This work was supported by K12 HD068322 (SCM); R01 CA179921 and P51 OD011092 (AVM); and award 14PRE20320014 from the America Heart Association (SB).

NOTE: All procedures described in this protocol should be performed under BSL-2 conditions.
1. KSHV Stock Preparation
<ol>
	<li>Prepare TNE buffer: dissolve 292.24 mg EDTA in ddH2O, bring to 225 mL, and adjust to pH 8. Dissolve 605.7 mg Tris in ddH2O, bring to 225 mL, and adjust to pH 8. Combine EDTA and Tris solutions, add 4.38 g NaCl, adjust final volume to 500 mL, filter sterilize, and store at 4 &#176;C.</li>
	<li>Culture the KSHV-positive, EBV-negative primary effusion lymphoma cell line BCBL-1 in a humidified incubator at 37 &#176;C plus 5% CO2 in RPMI supplemented with 10% heat-inactivated fetal bovine serum (FBS) and antimicrobials to approximately 1 to 1.2 x 106 cells per mL.</li>
	<li>To induce KSHV production, split cultures 1:2 with fresh medium and add Phorbol 12-Myristate 13-Acetate (PMA) to a final concentration of 20 ng/mL and incubate cultures for 5 days. As an alternative, treat cells with sodium butyrate (NaB; 0.1 mM) for 3 days to induce lytic viral replication.</li>
	<li>To harvest viral particles, first centrifuge the culture supernatant at 300 x g for 5 min at room temperature to pellet the cells and transfer supernatants to fresh tubes.</li>
	<li>To further clarify the supernatant so as to avoid transfer of cellular debris, centrifuge at 2,500 x g for 10 min at 4 &#176;C. 
	NOTE: As an alternative to high speed centrifugation for clarification of culture supernatants, filtration through a sterile 0.45 &#181;m filter can be performed. We have observed a significant drop in titer using filtration; therefore, we routinely perform the second centrifugation step instead.</li>
	<li>Next, overlay 5 mL of 25% sucrose solution in TNE buffer with approximately 30 mL of the clarified culture supernatant in 6 ultracentrifuge tubes.</li>
	<li>Centrifuge balanced tubes at 75,000 x g for 2 h at 4 &#176;C under vacuum.</li>
	<li>Decant culture supernatant and blot the rim of each tube to remove as much supernatant and sucrose solution as possible, then resuspend the virus pellet, which may not be visible, in 150 &#181;L of TNE buffer.</li>
	<li>Pool all resuspended virus, mix well, and freeze 25 &#181;L aliquots at -80 &#176;C.</li>
</ol>
2. Transduction of EC with E6 and E7 Papillomavirus Genes
NOTE: We routinely use standard tissue culture flasks for growing primary EC. However, if unsatisfactory growth of EC are obtained then the use of commercial culture flasks should be considered.
<ol>
	<li>Culture primary human dermal microvascular or lymphatic EC in a humidified incubator at 37&#176;C plus 5% CO2 in EC growth medium (EGM; contains EC basal medium [EBM] supplemented with EGM-2 BulletKit [containing FBS, hydrocortisone, human fibroblast growth factor-B, vascular EC growth factor, insulin-like growth factor-1, ascorbic acid, human epithelial growth factor, antibiotics, and heparin]) in a T75 cell culture flask to approximately 50% confluence.</li>
	<li>For transduction, culture PA317 LXSN 16E6E7 cells24,35 in a humidified incubator at 37&#176;C plus 5% CO2 in DMEM supplemented with 10% FBS and antimicrobials in a T150 cell culture flask until they are approximately 90% confluent. Then incubate overnight in 16 mL of medium.</li>
	<li>Clarify the PA317 medium by centrifuging at 300 x g for 5 min at room temperature.</li>
	<li>Remove the EGM from the EC culture and overlay cells with 12 mL of the clarified PA317 medium and incubate for 4 h. 
	NOTE: Centrifuging 16 mL of conditioned medium at 300 x g for 5 min results in a compact pellet that is not disturbed by the careful subsequent removal of 12 mL of clarified supernatant. However, if transfer of PA317 LXSN 16E6E7 cells to primary EC cultures is a concern (the packaging cell line will quickly outgrow EC), then filtration of the conditioned supernatant through a 0.45 &#181;m filter before transfer can be performed.</li>
	<li>Replace 6 mL of the PA317 medium with fresh EGM and incubate overnight.</li>
	<li>Refeed EC with 12 mL fresh EGM and incubate a further 48 h.</li>
	<li>To sub-culture the EC, remove medium and wash with 12 mL of PBS without cations, and add 3 mL of commercial enzymatic dissociation solution (e.g., TrypLE) by and incubate at 37 &#176;C for 3 min.</li>
	<li>Transfer cell suspension to a 15 mL conical tube and centrifuge at 300 x g for 5 min at room temperature. Resuspend the resulting cell pellet in fresh EGM and divide evenly into 3 x T75 flasks with a final volume of 12 mL EGM per flask.</li>
