We thank Dr. Stephen Schoenberger for providing B16-Flt3L cells and the staff of the LJI animal and flow cytometry facilities for excellent support.

All mice used in the study were maintained and housed in the vivarium of the La Jolla Institute for Immunology (LJI) under specific pathogen-free conditions with controlled temperature and humidity. Animal experiments were performed with 8-14 weeks old female C57BL/6 mice according to guidelines and protocols approved by the LJI Animal Care Committee.
1. Preparation of cultured tumor cells for implantation
<ol>
	<li>Culture B16-F10 melanoma cells in Iscove&#39;s Modified Dulbecco&#39;s medium (IMDM) containing 10% heat-inactivated FBS, 2 mM glutamine, 1 mM sodium pyruvate, 1 mM MEM nonessential amino acids, and 100 U/mL each of penicillin and streptomycin. Maintain the cell line at 37 &#176;C under 5% CO2.</li>
	<li>Seed 1.5-2 x 106 B16-F10 cells in a 175T flask and culture for 2 days. Harvest cells when they are 75%-80% confluent.</li>
	<li>Remove the culture medium and wash the flask once with PBS. Aspirate PBS and add 5 mL of 0.25% trypsin-EDTA followed by harshly tapping the rim of the culture flask.</li>
	<li>Add 15 mL of culture medium to neutralize the trypsin-EDTA and pour the contents of the flask into a 50 mL centrifuge tube. Wash the dish surface with 10 mL of PBS and pour into the same 50 mL tube.</li>
	<li>Centrifuge the cells for 5 min at 200 x g. Discard the supernatant and break the cell pellet by finger tapping the bottom of the tube.</li>
	<li>Add cold 10 mL of PBS and gently pipet the cell suspension; then, manually count cells using hemocytometer. Keep the cells on ice before injection.</li>
</ol>
2. Tumor implantation
<ol>
	<li>Gas anesthetize mice with 5% isoflurane at gas flow rate of 1.0 L per min in the fume hood.&#160;Change the flow rate to the maintenance dose of 2% isoflurane&#160;once the mice are fully anesthetized. For this protocol, anesthetization was performed by the veterinarian following&#160;the institutional animal care and use guidelines.</li>
	<li>Shave the hair on the left flank of the mice and sterilize the injection site using alcohol wipes. Intradermally (i.d.) implant B16-F10 tumor cells at 5 x 105 cells in 50 &#181;L of cold PBS in the left flank using a 30 G needle. 
	NOTE: The dose of implanted B16-F10 tumor cells may need to be adjusted in the range of 0.5-5 x 105 cells for successful tumor development.</li>
	<li>After implantation, measure the tumor length and width three times a week using an electronic digital caliper. Calculate the tumor volume (mm3) using the formula: 
	Tumor volume (mm3) = width2 &#215; length &#215; 0.5 
	Treat mice with tumor vaccine when tumors have reached a size of &#8805;2 mm. 
	&#8203;NOTE: Tumors usually can be measured on day 3 after implantation of 5 x 105 tumor cells. Faster B16-F10 tumor growth rate was observed in male C57BL/6, Rag1-/-, or Rag2-/-&#947;c-/-mice. A similar observation was described in other studies8. Keeping the gender of the mice consistent is recommended. However, note that the NIH places emphasis on sex as an important biological variable in biomedical research.</li>
</ol>
3. Vaccine preparation and injection of Flt3L-expressing B16-F10 (B16-Flt3L) cells
<ol>
	<li>Maintain the B16-Flt3L cells in DMEM containing 8% heat-inactivated FBS, 2 mM glutamine, and 100 U/mL each of penicillin and streptomycin at 37 &#176;C under 5% CO2.</li>
	<li>Seed 1 x 106 B16-Flt3L cells in a 175T flask and culture for 2 days. Harvest cells when they are 75%-80% confluent as described in steps 1.3 to 1.6 and suspend in 1 mL of cold PBS.</li>
	<li>Irradiate cells at 150 Gy dose of gamma rays using X-ray Irradiator with 160 kV and 25 mA parameter setting. Count and check the cell viability by trypan blue staining before injection.</li>
	<li>Gas anesthetize mice as described earlier and sterilize the injection site using alcohol wipes. Intradermally inject the mice with 1 x 106 irradiated B16-Flt3L cells in 50 &#181;L of cold PBS on the same flank as the original tumor implantation, ~1 cm away from the site of the primary tumor on days 3, 6, and 9 after the initial cell implantation.</li>
	<li>Mark the vaccine injection sites with a colored pen to distinguish it from the primary tumor. 
	&#8203;NOTE: If 0.5 x 105 B16-F10 cells are initially implanted, it is recommended to perform vaccine treatment on days 8, 11, and 14.</li>
</ol>
4. Intratumoral immune cell isolation
<ol>
	<li>Sacrifice mice using CO2 and cervical dislocation in the fume hood at the end of the experiment (on day 15 after tumor implantation; Figure 1).</li>
	<li>Surgically remove the tumor with the skin from each mouse and put it into 24-well plate with 1 mL 10% FBS/RPMI-1640 medium. Dry the tumors using a paper towel before weighing it.</li>
	<li>Cut the tumors into small pieces. Add 2 mL of digestion buffer (100 &#181;g/mL TL Liberase and 200 &#181;g/mL DNase I in RPMI-1640 medium) and incubate for 25 min at 37 &#176;C.</li>
	<li>Add 10 mL of 10% FBS/RPMI-1640 medium to stop the digestion. Transfer the cells using a 25 mL serological pipette and use the plunger of a 1 mL syringe to grind tissue on a 40 &#181;m cell strainer.</li>
	<li>Centrifuge the cells at 500 x g for 5 min at 4 &#176;C. Resuspend the pellet in 5 mL of 40% density gradient specific medium in PBS, diluted to 1x concentration).</li>
	<li>Add the cell suspension slowly on top of 5 mL of 80% density-gradient-specific medium containing PBS. Centrifuge the cells at 325 x g with low brake setting for 23 min at room temperature (RT).</li>
	<li>After centrifugation, carefully collect the leukocytes layer at the interface between 40% and 80% density-gradient-specific medium and pass it through a 40 &#181;m cell strainer. Centrifuge the cells at 500 x g for 5 min at 4 &#176;C.</li>
	<li>Incubate the pellet in 2 mL of red blood cell (RBC) lysis buffer for 5 min at RT. After incubation, add 10 mL of 10% FBS/RPMI-1640 medium to quench the RBC lysis buffer.</li>
	<li>Centrifuge the cells at 500 x g for 5 min at 4 &#176;C. Resuspend the cells in 0.5 mL of 10% FBS/RPMI-1640 medium and count the total number of cells before use for further analysis. 
	&#8203;NOTE: Collect the spleen or dLN as controls for gating strategy of immune cell subsets by flow cytometry analysis. Follow the cell isolation method as described above with the following changes: Use the plunger of a 1 mL syringe to grind tissue on a 70 &#181;m mesh filter. Wash the tissue with 10% FBS/RPMI-1640 medium to get single-cell suspensions. Lyse the RBC as described.</li>
