Name: a melanoma patient-derived xenograft model
Uploaded: 2019-05-20T14:30:00
Description: Watch this Scientific Journal Video about A Melanoma Patient-Derived Xenograft Model Video at JoVE.com

The authors thank the Wistar Institute Animal Facility, Microscopy Facility, Histotechnology Facility, and Research Supply Center. This study was funded in part by grants from the U54 (CA224070-01), SPORE (CA174523), P01 (CA114046-07), the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation, and the Melanoma Research Foundation.

The following animal protocols follow the guidelines of The Wistar Institute&#8217;s humane ethics committee and animal care guidelines.
1. Melanoma tumor tissue collection
<ol>
	<li>Collect tumor tissue (termed passage 0) from melanoma patients by one of the following surgery or biopsy methods.
	<ol>
		<li>For surgical excision tissue, maintain a minimum of 1 g of tissue (resect metastases and primary lesions) in transport storage media (RPMI 1640 + 0.1% fungizone + 0.2% gentamicin) at 4 &#...

<ol>
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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=Recovery+of+phospho-ERK+activity+allows+melanoma+cells+to+escape+from+BRAF+inhibitor+therapy.">Recovery of phospho-ERK activity allows melanoma cells to escape from BRAF inhibitor therapy.</a> British Journal Of Cancer. 102 (12), 1724-1730 (2010).</li><li>Long, G. V., 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=Long-Term+Outcomes+in+Patients+With+BRAF+V600-Mutant+Metastatic+Melanoma+Who+Received+Dabrafenib+Combined+With+Trametinib.">Long-Term Outcomes in Patients With BRAF V600-Mutant Metastatic Melanoma Who Received Dabrafenib Combined With Trametinib.</a> Journal of Clinical Oncology. 36 (7), 667-673 (2018).</li><li>Hidalgo, 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=Patient-derived+xenograft+models:+an+emerging+platform+for+translational+cancer+research.">Patient-derived xenograft models: an emerging platform for translational cancer research.</a> Cancer Discovery. 4 (9), 998-1013 (2014).</li><li>Hausser, H. J., Brenner, R. 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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=Development+of+three+human+small+cell+lung+cancer+models+in+nude+mice.">Development of three human small cell lung cancer models in nude mice.</a> Recent Results In Cancer Research. 97, 77-86 (1985).</li><li>Izumchenko, E., 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=Patient-derived+xenografts+effectively+capture+responses+to+oncology+therapy+in+a+heterogeneous+cohort+of+patients+with+solid+tumors.">Patient-derived xenografts effectively capture responses to oncology therapy in a heterogeneous cohort of patients with solid tumors.</a> Annals of Oncology. 28 (10), 2595-2605 (2017).</li><li>Shi, 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=Acquired+resistance+and+clonal+evolution+in+melanoma+during+BRAF+inhibitor+therapy.">Acquired resistance and clonal evolution in melanoma during BRAF inhibitor therapy.</a> Cancer Discovery. 4 (1), 80-93 (2014).</li><li>Monsma, D. 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We have herein described generating PDX models of melanoma with patient tissue derived from primary and metastatic tumors, core biopsies, and FNAs. When directly engrafted into NSG mice, tumors present similar morphologic, genomic, and biologic properties to those observed in the patient. In the case when only a small quantity of tissue is available to investigators, as often occurs with FNAs, the PDX technique allows for the expansion of the tumor tissue for DNA, RNA, and protein characterization, as well as for therapy...

