We found that Hsp90 inhibitors significantly decreased the expression of Ephrin-B2 in multiple KS tumor models (L1T2, SLK-KSHV), which suggests that downregulation of ephrin interactions through Hsp90 inhibitors contributes to their effectiveness in the endothelial lineage tumor KS. The gene discussed is EFNB2; the disease is Kaposi's sarcoma.