Name: in vivo immunogenicity screening of tumor-derived extracellular vesicles by flow cytometry of splenic t cells
Uploaded: 2021-09-23T14:30:00
Description: Watch this Scientific Journal Video about In Vivo Immunogenicity Screening of Tumor-Derived Extracellular Vesicles by Flow Cytometry of Splenic T Cells at JoVE.com

This study was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Projektnummer 360372040 - SFB 1335 and Projektnummer 395357507 - SFB 1371 (to H.P.), a Mechtild Harf Research Grant from the DKMS Foundation for Giving Life (to H.P.) a Young Investigator Award by the Melanoma Research Alliance (to S.H.), a scholarship by the Else-Kr&#246;ner-Fresenius-Stiftung (to F.S.), a Seed Fund by the Technical University Munich (to S.H.) and a research grant by the Wilhelm Sander Foundation (2021.041.1, to S.H.). H. P. is supported by the EMBO Young Investigator Program.
AUTHOR CONTRIBUTIONS:
F.S., H.P., and S.H. designed the research, analyzed, and interpreted the results. F.S. and S.H. wrote the manuscript. H.P. and S.H. guided the study.

At the onset of experiments, mice were at least 6 weeks of age and were maintained under specific pathogen-free conditions. The present protocol complies with the Institutional ethical standards and prevailing local regulations. Animal studies were approved by the local regulatory agency (Regierung von Oberbayern, Munich, Germany). Possible sex-related biases were not investigated in these studies.
1. Generation and isolation of EVs derived from tumor cells after chemotherapy exposure
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This protocol provides an immunological in vivo assessment of EVs derived from melanoma cells under chemotherapy-induced stress while adapting to EVs emitted from various cancers under various treatments. Immunizing mice with EVs derived from oxaliplatin-treated B16-OVA cells, for instance, expands IFN-&#947;-producing CD8+ T cells in the spleen, which are further stimulated by ex vivo incubation with ovalbumin, indicating a tumor-specific immune response. Thus, detection of immunogenic EVs b...

