Osteoclast inhibitory peptide 2 inhibits osteoclast formation via its C-terminal fragment.

Osteoclast inhibitory peptide 2 (OIP-2) is a novel autocrine/paracrine factor produced by osteoclasts (OCLs) that inhibits bone resorption and OCL formation in vitro and in vivo. It is identical to the asparaginyl endopeptidase legumain. During maturation of OIP-2, a signal peptide and a 17-kDa C-terminal fragment (CTF) are cleaved to produce the mature enzyme. To determine if enzyme activity is required for inhibition of OCL formation or if only the CTF is responsible for these effects, we synthesized His-tagged complementary DNA (cDNA) constructs for the CTF of OIP-2, the proform of OIP-2, and the "mature enzyme" form of OIP-2. The proform or the CTF portion of OIP-2 inhibited OCL formation in a dose-dependent manner in murine bone marrow cultures stimulated with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The mature form of OIP-2, which was enzymatically active, did not inhibit OCL formation. In addition, OIP-2 inhibited OCL formation in cultures of highly purified human OCL precursor cells or RAW264.7 cells stimulated with 10 ng/ml of receptor activator of NF-kappaB (RANK) ligand. Binding studies with His-tagged OIP-2 showed expression of a putative OIP-2 receptor on RAW264.7 cells treated with RANK ligand for 4 days and human marrow cultures treated with 1,25(OH)2D3 for 3 weeks. These data show that the CTF of OIP-2, rather than the mature enzyme, mediates the inhibitory effects of OIP-2 through a putative receptor on OCL precursors.

IL-6 mediates the effects of IL-1 or TNF, but not PTHrP or 1,25(OH)2D3, on osteoclast-like cell formation in normal human bone marrow cultures.

A potent interleukin-6 (IL-6) antagonist (Sant 5), which binds tightly to the IL-6alpha receptor but has impaired gp130 heterodimerization, has been developed recently by site-directed mutagenesis of human IL-6. We report here that Sant 5 inhibits IL-6-stimulated osteoclast-like multinucleated cell (MNC) formation in human marrow cultures but also inhibits the stimulatory effects of IL-1 or tumor necrosis factor alpha (TNF-alpha in these cultures. We further show that a neutralizing antibody to IL-6 also inhibits the stimulatory effects of IL-1 or TNF-alpha in these cultures. In contrast, Sant 5 had no effect on parathyroid hormone related protein (PTHrP) or 1,25-dihydroxyvitamin D3 stimulated MNC formation in human marrow cultures. Transfection of a human marrow stromal cell line, which normally induces osteoclast formation through production of IL-6, with the Sant 5 cDNA driven by a cytomegalovirus (CMV) promoter blocked the capacity of these cells to stimulate osteoclast-like cell formation. These Sant 5 transfected cells and conditioned media from these cells also inhibited the stimulatory effects of the parent cell line on MNC formation. These data suggest that IL-6 mediates the effects of IL-1 and TNF on human osteoclast formation, but in contrast to murine systems, does not mediate the effects of PTHrP. These data further demonstrate that stromal cells transfected with the Sant 5 cDNA can constitutively produce high levels of the IL-6 antagonist and inhibit osteoclast formation in vitro.

Characterization of the osteoclast vacuolar H(+)-ATPase B-subunit.

During bone resorption, osteoclasts acidify the extracellular bone resorbing compartment via a vacuolar H(+)-ATPase (V-ATPase), which resides in the ruffled-border membrane. In an effort to characterize the composition of the osteoclast V-ATPase catalytic domain, we have isolated a cDNA clone that encodes the V-ATPase B-subunit from a cDNA library constructed from highly purified chicken osteoclasts. Comparison of the predicted amino-acid sequence with the published sequences of isoforms of V-ATPase B-subunits from other sources revealed that the chicken osteoclast B-subunit is brain type and not kidney type. Furthermore, only clones encoding the brain type isoform of subunit B could be generated by PCR from a cDNA library prepared from human osteoclastoma osteoclast-like cells. Northern blot analysis revealed that two B-subunit mRNAs, approx. 1.7 and 3.5 kb in length, are expressed in chicken bone marrow mono-nuclear cells, brain and kidney, although the relative amounts of these two transcripts were different in each tissue. In brain, the 3.5-kb mRNA was predominantly expressed. In bone marrow cells, the levels of the 1.7-kb mRNA were higher than in other tissues and expression of this message was increased by 1,25-dihydroxyvitamin D-3, suggesting that this mRNA is specifically upregulated during osteoclast differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and identification of annexin II as an autocrine/paracrine factor that increases osteoclast formation and bone resorption.

