The proteasome inhibitor bortezomib stimulates osteoblastic differentiation of human osteoblast precursors via upregulation of vitamin D receptor signalling.

Interactions of myeloma cells with the bone marrow microenvironment lead to enhanced osteoclast recruitment and impaired osteoblast activity. Recent evidence revealed that the proteasome inhibitor bortezomib stimulates osteoblast differentiation, but the mechanisms are not fully elucidated. We hypothesised that bortezomib could influence osteoblastic differentiation via alteration of vitamin D signalling by blocking the proteasomal degradation of the vitamin D receptor (VDR). This is of clinical importance, as a high rate of vitamin D deficiency was reported in patients with myeloma. We performed cocultures of primary human mesenchymal stem cells (hMSCs) and human osteoblasts (hOBs) with myeloma cells, which resulted in an inhibition of the vitamin D-dependent differentiation of osteoblast precursors. Treatment with bortezomib led to a moderate increase in osteoblastic differentiation markers in hMSCs and hOBs. Importantly, this effect could be strikingly increased when vitamin D was added. Bortezomib led to enhanced nuclear VDR protein levels in hMSCs. Primary hMSCs transfected with a VDR luciferase reporter construct showed a strong increase in VDR signalling with bortezomib. In summary, stimulation of VDR signalling is a mechanism for the bortezomib-induced stimulation of osteoblastic differentiation. The data suggest that supplementation of vitamin D in patients with myeloma treated with bortezomib is crucial for optimal bone formation.

The novel, orally bioavailable HSP90 inhibitor NVP-HSP990 induces cell cycle arrest and apoptosis in multiple myeloma cells and acts synergistically with melphalan by increased cleavage of caspases.

Heat shock protein 90 (HSP90) binds and stabilizes numerous proteins and kinases essential for myeloma cell survival and proliferation. We and others have recently demonstrated that inhibition of HSP90 by small molecular mass inhibitors induces cell death in multiple myeloma (MM). However, some of the HSP90 inhibitors involved in early clinical trials have shown limited antitumor activity and unfavorable toxicity profiles. Here, we analyzed the effects of the novel, orally bioavailable HSP90 inhibitor NVP-HSP990 on MM cell proliferation and survival. The inhibitor led to a significant reduction in myeloma cell viability and induced G2 cell cycle arrest, degradation of caspase-8 and caspase-3, and induction of apoptosis. Inhibition of the HSP90 ATPase activity was accompanied by the degradation of MM phospho-Akt and phospho-ERK1/2 and upregulation of Hsp70. Exposure of MM cells to a combination of NVP-HSP990 and either melphalan or histone deacetylase (HDAC) inhibitors caused synergistic inhibition of viability, increased induction of apoptosis, and was able to overcome the primary resistance of the cell line RPMI-8226 to HSP90 inhibition. Combined incubation with melphalan and NVP-HSP990 led to synergistically increased cleavage of caspase-2, caspase-9, and caspase-3. These data demonstrate promising activity for NVP-HSP990 as single agent or combination treatment in MM and provide a rationale for clinical trials.

Decrease in CD4+ T-cell counts in patients with multiple myeloma treated with bortezomib.

