Name: simultaneous imaging and flow-cytometry-based detection of multiple fluorescent senescence markers in therapy-induced senescent cancer cells
Uploaded: 2022-07-12T14:30:00
Description: Watch this Scientific Journal Video about Simultaneous Imaging and Flow-Cytometry-based Detection of Multiple Fluorescent Senescence Markers in Therapy-Induced Senescent Cancer Cells at JoVE.com

This work was supported by a grant to Yong Yu from Johannes Kepler University Linz (BERM16108001).

1. DLBCL cell lines with mafosfamide or daunorubicin treatment to induce cellular senescence
NOTE: The protocol also works for adherent cancer cells. Depending on cell size, seed 1-2 &#215; 105 cells into one well of a 6-well plate and incubate the plate in a 5% CO2, 37 &#176;C incubator overnight before treatment. The protocol steps are the same as for suspension cells but with two exceptions. First, cells need to be trypsinized off the plate after step 3....

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This method examined the senescence-entering capability of four different DLBCL cell lines upon chemotherapy treatment, with bright-field imaging and flow cytometry-based quantification. On a single-cell level, we successfully detected major C12FDG+EdU-Ki67+ senescent populations in treated KARPAS422 and WSU-DLCL2 cells, and to a lesser extent in OCI-LY1 cells, while the SU-DHL6 cell line was resistant to the treatment. The difference in senescence-entering capability among cel...