The immune system plays a pivotal role in the fight against cancer, both when incited by immune checkpoint inhibition and for the efficacy of conventional cancer therapies. Tumor cells succumbing to genotoxic therapies such as the chemotherapeutic agents oxaliplatin and doxorubicin, or ionizing radiation treatment can release antigens and danger-associated molecular patterns (DAMPs) that potentially initiate an adaptive anti-tumor immune response1. The most prominent DAMPs, in the context of immunogenic cell death, include find-me signals such as chemotactic ATP, eat-me signals such as the exposure of calreticulin, that promotes tumor cell uptake by antigen-presenting cells, and the release of HMGB1, that activates pattern recognition receptors, thereby enhancing the cross-presentation of tumor antigens2. Furthermore, type I interferons (IFN-I), induced via tumor-derived immunogenic nucleic acids or other stimuli, are sensed by dendritic cells, enabling them to effectively prime tumor-specific cytotoxic T cells3,4. Clinically, activated and proliferating CD8+ T cells infiltrating the tumor provide an independent prognostic factor for prolonged survival in many cancer patients. Released from such activated T cells, IFN-&#947; mediates direct antiproliferative effects on cancer cells and drives Th1 polarization and cytotoxic T cell differentiation, thereby contributing to effective immunosurveillance against cancer5,6. Oxaliplatin is a bona fide immunogenic cell death inducer, mediating such adaptive immune response against cancer7. However, the plethora of initial immunogenic signals released by tumor cells under therapy-induced stress remains to be fully unveiled. Despite significant advances in cancer immunotherapy, expanding its benefits to a larger portion of patients remains a challenge. A more detailed understanding of immunogenic signals that initiate T cell activation may guide the development of novel therapies.
A heterogeneous group of membrane-enclosed structures, known as extracellular vesicles (EVs), seem to serve as intercellular communication devices. Emitted by virtually all cell types, EVs carry functional proteins, RNA, DNA, and other molecules to a recipient cell or may alter a cell&#39;s functional state just by binding to receptors on the cell surface. Their biologically active cargo varies significantly by the type and functional state of the generating cell8. In cancer immunology, EVs released from tumor cells have been predominantly regarded as adversarial to immunotherapy because they eventually promote invasive growth, preform metastatic niches9, and suppress the immune response10. In contrast, some studies have shown that EVs can transfer tumor antigens to dendritic cells for effective cross-presentation11,12. EVs may provide immunostimulatory nucleic acids if they emerge under therapy-induced stress, facilitating an anti-tumor immune response13,14. Sensing of such RNA and DNA&#160;innate immune ligands in the tumor microenvironment has recently been shown to modulate responsiveness to checkpoint blockade significantly15,16,17. Hence, the immunogenic role of EVs released by tumor cells under different therapy-induced stress needs to be further elucidated. Since EVs constitute a young yet growing field of research, standardization of methods is still ongoing. Therefore, sharing knowledge is essential to improve the research reproducibility on interactions between EVs and cancer immunology. With this in mind, this manuscript describes a simple protocol to assess the immunogenic effect of tumor-derived EVs in vivo.
This assessment is performed by generating tumor-derived EVs, immunizing recipient mice with those EVs, and analyzing splenic T cells via flow cytometry. EV generation is ideally performed by seeding murine tumor cells in an EV-free cell culture medium for a high degree of purity. Cells are treated with a specific cell stress stimulus, such as chemotherapy, to compare the effect of therapy-induced EVs against baseline immunogenicity of respective tumor-derived EVs. The isolation of EVs may well be performed by various techniques that should be selected according to in vivo applicability and local availability. The following protocol describes a precipitation-based assay with a commercial kit for EV purification. Mice are immunized twice with those EVs. Fourteen days after the first injection, T cells are extracted from the spleen and analyzed for IFN-&#947; production via flow cytometry to evaluate a systemic immune response. With this, the potential of tumor-derived EVs, emerging under different therapeutic regimens, to induce anti-tumor T cell responses is assessed relatively easily, quickly, and with high validity13. Therefore, this method is suitable for an immunological screening of EVs derived from cancer cells under various conditions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anti-CD3 FITC</td>
			<td>Biolegend</td>
			<td>100204</td>
			<td>Clone 17A2</td>
		</tr>
		<tr>
			<td>Anti-CD4 PacBlue</td>
			<td>Biolegend</td>
			<td>100428</td>
			<td>Clone GK1.5</td>
		</tr>
		<tr>
			<td>Anti-CD8 APC</td>
			<td>Biolegend</td>
			<td>100712</td>
			<td>Clone 53-6.7</td>
		</tr>
		<tr>
			<td>Anti-IFN&#947; PE</td>
			<td>eBioscience</td>
			<td>RM90022</td>
			<td>Clone XMG1.2</td>
		</tr>
		<tr>
			<td>Brefeldin A</td>
			<td>Biolegend</td>
			<td>420601</td>
			<td>Brefeldin A Solution (1,000x)</td>
		</tr>
		<tr>
			<td>Cell Strainer, 100 &#181;m</td>
			<td>Greiner</td>
			<td>542000</td>
			<td>EASYstrainer 100 &#181;m</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Sigma-Aldrich</td>
			<td>D6429</td>
			<td>Dulbecco&#39;s Modified Eagle&#39;s Medium with D-glucose (4.5 g/L) and L-glutamine (4 mM)</td>
		</tr>
		<tr>
			<td>FBS Good Forte</td>
			<td>PAN BIOTECH</td>
			<td>P40-47500</td>
			<td>Fetal Calf Serum (FCS)</td>
		</tr>
		<tr>
			<td>Fixable Viability Dye eFluor 506</td>
			<td>eBioscience, division of Thermo Fischer Scientific</td>
			<td>65-0866-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixation/Permeabilization Concentrate</td>
			<td>eBioscience</td>
			<td>00-5123-43</td>
			<td>Fixation/Permeabilization Concentrate (10x)</td>
		</tr>
		<tr>
			<td>Fixation/Permeabilization Diluent</td>
			<td>eBioscience</td>
			<td>00-5223-56</td>
			<td></td>
		</tr>
		<tr>
			<td>Ionomycin</td>
			<td>Sigma-Aldrich</td>
			<td>407952</td>
			<td>From Streptomyces conglobatus - CAS 56092-82-1, &#8805; 97% (HPLC)</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Gibco</td>
			<td>25030-032</td>
			<td>L-Glutamine (200 mM)</td>
		</tr>
		<tr>
			<td>Ovalbumin</td>
			<td>InvivoGen</td>
			<td>vac-pova</td>
			<td>Ovalbumine with &#60; 1 EU/mg endotoxin - CAS 9006-59-1</td>
		</tr>
		<tr>
			<td>Oxaliplatin</td>
			<td>Pharmacy of MRI hospital</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma-Aldrich</td>
			<td>D8537</td>
			<td>Phosphate Buffered Saline without calcium chloride and magnesium chloride</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Gibco</td>
			<td>1514-122</td>
			<td>Mixture of penicillin (10,000 U/mL) and streptomycin (10,000 ug/mL)</td>
		</tr>
		<tr>
			<td>PMA</td>
			<td>Sigma-Aldrich</td>
			<td>P1585</td>
			<td>Phorbol 12-myristate 13-acetate, &#8805; 99% (HPLC)</td>
		</tr>
		<tr>
			<td>PVDF filter, 0,22 &#181;m, for syringes</td>
			<td>Merck Millipore</td>
			<td>SLGV033RS</td>
			<td>Millex-GV Filter Unit 0.22 &#181;m Durapore PVDF Membrane</td>
		</tr>
		<tr>
			<td>Red Blood Cell Lysis Buffer</td>
			<td>Invitrogen</td>
			<td>00-4333-57</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Thermo Fischer Scientific</td>
			<td>11875</td>
			<td>Roswell Park Memorial Institute 1640 Medium with D-glucose (2.00 g/L) and L-glutamine (300 mg/L), without HEPES</td>
		</tr>
		<tr>
			<td>Syringe, 26 G</td>
			<td>BD Biosciences</td>
			<td>305501</td>
			<td>1 mL Sub-Q Syringes with needle (0.45 mm x 12.7 mm)</td>
		</tr>
		<tr>
			<td>Total Exosome Isolation Reagent</td>
			<td>Invitrogen</td>
			<td>4478359</td>
			<td>For isolation from cell culture media</td>
		</tr>
		<tr>
			<td>&#946;-Mercaptoethanol</td>
			<td>Thermo Fischer Scientific</td>
			<td>31350</td>
			<td>&#946;-Mercaptoethanol (50 mM)</td>
		</tr>
	</tbody>
</table>

