Furthermore, K9/vIRF1 mRNA is expressed in all KS tumors (total 21 KS clinical biopsies) and preferentially transcribed during latent infection of either endothelial/mesenchymal lineage cells, which strengthens the role of K9/vIRF1 in KS tumorigenesis [58]. This evidence concerns the gene KRT9 and disease arising from reactivation of latent virus.