Marwan El-Sabban

Bone marrow mesenchymal stem cell transplantation in patients with multiple sclerosis: A pilot study☆

We explore the safety, and therapeutic benefit of intrathecal injection of ex-vivo expanded autologous bone marrow derived mesenchymal stem cells (BM-MSCs) in 10 patients with advanced multiple sclerosis (MS). Patients were assessed at 3, 6 and 12 months. Assessment at 3-6 months revealed Expanded Disability Scale Score (EDSS) improvement in 5/7, stabilization in 1/7, and worsening in 1/7 patients. MRI at 3 months revealed new or enlarging lesions in 5/7 and Gadolinium (Gd+) enhancing lesions in 3/7 patients. Vision and low contrast sensitivity testing at 3 months showed improvement in 5/6 and worsening in 1/6 patients. Early results show hints of clinical but not radiological efficacy and evidence of safety with no serious adverse events.

Connexins: a myriad of functions extending beyond assembly of gap junction channels.

Connexins constitute a large family of trans-membrane proteins that allow intercellular communication and the transfer of ions and small signaling molecules between cells. Recent studies have revealed complex translational and post-translational mechanisms that regulate connexin synthesis, maturation, membrane transport and degradation that in turn modulate gap junction intercellular communication. With the growing myriad of connexin interacting proteins, including cytoskeletal elements, junctional proteins, and enzymes, gap junctions are now perceived, not only as channels between neighboring cells, but as signaling complexes that regulate cell function and transformation. Connexins have also been shown to form functional hemichannels and have roles altogether independent of channel functions, where they exert their effects on proliferation and other aspects of life and death of the cell through mostly-undefined mechanisms. This review provides an updated overview of current knowledge of connexins and their interacting proteins, and it describes connexin modulation in disease and tumorigenesis.

New therapeutic approaches for adult T-cell leukaemia

Adult T-cell leukaemia or lymphoma is an aggressive malignant disease of mature activated T cells caused by human T-cell lymphotropic virus type I. Patients with this disease have a very poor outlook because of intrinsic chemoresistance and severe immunosuppression. In acute adult T-cell leukaemia, clinical trials in Japan show that although non-targeted combinations of chemotherapy improve response, they do not have a significant effect on complete remission and survival. Antiretroviral therapy with combination zidovudine and interferon alfa, which induces a high rate of complete remission and lengthens survival, should be the first treatment option in acute adult T-cell leukaemia. Patients with adult T-cell lymphoma might benefit from initial aggressive chemotherapy followed by antiretroviral therapy. To prevent relapse in all patients allogeneic bone-marrow transplantation when feasible, or additional targeted therapy, should be mandatory. Based on current pathophysiology, we discuss promising new drugs such as arsenic trioxide, proteasome inhibitors, retinoids, and angiogenesis inhibitors, as well as cellular immunotherapy.

Ceramide generation by two distinct pathways in tumor necrosis factor α‐induced cell death

Ceramide accumulation in the cell can occur from either hydrolysis of sphingomyelin or by de novo synthesis. In this study, we found that blocking de novo ceramide synthesis significantly inhibits ceramide accumulation and subsequent cell death in response to tumor necrosis factor α. When cells were pre‐treated with glutathione, a proposed cellular regulator of neutral sphingomyelinase, inhibition of ceramide accumulation at early time points was achieved with attenuation of cell death. Inhibition of both pathways achieved near‐complete inhibition of ceramide accumulation and cell death indicating that both pathways of ceramide generation are stimulated. This illustrates the complexity of ceramide generation in cytokine action.

Efficacy and mechanism of action of the proteasome inhibitor PS-341 in T-cell lymphomas and HTLV-I associated adult T-cell leukemia/lymphoma

HTLV-I associated adult T-cell leukemia (ATL) and HTLV-I-negative peripheral T-cell lymphomas are associated with poor prognosis. Using pharmacological concentrations of the proteasome inhibitor PS-341, we demonstrate inhibition of cell proliferation and induction of apoptosis in fresh ATL cells, HTLV-I transformed and HTLV-I-negative malignant T cells, while normal resting or activated T lymphocytes were resistant. Combination of PS-341 and doxorubicin or etoposide resulted in an additive growth inhibition. In HTLV-I-negative malignant cells, PS-341 treatment significantly downregulated the antiapoptotic protein X-IAP and to a lesser extent c-IAP-1 and bcl-XL and resulted in caspase-dependent apoptosis. In HTLV-I transformed cells, the inhibition of the proteasomal degradation of Tax by PS-341 likely explains the relative protection of HTLV-I infected cells against caspase-dependent apoptosis. PS-341 treatment of these cells stabilized IκBα, IκBβ, IκBɛ, p21, p27 and p53 proteins and selectively inhibited Rel-A DNA binding NF-κB complexes. In both HTLV-I-positive and -negative cells, PS-341 treatment induced ceramide accumulation that correlated with apoptosis. We conclude that PS-341 affects multiple pathways critical for the survival of HTLV-I-positive and -negative malignant T cells supporting a potential therapeutic role for PS-341 in both ATL and HTLV-I-negative T-cell lymphomas, whether alone or in combination with chemotherapy.

ECM-induced gap junctional communication enhances mammary epithelial cell differentiation.

