Antiproliferative and pro-apoptotic activity of novel phenolic derivatives of resveratrol.

Gloriosaols A-C, isolated from Yucca gloriosa (Agavaceae), are novel phenolic compounds structurally related to resveratrol. In the present study, we show that gloriosaols possess antiproliferative and pro-apoptotic activity on tumor cells of different histogenetic origin and that their cell growth inhibition potential is higher than that of resveratrol. Despite the close similarities in their structure, gloriosaols A-C exhibited different antiproliferative potency, as the EC(50) ascending order is: gloriosaol C, gloriosaol A, gloriosaol B. Further mechanisms of gloriosaol C cytotoxicity were elucidated in detail in U937 cells, the most sensitive of the cell lines tested. The effect of gloriosaol C on cell growth turned out to be strongly dependent upon the concentration. Gloriosaol C doses lower than the EC(50) value (8 mu-icroM) blocked the cell cycle in G(0)/G(1), with a concurrent decrease in the number of cells in the G(2)/M phases of the cell cycle. At higher doses, this arrest overlaps with the occurrence of apoptosis and necrosis. In the 10-25 microM range of doses, gloriosaol C caused cell death mainly by apoptosis, as measured by hypodiploidia induction, phosphatidyl serine externalization and disruption of mitochondrial transmembrane potential. A switch in the mode of death from apoptosis to necrosis occurred at doses of gloriosaol C higher than 30 microM. Gloriosaol C was found to induce production of reactive species dose-dependently, but also to counteract their elevation in stressed cells. Thus, the different fate of cells, that is cell cycle arrest or cell death, in response to different doses of gloriosaol C might be related to the extent of induced oxidative stress.

Oxidative stress and neuroAIDS: triggers, modulators and novel antioxidants.

Neurological disorders represent one of the most common disturbances accompanying HIV infection. In the past few years, highly antiretroviral active therapy has significantly reduced the incidence of HIV-related diseases. However, neurological dysfunction in AIDS patients still remains an unresolved problem. Oxidative stress, which occurs in brain tissues of patients undergoing HIV infection and is implicated in cell death of both astroglia and neurones, has recently been suggested to play a role in the pathogenesis of neuroAIDS. Thus, a better understanding of the processes that trigger and modulate free radical formation in brain tissues of AIDS patients might help in a successful therapeutic approach to the neuropathogenesis of HIV infection.

Transferrin-like autocrine growth factor, derived from T-lymphoma cells, that inhibits normal T-cell proliferation.

Transferrin, the major iron-binding protein in the plasma of vertebrate species, is an essential growth factor for cells in serum free medium. We have established a cell line, Fr, from peripheral blood mononuclear cells of a patient affected by Sézary syndrome. Fr cells show a very immature antigenic phenotype, while constitutively bearing transferrin receptor on their surface. Furthermore the Fr line does not produce or respond to interleukin 2. Finally its conditioned medium contains both a growth stimulating activity for the Fr cell line and a factor which inhibits T-lymphocyte proliferation. We have identified a protein, produced in large amounts by Fr cells, which shares the immunological properties of human transferrin. Our data suggest that this transferrin-like factor can act as an autocrine growth factor for the producer cells and as an inhibitory factor for normal lymphocytes.

Enhancement of viral gene expression in Friend erythroleukemic cells by 12-O tetradecanoylphorbol-13-acetate.

Tumor-promoting agents are known to inhibit the specific differentiation processes of several animal cell systems in vitro, including the Friend leukemia cell system. We have examined the effect of 12-O tetradecanoylphorbol-13-acetate (TPA) on the latter system and have investigated its action on Friend virus expression. At a concentration of 16.7 nM, TPA inhibits the dimethyl sulfoxide-induced Friend cell terminal differentiation and, at the same time, enhances the expression of the Friend virus genome, as demonstrated by a 2-fold increase in the amount of reverse transcriptase-containing particles released into the culture fluid and in the levels of virus-specific intracytoplasmic RNA. The greatest effect of TPA is evident after 24 hr of treatment. At this time, TPA exerts also its strongest effect upon the induction of the plasminogen activator. Our results indicate that two specific effects of TPA, i.e., block of differentiation and induction of plasminogen activator, correlate well in the Friend cell system with an extracellular and intracellular increase in virus expression.

NF-kappaB/Rel-mediated regulation of apoptosis in hematologic malignancies and normal hematopoietic progenitors.

