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In B-chronic lymphocytic leukemia (B-CLL), the interaction between leukemic cells and the microenvironment promotes tumor cell survival. The Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib is one of the first-in-class molecules for the treatment of B-CLL patients, however, the emerging mechanisms of resistance to ibrutinib call for new therapeutic strategies. The purpose of the current study was to investigate the ability of ibrutinib plus the MDM2-inhibitor nutlin-3 to counteract the tumor microenvironment protective effect. We observed that primary B-CLL cells cultivated in microenvironment mimicking conditions were protected from apoptosis by the up-regulation of c-MYC and of p53. In the same setting, combined treatments with ibrutinib plus nutlin-3 led to significantly higher levels of apoptosis compared to the single treatments, counteracting the c-MYC up-regulation. Moreover, the combination induced high p53 levels and a significant dissipation of the mitochondrial membrane potential, together with BAX cleavage in the more active p18 form and phospho-BAD down-regulation, that are key components of the mitochondrial apoptotic pathway, enhancing the apoptosis level. Our findings propose a new therapeutic strategy to overcome the tumor microenvironment protection involved in B-CLL resistance to drugs, with possible clinical implications also for other hematologic and solid tumors for which ibrutinib is considered a therapeutic option.

Innate and adaptive immune responses have a well-known link and represent the distinctive origins of several diseases, many of which may be the consequence of the loss of balance between these two responses. Indeed, autoinflammation and autoimmunity represent the two extremes of a continuous spectrum of pathologic conditions with numerous overlaps in different pathologies. A common characteristic of these dysregulations is represented by hyperinflammation, which is an exaggerated response of the immune system, especially involving white blood cells, macrophages, and inflammasome activation with the hyperproduction of cytokines in response to various triggering stimuli. Moreover, hyperinflammation is of great interest, as it is one of the main manifestations of COVID-19 infection, and the cytokine storm and its most important components are the targets of the pharmacological treatments used to combat COVID-19 damage. In this context, the purpose of our review is to provide a focus on the pathogenesis of autoinflammation and, in particular, of hyperinflammation in order to generate insights for the identification of new therapeutic targets and strategies.

Mitoquinone (MitoQ) is a mitochondrial reactive oxygen species scavenger that is characterized by high bioavailability. Prior studies have demonstrated its neuroprotective potential. Indeed, the release of reactive oxygen species due to damage to mitochondrial components plays a pivotal role in the pathogenesis of several neurodegenerative diseases. The present study aimed to examine the impact of the inflammation platform activation on the neuronal cell line (DAOY) treated with specific inflammatory stimuli and whether MitoQ addition can modulate these deregulations. DAOY cells were pre-treated with MitoQ and then stimulated by a blockade of the cholesterol pathway, also called mevalonate pathway, using a statin, mimicking cholesterol deregulation, a common parameter present in some neurodegenerative and autoinflammatory diseases. To verify the role played by MitoQ, we examined the expression of genes involved in the inflammation mechanism and the mitochondrial activity at different time points. In this experimental design, MitoQ showed a protective effect against the blockade of the mevalonate pathway in a short period (12 h) but did not persist for a long time (24 and 48 h). The results obtained highlight the anti-inflammatory properties of MitoQ and open the question about its application as an effective adjuvant for the treatment of the autoinflammatory disease characterized by a cholesterol deregulation pathway that involves mitochondrial homeostasis.

Background and Aims Cardiovascular disease is the main cause of death worldwide, but the collective efforts to prevent this pathological condition are directed exclusively to individuals at higher risk due to hypercholesterolemia, hypertension, obesity, diabetes. Recently, vitamin D deficiency was identified as a risk factor for cardiovascular disease in healthy people, as it predisposes to different vascular dysfunctions that can result in plaque development and fragility. In this scenario, the fundamental aim of the study was to reproduce a disease model inducing vitamin D deficiency and atheromatosis in ApoE-/- mice and then to evaluate the impact of this vitamin D status on the onset/progression of atheromatosis, focusing on plaque formation and instability. Methods and Results In our murine disease model, vitamin D deficiency was achieved by 3 weeks of vitamin D deficient diet along with intraperitoneal paricalcitol injections, while atheromatosis by western-type diet. Under these experimental conditions, vitamin D deficient mice developed more unstable atheromatous plaques with reduced or absent fibrotic cap. Since calcium and phosphorus metabolism and also cholesterol and triglycerides systemic concentration were not affected by vitamin D level, our results highlighted the role of vitamin D deficiency in the formation/instability of atheromatous plaque and, although further studies are needed, suggested a possible intervention with vitamin D to prevent or delay the atheromatous disease. Conclusions The data obtained open the question about the potential role of the vitamins in the pharmacological treatments of cardiovascular disorders as coadjutant of the primary drugs used for these pathologies., Graphical abstract Image 1, Highlights • The vitamin D deficiency represents a risk factor for cardiovascular disease. • The vitamin D deficiency has been correlated to atheromatosis progression. • A model of vitamin D deficiency was fundamental to evaluate the role of the vitamin D the onset/progression of atheromatosis. • The vitamin D deficiency was clearly involved in an early formation of atherosclerotic lesions. • The vitamins play a potential role in the pharmacological treatments of cardiovascular disorders.