in vivo immunogenicity screening of tumor-derived extracellular vesicles by flow cytometry of splenic t cells

Immunogenic cell death of tumors, caused by chemotherapy or irradiation, can trigger tumor-specific T cell responses by releasing danger-associated molecular patterns and inducing the production of type I interferon. Immunotherapies, including checkpoint inhibition, primarily rely on preexisting tumor-specific T cells to unfold a therapeutic effect. Thus, synergistic therapeutic approaches that exploit immunogenic cell death as an intrinsic anti-cancer vaccine may improve their responsiveness. However, the spectrum of immunogenic factors released by cells under therapy-induced stress remains incompletely characterized, especially regarding extracellular vesicles (EVs). EVs, nano-scale membranous particles emitted from virtually all cells, are considered to facilitate intercellular communication and, in cancer, have been shown to mediate cross-priming against tumor antigens. To assess the immunogenic effect of EVs derived from tumors under various conditions, adaptable, scalable, and valid methods are sought-for. Therefore, herein a relatively easy and robust approach is presented to assess EVs' in vivo immunogenicity. The protocol is based on flow cytometry analysis of splenic T cells after in vivo immunization of mice with EVs, isolated by precipitation-based assays from tumor cell cultures under therapy or steady-state conditions. For example, this work shows that oxaliplatin exposure of B16-OVA murine melanoma cells resulted in the release of immunogenic EVs that can mediate the activation of tumor-reactive cytotoxic T cells. Hence, screening of EVs via in vivo immunization and flow cytometry identifies conditions under which immunogenic EVs can emerge. Identifying conditions of immunogenic EV release provides an essential prerequisite to testing EVs' therapeutic efficacy against cancer and exploring the underlying molecular mechanisms to ultimately unveil new insights into EVs' role in cancer immunology.

This protocol is intended to facilitate the straightforward and easily reproducible assessment of the immunogenicity of tumor-derived EVs. Hereby, mice are inoculated with EVs derived from in vitro cultures of tumor cells expressing the model antigen chicken ovalbumin (OVA). The subsequent immune response is analyzed in splenic T cells via flow cytometry.
Figure 1 gives an overview of the practical steps of the entire protocol. Since the work foc...

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In Vivo Immunogenicity Screening of Tumor-Derived Extracellular Vesicles by Flow Cytometry of Splenic T Cells

This manuscript describes how to assess in vivo immunogenicity of tumor cell-derived extracellular vesicles (EVs) using flow cytometry. EVs derived from tumors undergoing treatment-induced immunogenic cell death seem particularly relevant in tumor immunosurveillance. This protocol exemplifies the assessment of oxaliplatin-induced immunostimulatory tumor EVs but can be adapted to various settings.

In Vivo Immunogenicity Screening of Tumor-Derived Extracellular Vesicles by Flow Cytometry of Splenic T Cells

Immunogenic cell death of tumors, caused by chemotherapy or irradiation, can trigger tumor-specific T cell responses by releasing danger-associated ...