BACKGROUND: Bortezomib is highly effective in multiple myeloma and is widely used in this disease. Recently, an increased incidence of varicella zoster virus (VZV) reactivation was reported in patients with myeloma undergoing bortezomib treatment. PATIENTS AND METHODS: We investigated the influence of bortezomib on T-cell subpopulations in 53 patients with myeloma before initiation of bortezomib and during therapy. RESULTS: A decrease of CD4+ T cells was seen in 41 of 53 patients (77%). The median CD3+/CD4+ lymphocyte counts declined from 494/microL (range, 130-2187/microL) to 274/microL (range, 41-1404/microL) during bortezomib treatment (P < .001). In the majority of patients (40 of 53 patients, 75%), CD4+ lymphocytes dropped to < 400/microL during bortezomib treatment, and in 18 of 53 patients (33.9%) the CD4+ T cells fell below 200/microL. The minimum CD4S+ cell count was observed at a median of 6 weeks (range, 2-22 weeks) after initiation of treatment. The incidence of herpes zoster reactivation was 5.7% in the whole population of patients with myeloma receiving bortezomib. Nineteen of 53 patients received acyclovir at a dose of 400 mg daily as prophylaxis against VZV reactivation. In this group, none of the patients developed herpes zoster. The incidence of VZV reactivation in patients not receiving acyclovir was 3 of 34 (8.8%). Importantly, occurrence of herpes zoster was associated with reduced CD4+ T-cell subpopulation: all patients who developed herpes zoster had CD4+ lymphocytes < 400/microL. CONCLUSION: Our results show that bortezomib leads to a transient decrease in CD4+ lymphocytes, accompanied by an increased incidence of VZV infections. The antiviral prophylaxis with acyclovir is effective in patients with myeloma treated with bortezomib.

BSc2118 is a novel proteasome inhibitor with activity against multiple myeloma.

OBJECTIVES: The ubiquitin-proteasome system emerged as a new therapeutic target in cancer treatment. The purpose of this study was to elucidate the effects of the novel proteasome inhibitor BSc2118 on t(4;14) positive and negative multiple myeloma (MM) cells and normal peripheral blood mononuclear cells (PBMNC). METHODS: Human MM cell lines OPM-2, RPMI-8226, and U266 and primary MM cells from bone marrow aspirates were exposed to BSc2118. Cytotoxicity levels were evaluated using the MTT-test. BSc2118-induced apoptosis was analyzed by annexin-V assay. Further methods used included proteasomal activity determination, cell cycle analysis, western blot, and transcription factor assays. RESULTS: In OPM-2, RPMI-8226, U266 cell lines and primary MM cells, BSc2118 caused dose-dependent growth inhibitory effects. After 48 h, dose-dependent apoptosis occurred both in cell lines and primary myeloma cells irrespective of t(4;14). A significant G2-M cell cycle arrest occurred after 24 h. Furthermore, we observed a marked inhibition of intracellular proteasome activity, an increase in intracellular p21 levels, and an inhibition of NF-kappaB activation. The toxicity against PBMNC remained low, suggesting a broad therapeutic range of this agent. CONCLUSION: Taken together, BSc2118 shows significant antimyeloma activity and may be considered as a promising agent in cancer drug development.

Synergistic action of the novel HSP90 inhibitor NVP-AUY922 with histone deacetylase inhibitors, melphalan, or doxorubicin in multiple myeloma.

Heat shock protein 90 (HSP90) is a promising target for tumor therapy. The novel HSP90 inhibitor NVP-AUY922 has preclinical activity in multiple myeloma, however, little is known about effective combination partners to design clinical studies. Multiple myeloma cell lines, OPM-2, RPMI-8226, U-266, LP-1, MM1.S, and primary myeloma cells were exposed to NVP-AUY922 and one of the combination partners histone deacetylase inhibitor NVP-LBH589, suberoylanilide hydroxamic acid (SAHA), melphalan, or doxorubicin, either simultaneously or in sequential patterns. Effects on cell proliferation and apoptosis were determined. Synergistic effects were evaluated using the method of Chou and Talalay. Combined sequential incubation with NVP-AUY922 and SAHA showed that best synergistic effects were achieved with 24 h preincubation with SAHA followed by another 48 h of combination treatment. Combination of NVP-AUY922 with SAHA, NVP-LBH589, melphalan, or doxorubicin resulted in synergistic inhibition of viability, with strong synergy (combination index < 0.3) in the case of melphalan. Importantly, resistance of the RPMI-8226 cell line and relative resistance of some primary myeloma cells against NVP-AUY922 could be overcome by combination treatment. These data show impressive synergistic action of the novel HSP90 inhibitor NVP-AUY922 with melphalan, doxorubicin, NVP-LBH589, and SAHA in multiple myeloma and build the frame work for clinical trials.