Autocrine products of osteoclasts such as interleukin-6 may play an important role in normal osteoclast formation and activity. To identify novel stimulatory factors for osteoclasts, we have prepared a mammalian cDNA expression library generated from highly purified human osteoclast-like multinucleated cells (MNC) formed in long term bone marrow cultures and screened this library for autocrine factors that enhance MNC formation. A candidate clone which stimulated MNC formation was isolated. Sequence analysis showed that this cDNA encoded annexin II (AXII). Purified recombinant AXII significantly increased MNC formation in human bone marrow cultures in the absence of 1,25-(OH)2 vitamin D3 and enhanced MNC formation in mouse bone marrow cultures treated with 10(-9) M 1,25-(OH)2 vitamin D3. The enhanced MNC formation in murine marrow cultures resulted in increased bone resorption. Treatment of fetal rat long bones with AXII and 1,25-(OH)2 vitamin D3 significantly increased bone resorption compared to 1,25-(OH)2 vitamin D3 alone. Reverse transcriptase polymerase chain reaction analysis demonstrated that AXII mRNA was expressed at high levels in RNA isolated from highly purified giant cells from osteoclastomas, human osteoclast-like MNC, and pagetic bone. Western blot analysis of conditioned media collected from human marrow cultures showed that AXII was present in the media. Furthermore, approximately 50% of total AXII produced by cells transfected with AXII cDNA was present in the conditioned media. These data suggest that the AXII is an autocrine factor that enhances osteoclast formation and bone resorption and demonstrate a previous unknown function for AXII.

Phase I trial of dacarbazine with cyclophosphamide, carmustine, etoposide, and autologous stem-cell transplantation in patients with lymphoma and multiple myeloma.

PURPOSE: We investigated the feasibility of escalating doses of dacarbazine (DTIC) in combination with high-dose cyclophosphamide, carmustine, and etoposide (CBV) given with autologous stem-cell transplantation in 33 patients with relapsed or refractory lymphoma or multiple myeloma. PATIENTS AND METHODS: Eligible patients were treated in this phase I study with cyclophosphamide (7.2 g/m2), carmustine (BCNU) (600 mg/m2), etoposide (2.4 g/m2), and escalating doses of DTIC (3,000 to 6,591 mg/m2) administered either as a 2- (in 23 patients) or a 6- (in 10 patients) hour infusion to determine the maximum-tolerated dose (MTD) of DTIC and the toxicity profile of this combination. RESULTS: The MTD of DTIC infused over 2 hours and given with the CBV regimen was 3,900 mg/m2, with the dose-limiting toxicity being hypotension. Seven patients experienced transient acute hypocalcemia in association with the DTIC infusion. Prolonging the DTIC infusion to 6 hours or administration of supplemental calcium did not allow further dose escalation of DTIC to occur. Other non-hematologic toxicities observed with this regimen have been reported with CBV alone. Of 25 patients assessable for tumor response at first evaluation posttransplant, 13 (52%) were in complete remission (CR), four (16%) were in partial remission (PR), five (20%) had stable disease (SD), and three (12%) had progressive disease (PROG). Of 31 patients assessable for relapse-free survival, 22 are alive with 13 in CR, one in PR, two with SD, and six with PROG at a median follow-up duration of 313 days (range, 35 to 749+). Treatment-related mortality occurred in six patients (18%). CONCLUSION: The feasibility of combining DTIC in high doses with the CBV regimen has been demonstrated. Dose-limiting hypotension is transient and reversible when DTIC is administered at 3,900 mg/m2 with CBV. Future trials to evaluate the effect of the addition of DTIC to the CBV regimen on response rate and relapse-free survival are encouraged.

Nutritional parameters observed during 28-day infusion of recombinant human tumor necrosis factor-alpha.

In conjunction with a Phase I investigation of the antineoplastic activity of recombinant human tumor necrosis factor-alpha (TNF-alpha), administered as a 28-day continuous infusion, selected nutritional parameters were evaluated to identify any effect that might be attributed to the TNF infusion. Seven clinically stable men with a variety of tumor types were studied. None had clinical or laboratory evidence of significant malnutrition before entry into the study. Five patients received 10 micrograms of recombinant human TNF-alpha per square meter per day and two patients received 25 micrograms/m2 per day. Indirect calorimetry assessment of resting energy expenditure, body weight, serum TNF concentration, and laboratory analysis of common nutritional markers (albumin, prealbumin, and triglycerides) were performed at baseline, day 14, day 28, and 2 weeks (day 42) after completion of the infusion. There were no statistically significant differences by analysis of variance observed in any parameter during the study period compared with baseline values and values on day 42. Also, there were no differences between any parameters when stratified by dose administered, although the number of patients studied was small. Measured serum TNF concentrations ranged from 0.02 to 1.56 ng/mL and did not correlate with study day or dose of TNF infused. No correlation was observed between serum TNF concentrations and resting energy expenditure. Although others have reported significant metabolic changes associated with acute administration of TNF in humans and animals, our experience does not support a hypermetabolic state in patients receiving low daily dose, long-term (28-day) continuous infusion of recombinant human TNF-alpha, a state that may be consistent with many neoplastic conditions.

Tartrate-resistant acid phosphatase gene expression as a facile reporter gene for screening transfection efficiency in mammalian cell cultures.

The efficiency of DNA transfection into mammalian cell cultures has been monitored using a variety of reporter assays. However, the common procedures are expensive, time-consuming and usually cannot identify the transfected cell population directly. In the present communication we describe a simple, inexpensive and efficient method to directly identify DNA transfection in mammalian cells using tartrate-resistant acid phosphatase (TRAP) gene expression. The method involves the transfection of a plasmid (pCT3), which contains TRAP cDNA driven by a CMV promoter, into mammalian cells. The cells can then be stained for TRAP activity, and the transfection efficiency can be determined by simply counting the positively transfected cells in a defined area with a microscope. This method permits screening of mammalian cells for transfection efficiency in multi-well plates. After waiting 30-40 minutes to allow the TRAP assay to saturate, wells can be scored in 1-2 minutes with little difficulty in detecting the transfected cells.