This video shows how to assess the in vivo immunogenicity of tumor-derived extracellular vesicles, or EVs, using flow cytometry. The screening method described herein is relatively easy to perform and can be adapted to various settings. In cancer, identifying conditions of immunogenic extracellular vesicle releases of particular translational relevance.As such, autologous EVs might be used as personalized anti-cancer treatments. Demonstrating the first part of the procedure will be Tatiana Nedelko, a technical assistant from my laboratory. To start the preparation of cell culture media required for extracellular vesicle, or EVs, deplete the bovine EVs in FCS media by ultracentrifugation at 100, 000 times g for 24 hours at 4 degrees Celsius.Discard the pellet after centrifugation. Harvest the murine B16 melanoma cells expressing ovalbumin, or B16-OVA cells, from the culture and wash the cells twice with PBS. Then, seed the cells at a concentration of 400, 000 cells per milliliter in the EV-depleted media.Next, treat the B16-OVA cells with 30 micrograms of oxaliplatin per milliliter and incubate for 24 hours at 37 degrees Celsius with untreated control samples. After 24 hours, collect the supernatant to centrifuge at 400 times g for five minutes at 4 degree Celsius. Discard the pellet before centrifugation again at 2, 000 times g for 30 minutes at 4 degrees Celsius.After discarding the pellet, filter the supernatant through a 220 nanometer PVDF membrane filter into a fresh tube. Then, mix 1 milliliter of supernatant with 0.5 milliliters of a specific commercially-available exosome isolation reagent. Vortex and transfer the mixture into 1.5 milliliter tubes, followed by overnight incubation at 4 degrees Celsius.The next day, centrifuge the mixture at 10, 000 times g for 60 minutes at 4 degrees Celsius. After carefully discarding the supernatant, remove the remaining drops by tapping the 1.5 milliliter tube upside down on a paper towel and by aspiration through a fine tip of pipette without touching the EV pellet at the bottom. Resuspend the pellet in cold PBS by pipetting up and down without scratching the pellet with the tip.Then, pool the EVs from all tubes. If not using immediately, store the EV suspensions at 80 degrees Celsius in siliconized vessels for up to 28 days until application. To immunize each mouse in the treatment group with EVs isolated from 4.0 x 10 to the fifth B16-OVA cells, mix 5 microliters of the EV suspension with 55 microliters of cold PBS.Next, fill syringes mounted with 26 to 30-gauge needles with 60 microliters of the diluted EVs or PBS and then immediately put the syringe on ice. Inoculate the EVs or PBS subcutaneously into the medial aspect of the mice's thigh. Repeat the immunization after seven days.14 days after the first treatment, sacrifice the mice to resect the spleen. Then, mash the resected spleen with a moistened 100-micrometer cell strainer and the plastic plunger of a syringe. Flush the splenic cells into a 50 milliliter tube with 5 to 10 milliliters of the cool complete RPMI.Next, centrifuge the cells at 400 times g for five minutes at 4 degrees Celsius before discarding the supernatant. To remove erythrocytes from the cell suspension, resuspend and incubate the cell pellet with 2 milliliters of the red blood cell lysis buffer for five minutes at room temperature. Then, stop the reaction by adding five to 10 milliliters of complete RPMI, followed by centrifugation as described earlier.After resuspending the cell pellet in complete RPMI, count the cells from every mouse and place the triplicates of 200, 000 splenocytes with 200 microliters of cRPMI into each well of a 96-well plate with a U-shaped bottom. Then, incubate the plates for 48 hours at 37 degrees Celsius. After 48 hours, treat the cell culture with 5 nanograms per milliliter Brefeldin A, 20 nanograms per milliliter PMA, and 1 microgram per milliliter Ionomycin at 37 degrees Celsius for 4 hours.Post incubation, transfer the splenocytes to a 96-well plate with a V-shaped bottom and wash the cells twice with PBS. Resuspend the pelleted splenocytes in the freshly-prepared staining solution and incubate the cell suspension for 30 minutes at 4 degrees Celsius protected from light. For fixation and permeabilization, wash the splenocytes twice in the FACS-buffer and then resuspend the splenocytes in 100 microliters per well of the fixation and permeabilization solution, followed by incubation in the dark as explained earlier.For staining the intracellular interferon gamma, wash the splenocytes in the fixation or permeabilization buffer before resending the cells with the fluorescent antibodies against interferon gamma diluted 1:200 in the buffer. Incubate the splenocytes for 1 to 12 hours at 4 degree Celsius in the dark. After thorough washing and resuspension in FACS-buffer, analyze the activation of cytotoxic T cells according to the gating strategy explained in the manuscript.In the representative image, the gating strategy to analyze the activation of cytotoxic T-cells is displayed. The cells were gated as the single cells, the lymphocyte subset, the viable CD3-positive T cells, and the CD4-negative CD8-positive cytotoxic T-cells. The intracellular accumulation of the interferon gamma was assessed as a surrogate marker for the activation.After the immunization with EVs derived from the tumor cells, the induction of antigen-specific T cell responses in recipient mice was studied. The tumor-derived EVs cultured under genotoxic stress conditions, such as oxaliplatin treatment, induced potent activation of the splenic cytotoxic T cells in contrast to untreated EVs. The vehicle-treated group of animals showed the lowest response.The activation of splenic T cells was determined after the ex vivo restimulation either in the presence or absence of ovalbumin. The production of the interferon gamma was increased when the splenocytes of tumor EV-treated animals were restimulated with the model tumor antigen ovalbumin before the analysis. Please note that reproducible results rely on the constant isolation efficacy of EVs.Thus, ensure that EV pellets are resuspended entirely and promptly to avoid desiccation. With this protocol, we were able to analyze specific pathways within tumor cells that determine the immunogenicity of tumor cell-derived EVs. This may pave the road to harness such immunogenic EVs in cancer treatment.