Serum levels of total-RANKL in multiple myeloma.

BACKGROUND: Receptor activator of nuclear factor-kappaB ligand (RANKL) plays a key role in osteoclast activation in myeloma bone disease. The increased expression of RANKL in the bone marrow microenvironment was demonstrated in several studies, but there are only rare data on circulating RANKL levels in patients with multiple myeloma (MM). PATIENTS AND METHODS: In the current study, we investigated the clinical significance of serum RANKL levels, using an enzyme-linked immunosorbent assay test that detects both free and osteoprotegerin (OPG)-bound RANKL (total-RANKL, tRANKL) in patients with newly diagnosed MM (n = 93) and monoclonal gammopathy of undetermined significance (MGUS; n = 20) compared with healthy controls (n = 20). RESULTS: Circulating serum tRANKL was significantly elevated in patients with MM compared with controls (P < .001) or MGUS (P < .001). Furthermore, tRANKL levels were higher in smoldering MM versus MGUS (P = .031) and in symptomatic versus smoldering MM (P < .001). Serum tRANKL increased parallel to International Staging System stages I to III (P = .004) and correlated with the presence of lytic bone lesions (P < .001). Total-RANKL was a prognostic factor for overall survival in symptomatic MM (P = .043). A significantly longer progression-free survival was observed in patients with a > 50% decrease in tRANKL levels after 3 months of combined chemotherapy and bisphosphonate treatment. CONCLUSION: Our study demonstrates for the first time that serum tRANKL reflects advanced disease, lytic bone destruction, and poor prognosis in MM.

Synergistic interaction of proteasome and topoisomerase II inhibition in multiple myeloma.

Multiple myeloma is a malignancy of terminally differentiated plasma cells and is incurable in the majority of the patients. Thus, novel effective treatment regimens are urgently needed. In this study, we examined the effects of co-treatment with proteasome-inhibitor bortezomib and topoisomerase II inhibitor etoposide in multiple myeloma cells lines OPM-2, RPMI-S and NCI-H929. Using the median effect method of Chou and Talalay, we evaluated the combination indices (CI) for simultaneous and sequential treatment schedules. In the sequential treatment schedule, we found strong synergistic effects in all three cell lines, even at low single-agent cytotoxicity levels. When cells were treated simultaneously with both drugs, the synergy was present but less pronounced than in the sequential treatment schedule. The synergistic effects observed in the co-treatment schedules were accompanied by an inhibition of anti-apoptotic effects that were induced by etoposide alone. Namely, bortezomib abrogated both etoposide-induced NF-kappaB activation and etoposide-induced bcl-2 up-regulation. Our data suggest that combining etoposide with bortezomib might be useful for cancer treatment, as bortezomib potentially inhibits counter-regulatory mechanisms of tumor cells, which are induced by topoisomerase II inhibition and which may contribute to acquired chemoresistance.

Therapeutic implication of BAL in patients with neutropenia.

Bronchoalveolar lavage (BAL) is a practicable procedure establishing the etiology of pneumonia. In patients with neutropenia, empirical antimicrobial treatment is mandatory immediately after diagnosis of infection, usually before results of BAL are available. We evaluated the impact of BAL on treatment and outcome of pneumonia in immunocompromised patients with a special regard to neutropenia. Bronchoscopy with BAL was performed in 58 episodes of clinical documented pneumonia in patients with hematological malignancies (88%) or solid tumors (12%), in 30 cases patients had neutropenia, in 28 cases patients had no neutropenia. In 93% of cases, BAL was performed under empirical antimicrobial treatment. BAL fluid was cultivated for bacteria, fungi, and tested for Pneumocystis jirovecii and cytomegalovirus (CMV). BAL revealed positive bacterial results in 67% of cases. Gram-positive microorganisms were detected in 95% of positive BAL results, gram-negative microorganisms in 23%, mixed bacterial cultures occurred in 41%. Positive fungi cultures were found in 59%. P. jirovecii was detected in 5% of cases tested and CMV in 8%. There was no significant difference between neutropenic and non-neutropenic patients. BAL results directed a change of therapy in only six of 58 episodes (5%). Overall mortality related to pneumonia was 16%. In this patient setting, the yield of BAL rarely has a significant influence on treatment and outcome of pneumonia. The early beginning of antimicrobial treatment reduces the diagnostic yield of BAL. In patients with pneumonia during neutropenia, its use should be well considered.