A variety of stimuli can trigger cellular senescence, causing cells to enter a state of stable cell cycle arrest. These stimuli include intrinsic signaling changes or extrinsic stresses. Intrinsic signals include progressive telomere shortening, changes in telomere structure, epigenetic modification, proteostasis disorders, mitochondrial dysfunction, and activation of oncogenes. Extrinsic stresses include inflammatory and/or tissue damage signals, radiation or chemical treatment, and nutritional deprivation1,2,3,4. Among distinct types of senescence, the most commonly seen and well-studied are replicative senescence, oncogene-induced senescence (OIS), radiation-induced senescence, and therapy-induced senescence (TIS). OIS is an acute cellular response to genotoxic damage caused by replicative stress generated by aberrant oncogene activation and can to some extent prevent the pathological progression from a preneoplastic lesion to a full-blown tumor. TIS happens when tumor cells are stressed by chemotherapeutic drugs or ionizing radiation5,6.
Senescence is considered a double-edged sword in pathology due to its highly dynamic nature. It was initially described as a beneficial tumor-suppressive mechanism to remove damaged cells from the circulating pool of dividing cells, safeguarding the normal function of organs and inhibiting tumor growth7,8,9. However, emerging evidence has suggested a dark side of senescence. Senescent cells secrete proinflammatory cytokines, known as senescence-associated secretory phenotype (SASP), leading to fibrosis and malfunctional organs and promoting tumor initiation and progression10. Moreover, senescent cancer cells undergo epigenetic and gene-expression reprogramming in parallel with chromatin remodeling and activation of a sustained DNA-damage response (DDR)11,12, newly acquiring new cancer-stem-cell properties3. Although senescence-capable tumors respond better to therapeutic intervention compared to senescence-incapable ones13, the persistence of senescent cells may lead to a poor long-term prognosis if they are not effectively identified and eliminated by senolytic drugs5. Either way, a reliable method to assess senescence is of significant clinical interest, not only for the prognosis of therapy treatment but also for the development of novel strategies targeting senescent cells.
Regardless of different triggers, senescent cells exhibit some common features, including enlarged, flattened, multinucleated morphology with big vacuoles, significantly expanded nuclei, formation of H3K9me3-rich senescence-associated heterochromatin (SAHF) in the nucleus, persistent accumulation of DNA damage marker &#947;H2AX foci, activated p53-p21CIP1 and Rb-p16INK4a cell cycle regulatory mechanisms, stable G1 cell cycle arrest, massive induction of SASP, and elevated senescence-associated &#946;-galactosidase (SA-&#946;-gal) activity14. Since no single marker is sufficient to define senescence, enzymatic staining for SA-&#946;-gal activity, which is considered the gold standard for senescence detection, is usually combined with immunohistochemical staining for H3K9me3 and Ki67 to detect TIS15. However, chemical chromogenic-based SA-&#946;-gal is difficult to quantify. Here, we combined 5-dodecanoylaminofluorescein-di-&#946;-D-galactopyranoside (C12FDG) fluorescence-based SA-&#946;-gal (fSA-&#946;-gal) detection with immunofluorescent staining for &#947;H2AX and EdU-incorporated DNA to identify C12FDG+EdU-&#947;H2AX+ senescent cells using the advanced imaging flow cytometer system, which combines the speed, sensitivity and detailed single-cell images with spatial information that cannot be provided by flow cytometry and microscopy. This method enables rapid generation of high-resolution images allowing for the positioning and quantification of fluorescent signals within cells, while licensing the swift analysis of multiple samples by building standard pipelines.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alexa Fluor 647 anti-H2A.X Phospho (Ser139) Antibody</td>
			<td>Biolegend</td>
			<td>613407</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Ki-67 Mouse Monoclonal Antibody (Alexa Fluor 647)</td>
			<td>Biolegend</td>
			<td>350509</td>
			<td></td>
		</tr>
		<tr>
			<td>C12FDG (5-Dodecanoylaminofluorescein Di-&#946;-D-Galactopyranoside)</td>
			<td>Fisher Scientific</td>
			<td>11590276</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroquin -diphosphat</td>
			<td>Sigma aldrich</td>
			<td>C6628</td>
			<td></td>
		</tr>
		<tr>
			<td>Cleanser (Coulter Clenz)</td>
			<td>Beckman Coulter</td>
			<td>8546929</td>
			<td></td>
		</tr>
		<tr>
			<td>Click-iT EdU Pacific Blue Flow Cytometry Assay Kit</td>
			<td>Thermo Scientific</td>
			<td>C10418</td>
			<td></td>
		</tr>
		<tr>
			<td>Daunorubicin</td>
			<td>Medchemexpress</td>
			<td>HY-13062A</td>
			<td></td>
		</tr>
		<tr>
			<td>Debubbler (70% Isopropanol)</td>
			<td>Millipore</td>
			<td>1.3704</td>
			<td></td>
		</tr>
		<tr>
			<td>Image Analysis software (Amnis&#160;IDEAS&#160;6.3)</td>
			<td>Luminex</td>
			<td>CN-SW69-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Instrument and imaging software (Amnis&#160;ImageStreamX&#160;Mk II Imaging Flow Cytometer System and INSPIRE software)</td>
			<td>Luminex</td>
			<td>100220</td>
			<td></td>
		</tr>
		<tr>
			<td>KARPAS</td>
			<td>DSMZ</td>
			<td>ACC 31</td>
			<td></td>
		</tr>
		<tr>
			<td>mafosfamide cyclohexylamine</td>
			<td>Niomech</td>
			<td>D-17272</td>
			<td></td>
		</tr>
		<tr>
			<td>OCI-LY1</td>
			<td>DSMZ</td>
			<td>ACC 722</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Fisher Scientific</td>
			<td>11473704</td>
			<td></td>
		</tr>
		<tr>
			<td>PETG (2-Phenylethyl-&#946;-D-thiogalactosid)&#160;</td>
			<td>Sigma aldrich</td>
			<td>P4902</td>
			<td></td>
		</tr>
		<tr>
			<td>saponin</td>
			<td>Sigma aldrich</td>
			<td>47036</td>
			<td></td>
		</tr>
		<tr>
			<td>Sheath</td>
			<td>Millipore</td>
			<td>BSS-1006-B</td>
			<td></td>
		</tr>
		<tr>
			<td>SpeedBead Kit for ImageStream</td>
			<td>Luminex</td>
			<td>400041</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilizer (0.4-0.7% Hypochlorite)</td>
			<td>VWR</td>
			<td>JT9416-1</td>
			<td></td>
		</tr>
		<tr>
			<td>SU-DHL6</td>
			<td>DSMZ</td>
			<td>ACC 572</td>
			<td></td>
		</tr>
		<tr>
			<td>WSU-DLCL2</td>
			<td>DSMZ</td>
			<td>ACC 575</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

A compensation matrix was generated using image analysis software by loading recorded data of single-color control samples. As shown in Supplemental Figure S1, a non-negligible (coefficient value &#8805; 0.1) light spillover from EdU to C12FDG was detected with crosstalk coefficient value 0.248, while the crosstalk among other channels was not significant. Four different DLBCL cell lines were treated with 5 &#181;g/mL MAF or 20 ng/mL DN to induce cellular senescence and analyzed using either c...