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Research

JoVE Journal

Cancer Research

Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median survival following diagnosis is less than 15 months with maximal surgical resection, radiation, and temozolomide chemotherapy. The challenges inherent in developing more effective GBM treatments have become increasingly clear, and include its unyielding invasiveness, its resistance to standard treatments, its genetic complexity and molecular adaptability, and subpopulations of GBM cells with phenotypic similarities to normal stem cells, herein referred to as glioblastoma stem cells (GSCs). Because GSCs are required for tumor growth and progression, differentiation-based therapy represents a viable treatment modality for these incurable neoplasms. 
The following protocol describes a collection of procedures to establish a high throughput screening platform aimed at the identification of small molecules that promote GSC astroglial differentiation. At the core of the system is a glial fibrillary acidic protein (GFAP) differentiation reporter-construct. The protocol contains the following general procedures: (1) establishing GSC differentiation reporter lines; (2) testing/validating the relevance of the reporter to GSC self-renewal/clonogenic capacity; and (3) high-capacity flow-cytometry based drug screening. 
The screening platform provides a straightforward and inexpensive approach to identify small molecules that promote GSCs differentiation. Furthermore, utilization of libraries of FDA-approved drugs holds the potential for the identification of agents that can be repurposed more rapidly. Also, therapies that promote cancer stem cell differentiation are expected to work synergistically with current "standard of care" therapies that have been shown to target and eliminate primarily more differentiated cancer cells.

An efficient screening protocol is presented for the identification of small molecules that promote astroglial differentiation in glioblastoma stem cells (GSCs). The assay is based on a stem cell differentiation reporter whereby the expression of the enhanced GFP (eGFP) is driven by the human GFAP promoter.

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median ...

In Vivo EPR Assessment of pH, pO2, Redox Status, and Concentrations of Phosphate and Glutathione in the Tumor Microenvironment

This protocol demonstrates the capability of low-field electron paramagnetic resonance (EPR)-based techniques in combination with functional paramagnetic probes to provide quantitative information on the chemical tumor microenvironment (TME), including pO2, pH, redox status, concentrations of interstitial inorganic phosphate (Pi), and intracellular glutathione (GSH). In particular, an application of a recently developed soluble multifunctional trityl probe provides unsurpassed opportunity for in vivo concurrent measurements of pH, pO2 and Pi in Extracellular space (HOPE probe). The measurements of three parameters using a single probe allow for their correlation analyses independent of probe distribution and time of the measurements.

In Vivo EPR Assessment of pH, pO2, Redox Status, and Concentrations of Phosphate and Glutathione in the Tumor Microenvironment

Low-field (L-band, 1.2 GHz) electron paramagnetic resonance using soluble nitroxyl and trityl probes is demonstrated for assessment of physiologically important parameters in the tumor microenvironment in mouse models of breast cancer.

This protocol demonstrates the capability of low-field electron paramagnetic resonance (EPR)-based techniques in combination with functional paramagnetic ...