The relationship between gap junctional intercellular communication (GJIC) and mammary cell (CID-9) differentiation in vitro was explored. CID-9 cells differentiate and express β-casein in an extracellular matrix (ECM)- and hormone-dependent manner. In response to interaction with the ECM, cells in culture modulated the expression of their gap junction proteins at the transcriptional and post-translational levels. In the presence of EHS-matrix, connexins (Cx)26, 32 and 43 localized predominantly to the plasma membrane, and enhanced GJIC [as measured by Lucifer Yellow (LY) dye transfer assays] was noted. Inhibition of GJIC of cells on EHS-matrix with 18α glycyrrhetinic acid (GA) resulted in reversible downregulation of β-casein expression. In the presence of cAMP, cells cultured on plastic expressed β-casein, upregulated Cx43 and Cx26 protein levels and enhanced GJIC. This was reversed in the presence of 18α GA. cAMP-treated cells plated either on a non-adhesive PolyHEMA substratum or on plastic supplemented with function-blocking anti-β1 integrin antibodies, maintainedβ -casein expression. These studies suggest that cell-ECM interaction alone may induce differentiation through changes in cAMP levels and formation of functional gap junctions. That these events are downstream of ECM signalling was underscored by the fact that enhanced GJIC induced partial differentiation in mammary epithelial cells in the absence of an exogenously provided basement membrane and in a β1-integrin- and adhesion-independent manner.

Evidence against a direct cytotoxic effect of alpha interferon and zidovudine in HTLV-I associated adult T cell leukemia/lymphoma

The combination of the anti-viral agents, zidovudine (AZT) and interferon-α (IFN), is a potent treatment of HTLV-I-associated adult T cell leukemia/lymphoma (ATL). In this study we investigate the possible mechanism of action of this combination by examining several cellular parameters including cell proliferation, cell cycle distribution and apoptosis. The ATL-derived T cell lines HuT-102 and MT-2 served as models. HTLV-I negative T cell lines (CEM and Jurkat) were used as controls. No significant modification of cell growth was observed except at suprapharmacological doses of AZT and IFN. Moreover, these effects were less pronounced in HTLV-I-infected cell lines compared to control cell lines. AZT and IFN treatment did not induce any significant modification of the expression of bcl-2 and p53. Interestingly no in vitrocytotoxic effect of AZT/IFN combination was observed on fresh leukemic cells derived from an acute ATL patient at diagnosis despite achievement of in vivo complete remission using the same therapy. These results suggest that the therapeutic effect of AZT and IFN is not through a direct cytotoxic effect of these drugs on the leukemic cells.

Therapy-induced selective loss of leukemia-initiating activity in murine adult T cell leukemia

Treatment with a combination of interferon-α and arsenic trioxide ablates leukemia-initiating activity before reducing primary tumor bulk in a murine model of adult T cell leukemia.

Ubiquitylated Tax targets and binds the IKK signalosome at the centrosome

Constitutive activation of the NF-κB pathway by the Tax oncoprotein plays a crucial role in the proliferation and transformation of HTLV-I infected T lymphocytes. We have previously shown that Tax ubiquitylation on C-terminal lysines is critical for binding of Tax to IκB kinase (IKK) and its subsequent activation. Here, we report that ubiquitylated Tax is not associated with active cytosolic IKK subunits, but binds endogenous IKK-α, -β, -γ, targeting them to the centrosome. K63-ubiquitylated Tax colocalizes at the centrosome with IKK-γ, while K48-ubiquitylated Tax is stabilized upon proteasome inhibition. Altogether, these results support a model in which K63-ubiquitylated Tax activates IKK in a centrosome-associated signalosome, leading to the production of Tax-free active cytoplasmic IKK. These observations highlight an unsuspected link between Tax-induced IKK activation and the centrosome.

Protective Effect of Vitamin E on Ultraviolet B Light-Induced Damage in Keratinocytes

Ultraviolet (UV) B radiation is the most common environmental factor in the pathogenesis of skin cancer. Exposure of human skin to UVB radiation leads to the depletion of cutaneous antioxidants, the activation of nuclear factor kappa B (NF‐κB), and programmed cell death (apoptosis). Although antioxidant supplementation has been shown to prevent UVB‐induced photooxidative damage, its effect on components of cell signaling pathways leading to gene expression has not been clearly established. In the present study, the effect of the antioxidant vitamin, α‐tocopherol (α‐T), and its acetate analog, α‐tocopherol acetate (α‐TAc), on UVB‐induced damage in primary and neoplastic mouse keratinocytes was investigated. The ability of both vitamins to modulate UVB‐induced apoptosis and activation of the transcription factor NF‐κB were studied. Treatment of normal and neoplastic mouse epidermal keratinocytes (308 cells) with 30–60 mJ/cm2 UVB markedly decreased viable cell number and was accompanied by DNA fragmentation. When both vitamins were applied to cells at times before and after UVB radiation, a significant increase in the percentage of viable cells and concomitant decrease in the number of apoptotic cells was noted, with vitamin pretreatment providing a better protection than posttreatment. Simultaneous posttreatment of irradiated cells with α‐TAc abolished the cytotoxic effects of UVB and restored cell viability to control levels. In addition, simultaneous posttreatment of irradiated cells with α‐T reduced the number of apoptotic cells by half, indicating a synergistic effect of two such treatments compared with any single one. Flow cytometry analysis indicated that vitamin treatment suppressed both an increase in pre‐G0 cells and a decrease in cycling cells by UVB exposure. In addition, NF‐κB activation was detected 2 h after UV exposure and was maintained for up to 8 h. Pretreatment with vitamins significantly inhibited NF‐κB activation at 4 and 8 h. These results indicate that vitamin E and its acetate analog can modulate the cellular response to UVB partly through their action on NF‐κB activation. Thus, these antioxidant vitamins are potential drugs for the protection from or the reduction of UVB‐associated epidermal damage.