</ol>
5. Flow cytometry analysis
NOTE: Cells collected from the leukocytes layer contain immune cells and tumor cells. Two independent staining panels are recommended.
<ol>
	<li>Surface staining
	<ol>
		<li>Transfer the cells into a 96-well V-shape-bottom plate. Wash the cells with PBS and stain them with cell viability dye (50-100 &#181;L/well) for 15 min at RT.</li>
		<li>Centrifuge the cells at 500 x g for 5 min at 4 &#176;C. Stain the surface markers with mixed antibodies (detailed dilution is provided in Table of Materials) in FACS buffer (1% FBS and 0.05% NaN3 in PBS) for 30 min on ice (50-100 &#181;L/ well).</li>
		<li>Centrifuge the cells at 500 x g for 5 min and wash them with FACS buffer twice.</li>
		<li>Fix the cells with cell fixation buffer (50-100 &#181;L/ well) for 35 min on ice. Centrifuge the cells at 500 x g for 5 min and wash them twice with FACS buffer.</li>
		<li>Store the samples in FACS buffer (150-200 &#181;L/tube) at 4 &#176;C and protect from light. Acquire the samples on a flow cytometer. For DCs and T cells population, follow the gating strategies provided in Figure 2B and Figure 3A. 
		NOTE: For the staining of myeloid DCs, incubating FC-blocker (Rat anti-mouse CD16/CD32) for 15 min on ice before surface antibodies incubation (step 5.1.2) is recommended.</li>
	</ol>
	</li>
	<li>Cytokine analysis upon ex vivo re-stimulation
	<ol>
		<li>Plate the cells in complete medium (RPMI-1640 supplemented with 10% FBS, 10 mM HEPES, pH 7.2-7.6, 0.1 mM non-essential amino acid, 1 mM sodium pyruvate, 100 U/mL each penicillin and streptomycin, 50 &#956;M 2-mercaptoethanol, and 2 mM L-glutamine) and stimulate with 50 ng/mL of PMA plus 1 &#181;M ionomycin in the presence of protein transport inhibitor for 4 h at 37 &#176;C under 5% CO2.</li>
		<li>Perform surface staining for surface markers as described above in step 5.1.</li>
		<li>Add the permeabilization solution (50-100 &#181;L/well) and incubate for 5 min at RT for intracellular staining. Incubate the cells with antibodies specific for cytokines or nuclear proteins in permeabilization solution (50-100 &#181;L/well) for 60 min on ice or overnight at 4 &#176;C.</li>
		<li>Centrifuge the cells at 500 x g for 5 min and wash them with FACS buffer twice. Store the samples at 4 &#176;C and protect from light. Acquire the samples on a flow cytometer. 
		NOTE: Antibody dilution may have to be adjusted as necessary to accomplish optimal staining.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Zhang, Y., Zhang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+history+and+advances+in+cancer+immunotherapy:+understanding+the+characteristics+of+tumor-infiltrating+immune+cells+and+their+therapeutic+implications.">The history and advances in cancer immunotherapy: understanding the characteristics of tumor-infiltrating immune cells and their therapeutic implications.</a> Cell &amp; Molecular Immunology. 17 (8), 807-821 (2020).</li><li>Banchereau, J., Steinman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+cells+and+the+control+of+immunity.">Dendritic cells and the control of immunity.</a> Nature. 392 (6673), 245-252 (1998).</li><li>Banchereau, 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=Immunobiology+of+dendritic+cells.">Immunobiology of dendritic cells.</a> Annual Review of Immunology. 18, 767-811 (2000).</li><li>Martinez-Lostao, L., Anel, A., Pardo, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+do+cytotoxic+lymphocytes+kill+cancer+cells.">How do cytotoxic lymphocytes kill cancer cells.</a> Clinical Cancer Research. 21 (22), 5047-5056 (2015).</li><li>Maraskovsky, 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=Dramatic+increase+in+the+numbers+of+functionally+mature+dendritic+cells+in+Flt3+ligand-treated+mice:+multiple+dendritic+cell+subpopulations+identified.">Dramatic increase in the numbers of functionally mature dendritic cells in Flt3 ligand-treated mice: multiple dendritic cell subpopulations identified.</a> Journal of Experimental Medicine. 184 (5), 1953-1962 (1996).</li><li>Talmadge, J. 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=Intratumoral,+injection+of+adenoviral+Flt3+ligand+has+therapeutic+activity+in+association+with+increased+intratumoral+levels+of+T+cells+but+not+dendritic+cells.">Intratumoral, injection of adenoviral Flt3 ligand has therapeutic activity in association with increased intratumoral levels of T cells but not dendritic cells.</a> Blood. 104 (11), 5280 (2004).</li><li>Curran, M. A., Allison, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+vaccines+expressing+flt3+ligand+synergize+with+ctla-4+blockade+to+reject+preimplanted+tumors.">Tumor vaccines expressing flt3 ligand synergize with ctla-4 blockade to reject preimplanted tumors.</a> American Association for Cancer Research. 69 (19), 7747-7755 (2009).</li><li>Simon, S. R., Ershler, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hormonal+influences+on+growth+of+B16+murine+melanoma.">Hormonal influences on growth of B16 murine melanoma.</a> Journal of the National Cancer Institute. 74 (5), 1085-1088 (1985).</li><li>Broz, M. L., 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=Dissecting+the+tumor+myeloid+compartment+reveals+rare+activating+antigen-presenting+cells+critical+for+T+cell+immunity.">Dissecting the tumor myeloid compartment reveals rare activating antigen-presenting cells critical for T cell immunity.</a> Cancer Cell. 26 (6), 938 (2014).</li><li>Salmon, 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=Expansion+and+activation+of+CD103(+)+dendritic+cell+progenitors+at+the+tumor+site+enhances+tumor+responses+to+therapeutic+PD-L1+and+BRAF+inhibition.">Expansion and activation of CD103(+) dendritic cell progenitors at the tumor site enhances tumor responses to therapeutic PD-L1 and BRAF inhibition.</a> Immunity. 44 (4), 924-938 (2016).</li><li>Liu, H. 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=Leveraging+the+Treg-intrinsic+CTLA4-PKCeta+signaling+pathway+for+cancer+immunotherapy.">Leveraging the Treg-intrinsic CTLA4-PKCeta signaling pathway for cancer immunotherapy.</a> Journal for Immunotherapy Cancer. 9 (9), 002792 (2021).</li><li>Kong, K. F., 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=Protein+kinase+C-eta+controls+CTLA-4-mediated+regulatory+T+cell+function.">Protein kinase C-eta controls CTLA-4-mediated regulatory T cell function.</a> Nature Immunology. 15 (5), 465-472 (2014).</li></ol>