Synergistic interaction of the histone deacetylase inhibitor SAHA with the proteasome inhibitor bortezomib in cutaneous T cell lymphoma.

Proteasome inhibitors and histone deacetylase (HDAC) inhibitors are novel targeted therapies being evaluated in clinical trials for cutaneous T-cell lymphoma (CTCL). However, data in regard to tumor biology are limited with these agents. In the present study we analyzed the effects of the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and the proteasome inhibitor bortezomib on human CTCL cells. Four CTCL cell lines (SeAx, Hut-78, MyLa, and HH) were exposed to bortezomib and/ or SAHA at different concentrations. Cell viability was quantified using the MTT assay. In addition, apoptosis and generation of reactive oxygen species were analyzed. Both agents potently inhibited cell viability and induced apoptosis. After 48 h of incubation, IC50 of bortezomib was noted at 8.3 nm, 7.9 nm, 6.3 nm, and 22.5 nm in SeAx, Hut-78, HH, and MyLa cells, respectively. For SAHA, the IC50 values were at 0.6 microm in SeAx cells, 0.75 microm in Hut-78 cells, 0.9 microm in HH cells, and 4.4 microm in MyLa cells. Importantly, combined treatment resulted in synergistic cytotoxic effects, as indicated by Combination indices values <1 using the median effect method of Chou and Talalay. We furthermore found that combined treatment with both agents lead to a decreased proteasome activity, an upregulation of the cell regulators p21 and p27 and increased expression of phosphorylated p38. In addition, we showed that SAHA reduced the vascular endothelial growth factor production of CTCL cells. Our results demonstrate that bortezomib and SAHA synergistically induce apoptosis in CTCL cells and thus provide a rationale for clinical trials of combined proteasome and histone deacetylase inhibition in the treatment of CTCL.

Serum concentrations of DKK-1 decrease in patients with multiple myeloma responding to anti-myeloma treatment.

Lytic bone destruction is a hallmark of multiple myeloma (MM) and is because of an uncoupling of bone remodeling. Secretion of Dickkopf (DKK)-1 by myeloma cells is a major factor which causes inhibition of osteoblast precursors. In this study, the effect of different treatment regimens for MM on serum DKK-1 was evaluated and correlated with the response to treatment in 101 myeloma patients receiving bortezomib, thalidomide, lenalidomide, adriamycin and dexamethasone (AD) or high-dose chemotherapy (HDCT) followed by autologous stem cell transplantation (ASCT). At baseline, myeloma patients had increased serum DKK-1 as compared with patients with MGUS (mean 3786 pg/mL vs. 1993 pg/mL). There was no difference between previously untreated MM patients and patients at relapse. A significant decrease of DKK-1 after therapy was seen in the following groups: Bortezomib (4059 pg/mL vs. 1862 pg/mL, P = 0.016), lenalidomide (11837 pg/mL vs. 4374 pg/mL, P = 0.039), AD (1668 pg/mL vs. 1241 pg/mL, P = 0.016), and AD + HDCT + ASCT (2446 pg/mL vs. 1082 pg/mL, P = 0.001). Thalidomide led to a non-significant decrease in DKK-1 (1705 pg/mL vs. 1269 pg/mL, P = 0.081). Within all groups, a significant decrease of DKK-1 was only seen in responders (i.e. patients achieving complete remission or partial remission), but not in non-responders. We show for the first time that serum DKK-1 levels decrease in myeloma patients responding to treatment, irrespective of the regimen chosen. These data suggest that myeloma cells are the main source of circulating DKK-1 protein and provide a framework for clinical trials on anti-DKK-1 treatment in MM.