The activity of NF-kappaB/Rel transcription factors can downmodulate apoptosis in normal and neoplastic cells of the hematologic and other compartments, contributing in maintaining neoplastic clone survival and impairing response to therapy. Alterations in nfkappab or ikappaB genes are documented in some hematologic neoplasias, while in others dysfunction in NF-kappaB/Rel-activating signaling pathways can be recognized. The prosurvival properties of NF-kappaB/Rel appear to rely on the induced expression of molecules (caspase inhibitors, Bcl2 protein family members, etc.), which interfere with the apoptosis pathway. Constitutive NF-kappaB/Rel activity in some hematologic malignancies could be advantageous for neoplastic clone expansion by counteracting stress stimuli (consumption of growth factors and metabolites) and immune system-triggered apoptosis; it is furthermore likely to play a central role in determining resistance to therapy. Based on this evidence, NF-kappaB/Rel-blocking approaches have been introduced in antineoplastic strategies. The identification of NF-kappaB/Rel target genes relevant for survival in specific neoplasias is required in order to address tailored therapies and avoid possible detrimental effects due to widespread NF-kappaB/Rel inhibition. Moreover, comparative analyses of normal hematopoietic progenitors and neoplastic cell sensitivities to inhibitors of NF-kappaB/Rel and their target genes will allow to evaluate the impact of these tools on normal bone marrow.

Growth inhibition and synergistic induction of apoptosis by zoledronate and dexamethasone in human myeloma cell lines.

Bisphosphonates (BPs) are commonly used in the treatment of myeloma-associated osteolytic lesions. Recent reports have suggested that BPs may also exert direct antitumor effects on myeloma cells. Here, we show that the treatment of myeloma cell lines with the combination of the potent BP zoledronate and dexamethasone inhibits cell growth and synergistically induces apoptotic cell death, providing a rationale for potential applications in vivo.

T cell growth-promoting activity of interferon-gamma. Mitogenic effect of the recombinant cytokine on cells from a human T-chronic lymphocytic leukemia.

Interferon-gamma (IFN-gamma) has previously been described as exerting a growth factor activity for murine and human stimulated normal T lymphocytes, in addition to its established role in regulating the cytotoxic activity of T and NK cells. We analyzed the effect of human recombinant IFN-gamma on the proliferation of leukemic lymphocytes isolated from the peripheral blood of a patient affected by a T-cell chronic lymphocytic leukemia (T-CLL). Incubation with IFN-gamma induced the proliferation of unstimulated leukemic cells. Cell proliferation was maximal after 6 days of culture with the cytokine; the half-maximal effect of IFN-gamma was observed at a concentration of approximately 800 U/ml. We also measured the production of IFN-gamma by leukemic cells. Cells incubated in control medium released small quantities of IFN-gamma activity, while the addition of low doses of the exogenous cytokine to the cell cultures induced high levels of IFN-gamma mRNA and protein production. Furthermore, anti-HLA class I monoclonal antibodies, that exert a mitogenic effect on these neoplastic lymphocytes, also induced the IFN-gamma gene expression in the same cells. These results indicate that IFN-gamma may stimulate the proliferation of human neoplastic T cells and suggest that this cytokine might have a role in the expansion of T-leukemic cell clones in vivo.

BAG3 regulates formation of the SNARE complex and insulin secretion.

Insulin release in response to glucose stimulation requires exocytosis of insulin-containing granules. Glucose stimulation of beta cells leads to focal adhesion kinase (FAK) phosphorylation, which acts on the Rho family proteins (Rho, Rac and Cdc42) that direct F-actin remodeling. This process requires docking and fusion of secretory vesicles to the release sites at the plasma membrane and is a complex mechanism that is mediated by SNAREs. This transiently disrupts the F-actin barrier and allows the redistribution of the insulin-containing granules to more peripheral regions of the ß cell, hence facilitating insulin secretion. In this manuscript, we show for the first time that BAG3 plays an important role in this process. We show that BAG3 downregulation results in increased insulin secretion in response to glucose stimulation and in disruption of the F-actin network. Moreover, we show that BAG3 binds to SNAP-25 and syntaxin-1, two components of the t-SNARE complex preventing the interaction between SNAP-25 and syntaxin-1. Upon glucose stimulation BAG3 is phosphorylated by FAK and dissociates from SNAP-25 allowing the formation of the SNARE complex, destabilization of the F-actin network and insulin release.