The authors have nothing to disclose.

The protocol described here is based on the study by Allison&#39;s group. They demonstrated that combination of B16-Flt3L vaccine with CTLA-4 blockade showed a synergistic effect on survival rate and tumor growth, whereas no reduction of tumor growth was seen in mice receiving the B16-Flt3L vaccine or anti-CTLA-4 antibody treatment alone7. Recent studies have revealed a novel Treg-intrinsic CTLA4-PKC&#951; signaling pathway that plays an important obligatory role in regulating the contact-dependen...

Cancer immunotherapy has been recognized as a promising therapeutic strategy based on its less toxic side effects and more durable responses. Several types of immunotherapies have been developed, including oncolytic virus therapies, cancer vaccines, cytokine therapies, monoclonal antibodies, adoptive cell transfer (CAR-T cells or CAR-NK), and immune checkpoint blockade1.
For cancer vaccines, there are different forms of therapeutic vaccines, such as whole cell-based vaccines, protein or peptide vaccines, and RNA or DNA vaccines. Vaccination relies on the ability of antigen-presenting cells (APCs) to process tumor antigens, including tumor-specific antigens, and present them in an immunogenic form to T cells. Dendritic cells (DCs) have been known to be the most potent APCs and are believed to play an important role in antitumor immunity2,3. These cells take up and process tumor antigens, and then migrate to the draining lymph nodes (dLN) to prime and activate tumor-specific T effector (Teff) cells through engagement of the T-cell receptor (TCR) and costimulatory molecules. This results in differentiation and expansion of tumor-specific cytotoxic T cells (CTL), which infiltrate the tumor and kill tumor cells4. Consequently, activation and maturation of DCs represent attractive strategies to stimulate immunity against tumor antigens.
Flt3L is known to promote the maturation and expansion of functionally mature DCs that express MHC class II, CD11c, DEC205, and CD86 proteins5. Intratumoral, but not intravenous, administration of an adenovirus vector incorporating the Flt3L gene (Adv-Flt3L) has been shown to promote immune therapeutic activity against orthrotopic tumors6. Flt3L has also been used in tumor cell-based vaccines consisting of irradiated B16-F10 cells stably expressing retrovirally transduced Flt3L as a way of enhancing the cross-presentation of tumor antigens by DCs and, thus, increasing antitumor responses. The protocol of B16-Flt3L tumor vaccination described here is based on a study published by Dr. James Allison's group7. In this paper, they reported that a B16-Flt3L vaccine combined with CTLA-4 blockade synergistically induced the rejection of established melanoma, resulting in increased survival.
The goal of this protocol is to provide a preclinical immunotherapy model for melanoma. Here, detailed procedures of how to prepare and implant tumor vaccines, and how to analyze the composition and function of intratumoral immune cells from solid tumor are described.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.25% trypsin-EDTA&#160;</td>
			<td>Gibco</td>
			<td>25200-056</td>
			<td></td>
		</tr>
		<tr>
			<td>10% heat-inactivated FBS</td>
			<td>Omega Scientific</td>
			<td>FB-02&#160;</td>
			<td>Lot# 209018</td>
		</tr>
		<tr>
			<td>30G needle</td>
			<td>BD Biosciences</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well V-shape-bottom plate</td>
			<td>SARSTEDT</td>
			<td>83.3926.500</td>
			<td></td>
		</tr>
		<tr>
			<td>B16 cell line expressing Fms-like tyrosine kinase 3 ligand (B16-Flt3L)</td>
			<td>Gift of Dr. Stephen Schoenberger, LJI&#160;</td>
			<td></td>
			<td>Flt3L cDNAs were cloned into the pMG-Lyt2 retroviral vector, as in refernce 5, Supplemental Figure 1</td>
		</tr>
		<tr>
			<td>B16-F10 cell lines</td>
			<td>ATCC</td>
			<td>CRL-6475</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge 5810R</td>
			<td>Eppendorf</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cytofix fixation buffer&#160;</td>
			<td>BD Biosciences</td>
			<td>BDB554655</td>
			<td>Cell fixation buffer (4.2% PFA)&#160;</td>
		</tr>
		<tr>
			<td>Cytofix/Cytoperm kit&#160;</td>
			<td>BD Biosciences</td>
			<td>554714</td>
			<td>Fixation/Permeabilization Solution Kit</td>
		</tr>
		<tr>
			<td>DNase I</td>
			<td>Sigma</td>
			<td>11284932001</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium&#160; (DMEM)&#160;</td>
			<td>Corning</td>
			<td>10013CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Electronic digital caliper</td>
			<td>Fisherbrand</td>
