Name: an ex vivo brain slice model to study and target breast cancer brain metastatic tumor growth
Uploaded: 2021-09-22T13:00:00
Description: Watch this Scientific Journal Video about An Ex Vivo Brain Slice Model to Study and Target Breast Cancer Brain Metastatic Tumor Growth at JoVE.com

We want to thank Julia Farnan, Kayla Green, and Tiziana DeAngelis for their technical assistance. This work was supported in part by the Pennsylvania Commonwealth Universal Research Enhancement Grant Program (MJR, JGJ), UO1CA244303 (MJR), R01CA227479 (NLS), R00CA207855 (EJH), and W.W. Smith Charitable Trusts (EjH).

This protocol was approved and follows the animal care guidelines by the Drexel University College of Medicine Institutional Animal Care and Use Committee (IACUC). Nu/Nu athymic female mice (6-8 weeks old) were used in this study.
1. Intracranial injection of tumor cells
<ol>
	<li>Sterilize all equipment (tweezers, scissors, suturing scissors, hand drill) under a dry cycle of an autoclave for up to 45 min in sterilization pouches, including a sterilization indicator. If conducting surgeries ...

<ol>
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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=Heralding+a+new+paradigm+in+3D+tumor+modeling.">Heralding a new paradigm in 3D tumor modeling.</a> Biomaterials. 108, 197-213 (2016).</li><li>Parker, J. 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=A+human+glioblastoma+organotypic+slice+culture+model+for+study+of+tumor+cell+migration+and+patient-specific+effects+of+anti-invasive+drugs.">A human glioblastoma organotypic slice culture model for study of tumor cell migration and patient-specific effects of anti-invasive drugs.</a> Journal of Visualized Experiments: JoVE. (125), e53557 (2017).</li><li>Chuang, H. N., 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=Coculture+system+with+an+organotypic+brain+slice+and+3D+spheroid+of+carcinoma+cells.">Coculture system with an organotypic brain slice and 3D spheroid of carcinoma cells.</a> Journal of Visualized Experiments: JoVE. (80), e50881 (2013).</li><li>Hohensee, I., 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=PTEN+mediates+the+cross+talk+between+breast+and+glial+cells+in+brain+metastases+leading+to+rapid+disease+progression.">PTEN mediates the cross talk between breast and glial cells in brain metastases leading to rapid disease progression.</a> Oncotarget. 8 (4), 6155-6168 (2017).</li><li>van de Merbel, A. 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=An+ex+vivo+Tissue+culture+model+for+the+assessment+of+individualized+drug+responses+in+prostate+and+bladder+cancer.">An ex vivo Tissue culture model for the assessment of individualized drug responses in prostate and bladder cancer.</a> Frontiers in Oncology. 8, 400 (2018).</li><li>Martin, S. Z., 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=Ex+vivo+tissue+slice+culture+system+to+measure+drug-response+rates+of+hepatic+metastatic+colorectal+cancer.">Ex vivo tissue slice culture system to measure drug-response rates of hepatic metastatic colorectal cancer.</a> BMC Cancer. 19 (1), 1030 (2019).</li><li>Orimo, A., Weinberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stromal+fibroblasts+in+cancer:+a+novel+tumor-promoting+cell+type.">Stromal fibroblasts in cancer: a novel tumor-promoting cell type.</a> Cell Cycle. 5 (15), 1597-1601 (2006).</li><li>Lim, C. 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=Organotypic+slice+cultures+of+pancreatic+ductal+adenocarcinoma+preserve+the+tumor+microenvironment+and+provide+a+platform+for+drug+response.">Organotypic slice cultures of pancreatic ductal adenocarcinoma preserve the tumor microenvironment and provide a platform for drug response.</a> Pancreatology. 18 (8), 913-927 (2018).</li><li>Gerlach, M. 