Mevalonate Kinase Deficiency (MKD) is a rare inborn disease belonging to the family of periodic fever syndromes. The MKD phenotype is characterized by systemic inflammation involving multiple organs, including the nervous system. Current anti-inflammatory approaches to MKD are only partially effective and do not act specifically on neural inflammation. According to the new emerging pharmacology trends, the repositioning of drugs from the indication for which they were originally intended to another one can make mechanistic-based medications easily available to treat rare diseases. According to this perspective, the squalene synthase inhibitor Lapaquistat (TAK-475), originally developed as a cholesterol-lowering drug, might find a new indication in MKD, by modulating the mevalonate cholesterol pathway, increasing the availability of anti-inflammatory isoprenoid intermediates. Using an in vitro model for MKD, we mimicked the blockade of the cholesterol pathway and evaluated the potential anti-inflammatory effect of Lapaquistat. The results obtained showed anti-inflammatory effects of Lapaquistat in association with a low blockade of the metabolic pathway, while this effect did not remain with a tighter blockade. On these bases, Lapaquistat could be configured as an effective treatment for MKD’s mild forms, in which the residual enzymatic activity is only reduced and not almost completely absent as in the severe forms.

// Rebecca Voltan 1, * , Erika Rimondi 2, * , Elisabetta Melloni 1 , Gian Matteo Rigolin 3 , Fabio Casciano 1 , Maria Vittoria Arcidiacono 1 , Claudio Celeghini 2 , Antonio Cuneo 3 , Giorgio Zauli 1 , Paola Secchiero 1 1 Department of Morphology, Surgery and Experimental Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy 2 Department of Life Sciences, University of Trieste, Trieste, Italy 3 Department of Medical Sciences, Section of Hematology, University of Ferrara, Ferrara, Italy * These authors have contributed equally to this work Correspondence to: Paola Secchiero, email: paola.secchiero@unife.it Keywords: B leukemic cells, Ibrutinib, MDM-2 inhibitors, apoptosis, combination therapy Received: July 20, 2016 Accepted: September 09, 2016 Published: September 20, 2016 ABSTRACT Objective: The aim of this study was to investigate the anti-leukemic activity of the Bruton tyrosine kinase inhibitor Ibrutinib in combination with the small molecule MDM-2 inhibitor Nutlin-3 in preclinical models. Methods: The potential efficacy of the Ibrutinib/Nutlin-3 combination was evaluated in vitro in a panel of B leukemic cell lines (EHEB, JVM-2, JVM-3, MEC-1, MEC-2) and in primary B-chronic lymphocytic leukemia (B-CLL) patient samples, by assessing cell viability, cell cycle profile, apoptosis and intracellular pathway modulations. Validation of the combination therapy was assessed in a B leukemic xenograft mouse model. Results: Ibrutinib exhibited variable anti-leukemic activity in vitro and the combination with Nutlin-3 synergistically enhanced the induction of apoptosis independently from the p53 status. Indeed, the Ibrutinib/Nutlin-3 combination was effective in promoting cytotoxicity also in primary B-CLL samples carrying 17p13 deletion and/or TP53 mutations, already in therapy with Ibrutinib. Molecular analyses performed on both B-leukemic cell lines as well as on primary B-CLL samples, while confirming the switch-off of the MAPK and PI3K pro-survival pathways by Ibrutinib, indicated that the synergism of action with Nutlin-3 was independent by p53 pathway and was accompanied by the activation of the DNA damage cascade signaling through the phosphorylation of the histone protein H2A.X. This observation was confirmed also in the JVM-2 B leukemic xenograft mouse model. Conclusions: Taken together, our data emphasize that the Ibrutinib/Nutlin-3 combination merits to be further evaluated as a therapeutic option for B-CLL.

