Performance of a ventricular automatic-capture algorithm in a wide clinical setting.

BACKGROUND: The optimal programming of a pacemaker (PM) voltage output considers both efficiency (prolonging battery cell longevity) and patient safety (adequate safety margin). Currently, automatic capture (AC) algorithms are designed to ensure safe automatic stimulation threshold determination and pacing with a safety margin. METHODS: The aims of this prospective observational study were (1) to evaluate, over a short-term follow-up, the extent of backup pacing in patients implanted with an AC-featured PM produced by Boston Scientific (Insignia) and a wide range of ventricular leads; (2) to identify patient- or lead-specific predictors of ventricular threshold increase or missed detection of the ventricular pacing threshold; and (3) to analyze day-to-day fluctuations in the ventricular pacing threshold and the relationship between their magnitude, the characteristics of patients, and the system implanted. RESULTS: Five hundred and seventy-nine patients implanted with 89 different leads were followed up for a median of 2.1 months. Five hundred and thirty-six patients (92.5%) never experienced failure of automatic threshold testing; 571 (98.6%) did not experience permanent failure requiring continuous backup pacing at high energy. On multivariate analysis, none of the patient or lead characteristics predicted the occurrence of high-energy backup pacing during the study period. Day-to-day threshold fluctuations were associated only with higher thresholds (>1 V). CONCLUSION: AC algorithm reliably measures ventricular pacing thresholds in most patients: in only 1.4% of patients the system is permanently unable to detect the ventricular threshold. Backup pacing is not dependent on lead or patient characteristics, including lead polarization, polarity, and maturation.

The new tumor-suppressor gene inhibitor of growth family member 4 (ING4) regulates the production of proangiogenic molecules by myeloma cells and suppresses hypoxia-inducible factor-1 alpha (HIF-1alpha) activity: involvement in myeloma-induced angiogenesis.

Angiogenesis has a critical role in the pathophysiology of multiple myeloma (MM); however, the molecular mechanisms underlying this process are not completely elucidated. The new tumor-suppressor gene inhibitor of growth family member 4 (ING4) has been recently implicated in solid tumors as a repressor of angiogenesis. In this study, we found that ING4 expression in MM cells was correlated with the expression of the proangiogenic molecules interleukin-8 (IL-8) and osteopontin (OPN). Moreover, we demonstrate that ING4 suppression in MM cells up-regulated IL-8 and OPN, increasing the hypoxia inducible factor-1alpha (HIF-1alpha) activity and its target gene NIP-3 expression in hypoxic condition. In turn, we show that the inhibition of HIF-1alpha by siRNA suppressed IL-8 and OPN production by MM cells under hypoxia. A direct interaction between ING4 and the HIF prolyl hydroxylase 2 (HPH-2) was also demonstrated. Finally, we show that ING4 suppression in MM cells significantly increased vessel formation in vitro, blunted by blocking IL-8 or OPN. These in vitro observations were confirmed in vivo by finding that MM patients with high IL-8 production and microvascular density (MVD) have significantly lower ING4 levels compared with those with low IL-8 and MVD. Our data indicate that ING4 exerts an inhibitory effect on the production of proangiogenic molecules and consequently on MM-induced angiogenesis.

Production of Wnt inhibitors by myeloma cells: potential effects on canonical Wnt pathway in the bone microenvironment.

Osteoblast impairment occurs within multiple myeloma cell infiltration into the bone marrow. Canonical Wnt signaling activation in osteoprogenitor cells is involved in osteoblast formation through the stabilization of dephosphorylated beta-catenin and its nuclear translocation. The effects of multiple myeloma cells on Wnt signaling in human mesenchymal/osteoprogenitor cells are unclear. In 60 multiple myeloma patients checked, we found that among the Wnt inhibitors, Dickkopf-1 and secreted frizzled-related protein-3 were produced by multiple myeloma cells. However, although multiple myeloma cells or multiple myeloma bone marrow plasma affected expression of genes in the canonical Wnt signaling and inhibited beta-catenin stabilization in murine osteoprogenitor cells, they failed to block the canonical Wnt pathway in human mesenchymal or osteoprogenitor cells. Consistently, Wnt3a stimulation in human osteoprogenitor cells did not blunt the inhibitory effect of multiple myeloma cells on osteoblast formation. Consequently, despite the higher Wnt antagonist bone marrow levels in osteolytic multiple myeloma patients compared with nonosteolytic ones, beta-catenin immunostaining was not significantly different. Our results support the link between the production of Wnt antagonists by multiple myeloma cells and the presence of bone lesions in multiple myeloma patients but show that myeloma cells do not inhibit canonical Wnt signaling in human bone microenvironment.

