Lorenz Kleeberg

Bortezomib inhibits human osteoclastogenesis.

In multiple myeloma, the overexpression of receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) leads to the induction of NF-κB and activator protein-1 (AP-1)-related osteoclast activation and enhanced bone resorption. The purpose of this study was to examine the molecular and functional effects of proteasome inhibition in RANKL-induced osteoclastogenesis. Furthermore, we aimed to compare the outcome of proteasome versus selective NF-κB inhibition using bortezomib (PS-341) and I-κB kinase inhibitor PS-1145. Primary human osteoclasts were derived from CD14+ precursors in presence of RANKL and macrophage colony-stimulating factor (M-CSF). Both bortezomib and PS-1145 inhibited osteoclast differentiation in a dose- and time-dependent manner and furthermore, the bone resorption activity of osteoclasts. The mechanisms of action involved in early osteoclast differentiation were found to be related to the inhibition of p38 mitogen-activated protein kinase pathways, whereas the later phase of differentiation and activation occurred due to inhibition of p38, AP-1 and NF-κB activation. The AP-1 blockade contributed to significant reduction of osteoclastic vascular endothelial growth factor production. In conclusion, our data demonstrate that proteasomal inhibition should be considered as a novel therapeutic option of cancer-induced lytic bone disease.

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.

Proteasome as an Emerging Therapeutic Target in Cancer

The 26S proteasome is a multicatalytic intracellular protease expressed in eukaryotic cells. It is responsible for selective degradation of intracellular proteins that are responsible for cell proliferation, growth, regulation of apoptosis and transcription of genes involved in execution of key cellular functions. Thus proteasome inhibition is a potential treatment option for cancer and diseases due to aberrant inflammation condition. Treatment with proteasome inhibitors results in stabilization and accumulation proteasome substrates, a phenomenon that may result in confounding signals in cells, cell cycle arrest and activation of apoptotic programs. The inhibition of the transcriptional factor nuclear factor kappaB (NF-kappaB) activation was found as one of crucial mechanisms in induction of apoptosis, overcoming resistance mechanisms and inhibition of immune response and inflammation mechanisms. Bortezomib (PS-341) and PS-519 are the first proteasome inhibitors that have 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) for the treatment of relapsed multiple myeloma. At present, several phase II and phase III trials in hematological malignancies and solid tumors are ongoing. PS-519 that focuses on inflammation, reperfusion injury and ischemia is currently under evaluation for the indication of acute stroke.

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.

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.

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).

Novel renal replacement strategies for the elimination of serum free light chains in patients with kappa light chain nephropathy

Multiple myeloma (MM) is a malignancy with excessive production of monoclonal proteins. At disease presentation 30% of MM patients have significant renal impairment which may progress to renal failure requiring dialysis. Besides chemotherapy extracorporeal elimination procedures such as plasma exchange have been applied as adjuvant strategies to eliminate free light chains from circulating blood, however the efficacy was poor with older techniques. We report about a highly efficient method to eliminate serum free light chain (sFLC) using a newly designed protein leaking membrane in patients suffering from sFLC induced acute renal failure. The protein leaking membrane (HCO 1100) is characterized by increased pore size facilitating elimination of middle molecules such as sFLC kappa (22.5 kD). The HCO 1100 membrane was applied in a hemodialysis and hemodiafiltration mode and compared to standard procedures (high flux hemodialysis, hemodiafiltration and plasma exchange). Hemodiafiltration with the protein leaking membrane HCO 1100 was superior to all other extracorporeal replacement strategies in eliminating sFLC-kappa from circulating blood. A median blood reduction rate of 40.8% (range 13.9% - 66.4%) was achieved during hemodiafiltration. The corresponding peak clearance rate was 25 ml/min. Importantly, the poorest elimination rate was achieved by plasma exchange followed by standard high flux hemodialysis. Extracorporeal elimination strategies with the protein leaking membrane HCO 1100 may be a promising adjuvant treatment strategy for patients with sFLC nephropathy requiring dialysis. Hemodiafiltration and to lesser extend also hemodialysis with the HCO 1100 hemofilter are able to eliminate substantial amounts of sFLC kappa in MM patients.