// Paola Secchiero 1, * , Rebecca Voltan 1, * , Erika Rimondi 1 , Elisabetta Melloni 1 , Emmanouil Athanasakis 2 , Veronica Tisato 1 , Stefania Gallo 1 , Gian Matteo Rigolin 3 and Giorgio Zauli 1 1 Department of Morphology, Surgery and Experimental Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy 2 Institute for Maternal and Child Health, IRCCS “Burlo Garofolo”, Trieste, Italy 3 Department of Medical Sciences, Section of Hematology, University of Ferrara, Ferrara, Italy * These authors have contributed equally to this work Correspondence to: Giorgio Zauli, email: giorgio.zauli@unife.it Paola Secchiero, email: paola.secchiero@unife.it Keywords: B-leukemic cells, Ibrutinib, γ-secretase inhibitors, NOTCH1, combination therapy Received: May 05, 2017 Accepted: June 20, 2017 Published: July 22, 2017 ABSTRACT Ibrutinib blocks B-cell receptor signaling and interferes with leukemic cell-to-microenvironment interactions. Ibrutinib plays a key role in the management of B-CLL and is recommended for first line treatment of high-risk CLL patients with 17p deletion. Therefore, elucidating the factors governing sensitivity/resistance to Ibrutinib represents a relevant issue. For this purpose, in 3 B-CLL patient samples harboring functional TP53 mutations, the frequency of the mutated clones was monitored during in vivo Ibrutinib therapy, revealing a progressive decline of the frequency of TP53 mut clones during 12 months of treatment. In parallel, the anti-leukemic activity of Ibrutinib was assessed in vitro on B-CLL patient cell cultures in combination with γ-secretase inhibitors (GSI). In the in vitro assays, the combination of Ibrutinib+GSI exhibited enhanced cytotoxicity on B-CLL cells also in the presence of stroma and it was coupled to the down-regulation of the stroma-activated NOTCH1 and c-MYC pathways. Moreover, the combined treatment was effective in reducing CXCR4 expression and functions. Therefore, the ability of GSI to enhance the Ibrutinib anti-leukemic activity in B-CLL cells, by down-regulating the NOTCH1 and c-MYC pathways, warrants further experimentation for its potential therapeutic applications.

Metformin and the mitochondrial targeting dichloroacetate (DCA) have recently received attention due to their ability to inhibit anaerobic glycolysis, which renders most cancer cells resistant to apoptosis induction. We observed that Metformin alone exhibited a dose-dependent anti-leukemic activity in both B leukemic cell lines and primary B-chronic lymphocytic leukemia (B-CLL) patients' cells and its anti-leukemic activity was enhanced when used in combination with DCA. In order to overcome the problems of poor bioavailability and cellular uptake, which limit DCA efficacy, we have designed and synthetized cocrystals consisting of Metformin and DCA (Met-DCA) at different stoichiometric ratios. Of note, the MetH(2)(++)•2DCA(-) cocrystal exhibited enhanced in vitro anti-leukemic activity, with respect to the treatment with the mix consisting of Metformin plus DCA. In particular, the treatment with the cocrystal MetH(2)(++)•2DCA(-) induced a synergistic apoptotic cell death coupled to a marked down-modulation of the anti-apoptotic Mcl-1 protein. Taken together, our data emphasize that innovative compounds based on Metformin-DCA combination merit to be further evaluated as chemotherapeutic agents for the treatment of B-CLL.

To improve the pharmacokinetic profile of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) an N-terminal specific pegylation was performed to generate pegylated TRAIL (PEG-TRAIL). In in vitro experiments, we found that although PEG-TRAIL was slightly less efficient than recombinant TRAIL in promoting leukemic cell apoptosis, it showed an improved ability to promote migration of bone-marrow mesenchymal stem cells and to elicit the ERK1/2 intracellular signal transduction pathway. Overall, these data suggest that TRAIL pegylation retains, or even enhances, the biological activities of TRAIL relevant for its therapeutic applications.