Immunophenotyping of Orthotopic Homograft (Syngeneic) of Murine Primary KPC Pancreatic Ductal Adenocarcinoma by Flow Cytometry

Homograft (syngeneic) tumors are the workhorse of today&#39;s immuno-oncology (I/O) preclinical research. The tumor microenvironment (TME), particularly its immune-components, is vital to the prognosis and prediction of treatment outcomes, especially those of immunotherapy. TME immune-components are composed of different subsets of tumor-infiltrating immune cells assessable by multi-color FACS. Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest malignances lacking good treatment options, thus an urgent and unmet medical need. One important reason for its non-responsiveness to various therapies (chemo-, targeted, I/O) has been its abundant TME, consisting of fibroblasts and leukocytes that protect tumor cells from these therapies. Orthotopically implanted PDAC is believed to more accurately recapture the TME of human pancreatic cancers than conventional subcutaneous (SC) models.
Homograft tumors (KPC) are transplants of mouse spontaneous PDAC originating from genetically engineered KPC-mice (KrasG12D/+/P53-/-/Pdx1-Cre) (KPC-GEMM). The primary tumor tissue is cut into small fragments (~2 mm3) and transplanted subcutaneously (SC) to the syngeneic recipients (C57BL/6, 7&#8211;9 weeks old). The homografts were then surgically orthotopically transplanted onto the pancreas of new C57BL/6 mice, along with SC-implantation, which reached tumor volumes of 300&#8211;1,000 mm3 by 17 days. Only tumors of 400&#8211;600 mm3 were harvested per approved autopsy procedure and cleaned to remove the adjacent non-tumor tissues. They were dissociated per protocol using a tissue dissociator into single-cell suspensions, followed by staining with designated panels of fluorescently-labeled antibodies for various markers of different immune cells (lymphoid, myeloid and NK, DCs). The stained samples were analyzed using multi-color FACS to determine numbers of immune cells of different lineages, as well as their relative percentage within tumors. The immune profiles of orthotopic tumors were then compared to those of SC tumors. The preliminary data demonstrated significantly elevated infiltrating TILs/TAMs in tumors over the pancreas, and higher B-cell infiltration into orthotopic rather than SC tumors.

Immunophenotyping of Orthotopic Homograft Syngeneic of Murine Primary KPC Pancreatic Ductal Adenocarcinoma by Flow Cytometry

The experimental procedure on the immunophenotyping of murine orthotopic PDAC homografts aims at profiling the tumor immuno-microenvironment. Tumors are orthotopically implanted via surgery. Tumors of 200&#8211;600 mm3 in size were harvested and dissociated to prepare single-cell suspensions, followed by multi-immune marker FACS analysis using different fluorescently-labeled antibodies.

Homograft (syngeneic) tumors are the workhorse of today&#39;s immuno-oncology (I/O) preclinical research. The tumor microenvironment (TME), particularly ...

A Spheroid Killing Assay by CAR T Cells

Immunotherapy has become a field of growing interest in the fight against cancer otherwise untreatable. Among all immunotherapeutic methods, chimeric antigen receptor (CAR) redirected T cells obtained the most spectacular results, in particular with pediatric B-acute lymphoblastic leukemia (B-ALL). Classical validation methods of CAR T cells rely on the use of specificity and functionality assays of the CAR T cells against target cells in suspension and in xenograft models. Unfortunately, observations made in vitro are often decoupled from results obtained in vivo and a lot of effort and animals could be spared by adding another step: the use of 3D culture. The production of spheroids out of potential target cells that mimic the 3D structure of the tumor cells when they are engrafted into the animal model represents an ideal alternative. Here, we report an affordable, reliable and easy method to produce spheroids from a transduced colorectal cell line as a validation tool for adoptive cell therapy (exemplified here by CD19 CAR T cells). This method is coupled with an advanced live imaging system that can follow spheroid growth, effector cells cytotoxicity and tumor cell apoptosis.

This protocol is designed to assess immunotherapeutic redirected T-cell (CAR T-cell) cytotoxicity against 3D structured cancerous cells (spheroids) in real time.

Immunotherapy has become a field of growing interest in the fight against cancer otherwise untreatable. Among all immunotherapeutic methods, chimeric ...

Real Time Detection of In Vitro Tumor Cell Apoptosis Induced by CD8+ T Cells to Study Immune Suppressive Functions of Tumor-infiltrating Myeloid Cells

Potentiation of the tumor-killing ability of CD8+ T cells in tumors, along with their efficient tumor infiltration, is a key element of successful immunotherapies. Several studies have indicated that tumor infiltrating myeloid cells (e.g., myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs)) suppress cytotoxicity of CD8+ T cells in the tumor microenvironment, and that targeting these regulatory myeloid cells can improve immunotherapies. Here, we present an in vitro assay system to evaluate immune suppressive effects of monocytic-MDSCs and TAMs on the tumor-killing ability of CD8+ T cells. To this end, we first cultured na&#239;ve splenic CD8+ T cells with anti-CD3/CD28 activating antibodies in the presence or absence of suppressor cells, and then co-cultured the pre-activated T cells with target cancer cells in the presence of a fluorogenic caspase-3 substrate. Fluorescence from the substrate in cancer cells was detected by real-time fluorescence microscopy as an indicator of T-cell induced tumor cell apoptosis. In this assay, we can successfully detect the increase of tumor cell apoptosis by CD8+ T cells and its suppression by pre-culture with TAMs or MDSCs. This functional assay is useful for investigating CD8+ T cell suppression mechanisms by regulatory myeloid cells and identifying druggable targets to overcome it via high throughput screening.

