PubMed Health⌕ Search

Biomedical subjects

Orhan Sezer

Publications and source records attributed to Orhan Sezer.

At least 19 recordsLinked to original sources
PubMed2006

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.

Female↗
PubMed2006

Angiogenesis in multiple myeloma.

Multiple myeloma (MM) was the first haematological malignancy in which a prognostic relevance of bone marrow microvessel density (MVD) was shown. Myeloma-induced angiogenesis involves either the direct production of angiogenic molecules by myeloma cells or their induction in bone marrow stromal cells or endothelial cells (EC). Recent data demonstrate an increased angiogenic potential and a paracrine stimulatory effect of bone marrow EC on plasma cells (PC) in MM. Soluble angiogenic factors are elevated in bone marrow (BM) and in peripheral blood samples from myeloma patients. Furthermore, correlation with disease stage and prognosis was shown for serum levels of the angiogenic factors basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF). In this review we summarize recent data which give strong evidence for an increased angiogenic activity in bone marrow microenvironment and support the hypothesis that angiogenesis is not only an epiphenomenon of tumour growth but may also promote PC growth in MM.

Angiogenic Proteins↗
PubMed2006

Bone markers in multiple myeloma.

Bone disease, a hallmark of multiple myeloma occurs in the majority of the patients, is associated with bone pain, fractures, hypercalcemia and has major impacts on quality of life. Myeloma is characterized by a unique form of bone disease with osteolytic bone destruction that is not followed by reactive bone formation, resulting in extensive lytic lesions. This review will focus on the pathophysiology of osteoclast activation and osteoblast inhibition in multiple myeloma and on biochemical markers of bone turnover. Since osteolytic lesions do not rapidly heal in myeloma, X-rays cannot reflect the activity of bone disease during antimyeloma treatment. Activity in bone turnover does not parallel changes in monoclonal protein levels. Thus, there is a need for biochemical markers reflecting disease activity in bone. The utility, prognostic implications and limitations of classical and novel markers of bone remodeling (e.g. ICTP, NTx, TRACP-5b, osteoprotegerin, sRANKL) will be discussed in this overview.

Biomarkers↗
PubMed2006

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.

Annexin A5↗
PubMed2006

Histone deacetylase inhibitors reduce VEGF production and induce growth suppression and apoptosis in human mantle cell lymphoma.

OBJECTIVES: Mantle cell lymphoma (MCL) is an incurable disease with an aggressive course and novel treatment strategies are urgently needed. The purpose of this study was to evaluate the effects of histone deacetylase (HDAC) inhibitors, a new group of antiproliferative agents, on human MCL cells. METHODS: Three MCL cell lines (JeKo-1, Hbl-2 and Granta-519) were exposed to different concentrations of the HDAC inhibitors sodium butyrate (NaB) and suberoylanilide hydroxamic acid (SAHA) for 8-72 h. Their effects on cell viability, apoptosis induction and cell cycle proliferation were studied. Moreover, the influence of SAHA on the expression of cyclin D1, the cell cycle regulators p21 and p27 and the production of vascular endothelial growth factor (VEGF) were analyzed. RESULTS: The HDAC inhibitors induced accumulation of acetylated histones in MCL cells. MTT assays and Annexin-V staining showed that they potently inhibited viability in a dose-dependent manner and induced apoptosis in all cell lines tested. Cell cycle analysis indicated that their exposure to SAHA or NaB decreased the proportion of cells in S phase and increased the proportion of cells in the G0/G1 and/or G2/M phases. Incubation with the two HDAC inhibitors resulted in downregulation of cyclin D1. SAHA lead to an upregulation of p21 in all cell lines and an upregulation of p27 in JeKo-1 and Granta-519 cells, while expression of p27 in Hbl-2 was not altered. In addition, SAHA inhibited the production of the angiogenic cytokine VEGF. Treatment with NaB increased the expression of p21 in JeKo-1 and Hbl-2 cells, while in Granta 519 cells no effect was noted. The expression of p27 remained constant in all three cell lines after exposure to NaB. CONCLUSION: Based on these findings, we provide evidence that HDAC inhibitors have antiproliferative effects in MCL and may represent a promising therapeutic approach.

Apoptosis↗
PubMed2006

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.

Adult↗
PubMed2006

Bortezomib-induced tumor lysis syndrome in multiple myeloma.