			<td>14-648-17</td>
			<td></td>
		</tr>
		<tr>
			<td>FlowJo software&#160;</td>
			<td>Tree Star</td>
			<td></td>
			<td>Flow cytometer data analysis</td>
		</tr>
		<tr>
			<td>GolgiStop (protein transport inhibitor)</td>
			<td>BD Biosciences</td>
			<td>554724</td>
			<td>1:1500 dilution</td>
		</tr>
		<tr>
			<td>HEPES (1M)</td>
			<td>Gibco</td>
			<td>15630-080</td>
			<td></td>
		</tr>
		<tr>
			<td>Ionomycin</td>
			<td>Sigma</td>
			<td>I0634</td>
			<td></td>
		</tr>
		<tr>
			<td>Iscove&#8217;s modified Dulbecco&#8217;s medium (IMDM)</td>
			<td>Thermo Fisher</td>
			<td>12440053</td>
			<td></td>
		</tr>
		<tr>
			<td>LSR-II cytometers&#160;</td>
			<td>BD Biosciences</td>
			<td></td>
			<td>Flow cytometer</td>
		</tr>
		<tr>
			<td>MEM nonessential amino acids</td>
			<td>Gibco</td>
			<td>11140-050</td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin and streptomycin&#160;</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Percoll&#160;</td>
			<td>GE Healthcare Life Sciences</td>
			<td>GE17-0891-02</td>
			<td>density gradient specific medium</td>
		</tr>
		<tr>
			<td>PMA</td>
			<td>Sigma</td>
			<td>P1585</td>
			<td></td>
		</tr>
		<tr>
			<td>Red Blood Cell Lysing Buffer Hybri-Max liquid</td>
			<td>Sigma</td>
			<td>R7757-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640 medium</td>
			<td>Corning</td>
			<td>10-040-CV</td>
		</tr>
		<tr>
			<td>RS2000 X-ray Irradiator</td>
			<td>Rad Source Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>sodium pyruvate</td>
			<td>Gibco</td>
			<td>11360-070</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile cell strainer 40 &#956;m</td>
			<td>Fisherbrand</td>
			<td>22-363-547</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile cell strainer 70 &#956;m</td>
			<td>Fisherbrand</td>
			<td>22-363-548</td>
			<td></td>
		</tr>
		<tr>
			<td>TL Liberase</td>
			<td>Roche</td>
			<td>477530</td>
			<td></td>
		</tr>
		<tr>
			<td>Zombie Aqua fixable viability kit</td>
			<td>BioLegend</td>
			<td>423101</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibodies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mCD45</td>
			<td>BioLegend</td>
			<td>103135</td>
			<td>Clone: 30-F11 
			Fluorophore: BV570 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mCD3&#949;</td>
			<td>BioLegend</td>
			<td>100327</td>
			<td>Clone: 145-2C11 
			Fluorophore: PerCP-Cy5.5 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mCD8</td>
			<td>BioLegend</td>
			<td>100730 
			100724</td>
			<td>Clone: 53-6.7 
			Fluorophore: Alexa Fluor 700, Alexa Fluor 647 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mCD4</td>
			<td>BioLegend</td>
			<td>100414</td>
			<td>Clone: GK1.5 
			Fluorophore: APC-Cy7 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mFoxp3</td>
			<td>Thermo Fisher Scientific</td>
			<td>11577382</td>
			<td>Clone: FJK-16s 
			Fluorophore: FITC 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-m/hGzmB</td>
			<td>BioLegend</td>
			<td>372208</td>
			<td>Clone: QA16A02 
			Fluorophore: PE 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mIFNg</td>
			<td>BioLegend</td>
			<td>505826</td>
			<td>Clone: XMG1.2 
			Fluorophore: PE-Cy7 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mCD19</td>
			<td>BioLegend</td>
			<td>115543</td>
			<td>Clone: 6D5 
			Fluorophore: BV785 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mGr1</td>
			<td>BioLegend</td>
			<td>108423</td>
			<td>Clone: RB6-8C5 
			Fluorophore: APC/Cy7 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mCD11b</td>
			<td>BioLegend</td>
			<td>101223</td>
			<td>Clone: M1/70 
			Fluorophore: Pacific blue 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mF4/80</td>
			<td>BioLegend</td>
			<td>123114</td>
			<td>Clone: BM8 
			Fluorophore: PECy7 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mCD11c</td>
			<td>BioLegend</td>
			<td>117328</td>
			<td>Clone: N418 
			Fluorophore: PerCP Cy5.5 
			Dilution: 1:100</td>
		</tr>
		<tr>
			<td>Anti-mMHCII</td>
			<td>BioLegend</td>
			<td>107622</td>
			<td>Clone: M5/114.15.2 
			Fluorophore: AF700 
			Dilution: 1:400</td>
		</tr>
		<tr>
			<td>Anti-mCD103</td>
			<td>BioLegend</td>
			<td>121410</td>
			<td>Clone: 2E7 
			Fluorophore: Alexa Fluor 647 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>Anti-mCD86</td>
			<td>BioLegend</td>
			<td>105007</td>
			<td>Clone: GL-1 
			Fluorophore: PE 
			Dilution: 1:200</td>
		</tr>
		<tr>
			<td>FC-blocker (Rat anti-mouse CD16/CD32)</td>
			<td>BD Biosciences</td>
			<td>553141</td>
			<td>Clone: 2.4G2 
			Dilution: 1:200</td>
		</tr>
	</tbody>
</table>

