Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026764 (multiple myeloma)
 36,148 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzyme that catalyzes the formation of GDP-L-fucose from GTP and beta-L-fucose-1-phosphate (i.e. GDP-beta-L-fucose pyrophosphorylase, GFPP) was purified about 560-fold from the cytosolic fraction of pig kidney. At this stage, there were still a number of protein bands on SDS gels, but only the 61-kDa band became specifically labeled with the photoaffinity substrate, azido-GDP-L-[32P]fucose. Several peptides from this 61-kDa band were sequenced and these sequences were used for cloning the gene. The cDNA clone yielded high levels of GFPP activity when expressed in myeloma cells and in a baculovirus system, demonstrating that the 61-kDa band is the authentic GFPP. The porcine tissue with highest specific activity for GFPP was kidney, with lung, liver, and pancreas being somewhat lower. GFPP was also found in Chinese hamster ovary, but not Madin-Darby canine kidney cells. Northern analysis showed the mRNA in human spleen, prostate, testis, ovary, small intestine, and colon. GFPP was stable at 4 (o)C in buffer containing 50 mM sucrose, with little loss of activity over a 9-day period. GTP was the best nucleoside triphosphate substrate but significant activity was also observed with ITP and to a lesser extent with ATP. The enzyme was reasonably specific for beta-L-fucose-1-P, but could also utilize alpha-D-arabinose-1-P to produce GDP-alpha-D-arabinose. The product of the reaction with GTP and alpha-L-fucose-1-P was characterized as GDP-beta-L-fucose by a variety of chemical and chromatographic methods.
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PMID:GDP-L-fucose pyrophosphorylase. Purification, cDNA cloning, and properties of the enzyme. 980 72

Selection for in vitro drug resistance can result in a complex phenotype with more than one mechanism of resistance emerging concurrently or sequentially. We examined emerging mechanisms of drug resistance during selection with mitoxantrone in the human myeloma cell line 8226. A novel transport mechanism appeared early in the selection process that was associated with a 10-fold resistance to mitoxantrone in the 8226/MR4 cell line. The reduction in intracellular drug concentration was ATP-dependent and ouabain-insensitive. The 8226/MR4 cell line was 34-fold cross-resistant to the fluorescent aza-anthrapyrazole BBR 3390. The resistance to BBR 3390 coincided with a 50% reduction in intracellular drug concentration. Confocal microscopy using BBR 3390 revealed a 64% decrease in the nuclear:cytoplasmic ratio in the drug-resistant cell line. The reduction in intracellular drug concentration of both mitoxantrone and BBR 3390 was reversed by a novel chemosensitizing agent, fumitremorgin C. In contrast, fumitremorgin C had no effect on resistance to mitoxantrone or BBR 3390 in the P-glycoprotein-positive 8226/DOX6 cell line. Increasing the degree of resistance to mitoxantrone in the 8226 cell line from 10 to 37 times (8226/MR20) did not further reduce the intracellular drug concentration. However, the 8226/MR20 cell line exhibited 88 and 70% reductions in topoisomerase II beta and alpha expression, respectively, compared with the parental drug sensitive cell line. This decrease in topoisomerase expression and activity was not observed in the low-level drug-resistant, 8226/MR4 cell line. These data demonstrate that low-level mitoxantrone resistance is due to the presence of a novel, energy-dependent drug efflux pump similar to P-glycoprotein and multidrug resistance-associated protein. Reversal of resistance by blocking drug efflux with fumitremorgin C should allow for functional analysis of this novel transporter in cancer cell lines or clinical tumor samples. Increased resistance to mitoxantrone may result from reduced intracellular drug accumulation, altered nuclear/cytoplasmic drug distribution, and alterations in topoisomerase II activity.
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PMID:Multiple mechanisms confer drug resistance to mitoxantrone in the human 8226 myeloma cell line. 1007 Sep 58