	<li>To select for EC transduced with E6 and E7, add G418 to a final concentration of 200 &#181;g/mL for two passages, after which the transduced EC can be plated for infection or frozen in liquid nitrogen.</li>
</ol>
3. Infection of Transduced EC with KSHV
<ol>
	<li>On the day prior to infection harvest EC by enzymatic digestion using the commercial enzymatic dissociation solution as described above. Resuspend cell pellet in 1 mL of EGM. Use 5 &#181;L of cells to prepare a 1/10 dilution in Trypan blue. Count live cells using a hemocytometer and seed 2.5 x 105 live cells in 2 mL of EGM per well in 6 well plates.</li>
	<li>On the day of infection, remove EGM and wash cells with 3 mL of PBS with calcium and magnesium per well, and then add 2 mL EBM. 
	NOTE: It is essential to use EBM rather than EGM during infection, as the heparin in EGM will inhibit binding of viral particles to and subsequent infection of target EC.</li>
	<li>To infect cells with KSHV, add 5 to 20 &#181;L virus stock to each well and swirl plate to mix. For mock-infected cells add an equal volume of TNE buffer to each well.</li>
	<li>Centrifuge plates at 400 x g for 30 min at room temperature and then incubate the plates at 37 &#176;C for 90 min.</li>
	<li>If the goal of the study is to investigate early events requiring a synchronous viral infection, e.g., early events in de novo infection, remove the viral inoculum at this point. Rinse and refeed the cells with 2 mL fresh EGM. Otherwise, add 2 mL EGM and incubate cultures overnight.</li>
	<li>Refeed cells with 2 mL EGM the day after infection and then every other day.</li>
	<li>When cells are approximately 90% confluent, harvest by enzymatic digestion using commercial enzymatic dissociation solution as described above, then pool the cells from three wells into a T75, noting both the total passage number and the passage post-infection.</li>
	<li>Expand mock- and KSHV-infected EC with 1:3 splits for at least two more passages at which time cells can be used in experiments or frozen in liquid nitrogen. 
	NOTE: As with splitting of EC transduced with E6 and E7, maintenance cultures of mock- and KSHV-infected cells should be split before reaching confluence (~85 to 90%).</li>
</ol>
4. Confirming Infection with KSHV by Immunofluorescence
NOTE: Detection of the KSHV latency-associated nuclear antigen (LANA-1/ORF73) provides a reliable quantitative measure of infection. Anti-LANA antibodies are commercially available.
<ol>
	<li>The day prior to staining, plate two wells each with mock- or KSHV-infected EC on a 24-well plate at 1 x 105 cells per well in 1 mL EGM and incubate overnight.</li>
	<li>Wash cells twice with 500 &#181;L of PBS plus calcium and magniseum. Wash for 30 s on a rocking platform.</li>
	<li>In an externally-ventillated fume hood, fix cells with 500 &#181;L of 4% paraformaldehyde for 15 min at room temperature.</li>
	<li>Wash cells three times with 500 &#181;L of wash buffer (0.1% Triton X-100 plus 0.02% goat serum in PBS plus cations).</li>
	<li>Block cells with 500 &#181;L of 2% goat serum in wash buffer for 30 min at room temperature.</li>
	<li>Wash cells three times with 500 &#181;L of wash buffer.</li>
	<li>Label one well of mock- or KSHV-infected EC with 200 &#181;L of primary antibody diluted 1:100 in wash buffer for 30 min at room temperature on a rocker. Incubate the remaining two wells in 200 &#181;L of wash buffer only.</li>
	<li>Wash cells three times with 500 &#181;L of wash buffer.</li>
	<li>Label all four wells with 200 &#181;L of secondary antibody diluted 1:100 in wash buffer for 30 min at room temperature on a rocker.</li>
	<li>Wash cells three times with 500 &#181;L of wash buffer.</li>
	<li>To each well apply 20 &#181;L of mounting medium containing DAPI and a coverslip and evaluate staining using an inverted fluorescent microscope.</li>
	<li>Determine the percent infection of KSHV-infected cells by counting the number of LANA-positive nuclei in at least 200 cells. Infection with recombinant KSHV-Bac16 can also be monitored via observation of cultures for expression of GFP.</li>
</ol>

Oncogenesis is a multistep process that circumvents important safeguards within an organism36. As KS lesions exist along a spectrum of chronic inflammation to true sarcomas, elucidation of certain pathophysiological processes mediated by KSHV requires that some studies be conducted in cell culture models that support transformation9. It should be noted that loss of contact inhibition and anchorage-dependent growth, phenotypes indicative of cellular transformation, do not re...