We have compared the cytotoxic/cytostatic responses of the SKW6.4 lymphoblastoid B-cells to the alkylating agent chlorambucil, the purine analog fludarabine, the non-genotoxic activator of the p53 pathway, Nutlin-3, used alone or in association with the death-inducing ligand recombinant TRAIL. Exposure to chlorambucil, fludarabine, and Nutlin-3 induced p53 accumulation and variably affected cell cycle progression in SKW6.4 lymphoblastoid cells. In particular, chlorambucil induced cell cycle accumulation at the G2/M checkpoint; Nutlin-3 induced early cell cycle arrest at the G1/S checkpoint, while fludarabine showed an intermediate behavior. On the other hand, recombinant TRAIL alone did not affect cell cycle progression but induced a rapid increase of apoptosis. Analysis of the gene expression profile of the p53-transcriptional targets showed distinct features between chlorambucil, Nutlin-3 and fludarabine, which likely account for their differential effect on cell cycle in SKW6.4 cells. In particular, chlorambucil upregulated the steady-state mRNA expression of SFN/14-3-3sigma, a gene involved in G2/M cell cycle arrest. Of note, all agonists upregulated TRAIL-R2 expression in SKW6.4 cells both at the mRNA and protein levels. Consistently, pretreatment with chlorambucil, fludarabine and Nutlin-3 enhanced SKW6.4 sensitivity to TRAIL-mediated apoptosis.

It has been clearly established that receptor activator of nuclear factor kappa B ligand (RANKL) is a key cytokine involved in the differentiation of osteoclastic precursors of the monocytic/macrophagic lineage. However, relatively little information is available on the ability of RANKL to modulate the expression of genes controlling cell survival/apoptosis and proliferation in human osteoclastic cells in comparison to macrophages. For this purpose, CD14+ human peripheral blood mononuclear cells, which express the cognate high affinity receptor activator of nuclear factor kappa B (RANK), were differentiated along the macrophagic or osteoclastic lineage by adding macrophage-colony stimulating factor (M-CSF) or M-CSF plus RANKL in culture for 12 days. RANKL up-regulated the expression of the chemokine MIP1α, which potentiates osteoclastic differentiation and simultaneously activated both anti-apoptotic (Bcl-2) and pro-apoptotic (CIDEB, PYCARD, and BAK-1) genes. Moreover, RANKL markedly up-regulated cylin D2, while it significantly decreased the levels of cyclin A, cyclin-dependent kinase 2, and other cyclin-dependent kinases, in keeping with the notion that end-stage osteoclasts are nondividing cells. Finally, a long-term exposure of RANKL up-regulated the adaptor protein TRAF3 but not TRAF6. Anat Rec, 2007. © 2007 Wiley-Liss, Inc.

The role of the tumor necrosis factor (TNF) superfamily member receptor activator of nuclear factor kappa B ligand (RANKL) in promoting the differentiation of osteoclasts has been extensively characterized. In this study, we have investigated the effect of TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily of cytokines, in osteoclastogenesis, by using human peripheral blood mononuclear cells and the RAW264.7 murine monocytic cell line. Both cell models differentiate into osteoclast-like cells in presence of RANKL plus macrophage-colony-stimulating factor (M-CSF), as evaluated in terms of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and bone resorption activity. Unexpectedly, when added in culture in combination with RANKL plus M-CSF, TRAIL inhibited osteoclastic differentiation in both cell models. To investigate the molecular mechanism underlining such inhibitory activity, we analyzed the effect of TRAIL on the mitogen-activated protein kinases (MAPKs) pathways, which play a key role in osteoclastogenesis. Treatment with RANKL plus M-CSF activated both the ERK1/2 and p38/MAPK pathways, which are essential for proliferation and differentiation of preosteoclasts, respectively. Of note, the addition of TRAIL to RANKL plus M-CSF did not affect ERK1/2 but it profoundly inhibited p38/MAPK phosphorylation. Thus, our data demonstrate that TRAIL blocks osteoclastic differentiation and suggest that inhibition of the p38/MAPK pathway by TRAIL likely plays an important role in this process. (Blood. 2004;104:2044-2050)