Preclinical models are critical for all aspects of translational cancer research, including disease characterization, discovery of actionable vulnerabilities unique to cancer versus normal cells, and the development of efficacious therapies that exploit these vulnerabilities to increase the overall survival of patients. In the melanoma field, tens of thousands of cell line models have been heavily utilized for drug screening, with &#62;4,000 contributed by our group alone (WMXXX series). These cell line models were derived from melanoma patients with various forms of cutaneous melanoma (i.e., acral, uveal, and superficial spreading) and diverse genotypes (i.e., BRAFV600-mutant and neuroblastoma RAS viral oncogene homolog [NRASQ61R-mutant]), which span the spectrum of disease present in the clinic1,2.
Unequivocally, the most successful, targeted therapy strategy in the melanoma field has emerged from 1) the genomic characterization of patients&#8217; tumors identifying BRAF mutations in ~50% of melanomas3 and from 2) preclinical investigation leveraging melanoma cell line models4. The BRAF/MEK inhibitor combination was Food and Drug Administration (FDA)-approved in 2014 for the treatment of patients whose melanomas harbor activating BRAFV600E/K mutations and boasts a &#62;75% response rate5. Despite this initial efficacy, resistance rapidly arises in nearly every case due to multifarious intrinsic and acquired resistance mechanisms and intratumoral heterogeneity. Unfortunately, cell line models do not recapitulate representative biological heterogeneity when grown in two-dimensional culture in plastic vessels, which masks their clinically predictive potential when investigators attempt to experimentally determine therapies that might be effective in patients with a specific form or genotype of melanoma6. Understanding how to best model patient intratumoral heterogeneity will allow investigators to better develop therapeutic modalities that can kill therapy-resistant subpopulations that drive failure to current standard-of-care therapies.
Paramount to the limited predictive value of cell line models is how they are initially established. Irreversible alterations occur in the tumor clonal landscape when a single-cell suspension of a patients&#8217; tumor is grown on two-dimensional, plastic tissue culture vessels, including changes in proliferative and invasive potential, the elimination of specific subpopulations, and the alteration of genetic information7. Xenografts into mice of these melanoma cell line models represent the most frequently used in vivo platform for preclinical studies; however, this strategy also suffers from the poor recapitulation of complex tumor heterogeneity observed clinically. To overcome this shortcoming, there has been a growing interest in incorporating more sophisticated preclinical models of melanoma, including the PDX model. PDX models have been utilized for &#62;30 years, with seminal studies in lung cancer patients demonstrating concordance between the patients&#39;&#160;response to cytotoxic agents and the response of the PDX model derived from the same patient8. Recently, there has been a drive to utilize PDX models as the tool of choice for preclinical investigations both in the industry and in academic centers. PDX models, because of their superior recapitulation of tumor heterogeneity in human patients, are more clinically relevant to use in therapy optimization efforts than cell line xenografts9. In melanoma, there are immense hurdles that blunt the therapeutic management of advanced disease10. Clinically relevant PDX models have been used to model clinical resistance and identify therapeutic strategies with clinically available agents to treat therapy-resistant tumors11,12. Briefly, the protocol presented here to generate PDX models requires the subcutaneous implantation of fresh tissue from primary or metastatic melanomas (collected by biopsy or surgery) into NOD/scid/IL2-receptor null (NSG) mice. Different variations in methodological approach are used by different groups; however, a fundamental core exists13.

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			<td height="40" style="height:40px;width:352px;">1 M Hepes</td>
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			<td style="width:344px;">Cat # H0887-100ML</td>
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			<td>Invitrogen</td>
			<td>Cat # 15140163</td>
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			<td>MED</td>
			<td>Cat # MT21-023-CV</td>
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			<td height="61" style="height:62px;">2.5% Trypsin&#160;</td>
			<td>SIGMA-ALDRICH CORPORATION</td>
			<td>Cat # T4549-100ML</td>
			<td>10 mL aliquots stored at &#8211;20oC</td>
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			<td height="40" style="height:40px;">BSA</td>
			<td>SIGMA-ALDRICH CORPORATION</td>
			<td>Cat # A9418-500G</td>
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			<td>Fisher Scientific</td>
			<td>Cat# 50-118-0313</td>
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			<td>Worthington&#160;</td>
			<td>Cat #4189</td>
			<td>make up in HBSS-/- from Collagenase IV powder stock (Worthington #4189, u/mg indicated on bottle and varies with each lot); freeze 1</td>
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			<td height="40" style="height:40px;">DMSO</td>
			<td>SIGMA-ALDRICH CORPORATION</td>
			<td>Cat # C6295-50ML</td>
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			<td height="40" style="height:40px;">DNase</td>
			<td>SIGMA-ALDRICH CORPORATION</td>
			<td>Cat # D4527</td>
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			<td height="40" style="height:40px;">EGTA (ethylene glycol bis(2-aminoethyl ether)-N,N,N&#8217;N&#8217;-tetraacetic acid)</td>
			<td>Merck</td>
			<td>Cat # 324626.25</td>
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			<td>INVITROGEN LIFE TECHNOLOGIES</td>
			<td>Cat # 16000-044</td>
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			<td height="40" style="height:40px;">Fungizone</td>
			<td>INVITROGEN LIFE TECHNOLOGIES</td>
			<td>Cat # 15290-018</td>
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			<td height="40" style="height:40px;">Gentamicin</td>
			<td>FISHER SCIENTIFIC</td>
			<td>Cat # BW17518Z</td>
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			<td height="40" style="height:40px;">Isoflurane</td>
			<td>HENRY SCHEIN ANIMAL HEALTH</td>
			<td>Cat # 050031</td>
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			<td height="40" style="height:40px;">Leibovitz&#39;s L15 media&#160;</td>
			<td>Invitrogen</td>
			<td>Cat # 21083027</td>
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			<td height="40" style="height:40px;">Matrigel</td>
			<td>Corning</td>
			<td>Cat # 354230</td>
			<td>Artificial extracellular matrix</td>
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			<td height="21" style="height:21px;">Meloxicam</td>
			<td>HENRY SCHEIN ANIMAL HEALTHRequisition # ::Henry Schein</td>
			<td>Cat # 025115</td>
			<td>1-5mg/kg, as painkiller</td>
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			<td height="21" style="height:21px;">NOD/SCID/IL2-receptor null (NSG) Mice</td>
			<td>The Wistar Institute, animal facility</td>
			<td></td>
			<td>breeding</td>
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			<td height="21" style="height:21px;">PVA (polyvinyl alcohol)</td>
			<td>SIGMA-ALDRICH CORPORATION</td>
			<td>Cat # P8136-250G</td>
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			<td height="21" style="height:21px;">RPMI 1640 Medium (Mod.) 1X with L-Glutamine</td>
			<td>Fisher Scientific</td>
			<td>Cat# MT10041CM</td>
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			<td>Feather</td>
			<td>Cat # 2976-22</td>
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			<td height="21" style="height:21px;">Virkon</td>
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			<td>Cat # 222-01-06</td>
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			<td height="21" style="height:21px;">Wound clips</td>
			<td>MikRon</td>
			<td>Cat #427631</td>
			<td></td>
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a melanoma patient-derived xenograft model

