N-WASP Control of LPAR1 Trafficking Establishes Response to Self-Generated LPA Gradients to Promote Pancreatic Cancer Cell Metastasis

Pancreatic ductal adenocarcinoma is one of the most invasive and metastatic cancers and has a dismal 5-year survival rate. We show that N-WASP drives pancreatic cancer metastasis, with roles in both chemotaxis and matrix remodeling. lysophosphatidic acid, a signaling lipid abundant in blood and ascites fluid, is both a mitogen and chemoattractant for cancer cells. Pancreatic cancer cells break lysophosphatidic acid down as they respond to it, setting up a self-generated gradient driving tumor egress. N-WASP-depleted cells do not recognize lysophosphatidic acid gradients, leading to altered RhoA activation, decreased contractility and traction forces, and reduced metastasis. We describe a signaling loop whereby N-WASP and the endocytic adapter SNX18 promote lysophosphatidic acid-induced RhoA-mediated contractility and force generation by controlling lysophosphatidic acid receptor recycling and preventing degradation. This chemotactic loop drives collagen remodeling, tumor invasion, and metastasis and could be an important target against pancreatic cancer spread.

Fam49/CYRI interacts with Rac1 and locally suppresses protrusions

Actin-based protrusions are reinforced through positive feedback, but it is unclear what restricts their size, or limits positive signals when they retract or split. We identify an evolutionarily conserved regulator of actin-based protrusion: CYRI (CYFIP-related Rac interactor) also known as Fam49 (family of unknown function 49). CYRI binds activated Rac1 via a domain of unknown function (DUF1394) shared with CYFIP, defining DUF1394 as a Rac1-binding module. CYRI-depleted cells have broad lamellipodia enriched in Scar/WAVE, but reduced protrusion-retraction dynamics. Pseudopods induced by optogenetic Rac1 activation in CYRI-depleted cells are larger and longer lived. Conversely, CYRI overexpression suppresses recruitment of active Scar/WAVE to the cell edge, resulting in short-lived, unproductive protrusions. CYRI thus focuses protrusion signals and regulates pseudopod complexity by inhibiting Scar/WAVE-induced actin polymerization. It thus behaves like a 'local inhibitor' as predicted in widely accepted mathematical models, but not previously identified in cells. CYRI therefore regulates chemotaxis, cell migration and epithelial polarization by controlling the polarity and plasticity of protrusions.

Accepting from the best donor; analysis of long-lifetime donor fluorescent protein pairings to optimise dynamic FLIM-based FRET experiments

FRET biosensors have proven very useful tools for studying the activation of specific signalling pathways in living cells. Most biosensors designed to date have been predicated on fluorescent protein pairs that were identified by, and for use in, intensity based measurements, however fluorescence lifetime provides a more reliable measurement of FRET. Both the technology and fluorescent proteins available for FRET have moved on dramatically in the last decade. Lifetime imaging systems have become increasingly accessible and user-friendly, and there is an entire field of biology dedicated to refining and adapting different characteristics of existing and novel fluorescent proteins. This growing pool of fluorescent proteins includes the long-lifetime green and cyan fluorescent proteins Clover and mTurquoise2, the red variant mRuby2, and the dark acceptor sREACh. Here, we have tested these donors and acceptors in appropriate combinations against the standard or recommended norms (EGFP and mTFP as donors, mCherry and either Ypet or Venus as acceptors) to determine if they could provide more reliable, reproducible and quantifiable FLIM-FRET data to improve on the dynamic range compared to other donors and breadth of application of biosensor technologies. These tests were performed for comparison on both a wide-field, frequency domain system and a multiphoton, TCSPC time domain FLIM system. Clover proved to be an excellent donor with extended dynamic range in combination with mCherry on both platforms, while mRuby2 showed a high degree of variability and poor FRET efficiencies in all cases. mTFP-Venus was the most consistent cyan-yellow pair between the two FLIM methodologies, but mTurquoise2 has better dynamic range and transfers energy consistently over time to the dark acceptor sRCh. Combination of mTFP-sRCh with Clover-mCherry would allow the simultaneous use of two FLIM-FRET biosensors within one sample by eliminating the crosstalk between the yellow acceptor and green donor emissions.

Periodic venting of MABR lumen allows high removal rates and high gas-transfer efficiencies

The membrane-aerated biofilm reactor (MABR) is a novel treatment technology that employs gas-supplying membranes to deliver oxygen directly to a biofilm growing on the membrane surface. When operated with closed-end membranes, the MABR provides 100-percent oxygen transfer efficiencies (OTE), resulting in significant energy savings. However, closed-end MABRs are more sensitive to back-diffusion of inert gases, such as nitrogen. Back-diffusion reduces the average oxygen transfer rates (OTR), consequently decreasing the average contaminant removal fluxes (J). We hypothesized that venting the membrane lumen periodically would increase the OTR and J. Using an experimental flow cell and mathematical modeling, we showed that back-diffusion gas profiles developed over relatively long timescales. Thus, very short ventings could re-establish uniform gas profiles for relatively long time periods. Using modeling, we systematically explored the effect of the venting interval (time between ventings). At moderate venting intervals, opening the membrane for 20 s every 30 min, the venting significantly increased the average OTR and J without substantially impacting the OTEs. When the interval was short enough, in this case shorter than 20 min, the OTR was actually higher than for continuous open-end operation. Our results show that periodic venting is a promising strategy to combine the advantages of open-end and closed end operation, maximizing both the OTR and OTE.

