This work was supported by NIH grants P50 CA174521 (to J.R. Howe and A.M. Bellizzi). P.H. Ear is a recipient of the P50 CA174521 Career Enhancement Program award.

All experiments using human neuroendocrine tumor samples have been approved by the University of Iowa Hospital and Clinics IRB committee (Protocol number 199911057). A list of all materials and equipment is described in the Table of Materials. A list of growth media and key solutions is found in Table 1.
1. Small bowel neuroendocrine tumor (SBNET) collection and cell dissociation
<ol>
	<li>Obtain resected patient SBNET samples after tumor tissues confirmatio...

<ol>
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The authors have nothing to disclose.

Tumor 3D cultures have become a valuable resource for preclinical drug testing15. Various tumor organoid biobanks have recently been established from breast cancer and prostate cancer tumors16,17. In this study, we provide a detailed protocol to culture SBNET as spheroids and a simple and fast method to validate the spheroid cultures for NET markers by immunofluorescence and test drug sensitivity. From our experience, SBNET spheroids can g...

Small bowel neuroendocrine tumors (SBNETs) originate from enterochromaffin cells of the small intestine. Although SBNETs are generally known to grow slowly, they commonly metastasize to the liver1. While the surgical removal or tumor ablation can be considered in many cases, recurrence is nearly universal, and, therefore, medical therapy plays an important role in management. Tremendous efforts have been invested to generate new SBNET cell lines for drug testing. However, there has been very little success. Only 6 SBNET cell lines (KRJ-I, CND2, GOT1, P-STS, L-STS, H-STS) have been reported2,3,4,5; and unfortunately one cell line no longer expresses NET markers6 and three other SBNET cell lines (KRJ-I, L-STS, H-STS) were determined to be derived from transformed lymphoblasts instead of NETs7. In order to accelerate the identification of drugs for targeting SBNETs, alternative methods for in vitro drug testing are needed.
Here, we take&#160;advantage of the availability of resected SBNETs and have established a way to culture these patient-derived SBNETs as spheroids growing in ECM. The overall goal of this manuscript is to describe a method to culture SBNET as a three-dimensional (3D) culture and outline procedures to characterize these spheroids for the retention of SBNET markers by immunofluorescence staining and immunohistochemistry.
In addition, we demonstrate how these SBNET spheroids can be used for testing the effect of rapamycin, an anti-cancer drug for NETs8. The rationale behind this protocol is to develop a new method to grow SBNET cells in vitro and use them for drug testing. The advantage of this technique over the traditional method of establishing an SBNET cell line is that 3D cultures of SBNETs can rapidly be obtained and drug testing can be done within 3 weeks. SBNET spheroids could potentially be used as a model for performing in vitro drug screens to identify new drugs for SBNET patients. Since SBNET cell lines are not widely available, 3D cultures of SBNET spheroids can serve as a new in vitro model for studying SBNETs and can be shared among scientists in the field.