The glutamine metabolism was studied in glucose-starved and glucose-sufficient hybridoma and Sp2/0-Ag14 myeloma cells. Glucose starvation was attained by cultivating the hybridoma cells with fructose instead of glucose, and the myeloma cells with a low initial glucose concentration which was rapidly exhausted. Glutamine used in the experiments was labeled with 15N, either in the amine or in the amide position. The fate of the label was monitored by 1H/15N NMR analysis of released 15NH+4 and 15N-alanine. Thus, NH+4 formed via glutaminase (GLNase) could be distinguished from NH+4 formed via glutamate dehydrogenase (GDH). In the glucose-sufficient cells a small but measurable amount of 15NH+4 released by GDH could be detected in both cell lines (0.75 and 0.31 micromole/10(6) cells for hybridoma and myeloma cells, respectively). The uptake of glutamine and the total production of NH+4 was significantly increased in both fructose-grown hybridoma and glucose-starved myeloma cells, as compared to the glucose-sufficient cells. The increased NH+4 production was due to an increased throughput via GLNase (1.6 -1.9-fold in the hybridoma, and 2.7-fold in the myeloma cell line) and an even further increased metabolism via GDH (4.8-7.9-fold in the hybridoma cells, and 3.1-fold in the myeloma cells). The data indicate that both GLNase and GDH are down-regulated when glucose is in excess, but up-regulated in glucose-starved cells. It was calculated that the maximum potential ATP production from glutamine could increase by 35-40 % in the fructose-grown hybridoma cells, mainly due to the increased metabolism via GDH.
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PMID:Elevated glutamate dehydrogenase flux in glucose-deprived hybridoma and myeloma cells: evidence from 1H/15N NMR. 1009 57

Bisphosphonates (BPs) used as inhibitors of bone resorption all contain two phosphonate groups attached to a single carbon atom, forming a "P-C-P" structure. The bisphosphonates are therefore stable analogues of naturally occuring pyrophosphate-containing compounds, which now helps to explain their intracellular as well as their extracellular modes of action. Bisphosphonates adsorb to bone mineral and inhibit bone resorption. The mode of action of bisphosphonates was originally ascribed to physico-chemical effects on hydroxyapatite crystals, but it has gradually become clear that cellular effects must also be involved. The marked structure-activity relationships observed among more complex compounds indicate that the pharmacophore required for maximal activity not only depends upon the bisphosphonate moiety but also on key features, e.g., nitrogen substitution in alkyl or heterocyclic side chains. Several bisphosphonates (e.g., etidronate, clodronate, pamidronate, alendronate, tiludronate, risedronate, and ibandronate) are established as effective treatments in clinical disorders such as Paget's disease of bone, myeloma, and bone metastases. Bisphosphonates are also now well established as successful antiresorptive agents for the prevention and treatment of osteoporosis. In particular, etidronate and alendronate are approved as therapies in many countries, and both can increase bone mass and produce a reduction in fracture rates to approximately half of control rates at the spine, hip, and other sites in postmenopausal women. In addition to inhibition of osteoclasts, the ability of bisphosphonates to reduce the activation frequency and birth rates of new bone remodeling units, and possibly to enhance osteon mineralisation, may also contribute to the reduction in fractures. The clinical pharmacology of bisphosphonates is characterized by low intestinal absorption, but highly selective localization and retention in bone. Significant side effects are minimal. Current issues with bisphosphonates include the introduction of new compounds, the choice of therapeutic regimen (e.g., the use of intermittent dosing rather than continuous), intravenous vs. oral therapy, the optimal duration of therapy, the combination with other drugs, and extension of their use to other conditions, including steroid-associated osteoporosis, male osteoporosis, arthritis, and osteopenic disorders in childhood. Bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of osteoclasts. It is likely that bisphosphonates are internalized by osteoclasts and interfere with specific biochemical processes and induce apoptosis. The molecular mechanisms by which these effects are brought about are becoming clearer. Recent studies show that bisphosphonates can be classified into at least two groups with different modes of action. Bisphosphonates that closely resemble pyrophosphate (such as clodronate and etidronate) can be metabolically incorporated into nonhydrolysable analogues of ATP that may inhibit ATP-dependent intracellular enzymes. The more potent, nitrogen-containing bisphosphonates (such as pamidronate, alendronate, risedronate, and ibandronate) are not metabolized in this way but can inhibit enzymes of the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small GTPases. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explains the loss of osteoclast activity and induction of apoptosis. These different modes of action might account for subtle differences between compounds in terms of their clinical effects. In conclusion, bisphosphonates are now established as an important class of drugs for the treatment of bone diseases, and their mode of action is being unravelled. As a result, their full therapeutic potential is gradual
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PMID:Bisphosphonates: from the laboratory to the clinic and back again. 1042 31