Real Time Detection of In Vitro Tumor Cell Apoptosis Induced by CD8+ T Cells to Study Immune Suppressive Functions of Tumor-infiltrating Myeloid Cells

We describe here a protocol to investigate cytotoxicity of pre-activated CD8+ T cells against cancer cells by detecting apoptotic cancer cells via real-time microscopy. This protocol can investigate mechanisms behind myeloid cell-induced T cell suppression and evaluate compounds aimed at replenishing T cells via blockade of immune suppressive myeloid cells.

Potentiation of the tumor-killing ability of CD8+ T cells in tumors, along with their efficient tumor infiltration, is a key element of successful ...

Extraction of Extracellular Vesicles from Whole Tissue

Circulating and interstitial small membrane-bound extracellular vesicles (EVs) represent promising targets for the development of novel diagnostic or prognostic biomarker assays, and likely serve as important players in the progression of a vast spectrum of diseases. Current research is focused on the characterization of vesicles secreted from multiple cell and tissue types in order to better understand the role of EVs in the pathogenesis of conditions including neurodegeneration, inflammation, and cancer. However, globally consistent and reproducible techniques to isolate and purify vesicles remain in progress. Moreover, methods for extraction of EVs from solid tissue ex vivo are scarcely described. Here, we provide a detailed protocol for extracting small EVs of interest from whole fresh or frozen tissues, including brain and tumor specimens, for further characterization. We demonstrate the adaptability of this method for multiple downstream analyses, including electron microscopy and immunophenotypic characterization of vesicles, as well as quantitative mass spectrometry of EV proteins.

Here, we provide a detailed protocol to isolate small extracellular vesicles (EVs) from whole tissues, including brain and tumor specimens. This method offers a reproducible technique to extract EVs from solid tissue for further downstream analyses.

Circulating and interstitial small membrane-bound extracellular vesicles (EVs) represent promising targets for the development of novel diagnostic or ...

Cell Cycle-specific Measurement of &#947;H2AX and Apoptosis After Genotoxic Stress by Flow Cytometry

The presented method or slightly modified versions have been devised to study specific treatment responses and side effects of various anti-cancer treatments as used in clinical oncology. It enables a quantitative and longitudinal analysis of the DNA damage response after genotoxic stress, as induced by radiotherapy and a multitude of anti-cancer drugs. The method covers all stages of the DNA damage response, providing endpoints for induction and repair of DNA double-strand breaks (DSBs), cell cycle arrest and cell death by apoptosis in case of repair failure. Combining these measurements provides information about cell cycle-dependent treatment effects and thus allows an in-depth study of the interplay between cellular proliferation and coping mechanisms against DNA damage. As the effect of many cancer therapeutics including chemotherapeutic agents and ionizing radiation is limited to or strongly varies according to specific cell cycle phases, correlative analyses rely on a robust and feasible method to assess the treatment effects on the DNA in a cell cycle-specific manner. This is not possible with single-endpoint assays and an important advantage of the presented method. The method is not restricted to any particular cell line and has been thoroughly tested in a multitude of tumor and normal tissue cell lines. It can be widely applied as a comprehensive genotoxicity assay in many fields of oncology besides radio-oncology, including environmental risk factor assessment, drug screening and evaluation of genetic instability in tumor cells.

The presented method combines the quantitative analysis of DNA double-strand breaks (DSBs), cell cycle distribution and apoptosis to enable cell cycle-specific evaluation of DSB induction and repair as well as the consequences of repair failure.

The presented method or slightly modified versions have been devised to study specific treatment responses and side effects of various anti-cancer ...

Isolation of Exosome-Enriched Extracellular Vesicles Carrying Granulocyte-Macrophage Colony-Stimulating Factor from Embryonic Stem Cells

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell types, ESCs release small membrane vesicles, such as exosomes, to the extracellular environment. Exosomes serve as essential mediators of intercellular communication and play a basic role in many (patho)physiological processes. Granulocyte-macrophage colony-stimulating factor (GM-CSF) functions as a cytokine to modulate the immune response. The presence of GM-CSF in exosomes has the potential to boost their immune-regulatory function. Here, GM-CSF was stably overexpressed in the murine ESC cell line ES-D3. A protocol was developed to isolate high-quality exosome-enriched extracellular vesicles (EVs) from ES-D3 cells overexpressing GM-CSF. Isolated exosome-enriched EVs were characterized by a variety of experimental approaches. Importantly, significant amounts of GM-CSF were found to be present in exosome-enriched EVs. Overall, GM-CSF-bearing exosome-enriched EVs from ESCs might function as cell-free vesicles to exert their immune-regulatory activities.