// Chiara Agnoletto 1,* , Elisabetta Melloni 1,* , Fabio Casciano 1 , Gian Matteo Rigolin 2 , Erika Rimondi 3 , Claudio Celeghini 3 , Laura Brunelli 1 , Antonio Cuneo 2 , Paola Secchiero 1 , Giorgio Zauli 4 1 Department of Morphology, Surgery and Experimental Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy 2 Department of Medical Sciences, University of Ferrara-Arcispedale S.Anna, Ferrara, Italy 3 Department of Life Sciences, University of Trieste, Trieste, Italy 4 Institute for Maternal and Child Health, IRCCS “Burlo Garofolo”, Trieste, Italy * These two authors equally contributed to this work Correspondence: Paola Secchiero, email: // Keywords : Sodium dichloroacetate, Nutlin-3, B-CLL, p21 Received : March 21, 2014 Accepted : May 26, 2014 Published : May 26, 2014 Abstract The anti-leukemic activity of the mitochondria-targeting small molecule sodium dichloroacetate (DCA), used alone and in association with the small molecule inhibitor of the p53/MDM2 interaction Nutlin-3, was analyzed in primary B-chronic lymphocytic leukemia (B-CLL) samples (n=22), normal peripheral blood cells (n=10) and in p53 wild-type EHEB, JVM-2, JVM-3 B lymphoblastoid cell lines. DCA exhibited a dose-dependent anti-leukemic activity in both primary B-CLL and B leukemic cell lines with a functional p53 status and showed a synergistic cytotoxic activity when used in combination with Nutlin-3. At the molecular level, DCA positively regulated p53 activity, as documented by post-transcriptional modifications of p53 protein, and synergized with Nutlin-3 in increasing the expression of the p53-target genes MDM2 , PUMA , TIGAR and in particular p21 . The potential role of p21 in mediating the DCA+Nutlin-3 anti-leukemic activity was underscored in knocking-down experiments. Indeed, transfection of leukemic cells with p21 siRNAs significantly decreased the DCA+Nutlin-3-induced cytotoxicity. Taken together, our data emphasize that DCA is a molecule that merits to be further evaluated as a chemotherapeutic agent for B-CLL, likely in combination with other therapeutic compounds.

Dear Editor: It has been extensively documented that osteoprotegerin (OPG), a soluble member of the TNF receptor superfamily, inhibits osteoclastogenesis by binding to receptor activator of NF-kB ligand (RANKL) and preventing interaction with its cognate transmembrane receptor RANK [reviewed in 1]. However, OPG can also interact with, and neutralize, TNF-related apoptosis inducing ligand (TRAIL), whose extracellular domain shares a 30% homology with the extracellular domain of RANKL [reviewed in 2]. Although some inconsistencies on the differential binding affinity of OPG for RANKL versus TRAIL were present in initial studies [2, 3], it has been recently demonstrated that the affinity of native OPG for native TRAIL is comparable to that for RANKL (45 nM versus 23 nM, respectively) at 37°C, as determined by plasmon surface resonance analysis [4]. Consistently with this biochemical study, OPG has been shown to act in a paracrine and autocrine manner by binding TRAIL and promoting the survival of multiple myeloma [5], prostate cancer [6], ameloblastoma cells [7] and synovial fibroblasts [8]. Interestingly, previous data from different groups have shown that recombinant TRAIL modulates the differentiation of erythroid and myeloid precursors [9–10], while inhibits both human and mouse osteoclastogenesis when added to pre-osteoclast cultures induced to differentiate with recombinant macrophage colony-stimulating factor (M-CSF) +RANKL as well as to mature osteoclasts [11–14]. On the other hand, a couple of studies suggested that recombinant soluble TRAIL might promote osteoclastogenesis [4, 15], and the proposed molecular mechanism to explain such observation was a competition between TRAIL and RANKL for OPG binding. However, it should be noticed that Vitovsky et al. used much higher concentrations of TRAIL (500 ng/ml) than RANKL (30 ng/ml) or OPG (50 ng/ml) and more importantly used mouse bone marrow pre-osteoclasts [4]. In this respect, it has been clearly shown that mouse pre-osteoclasts only express TRAIL-R2 [2], while human peripheral blood-derived pre-osteoclasts express both death receptors TRAIL-R1 and TRAIL-R2 as well as TRAIL-R4 [11–14]. Therefore, to further elucidate the important issue of the interplay between RANKL, TRAIL and OPG in human osteoclastogenesis, we have cultured adherent PBMC with M-CSF+RANKL for 14 days in the absence or presence of recombinant OPG and recombinant TRAIL, prepared as previously described [16]. TRAIL and OPG were added alone or in combination. Importantly, all cytokines were used at the same concentration (50 ng/ml). As expected [11–14], the addition of TRAIL to M-CSF+RANKL significantly (P < 0.05) inhibited osteoclast formation (Fig. 1A and B). Of note, recombinant OPG completely abrograted (P < 0.05) osteoclast formation irrespectively of the presence of recombinant TRAIL in culture (Fig. 1A and B). The anti-osteoclastic activity of OPG could not be ascribed to a low affinity of OPG for TRAIL since OPG (50 ng/ml) efficiently inhibited the apoptosis induced by TRAIL (50 ng/ml) in HL-60 leukemic cells (data not shown). 1 Effect of combined treatment of RANKL, TRAIL and OPG on osteoclastic differentiation. Adherent PBMC were cultured with M-CSF alone for 6 days. Then cells were cultured for additional 14 days with the addition of RANKL in the absence or presence of TRAIL ... Our current observations on one hand confirm that TRAIL has anti-osteoclastic activity and on the other hand indicate that it does not affect the potent anti-osteoclastic activity of OPG at least in the simplified model of osteoclastogenesis represented by human PBMC induced to differentiate by M-CSF+RANKL. Taken together with previous studies [4, 11–15], these data also suggest that the relative concentrations of TRAIL, RANKL and OPG in the local microenvironment are likely key determinant for the regulation of osteoclastogenesis.