The proteasome inhibitor bortezomib affects osteoblast differentiation in vitro and in vivo in multiple myeloma patients.

The proteasome inhibitor bortezomib may increase osteoblast-related markers in multiple myeloma (MM) patients; however, its potential osteoblastic stimulatory effect is not known. In this study, we show that bortezomib significantly induced a stimulatory effect on osteoblast markers in human mesenchymal cells without affecting the number of osteoblast progenitors in bone marrow cultures or the viability of mature osteoblasts. Consistently we found that bortezomib significantly increased the transcription factor Runx2/Cbfa1 activity in human osteoblast progenitors and osteoblasts without affecting nuclear and cytoplasmatic active beta-catenin levels. Consequently a stimulatory effect of bortezomib on bone nodule formation was also demonstrated in osteoblast progenitors. These in vitro observations were confirmed in vivo by the finding of a significant increase in the number of osteoblastic cells x mm(2) of bone tissue and in the number of Runx2/Cbfa1-positive osteoblastic cells that was observed in MM patients who responded to bortezomib. Our in vitro and in vivo observations support the hypothesis that a direct stimulatory effect on bone formation process could occur during bortezomib treatment.

Targeting pathways mediating bone disease.

Multiple myeloma (MM) is a plasma cell malignancy characterized by the high capacity to induce osteolytic bone lesions. Bone destruction in MM mainly depends on the increase of osteoclast formation and activity that occurs in close contact with myeloma cells infiltration. The histomorphometric studies, performed in MM patients, have demonstrated that MM patients with high plasma cell infiltrate are also characterized by a lower number of osteoblasts and a decreased bone formation that contributes, to the development of bone lesion. In the last years the progress in acknowledge of the pathophysiology of MM-induced osteolysis leaded to identify new therapeutics targets in MM bone disease and developed new drugs in the treatment of patients with skeletal involvement.

CXCR3 and its binding chemokines in myeloma cells: expression of isoforms and potential relationships with myeloma cell proliferation and survival.

BACKGROUND AND OBJECTIVES: The chemokine receptor CXCR3, involved in chemotaxis, is expressed on normal and malignant B cells and plasma cells. Recent data suggest that CXCR3-binding chemokines may also regulate proliferation and survival in endothelial cells through the interaction with two distinct isoforms of CXCR3 (CXCR3-A and CXCR3-B). DESIGN AND METHODS: We evaluated the potential expression of CXCR3 isoforms in myeloma cells, also investigating whether CXCR3 expression is affected by cell cycle and apoptosis. Furthermore, we assessed the effect of CXCR3 activation on myeloma cell proliferation and survival. RESULTS: We found that CXCR3 is widely expressed on human myeloma cell lines and freshly purified myeloma cells. The presence of both CXCR3 isoforms, CXCR3-A and CXCR3-B, was observed in myeloma cells with different ratios of expression. Interestingly, we found that CXCR3 expression in myeloma cell was cell cycle dependent and that myeloma growth factors inhibited CXCR3 expression in myeloma cells. On the other hand, we found that FAS (CD95)-mediated apoptosis up-regulated CXCR3 expression. A similar behavior was observed for the CXCR3-binding chemokines. Finally we found that the activation of CXCR3 on myeloma cells by CXCL10/IP-10 partially blunted FAS-mediated apoptosis in myeloma cells that express CXCR3-A and that high concentrations of CXCL10/IP-10 inhibit myeloma cell proliferation. INTERPRETATION AND CONCLUSIONS Our data indicate that myeloma cells express the CXCR3 system with patterns correlated to cell cycle and apoptosis and that CXCR3 activation may affect myeloma cell survival and proliferation.