Kaposi sarcoma (KS) is a multi-focal angioproliferative tumor affecting dermal, mucosal, and visceral sites that develops most commonly in the setting of advanced immune suppression1. Four epidemiological forms have been described: classic, an indolent form that typically affects older people of Mediterranean and Middle Eastern heritage; iatrogenic, resulting from treatment with immunosuppressive drugs following organ transplantation; epidemic, an AIDS-defining cancer; and endemic, an HIV-independent form common in children in endemic regions in Africa. With the advent of effective combination anti-retroviral drug regimens for the treatment of HIV, epidemic KS is much less commonly diagnosed in developing countries. However, the clinically aggressive endemic and epidemic forms remain among the most commonly diagnosed cancers in many African countries2,3,4. Therefore, identification of effective pathogenesis-targeted drugs for treatment of KS is a research priority.
Histologically, KS lesions are characterized by extensive but abnormal neovascularization whereby spindle cells of EC origin form discontinuous vascular networks5. These abnormal vessels (&#34;vascular slits&#34;) allow extravasation of erythrocytes, which give lesions their characteristic color. Additionally, lesions contain numerous leukocytes that characterize chronic inflammation (i.e., lymphocytes, macrophages, and plasma cells). Regression of KS lesions following immune reconstitution has been described, suggesting that KS has features of both a hyper-proliferative lesion and a true tumor6,7,8,9.
KS herpesvirus (KSHV), the causative agent of KS, was identified in 199410. Since then many in vitro cell culture models have been developed to enable pathogenesis studies, including cells explanted from tumor biopsy material and primary or telomerase-expressing EC infected with KSHV in vitro11,12,13,14,15,16,17,18. None of the currently available models fully recapitulates the KS tumor microenvironment, but all have contributed valuable knowledge to our understanding of the pathobiology of KSHV infection. Unlike the other known tumorigenic human herpesvirus Epstein-Barr virus (EBV), KSHV does not readily transform cells in culture following de novo infection19,20,21,22. However, this limitation has been overcome by transducing primary human EC of either mixed microvascular or lymphatic origin with the E6 and E7 genes from human papillomavirus type 16 prior to infection with KSHV23,24. Expression of these exogenous oncogenes dramatically increases the transforming potential of KSHV in vitro in part by providing further inhibition of the retinoblastoma protein and p5323,24. This EC transduction method has allowed multiple laboratories to identify key alterations in host cell gene expression that are induced by KSHV infection and that appear to facilitate KS cell survival and proliferation25,26,27,28,29,30,31,32. The protocols described herein are straightforward and highly reproducible, and will result in the generation of age- and passage-matched KSHV-infected EC and mock-infected controls that can be cultured for far longer than primary cells and will allow for the investigation of oncogenic mechanisms employed by KSHV. Although the protocol includes a method for production of wild type KSHV from the primary effusion lymphoma cell line BCBL-1, E6/E7-immortalized EC are also highly susceptible to infection with recombinant BACmid derived KSHV-BAC1630. Protocols for preparation of BAC16 are described elsewhere33,34.

<table><tbody><tr><td>BCBL-1 cells</td><td>NIH AIDS Reagent Program</td><td>3233</td><td></td></tr><tr><td>PA317 cells</td><td>ATCC</td><td>CRL-2203</td><td></td></tr><tr><td>Neonatal dermal microvascular endothelial cells</td><td>Lonza</td><td>CC-2505</td><td></td></tr><tr><td>EBM-2 Basal Medium</td><td>Lonza</td><td>CC-3156</td><td></td></tr><tr><td>EGM-2 BulletKit</td><td>Lonza</td><td>CC-3162</td><td></td></tr><tr><td>anti-KSHV LANA/ORF 73</td><td>Advanced Biotechnologies</td><td>13-210-100</td><td></td></tr><tr><td>TrypLE&lt;sup&gt;TM&lt;/sup&gt;Express, no phenol red</td><td>ThermoFisher</td><td>12604013</td><td></td></tr><tr><td>RPMI</td><td></td><td></td><td></td></tr><tr><td>DMEM</td><td></td><td></td><td></td></tr><tr><td>PBS with calcium and magnesium</td><td></td><td></td><td></td></tr></tbody></table>

an in vitro model for studying cellular transformation by kaposi sarcoma herpesvirus

