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Method Article
This protocol describes xenograft and orthotopic mouse models of human thyroid tumorigenesis as a platform to test microRNA-based inhibitor treatments. This approach is ideal to study the function of non-coding RNAs and their potential as new therapeutic targets.
MicroRNAs (miRNAs) are important regulators of gene expression through their ability to destabilize mRNA and inhibit translation of target mRNAs. An ever-increasing number of studies have identified miRNAs as potential biomarkers for cancer diagnosis and prognosis, and also as therapeutic targets, adding an extra dimension to cancer evaluation and treatment. In the context of thyroid cancer, tumorigenesis results not only from mutations in important genes, but also from the overexpression of many miRNAs. Accordingly, the role of miRNAs in the control of thyroid gene expression is evolving as an important mechanism in cancer. Herein, we present a protocol to examine the effects of miRNA-inhibitor delivery as a therapeutic modality in thyroid cancer using human tumor xenograft and orthotopic mouse models. After engineering stable thyroid tumoral cells expressing GFP and luciferase, cells are injected into nude mice to develop tumors, which can be followed by bioluminescence. The in vivo inhibition of a miRNA can reduce tumor growth and upregulate miRNA gene targets. This method can be used to assess the importance of a determined miRNA in vivo, in addition to identifying new therapeutic targets.
Thyroid cancer is an endocrine malignancy with an increasing incidence, although in general terms it has a good outcome1. Nevertheless, some patients develop aggressive forms of the disease that are untreatable and the molecular bases are poorly understood2.
miRNAs are 22-nucleotide-long non-coding RNAs that regulate gene expression in many tissues, typically by base-pair binding to the 3' untranslational region (3’UTR) of target messenger RNAs (mRNAs), triggering mRNA degradation or translational repression3,4. There is increasing evidence demonstrating that the deregulation of microRNA expression is a hallmark of cancer, as these molecules modulate proliferative signaling, migration, invasion and metastasis, and can provide resistance to apoptosis5,6. In recent years, many studies have identified miRNAs as potential biomarkers for cancer diagnosis and prognosis as well as therapeutic targets7, providing a new dimension to cancer evaluation and treatment.
miRNAs have taken center stage in human molecular oncology as key drivers of human thyroid neoplasms8,9,10,11,12. Among the miRNAs up-regulated, miR-146b is highly overexpressed in Papillary Thyroid Carcinoma (PTC) tumors and was shown to significantly increase cell proliferation, and to be associated with aggressiveness and dismal prognosis6,12,13,14,15. Furthermore, miR-146b regulates several thyroid genes involved in differentiation12, and also important tumor suppressor genes such as PTEN16 and DICER117. Despite their importance in cancer biology, miRNA-based cancer therapy is still in its early stages, and very few studies have addressed thyroid cancer - the most frequent of the endocrine tumors18. Here we describe a protocol using two different mouse models with human-derived tumors, in which the administration of a synthetic miRNA-inhibitor (antagomiR) that specifically inhibits a cellular miRNA can block tumor growth. We first used a common xenograft model, and the local intratumor administration of an antagomiR decreased tumor growth measured as a reduction in tumor bioluminescence16. Because the establishment of robust mouse models mimicking human tumor progression is essential to develop unique therapeutic approaches, orthotopic implantation of primary human tumors is a more valuable platform for clinical validation of new drugs than subcutaneous implantation models. Thus, in order to better assess the therapeutic potential of the antagomiR, we used an orthotopic mouse model with systemic delivery in the blood stream, obtaining the same results.
Animal experimentation was performed in compliance with the European Community Law (86/609/EEC) and the Spanish law (R.D. 1201/2005), with approval of the Ethics Committee of the Consejo Superior de Investigaciones Científicas (CSIC, Spain).
1. Flank inoculation of cells and intratumoral antagomiR treatment
2. Thyroid orthotopic inoculation of cells and systemic antagomiR treatment
We used two different mice models to determine whether the neutralization of a miRNA could suppress tumor growth. Accordingly, human tumor thyroid Cal62-luc cells were subcutaneously injected into the flanks of nude mice to generate a xenograph model. After two weeks, tumors were established and could be measured with calipers. At that time point, mice were injected intratumorally with the miR-146b-inhibitor, or an appropriate control, and tumor volume was followed for a further two weeks (Figure 1A<...
This paper describes a method for studying the in vivo function of a miRNA in order to better understand its role in tumor initiation and progression, and its potential as a therapeutic target in thyroid cancer. The tumor xenograft models here described are based on the use of cells that can be tracked by their bioluminescence signal, permitting the measurement of tumor growth in vivo under the influence of a treatment. In addition, we describe the use of a miRNA-based treatment for thyroid cancer, which is currently in ...
The authors have nothing to disclose.
We are grateful to Raquel Arocha Riesco for her assistance with the treatment and care of mice. We thank Dr. J. Blanco (Catalonian Institute for Advance Chemistry-CSIC) and Dr E. Mato (Institut de Reserca de l’Hospital de la Santa Creu i Sant Pau) Barcelona (Spain) for gifting the CMV-Firefly luc- IRES-EGFP and Cal62-Luc cells, respectively. Funding: SAF2016-75531-R (MICIU), Fondo Europeo de Desarrollo Regional FEDER, B2017/BMD-3724 (Comunidad de Madrid), and GCB14142311CRES (Fundación Española contra el Cáncer, AECC).
Name | Company | Catalog Number | Comments |
AntagomiR: mirVana miRNA inhibitor | Thermo Fisher | 4464088 | In Vivo Ready |
Basement Membrane Matrix: Matrigel Basement Membrane Matrix High Concentration | Corning | #354248 | |
DICER antibody | Abcam | ab14601 | IHQ: 1/100 |
In vivo delivery reagent: Invivofectamine 3.0 Reagent | Thermo Fisher | IVF3005 | |
In vivo imaging software: IVIS-Lumina II Imaging System | Caliper Life Sciences | ||
Negative control: mirVana miRNA Inhibitor, Negative Control #1 | Thermo Fisher | 4464077 | In Vivo Ready |
PCNA antibody | Abcam | ab92552 | WB: 1/2,000 |
PTEN antibody | Santa Cruz | sc-7974 | WB: 1/1,000 |
XenoLight D-Luciferin - K+ Salt Bioluminescent Substrate | PerkinElmer | 122799 | Diluted in PBS |
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