Kaposi's sarcoma (KS) is common in Africa, but economic constraints hinder successful treatment in most patients. Propranolol, a generic -adrenergic antagonist, decreased proliferation of KS-associated herpesvirus (KSHV)-infected cells. Downregulation of cyclin A2 and cyclin-dependent kinase 1 (CDK1) recapitulated this phenotype. Additionally, propranolol induced lytic gene expression in association with downregulation of CDK6. Thus, propranolol has diverse effects on KSHV-infected cells, and this generic drug has potential as a therapeutic agent for KS.
Kaposi's sarcoma (KS) is a vascular neoplasm initiated by infection of endothelial cells (EC) with KS-associated herpesvirus (KSHV) (1). Infection induces a transformed phenotype typified by anchorage-independent growth, loss of contact inhibition, and upregulation of progrowth pathways. Targeting these altered processes in vitro has identified novel treatment targets (2-5). However, economic constraints prevent clinical translation of many of these observations in areas of high KS burden, so systemic cytotoxic agents, where available, remain the mainstay of KS treatment (6, 7).Like KS, the vascular lesion infantile hemangioma (IH) develops from dysregulated proliferation of EC (8). The generic -adrenergic antagonist propranolol has been shown recently to be effective against IH and is now a first-line agent for treatment of this vascular lesion (9, 10). Given the similarities between KS and IH, we hypothesized that propranolol would decrease proliferation of KSHV-infected EC in a validated in vitro KS model (11). Here we show that postconfluent growth of EC transformed by KSHV requires cyclin-dependent kinase 1 (CDK1) and one of its binding partners, cyclin A2, to complete the S and G 2 -M phases of the cell cycle. Furthermore, we show that induction of KSHV lytic gene expression is associated with downregulation of CDK6. These data suggest that -adrenergic signaling drives KS cell proliferation and suppresses viral reactivation in part by maintaining high levels of cyclin A2 and CDK6, respectively. Additionally, these data identify propranolol as a potential agent for treatment of KS amenable to use in limited-resource settings.Propranolol decreased postconfluent proliferation of KSHV-infected EC. Human lymphatic EC were maintained in endothelial growth medium 2 (EGM-2; Lonza, Allendale, NJ). Transduction of EC with the human papillomavirus E6 and E7