Myeloma cells block RUNX2/CBFA1 activity in human bone marrow osteoblast progenitors and inhibit osteoblast formation and differentiation.

Decreased bone formation contributes to the development of bone lesions in multiple myeloma (MM) patients. In this study, we have investigated the effects of myeloma cells on osteoblast formation and differentiation and the potential role of the critical osteoblast transcription factor RUNX2/CBFA1 (Runt-related transcription factor 2/core-binding factor Runt domain alpha subunit 1) in the inhibition of osteoblastogenesis in MM. We found that human myeloma cells suppress the formation of human osteoblast progenitors in bone marrow (BM) cultures. Moreover, an inhibitory effect on osteocalcin, alkaline phosphatase, collagen I mRNA, protein expression, and RUNX2/CBFA1 activity by human preosteoblastic cells was observed in cocultures with myeloma cells. The inhibitory effect was more pronounced in the cell-to-cell contact conditions compared with those without the contact and involved the very late antigen 4 (VLA-4) integrin system. Among the soluble osteoblast inhibitors screened, we show the potential contribution of interleukin-7 (IL-7) in the inhibitory effect on osteoblast formation and RUNX2/CBFA1 activity by human myeloma cells in coculture. Finally, our in vitro results were supported in vivo by the finding of a significant reduction in the number of Runx2/Cbfa1-positive cells in the BM biopsies of patients with MM who had osteolytic lesions compared with those who did not have bone lesions, suggesting the critical involvement of RUNX2/CBFA1 in the decreased bone formation in MM.

IL-3 is a potential inhibitor of osteoblast differentiation in multiple myeloma.

Bone destruction in multiple myeloma is characterized both by markedly increased osteoclastic bone destruction and severely impaired osteoblast activity. We reported that interleukin-3 (IL-3) levels are increased in bone marrow plasma of myeloma patients compared with healthy controls and that IL-3 stimulates osteoclast formation. However, the effects of IL-3 on osteoblasts are unknown. Therefore, to determine if IL-3 inhibits osteoblast growth and differentiation, we treated primary mouse and human marrow stromal cells with IL-3 and assessed osteoblast differentiation. IL-3 inhibited basal and bone morphogenic protein-2 (BMP-2)-stimulated osteoblast formation in a dose-dependent manner without affecting cell growth. Importantly, marrow plasma from patients with high IL-3 levels inhibited osteoblast differentiation, which could be blocked by anti-IL-3. However, IL-3 did not inhibit osteoblast differentiation of osteoblastlike cell lines. In contrast, IL-3 increased the number of CD45+ hematopoietic cells in stromal-cell cultures. Depletion of the CD45+ cells abolished the inhibitory effects of IL-3 on osteoblasts, and reconstitution of the cultures with CD45+ cells restored the capacity of IL-3 to inhibit osteoblast differentiation. These data suggest that IL-3 plays a dual role in the bone destructive process in myeloma by both stimulating osteoclasts and indirectly inhibiting osteoblast formation.

Lack of receptor activator of nuclear factor-kB ligand (RANKL) expression and functional production by human multiple myeloma cells.

The direct expression and production of the critical osteoclastogenic factor, the receptor activator of NF-kB ligand (RANKL), is a matter of controversy. In this study we definitively demonstrate by both qualitative and quantitative polymerase chain reaction analysis that human myeloma cells do not express significant levels of RANKL mRNA or produce RANKL able to stimulate osteoclast formation.

Angiopoietin-1 and myeloma-induced angiogenesis.