Tumor lysis syndrome (TLS) is exceedingly rare in multiple myeloma because of the relatively slow proliferation and response of the malignant cells. Bortezomib is a novel agent that inhibits proteasome and has shown activity against multiple myeloma. We report 8 episodes of TLS seen in 7 patients with bortezomib therapy, with or without dexamethasone, among 496 patients treated on 3 phase II multicenter studies. Biochemical abnormalities resolved with supportive therapy in 6 patients (including hemodialysis in 2) but proved fatal in 1. Clinicians should be alert for TLS in patients with myeloma with significant disease burden treated with bortezomib because of the potential for rapid onset of cell lysis with this agent.

Antineoplastic Agents↗
PubMed2006

The effects of the histone deacetylase inhibitor valproic acid on cell cycle, growth suppression and apoptosis in multiple myeloma.

The aim of this study was to evaluate the effects of valproic acid (VPA), as a histone deacetylase inhibitor, on myeloma cell lines and on sorted human bone marrow multiple myeloma cells. VPA induced accumulation of acetylated histones, potently inhibited proliferation in a dose-dependent manner and induced apoptosis in all myeloma cell lines tested as well as in sorted primary multiple myeloma cells. Cell cycle analysis indicated an arrest in G0/1 phase in response to VPA. Accumulation of p21 and reduced levels of cyclin D1 were detected. The production of vascular endothelial growth factor was significantly inhibited by VPA. These results provide the framework for clinical trials.

Apoptosis↗
PubMed2005

Gemcitabine as prolonged infusion and vinorelbine in anthracycline and/or taxane pretreated metastatic breast cancer: a phase II study.

BACKGROUND: Gemcitabine and vinorelbine are active agents for the treatment of metastatic breast cancer. Prolonged infusion of gemcitabine can result in higher levels of active metabolites compared to shorter administration. This phase II trial was initiated to evaluate the efficacy and tolerability of gemcitabine as prolonged infusion in combination with vinorelbine in anthracycline and/or taxane pretreated patients with metastatic breast cancer. PATIENTS AND METHODS: Patients who had received one prior line of chemotherapy for metastatic disease were treated with gemcitabine (350 mg/m2 as 4 h infusion) and vinorelbine (25 mg/m2 on days 1 and 8. Treatment was repeated every 3 weeks for a maximum of six cycles. RESULTS: Of 26 patients enrolled, 84% had received prior anthracycline treatment and 50% prior taxane therapy. In total, one complete and six partial responses were achieved, accounting for an overall response rate of 30.4%. The clinical benefit rate was 47.8%. Median duration of response and median time to progression were 7.3 months and 4.6 months, respectively. Median overall survival was 14.5 months. Although the predominant toxicity was myelosuppression with grade 3/4 neutropenia in 42% of patients, few neutropenic complications resulted. Non-hematological toxicity was generally moderate. Most common non-hematologic toxicities were nausea, vomiting, alopecia, peripheral neuropathy and elevation of liver enzymes. CONCLUSION: Gemcitabine as prolonged infusion and vinorelbine are a safe and effective combination treatment in anthracycline and/or taxane pretreated patients. Approximately 47.8% of patients derived clinical benefit from treatment. This regimen represents a therapeutic option for patients receiving second-line therapy for metastatic breast cancer.

Adult↗
PubMed2005

Novel aspects of osteoclast activation and osteoblast inhibition in myeloma bone disease.

Increased bone resorption is a major characteristic of multiple myeloma and is caused by osteoclast activation and osteoblast inhibition (uncoupling). Myeloma cells alter the local regulation of bone metabolism by increasing the receptor activator of NF-kappaB ligand (RANKL) and decreasing osteoprotegerin expression within the bone marrow microenvironment, thereby stimulating the central pathway for osteoclast formation and activation. In addition, they produce the chemokines MIP-1alpha, MIP-1beta, and SDF-1alpha, which also increase osteoclast activity. On the other hand, myeloma cells suppress osteoblast function by the secretion of osteoblast inhibiting factors, e.g., the Wnt inhibitors DKK-1 and sFRP-2. Moreover, they inhibit differentiation of osteoblast precursors and induce apoptosis in osteoblasts. The resulting bone destruction releases several cytokines, which in turn promote myeloma cell growth. Therefore, the inhibition of bone resorption could stop this vicious circle and not only decrease myeloma bone disease, but also the tumor progression.

Animals↗
PubMed2005

Proteasome inhibitors abrogate osteoclast differentiation and osteoclast function.