Watch this Scientific Journal Video about Simultaneous Imaging and Flow-Cytometry-based Detection of Multiple Fluorescent Senescence Markers in Therapy-Induced Senescent Cancer Cells at JoVE.com

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

This method can rapidly generate high resolution images that allow an analysis of spatial distribution and quantification of fluorescent signals within cells while allowing rapid analysis of multiple samples. Cells are measured using the advanced imaging flow cytometry system, combining speed, sensitivity and detailed single cell images with spatial information yielding unique data that cannot be provided by flows optometry or microscopy. One important advice is to provide enough cells to establish the instrument settings and we suspend the cells at the high density for the measurements.Apart from this data acquisition is straightforward and similar to conventional flow cytometry. First generate the DLBCL cell lines as described in the manuscript. Then add 10 millimolar EdU solution at a ratio of one to 1000 into the DLBCL cell culture and incubate the plate in a 5%carbon dioxide incubator at 37 degrees Celsius for three hours after mixing the plate by gentle rocking.Take the plate out after incubation and add 100 millimolar chloroquine solution to a final concentration of 75 micromolar. Mix by rocking gently and incubate for 30 minutes. Then add 20 millimolar C12 FDG solutions to a final concentration of 20 micromolar.After gentle mixing, incubate the plate for one hour as demonstrated previously. Next, add 100 millimolar 2-phenylethyl-beta-d-thiogalactoside solution at one to 50 to stop the FSA beta-gal staining. And gently rotate the plate to mix.Transfer the cells to 15 milliliter sterile centrifuge tubes and spin at 100 times G for five minutes at four degree Celsius. Once the supernatant is discarded, wash the cells with four milliliters of PBS and centrifuge at 100 times G for five minutes at four degrees Celsius. Then re-suspend the cell pellets in 500 microliters at 4%paraformaldehyde fixation solution.After 10 minute incubation at room temperature, centrifuge at 250 times G for five minutes at room temperature. Discard the supernatant and wash the cells with four milliliters of PBS twice and centrifuge at 100 times G for five minutes at room temperature. After washing, discard the supernatant and re-suspend the cell pellet in 200 microliters of saponin permeabilization buffer.Now transfer the suspension to a new 1.5 milliliter tube and incubate for 10 minutes at room temperature. Pellet the cells at 250 times G for five minutes at room temperature. Then re-suspend the cells in 200 microliters of primary antibody solution and incubate at four degree Celsius overnight, in the dark.Centrifuge the tubes at 250 times G for five minutes at four degrees Celsius. Discard the supernatant and wash with 100 microliters of saponin wash solution. After washing the cells twice, discard the supernatant and re-suspend the cell pellets in 500 microliters of EdU detection cocktail.Incubate at room temperature for 30 minutes in the dark and centrifuge at 250 times G for five minutes at room temperature. Discard the supernatant and wash with one milliliter of saponin wash solution. Repeat the washing two times, discard the supernatant and re-suspend the cell pellets in 20 to 50 microliters of PBS.Before turning on the instrument, empty the waste fluid bottle and check the levels of SpeedBeads, sterilizer, cleaner, debubbler and sheath sufficient fluids. After turning on the instrument and imaging software, click on the startup button to initialize fluidics and system calibration. Set the magnification to 40 times and set the fluidic speed to low.After switching on the lasers, turn on a 405 nanometers laser to measure EdU Pacific Blue, 488 nanometers to measure C12-FDG and 642 nanometers to measure Alexa-Fluor-647-gamma-H2AX. Set channel six for the scatter channel, channel one and channel nine for the bright-field. Then start with the sample expected to have the highest fluorescence to set up the intensity of the lasers and gently flip the sample tube to mix.After opening the tube lid, insert the sample tube onto the dock. Click on Load to start and open a scatter plot. Next, select the Features area, underscore MO1 and aspect ratio underscore MO1 for the X and Y axes respectively.Set a gate above aspect ratio of 0.5 to exclude doublets and cell aggregates below and on the right side and the SpeedBead population on the left side. Now, open Histogram Plot and select the feature gradient root mean square of mask one and channel one for the X axis. Choose the singlet population and set the gate to select for focused cells.Open a histogram plot and select raw max pixel intensities for X axis channel two, seven, and 11. Then adjust the the laser powers of 488 nanometers, 405 nanometers and 642 nanometers lasers for channel two, seven and 11 respectively so each fluorochrome has a raw max pixel value between 100 and 4, 000 to avoid oversaturation. Choose the focused population to record and click on Acquire to measure the DLBCL samples with consistent settings.When changing samples for measurement, click on return to recover the sample tube. Press Load to discard the sample. After all the samples are measured, turn off the bright-field and scatter laser.Measure single color control samples to generate a compensation matrix. Click on Shutdown to close the imaging system. Analyze the data in the image analysis software.Use the Spot Wizard tool of the image analysis software to automatically count and quantify nuclear gamma H2AX foci and live cell images. Select two cell populations, one with high and one with low spot count to train the Spot Wizard for further automatic spot count analysis. The flow cytometry method in single cell images showed increased C12-FDG positive, EdU negative, gamma H2AX positive, senesced population and KARPAS422.WSU-DLCL2 and OCI-LY1 cells, but not in SU-DHL6 cells. The imaging-based analysis presented significantly higher numbers of gamma H2AX foci and KARPAS422, WSU-DLCL2 and OCI-LY1, but not in SU-DHL6 cells. Similar results were represented by frequency and quantification data.Adding saponin to the cell suspension is crucial, otherwise the antibodies cannot reach the cell internal antigens and harsh detergents lead to loss of C12-FTG signal Imaging cytometry is optimal for analyzing changes in marker localization like translocation of a transcription factor to the nucleus in response to certain stimuli. Such an analysis can also be achieved with our protocol. This method allows to visualization of multiple fluorescent markers on a single-cell level which helps detect the presence, intensity and localization of the individual signals.

