stilbenes and Burkitt-Lymphoma

Type I interferons (IFN) exert multiple effects on both the innate and adaptive immune system in addition to their antiviral and antiproliferative activities. Little is known, however about the direct effects of type I IFNs on germinal center (GC) B cells, the central components of adaptive B cell responses. We used Burkitt's lymphoma (BL) lines, as a model system of normal human GC B cells, to examine the effect of type I IFNs on the expression of BCL-6, the major regulator of the GC reaction. We show that type I IFNs, but not IFNγ, IL-2 and TNFα rapidly down-regulate BCL-6 protein and mRNA expression, in cell lines derived from endemic, but not from sporadic BL. IFNα-induced down-regulation is specific for BCL-6, independent of Epstein-Barr virus and is not accompanied by IRF-4 up-regulation. IFNα-induced BCL-6 mRNA down-regulation does not require de novo protein synthesis and is specifically inhibited by piceatannol. The proteasome inhibitor MG132 non-specifically prevents, while inhibitors of alternate type I IFN signaling pathways do not inhibit IFNα-induced BCL-6 protein downregulation. We validate our results with showing that IFNα rapidly down-regulates BCL-6 mRNA in purified mouse normal GC B cells. Our results identify type I IFNs as the first group of cytokines that can down-regulate BCL-6 expression directly in GC B cells.

Topics: Adaptor Proteins, Signal Transducing; Animals; B-Lymphocytes; Burkitt Lymphoma; Cell Line, Transformed; DNA-Binding Proteins; Down-Regulation; Gene Expression Regulation, Neoplastic; Germinal Center; Herpesvirus 4, Human; Humans; Interferon Regulatory Factors; Interferon-alpha; Interferon-gamma; Interleukin-2; Kinetics; Leupeptins; Mice; Protein Biosynthesis; Proto-Oncogene Proteins c-bcl-6; RNA-Binding Proteins; RNA, Messenger; Signal Transduction; Stilbenes; Transcription Factors; Tumor Necrosis Factor-alpha

Doxorubicin (DOX) has been used in a variety of human malignancies for decades, in particular of lymphoma. But increased cardiomyocyte apoptosis has been implicated in its cardiotoxicity. Resveratrol (RES) generates cardiovascular protective effects by heme oxygenase-1(HO-1)-mediated mechanism. The present study was designed to determine whether RES protected cardiomyocyte against apoptosis through induction of HO-1 in lymphoma nude mouse in vivo. After being developed into lymphoma model, 40 male Balb/c nude mice were randomized to one of the following four treatments (10 mice per group): control, DOX, DOX + RES and DOX + RES + HO-1 inhibitor (zinc protoporphyrin IX, ZnPP). The results showed that DOX injection markedly decreased the body weight, the heart weight and the ratio of heart weight to body weight, but inversely increased cardiomyocyte apoptosis and the level of serum lactate dehydrogenase and creatine kinase. Moreover, DOX injection attenuated HO-1 expression and enzymatic activity as well as increased P53 expression, modulated Bcl-2/Bax expression and enhanced caspase 3 activity. These cardiotoxic effects of DOX were ameliorated by its combination with RES. However, the protective effects of RES were reversed by the addition of ZnPP. Taken together, it is concluded that HO-1 plays a core role for protective action of RES in DOX-induced cardiomyocyte apoptosis in lymphoma nude mice.

Topics: Animals; Apoptosis; Burkitt Lymphoma; Cell Line, Tumor; Doxorubicin; Enzyme Induction; Heme Oxygenase-1; Humans; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Nude; Myocytes, Cardiac; Random Allocation; Resveratrol; Stilbenes; Xenograft Model Antitumor Assays

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.