experimental melanoma immunotherapy model using tumor vaccination with a hematopoietic cytokine

Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that promotes the survival and differentiation of dendritic cells (DCs). It has been used in tumor vaccines to activate innate immunity and enhance antitumor responses. This protocol demonstrates a therapeutic model using cell-based tumor vaccine consisting of Flt3L-expressing B16-F10 melanoma cells along with phenotypic and functional analysis of immune cells in the tumor microenvironment (TME). Procedures for cultured tumor cell preparation, tumor implantation, cell irradiation, tumor size measurement, intratumoral immune cell isolation, and flow cytometry analysis are described. The overall goal of this protocol is to provide a preclinical solid tumor immunotherapy model, and a research platform to study the relationship between tumor cells and infiltrating immune cells. The immunotherapy protocol described here can be combined with other therapeutic modalities, such as immune checkpoint blockade (anti-CTLA-4, anti-PD-1, anti-PD-L1 antibodies) or chemotherapy in order to improve the cancer therapeutic effect of melanoma.

A visible black dot of the implanted B16-F10 cells is usually observed on the skin surface ~3 days after tumor implantation. Mice are treated with the tumor vaccine 3, 6, and 9 days after the tumor nodule has reached a size of &#8805;2 mm. We observed a significant reduction in tumor growth in vaccinated mice group ~2 weeks after tumor implantation (Figure 1). At the end of the experiment, we isolated the intratumoral immune cells and analyzed their number and cell surface marker expression,...

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Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine

The protocol presents a cancer immunotherapy model using cell-based tumor vaccination with Flt3L-expressing B16-F10 melanoma. This protocol demonstrates the procedures, including preparation of cultured tumor cells, tumor implantation, cell irradiation, measurement of tumor growth, isolation of intratumoral immune cells, and flow cytometry analysis.

Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that promotes the survival and differentiation of dendritic cells (DCs). It has been ...

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3.2K Views.  La Jolla Institute for Immunology. The protocol presents a cancer immunotherapy model using cell-based tumor vaccination with Flt3L-expressing B16-F10 melanoma. This protocol demonstrates the procedures, including preparation of cultured tumor cells, tumor implantation, cell irradiation, measurement of tumor growth, isolation of intratumoral immune cells, and flow cytometry analysis.