<table border="0" cellpadding="0" cellspacing="0" style="width:1009px;" width="1009">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Anti-rabbit FITC</td>
			<td style="width:196px;">Jackson ImmunoResearch</td>
			<td style="width:119px;">11-095-152</td>
			<td style="width:437px;">Secondary antibody couple to a green fluorophore</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Antigen Retrieval Solution</td>
			<td>Agilent Dako</td>
			<td style="width:119px;">S2367</td>
			<td>Solution at pH 9 for preparing slides for IHC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Autostainer Link 48</td>
			<td>Agilent Dako</td>
			<td style="width:119px;">Not Available</td>
			<td>Automated system for antibody staining</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell freezing container</td>
			<td style="width:196px;">Thermo Scientific</td>
			<td>5100-0001</td>
			<td>Container to for freezing cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">CellSence</td>
			<td style="width:196px;">Olympus</td>
			<td style="width:119px;">Version 1.18</td>
			<td>Computer software for using fluorescent microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chromogranin A antibody</td>
			<td>Abcam-45179</td>
			<td style="width:119px;">RB-9003-PO</td>
			<td>Antibodies for IF</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chromogranin A antibody (clone LK2H10)</td>
			<td style="width:196px;">Thermo Scientific</td>
			<td>MA5-13096</td>
			<td>Antibodies for IHC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Collagenase</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:119px;">C0130</td>
			<td>Enzyme for digesting tumor tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMEM</td>
			<td style="width:196px;">Gibco</td>
			<td style="width:119px;">11965-092</td>
			<td>Medium for tissue preparation</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;">DMEM/F12</td>
			<td style="width:196px;">Gibco</td>
			<td style="width:119px;">11320-033</td>
			<td>Medium for organoid cultures</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMSO</td>
			<td style="width:196px;">Sigma</td>
			<td>D8418</td>
			<td>Solvent for dissolving drug</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNAse</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:119px;">DN25</td>
			<td>Enzyme for digesting tumor tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethidium Homodimer</td>
			<td style="width:196px;">Chemodex</td>
			<td style="width:119px;">CDX-E0012-T1E</td>
			<td>DNA and RNA binding dye</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FBS</td>
			<td style="width:196px;">Gibco</td>
			<td style="width:119px;">16000044</td>
			<td>Reagent for culture media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Fluorescent microscope</td>
			<td style="width:196px;">Olympus</td>
			<td style="width:119px;">CKX35</td>
			<td>Microscope for taking pictures of SBENT spheroids</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glutamine</td>
			<td style="width:196px;">Gibco</td>
			<td style="width:119px;">A2916801</td>
			<td>Reagent for culture media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">ImageJ</td>
			<td style="width:196px;">National Institutes of Health</td>
			<td style="width:119px;">Version 1.51</td>
			<td>Computer software for image analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Insulin</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:119px;">I0516</td>
			<td>Reagent for culture media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Matrigel</td>
			<td style="width:196px;">Corning</td>
			<td>356235</td>
			<td>Matrix to embed and anchore organoids</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mounting medium (VECTASHIELD)</td>
			<td style="width:196px;">Vector Laboratories</td>
			<td>H-1200</td>
			<td>Fixative for labelled-cells with a nuclear stain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nicotinamide</td>
			<td style="width:196px;">Sigma</td>
			<td>72340</td>
			<td>Reagent for culture media</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Paraformaldehyde</td>
			<td style="width:196px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">15710</td>
			<td>Reagent to fix cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PEN/STREP</td>
			<td style="width:196px;">Gibco</td>
			<td style="width:119px;">15140-122</td>
			<td>Reagent for culture media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PT Link</td>
			<td>Agilent Dako</td>
			<td style="width:119px;">Not Available</td>
			<td>Automated system to prepare slides for IHC staining</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rapamycin</td>
			<td style="width:196px;">Alfa Aesar</td>
			<td style="width:119px;">J62473</td>
			<td>Drug that can inhibit NET growth</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Secondary antibodies for IHC</td>
			<td style="width:196px;">Agilent Dako</td>
			<td style="width:119px;">K8000</td>
			<td>Secondary antibodies for IHC using Polymer-based EnVision FLEX system</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SSTR2 antibody</td>
			<td style="width:196px;">GeneScritp</td>
			<td style="width:119px;">A01591</td>
			<td>Antibodies for IF</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SSTR2 antibody (clone UMB1)</td>
			<td style="width:196px;">Abcam</td>
			<td>ab134152</td>
			<td>Antibodies for IHC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Synaptophysin antibody</td>
			<td style="width:196px;">Abcam</td>
			<td>32127</td>
			<td>Antibodies for IF</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Synaptophysin antibody (clone DAK-SYNAP)</td>
			<td>Agilent Dako</td>
			<td style="width:119px;">M7315</td>
			<td>Antibodies for IHC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TritonX</td>
			<td style="width:196px;">Mallinckrodt</td>
			<td style="width:119px;">3555 KBGE</td>
			<td>Reagent to permeablize cells</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">Y-2763 ROCK inhibitor</td>
			<td style="width:196px;">Adipogen</td>
			<td style="width:119px;">AG-CR1-3564-M005</td>
			<td>To improve SBNET spheroid viability after freeze thaw</td>
		</tr>
	</tbody>
</table>