Cancer-induced bone disease results in bone destruction, pathological fractures, and pain. We hypothesized that the inhibition of the proteasome-ubiquitin system in osteoclasts could abolish the receptor activator of NF-kappaB ligand (RANKL) mediated osteoclast differentiation and function, since RANKL-mediated downstream signaling plays a crucial role in osteoclast life cycle. In this study, we examined the effects of the proteasome inhibitors MG-132 and MG-262 on RANKL-induced osteoclast differentiation and function. Osteoclast precursors from peripheral blood mononuclear cells were cultured in the presence of RANKL and M-CSF. Osteoclasts were identified as multi-nucleated TRAP-positive cells. Osteoclast function was quantified with the extent of dentine resorption and TRAP activity in culture supernatants. For the evaluation of the effects of proteasome inhibitors towards osteoclastogenesis, sub-apoptotic concentrations of MG-132 and MG-262 were used. Effects on NF-kappaB were obtained in treated and untreated osteoclasts. MG-132 and MG-262 inhibit both osteoclast differentiation and osteoclast function. 0.01 microM MG-132 induced a 3.2-fold (P = 0.004) and 0.001 microM MG-262 a 3.3-fold (P = 0.004) reduction of osteoclast differentiation, respectively. The resorption capacity was decreased 2.6- and 11.1-fold (P = 0.003) by treatment with 0.01 and 0.1 microM MG-132, and 14.2- and 16.6-fold (P = 0.003) by 0.001 and 0.01 microM MG-262, respectively. This decrease correlated with the extent of NF-kappaB binding capacity. In conclusion, this study shows for the first time that proteasome inhibitors act on osteoclast development and function at low concentrations and should be considered as potential drugs for the treatment of cancer-induced osteolytic bone disease.

Bone Resorption↗
PubMed2005

Definition of organ involvement and treatment response in immunoglobulin light chain amyloidosis (AL): a consensus opinion from the 10th International Symposium on Amyloid and Amyloidosis, Tours, France, 18-22 April 2004.

We undertook this study to develop uniformly accepted criteria for the definition of organ involvement and response for patients on treatment protocols for immunoglobulin light-chain amyloidosis (AL). A consensus panel was convened comprising 13 specialists actively involved in the treatment of patients with amyloidosis. Institutional criteria were submitted from each, and a consensus was developed defining each organ involved and the criteria for response. Specific criteria have been developed with agreed on definitions of organ and hematologic response as a result of discussions at the 10th International Symposium on Amyloid and Amyloidosis held in Tours, France, April 2004. These criteria now form the working definition of involvement and response for the purposes of future data collection and reporting. We report criteria that centers can now use to define organ involvement and uniform response criteria for reporting outcomes in patients with light-chain AL.

Amyloid↗
PubMed2005

Gemcitabine and mitoxantrone in metastatic breast cancer: a phase-I-study.

BACKGROUND: Gemcitabine and mitoxantrone are active agents for the treatment of metastatic breast cancer. Due to different modes of action and a favorable toxicity profile they are suitable for combination therapy. This phase I trial was initiated to determine the optimal doses for the combination in patients with metastatic breast cancer. Secondary objectives included the evaluation of the safety and efficacy of the regimen. PATIENTS AND METHODS: Patients with metastatic breast cancer were treated with gemcitabine (1000-1400 mg/m(2)) on days 1, 8 and 15 and mitoxantrone (10-14 mg/m(2)) on day 8. Treatment was repeated every 4 weeks for a maximum of 8 cycles. Doses were assigned at registration according to the escalation scheme. RESULTS: Twenty-six patients received a total of 93 cycles at 5 different dose levels. The maximum tolerated doses were 1200 mg/m(2) gemcitabine and 14 mg/m(2) mitoxantrone with grade 4 neutropenia being the dose limiting toxicity. Recommended phase II doses, however, are gemcitabine 1200 mg/m(2) and mitoxantrone 12 mg/m(2) based on a similar median dose intensity and a more favorable toxicity profile. Predominant toxicity was myelosuppression. Most common non-hematological toxicities were nausea, vomiting, alopecia and elevation of liver enzymes. Twenty-one patients were assessable for response. Four patients achieved a partial response accounting for an overall response rate of 19%. In addition, 12 patients (57%) had stable disease and 5 patients (24%) failed to response to the treatment. Median duration of response and duration of clinical benefit were 14 and 9 months, respectively. CONCLUSION: In this phase I study of gemcitabine and mitoxantrone, the DLT was neutropenia. Recommended phase II doses are gemcitabine 1200 mg/m(2) and mitoxantrone 12 mg/m(2).

Adult↗
PubMed2005

Prolonged infusion of gemcitabine in advanced solid tumors: a phase-I-study.