Curcumin diminishes human osteoclastogenesis by inhibition of the signalosome-associated I kappaB kinase.

PURPOSE: Curcumin is a natural polyphenolic derogate extracted from spice turmeric, exhibiting anti-inflammatory and chemopreventive activities. It was described to interact with the signalosome-associated kinases and the proteasome-ubiquitin system, which both are involved in the osteoclastogenesis. Thus, we hypothesized that curcumin could diminish osteoclast differentiation and function. METHODS: For the experiments considering osteoclast differentiation and resorptional activities, preosteoclasts were cultured for 4 weeks and treated with curcumin at subapoptotic dosages. Derived mature osteoclasts were identified as large, multinucleated cells with expression of tartrate-resistant acid phosphatase activity. Formation of resorption lacunae, a hallmark of osteoclast activity, was quantified using dentine pits and light microscopy. The signaling pathways were examined by ELISA-based methods and by immunoblotting. RESULTS: Both 1 and 10 microM curcumin abrogated osteoclast differentiation (by 56 and 81%) and function (by 56 and 99%) (P < 0.05) dose-dependently. The effects were accompanied by the inhibition of I kappaB phosphorylation and NF-kappaB activation. In contrast, subtoxic doses did not have any significant effects on proteasome inhibition. CONCLUSION: This manuscript is the first report that describes the effects of curcumin toward human osteoclastogenesis, and builds the framework for clinical trials of curcumin in the treatment of cancer-induced lytic bone disease.

The potential of proteasome inhibitors in cancer therapy.

BACKGROUND: The ubiquitin-proteasome system has become a promising novel molecular target in cancer due to its critical role in cellular protein degradation, its interaction with cell cycle and apoptosis regulation and its unique mechanism of action. OBJECTIVE: This review focuses both on preclinical results and on data from clinical trials with proteasome inhibitors in cancer. METHODS: Results in hematological malignancies and solid tumors were included, and important data presented in abstract form were considered in this review. RESULTS/CONCLUSION: Bortezomib as first-in-class proteasome inhibitor has proven to be highly effective in some hematological malignancies, overcomes conventional chemoresistance, directly induces cell cycle arrest and apoptosis, and also targets the tumor microenvironment. It has been granted approval by the FDA for relapsed multiple myeloma, and recently for relapsed mantle cell lymphoma. Combination chemotherapy regimens have been developed providing high remission rates and remission quality in frontline treatment or in the relapsed setting in multiple myeloma. The combination of proteasome inhibition with novel targeted therapies is an emerging field in oncology. Moreover, novel proteasome inhibitors, such as NPI-0052 and carfilzomib, have been developed. This review summarizes our knowledge of the ubiquitin-proteasome system and recent data from cancer clinical trials.

Serum concentrations of DKK-1 correlate with the extent of bone disease in patients with multiple myeloma.

