values. Run the PCR as detailed in the accompanying text protocol. Then move on to double-digestion by combining the reaction mixtures, including the restriction enzymes Exo1 and Not1 one in a tube.Incubate the mixtures for three to four hours in a 37 degree Celsius water bath. Run the double-digested products on a 1%agarose gel. Then cut the bands under UV light.Purify the double-digested PCR products and luciferase vectors from the excised bands. Continue with ligation of the PCR products into the luciferase vectors by preparing 20 microliters of ligation reaction mixtures including the DNA ligase. Briefly centrifuge the tube for 10 to 15 seconds.Incubate the ligation at 16 degrees Celsius overnight using a thermal cycler. The next day, perform transformation by adding the ligation mixtures into the tube containing competent cells. Gently tap the tube and keep it on ice for 20 minutes.Quickly and gently transfer the tube to a heat block at 42 degrees Celsius for 30 seconds to one minute. Following heat shock, place the tube on ice for 20 minutes. Spread competent cells on an LB agar plate.Grow competent cells in an incubator at 37 degrees Celsius overnight. The following day, pick an individual colony and resuspend E.coli in one of the 8-strip tubes containing ultrapure water, and repeat this step to resuspend E.coli from four to eight randomly-selected colonies. Transfer 25 microliters of E.coli suspension into another set of 8-strip tubes.Perform the colony PCR using the E.coli suspension. Prepare the luciferase assay in a 24 well plate. Add one to two times ten to the four cells in a 500 microliter cell culture media for each well.After overnight incubation, transfect 50 nanograms of luciferase vectors into the cells with control mimic or a specific microRNA mimic using a transfection reagent. The next day, wash the inside of the wells twice using phosphate buffered saline. Apply 200 microliters of lysis reagent into the wells and sufficiently carry out cell lysis before measuring the luciferase activity.Keep the plate shaking for at least 15 minutes. Transfer five to 10 microliters of cell lysate into the new tube, and add 100 microliters of reagent one and immediately mix the solution by pipetting. Then read the firefly luciferase activity using illuminometer for 10 to 15 seconds.Add 100 microliters of reagent two in the same tube and then mix by pipetting twice. Finally, read the renilla luciferase activity for 10 to 15 seconds using illuminometer. RTPCR shows a significant reduction of microRNA-107 and PANC-1 and CAPAN-1 cells compared with HPNE cells.The levels of microRNA-301 were significantly upregulated in PANC-1 and CAPAN-1 cells, compared with HPNE cells. The SRB assay in this study clearly demonstrates that the proliferation of PANC-1 cells decreased following a microRNA-107 mimic transfection. The screening of 11 potential predicted targets of microRNA-107 clearly shows that only synuclein gamma, or SNCG, a positive regulator of tumor cell growth directly interacts with microRNA-107 and PANC-1 cells, indicating that microRNA-107 can negatively regulate the proliferation of PANC-1 cells by modulating the SNCG expression.Adult cell proliferation assays that use the tetra hydroleum-based entity and CFSE are applicable to screen the effect of such as microRNA mimics, depending on the cell types. Based on the experimentally-validated function of microRNAs, a systematic review of database and target prediction program is required to narrow down the list of candidate targets before luciferase assays. For the evaluation of combination efficiency of microRNAs with anti-cancer drugs, it is advantageous to calculate adjusted IC values based on our protocol for the assessment of combination index.

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JoVE Journal

Genetics

8.1K visualizações.  Hallym University. Acessar interações de alvo de microRNA neural com funções de MicroRNA é fundamental para entender como as MicroRNAs regulam vários processos biológicos em estados saudáveis e doentes. Este protocolo descreve a reprodução através da estratégia para identificar alvos de microRNA e as microRNAs funcionais como a validação do alvo direto das microRNAs é desafiadora. Nosso protocolo pode fornecer insights sobre a função das microRNAs individuais e a implicação de um microRNA na ...