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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 ...

Multimodal Bioluminescent and Positronic-emission Tomography/Computational Tomography Imaging of Multiple Myeloma Bone Marrow Xenografts in NOG Mice

Multiple myeloma (MM) tumors engraft in the bone marrow (BM) and their survival and progression are dependent upon complex molecular and cellular interactions that exist within this microenvironment. Yet the BM microenvironment cannot be easily replicated in vitro, which potentially limits the physiologic relevance of many in vitro and ex vivo experimental models. These issues can be overcome by utilizing a xenograft model in which luciferase (LUC)-transfected 8226 MM cells will specifically engraft in the mouse skeleton. When these mice are given the appropriate substrate, D-luciferin, the effects of therapy on tumor growth and survival can be analyzed by measuring changes in the bioluminescent images (BLI) produced by the tumors in vivo. This BLI data combined with positronic-emission tomography/computational tomography (PET/CT) analysis using the metabolic marker 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG) is used to monitor changes in tumor metabolism over time. These imaging platforms allow for multiple noninvasive measurements within the tumor/BM microenvironment.

Here we use bioluminescent, X-ray, and positron-emission tomography/computed tomography imaging to study how inhibiting mTOR activity impacts bone marrow-engrafted myeloma tumors in a xenograft model. This allows for physiologically relevant, non-invasive, and multimodal analyses of the anti-myeloma effect of therapies targeting bone marrow-engrafted myeloma tumors in vivo.

Multiple myeloma (MM) tumors engraft in the bone marrow (BM) and their survival and progression are dependent upon complex molecular and cellular ...