OBJECTIVES: Lytic bone disease is a hallmark of multiple myeloma (MM) and is caused by osteoclast activation and osteoblast inhibition. Secretion of Dickkopf (DKK)-1 by myeloma cells is a major factor which causes inhibition of osteoblast precursors. So far, there is no study showing a significant difference in serum DKK-1 levels in MM patients with or without lytic bone lesions. METHODS: DKK-1 serum levels were quantified in 184 untreated MM patients and 33 monoclonal gammopathy of undetermined significance (MGUS) patients by ELISA, using a monoclonal anti-DKK-1 antibody. RESULTS: Serum DKK-1 was elevated in MM as compared with MGUS (mean 11 963 pg/mL vs. 1993 pg/mL; P < 0.05). Serum DKK-1 levels significantly correlated with myeloma stage according to Durie and Salmon (mean 2223 pg/mL vs. 15 209 pg/mL in stage I and II/III, respectively; P = 0.005). Importantly, myeloma patients without lytic lesions in conventional radiography had significantly lower DKK-1 levels than patients with lytic bone disease (mean 3114 pg/mL vs. 17 915 pg/mL; P = 0.003). Of interest, serum DKK-1 correlated with the number of bone lesions (0 vs. 1-3 vs. >3 lesions: 3114 pg/mL vs. 3559 pg/mL vs. 24 068 pg/mL; P = 0.002). CONCLUSION: Using a large series of myeloma patients, we could show for the first time a correlation between DKK-1 serum concentration and the amount of lytic bone disease, indicating that DKK-1 is an important factor for the extent of bone disease and supporting the hypothesis of DKK-1 as a therapeutic target in myeloma bone disease.

Synergistic interaction of the histone deacetylase inhibitor SAHA with the proteasome inhibitor bortezomib in mantle cell lymphoma.

OBJECTIVES: Mantle cell lymphoma (MCL) is an incurable B cell lymphoma, and novel treatment strategies are urgently needed. We evaluated the effects of combined treatment with the proteasome inhibitor bortezomib and the histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA) on MCL. Bortezomib acts by targeting the proteasome, and--among other mechanisms--results in a reduced nuclear factor-kappa B (NF-kappaB) activity. HDACi promote histone acetylation, and also interfere with NF-kappaB signaling. METHODS: Human MCL cell lines (JeKo-1, Granta-519 and Hbl-2) were exposed to bortezomib and/or SAHA. Cell viability and apoptosis were quantified by the MTT and annexin-V assay, respectively. Reactive oxygen species (ROS) were analyzed using the fluorophore H2DCFDA. In addition, activated caspases, proteasome- and NF-kappaB activity were quantified. RESULTS: Combined incubation with bortezomib and SAHA resulted in synergistic cytotoxic effects, as indicated by combination index values <1 using the median effect method of Chou and Talalay. The combination of both inhibitors led to a strong increase in apoptosis as compared to single agents and was accompanied by enhanced ROS generation, while each agent alone only modestly induced ROS. The free radical scavenger N-acetyl-L-cysteine blocked the ROS generation and reduced the apoptosis significantly. In addition, coexposure of bortezomib and SAHA led to increased caspase-3, -8 and -9 activity, marked reduction of proteasome activity and decrease of NF-kappaB activity. CONCLUSIONS: This is the first report giving evidence that SAHA and bortezomib synergistically induce apoptosis in MCL cells. These data build the framework for clinical trials using combined proteasome and histone deacetylase inhibition in the treatment of MCL.

Molecular and clinical aspects of proteasome inhibition in the treatment of cancer.

The proteasome is a multicatalytic threonine protease responsible for intracellular protein turnover in eukaryotic cells, including the processing and degradation of several proteins involved in cell cycle control and the regulation of apoptosis. Preclinical studies have shown that the treatment with proteasome inhibitors results in decreased proliferation, induction of apoptosis, and sensitization of tumor cells against conventional chemotherapeutic agents and irradiation. The effects were conferred to stabilization of p21, p27, Bax, p53, I-KB, and the resulting inhibition of the nuclear factor-KB (NF-KB) activation. Bortezomib is the first proteasome inhibitor that has entered clinical trials. In multiple myeloma, both the FDA (United States Food and Drug Administration) and EMEA (European Medicine Evaluation Agency) granted an approval for the use of bortezomib (Velcade, Millennium Pharmaceuticals, Cambridge, MA, USA) for the treatment of relapsed multiple myeloma. At present, clinical trials are examining the activity in a variety of solid tumors and hematological malignancies.