Accumulating evidence suggests that molecular and biological properties differ in melanoma cells grown in traditional two-dimensional tissue culture vessels versus in vivo in human patients. This is due to the bottleneck selection of clonal populations of melanoma cells that can robustly grow in vitro in the absence of physiological conditions. Further, responses to therapy in two-dimensional tissue cultures overall do not faithfully reflect responses to therapy in melanoma patients, with the majority of clinical trials failing to show the efficacy of therapeutic combinations shown to be effective in vitro. Although xenografting of melanoma cells into mice provides the physiological in vivo context absent from two-dimensional tissue culture assays, the melanoma cells used for engraftment have already undergone bottleneck selection for cells that could grow under two-dimensional conditions when the cell line was established. The irreversible alterations that occur as a consequence of the bottleneck include changes in growth and invasion properties, as well as the loss of specific subpopulations. Therefore, models that better recapitulate the human condition in vivo may better predict therapeutic strategies that effectively increase the overall survival of patients with metastatic melanoma. The patient-derived xenograft (PDX) technique involves the direct implantation of tumor cells from the human patient to a mouse recipient. In this manner, tumor cells are consistently grown under physiological stresses in vivo and never undergo the two-dimensional bottleneck, which preserves the molecular and biological properties present when the tumor was in the human patient. Notable, PDX models derived from organ sites of metastases (i.e., brain) display similar metastatic capacity, while PDX models derived from therapy naive patients and patients with acquired resistance to therapy (i.e., BRAF/MEK inhibitor therapy) display similar sensitivity to therapy.

Tumor tissue for melanoma PDX models can come from a variety of different sources and can also be processed per the growth dynamics of individual models and the desired use of the PDX tissue. The priority when establishing a PDX model is to have sufficient material to bank for future use and DNA for characterization (Figure 1).
Once sufficient material is banked, tumor tissue can be expanded in one of three main methods to grow enough tumor to perform a formal the...

Watch this Scientific Journal Video about A Melanoma Patient-Derived Xenograft Model Video at JoVE.com

A Melanoma Patient-Derived Xenograft Model Video (Video) | JoVE

Patient-derived xenograft (PDX) models more robustly recapitulate melanoma molecular and biological features and are more predictive of therapy response compared to traditional plastic tissue culture-based assays. Here we describe our standard operating protocol for the establishment of new PDX models and the characterization/experimentation of existing PDX models.

A Melanoma Patient-Derived Xenograft Model

Accumulating evidence suggests that molecular and biological properties differ in melanoma cells grown in traditional two-dimensional tissue culture ...

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