Topics: Apoptosis; Burkitt Lymphoma; Cell Cycle Checkpoints; Cell Growth Processes; Cell Line, Tumor; Down-Regulation; Epstein-Barr Virus Infections; Gene Expression Regulation, Viral; Herpesvirus 4, Human; Humans; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; NF-kappa B; p38 Mitogen-Activated Protein Kinases; Resveratrol; Stilbenes; Viral Matrix Proteins; Virus Latency

Resveratrol (RES), a natural phytoalexin found at high levels in grapes and red wine, has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. However, the underlying molecular mechanisms are at present only partially understood.. The effects of RES on activation of unfolded protein responses (UPR) were evaluated using Western blotting, semi-quantitative and real-time RT-PCR. Cell death was evaluated using Annexin V/PI staining and subsequent FACS.. Similar as tunicamycin, treatment with RES lead to the activation of all 3 branches of the UPR, with early splicing of XBP-1 indicative of IRE1 activation, phosphorylation of eIF2alpha consistent with ER resident kinase (PERK) activation, activating transcription factor 6 (ATF6) splicing, and increase in expression levels of the downstream molecules GRP78/BiP, GRP94 and CHOP/GADD153 in human Burkitt's lymphoma Raji and Daudi cell lines. RES was shown to induce cell death, which could be attenuated by thwarting upregulation of CHOP.. Our data suggest that activation of the apoptotic arm of the UPR and its downstream effector CHOP/GADD153 is involved, at least in part, in RES-induced apoptosis in Burkitt's lymphoma cells.

Topics: Activating Transcription Factor 6; Antineoplastic Agents, Phytogenic; Blotting, Western; Burkitt Lymphoma; DNA-Binding Proteins; eIF-2 Kinase; Endoplasmic Reticulum Chaperone BiP; Heat-Shock Proteins; Humans; Membrane Glycoproteins; Phosphorylation; Regulatory Factor X Transcription Factors; Resveratrol; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Stilbenes; Transcription Factor CHOP; Transcription Factors; Tumor Cells, Cultured; Unfolded Protein Response; Vasodilator Agents; X-Box Binding Protein 1

The mammalian target of rapamycin (mTOR) is emerging as a promising target for antitumor therapy. However, the mechanism that contributes to its regulation in B lymphomas remains unknown. This study shows that in follicular lymphoma (FL) cells, mTOR is active because the cells displayed rapamycin-sensitive phosphorylation of p70S6 kinase and 4E-BP1. Moreover, immunohistochemistry applied on lymph node tissue sections obtained from patients with FL revealed that, in most cases, p70S6 kinase was highly phosphorylated compared to normal tonsillar tissue. In FL cells, mTOR was under control of both phospholipase D (PLD) and phosphatidylinositol 3-kinase (PI3K). Moreover, we demonstrated that Syk plays a central role in mTOR activation because we found that both expression and activity are elevated compared to normal or chronic lymphocytic leukemia B cells. We also provide evidence that Syk operates through PLD- and PI3K-independent pathways. Finally, Syk inhibition by piceatannol or by siRNA plasmids resulted in a potent inhibition of mTOR activity in FL cells, as well as in mantle cell lymphoma, Burkitt lymphoma, and diffuse large B-cell lymphoma. These findings suggest that the Syk-mTOR pathway has a critical function in FL survival, and therefore, that Syk could be a promising new target for B-lymphoma therapy.

Topics: Burkitt Lymphoma; Cell Line, Tumor; Enzyme Activation; Humans; Intracellular Signaling Peptides and Proteins; Leukemia, Lymphocytic, Chronic, B-Cell; Lymph Nodes; Lymphoma, B-Cell; Lymphoma, Follicular; Lymphoma, Mantle-Cell; Neoplasm Proteins; Palatine Tonsil; Phosphatidylinositol 3-Kinases; Phospholipase D; Protein Kinases; Protein-Tyrosine Kinases; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Small Interfering; Signal Transduction; Stilbenes; Syk Kinase; TOR Serine-Threonine Kinases