MSK1 regulates transcriptional induction of Arc/Arg3.1 in response to neurotrophins

The immediate early gene activity‐regulated cytoskeletal protein (Arc)/Arg3.1 and the neurotrophin brain‐derived neurotrophic factor (BDNF) play important roles in synaptic plasticity and learning and memory in the mammalian brain. However, the mechanisms by which BDNF regulates the expression of Arc/Arg3.1 are unclear. In this study, we show that BDNF acts via the ERK1/2 pathway to activate the nuclear kinase mitogen‐ and stress‐activated protein kinase 1 (MSK1). MSK1 then induces Arc/Arg3.1 expression via the phosphorylation of histone H3 at the Arc/Arg3.1 promoter. MSK1 can also phosphorylate the transcription factor cyclic‐AMP response element‐binding protein (CREB) on Ser133. However, this is not required for BDNF‐induced Arc.Arg3.1 transcription as a Ser133Ala knockin mutation had no effect on Arc/Arg3.1 induction. In parallel, ERK1/2 directly activates Arc/Arg3.1 mRNA transcription via at least one serum response element on the promoter, which bind a complex of the Serum Response Factor (SRF) and a Ternary Complex Factor (TCF).

A molecular toggle after exocytosis sequesters the presynaptic syntaxin1a molecules involved in prior vesicle fusion

Neuronal synapses are among the most scrutinized of cellular systems, serving as a model for all membrane trafficking studies. Despite this, synaptic biology has proven difficult to interrogate directly in situ due to the small size and dynamic nature of central synapses and the molecules within them. Here we determine the spatial and temporal interaction status of presynaptic proteins, imaging large cohorts of single molecules inside active synapses. Measuring rapid interaction dynamics during synaptic depolarization identified the small number of syntaxin1a and munc18-1 protein molecules required to support synaptic vesicle exocytosis. After vesicle fusion and subsequent SNARE complex disassembly, a prompt switch in syntaxin1a and munc18-1-binding mode, regulated by charge alteration on the syntaxin1a N-terminal, sequesters monomeric syntaxin1a from other disassembled fusion complex components, preventing ectopic SNARE complex formation, readying the synapse for subsequent rounds of neurotransmission.

A methodology to assess the effects of biofilm roughness on substrate fluxes using image analysis, substrate profiling, and mathematical modelling

We present a novel approach, based on image analysis and modelling, to study the impact of morphological variability (roughness) and fluid dynamics on substrate mass fluxes in biofilms. Specifically, we used this method to assess substrate fluxes in counter-diffusional autotrophic biofilms in a hydrogen-based membrane biofilm reactor. The physical structure of the biofilm was determined in situ at the meso-scale using stereomicroscopy. Image analysis was used to characterize the biofilm structure, and substrate profiles were obtained using microsensors. A two-dimensional, continuum biofilm model including microbial reactions, mass transport, and fluid dynamics was developed to compute substrate conversion in irregularly shaped counter-diffusional biofilms. Experimental biofilm structures were reproduced in the model and simulated under the prevailing substrate and hydrodynamic conditions for flow velocities varied over three orders of magnitude. Model calculations were consistent with experimental results and showed enhanced conversion rates with increased roughness at higher flow velocities. Also, modelling showed that conversion rates in counter-diffusional biofilms were typically higher than in co-diffusional biofilms. This study highlights the potential to use a simple image acquisition approach coupled to a theoretical model, to evaluate biofilm overall substrate utilization related to biofilm morphological heterogeneity.

Munc18-1 protein molecules move between membrane molecular depots distinct from vesicle docking sites

Four evolutionarily conserved proteins are required for mammalian regulated exocytosis: three SNARE proteins, syntaxin, SNAP-25, and synaptobrevin, and the SM protein, Munc18-1. Here, using single-molecule imaging, we measured the spatial distribution of large cohorts of single Munc18-1 molecules correlated with the positions of single secretory vesicles in a functionally rescued Munc18-1-null cellular model. Munc18-1 molecules were nonrandomly distributed across the plasma membrane in a manner not directed by mode of interaction with syntaxin1, with a small mean number of molecules observed to reside under membrane resident vesicles. Surprisingly, we found that the majority of vesicles in fully secretion-competent cells had no Munc18-1 associated within distances relevant to plasma membrane-vesicle SNARE interactions. Live cell imaging of Munc18-1 molecule dynamics revealed that the density of Munc18-1 molecules at the plasma membrane anticorrelated with molecular speed, with single Munc18-1 molecules displaying directed motion between membrane hotspots enriched in syntaxin1a. Our findings demonstrate that Munc18-1 molecules move between membrane depots distinct from vesicle morphological docking sites.