Kaposi sarcoma (KS) is an unusual tumor composed of proliferating spindle cells that is initiated by infection of endothelial cells (EC) with KSHV, and develops most often in the setting of immunosuppression. Despite decades of research, optimal treatment of KS remains poorly defined and clinical outcomes are especially unfavorable in resource-limited settings. KS lesions are driven by pathological angiogenesis, chronic inflammation, and oncogenesis, and various in vitro cell culture models have been developed to study these processes. KS arises from KSHV-infected cells of endothelial origin, so EC-lineage cells provide the most appropriate in vitro surrogates of the spindle cell precursor. However, because EC have a limited in vitro lifespan, and as the oncogenic mechanisms employed by KSHV are less efficient than those of other tumorigenic viruses, it has been difficult to assess the processes of transformation in primary or telomerase-immortalized EC. Therefore, a novel EC-based culture model was developed that readily supports transformation following infection with KSHV. Ectopic expression of the E6 and E7 genes of human papillomavirus type 16 allows for extended culture of age- and passage-matched mock- and KSHV-infected EC and supports the development of a truly transformed (i.e., tumorigenic) phenotype in infected cell cultures. This tractable and highly reproducible model of KS has facilitated the discovery of several essential signaling pathways with high potential for translation into clinical settings.

The morphology of primary EC is classically described as &#34;cobble stone&#34;, and this morphology is not altered by expression of the papillomavirus E6 and E7 genes (Figure 1A). Expression of the E6 and E7 genes alone does not induce a transformed phenotype; thus, cells are susceptible to contact inhibition and will cease dividing upon reaching confluence in culture. The cells will however proliferate and regrow to confluence upon trypsinization and replating at a lowe...

Watch this Scientific Journal Video about An In Vitro Model for Studying Cellular Transformation by Kaposi Sarcoma Herpesvirus at JoVE.com

An In Vitro Model for Studying Cellular Transformation by Kaposi Sarcoma Herpesvirus

Kaposi sarcoma (KS) is a tumor induced by infection with the oncogenic virus human herpesvirus-8/KS herpesvirus (HHV-8/KSHV). The endothelial cell culture model described here is uniquely suited for studying the mechanisms by which KSHV transforms host cells.

An In Vitro Model for Studying Cellular Transformation by Kaposi Sarcoma Herpesvirus

Kaposi sarcoma (KS) is an unusual tumor composed of proliferating spindle cells that is initiated by infection of endothelial cells (EC) with KSHV, and ...

an-vitro-model-for-studying-cellular-transformation-kaposi-sarcoma

Research

JoVE Journal

Biology

8.2K Views.  University of Minnesota Medical School. Kaposi sarcoom (KS) is een tumor die is veroorzaakt door infectie met de oncogene virus Humaan herpesvirus-8/KS herpesvirus (HHV-8/KSHV). De endothelial cell cultuur model hier beschreven is uniek geschikt voor de studie van de mechanismen waarmee KSHV gastheer cellen transformeert.

Video: An In Vitro Model for Studying Cellular Transformation by Kaposi Sarcoma Herpesvirus

Identifying Dysregulated Genes Induced by Kaposi's Sarcoma-associated Herpesvirus (KSHV)

Currently KS is the most predominant HIV/AIDS related malignancy in Southern Africa and hence the world.1,2 It is characterized as an angioproliferative tumor of vascular endothelial cells and produces rare B cell lymphoproliferative diseases in the form of pleural effusion lymphomas (PEL) and some forms of multicentric Castleman's disease.3-5 Only 1-5% of cells in KS lesions actively support lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent associated with KS, and it is clear that cellular factors must interact with viral factors in the process of oncogenesis and tumor progression.6,7 Identifying novel host-factor determinants which contribute to KS pathology is essential for developing prognostic markers for tumor progression and metastasis as well as for developing novel therapeutics for the treatment of KS.8 The accompanying video details the methods we use to identify host cell gene expression programs altered in dermal microvascular endothelial cells (DMVEC) after KSHV infection and in KS tumor tissue.9 Once dysregulated genes are identified by microarray analysis, changes in protein expression are confirmed by immunoblot and dual labeled immunofluorescence. Changes in transcriptional expression of dysregulated genes are confirmed in vitro by quantitative real-time polymerase chain reaction (qRT-PCR). Validation of in vitro findings using archival KS tumor tissue is also performed by dual labeled immunochemistry and tissue microarrays.8,10 Our approach to identifying dysregulated genes in the KS tumor tissue microenvironment will allow the development of in vitro and subsequently in vivo model systems for discovery and evaluation of potential novel therapeutic for the treatment of KS.