Previous work with 8-chloro-cAMP (8-Cl-cAMP) has raised questions as to whether it works as a cAMP analogue or as a nucleoside analogue after its conversion to 8-chloro-adenosine (8-Cl-Ado). Although degradation of 8-Cl-cAMP to 8-Cl-Ado in culture medium or plasma has been shown, cellular pharmacology data are missing. The purpose of the present study was to identify the cellular metabolism of these drugs and their actions in a human multiple myeloma cell line. The cells were incubated with either 8-Cl-Ado or 8-Cl-cAMP to follow the cellular metabolism of these agents. Both 8-Cl-cAMP and 8-Cl-Ado incubation resulted in the accumulation of 8-Cl-Ado mono-, di-, and tri-phosphate (8-Cl-ATP), however, the triphosphate was the major cytotoxic metabolite. Accumulation of 8-Cl-ATP was dependent on both the exogenous concentration of 8-Cl-Ado and incubation time. At the 10 microM level of 8-Cl-Ado, >400 microM 8-Cl-ATP accumulated in multiple myeloma cells after continuous incubation for 12 h. Similar incubation with 8-Cl-cAMP also resulted in accumulation of 8-Cl-ATP in the cells, albeit at a lower level. The formation of 8-Cl-ATP from 8-Cl-cAMP was inhibited by >80% in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine in the medium, suggesting extracellular conversion of 8-Cl-cAMP to 8-Cl-Ado. Cells lacking Ado kinase did not accumulate 8-Cl-ATP, either from 8-Cl-Ado or 8-Cl-cAMP, and were resistant to these agents. There was also a decline in the endogenous level of the cellular ATP pool parallel to the accumulation of 8-C1-ATP. The elimination of 8-Cl-ATP was biphasic and slow from the cells. The accumulation of 8-Cl-ATP and a decline in the ATP pool inhibited RNA synthesis but did not affect DNA synthesis for up to 12 h of incubation. Taken together, these data demonstrate that the cytotoxic metabolite of 8-Cl-Ado and 8-Cl-cAMP is 8-Cl-ATP. Hence, 8-Cl-cAMP serves as a prodrug and is converted to 8-Cl-Ado in medium with subsequent phosphorylation to accumulate as 8-Cl-ATP in cells. At the cellular level, 8-Cl-ATP is associated with a decrease in the endogenous ATP pool; at the nuclear level, it inhibits RNA synthesis.
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PMID:8-chloro-cAMP and 8-chloro-adenosine act by the same mechanism in multiple myeloma cells. 1145 94

