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A better understanding of multiple myeloma (MM) biology has led to the development of novel therapies. However, MM is still an incurable disease and new pharmacological strategies are needed. Dinaciclib, a multiple cyclin‐dependent kinase (CDK) inhibitor, which inhibits CDK1, 2, 5 and 9, displays significant antimyeloma activity as found in phase II clinical trials. In this study, we have explored the mechanism of dinaciclib‐induced death and evaluated its enhancement by different BH3 mimetics in MM cell lines as well as in plasma cells from MM patients. Our results indicate a synergistic effect of dinaciclib‐based combinations with B‐cell lymphoma 2 or B‐cell lymphoma extra‐large inhibitors, especially in MM cell lines with partial dependence on myeloid cell leukemia sequence 1 (MCL‐1). Simultaneous treatment with dinaciclib and BH3 mimetics ABT‐199 or A‐1155463 additionally showed a synergistic effect in plasma cells from MM patients, ex vivo. Altered MM cytogenetics did not affect dinaciclib response ex vivo, alone or in combined treatment, suggesting that these combinations could be a suitable therapeutic option for patients bearing cytogenetic alterations and poor prognosis. This work also opens the possibility to explore cyclin‐dependent kinase 9 inhibition as a targeted therapy in MM patients overexpressing or with high dependence on MCL‐1. [ABSTRACT FROM AUTHOR]

OBJECTIVE: We previously observed that T lymphocytes present in synovial fluid (SF) from patients with rheumatoid arthritis (RA) were sensitive to APO2L/TRAIL. In addition, there was a drastic decrease in the amount of bioactive APO2L/TRAIL associated with exosomes in SF from RA patients. This study was undertaken to evaluate the effectiveness of bioactive APO2L/TRAIL conjugated with artificial lipid vesicles resembling natural exosomes as a treatment in a rabbit model of antigen-induced arthritis (AIA). METHODS: We used a novel Ni(2+)-(N-5-amino-1-carboxypentyl)-iminodiacetic acid)-containing liposomal system. APO2L/TRAIL bound to liposomes was intraarticularly injected into the knees of animals with AIA. One week after treatment, rabbits were killed, and arthritic synovial tissue was analyzed. RESULTS: Tethering APO2L/TRAIL to the liposome membrane increased its bioactivity and resulted in more effective treatment of AIA compared with soluble, unconjugated APO2L/TRAIL, with substantially reduced synovial hyperplasia and inflammation in rabbit knee joints. The results of biophysical studies suggested that the increased bioactivity of APO2L/TRAIL associated with liposomes was due to the increase in the local concentration of the recombinant protein, augmenting its receptor crosslinking potential, and not to conformational changes in the protein. In spite of this increase in bioactivity, the treatment lacked systemic toxicity and was not hepatotoxic. CONCLUSION: Our findings indicate that binding APO2L/TRAIL to the liposome membrane increases its bioactivity and results in effective treatment of AIA. [ABSTRACT FROM AUTHOR]

Induction of reactive oxygen species (ROS) is a hallmark of granzyme B (gzmB)-mediated pro-apoptotic processes and target cell death. However, it is unclear to what extent the generated ROS derive from mitochondrial and/or extra-mitochondrial sources. To clarify this point, we have produced a mutant EL4 cell line, termed EL4-ρ0, which lacks mitochondrial DNA, associated with a decreased mitochondrial membrane potential and a defective ROS production through the electron transport chain of oxidative phosphorylation. When incubated with either recombinant gzmB plus streptolysin or ex vivo gzmB+ cytotoxic T cells, EL4-ρ0 cells showed phosphatydylserine translocation, caspase 3 activation, Bak conformational change, cytochrome c release and apoptotic morphology comparable to EL4 cells. Moreover, EL4-ρ0 cells produced ROS at levels similar to EL4 under these conditions. GzmB-mediated ROS production was almost totally abolished in both cell lines by the pan-caspase inhibitor, Z-VAD-fmk. However, addition of apocynin, a specific inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, led to a significant reduction of ROS production and cell death only in EL4-ρ0 but not EL4 cells. These data suggest that gzmB-induced cell death is accompanied by a caspase-dependent pathway of extra-mitochondrial ROS production, most probably through activation of NADPH oxidase. [ABSTRACT FROM AUTHOR]

Abstract: Interferon-α (IFN-α) is currently used for the therapy of multiple myeloma (MM) though it is only effective in some patients. IFN-α induces apoptosis in some MM cell lines and it has been proposed to occur through an autocrine loop involving Apo2L/TRAIL. We have analysed the sensitivity to IFN-α and Apo2L/TRAIL of five MM cell lines and found no correlation between the apoptosis inducing ability of both cytokines. IFN-α-induced apoptosis in MM cells was not prevented by a caspase-8 selective inhibitor (Z-IETD-fmk) or blocking Apo2L/TRAIL. However, human monocytes treated with IFN-α release bioactive Apo2L/TRAIL to culture media which was cytotoxic for MM cells resistant to IFN-α. We propose that Apo2L/TRAIL released from IFN-α-stimulated blood monocytes would be a major mediator of the anti-myeloma effect of IFN-α in vivo. [Copyright &y& Elsevier]

The mechanisms responsible for the down-modulation of the activation of separated CD4 or CD8 human T cell blasts were studied using cells obtained from healthy donors. In the presence of IL-2, human CD8 T cell blasts were more sensitive than CD4 T cell blasts to regulation by APO2 ligand/TNF-related apoptosis-inducing ligand (APO2L/TRAIL), while both T cell subsets were equally sensitive to Fas/CD95 regulation. This regulation was defined as inhibition of IL-2-dependent T cell growth in the absence of cell death induction, characterized by cell cycle arrest in G/M. The physiological validity of these observations was corroborated by the demonstration of intracellular FasL and APO2L/TRAIL expression in CD4 and CD8 T cell blasts, which were secreted in their bioactive form into the supernatant upon PHA, CD3 or CD59 reactivation. Additionally, the inhibition of IL-2-dependent CD4 or CD8 T cell blast growth upon CD3 or CD59 ligation was dependent, at least partially, on FasL and/or APO2L/TRAIL. These data precisely define the role of APO2L/TRAIL in the regulation of human T cell activation. [ABSTRACT FROM AUTHOR]