A novel miR-371a-5p-mediated pathway, leading to BAG3 upregulation in cardiomyocytes in response to epinephrine, is lost in Takotsubo cardiomyopathy.

Molecular mechanisms protecting cardiomyocytes from stress-induced death, including tension stress, are essential for cardiac physiology and defects in these protective mechanisms can result in pathological alterations. Bcl2-associated athanogene 3 (BAG3) is expressed in cardiomyocytes and is a component of the chaperone-assisted autophagy pathway, essential for homeostasis of mechanically altered cells. BAG3 ablation in mice results in a lethal cardiomyopathy soon after birth and mutations of this gene have been associated with different cardiomyopathies including stress-induced Takotsubo cardiomyopathy (TTC). The pathogenic mechanism leading to TTC has not been defined, but it has been suggested that the heart can be damaged by excessive epinephrine (epi) spillover in the absence of a protective mechanism. The aim of this study was to provide more evidence for a role of BAG3 in the pathogenesis of TTC. Therefore, we sequenced BAG3 gene in 70 TTC patients and in 81 healthy donors with the absence of evaluable cardiovascular disease. Mutations and polymorphisms detected in the BAG3 gene included a frequent nucleotide change g2252c in the BAG3 3'-untranslated region (3'-UTR) of Takotsubo patients (P<0.05), resulting in loss of binding of microRNA-371a-5p (miR-371a-5p) as evidenced by dual-luciferase reporter assays and argonaute RNA-induced silencing complex catalytic component 2/pull-down assays. Moreover, we describe a novel signaling pathway in cardiomyocytes that leads to BAG3 upregulation on exposure to epi through an ERK-dependent upregulation of miR-371a-5p. In conclusion, the presence of a g2252c polymorphism in the BAG3 3'-UTR determines loss of miR-371a-5p binding and results in an altered response to epi, potentially representing a new molecular mechanism that contributes to TTC pathogenesis.

Oxaliplatin (L-OHP) treatment of human myeloma cells induces in vitro growth inhibition and apoptotic cell death.

Oxaliplatin (L-OHP), a diaminocyclohexane platinum derivative, is an active and well tolerated anticancer drug which is presently used in the treatment of gastrointestinal tumours. Since the efficacy of L-OHP in the treatment of multiple myeloma (MM) has not yet been evaluated, we studied the antiproliferative activity of this compound in vitro in a panel of MM cell lines (XG1, XG1a, U266 and IM-9). We found that L-OHP inhibited the growth of MM cells at therapeutically achievable concentrations (IC(50): 5-10 microM after 24 h of exposure) and was more active than Cisplatin (CDDP) or Carboplatin (CBDCA). The activity of L-OHP was apparently not affected by interleukin-6 (IL-6), the major growth and survival factor of MM cells. We also found that L-OHP induced apoptotic cell death. We demonstrated that the combination of L-OHP with Dexamethasone (Dex) resulted in the enhancement of the anti-myeloma effects. L-OHP and Dex both induced poly adenosine diphosphate (ADP)-ribose polymerase (PARP) cleavage and this induction was enhanced by the combined treatment. L-OHP-induced apoptosis correlated with caspase-3 cleavage, but this correlation could not be demonstrated in Dex-treated cells. Taken together, these in vitro results provide a rationale for the experimental use of L-OHP in the treatment of MM patients and suggest therapeutic combinations of potential value.

Analysis of peripheral blood normal and malignant cells with the novel murine monoclonal antibody UN2.

The monoclonal antibody (mAb) UN2 was generated upon immunization of a Balb/c mouse with human thymocytes. mAb UN2 recognized an antigen expressed by a subpopulation of human thymocytes and peripheral blood lymphocytes. In thymus, mAb UN2 recognized cortical cells; its expression was higher on CD3bright than on CD3dim thymocytes. This antigen was also detected on peripheral blood granulocytes, monocytes, platelets and on cell lines MOLT4, U937 and KG1. mAb UN2 was submitted to the 5th International Workshop and Conference on Human Leukocyte Differentiation Antigens, Boston, MA, 1993, and was assigned to the CD31. Expression of the UN2-recognized antigen in malignant lymphoid cells from 57 cases of B-cell chronic lymphoproliferative disease and 4 of B-cell acute lymphoblastic leukemia was analysed in flow cytometry. Among the 57 cases of B-cell chronic lymphoproliferative malignancies studied, 49 were classified as B-cell chronic lymphocytic leukemia. These showed high (86 +/- 8%) UN2 antigen expression. In 8 cases of hairy-cell leukemia the percentage of cells reacting with mAb UN2 was 42 +/- 4%; the fluorescence intensity of labelled cells was lower than that displayed by cells of B-cell chronic lymphocytic leukemia and comparable to that of normal lymphoid cells. mAb UN2 could prove useful in analysis of the lymphoid development and diagnostics of B-cell chronic lymphoproliferative disorders.