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G., 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=Neuronal+activity+and+glutamate+uptake+decrease+mitochondrial+mobility+in+astrocytes+and+position+mitochondria+near+glutamate+transporters.">Neuronal activity and glutamate uptake decrease mitochondrial mobility in astrocytes and position mitochondria near glutamate transporters.</a> Journal of Neuroscience. 34 (5), 1613-1624 (2014).</li><li>Farnan, J. K., Green, K. K., Jackson, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+imaging+of+mitochondrial+dynamics+and+trafficking+in+astrocytes.">Ex vivo imaging of mitochondrial dynamics and trafficking in astrocytes.</a> Current Protocols in Neuroscience. 92 (1), 94 (2020).</li><li>Simone, N. 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=Ionizing+radiation-induced+oxidative+stress+alters+miRNA+expression.">Ionizing radiation-induced oxidative stress alters miRNA expression.</a> PLoS One. 4 (7), 6377 (2009).</li><li>Couturier, C. P., 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=Single-cell+RNA-seq+reveals+that+glioblastoma+recapitulates+a+normal+neurodevelopmental+hierarchy.">Single-cell RNA-seq reveals that glioblastoma recapitulates a normal neurodevelopmental hierarchy.</a> Nature Communications. 11 (1), 3406 (2020).</li><li>Candolfi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracranial+glioblastoma+models+in+preclinical+neuro-oncology:+neuropathological+characterization+and+tumor+progression.">Intracranial glioblastoma models in preclinical neuro-oncology: neuropathological characterization and tumor progression.</a> Journal of Neuro-Oncology. 85 (2), 133-148 (2007).</li><li>Fitzgerald, D. P., 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=Reactive+glia+are+recruited+by+highly+proliferative+brain+metastases+of+breast+cancer+and+promote+tumor+cell+colonization.">Reactive glia are recruited by highly proliferative brain metastases of breast cancer and promote tumor cell colonization.</a> Clinical &amp; Experimental Metastasis. 25 (7), 799-810 (2008).</li><li>Kondru, N., 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=An+Ex+Vivo+Brain+Slice+Culture+Model+of+Chronic+Wasting+Disease:+Implications+for+Disease+Pathogenesis+and+Therapeutic+Development.">An Ex Vivo Brain Slice Culture Model of Chronic Wasting Disease: Implications for Disease Pathogenesis and Therapeutic Development.</a> Scientific Reports. 10 (1), (2020).</li><li>Abu Samaan, T. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paclitaxel's+mechanistic+and+clinical+effects+on+breast+cancer.">Paclitaxel's mechanistic and clinical effects on breast cancer.</a> Biomolecules. 9 (12), (2019).</li><li>Mewes, A., Franke, H., Singer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organotypic+brain+slice+cultures+of+adult+transgenic+P301S+mice--a+model+for+tauopathy+studies.">Organotypic brain slice cultures of adult transgenic P301S mice--a model for tauopathy studies.</a> PLoS One. 7 (9), 45017 (2012).</li><li>Valiente, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain+metastasis+cell+lines+panel:+A+public+resource+of+organotropic+cell+lines.">Brain metastasis cell lines panel: A public resource of organotropic cell lines.</a> Cancer Research. 80 (20), 4314-4323 (2020).</li></ol>

This study establishes a novel ex vivo brain culture method for explanted xenograft brain tumors. We show that BCBM cells MDA-MB-231BR cells intracranially injected in the brain of mice can survive and grow in ex vivo brain slices. The study also tested intracranially injected U87MG glioblastoma (GBM) cells and also found that these cancer cells survive and grow in brain slices (data not shown). We believe this model can be expanded beyond BCBM and GBM to other cancers that readily metastasize to the br...