Development of the chimeric mouse antihuman CD20 antibody, Rituximab, presented a notable advance in the treatment of patients with non-Hodgkin's lymphoma (NHL). Its use allowed the specific targeting of tumor B cells without the systemic toxicity of traditional therapies. The mechanisms by which Rituximab induces its antitumor activity are not fully understood. We have shown previously that Rituximab down-regulates Bcl-2 expression in some B-NHL cell lymphoma lines through an interleukin 10 (IL-10)-dependent autocrine loop, an effect that renders the resistant cells susceptible to chemotherapeutic drugs. The objective of this study was to delineate the signaling pathway by which Bcl-2 is controlled by Rituximab and IL-10. We hypothesized that the down-regulation of IL-10 by Rituximab decreases activation of the signal transducer and activator of transcription 3 (STAT3) protein, which in turn, is responsible for decreased levels of Bcl-2. We demonstrate by phosphoprotein immunoblotting and gel shift analyses that endogenous IL-10 induces activation of STAT3 in the 2F7 cell line. Furthermore, we show that Rituximab and anti-IL-10 antibody treatment decreases the ability of STAT3 to bind to its DNA binding site. The decrease in STAT3 activation by these treatments correlates with a decrease in Bcl-2 expression. Additionally, piceatannol, an inhibitor of STAT3 activation, down-regulates the expression of Bcl-2. Altogether, these results demonstrate that Bcl-2 expression is under the regulation of the STAT3 signaling pathway, which is regulated by endogenously secreted IL-10. Hence, Rituximab-induced down-regulation of IL-10 expression is responsible for the down-regulation of Bcl-2 and sensitization of NHL cells by therapeutic drugs. Furthermore, these findings support the notion that circulating IL-10 in vivo may control the resistance of NHL to drug-mediated cytotoxicity.

Topics: Antibodies; Antibodies, Monoclonal; Antibodies, Monoclonal, Murine-Derived; Antineoplastic Agents; Burkitt Lymphoma; Culture Media, Serum-Free; DNA-Binding Proteins; Down-Regulation; Drug Synergism; Humans; Interleukin-10; Phosphorylation; Proto-Oncogene Proteins c-bcl-2; Rituximab; Signal Transduction; STAT3 Transcription Factor; Stilbenes; Trans-Activators

The stilbene phytochemicals resveratrol and piceatannol have been reported to possess substantial antitumorigenic and antileukemic activities, respectively. Although recent experimental data revealed the proapoptotic potency of resveratrol, the molecular mechanisms underlying the antileukemic activity have not yet been studied in detail. In the present study, we show that resveratrol, as well as the hydroxylated analog piceatannol, are potent inducers of apoptotic cell death in BJAB Burkitt-like lymphoma cells with an ED50 concentration of 25 microM. Further experiments revealed that treatment of BJAB cells with both substances led to a concentration-dependent activation of caspase-3 and mitochondrial permeability transition. Using BJAB cells overexpressing a dominant-negative mutant of the Fas-associated death domain (FADD) adaptor protein to block death receptor-mediated apoptosis, we demonstrate that resveratrol- and piceatannol-induced cell death in these cells is independent of the CD95/Fas signaling pathway. To explore the antileukemic properties of both compounds in more detail, we extended our study to primary, leukemic lymphoblasts. Interestingly, piceatannol but not resveratrol is a very efficient inducer of apoptosis in this ex vivo assay with leukemic lymphoblasts of 21 patients suffering from childhood lymphoblastic leukemia (ALL).

Topics: Adolescent; Anticarcinogenic Agents; Antineoplastic Agents; Apoptosis; Burkitt Lymphoma; Caspase 3; Caspases; Cell Nucleus; Child; Child, Preschool; DNA Fragmentation; Dose-Response Relationship, Drug; fas Receptor; Female; Humans; Infant; Leukemia, Lymphoid; Male; Membrane Potentials; Mitochondria; Resveratrol; Signal Transduction; Stilbenes; Tumor Cells, Cultured