Video: Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine

Murine Experimental Model of Original Tumor Development and Peritoneal Metastasis via Orthotopic Inoculation with Ovarian Carcinoma Cells

Epithelial ovarian carcinoma (EOC) is associated with a poor prognosis because it shows peritoneal dissemination. To improve the prognosis, it is important to control peritoneal dissemination. However, it is still unclear how tumor cells detach from primary lesions and attach to the mesothelium. The establishment of an appropriate animal model is needed to gain an understanding of the mechanism of peritoneal dissemination in vivo. In the current study, we introduce the process from the local injection of EOC cells into the murine ovarian surface to the development of metastasis, including the peritoneum and distant organs. Female nude mice (BALB/c nu/nu) at 8 weeks of age were used. Under a microscopic field of view, EOC cells (1 x 105 cells/&#181;l of medium-extracellular matrix (ECM)-based hydrogel/unilateral ovary/mouse) were injected into murine ovaries through a retroperitoneal approach from the dorsal flank. This proposed method is a less invasive procedure for the mouse and minimizes damage to the ovary. Here, we describe the methodological steps in the development of the original and metastatic tumor formation of EOC.

Murine Experimental Model of Original Tumor Development and Peritoneal Metastasis via Orthotopic Inoculation with Ovarian Carcinoma Cells

To clarify the multistep process of peritoneal dissemination of ovarian carcinoma, the current study presents a murine experimental model of original tumor development and peritoneal metastasis via orthotopic inoculation with these tumor cells.

Epithelial ovarian carcinoma (EOC) is associated with a poor prognosis because it shows peritoneal dissemination. To improve the prognosis, it is ...

A Murine Orthotopic Bladder Tumor Model and Tumor Detection System

This protocol describes the generation of bladder tumors in female C57BL/6J mice using the murine bladder cancer cell line MB49, which has been modified to secrete human Prostate Specific Antigen (PSA), and the procedure for the confirmation of tumor implantation. In brief, mice are anesthetized using injectable drugs and are made to lay in the dorsal position. Urine is vacated from the bladder and 50 &#181;L of poly-L-lysine (PLL) is slowly instilled at a rate of 10 &#181;L/20 s using a 24 G IV catheter. It is left in the bladder for 20 min by stoppering the catheter. The catheter is removed and PLL is vacated by gentle pressure on the bladder. This is followed by instillation of the murine bladder cancer cell line (1 x 105 cells/50 &#181;L) at a rate of 10 &#181;L/20 s. The catheter is stoppered to prevent premature evacuation. After 1 h, the mice are revived with a reversal drug, and the bladder is vacated. The slow instillation rate is important, as it reduces vesico-ureteral reflux, which can cause tumors to occur in the upper urinary tract and in the kidneys. The cell line should be well re-suspended to reduce clumping of cells, as this can lead to uneven tumor sizes after implantation.
This technique induces tumors with high efficiency. Tumor growth is monitored by urinary PSA secretion. PSA marker monitoring is more reliable than ultrasound or fluorescence imaging for the detection of the presence of tumors in the bladder. Tumors in mice generally reach a maximum size that negatively impacts health by about 3 - 4 weeks if left untreated. By monitoring tumor growth, it is possible to differentiate mice that were cured from those that were not successfully implanted with tumors. With only end-point analysis, the latter may be mistakenly assumed to have been cured by therapy.

This protocol describes the generation of murine orthotopic bladder tumors in female C57BL/6J mice and the monitoring of tumor growth.

This protocol describes the generation of bladder tumors in female C57BL/6J mice using the murine bladder cancer cell line MB49, which has been modified ...

Using CRISPR/Cas9 Gene Editing to Investigate the Oncogenic Activity of Mutant Calreticulin in Cytokine Dependent Hematopoietic Cells

Clustered regularly interspaced short palindromic repeats (CRISPR) is an adaptive immunity system in prokaryotes that has been repurposed by scientists to generate RNA-guided nucleases, such as CRISPR-associated (Cas) 9 for site-specific eukaryotic genome editing. Genome engineering by Cas9 is used to efficiently, easily and robustly modify endogenous genes in many biomedically-relevant mammalian cell lines and organisms. Here we show an example of how to utilize the CRISPR/Cas9 methodology to understand the biological function of specific genetic mutations. We model calreticulin (CALR) mutations in murine interleukin-3 (mIL-3) dependent pro-B (Ba/F3) cells by delivery of single guide RNAs (sgRNAs) targeting the endogenous Calr locus in the specific region where insertion and/or deletion (indel) CALR mutations occur in patients with myeloproliferative neoplasms (MPN), a type of blood cancer. The sgRNAs create double strand breaks (DSBs) in the targeted region that are repaired by non-homologous end joining (NHEJ) to give indels of various sizes. We then employ the standard Ba/F3 cellular transformation assay to understand the effect of physiological level expression of Calr mutations on hematopoietic cellular transformation. This approach can be applied to other genes to study their biological function in various mammalian cell lines.

