profiles and generate phenotypically similar KS-like tumors in vivo. Two plausible explanations 11 Productively-Infected KSHV Tumorigenesis Models could account for this outcome: both rKSHV.219 infection and BAC36 transfection were able to establish an infection in, and promote survival of, spindle cell-like progenitor cell isolated from the bone marrow or, KSHV infection induced transdifferentiation of the spindle-like progenitor cell to the same oncogenic endothelial cell lineage. Importantly, both explanations point to the presence of a KS-like spindle cell progenitor among the bone marrow population that was targeted both by BAC36 transfection and rKSHV.219 infection. These results are also consistent with studies showing the oncogenic consequence of KSHV infection of rat bone marrow mesenchymal cells. In summary, we have constructed two productively infected murine models of KS; one from a mouse line established previously 
in our lab and another from primary isolated bone marrow derived cells. By reproducing the tumorigenic phenotype in de novo infected primary marrow-derived murine cells, we have identified a method that sets a foundation for the systematic identification of the KS progenitor cell. Further, our isolation and culture system of primary bone marrow cells and rKSHV.219 infection opens the possibility of delineating KSHV biology and KS pathogenesis with mice genetically engineered to aberrantly express genes important to KS pathophysiology, such as those involved in angiogenesis and inflammation. Finally, these types of productively infected, lytically inducible models should open avenues of research that include in vivo basic science studies of KSHV reactivation and replication and should be excellent systems in which to test novel KSHV-targeted antitumor strategies. growth medium: DMEM supplemented with 30% FBS, 0.2 mg/ml Endothelial Cell Growth Factor , 0.2 mg/ml Endothelial Cell Growth Supplement , 1.2 mg/ml heparin, insulin/transferrin/selenium, 1% penicillin-streptomycin, and BME vitamin. NIH3T3 cells were purchased from American Type Culture Collection. HEK293 cells were cultured in DMEM with 10% FBS and 1% penicillin-streptomycin. All cell lines were PCR tested for: Mycoplasma spp., Sendai virus, mouse hepatitis virus, pneumonia virus of mice, minute virus of mice, mouse parvovirus, Theiler’s murine encephalomyelitis virus, murine norovirus, reovirus 3, mouse rotavirus, ectromelia virus, lymphocytic choriomeningitis virus, polyoma virus, lactate dehydrogenaseelevating virus, mouse adenovirus, mouse cytomegalovirus. Soft agar assay Base agar was made by combining melted 1% agar with 26 mEC medium to give a 0.5% Agar/1X mEC medium solution. 1.5 mL was added to each well of a 6 well plate and allowed to set. Five thousand cells were plated on top of base agar in 0.7% agar/ 2X mEC medium in triplicate in 6-well plates. The cells were fed every 3 days with 1 mL of mEC medium. Colonies were PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19649022 photographed at 4 weeks. Only colonies larger than the mean size of the background colonies in the NIH3T3 negative control wells were considered. Materials and Methods All animal work was conducted according to relevant HC-067047 national and international guidelines and conducted under the University of Miami Miller School of Medicine’s Institutional Animal Care and Use Committee approved protocols in AAALAC certified facilities. Histopathology and immunofluorescence Tissue slices of rKSHV.219 infected mouse tumors were fixed overnight in