Detection of Protease Activity by Fluorescent Peptide Zymography

The purpose of this method is to measure the proteolytic activity of complex biological samples. The samples are separated by molecular weight using electrophoresis through a resolving gel embedded with a degradable substrate. This method differs from traditional gel zymography in that a quenched fluorogenic peptide is covalently incorporated into the resolving gel instead of full length proteins, such as gelatin or casein. Use of the fluorogenic peptides enables direct detection of proteolytic activity without additional staining steps. Enzymes within the biological samples cleave the quenched fluorogenic peptide, resulting in an increase in fluorescence. The fluorescent signal in the gels is then imaged with a standard fluorescent gel scanner and quantified using densitometry. The use of peptides as the degradable substrate greatly expands the possible proteases detectable with zymographic techniques.

Here, we present a detailed protocol for a modified zymographic technique in which fluorescent peptides are used as the degradable substrate in place of native proteins. Electrophoresis of biological samples in fluorescent peptide zymograms enables detection of a wider range of proteases than previous zymographic techniques.

The purpose of this method is to measure the proteolytic activity of complex biological samples. The samples are separated by molecular weight using ...

Detection of Lung Tumor Progression in Mice by Ultrasound Imaging

With ~1.6 million victims per year, lung cancer contributes tremendously to the worldwide burden of cancer. Lung cancer is partly driven by genetic alterations in oncogenes such as the KRAS oncogene, which constitutes ~25% of lung cancer cases. The difficulty in therapeutically targeting KRAS-driven lung cancer partly stems from having poor models that can mimic the progression of the disease in the lab. We describe a method that permits the relative quantification of primary KRAS lung tumors in a Cre-inducible LSL-KRAS G12D mouse model via ultrasound imaging. This method relies on brightness (B)-mode acquisition of the lung parenchyma. Tumors that are initially formed in this model are visualized as B-lines and can be quantified by counting the number of B-lines present in the acquired images. These would represent the relative tumor number formed on the surface of the mouse lung. As the formed tumors develop with time, they are perceived as deep clefts within the lung parenchyma. Since the circumference of the formed tumor is well-defined, calculating the relative tumor volume is achieved by measuring the length and width of the tumor and applying them in the formula used for tumor caliper measurements. Ultrasound imaging is a non-invasive, fast and user-friendly technique that is often used for tumor quantifications in mice. Although artifacts may appear when obtaining ultrasound images, it has been shown that this imaging technique is more advantageous for tumor quantifications in mice compared to other imaging techniques such as computed tomography (CT) imaging and bioluminescence imaging (BLI). Researchers can investigate novel therapeutic targets using this technique by comparing lung tumor initiation and progression between different groups of mice.

This protocol describes the steps taken to induce KRAS lung tumors in mice as well as the quantification of formed tumors by ultrasound imaging. Small tumors are visualized in early timepoints as B-lines. At later timepoints, relative tumor volume measurements are achieved by the measurement tool in the ultrasound software.

With ~1.6 million victims per year, lung cancer contributes tremendously to the worldwide burden of cancer. Lung cancer is partly driven by genetic ...

In Vivo Targeting of Xenografted Human Cancer Cells with Functionalized Fluorescent Silica Nanoparticles in Zebrafish

Developing nanoparticles capable of detecting, targeting, and destroying cancer cells is of great interest in the field of nanomedicine. In vivo animal models are required for bridging the nanotechnology to its biomedical application. The mouse represents the traditional animal model for preclinical testing; however, mice are relatively expensive to keep and have long experimental cycles due to the limited progeny from each mother. The zebrafish has emerged as a powerful model system for developmental and biomedical research, including cancer research. In particular, due to its optical transparency and rapid development, zebrafish embryos are well suited for real-time in vivo monitoring of the behavior of cancer cells and their interactions with their microenvironment. This method was developed to sequentially introduce human cancer cells and functionalized nanoparticles in transparent Casper zebrafish embryos and monitor in vivo recognition and targeting of the cancer cells by nanoparticles in real time. This optimized protocol shows that fluorescently labeled nanoparticles, which are functionalized with folate groups, can specifically recognize and target metastatic human cervical epithelial cancer cells labeled with a different fluorochrome. The recognition and targeting process can occur as early as 30 min postinjection of the nanoparticles tested. The whole experiment only requires the breeding of a few pairs of adult fish and takes less than 4 days to complete. Moreover, zebrafish embryos lack a functional adaptive immune system, allowing the engraftment of a wide range of human cancer cells. Hence, the utility of the protocol described here enables the testing of nanoparticles on various types of human cancer cells, facilitating the selection of optimal nanoparticles in each specific cancer context for future testing in mammals and the clinic.

