Resveratrol inhibits proliferation and survival of Epstein Barr virus-infected Burkitt's lymphoma cells depending on viral latency program

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a polyphenolic natural product, shows chemopreventive properties against several cancers, heart diseases, inflammation, and viral infections. Epstein Barr virus (EBV), a γ-herpesvirus, contributes to the development of several human cancers including Burkitt's lymphoma (BL). In this study, we asked whether treatment with resveratrol would affect the viability of EBV-positive BL cells displaying different forms of latency. We report here that resveratrol, regardless of EBV status, induces caspase-dependent apoptosis by arresting cell-cycle progression in G(1) phase. However, resveratrol strongly induced apoptosis in EBV(-) and latency I EBV(+) cells, whereas latency II and latency III EBV(+) BL cells showed a survival advantage that increased with the extent of the pattern of viral gene expression. Resveratrol-induced cell-cycle arrest and apoptosis occurred in association with induction of p38 MAPK phosphorylation and suppression of ERK1/2 signaling pathway. Moreover, NF-κB DNA-binding activity was inhibited in all BL lines except EBV(+) latency III cells. LMP1 oncogene, which is expressed in latency III phenotype, is involved with the higher resistance to the antiproliferative effect of resveratrol because siRNA-mediated inhibition of LMP1 greatly increased the sensitivity of latency III BL cells as well as that of lymphoblastoid cell lines to the polyphenol. We propose that a combined resveratrol/siRNA strategy may be a novel approach for the treatment of EBV-associated B-cell malignancies in which the viral pattern of gene expression has been defined.

The nuclear lamina and its proposed roles in tumorigenesis: Projection on the hematologic malignancies and future targeted therapy

The nuclear lamina, a network of lamin filaments and lamin-associated proteins, is located between the inner nuclear membrane and the peripheral chromatin. The nuclear lamina is involved in numerous nuclear functions including maintaining nuclear shape, determining nuclear positioning, organizing chromatin and regulating the cell cycle, DNA replication, transcription, cell differentiation, apoptosis, and aging. Alterations in the composition of nuclear lamins and their associated proteins are currently emerging as an additional event involved in malignant transformation, tumor propagation and progression, thus identifying potential novel targets for future anti-cancer therapy. Here, we review the current knowledge on lamin expression patterns in cells of hematologic malignancies and give an overview on the roles of the nuclear lamina proteins in heterochromatin organization, apoptosis, and aging with special emphasis on the relevance in cancer development.

Nonlamin components of the lamina: a paucity of proteins

Current models of nuclear organization propose that nuclear functions are modulated in part by reversible tethering of chromatin loops to structural elements of the nucleoplasm and the nuclear envelope. Lamins are the best-characterized proteins of the lamina portion of the nuclear envelope and are involved in binding chromatin to the inner nuclear membrane. However, they are not a universal feature of eukaryotic nuclei and do not account fully for the putative functions of the lamina in all organisms. It is possible that nonlamin components of the lamina may substitute for lamins in organisms from which they are absent and modify the properties of lamins during development and the cell cycle. We review the properties of the relatively small number of such components that have been reported, including the young arrest (fs(1)Ya) protein of Drosophila, statin, circumferin, and the MAN antigens. The experimental evidence indicates they are a diverse group of proteins, and that at least some have the potential to modulate the interactions of chromatin, lamins, and the nuclear membranes.Key words: nuclear envelope, lamina, YA protein, statin, circumferin.

Velcro in the nuclear envelope: LBR and LAPs

The nuclear envelope is crucial for the functional organization of the nucleus. Lamin B receptor (LBR) and several lamina-associated proteins (LAPs), residing in the inner membrane, provide attachment sites for chromatin and the nuclear lamina. LAPs and LAP-related proteins are members of a growing family of proteins, whose genes are expressed in a tissue and development specific manner, opening the opportunity for a complex regulation of membrane-chromatin and membrane-lamina interactions. Post-translational modifications of LBR and LAPs are likely to modulate their binding to lamins and chromatin, interactions that need to be dynamic to accommodate nuclear growth in interphase and nuclear envelope disassembly in mitosis. Accumulation of proteins in the inner nuclear membrane is believed to depend on their retention mediated by the interaction with nuclear components such as chromatin and lamins.