Breast cancer brain metastases (BCBM) develop when cells spread from the primary breast tumor to the brain. Breast cancer is the second most frequent cause of brain metastasis after lung cancer, with metastases occurring in 10-16% of patients1. Unfortunately, brain metastases remain incurable as &#62;80% of patients die within a year after their brain-metastasis diagnosis, and their quality of life is impaired due to neurological dysfunctions2. There is an urgent need to identify more effective treatment options. Monolayer two-dimensional or three-dimensional culture models are the most commonly used methods in testing therapeutic agents in the laboratory. However, they do not mimic the complex BCBM microenvironment, a major driver of tumor phenotype and growth. Although these models are useful, they do not capture the complex tumor-stromal interactions, the unique metabolic requirements, and the heterogeneity of the tumors3. To more faithfully recapitulate tumor-stromal interactions and microenvironment heterogeneity, our group and others have begun to generate organotypic brain metastasis &#34;slice&#34; cultures with patient-derived tumor cells (primary or metastatic) or cancer cell lines4,5,6. Compared to classical in vitro systems, this short-term ex vivo model may provide more relevant conditions for screening new therapeutics prior to preclinical assessment in large animal cohorts.
Ex vivo models have been constructed and successfully used primarily for the identification of successful treatments of various cancers. They require few days of assessment and additionally can be tailored to patient-specific drug screening. For example, human bladder and prostate cancer ex vivo tissues have shown a dose-dependent anti-tumor response of docetaxel and gemcitabine7. Similar colorectal carcinoma ex vivo tissues were developed to screen chemotherapeutic drugs Oxaliplatin, Cetuximab, and Pembrolizumab8. This application has been widely used in pancreatic cancer, considering the essential interaction between the stromal environment and the genotypic and phenotypic characteristics of pancreatic ductal adenocarcinoma9,10. Furthermore, such organotypic models have been developed for similar screenings in head, neck, gastric, and breast tumors11,12.
Here, an ex vivo brain slice model of xenografted breast cancer brain metastatic tumor cells in their microenvironment is being generated. Mice were intracranially injected with breast cancer brain metastatic brain trophic MDA-MB-231BR cells13 in the cerebral cortex parietal lobe- a common site of TNBC metastasis14,15 and allowed to develop tumors. Brain slices were generated from these xenografted animals and maintained ex vivo as organotypic cultures as described16,17. This novel ex vivo model allows for the analysis of BCBM cell&#39;s growth within the brain parenchyma and can be used to test therapeutic agents and radiation effects on tumor cells within the brain microenvironment.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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		<tr>
			<td>1 mL syringe, slip tip</td>
			<td>BD</td>
			<td>309659</td>
			<td></td>
		</tr>
		<tr>
			<td>30 G1/2 Needles</td>
			<td>BD</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plates</td>
			<td>Genessee</td>
			<td>25-105</td>
			<td></td>
		</tr>
		<tr>
			<td>Automated microscope and LUMAVIEW software</td>
			<td>Etaluma</td>
			<td>LS720</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 (GEM21)</td>
			<td>Gemini Bio-Products</td>
			<td>400-160</td>
			<td></td>
		</tr>
		<tr>
			<td>Beaker 50 mL</td>
			<td>Fisher</td>
			<td>10-210-685</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt sable paintbrush, Size #5/0</td>
			<td>Electron Microscopy Sciences</td>
			<td>66100-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Bone Wax</td>
			<td>ModoMed</td>
			<td>DYNJBW25</td>
			<td></td>
		</tr>
		<tr>
			<td>Brain injection Syringe</td>
			<td>Hamilton Company</td>
			<td>80430</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Fisher Scientific</td>
			<td>BP510-250</td>
			<td></td>
		</tr>
		<tr>
			<td>Cleaved caspase 3 Antibody</td>
			<td>Cell Signaling</td>
			<td>14220S</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Invitrogen</td>
			<td>P36935</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Luciferin Potassium Salt</td>
			<td>Perkin Elmer</td>
			<td>122799</td>
			<td></td>
		</tr>
		<tr>
			<td>Double edge razor blade</td>
			<td>VWR</td>