Osteoblasts promote migration and invasion of myeloma cells through upregulation of matrix metalloproteinases, urokinase plasminogen activator, hepatocyte growth factor and activation of p38 MAPK.

Formation of osteolytic lesions is a key pathophysiological feature in multiple myeloma and results from the interaction of myeloma cells with the bone marrow microenvironment. Matrix metalloproteinases (MMPs) and plasmin may be involved in bone destruction, but their precise roles have not been clarified. Furthermore, the impact of osteoblast-related alterations on myeloma bone disease is not well understood. We addressed this complex phenomenon by applying a coculture system between myeloma cells and osteoblasts. Osteoblasts induced expression of MMP-1 and upregulated the expression of MMP-2, urokinase plasminogen activator (uPA) and hepatocyte growth factor (HGF) in myeloma cells. In turn, interaction with myeloma cells led to abundant MMP-1 expression in osteoblasts. Because MMP-1 degrades collagen, its upregulation might represent an essential mechanism contributing to bone destruction. Cocultures using primary myeloma cells confirmed the results obtained with cell lines. The mechanisms responsible for MMP-1 upregulation are mediated by both membrane-bound and soluble factors, and involve the p38 mitogen-activated protein kinase (MAPK) pathway. The interaction with osteoblasts enhances the capability of myeloma cells to transmigrate and invade through Matrigel or type I collagen. Using appropriate inhibitors, we provide evidence that these processes involve MMPs, uPA, HGF and activation of p38 MAPK.

Genetic polymorphisms in the amino acid transporters LAT1 and LAT2 in relation to the pharmacokinetics and side effects of melphalan.

OBJECTIVES: Melphalan is widely used in the treatment of multiple myeloma. Pharmacokinetics of this alkylating drug shows high inter-individual variability. As melphalan is a phenylalanine derivative, the pharmacokinetic variability may be determined by genetic polymorphisms in the L-type amino acid transporters LAT1 (SLC7A5) and LAT2 (SLC7A8). METHODS: Pharmacokinetics were analysed in 64 patients after first administration of intravenous melphalan. Severity of side effects was documented according to WHO criteria. Genomic DNA was analysed for polymorphisms in LAT1 and LAT2 by sequencing of the entire coding region, intron-exon boundaries and 2 kb upstream promoter region. Selected polymorphisms in the common heavy chain of both transporters, the protein 4F2hc (SLC3A2), were analysed by single nucleotide primer extension. RESULTS: Melphalan pharmacokinetics was highly variable with up to 6.2-fold differences in total clearance. A total of 44 polymorphisms were identified in LAT1 and 21 polymorphisms in LAT2. From all variants, only five were in the coding region and only one heterozygous non-synonymous polymorphism (Ala94Thr) was found in LAT2. Numerous polymorphisms were found in the LAT1 and LAT2 5'-flanking regions but did not correlate with expression of the respective genes. No significant correlations could be observed between the polymorphisms in 4F2hc, LAT1, and LAT2 with melphalan pharmacokinetics or with melphalan side effects. CONCLUSIONS: The study confirmed that these transporter genes are highly conserved, particularly in the coding sequences. Genetic variation in 4F2hc, LAT1, and LAT2 does not appear to be a major cause of inter-individual variability in pharmacokinetics and of adverse reactions to melphalan.

Circulating proteasome levels are an independent prognostic factor for survival in multiple myeloma.