Osteoprotegerin (OPG) is a soluble member of the tumor necrosis factor (TNF) receptor family, initially characterized for its ability to inhibit the receptor activator of NFkB ligand (RANKL)-stimulated formation of osteoclasts [1]. OPG also interacts with TNF-related apoptosis inducing ligand (TRAIL) [2], a different member of the TNF super-family whose extracellular domain shares a 35% homology with RANKL [3]. Several studies have demonstrated that OPG is elevated in the serum/plasma of patients affected by different types of cancer (reviewed in [4]), but the potential role of OPG with respect to cancer development/progression is unknown. Among different potential cellular sources of circulating OPG, endothelial cells represent a major source of OPG under basal conditions as well as in response to inflammatory stimuli [5]. Hydrogen sulfide (H2S)—known for decades as a toxic gas—is endogenously generated from cysteine, in reactions catalyzed by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) [6–8]. Mounting data on endogenously generated H2S have now included this gas in the family of gasotransmitters, together with nitric oxide (NO) and carbon monoxide (CO), and its effects are intensively investigated both at the cellular and molecular level [7]. On these bases, the aim of the present study was to investigate in vitro the effect of H2S on the expression and release of OPG by human vascular endothelial cells in the absence or presence of the pro-inflammatory cytokine TNF-α.

The soluble member of the TNF-R superfamily osteoprotegerin (OPG) is abundantly released under basal conditions by both mesenchymal stem cells (MSC) and fibroblasts and by endothelial cells upon stimulation with inflammatory cytokines. Since MSC, fibroblasts and endothelial cells represent key elements of the normal and tumor microenvironment and express detectable levels of surface TRAIL receptors, we investigated the effect of TRAIL on OPG release. Unexpectedly, recombinant TRAIL decreased the spontaneous OPG release in all cell types examined. Moreover, TRAIL decreased OPG release also in stromal cells co-cultured with lymphoma cells and counteracted the OPG induction by TN-alpha in HUVEC and MSC. Such down-regulation was not due to a masking effect in the ELISA quantification of the OPG released in the culture supernatants due to binding of OPG to its ligands (TRAIL and RANKL), as demonstrated by competition experiments with recombinant TRAIL and by the lack of RANKL release/induction. In addition, OPG down-regulation was not due to induction of cytotoxic effects by TRAIL, since the degree of apoptosis in response to TRAIL was negligible in all primary cell types. With regards to the possible molecular mechanism accounting for the down-regulation of OPG release by TRAIL, we found that treatment of MSC with TRAIL significantly decreased the phosphorylation levels of p38/MAPK. There is a suggestion that this pathway is involved in the stabilization of OPG mRNA. In this respect, the ability of TRAIL to decrease the release of OPG, in the absence of cell cytotoxicity, was mimicked by the p38/MAPK inhibitor SB203580.

The effect of the single-chain alkylphospholipid perifosine was analyzed in p53(wild-type) (SKW6.4, OCI and MOLM), p53(mutated) (BJAB, MAVER) and p53(null) (HL-60) leukemic cell lines. Perifosine promoted cytotoxicity with a combination of apoptosis induction in all cell lines and cell cycle block at the G(2)M checkpoint, which was selectively observed in p53(mutated) BJAB and MAVER cell lines. At the molecular level, perifosine induced hypophosphorylation of retinoblastoma protein and the degradation of E2F1 protein in p53(mutated) but not in p53(wild-type) cells. These data indicate that perifosine potentially represents an innovative therapeutic approach for p53(mutated) hematological malignancies.