The skeleton is the most common site of metastatic disease in breast cancer and the most common site of first distant relapse. Bone metastases in breast cancer are the source of considerable morbidity, including severe pain, pathological fractures, need for radiotherapy or surgery, and hypercalcemia. Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption, and it is well known that breast cancer cells in bone can stimulate osteoclast formation and activity leading to the release of growth factors and cytokines, which will further stimulate cancer cell growth and their secretion of osteolytic factors. We are thus typically dealing with a vicious cycle, as the bone resorption-induced release of growth factors from the bone matrix will stimulate breast cancer cell growth (probably mainly by IGFs) and the production of the osteolytic factor PTHrP (probably mainly by TGF-beta but also by extracellular calcium). Clodronate, but not the aminobisphosphonates, can be metabolized to an ATP analog that is toxic for osteoclasts. Nitrogen-containing bisphosphonates, such as pamidronate, ibandronate, and zoledronate, interfere with the mevalonate pathway that is crucial to maintain cell membrane integrity. The net result, regardless of the mechanism, is osteoclast apoptosis, notably through the induction of caspase-3. Bisphosphonates are now the standard treatment for cancer hypercalcemia. Repeated bisphosphonate infusions also exert clinically relevant analgesic effects in at least one half of the patients with metastatic bone pain. Most importantly, prolonged administration of bisphosphonates (for at least 1 year) reduces the frequency of morbid skeletal events by 30-40% in breast cancer metastatic to bone and in up to 50% in patients with multiple myeloma. Newer bisphosphonates, such as ibandronate and zoledronate, will simplify the current therapeutic schemes and improve the cost-effectiveness ratio, and they have the potential to improve the therapeutic efficacy, at least in patients with aggressive osteolytic disease or in the adjuvant setting.
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PMID:Bisphosphonates in the treatment of metastatic breast cancer. 1201 36

The molecular chaperone heat shock protein 90 (Hsp90) serves essential roles in the regulation of signaling protein function, trafficking, and turnover. Hsp90 function is intimately linked to intrinsic ATP binding and hydrolysis activities, the latter of which is under the regulatory control of accessory factors. Glucose-regulated protein of 94 kDa (GRP94), the endoplasmic reticulum Hsp90, is highly homologous to cytosolic Hsp90. However, neither accessory factors nor adenosine nucleotides have been clearly implicated in the regulation of GRP94-client protein interactions. In the current study, the structural and regulatory consequences of adenosine nucleotide binding to GRP94 were investigated. We report that apo-GRP94 undergoes a time- and temperature-dependent tertiary conformational change that exposes a site(s) of protein-protein interaction; ATP, ADP, and radicicol markedly suppress this conformational change. In concert with these findings, ATP and ADP act identically to suppress GRP94 homooligomerization, as well as both local and global conformational activity. To identify a role(s) for ATP or ADP in the regulation of GRP94-client protein interactions, immunoglobulin (Ig) heavy chain folding intermediates containing bound GRP94 and immunoglobulin binding protein (BiP) were isolated from myeloma cells, and the effects of adenosine nucleotides on chaperone-Ig heavy chain interactions were examined. Whereas ATP elicited efficient release of BiP from both wild-type and mutant Ig heavy chain intermediates, GRP94 remained in stable association with Ig heavy chains in the presence of ATP or ADP. On the basis of these data, we propose that structural maturation of the client protein substrate, rather than ATP binding or hydrolysis, serves as the primary signal for dissociation of GRP94-client protein complexes.
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PMID:Adenosine nucleotides and the regulation of GRP94-client protein interactions. 1523 92

A recognition site for the cAMP-dependent protein kinase was introduced into the MAb-chCC49 by site-directed mutation of the coding sequence to make a variant of MAb-chCC49 containing a highly stable phosphate. To design this monoclonal antibody (MAb) without changing its immunoreactivity or biological properties, molecular modeling was used to locate appropriate regions for introduction of the cAMP-dependent phosphorylation site with desirable properties. We selected one position to mutate on the heavy chain based on molecular dynamics study of the solvated antibody. A vector expressing the mutant was constructed and transfected into mouse myeloma NS0 cells that expressed a high level of the resultant MAb-WW5. MAb-WW5 contained the cAMP-dependent phosphorylation site at the hinge region of the heavy chain, could be phosphorylated by the catalytic subunit of cAMP-dependent protein kinase with [gamma-32P]ATP to high specific activity, and retained the phosphate stably. Compared with MAb-chCC49K1, another phosphorylatable variant of MAb-chCC49, the phosphate attached to MAb-WW5 showed much improved stability: about a 10-fold increase in resistance to hydrolysis. MAb-WW5 exhibited the same binding specificity to the TAG-72 antigen on MCF-7 4C10 breast cancer cells as we observed with MAb-chCC49K1. The improved stability of the attached phosphate provides a MAb with potential to be used in diagnosis and therapy of adenocarcinomas.
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PMID:Design and construction of a phosphorylatable chimeric monoclonal antibody with a highly stable phosphate. 1566 96