Identifying Dysregulated Genes Induced by Kaposi's Sarcoma-associated Herpesvirus KSHV

Host cell factors play a critical role in the establishment and maintenance of Kaposi's sarcoma (KS). We outline methods to identify host cell factors altered in KSHV-infected DMVEC cells, and in KS tumor tissue. Cellular genes altered by virus will serve as potential target(s) for novel therapeutics.

Currently KS is the most predominant HIV/AIDS related malignancy in Southern Africa and hence the world.1,2 It is characterized as an angioproliferative ...

Immunology and Infection

Dissecting Host-virus Interaction in Lytic Replication of a Model Herpesvirus

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral cytokine production1,2. In order to colonize the host, viruses are obligate to evade host antiviral responses and manipulate signaling pathways. Unraveling the host-virus interaction will shed light on the development of novel therapeutic strategies against viral infection.
Murine &gamma;HV68 is closely related to human oncogenic Kaposi's sarcoma-associated herpesvirus and Epsten-Barr virus3,4. &gamma;HV68 infection in laboratory mice provides a tractable small animal model to examine the entire course of host responses and viral infection in vivo, which are not available for human herpesviruses. In this protocol, we present a panel of methods for phenotypic characterization and molecular dissection of host signaling components in &gamma;HV68 lytic replication both in vivo and ex vivo. The availability of genetically modified mouse strains permits the interrogation of the roles of host signaling pathways during &gamma;HV68 acute infection in vivo. Additionally, mouse embryonic fibroblasts (MEFs) isolated from these deficient mouse strains can be used to further dissect roles of these molecules during &gamma;HV68 lytic replication ex vivo.
Using virological and molecular biology assays, we can pinpoint the molecular mechanism of host-virus interactions and identify host and viral genes essential for viral lytic replication. Finally, a bacterial artificial chromosome (BAC) system facilitates the introduction of mutations into the viral factor(s) that specifically interrupt the host-virus interaction. Recombinant &gamma;HV68 carrying these mutations can be used to recapitulate the phenotypes of &gamma;HV68 lytic replication in MEFs deficient in key host signaling components. This protocol offers an excellent strategy to interrogate host-pathogen interaction at multiple levels of intervention in vivo and ex vivo.
Recently, we have discovered that &gamma;HV68 usurps an innate immune signaling pathway to promote viral lytic replication5. Specifically, &gamma;HV68 de novo infection activates the immune kinase IKK&beta; and activated IKK&beta; phosphorylates the master viral transcription factor, replication and transactivator (RTA), to promote viral transcriptional activation. In doing so, &gamma;HV68 efficiently couples its transcriptional activation to host innate immune activation, thereby facilitating viral transcription and lytic replication. This study provides an excellent example that can be applied to other viruses to interrogate host-virus interaction.

We describe a protocol to identify key roles of host signaling molecules in lytic replication of a model herpesvirus, gamma herpesvirus 68 (&gamma;HV68). Utilizing genetically modified mouse strains and embryonic fibroblasts for &gamma;HV68 lytic replication, the protocol permits both phenotypic characterization and molecular interrogation of virus-host interactions in viral lytic replication.

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral ...

Production of Replication-Defective Retrovirus by Transient Transfection of 293T cells

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, Bcr-PDGFR&#945;, etc.). We are able to model and study a human-like disease in our mouse model, by transplanting bone marrow cells previously infected with a retrovirus expressing the oncogene of interest. Replication-defective retrovirus encoding a human oncogene and a marker (GFP, RFP, antibiotic resistance gene, etc.) is produced by a transient transfection protocol using 293T cells, a human renal epithelial cell line transformed by the adenovirus E1A gene product. 293 cells have the unusual property of being highly transfectable by calcium phosphate (CaPO4), with up to 50-80% transfection efficiency readily attainable. Here, we co-transfect 293 cells with a retroviral vector expressing the oncogene of interest and a plasmid that expresses the gag-pol-env packaging functions, such as the single-genome packaging constructs kat or pCL, in this case the EcoPak plasmid. The initial transfection is further improved by use of chloroquine. Stocks of ecotropic virus, collected as culture supernatant 48 hrs. post-transfection, can be stored at -80&deg;C and used for infection of cell-lines in view of transformation and in vitro studies, or primary cells such as mouse bone marrow cells, that can then be used for transplant in our mouse model.

This technique demonstrates an efficient way to prepare replication-defective retroviral stocks encoding a human oncogene, and subsequently used for induction of myeloproliferative disease in the mouse model.

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, ...