Described here is a method for utilizing zebrafish embryos to study the ability of functionalized nanoparticles to target human cancer cells in vivo. This method allows for the evaluation and selection of optimal nanoparticles for future testing in large animals and in clinical trials.

Developing nanoparticles capable of detecting, targeting, and destroying cancer cells is of great interest in the field of nanomedicine. In vivo animal ...

Immunofluorescence Imaging of DNA Damage and Repair Foci in Human Colon Cancer Cells

The purpose of the manuscript is to provide a step-by-step protocol for performing immunofluorescence microscopy to study the radiation-induced DNA damage response induced by neutron-gamma mixed-beam used in boron neutron capture therapy (BNCT). Specifically, the proposed methodology is applied for the detection of repair proteins activation which can be visualized as foci using antibodies specific to DNA double-strand breaks (DNA-DSBs). DNA repair foci were assessed by immunofluorescence in colon cancer cells (HCT-116) after irradiation with the neutron-mixed beam. DNA-DSBs are the most genotoxic lesions and are repaired in mammalian cells by two major pathways: non-homologous end-joining pathway (NHEJ) and homologous recombination repair (HRR). The frequencies of foci, immunochemically stained, for commonly used markers in radiobiology like &#947;-H2AX, 53BP1 are associated with DNA-DSB number and are considered as efficient and sensitive markers for monitoring the induction and repair of DNA-DSBs. It was established that &#947;-H2AX foci attract repair proteins, leading to a higher concentration of repair factors near a DSB. To monitor DNA damage at the cellular level, immunofluorescence analysis for the presence of DNA-PKcs representative repair protein foci from the NHEJ pathway and Rad52 from the HRR pathway was planned. We have developed and introduced a reliable immunofluorescence staining protocol for the detection of radiation-induced DNA damage response with antibodies specific for repair factors from NHEJ and HRR pathways and observed radiation-induced foci (RIF). The proposed methodology can be used for investigating repair protein that is highly activated in the case of neutron-mixed beam radiation, thereby indicating the dominance of the repair pathway.

Radiation-induced DNA damage response activated by neutron mixed-beam used in boron neutron capture therapy (BNCT) has not been fully established. This protocol provides a step-by-step procedure to detect radiation-induced foci (RIF) of repair proteins by immunofluorescence staining in human colon cancer cell lines after irradiation with the neutron-mixed beam.

The purpose of the manuscript is to provide a step-by-step protocol for performing immunofluorescence microscopy to study the radiation-induced DNA damage ...

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 ...

Modeling Brain Metastasis by Internal Carotid Artery Injection of Cancer Cells

Brain metastasis is a cause of severe morbidity and mortality in cancer patients. Critical aspects of metastatic diseases, such as the complex neural microenvironment and stromal cell interaction, cannot be entirely replicated with in vitro assays; thus, animal models are critical for investigating and understanding the effects of therapeutic intervention. However, most brain tumor xenografting methods do not produce brain metastases consistently in terms of the time frame and tumor burden. Brain metastasis models generated by intracardiac injection of cancer cells can result in unintended extracranial tumor burden and lead to non-brain metastatic morbidity and mortality. Although intracranial injection of cancer cells can limit extracranial tumor formation, it has several caveats, such as the injected cells frequently form a singular tumor mass at the injection site, high leptomeningeal involvement, and damage to brain vasculature during needle penetration. This protocol describes a mouse model of brain metastasis generated by internal carotid artery injection. This method produces intracranial tumors consistently without the involvement of other organs, enabling the evaluation of therapeutic agents for brain metastasis.

Brain metastasis is a cause of severe morbidity and mortality in cancer patients. Most brain metastasis mouse models are complicated by systemic metastases confounding analysis of mortality and therapeutic intervention outcomes. Presented here is a protocol for internal carotid injection of cancer cells that produces consistent intracranial tumors with minimal systemic tumors.

