Apoptotic effect of ganciclovir on primary effusion lymphoma cells infected with Kaposi's sarcoma-associated herpesvirus

Primary effusion lymphoma in an elderly patient effectively treated by lenalidomide: case report and review of literature

Primary effusion lymphoma (PEL) is a rare aggressive subset of non-Hodgkin B-cell lymphoma. It is caused by Kaposi sarcoma-associated herpesvirus/human herpesvirus type 8 (KSHV/HHV8). It occurs mainly, but not exclusively, in HIV-positive patients. PEL predominantly develops in serous cavities and occasionally in extracavitary regions. PEL carries a very poor prognosis with a median survival time of <6 months. Indeed, currently used treatment modalities such as CHOP chemotherapy are far from achieving complete and sustainable remission. Therefore, there is no clear standard of care established in the treatment of PEL patients, stressing the need for novel-targeted approaches. Here, we have attempted a comprehensive assessment of the treatment of PEL, discussed avant-garde therapies and updated the state of preclinical research with promising clinical applications in the field. These include inhibitors of viral replication, modulators of cell signaling and inflammation, nuclear factor kappa B (NF-κB) and histone deacetylase inhibitors, and recently the combination of arsenic trioxide and interferon-alpha. Some of these targeted therapies have not yet reached clinical studies, although others were used in a few individual case reports with low numbers of patients. We also describe the first case of a 77-year-old, HIV-negative, HHV8-positive patient diagnosed with PEL limited to the pleural and peritoneal cavities. He received lenalidomide 25 mg/day for 21 days every 28 days. Treatment was well tolerated with no side effects. He rapidly improved after 1 month of treatment and progressively achieved complete remission persistent after 18 months of therapy. We believe that this review will bridge an important gap between classical chemotherapy and modern approaches of targeted therapy. Finally, our findings warrant further evaluation of lenalidomide in future prospective clinical studies.

Proteasome inhibitors induce apoptosis and reduce viral replication in primary effusion lymphoma cells

Primary effusion lymphoma (PEL) is an aggressive neoplasm caused by Kaposi's sarcoma-associated herpesvirus (KSHV). This study provides evidence that proteasomal activity is required for both survival of PEL cells stably harboring the KSHV genome and viral replication of KSHV. We evaluated the cytotoxic effects of proteasome inhibitors on PEL cells. The proteasome inhibitors MG132, lactacystin, and proteasome inhibitor I dramatically inhibited cell proliferation and induced apoptosis of PEL cells through the accumulation of p21 and p27. Furthermore, proteasome inhibitors induced the stabilization of NF-κB inhibitory molecule (IκBα) and suppressed the transcriptional activity of NF-κB in PEL cells. The NF-κB specific inhibitor BAY11-7082 also induced apoptosis in PEL cells. The constitutive activation of NF-κB signaling is essential for the survival and growth of B cell lymphoma cells, including PEL cells. NF-κB signaling is upregulated by proteasome-dependent degradation of IκBα. The suppression of NF-κB signaling by proteasome inhibitors may contribute to the induction of apoptosis in PEL cells. In addition, proteasome activity is required for KSHV replication in KSHV latently infected PEL cells. MG132 reduced the production of progeny virus from PEL cells at low concentrations, which do not affect PEL cell growth. These findings suggest that proteasome inhibitors may represent a novel strategy for the treatment of KSHV infection and KSHV-associated lymphomas.

9-(2-C-Cyano-2-deoxy-beta-D-arabino-pentofuranosyl)guanine, a potential antitumor agent against B-lymphoma infected with Kaposi's sarcoma-associated herpesvirus

Several 9-(2-C-cyano-2-deoxy-l-beta-d-arabino-pentofuranosyl)purine derivatives were tested against Kaposi's sarcoma-associated herpesvirus (KSHV)-infected primary effusion lymphoma (PEL) cells. The guanine derivative (3, CNDAG), as well as the 2-amino-6-substituted-purine derivatives 4, 5, and 6, exhibited cell growth inhibitory activity against KSHV-infected cells, but showed no cytotoxicity against KSHV-negative cells at >15 microM concentrations. Therefore, it was found that compounds 3, 4, 5, and 6 showed selective cytotoxicity against PEL cells infected with KSHV.