Targeted gene editing using CRISPR/Cas9 has greatly facilitated the understanding of the biological functions of genes. Here, we utilize the CRISPR/Cas9 methodology to model calreticulin mutations in cytokine-dependent hematopoietic cells in order to study their oncogenic activity.

Clustered regularly interspaced short palindromic repeats (CRISPR) is an adaptive immunity system in prokaryotes that has been repurposed by scientists to ...

A 3D Organotypic Melanoma Spheroid Skin Model

Malignant transformation of melanocytes, the pigment cells of human skin, causes formation of melanoma, a highly aggressive cancer with increased metastatic potential. Recently, mono-chemotherapies continue to improve by melanoma specific combination therapies with targeted kinase inhibitors. Still, metastatic melanoma remains a life-threatening disease because tumors exhibit primary resistance or develop resistance to novel therapies, thereby regaining tumorigenic capacity. In order to improve the therapeutic success of malignant melanoma, the determination of molecular mechanisms conferring resistance against conventional treatment approaches is necessary; however, it requires innovative cellular in vitro models. Here, we introduce an in vitro three-dimensional (3D) organotypic melanoma spheroid model that can portray the in vivo architecture of malignant melanoma and may warrant new insights into intra-tumoral as well as tumor-host interactions. The model incorporates defined numbers of mature and differentiated melanoma spheroids in a 3D human full skin reconstruction model consisting of primary skin cells. The cellular composition and differentiation status of the embedded melanoma spheroids is similar to the one of cutaneous melanoma metastasis in vivo. Using this organotypic melanoma spheroid model as a drug screening platform may support the identification of responders to selected combination therapies, while sparing the unnecessary treatment burden for non-responders, thereby increasing the benefit of therapeutic interventions.

Here, we present a protocol to generate a 3D organotypic melanoma spheroid skin model that recapitulates both the architecture and multicellular complexity of an organ/tumor in vivo but at the same time accommodates systematic experimental intervention.

Malignant transformation of melanocytes, the pigment cells of human skin, causes formation of melanoma, a highly aggressive cancer with increased ...

Digital Polymerase Chain Reaction Assay for the Genetic Variation in a Sporadic Familial Adenomatous Polyposis Patient Using the Chip-in-a-tube Format

The quantitative analysis of human genetic variation is crucial for understanding the molecular characteristics of serious medical conditions, such as tumors. Because digital polymerase chain reactions (PCR) enable the precise quantification of DNA copy number variants, they are becoming an essential tool for detecting rare genetic variations, such as drug-resistant mutations. It is expected that molecular diagnoses using digital PCR (dPCR) will be available in clinical practice in the near future; thus, how to efficiently conduct dPCR with human genetic material is a hot topic. Here, we introduce a method to detect Adenomatous polyposis coli (APC) somatic mosaicism using dPCR with the chip-in-a-tube format, which allows eight dPCR reactions to be simultaneously conducted. Care should be taken when filling and sealing the reaction mixture on the chips. This article demonstrates how to avoid the over- and underestimation of positive partitions. Furthermore, we present a simple procedure for collecting the dPCR product from the partitions on the chips, which can then be used to confirm the specific amplification. We hope that this methods report will help promote the dPCR with the chip-in-a-tube method in genetic research.

Digital polymerase chain reaction (PCR) is a useful tool for the high-sensitivity detection of single nucleotide variants and DNA copy number variants. Here, we demonstrate key considerations for measuring rare variants in the human genome using digital PCR with the chip-in-a-tube format.

The quantitative analysis of human genetic variation is crucial for understanding the molecular characteristics of serious medical conditions, such as ...

In Vitro Tumor Cell Rechallenge For Predictive Evaluation of Chimeric Antigen Receptor T Cell Antitumor Function

The field of chimeric antigen receptor (CAR) T cell therapy is rapidly advancing with improvements in CAR design, gene-engineering approaches and manufacturing optimizations. One challenge for these development efforts, however, has been the establishment of in vitro assays that can robustly inform selection of the optimal CAR T cell products for in vivo therapeutic success. Standard in vitro tumor-lysis assays often fail to reflect the true antitumor potential of the CAR T cells due to the relatively short co-culture time and high T cell to tumor ratio. Here, we describe an in vitro co-culture method to evaluate CAR T cell recursive killing potential at high tumor cell loads. In this assay, long-term cytotoxic function and proliferative capacity of CAR T cells is examined in vitro over 7 days with additional tumor targets administered to the co-culture every other day. This assay can be coupled with profiling T cell activation, exhaustion and memory phenotypes. Using this assay, we have successfully distinguished the functional and phenotypic differences between CD4+ and CD8+ CAR T cells against glioblastoma (GBM) cells, reflecting their differential in vivo antitumor activity in orthotopic xenograft models. This method provides a facile approach to assess CAR T cell potency and to elucidate the functional variations across different CAR T cell products.

Here, we describe an in vitro co-culture method to recursively challenge tumor-targeted T cells, which allows for phenotypic and functional analysis of antitumor T cell activity.

The field of chimeric antigen receptor (CAR) T cell therapy is rapidly advancing with improvements in CAR design, gene-engineering approaches and ...

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.

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.