The proteasome is a proteolytic complex for intracellular degradation of ubiquitinated proteins which are involved in cell-cycle regulation and apoptosis. A constitutively increased proteasome activity has been found in myeloma cells. We studied circulating proteasome levels and their prognostic significance in sera of 50 control subjects, 20 persons with monoclonal gammopathies of undetermined significance (MGUS), and 141 previously untreated patients with multiple myeloma (MM) by an anti-20S proteasome enzyme-linked immunoabsorbent assay (ELISA). Serum proteasome concentrations were significantly elevated in MM compared with controls (P < .001), in MM versus MGUS (P = .03), and in active (n = 101) versus smoldering (n = 40) MM (P < .001). In patients with active MM, there was a significant (P < .001) decrease from pretreatment to post-treatment proteasome concentrations in responders to chemotherapy, but not in nonresponders. Circulating proteasome levels were identified as a prognostic factor for overall survival in the univariate (P < .001 log-rank test) and in the multivariate (hazard ratio, 4.38) survival analysis in patients with active MM. We demonstrate for the first time that increased serum proteasome concentrations correlate with advanced disease and are an independent prognostic factor in MM.

Peroxisome proliferator-activated receptor-gamma ligands inhibit proliferation and induce apoptosis in mantle cell lymphoma.

Peroxisome proliferator-activated receptor-gamma, a nuclear receptor and transcription factor, and its natural and synthetic ligands have become a focus of novel approaches to induction of apoptosis in solid tumors and hematologic malignancies, including malignant B-lineage cells. The effect on mantle cell lymphoma, a subtype with dismal prognosis, has not yet been analyzed. We investigated the effect of 15-deoxy-delta-12,14-prostaglandin J2 (15d-PGJ2), pioglitazone (PGZ) or rosiglitazone (RGZ) on human mantle cell lymphoma cell lines (GRANTA-519, Hbl-2 and JeKo-1). Mantle cell lymphoma cell lines exhibited a high expression of Peroxisome proliferator-activated receptor-gamma protein in Western blot analysis. MTT assays revealed anti-proliferative effects induced by both 15d-PGJ2, the natural activator of Peroxisome proliferator-activated receptor-gamma, and PGZ and RGZ, synthetic Peroxisome proliferator-activated receptor-gamma ligands, in a dose-dependent manner. At a dose of 50 micromol/l, 15d-PGJ2 induced growth inhibition in all cell lines. The anti-proliferative effect of PGZ and RGZ was slightly lower. Induction of apoptosis was indicated by annexin V staining. At a dose of 50 micromol/l, 15d-PGJ2 led to apoptosis in all cell lines (87-99%) after 48 h of incubation. Again, the apoptotic effect with thiazolidinediones was slightly lower at the same dose level. This is the first study evaluating Peroxisome proliferator-activated receptor-gamma expression and its therapeutic implications in human mantle cell lymphoma cells. Thiazolidinediones comprise anti-lymphoma activity in vitro and should be further explored for the treatment of mantle cell lymphoma.

Bortezomib increases osteoblast activity in myeloma patients irrespective of response to treatment.

OBJECTIVES: Myeloma bone disease is a result of excessive osteoclast activation and impaired osteoblast function. Recent in vitro studies suggested that proteasome inhibitors might increase osteoblast function. METHODS: We analyzed serum markers of osteoblast activity in 25 patients with multiple myeloma receiving bortezomib alone or in combination with dexamethasone. As control, serum samples from 58 consecutive myeloma patients receiving a therapy different than bortezomib (i.e. adriamycin/dexamethasone, melphalan/prednisone or thalidomide) were evaluated. The serum concentrations of bone-specific alkaline phosphatase (BAP) and osteocalcin were quantified before initiation of treatment and after 3 months. RESULTS: In patients treated with bortezomib, mean serum levels of osteocalcin significantly increased from 6.3 to 10.8 microg/L (P = 0.024), while mean BAP levels increased from 19.7 to 30.2 U/L (P < 0.0005). Of interest, the increase in BAP was significant both in responders and non-responders. In contrast, the control group did not show a statistically significant change in BAP (24.8 U/L vs. 23.3 U/L) and osteocalcin (6.8 microg/L vs. 6.5 microg/L) before and after the treatment. CONCLUSION: These data show that treatment with bortezomib leads to enhanced markers of osteoblast activity in patients with myeloma. The comparison with the control group suggests that the effect on osteoblasts is unique to the proteasome inhibitor.