Ex Vivo Organotypic Corneal Model of Acute Epithelial Herpes Simplex Virus Type I Infection

Herpes keratitis is one of the most severe pathologies associated with the herpes simplex virus-type 1 (HSV-1). Herpes keratitis is currently the leading cause of both cornea-derived and infection-associated blindness in the developed world. Typical presentation of herpes keratitis includes infection of the corneal epithelium and sometimes the deeper corneal stroma and endothelium, leading to such permanent corneal pathologies as scarring, thinning, and opacity 1.
Corneal HSV-1 infection is traditionally studied in two types of experimental models. The in vitro model, in which cultured monolayers of corneal epithelial cells are infected in a Petri dish, offers simplicity, high level of replicability, fast experiments, and relatively low costs. On the other hand, the in vivo model, in which animals such as rabbits or mice are inoculated directly in the cornea, offers a highly sophisticated physiological system, but has higher costs, longer experiments, necessary animal care, and a greater degree of variability. 
In this video article, we provide a detailed demonstration of a new ex vivo model of corneal epithelial HSV-1 infection, which combines the strengths of both the in vitro and the in vivo models. The ex vivo model utilizes intact corneas organotypically maintained in culture and infected with HSV-1. The use of the ex vivo model allows for highly physiologically-based conclusions, yet it is rather inexpensive and requires time commitment comparable to that of the in vitro model.

Ex Vivo Organotypic Corneal Model of Acute Epithelial Herpes Simplex Virus Type I Infection

In this video article we describe the use of a new ex vivo model of acute herpes simplex virus type I corneal epithelial infection.

Herpes keratitis is one of the most severe pathologies associated with the herpes simplex virus-type 1 (HSV-1).  Herpes keratitis is currently the leading ...

Neuroscience

In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells

Tumorigenesis is a multi-step process in which cells acquire capabilities&#160;that allow their growth, survival, and dissemination under hostile conditions. Different tests seek to identify and quantify these hallmarks of cancerous cells; however, they often focus on a single aspect of cellular transformation and, in fact, multiple tests are required for their proper characterization. The purpose of this work is to provide researchers with a set of tools to assess cellular transformation in vitro from a broad perspective, thereby making it possible to draw sound conclusions.
A sustained proliferative signaling activation is the major feature of tumoral tissues and can be easily monitored under in vitro conditions by calculating the number of population doublings achieved over time. Besides, the growth of cells in 3D cultures allows their interaction with surrounding cells, resembling what occurs in vivo. This enables the evaluation of cellular aggregation and, together with immunofluorescent labeling of distinctive cellular markers, to obtain information on another relevant feature of tumoral transformation: the loss of proper organization. Another remarkable characteristic of transformed cells is their capacity to grow without attachment to other cells and to the extracellular matrix, which can be evaluated with the anchorage assay.
Detailed experimental procedures to evaluate cell growth rate, to perform immunofluorescent labeling of cell lineage markers in 3D cultures, and to test anchorage-independent cell growth in soft agar are provided. These methodologies are optimized for Breast Primary Epithelial Cells (BPEC) due to its relevance in breast cancer; however, procedures can be applied to other cell types after some adjustments.

This protocol provides experimental in vitro tools to evaluate the transformation of human mammary cells. Detailed steps to follow-up cell proliferation rate, anchorage-independent growth capacity, and distribution of cell lineages in 3D cultures with basement membrane matrix are described.

Tumorigenesis is a multi-step process in which cells acquire capabilities&#160;that allow their growth, survival, and dissemination under hostile ...

Cancer Research

Ex Vivo Infection of Murine Epidermis with Herpes Simplex Virus Type 1

To enter its human host, herpes simplex virus type 1 (HSV-1) must overcome the barrier of mucosal surfaces, skin, or cornea. HSV-1 targets keratinocytes during initial entry and establishes a primary infection in the epithelium, which is followed by latent infection of neurons. After reactivation, viruses can become evident at mucocutaneous sites that appear as skin vesicles or mucosal ulcers. How HSV-1 invades skin or mucosa and reaches its receptors is poorly understood. To investigate the invasion route of HSV-1 into epidermal tissue at the cellular level, we established an ex vivo infection model of murine epidermis, which represents the site of primary and recurrent infection in skin. The assay includes the preparation of murine skin. The epidermis is separated from the dermis by dispase II treatment. After floating the epidermal sheets on virus-containing medium, the tissue is fixed and infection can be visualized at various times postinfection by staining infected cells with an antibody against the HSV-1 immediate early protein ICP0. ICP0-expressing cells can be observed in the basal keratinocyte layer already at 1.5 hr postinfection. With longer infection times, infected cells are detected in suprabasal layers, indicating that infection is not restricted to the basal keratinocytes, but the virus spreads to other layers in the tissue. Using epidermal sheets of various mouse models, the infection protocol allows determining the involvement of cellular components that contribute to HSV-1 invasion into tissue. In addition, the assay is suitable to test inhibitors in tissue that interfere with the initial entry steps, cell-to-cell spread and virus production. Here, we describe the ex vivo infection protocol in detail and present our results using nectin-1- or HVEM-deficient mice.