This study describes a method to isolate exosome-enriched extracellular vesicles carrying immune-stimulatory granulocyte macrophage colony-stimulating factors from embryonic stem cells.

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell ...

Simultaneous Imaging and Flow-Cytometry-based Detection of Multiple Fluorescent Senescence Markers in Therapy-Induced Senescent Cancer Cells

Chemotherapeutic drugs can induce irreparable DNA damage in cancer cells, leading to apoptosis or premature senescence. Unlike apoptotic cell death, senescence is a fundamentally different machinery restraining&#160;propagation of cancer cells. Decades of scientific studies have revealed the complex pathological effects of senescent cancer cells in tumors and microenvironments that modulate cancer cells and stromal cells. New evidence suggests that senescence is a potent prognostic factor during cancer treatment, and therefore rapid and accurate detection of senescent cells in cancer samples is essential. This paper presents a method to visualize and detect therapy-induced senescence (TIS) in cancer cells. Diffuse large B-cell lymphoma (DLBCL) cell lines were treated with mafosfamide (MAF) or daunorubicin (DN) and examined for the senescence marker, senescence-associated &#946;-galactosidase (SA-&#946;-gal), the DNA synthesis marker 5-ethynyl-2&#8242;-deoxyuridine (EdU), and the DNA damage marker gamma-H2AX (&#947;H2AX). Flow cytometer imaging can help generate high-resolution single-cell images in a short period of time to simultaneously visualize and quantify the three markers in cancer cells.

Here we present a flow cytometry-based method for visualization and quantification of multiple senescence-associated markers in single cells.

Chemotherapeutic drugs can induce irreparable DNA damage in cancer cells, leading to apoptosis or premature senescence. Unlike apoptotic cell death, ...

Far-Red Fluorescent Senescence-Associated &#946;-Galactosidase Probe for Identification and Enrichment of Senescent Tumor Cells by Flow Cytometry

Cellular senescence is a state of proliferative arrest induced by biological damage that normally accrues over years in aging cells but may also emerge rapidly in tumor cells as a response to damage induced by various cancer treatments. Tumor cell senescence is generally considered undesirable, as senescent cells become resistant to death and block tumor remission while exacerbating tumor malignancy and treatment resistance. Therefore, the identification of senescent tumor cells is of ongoing interest to the cancer research community. Various senescence assays exist, many based on the activity of the well-known senescence marker, senescence-associated beta-galactosidase (SA-&#946;-Gal). 
Typically, the SA-&#946;-Gal assay is performed using a chromogenic substrate (X-Gal) on fixed cells, with the slow and subjective enumeration of "blue" senescent cells by light microscopy. Improved assays using cell-permeant, fluorescent SA-&#946;-Gal substrates, including C12-FDG (green) and DDAO-Galactoside (DDAOG; far-red), have enabled the analysis of living cells and allowed the use of high-throughput fluorescent analysis platforms, including flow cytometers. C12-FDG is a well-documented probe for SA-&#946;-Gal, but its green fluorescent emission overlaps with intrinsic cellular autofluorescence (AF) that arises during senescence due to the accumulation of lipofuscin aggregates. By utilizing the far-red SA-&#946;-Gal probe DDAOG, green cellular autofluorescence can be used as a secondary parameter to confirm senescence, adding reliability to the assay. The remaining fluorescence channels can be used for cell viability staining or optional fluorescent immunolabeling.
Using flow cytometry, we demonstrate the use of DDAOG and lipofuscin autofluorescence as a dual-parameter assay for the identification of senescent tumor cells. Quantitation of the percentage of viable senescent cells is performed. If desired, an optional immunolabeling step may be included to evaluate cell surface antigens of interest. Identified senescent cells can also be flow cytometrically sorted and collected for downstream analysis. Collected senescent cells can be immediately lysed (e.g., for immunoassays or 'omics analysis) or further cultured.

A protocol for fluorescent, flow cytometric quantification of senescent cancer cells induced by chemotherapy drugs in cell culture or in murine tumor models is presented. Optional procedures include co-immunostaining, sample fixation to facilitate large batch or time point analysis, and the enrichment of viable senescent cells by flow cytometric sorting.

Cellular senescence is a state of proliferative arrest induced by biological damage that normally accrues over years in aging cells but may also emerge ...