			<td>55411-060(95-0043)</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Paper (#1), quantitative circles, 4.25 cm</td>
			<td>Fisher</td>
			<td>09-805a (1001-042)</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine sable paintbrush #2/0</td>
			<td>Electron Microscopy Sciences</td>
			<td>66100-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fine Science Tools</td>
			<td>11251-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Gamma-H2AX antibody</td>
			<td>Millipore</td>
			<td>05-636</td>
			<td></td>
		</tr>
		<tr>
			<td>GFAP antibody</td>
			<td>Thermo Fisher</td>
			<td>13-0300</td>
			<td></td>
		</tr>
		<tr>
			<td>GFP antibody</td>
			<td>Santa Cruz</td>
			<td>SC-9996</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma Aldrich</td>
			<td>G8270</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamine (200 mM)</td>
			<td>Corning cellgrow</td>
			<td>25-005-Cl</td>
			<td></td>
		</tr>
		<tr>
			<td>H&#38;E and KI-67</td>
			<td>Jefferson Core Facility Pathology staining</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hand Drill Set with Micro Mini Twist Drill Bits</td>
			<td>Amazon</td>
			<td>YCQ2851920086082DJ</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES, free acid</td>
			<td>Fisher Scientific</td>
			<td>BP299-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Just for mice Stereotaxic Frame</td>
			<td>Harvard Apparatus (Holliston, MA, USA).</td>
			<td>72-6049, 72-6044</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Fisher Scientific</td>
			<td>S271-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Large surgical scissors</td>
			<td>Fine Science Tools</td>
			<td>14001-18</td>
			<td></td>
		</tr>
		<tr>
			<td>MDA-MB-231BR cells</td>
			<td>Kindly provided by Dr. Patricia Steeg</td>
			<td>Ref 14</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2&#183;6H2O</td>
			<td>Fisher Scientific</td>
			<td>M33-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Mice imaging device</td>
			<td>Perkin Elmer</td>
			<td>IVIS 200 system</td>
			<td></td>
		</tr>
		<tr>
			<td>Mice imaging software</td>
			<td>Caliper Life Sciences (Waltham, MA, USA).</td>
			<td>Living Image Software</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate Reader</td>
			<td>Tecan Spark</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mounting solution</td>
			<td>Invitrogen</td>
			<td>P36935</td>
			<td></td>
		</tr>
		<tr>
			<td>MTS reagent</td>
			<td>Promega CellTiter 96 Aqueous One Solution</td>
			<td>(Cat:G3582)</td>
			<td></td>
		</tr>
		<tr>
			<td>N2 supplement</td>
			<td>Life Technologies</td>
			<td>17502-048</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal medium</td>
			<td>Life Technologies</td>
			<td>21103049</td>
			<td></td>
		</tr>
		<tr>
			<td>Nu/Nu athymic mice</td>
			<td>Charles Rivers Labs (Wilmington, MA, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Affymetrix</td>
			<td>19943</td>
			<td></td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>Life Technologies</td>
			<td>145140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Polypropylene Suture</td>
			<td>Medex supply</td>
			<td>ETH-8556H</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone Iodine Swab sticks</td>
			<td>DME Supply USA</td>
			<td>Cat: 689286X</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel blade #11 (pk of 100)</td>
			<td>Fine Science Tools</td>
			<td>10011-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel handle #3</td>
			<td>Fine Science Tools</td>
			<td>10003-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Pyruvate</td>
			<td>Sigma Aldrich</td>
			<td>S8636</td>
			<td></td>
		</tr>
		<tr>
			<td>Spatula/probe</td>
			<td>Fine Science Tools</td>
			<td>10090-13</td>
			<td></td>
		</tr>
		<tr>
			<td>SS Double edge uncoated razor blades (American safety razor co (95-0043))</td>
			<td>VWR</td>
			<td>55411-060</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Amresco</td>
			<td>57-50-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Scalpel</td>
			<td>Exelint International</td>
			<td>D29702</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Chopper</td>
			<td>Brinkman</td>
			<td>(McIlwain type)</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue culture inserts</td>
			<td>Millipore</td>
			<td>PICMORG50 or PICM03050</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray machine</td>
			<td>Precision 250 kVp</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
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an ex vivo brain slice model to study and target breast cancer brain metastatic tumor growth