establishment and characterization of small bowel neuroendocrine tumor spheroids

Small bowel neuroendocrine tumors (SBNETs) are rare cancers originating from enterochromaffin cells of the gut. Research in this field has been limited because very few patient derived SBNET cell lines have been generated. Well-differentiated SBNET cells are slow growing and are hard to propagate. The few cell lines that have been established are not readily available, and after time in culture may not continue to express characteristics of NET cells. Generating new cell lines could take many years since SBNET cells have a long doubling time and many enrichment steps are needed in order to eliminate the rapidly dividing cancer-associated fibroblasts. To overcome these limitations, we have developed a protocol to culture SBNET cells from surgically removed tumors as spheroids in extracellular matrix (ECM). The ECM forms a 3-dimensional matrix that encapsulates SBNET cells and mimics the tumor micro-environment for allowing SBNET cells to grow. Here, we characterized the growth rate of SBNET spheroids and described methods to identify SBNET markers using immunofluorescence microscopy and immunohistochemistry to confirm that the spheroids are neuroendocrine tumor cells. In addition, we used SBNET spheroids for testing the cytotoxicity of rapamycin.

There are currently only 2 SBNET cell lines established and published2,3,4,5 and they are not readily available to many researchers. Here, we propose to culture SBNET as spheroids in ECM and use this as an alternative model to study SBNET drug sensitivity. Patient-derived tumor from an SBNET that metastasized to the liver was collected, digested to release SBNET cells, and mixed with liquid ECM...

Watch this Scientific Journal Video about Establishment and Characterization of Small Bowel Neuroendocrine Tumor Spheroids at JoVE.com

Establishment and Characterization of Small Bowel Neuroendocrine Tumor Spheroids

Neuroendocrine tumors (NETs) originate from neuroendocrine cells of the neural crest. They are slow growing and challenging to culture. We present an alternative strategy to grow NETs from the small bowel by culturing them as spheroids. These spheroids have small bowel NET markers and can be used for drug testing.

Small bowel neuroendocrine tumors (SBNETs) are rare cancers originating from enterochromaffin cells of the gut. Research in this field has been limited ...

