RNA-sequencing (RNA-seq) analysis of KSHV gene expression in tumors derived from KSHV-infected PDGFRA-positive MSCs grown in KS-like media (K-Pα(+)S KS tumors), which were found to be histologically indistinguishable from mECK36, also showed upregulation of KSHV lytic gene expression compared to the tumorigenic cells grown in vitro (KSHV in vivo lytic switch) (Fig 2A). This evidence concerns the gene PDGFRA and Kaposi's sarcoma.