Myeloid cell leukemia-1 (MCL-1) acts as a key survival factor for chronic lymphocytic leukemia (CLL) cells. In addition, dissipation of cellular bioenergy may impose a lethal effect on these quiescent cells. Previously, in multiple myeloma cell lines we demonstrated that halogenated adenosine (8-Cl-Ado) was phosphorylated to triphosphate (8-Cl-adenosine triphosphate [ATP]), which preferentially incorporated into mRNA and inhibited RNA synthesis by premature transcription termination. Furthermore, 8-Cl-ATP accumulation was associated with a decline in cellular bioenergy. Based on these actions, we hypothesized that 8-Cl-Ado would be ideal to target CLL lymphocytes. In the present study we demonstrate that leukemic lymphocytes incubated with 8-Cl-Ado display time- and dose-dependent increase in the accumulation of 8-Cl-ATP, with a parallel depletion of the endogenous ATP pool. Inhibition of global RNA synthesis resulted in a significant decline in the expression of transcripts with a short half-life such as MCL1. Consistent to this, protein expression of MCL-1 but not B-cell lymphoma-2 (BCL-2) was decreased. Furthermore, 8-Cl-ATP induced programmed cell death, as suggested by caspases activation, cleavage of caspase 3, and PARP (poly-adenosine diphosphate [ADP]-ribose polymerase), and increased DNA fragmentation. In conclusion, 8-Cl-Ado induces apoptosis in CLL lymphocytes by targeting cellular bioenergy as well as RNA transcription and translation of key survival genes such as MCL1.
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PMID:Cell death of bioenergetically compromised and transcriptionally challenged CLL lymphocytes by chlorinated ATP. 1571 23

Multiple myeloma is a slowly proliferating B-cell malignancy that accumulates apoptosis-resistant and replication-quiescent cell populations, posing a challenge for current chemotherapeutics that target rapidly replicating cells. Multiple myeloma remains an incurable disease in need of new therapeutic approaches. The purine nucleoside analogue, 8-amino-adenosine (8-NH2-Ado), exhibits potent activity in preclinical studies, inducing apoptosis in several multiple myeloma cell lines. This cytotoxic effect requires phosphorylation of 8-NH2-Ado to its triphosphate form, 8-amino-ATP, and results in a concomitant loss of endogenous ATP levels. Here, we show the novel effect of 8-NH2-Ado on the phosphorylation status of key cellular signaling molecules. Multiple myeloma cells treated with 8-NH2-Ado exhibit a dramatic loss of phosphorylation of several important signaling proteins, including extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and Akt kinase. Cells depleted of ATP independent of 8-NH2-Ado do not exhibit the same decrease in phosphorylation of vital cellular proteins. Therefore, the significant shifts in endogenous ATP pools caused by 8-NH2-Ado treatment cannot account for the changes in phosphorylation levels. Instead, 8-NH2-Ado may influence the activity of select regulatory protein kinases and/or phosphatases, with preliminary data suggesting that protein phophatase 2A activity is affected by 8-NH2-Ado. The distinctive effect of 8-NH2-Ado on the phosphorylation status of cellular proteins is a novel phenomenon for a nucleoside analogue drug and is unique to 8-NH2-Ado among this class of drugs. The kinetics of 8-NH2-Ado-mediated changes in phosphorylation levels of critical prosurvival and apoptosis-regulating proteins suggests that the modulation of these proteins by dephosphorylation at early time points may be an important mechanistic step in 8-NH2-Ado-induced apoptosis.
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PMID:8-Amino-adenosine induces loss of phosphorylation of p38 mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2, and Akt kinase: role in induction of apoptosis in multiple myeloma. 1582 30


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