Multiple myeloma (MM) is a plasma cell malignancy characterized by an increase of the bone marrow angiogenesis. Angiopoietin-1 (Ang-1) is a critical factor in the regulation of physiological and pathological vessel formation that acts by binding to a specific receptor Tie2 expressed on endothelial cells. Recent evidences indicate that human MM cells produce Ang-1 and up-regulate its receptor Tie2 in bone marrow endothelial cells. An overexpression of Ang-1 has been also found in MM cells as compared to normal plasma cells. The correlation between Ang-1 expression and BM angiogenesis, demonstrated in MM patients, and the inhibitory effect of Tie2 blocking on MM-induced vessel formation suggest that Ang-1 production by MM cells is critically involved in the angiogenic process in MM. In this review we focalize our attention on Ang-1/Tie2 system and its role in MM-induced angiogenesis.

The RANK/RANK ligand system is involved in interleukin-6 and interleukin-11 up-regulation by human myeloma cells in the bone marrow microenvironment.

BACKGROUND AND OBJECTIVES: The receptor activator of NF-kB ligand (RANKL) has a critical role in osteoclast activation. Recently it has been demonstrated that human multiple myeloma (MM) cells do not express RANKL but up-regulate RANKL in bone marrow stromal cells (BMSC). To further investigate the role of RANKL in the pathophysiology of MM we evaluated the expression of its receptor RANK in MM cells and in the BM environment and the potential role of RANKL in the interaction of myeloma cells with the microenvironment. DESIGN AND METHODS: RANK mRNA and protein expression were evaluated by reverse transcription polymerase chain reaction and Western blot analysis in human myeloma cell lines (HMCL), fresh purified MM cells, BMSC and endothelial cells. Moreover the effect and the role of RANKL on cytokine secretion were evaluated in BMSC, in endothelial cells and in co-culture conditions with myeloma cells. RESULTS: We found that RANK is expressed in BMSC and endothelial cells but not in myeloma cells. Consistently, RANKL did not have a direct effect on myeloma cell survival, but RANKL treatment induced a significant increase of interleukin (IL)-6 and IL-11 secretion by both BMSC and endothelial cells. Moreover, in a co-culture system we found that myeloma cells up-regulated both IL-6 and IL-11 secretion by BMSC and endothelial cells through cell-to-cell contact. The presence of the RANK-Fc that blocks the RANK/RANKL interaction significantly inhibited HMCL-induced secretion of IL-6 and IL-11. INTERPRETATION AND CONCLUSIONS: Our data provide new notions on the role of the RANKL system in the pathophysiology of MM.

Co-existence of Philadelphia chromosome positive acute megakaryoblastic and B-lymphoblastic mixed blast crisis of chronic myeloid leukemia with chronic lymphocytic leukemia.

In this study, we describe an extremely rare case of co-existence of a Philadelphia chromosome positive acute megakaryoblastic and B-lymphoblastic mixed blast crisis of chronic myeloid leukemia with chronic lymphocytic leukemia. A morphological, immunophenotypical and cytogenetic study has been performed to characterize the case and in order to identify the origin of two disorders. After the failure of the conventional therapy, the patient was treated with Imatinib with a complete hematological and cytogenetic response and a marked reduction of bone marrow fibrosis.

Role of implantable cardioverter defibrillators in dilated cardiomyopathy.

Idiopathic dilated cardiomyopathy (DCM) accounts for about 10,000 deaths per year in western countries. Of these deaths, 8% to 51% occur suddenly, with more than half of the events due to a ventricular arrhythmia. Improvement in diagnostic techniques and therapeutic strategies, together with changes in secular trends, have likely contributed to the reported trend toward improved survival in recent years. Identification of DCM patients at higher risk of sudden death is difficult. Poor left ventricular function is the strongest predictor of all-cause death, whereas a history of sustained unstable ventricular arrhythmia or cardiac arrest identifies patients at high risk of sudden death. Recent data suggest that a history of syncope, regardless of inducibility at programmed electrical stimulation, may be a risk factor of sudden death. Despite the absence of controlled studies, use of implantable cardioverter defibrillator therapy for primary prevention can be considered in patients with unexplained syncope as well as subgroups of DCM patients awaiting transplantation. In patients who survive a cardiac arrest or an unstable ventricular tachycardia, use of implantable cardioverter defibrillator therapy is associated with improved survival during follow-up and should be considered as a first-line therapy.