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Bortezomib represents a new class of anti-cancer drugs, the proteasome inhibitors. We evaluated the in vitro activity of bortezomib with regard to tumour-type specificity and possible mechanisms of drug resistance in 115 samples of tumour cells from patients and in a cell-line panel, using the short-term fluorometric microculture cytotoxicity assay. Bortezomib generally showed dose-response curves with a steep slope. In patient cells, bortezomib was more active in haematological than in solid tumour samples. Myeloma and chronic myeloid leukaemia were the most sensitive tumour types although with great variability in drug response between the individual samples. Colorectal and kidney cancer samples were the least sensitive. In the cell-line panel, only small differences in response were seen between the different cell lines, and the proteasome inhibitors, lactacystin and MG 262, showed an activity pattern similar to that of bortezomib. The cell-line data suggest that resistance to bortezomib was not mediated by MRP-, PgP, GSH-; tubulin and topo II-associated MDR. Combination experiments indicated synergy between bortezomib and arsenic trioxide or irinotecan. The data support the current use of bortezomib but also points to its potential utility in other tumour types and in combination with cytotoxic drugs.

Insulin-like growth factor I (IGF-I) has documented anabolic effects on osteoblasts, whereas its influence on osteoclasts and on bone resorption is unclear. We have investigated the effects of IGF-I on osteoclast recruitment and bone resorption in vitro. IGF-I (at and above 1 nM) stimulated the formation of multinucleated tartrate-resistant acid phosphatase positive cells in murine bone marrow cultures, incubated for 9 days. The number of multinucleated cells increased to 540 +/- 160% of control (mean +/- SEM) in cultures treated with 10 nM IGF-I. IGF-I (0.1-100 nM) had no effect by itself on 45Ca-release from prelabelled neonatal mouse calvarial bones. However, IGF-I (100 nM) had an inhibitory effect on bone resorption induced by prostaglandin E2 and 1,25(OH)2D3. These findings indicate that IGF-I enhances the formation of osteoclasts-like cells in long-term bone marrow cultures. In bone organ cultures, however, IGF-I has an inhibitory effect on stimulated bone resorption, suggesting that IGF-I inhibits existing osteoclasts and, alternatively, that IGF-I interferes with the osteoblast-derived factor(s) that stimulate existing osteoclasts.

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Previous studies have demonstrated high concentrations of polyamines in neoplastic tissue and embryos and these compounds are therefore believed to play a role in cellular growth and embryonic development. Maternal diabetes causes embryonic dysmorphogenesis and alterations in embryonic polyamine concentrations may contribute to this process. In the present study we have measured the contents of DNA, putrescine, spermidine and spermine in embryos on days 10 and 11 of gestation in normal and diabetic rats. We also estimated the activity of ornithine decarboxylase (ODC) in embryos on days 9–11. We found that maternal diabetes causes delayed growth as reflected by decreased content of DNA on day 11 in the embryos of the diabetic group. Both the polyamine content and ODC activity were altered in the embryos of diabetic rats. Thus, the polyamines were increased on day 10 and decreased on day 11, and the ODC activity was decreased in a down-regulated manner in day-10 embryos of the diabetic rats. These findings suggest that polyamine metabolism is involved in the dysmorphogenesis of diabetic pregnancy.

It has been reported that osteoclastic function is regulated by calcium-induced alterations in cytoplasmic free calcium ([Ca2+]i), possibly through a specific receptor. We have investigated whether osteoclasts, isolated from neonatal rat long bones, possess the divalent cation-receptor that has been demonstrated on parathyroid cells. Studies with fura-2 loaded adherent single cells showed that an increase in extracellular Ca2+ ([Ca2+]e) from 0.5 mM to 10 mM resulted in an increase in [Ca2+]i in isolated rat osteoclasts, from a basal value of 94.7 +/- 16.2 to 150.6 +/- 22.4 nM (means +/- SEM; n = 14). The shape and time course of the [Ca2+]i increase varied considerably from cell to cell. Less than half of the cells responded with a rapid transient increase whereas the rest responded with a slow increase that reached a plateau within 1-2 minutes. When [Ca2+]e was changed back to 0.5 mM, a slow decrease in [Ca2+]i was monitored. Immunohistochemical staining with two different monoclonal antibodies, recognizing the putative Ca2+ receptor on parathyroid cells, did not indicate any staining on freshly isolated rat osteoclasts. Thus, our data demonstrate that an increase in [Ca2+]e causes an elevation of [Ca2+]i in osteoclasts. This increase is not mediated via the putative cation-receptor found on parathyroid cells.

BackgroundPatients with rheumatoid arthritis (RA) have increased development of osteoporosis. We have identified an increased incidence of low-energy fractures in RA patients by analysing a population based register of fractures in northern Sweden. In RA increased serum levels and associations with genes encoding proteins involved in the Wnt pathway have been found and related to joint destruction in RAObjectivesTo analyse in patients with RA nine SNPs related to osteoporotic fractures in the general population and to joint destruction in RA.MethodsThe register of patients with RA (ARA criteria) consecutively included since 1995 (n=1178) was co-analysed with the register of Umeå injury database, Umeå, Sweden to identify low-energy fractures. This database was constituted in 1993 and covers six communities with a population at risk of 118000 adults. All individuals admitted to the emergency ward are included. DNA was available from 866 RA patients of whom 244 had a fracture after the diagnosis of RA. As controls served 997 sex and age matched population controls from the same area. The following SNPs have been analysed; rs3801387 (WNT16), rs6666455 (SOAT), rs3736228 (LRP5), rs4796995 (FAM210A), rs4792909 (SOST), rs2062377 (TNFRSF11B/OPG), rs884205 (TNFRSF11A/RANK), rs9533090 (TNFSF11/RANKl), and rs1373004 (DKK1) using KASP™ genotyping assays (LGC genomics Ltd, Hoddesdon, UK).ResultsThe distribution of the genotypes of rs4796995, rs3801387, and rs6666455 were not in Hardy-Weinberg equilibrium in the RA patients. Carrier of the major allele of rs4796995 was significantly associated with RA (odds ratio 1.48 [95%CI 1.06-2.06] p=0.020), and more strengthened among women (OR 1.62 [95%CI 1.10-2.39] p=0.014).The genotype distribution of rs1373004 differed significantly between RA patients with fractures and population controls (c2=8.21, p=0.017, 2df). Carrier of the rare allele was more common among RA patients with fractures compared with controls (OR 1.56 [95%CI 1.13-2.16] p=0.007).A difference in genotype distribution for rs4792909 (encoding sclerostin) was found comparing RA patients with and without fracture (c2=6.66, p=0.036, 2df). Being homozygous for the major allele was more common among those patients with fracture (OR 1.42 [95%CI 1.05-1.93] p=0.023) and after adjustment for ACPA, OR=1.51 [95%CI1.09-2.08] (p=0.012).ConclusionsGenes related to osteoporotic fractures in the general populations were identified also associated with increased risk of fractures in patients with RA. The increased risk of fracture in patients with RA has besides the disease and its treatment also a contribution of genetic factors suggested to be related to joint destruction.ReferencesEstrada K et al Nat Genet 2012;44:491-501.Rooy de DPC et al Ann Rheum Dis 2013;72:769.AcknowledgementsThe register of Umeå injury database, Umeå, Sweden and the Medical Biobank of northern Sweden.Disclosure of InterestNone declared