Ex Vivo Infection of Murine Epidermis with Herpes Simplex Virus Type 1

The skin is one target tissue of the human pathogen herpes simplex virus type 1 (HSV-1). To explore the invasion route of HSV-1 into tissue, we established an ex vivo infection model of murine epidermal sheets which represent the outermost layer of skin.

To enter its human host, herpes simplex virus type 1 (HSV-1) must overcome the barrier of mucosal surfaces, skin, or cornea. HSV-1 targets keratinocytes ...

Modeling Astrocytoma Pathogenesis In Vitro and In Vivo Using Cortical Astrocytes or Neural Stem Cells from Conditional, Genetically Engineered Mice

Current astrocytoma models are limited in their ability to define the roles of oncogenic mutations in specific brain cell types during disease pathogenesis and their utility for preclinical drug development. In order to design a better model system for these applications, phenotypically wild-type cortical astrocytes and neural stem cells (NSC) from conditional, genetically engineered mice (GEM) that harbor various combinations of floxed oncogenic alleles were harvested and grown in culture. Genetic recombination was induced in vitro using adenoviral Cre-mediated recombination, resulting in expression of mutated oncogenes and deletion of tumor suppressor genes. The phenotypic consequences of these mutations were defined by measuring proliferation, transformation, and drug response in vitro. Orthotopic allograft models, whereby transformed cells are stereotactically injected into the brains of immune-competent, syngeneic littermates, were developed to define the role of oncogenic mutations and cell type on tumorigenesis in vivo. Unlike most established human glioblastoma cell line xenografts, injection of transformed GEM-derived cortical astrocytes into the brains of immune-competent littermates produced astrocytomas, including the most aggressive subtype, glioblastoma, that recapitulated the histopathological hallmarks of human astrocytomas, including diffuse invasion of normal brain parenchyma. Bioluminescence imaging of orthotopic allografts from transformed astrocytes engineered to express luciferase was utilized to monitor in vivo tumor growth over time. Thus, astrocytoma models using astrocytes and NSC harvested from GEM with conditional oncogenic alleles provide an integrated system to study the genetics and cell biology of astrocytoma pathogenesis in vitro and in vivo and may be useful in preclinical drug development for these devastating diseases.

Modeling Astrocytoma Pathogenesis In Vitro and In Vivo Using Cortical Astrocytes or Neural Stem Cells from Conditional, Genetically Engineered Mice

Phenotypically wild-type astrocytes and neural stem cells harvested from mice engineered with floxed, conditional oncogenic alleles and transformed via viral Cre-mediated recombination can be used to model astrocytoma pathogenesis in vitro and in vivo by orthotopic injection of transformed cells into brains of syngeneic, immune-competent littermates.

Current astrocytoma models are limited in their ability to define the roles of oncogenic mutations in specific brain cell types during disease ...

Quantitative Fluorescence In Situ Hybridization (FISH) and Immunofluorescence (IF) of Specific Gene Products in KSHV-Infected Cells

Mechanistic insight arrives from careful study and quantification of specific RNAs and proteins. The relative locations of these biomolecules throughout the cell at specific times can be captured with fluorescence in situ hybridization (FISH) and immunofluorescence (IF). During lytic herpesvirus infection, the virus hijacks the host cell to preferentially express viral genes, causing changes in cell morphology and behavior of biomolecules. Lytic activities are centered in nuclear factories, termed viral replication compartments, which are discernable only with FISH and IF. Here we describe an adaptable protocol of RNA FISH and IF techniques for Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells, both adherent and in suspension. The method includes steps for the development of specific anti-sense oligonucleotides, double RNA FISH, RNA FISH with IF, and quantitative calculations of fluorescence intensities. This protocol has been successfully applied to multiple cell types, uninfected cells, latent cells, lytic cells, time-courses, and cells treated with inhibitors to analyze the spatiotemporal activities of specific RNAs and proteins from both the human host and KSHV.

Quantitative Fluorescence In Situ Hybridization FISH and Immunofluorescence IF of Specific Gene Products in KSHV-Infected Cells

We describe a protocol utilizing fluorescence in situ hybridization (FISH) to visualize multiple herpesviral RNAs within lytically infected human cells, either in suspension or adherent. This protocol includes quantification of fluorescence producing a nucleocytoplasmic ratio and can be extended for simultaneous visualization of host and viral proteins with immunofluorescence (IF).