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

A Three-Dimensional Spheroid Model to Investigate the Tumor-Stromal Interaction in Hepatocellular Carcinoma

The aggressiveness and lack of well-tolerated and widely effective treatments for advanced hepatocellular carcinoma (HCC), the predominant form of liver cancer, rationalize its rank as the second most common cause of cancer-related death. Preclinical models need to be adapted to recapitulate the human conditions to select the best therapeutic candidates for clinical development and aid the delivery of personalized medicine. Three-dimensional (3D) cellular spheroid models show promise as an emerging in vitro alternative to two-dimensional (2D) monolayer cultures. Here, we describe a 3D tumor spheroid&#160;model which exploits the ability of individual cells to aggregate when maintained in hanging droplets, and is more representative of an in vivo environment than standard monolayers. Furthermore, 3D spheroids can be produced by combining homotypic or heterotypic cells, more reflective of the cellular heterogeneity in vivo, potentially enabling the study of environmental interactions that can influence progression and treatment responses. The current research optimized the cell density to form 3D homotypic and heterotypic tumor spheroids by immobilizing cell suspensions on the lids of standard 10 cm3 Petri dishes. Longitudinal analysis was performed to generate growth curves for homotypic versus heterotypic tumor/fibroblasts spheroids. Finally, the proliferative impact of fibroblasts (COS7 cells) and liver myofibroblasts (LX2) on homotypic tumor (Hep3B) spheroids was investigated. A seeding density of 3,000 cells (in 20 &#181;L media) successfully yielded Huh7/COS7 heterotypic spheroids, which displayed a steady increase in size up to culture day 8, followed by growth retardation. This finding was corroborated using Hep3B homotypic spheroids cultured in LX2 (human hepatic stellate cell line) conditioned medium (CM). LX2 CM triggered the proliferation of Hep3B spheroids compared to control tumor spheroids. In conclusion, this protocol has shown that 3D tumor spheroids can be used as a simple, economical, and prescreen in vitro tool to study tumor-stromal interactions more comprehensively.

Comprehensive in vitro models that faithfully recapitulate the relevant human disease are lacking. The current study presents three-dimensional (3D) tumor spheroid creation and culture, a reliable in vitro tool to study the tumor-stromal interaction in human hepatocellular carcinoma.

The aggressiveness and lack of well-tolerated and widely effective treatments for advanced hepatocellular carcinoma (HCC), the predominant form of liver ...

Zebrafish Larvae as a Model to Evaluate Potential Radiosensitizers or Protectors

Zebrafish are extensively used in several kinds of research because they are one of the easily maintained vertebrate models and exhibit several features of a unique and convenient model system. As highly proliferative cells are more susceptible to radiation-induced DNA damage, zebrafish embryos are a front-line in vivo model in radiation research. In addition, this model projects the effect of radiation and different drugs within a short time, along with major biological events and associated responses. Several cancer studies have used zebrafish, and this protocol is based on the use of radiation modifiers in the context of radiotherapy and cancer. This method can be readily used to validate the effects of different drugs on irradiated and control (non-irradiated) embryos, thus identifying drugs as radio sensitizing or protective drugs. Although this methodology is used in most drug screening experiments, the details of the experiment and the toxicity assessment with the background of X-ray radiation exposure are limited or only briefly addressed, making it difficult to perform. This protocol addresses this issue and discusses the procedure and toxicity evaluation with a detailed illustration. The procedure describes a simple approach for using zebrafish embryos for radiation studies and radiation-based drug screening with much reliability and reproducibility.

The zebrafish has recently been exploited as a model to validate potential radiation modifiers. The present protocol describes the detailed steps to use zebrafish embryos for radiation-based screening experiments and some observational approaches to evaluate the effect of different treatments and radiation.

Zebrafish are extensively used in several kinds of research because they are one of the easily maintained vertebrate models and exhibit several features ...

Mapping the Tumor Immune Landscape: An In-Depth Multiplex IHC Analysis Protocol

Multiplex Immunohistochemical Analysis of the Spatial Immune Cell Landscape of the Tumor Microenvironment

The immune cell landscape of the tumor microenvironment potentially contains information for the discovery of prognostic and predictive biomarkers. Multiplex immunohistochemistry is a valuable tool to visualize and identify different types of immune cells in tumor tissues while retaining its spatial information. Here we provide detailed protocols to analyze lymphocyte, myeloid, and dendritic cell populations in tissue sections. Starting from cutting formalin-fixed paraffin-embedded sections, automatic multiplex staining procedures on an automated platform, scanning of the slides on a multispectral imaging microscope, to the analysis of images using an in-house-developed machine learning algorithm ImmuNet. These protocols can be applied to a variety of tumor specimens by simply switching tumor markers to analyze immune cells in different compartments of the sample (tumor versus invasive margin) and apply nearest-neighbor analysis. This analysis is not limited to tumor samples but can also be applied to other (non-)pathogenic tissues. Improvements to the equipment and workflow over the past few years have significantly shortened throughput times, which facilitates the future application of this procedure in the diagnostic setting.

Author Spotlight: Unlocking Insights into the Immune Cell Landscape of Tumors

This protocol describes in detail how immune cell characterization of the tumor microenvironment using multiplex immunohistochemistry is carried out.

The immune cell landscape of the tumor microenvironment potentially contains information for the discovery of prognostic and predictive biomarkers. ...