A novel monoclonal antibody recognizing human thymocytes and B-cell chronic lymphocytic leukemia cells.

This paper describes a new murine monoclonal antibody, UN5, raised against human thymocytes. This antibody recognizes a molecule of approximately 45 kDa on thymocytes. Flow cytometric analysis reveals a high intensity of labeling with the majority of thymocytes, whereas only CD20+ cells from peripheral whole-blood samples are weakly stained. Peripheral T cells, granulocytes, platelets and red blood cells do not express this antigen, while monocytes are only weakly labeled by UN5. Furthermore, the UN5 antibody discriminates between different types of B-cell malignancies, reacting with a subgroup of B-cell chronic lymphocytic leukemias and hairy cell leukemias, but not with the other kinds of hematopoietic malignancies tested. Antibody UN5 should prove a useful tool for the study of T-cell precursors and for analysis of both normal and neoplastic B cells.

CD40 and B chronic lymphocytic leukemia cell response to fludarabine: the influence of NF-kappaB/Rel transcription factors on chemotherapy-induced apoptosis.

The levels of tumour necrosis factor receptor (TNF-R) superfamily members can be altered in lymphoid leukemias, indicating a possible role of such molecules in the biology of these neoplasias. In B chronic lymphocytic leukemia cells, the CD40/CD40L system has been shown to be effective in inhibiting the apoptotic response to fludarabine. The modulation of apoptosis relied on the CD40-induced activity of NF-kappaB/Rel transcription factors. The anti-apoptotic effect of CD40 was abolished using a phosphorothioate kappaB decoy oligodeoxynucleotide. These findings illustrate an example of the biological activity of TNF-R-like molecules in leukemias. They also show the influence of NF-kappaB/Rel activity on leukemic cell response to apoptogenic agents.

BAG3 controls angiogenesis through regulation of ERK phosphorylation.

BAG3 is a co-chaperone of the heat shock protein (Hsp) 70, is expressed in many cell types upon cell stress, however, its expression is constitutive in many tumours. We and others have previously shown that in neoplastic cells BAG3 exerts an anti-apoptotic function thus favoring tumour progression. As a consequence we have proposed BAG3 as a target of antineoplastic therapies. Here we identify a novel role for BAG3 in regulation of neo-angiogenesis and show that its downregulation results in reduced angiogenesis therefore expanding the role of BAG3 as a therapeutical target. In brief we show that BAG3 is expressed in endothelial cells and is essential for the interaction between ERK and its phosphatase DUSP6, as a consequence its removal results in reduced binding of DUSP6 to ERK and sustained ERK phosphorylation that in turn determines increased levels of p21 and p15 and cell-cycle arrest in the G1 phase.

BAG3: a multifaceted protein that regulates major cell pathways.

Bcl2-associated athanogene 3 (BAG3) protein is a member of BAG family of co-chaperones that interacts with the ATPase domain of the heat shock protein (Hsp) 70 through BAG domain (110-124 amino acids). BAG3 is the only member of the family to be induced by stressful stimuli, mainly through the activity of heat shock factor 1 on bag3 gene promoter. In addition to the BAG domain, BAG3 contains also a WW domain and a proline-rich (PXXP) repeat, that mediate binding to partners different from Hsp70. These multifaceted interactions underlie BAG3 ability to modulate major biological processes, that is, apoptosis, development, cytoskeleton organization and autophagy, thereby mediating cell adaptive responses to stressful stimuli. In normal cells, BAG3 is constitutively present in a very few cell types, including cardiomyocytes and skeletal muscle cells, in which the protein appears to contribute to cell resistance to mechanical stress. A growing body of evidence indicate that BAG3 is instead expressed in several tumor types. In different tumor contexts, BAG3 protein was reported to sustain cell survival, resistance to therapy, and/or motility and metastatization. In some tumor types, down-modulation of BAG3 levels was shown, as a proof-of-principle, to inhibit neoplastic cell growth in animal models. This review attempts to outline the emerging mechanisms that can underlie some of the biological activities of the protein, focusing on implications in tumor progression.