Brain metastasis is a cause of severe morbidity and mortality in cancer patients. Critical aspects of metastatic diseases, such as the complex neural ...

A Flow Cytometry-Based Cell Surface Protein Binding Assay for Assessing Selectivity and Specificity of an Anticancer Aptamer

A key challenge in developing an anticancer aptamer is to efficiently determine the selectivity and specificity of the developed aptamer to the target protein. Due to its several advantages over monoclonal antibodies, aptamer development has gained enormous popularity among cancer researchers. Systematic evolution of ligands by exponential enrichment (SELEX) is the most common method of developing aptamers specific for proteins of interest. Following SELEX, a quick and efficient binding assay accelerates the process of identification, confirming the selectivity and specificity of the aptamer. 
This paper explains a step-by-step flow cytometric-based binding assay of an aptamer specific for epithelial cellular adhesion molecule (EpCAM). The transmembrane glycoprotein EpCAM is overexpressed in most carcinomas and plays roles in cancer initiation, progression, and metastasis. Therefore, it is a valuable candidate for targeted drug delivery to tumors. To evaluate the selectivity and specificity of the aptamer to the membrane-bound EpCAM, EpCAM-positive and -negative cells are required. Additionally, a non-binding EpCAM aptamer with a similar length and 2-dimensional (2D) structure to the EpCAM-binding aptamer is required. The binding assay includes different buffers (blocking buffer, wash buffer, incubation buffer, and FACS buffer) and incubation steps. 
The aptamer is incubated with the cell lines. Following the incubation and washing steps, the cells will be evaluated using a sensitive flow cytometry assay. Analysis of the results shows the binding of the EpCAM-specific aptamer to EpCAM-positive cells and not the EpCAM-negative cells. In EpCAM-positive cells, this is depicted as a band shift in the binding of the EpCAM aptamer to the right compared to the non-binding aptamer control. In EpCAM-negative cells, the corresponding bands of EpCAM-binding and -non-binding aptamers overlap. This demonstrates the selectivity and specificity of the EpCAM aptamer. While this protocol is focused on the EpCAM aptamer, the protocol is applicable to other published aptamers.

A necessary step in anticancer aptamer development is to test its binding to the target. We demonstrate a flow cytometric-based assay to study this binding, emphasizing the importance of including a negative control aptamer and cancer cells that are positive or negative for that particular protein.&#160;

A key challenge in developing an anticancer aptamer is to efficiently determine the selectivity and specificity of the developed aptamer to the target ...

Orthotopic Implantation of Patient-Derived Cancer Cells in Mice Recapitulates Advanced Colorectal Cancer

Over the last decade, more sophisticated preclinical colorectal cancer (CRC) models have been established using patient-derived cancer cells and 3D tumoroids. Since patient derived tumor organoids can retain the characteristics of the original tumor, these reliable preclinical models enable cancer drug screening and the study of drug resistance mechanisms. However, CRC related death in patients is mostly associated with the presence of metastatic disease. It is therefore essential to evaluate the efficacy of anti-cancer therapies in relevant in vivo models that truly recapitulate the key molecular features of human cancer metastasis. We have established an orthotopic model based on the injection of CRC patient-derived cancer cells directly into the cecum wall of mice. These tumor cells develop primary tumors in the cecum that metastasize to the liver and lungs, which is frequently observed in patients with advanced CRC. This CRC mouse model can be used to evaluate drug responses monitored by microcomputed tomography (&#181;CT), a clinically relevant small-scale imaging method that can easily identify primary tumors or metastases in patients. Here, we describe the surgical procedure and the required methodology to implant patient-derived cancer cells in the cecum wall of immunodeficient mice.

This protocol describes the orthotopic implantation of patient-derived cancer cells in the cecum wall of immunodeficient mice. The model recapitulates advanced colorectal cancer metastatic disease and allows for the evaluation of new therapeutic drugs in a clinically relevant scenario of lung and liver metastases.

Over the last decade, more sophisticated preclinical colorectal cancer (CRC) models have been established using patient-derived cancer cells and 3D ...