We have analyzed the effect of the synthetic glucocorticoid dexamethasone, used alone or in combination with recombinant TRAIL, on in vitro osteoclastic differentiation of peripheral blood-derived macrophages cultured in the presence of macrophage-colony stimulating factor (M-CSF) + RANKL for 12-14 days. Dexamethasone exhibited different effects based on the concentration used. Indeed, while at 10(-7) M dexamethasone reduced the number of mature osteoclasts, at 10(-8) M showed no significant effects and at 10(-9) M significantly increased the number of mature osteoclasts, with respect to cells cultured with only M-CSF + RANKL. On the other hand, the addition in culture of recombinant TRAIL inhibited the output of mature osteoclasts induced by M-CSF + RANKL. However, the presence of dexamethasone (10(-8) or 10(-9) M) into the culture medium significantly counteracted the anti-osteoclastic activity of TRAIL. In order to ascertain whether dexamethasone, might also interfere with the anti-leukemic activity of TRAIL, the degree of apoptosis induced by TRAIL was evaluated in several myeloid (OCI, MOLM, HL-60) and lymphoid (SKW6.4, MAVER, BJAB) leukemic cell lines. The levels of TRAIL-triggered apoptosis were not significantly different between leukemic cells cultured in the absence or presence of dexamethasone. Concerning the molecular mechanism mediating the dexamethasone-suppression of the TRAIL activity in pre-osteoclasts, but not in leukemic cells, we found that dexamethasone induced a significant down-regulation of the surface levels of TRAIL-R2 in cells of the osteoclastic lineage but not in leukemic cells. The ability of dexamethasone to counteract the TRAIL pathway envisions a novel mechanism mediating the pro-osteoclastic activity of dexamethasone in vivo.

Protein kinase C (PKC)-epsilon, a component of the serine/threonine PKC family, has been shown to influence the survival and differentiation pathways of normal hematopoietic cells. Here, we have modulated the activity of PKC-epsilon with specific small molecule activator or inhibitor peptides. PKC-epsilon inhibitor and activator peptides showed modest effects on HL-60 maturation when added alone, but PKC-epsilon activator peptide significantly counteracted the pro-maturative activity of tumor necrosis factor (TNF)-alpha towards the monocytic/macrophagic lineage, as evaluated in terms of CD14 surface expression and morphological analyses. Moreover, while PKC-epsilon inhibitor peptide showed a reproducible increase of TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis, PKC-epsilon activator peptide potently counteracted the pro-apoptotic activity of TRAIL. Taken together, the anti-maturative and anti-apoptotic activities of PKC-epsilon envision a potentially important proleukemic role of this PKC family member.

The small molecule inhibitor of the MDM2/p53 interaction Nutlin-3 significantly up-regulated the steady-state mRNA and protein levels of Notch1 in TP53wild-type (OCI, SKW6.4) but not in TP53deleted (HL-60) or TP53mutated (BJAB) leukemic cell lines. A direct demonstration that NOTCH1 was a transcriptional target of p53 in leukemic cells was obtained in experiments carried out with siRNA for p53. Moreover, inhibition of Notch1 expression using Notch1-specific siRNA significantly increased cytotoxicity in TP53wild-type leukemic cells. Of note, Nutlin-3 up-regulated Notch1 expression also in primary TP53wild-type B-chronic lymphocytic leukemia (B-CLL) cells and the combined use of Nutlin-3 plus pharmacological γ-secretase inhibitors of the Notch signaling showed a synergistic cytotoxicity in both TP53wild-type leukemic cell lines and primary B-CLL cells. A potential drawback of γ-secretase inhibitors was their ability to enhance osteoclastic maturation of normal circulating preosteoclasts induced by RANKL + M-CSF. Notwithstanding, Nutlin-3 completely suppressed osteoclastogenesis irrespective of the presence of γ-secretase inhibitors. Taken together, these data indicate that the p53-dependent up-regulation of Notch1 in response to Nutlin-3 represents an antiapoptotic feedback mechanism able to restrain the potential therapeutic efficacy of Nutlin-3 in hematologic malignancies. Therefore, therapeutic combinations of Nutlin-3 + γ-secretase inhibitors might potentiate the cytotoxicity of Nutlin-3 in p53wild-type leukemic cells.