Brain metastasis is a serious consequence of breast cancer for women as these tumors are difficult to treat and are associated with poor clinical outcomes. Preclinical mouse models of breast cancer brain metastatic (BCBM) growth are useful but are expensive, and it is difficult to track live cells and tumor cell invasion within the brain parenchyma. Presented here is a protocol for ex vivo brain slice cultures from xenografted mice containing intracranially injected breast cancer brain-seeking clonal sublines. MDA-MB-231BR luciferase tagged cells were injected intracranially into the brains of Nu/Nu female mice, and following tumor formation, the brains were isolated, sliced, and cultured ex vivo. The tumor slices were imaged to identify tumor cells expressing luciferase and monitor their proliferation and invasion in the brain parenchyma for up to 10 days. Further, the protocol describes the use of time-lapse microscopy to image the growth and invasive behavior of the tumor cells following treatment with ionizing radiation or chemotherapy. The response of tumor cells to treatments can be visualized by live-imaging microscopy, measuring bioluminescence intensity, and performing histology on the brain slice containing BCBM cells. Thus, this ex vivo slice model may be a useful platform for rapid testing of novel therapeutic agents alone or in combination with radiation to identify drugs personalized to target an individual patient&#39;s breast cancer brain metastatic growth within the brain microenvironment.

MDA-MB-231BR-GFP-Luciferase cells were intracranially injected into the right hemisphere of 4-6 week old Nu/Nu mice as explained above (Figure 1A) and were allowed to grow for 12-14 days, during which time tumor growth was monitored by bioluminescence imaging (Figure 1B). We injected 100,000 cancer cells intracranially as reported by other groups19, but it&#39;s possible to inject as low as 20,000 cell20. Following...

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An Ex Vivo Brain Slice Model to Study and Target Breast Cancer Brain Metastatic Tumor Growth

We introduce a protocol for measuring real-time drug and radiation response of breast cancer brain metastatic cells in an organotypic brain slice model. The methods provide a quantitative assay to investigate the therapeutic effects of various treatments on brain metastases from breast cancer in an ex vivo manner within the brain microenvironment interface.

An Ex Vivo Brain Slice Model to Study and Target Breast Cancer Brain Metastatic Tumor Growth

Brain metastasis is a serious consequence of breast cancer for women as these tumors are difficult to treat and are associated with poor clinical ...