Mechanistic insight arrives from careful study and quantification of specific RNAs and proteins. The relative locations of these biomolecules throughout ...

Monitoring Plasmid Replication in Live Mammalian Cells over Multiple Generations by Fluorescence Microscopy

Few naturally-occurring plasmids are maintained in mammalian cells. Among these are genomes of gamma-herpesviruses, including Epstein-Barr virus (EBV) and Kaposi's Sarcoma-associated herpesvirus (KSHV), which cause multiple human malignancies 1-3. These two genomes are replicated in a licensed manner, each using a single viral protein and cellular replication machinery, and are passed to daughter cells during cell division despite their lacking traditional centromeres 4-8.
Much work has been done to characterize the replications of these plasmid genomes using methods such as Southern blotting and fluorescence in situ hybridization (FISH). These methods are limited, though. Quantitative PCR and Southern blots provide information about the average number of plasmids per cell in a population of cells. FISH is a single-cell assay that reveals both the average number and the distribution of plasmids per cell in the population of cells but is static, allowing no information about the parent or progeny of the examined cell.
Here, we describe a method for visualizing plasmids in live cells. This method is based on the binding of a fluorescently tagged lactose repressor protein to multiple sites in the plasmid of interest 9. The DNA of interest is engineered to include approximately 250 tandem repeats of the lactose operator (LacO) sequence. LacO is specifically bound by the lactose repressor protein (LacI), which can be fused to a fluorescent protein. The fusion protein can either be expressed from the engineered plasmid or introduced by a retroviral vector. In this way, the DNA molecules are fluorescently tagged and therefore become visible via fluorescence microscopy. The fusion protein is blocked from binding the plasmid DNA by culturing cells in the presence of IPTG until the plasmids are ready to be viewed.
This system allows the plasmids to be monitored in living cells through several generations, revealing properties of their synthesis and partitioning to daughter cells. Ideal cells are adherent, easily transfected, and have large nuclei. This technique has been used to determine that 84% of EBV-derived plasmids are synthesized each generation and 88% of the newly synthesized plasmids partition faithfully to daughter cells in HeLa cells. Pairs of these EBV plasmids were seen to be tethered to or associated with sister chromatids after their synthesis in S-phase until they were seen to separate as the sister chromatids separated in Anaphase10. The method is currently being used to study replication of KSHV genomes in HeLa cells and SLK cells. HeLa cells are immortalized human epithelial cells, and SLK cells are immortalized human endothelial cells. Though SLK cells were originally derived from a KSHV lesion, neither the HeLa nor SLK cell line naturally harbors KSHV genomes11. In addition to studying viral replication, this visualization technique can be used to investigate the effects of the addition, removal, or mutation of various DNA sequence elements on synthesis, localization, and partitioning of other recombinant plasmid DNAs.

A method of observing individual DNA molecules in live cells is described. The technique is based on the binding of a fluorescently tagged lac repressor protein to binding sites engineered into the DNA of interest. This method can be adapted to follow many recombinant DNAs in live cells over time.

Few naturally-occurring plasmids are maintained in mammalian cells.  Among these are genomes of gamma-herpesviruses, including Epstein-Barr virus  (EBV) ...

Dual Bioluminescence Imaging of Tumor Progression and Angiogenesis

Angiogenesis, as a crucial process of tumor progression, has become a research hotspot and target of anti-tumor therapy. However, there is no reliable model for tracing tumor progression and angiogenesis simultaneously in a visual and sensitive manner. Bioluminescence imaging displays its unique superiority in living imaging due to its advantages of high sensitivity, strong specificity, and accurate measurement. Presented here is a protocol to establish a tumor-bearing mouse model by injecting a Renilla luciferase-labeled murine breast cancer cell line 4T1 into the transgenic mouse with angiogenesis-induced Firefly luciferase expression. This mouse model provides a valuable tool to simultaneously monitor tumor progression and angiogenesis in real-time by dual bioluminescence imaging in a single mouse. This model may be widely applied in anti-tumor drug screening and oncology research.

This protocol describes the establishment of a tumor-bearing mouse model to monitor tumor progression and angiogenesis in real-time by dual bioluminescence imaging.

Angiogenesis, as a crucial process of tumor progression, has become a research hotspot and target of anti-tumor therapy. However, there is no reliable ...

An In Vitro Model for Studying Cellular Transformation by Kaposi Sarcoma Herpesvirus

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