Immunomodulatory drugs reactivate lytic EBV.

Purpose:Lenalidomide, thalidomide, and pomalidomide (LTP) are immunomodulatory agents approved for use in multiple myeloma, but in some settings, especially with alkylating agents, an increase in Hodgkin's lymphoma (HL) and other secondary primary malignancies (SPM) has been noted. Some of these malignancies have been linked to Epstein-Barr virus (EBV), raising the possibility that immunomodulatory drugs disrupt latent EBV infection. Experimental Design:We studied the ability of LTP to reactivate latently infected EBV-positive cell lines in vitro and in vivo, and evaluated the EBV viral load in archived serum samples from patients who received a lenalidomide, thalidomide and dexamethasone (LTD) combination. Results:Treatment of EBV-infected B-cell lines with LTP at physiologically relevant concentrations induced the immediate early gene BZLF1, the early gene BMRF1, and the late proteins VCA and BCFR1. This occurred in the potency order pomalidomide>lenalidomide>thalidomide, and the nucleoside analogue ganciclovir enhanced the cytotoxic effects of lenalidomide and pomalidomide in Burkitt's lymphoma cells in vitro and in vivo. EBV reactivation was related to phosphatidylinositol-3 kinase (PI3K) stimulation and Ikaros suppression, and blocked by the PI3K- inhibitor idelalisib. Combinations of lenalidomide with dexamethasone or rituximab increased EBV reactivation compared to lenalidomide alone and, importantly, lenalidomide with melphalan produced even greater reactivation Conclusions:We conclude LTP may reactivate EBV-positive resting memory B-cells thereby enhancing EBV lytic cycle and host immune suppression.

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