Well-differentiated SBNET cells are slow growing and hard to propagate. The few established cell lines are not readily available to researchers. To overcome these limitations, we developed this 3D culture protocol.The advantage of this technique over the traditional method of establishing an SBNET cell line is that 3D cultures can be obtained and drug testing can be done within three weeks. This method can be applied to other neuroendocrine tumors such as neuroendocrine tumors from the pancreas. After obtaining a resected patient SBNET sample, cut it into five millimeter cubes and store it in 25 milliliters of DMEM F12 medium in a conical tube for transportation.Incubate the tumors in wash medium prepared according to manuscript directions for 15 minutes. Then transfer them to a new dish and mince them to less than one millimeter pieces using sterile curved scissors. Transfer the minced tissues into a new 50 milliliter tube containing 25 milliliters of wash medium, then centrifuge the sample at 500 times g for 15 minutes at four degrees Celsius.Discard the supernatant and resuspend the pellets in 10 milliliters of wash medium with collagenase and DNase. Allow the minced tumors to digest at 37 degrees Celsius with slow shaking for 90 minutes. It is important not to over digest the tumor samples.Too much enzyme or longer incubation time will kill SBNET cells. After digestion is complete, centrifuge the tube at 500 times g for 15 minutes at four degrees Celsius. Discard the supernatant and resuspend the pellet in 15 milliliters of wash medium.Place a 70 micrometer cell strainer on top of a new 50 milliliter tube and transfer 10 milliliters of the wash buffer through the strainer. Swirl the wash buffer inside the tube to prevent the cells from sticking to the sides. Then filter the cell suspension through the strainer.Centrifuge the cells at 500 times g for 15 minutes at four degrees Celsius. Discard the supernatant and resuspend the pellet in 200 microliters of wash medium. Place the tube on ice and use five microliters of the cells for cell counting with a hemocytometer.Calculate the number of cells, then repeat the centrifugation to remove the supernatant and resuspend the cells in liquid ECM at a concentration of one million cells per milliliter. Next, transfer five to 20 microliters of SBNET spheroids in ECM to a 96 well plate and place the plate in a 37 degrees Celsius incubator to allow the liquid ECM to solidify. Add 200 microliters of SBNET culture medium to each well containing spheroids or culture the organoids in stem cell media as previously described.Use a P1000 pipette to transfer the organoids to a 1.5 milliliter tube and centrifuge the tube at 1, 500 times g for one minute to remove the supernatant. Wash the culture with one milliliter of PBS and centrifuge again to remove the supernatant. Then fix the organoids by adding 500 microliters of paraformaldehyde and incubating them for 15 minutes.After the incubation, wash the culture twice with one milliliter of PBS. Add 500 microliters of PBS with 3%BSA and 0.1%Triton X-100 to permeabilize the culture. Incubate the tube for five minutes, then wash the organoids three times with one milliliter of PBS and 3%BSA.Next, incubate the culture with primary antibodies for one hour then repeat the washes with PBS and BSA. Incubate with the secondary antibodies and repeat the washes making sure to aspirate and discard all supernatant. To image the spheroids, add five microliters of mounting medium containing DAPI and use a P20 pipette to transfer five microliters of the spheroids to a glass slide.Seal the slide with a coverslip and image with a fluorescence microscope using the 10, 20, and 40X objectives. Mechanically break the ECM with a P1000 pipette and transfer it to a sterile 1.5 milliliter tube. Centrifuge the tube at 1, 000 times g at four degrees Celsius.Then remove all supernatant and place the tube on ice. Add two to four times the volume of new ECM to the pellet and mix the contents of the tube by pipetting up and down 10 times making sure to avoid introducing air bubbles. Transfer five to 20 microliters of the ECM and SBNET mixture to a new 96 well plate and allow the ECM to solidify.Then cover the solidified ECM with new SBNET medium and put the plate in the incubator. If shipping SBNET spheroids to another lab, transfer the spheroids with the new ECM to a T25 flask and allow the ECM to solidify. Fill the flask with SBNET spheroid medium, screw the cap on tightly, and prepare the shipping package.Upon receiving the spheroid culture, remove the culture medium and repeat the previous steps to put the spheroids back in culture. SBNET spheroid growth rate was monitored with microscopic imaging. It takes approximately 14 days for SBNET spheroids to double in size when the culture media is changed once a week.After 14 days in culture, SBNET spheroids do not increase in size. The spheroids were stained with antibodies specific against synaptophysin, chromogranin A, and SSTR2 and imaged using immunofluorescence microscopy. The data showed that these markers are localized in the cytoplasm and at the membrane of SBNET cells.To ensure the specificity of the antibodies, the same staining procedures were performed on an organoid line from a pancreas tumor that does not express synaptophysin, chromogranin A and SSTR2 and no green signal was detected. The main advantage of immunofluorescence imaging is that it can be performed within four hours and give similar staining information as the immunohistochemistry. Culturing SBNET as spheroids is a valuable technique for identifying drugs that can inhibit SBNET growth.The spheroids were treated with rapamycin and mTOR inhibitor. After five days, the rapamycin-treated spheroid formed a grape-like structure and became apoptotic or necrotic. When attempting this procedure, it is important to pre-wet the cell strainer and collection tube with wash medium.This will prevent SBNET cells from sticking to the cell strainer and the plastic tube. With this protocol, scientists and clinicians can establish SBNET spheroid cultures from resected tumors, share them with other laboratories, and use them for testing FDA approved drugs.

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Research

JoVE Journal

Cancer Research

6.4K Views.  University of Iowa Carver College of Medicine. Le cellule SBNET ben differenziate sono a crescita lenta e difficili da propagare. Le poche linee cellulari stabilite non sono prontamente disponibili per i ricercatori. Per superare queste limitazioni, abbiamo sviluppato questo protocollo di cultura 3D.Il vantaggio di questa tecnica rispetto al metodo tradizionale di stabilire una linea cellulare SBNET è che le colture 3D possono essere ottenute e il test dei farmaci può essere fatto entro tre settimane. Questo metodo può essere ap...