BACKGROUND: Gemcitabine is a pro-drug that has to be phosphorylated to gemcitabine-triphosphate in order to exhibit its antineoplastic activity. This reaction involves the enzyme deoxycytidine kinase which is saturated at plasma concentrations following standard 30-min infusions. Pharmacological studies indicate that prolonged administration of gemcitabine might result in higher intracellular concentrations of active metabolites. This phase I trial was therefore initiated to determine the optimal dose of gemcitabine administered over 4 h in patients with advanced solid tumors. PATIENTS AND METHODS: Patients were treated with gemcitabine as 4 h-infusion on day 1, 8 and 15 in 4 week intervals. The starting dose was 350 mg/m(2). Doses were escalated in 50 mg/m(2) increments. RESULTS: Twenty-one patients were treated at doses ranging from 350 to 450 mg/m(2). The maximum tolerated dose was 400 mg/m(2) with neutropenia, thrombocytopenia, stomatitis and elevation of liver enzymes being dose limiting toxicities (DLTs). Hematologic and nonhematological toxicities were generally mild to moderate. Most common side effects were myelosuppression, nausea, elevation of liver enzymes and asthenia. Objective responses were noted in patients with hepatocellular carcinoma and cholangio-carcinoma. CONCLUSION: In this phase I study of gemcitabine as 4h-infusion, DLTs were neutropenia, thrombocytopenia, stomatitis and elevation of liver enzymes. The recommended dose for phase II studies is 400 mg/m(2).

Adult↗
PubMed2005

Myeloma bone disease.

Bone destruction is a hallmark of multiple myeloma, and recent studies demonstrated a strong interdependence between tumor progression and bone resorption. Increased bone resorption as a major characteristic of multiple myeloma is caused by osteoclast activation and osteoblast inhibition (uncoupling). Myeloma cells alter the local regulation of bone metabolism by increasing the receptor activator of NF-kappaB ligand (RANKL) and decreasing osteoprotegerin (OPG) expression within the bone marrow microenvironment, thereby stimulating the central pathway for osteoclast formation and activation. In addition, they produce the chemokines MIP-1alpha, MIP-1beta and SDF-1alpha, which also increase osteoclast activity. Furthermore, myeloma cells suppress osteoblast function by the secretion of osteoblast inhibiting factors, e.g. Dickkopf (DKK)-1. The resulting bone destruction releases several cytokines, which in turn promote myeloma cell growth. Therefore, the inhibition of bone resorption could stop this vicious circle and not only decrease myeloma bone disease, but also the tumor progression. Preclinical studies provided strong evidence that the suppression of the osteoclast activity using bisphosphonates, RANKL blockade or inhibition of MIP-1alpha or MIP-1beta is effective both in reducing myeloma bone disease and tumor growth and therefore may offer an important treatment strategy in multiple myeloma.

Bone Diseases↗
PubMed2005

Primary chemotherapy with gemcitabine, liposomal doxorubicin and docetaxel in patients with locally advanced breast cancer: results of a phase I trial.

The primary objective was to determine the optimal doses for gemcitabine (prolonged infusion), liposomal doxorubicin (Myocet) and docetaxel as primary (neoadjuvant) chemotherapy for locally advanced breast cancer. Secondary objectives included evaluation of the safety and efficacy of the regimen. Patients (n=19) with histologically confirmed stage II or III breast cancer were treated with liposomal doxorubicin (50-60 mg/m2) and docetaxel (60-75 mg/m2) on day 1, and gemcitabine as 4-h infusion (350-400 mg/m2) on day 4. Treatment was repeated every 3 weeks for a maximum of 6 cycles. The maximum tolerated doses were gemcitabine 350 mg/m2, liposomal doxorubicin 60 mg/m2 and docetaxel 75 mg/m2. Dose-limiting toxicities were stomatitis, diarrhea and infection. The predominant hematologic toxicity was mild-to-moderate myelosuppression with grade 3/4 neutropenia in 20% of cycles. Non-hematologic toxicity was generally mild, with no grade 4 toxicities being observed. Predominant non-hematologic toxicity was stomatitis, which occurred in 95% of patients. Grade 3 toxicities were reported for stomatitis, nausea, diarrhea, infection and constipation. No cases of cardiac, renal, pulmonary or neurotoxicity were observed. The clinical response rate was 83% and histologically confirmed, clinically complete remissions occurred in two patients (11%). We conclude that the combination of gemcitabine (prolonged infusion), liposomal doxorubicin and docetaxel is safe and highly effective in patients with locally advanced breast cancer as defined by maximum tolerated doses. The evaluated schedule is suitable for phase II studies.

Adult↗