Experimental evidences indicate that the TNF family member TNF-related apoptosis inducing ligand (TRAIL) might be involved in modulating osteoclastic differentiation. The ability of recombinant soluble TRAIL to affect bone density in vivo was evaluated by using 4-week-old mice subcutaneously (s.c.) injected with TRAIL for 8 days. TRAIL injection induced a significant increase of tibia trabecular thickness and total bone mass in 4-week-old mice, accompanied by a significant decrease of TRAP serum levels, without modulation of osteocalcin and osteoprotegerin (OPG). Parallel experiments performed in vitro showed that inhibition of osteoclastic differentiation, induced by treatment of human peripheral blood osteoclast precursors with TRAIL, was associated to inhibition of receptor activator of nuclear factor kappa B ligand (RANKL)-induced accumulation of p27(Kip1). The potential role of p27(Kip1) pathway in mediating the anti-osteoclastic activity of TRAIL was further suggested by in vitro gene knock-down experiments performed in osteoclast precursor cultures. Taken together, our data strongly suggest that recombinant TRAIL inhibits osteoclastogenesis by inducing the ubiquitin-mediated degradation of p27(Kip1).

Exposure of human pre-osteoclasts to the MDM2 antagonist Nutlin-3 activated the p53 pathway and significantly decreased the entry of pre-osteoclasts in the S phase in response to RANKL. Moreover, repeated exposure to Nutlin-3 suppressed osteoclastic differentiation, without affecting cell survival at any culture time. Introduction: The p53 oncosuppressor coordinates an intracellular network involved in protection from malignant transformation and cell cycle control; its activation is tightly regulated by the murine double minute 2 (MDM2) gene and p53-MDM 2 interaction can be disrupted by selective small molecule inhibitors, the Nutlins. Although the ability of Nutlins to suppress the growth of wildtype p53 tumors has been clearly established, their biological activity in normal cells and tissues has not been extensively studied. Materials and Methods: Peripheral blood mononuclear cell pre-osteoclasts were cultured with macrophage-colony stimulating factor (M-CSF ) + RANKL or co-cultured with SaOS-2 osteosarcoma cells in the presence of IL-1β to induce osteoclastic differentiation. Cell cycle was analyzed by BrdU incorporation. The degree of osteoclastic differentiation was monitored at different culture times by TRACP and DAPI staining, as well as by TRACP-5b ELISA. Finally, the role of p53 in mediating the biological activity of Nutlin-3 was studied using specific siRNA. Results: Exposure of human pre-osteoclasts to RANKL induced an early (24 h) increase in the percentage of cells in the S phase, followed by the exit from the cell cycle at later time-points. The simultaneous addition of Nutlin-3 and RANKL dose-dependently decreased the percentage of pre-osteoclasts in the S phase and induced a rapid accumulation of p53 protein coupled with the induction of p53 target genes. Unexpectedly, the administration of Nutlin-3 to pre-osteoclasts at early culture times significantly suppressed the final output of osteoclasts at day 14 of culture. The role of p53 in mediating this biological activity of Nutlin-3 was underscored by gene knockdown experiments, in which the anti-osteoclastic activity of Nutlin-3 was significantly counteracted by siRNA specific for p53. Nutlin-3 also significantly decreased the formation of osteoclasts in a co-culture system of SaOS-2 osteosarcoma and pre-osteoclastic cells. Conclusions: These findings indicate that Nutlin-3 abrogates both pre-osteoclastic proliferation and differentiation through a p53-dependent pathway and may have therapeutic implications for those neoplastic diseases characterized by an abnormal osteoclastic activity.

Human and rat primary sub-cultured vascular smooth muscle cells (VSMCs) showed clear expression of the death receptors TRAIL-R1 and TRAIL-R2; however, recombinant soluble TRAIL did not induce cell death when added to these cells. TRAIL tended to protect rat VSMCs from apoptosis induced either by inflammatory cytokines tumor necrosis factor-alpha + interleukin-1beta + interferon-gamma or by prolonged serum withdrawal, and promoted a significant increase in VSMC proliferation and migration. Of note, all the biological effects induced by TRAIL were significantly inhibited by pharmacological inhibitors of the ERK pathway. Western blot analysis consistently showed that TRAIL induced a significant activation of ERK1/2, and a much weaker phosphorylation of Akt, while it did not affect the p38/MAPK pathway. Taken together, these data strengthen the notion that the TRAIL/TRAIL-R system likely plays a role in the biology of the vascular system by affecting the survival, migration and proliferation of VSMCs.