This protocol allows for the formation of brain metastatic tumor cells and the generation of ex vivo brain slices that allows for rapid testing of drug efficacy and radiation on a preformed tumor. The main advantage of this technique is the ability to rapidly test multiple drugs or treatments in a physiologically relevant setting that maintains brain-tumor-host interactions. This method may help understand how brain metastatic cells grow, survive, and invade the brain parenchyma and understand the role of the brain tumor microenvironment in cancer growth and spread.Demonstrating the procedure will be Lorela Ciraku and Emily Esquea, both PhD candidates from my laboratory. To begin, with place the anesthetized mice into a stereotaxic frame and immobilize the head using standard ear bars. Sterilize the surface of the head thrice by repeated alternating application of iodine swabs and 70%ethanol prior to incision.Using a surgical scalpel, make a one-centimeter midline incision at a diagonal angle to the imaginary axis dividing the mice's brain into two symmetrical halves to expose the skull. After wiping any blood with a cotton swab, deflect the skin laterally to expose the injection site. Use a 0.73 millimeter burr bit to penetrate the skull and drill a hole using slight pressure and twisting motion.To inject five microliters of cells stably expressing GFP luciferase, insert a high-precision syringe to 3.5 millimeters depth in the brain. Allow it to settle for two minutes and then pull the syringe up about one millimeter. After two minutes, slowly inject the first half-volume and wait for another two minutes before injecting the rest of the volume.After three minutes, slowly pull the syringe. Apply bone wax to the injection site on the skull and suture the tissue with polypropylene sutures. Monitor the behavior of the mouse right after the surgery periodically to determine if special treatment, including saline injection and soft food, are needed to help quick recovery.To monitor the tumor growth via bioluminescence imaging, first turn on the oxygen and isoflurane on the imaging system and allow both to be distributed to the separate chamber outside of the imaging box. Then, after turning on the software and initializing the instrument, choose the appropriate option for visualizing and capturing the whole mouse body. Next, transfer the mice to the chamber outside the imaging box supplied with oxygen and isoflurane.Once the mice are under the anesthetic effect, inject the mice intraperitoneally with 200 microliters of 30 milligrams per milliliter of luciferin. Place the mice in the imaging chamber with stomach facing down to the imaging chambers nose lip. Lock the chamber, choose two minutes time exposure to start imaging, and then complete the imaging.After placing the tissue slicer in a sterile laminar flow hood, clean all the tools and instruments with 70%ethanol. After euthanizing the mouse, remove and place the brain rapidly into ice-cold sucrose-ACSF solution. Using a spatula, transfer the brain on an ACSF-wetted filter paper on a 60-millimeter dish lid.Using a sharp, sterile razor blade, cut the excess parts of the brain that do not contain any tumor, including the bottom part of the brain, to bring the shape of the brain to a non-perfect cube. After placing several sheets of ACSF-wetted filter paper onto the cutting platform, place the blocked tissue upon the filter paper. To slice the tissue into 200-to 250-micrometers-thick sections, set the cut size to 2 or 2.5 units on the provider ruler and start cutting.Use a paint brush to transfer brain slices into a dish containing sucrose-ACSF and separate the slices under a light microscope using 27-gauge needles. Identify the GFP-positive slices under the fluorescent microscope. Then, using a sterile one-milliliter broken-off pipette with a wide opening, transfer identified slices to a new 60-millimeter dish containing two to three milliliters of adult slice media.Then, transfer three to five slices onto each tissue culture insert in each well of a six-well plate at a safe distance. After removing the excess medium from the surface of the insert, add one milliliter of equilibrated adult mouse slice medium underneath each insert. Incubate the tissues at 37 degrees Celsius, 5%carbon dioxide, and 95%humidity for 24 hours before imaging.Pipette five microliters of 30 milligrams per milliliter luciferin solution into the medium underneath the inserts inside a sterile hood. Place the six-well plate with the lid inside the imaging chamber of the instrument below the stationary camera and lock the chamber door. Open the software and initialize the instrument.After choosing camera settings allowing visualization and capturing of only one well per image, place the well to be imaged directly under the camera. Use the ROI tool, fit it around the tumor shape and size, measure the ROI, and report the total readings to quantify the bioluminescent signal of each tumor on the slice. After bringing the plate back to the sterile laminar flow hood, use forceps to slightly lift the insert from the well.After aspirating the medium, replace the medium with one milliliter of fresh medium and place the inset back in the well. For the experiments where the slices are treated with various compounds, such as inhibitors and metabolites, prepare the appropriate reagent concentration in 1.2 milliliters of brain slice media in a 1.5-milliliter tube, and then transfer one milliliter of reagent to the well containing the slice. The MDA-MB-231 BR-GFP luciferase cells were injected into nude mice, tumors were allowed to grow, brains with tumors were dissected out, sliced, grown ex vivo, and tumor growth was monitored by bioluminescence imaging.The H&E staining and GFP-positive fluorescence confirmed the presence of a tumor in the brain slice. The increased Ki-67 staining confirmed the presence of highly proliferative cancer cells. The tumors in brain slices that were not exposed to irradiation continued to grow ex vivo, while tumors exposed to irradiation showed a stalled growth.Brain slices containing tumors were also monitored via live imaging to visualize the tumor growth following the irradiation treatment. Consistent with the bioluminescent imaging, control cancer cells rapidly grew as GFP intensity increased and the cells started invading the brain parenchyma. In contrast, the cancer cells in brain slices treated with irradiation were cytostatic and GFP intensity was maintained.Large multi-nucleated cancer cells and an increase in staining of DNA damage marker in IR-treated cancer cells were detected. Also, an increase in reactive astrocytes was detected. The IR treatment-induced apoptosis was not detected in the tumor-free mouse brain slices.The brain slices containing tumors were treated with different concentrations of paclitaxel, a chemotherapeutic drug. Treatment decreased the tumor's size significantly following day 10 of treatment. An increase in apoptosis was detected in paclitaxel-treated tumor cells.The inhibitor treatment did not alter brain tissue viability. No increase in apoptosis was measured by cleaved caspase-3 staining in paclitaxel-treated tumor-free mouse brain slice. When the treatment with the drugs of interest has terminated, slices can be analyzed for protein expression through immunocytochemistry, omic studies, or achieve single-cell suspension suitable for flow cytometry.

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