Secretory vesicles are preferentially targeted to areas of low molecular SNARE density

Intercellular communication is commonly mediated by the regulated fusion, or exocytosis, of vesicles with the cell surface. SNARE (soluble N-ethymaleimide sensitive factor attachment protein receptor) proteins are the catalytic core of the secretory machinery, driving vesicle and plasma membrane merger. Plasma membrane SNAREs (tSNAREs) are proposed to reside in dense clusters containing many molecules, thus providing a concentrated reservoir to promote membrane fusion. However, biophysical experiments suggest that a small number of SNAREs are sufficient to drive a single fusion event. Here we show, using molecular imaging, that the majority of tSNARE molecules are spatially separated from secretory vesicles. Furthermore, the motilities of the individual tSNAREs are constrained in membrane micro-domains, maintaining a non-random molecular distribution and limiting the maximum number of molecules encountered by secretory vesicles. Together our results provide a new model for the molecular mechanism of regulated exocytosis and demonstrate the exquisite organization of the plasma membrane at the level of individual molecular machines.

MSK1 regulates homeostatic and experience-dependent synaptic plasticity

The ability of neurons to modulate synaptic strength underpins synaptic plasticity, learning and memory, and adaptation to sensory experience. Despite the importance of synaptic adaptation in directing, reinforcing, and revising the behavioral response to environmental influences, the cellular and molecular mechanisms underlying synaptic adaptation are far from clear. Brain-derived neurotrophic factor (BDNF) is a prime initiator of structural and functional synaptic adaptation. However, the signaling cascade activated by BDNF to initiate these adaptive changes has not been elucidated. We have previously shown that BDNF activates mitogen- and stress-activated kinase 1 (MSK1), which regulates gene transcription via the phosphorylation of both CREB and histone H3. Using mice with a kinase-dead knock-in mutation of MSK1, we now show that MSK1 is necessary for the upregulation of synaptic strength in response to environmental enrichment in vivo. Furthermore, neurons from MSK1 kinase-dead mice failed to show scaling of synaptic transmission in response to activity deprivation in vitro, a deficit that could be rescued by reintroduction of wild-type MSK1. We also show that MSK1 forms part of a BDNF- and MAPK-dependent signaling cascade required for homeostatic synaptic scaling, which likely resides in the ability of MSK1 to regulate cell surface GluA1 expression via the induction of Arc/Arg3.1. These results demonstrate that MSK1 is an integral part of a signaling pathway that underlies the adaptive response to synaptic and environmental experience. MSK1 may thus act as a key homeostat in the activity- and experience-dependent regulation of synaptic strength.

Vitamin D supplementation in CKD

Vitamin D deficiency is common in chronic kidney disease and is associated with increased morbidity and mortality. In addition, vitamin D deficiency in renal disease is associated with serious comorbidities including secondary hyperparathyroidism and cardiovascular disease. Several therapeutic options are available to correct vitamin D deficiency, including nutritional vitamin D, pro-hormones and active hormones. In this review we discuss clinical findings related to the effectiveness of these therapies in chronic kidney disease.

The new kidney disease: improving global outcomes (KDIGO) guidelines - expert clinical focus on bone and vascular calcification

Chronic kidney disease-mineral and bone disorder (CKD-MBD) defines a triad of interrelated abnormalities of serum biochemistry, bone and the vasculature associated with chronic kidney disease (CKD). The new kidney disease: improving global outcomes (KDIGO) guidelines define the quality and depth of evidence supporting therapeutic intervention in CKD-MBD. They also highlight where patient management decisions lack a strong evidence base. Expert interpretation of the guidelines, along with informed opinion, where evidence is weak, may help develop effective clinical practice. The body of evidence linking poor bone health and reservoir function (the ability of bone to buffer calcium and phosphorus) with vascular calcification and cardiovascular outcomes is growing. Treating renal bone disease should be one of the primary aims of therapy for CKD. Evaluation of the biochemical parameters of CKD-MBD (primarily phosphorus, calcium, parathyroid hormone and vitamin D levels) as early as CKD Stage 3, and an assessment of bone status (by the best means available), should be used to guide treatment decisions. The adverse effects of high phosphorus intake relative to renal clearance (including stimulation of hyperparathyroidism) precede hyperphosphatemia, which presents late in CKD. Early reduction of phosphorus load may ameliorate these adverse effects. Evidence that calcium load may influence progression of vascular calcification with effects on mortality should also be considered when choosing the type and dose of phosphate binder to be used. The risks, benefits, and strength of evidence for various treatment options for the abnormalities of CKD-MBD are considered.

Generation of a conditional CREB Ser133Ala knockin mouse

Phosphorylation of Ser133 in the transcription factor CREB is an important mechanism for regulating its transcriptional activity, however recent work has suggested significant roles for other regulatory inputs into CREB. To allow study of this in vivo, we have generated a Ser133 to alanine knockin mutation in the mouse CREB locus. As CREB knockout is perinatal lethal, a minigene strategy was used to allow conditional knockin of the Ser133Ala mutation in adult mice using Cre recombinase. While some expression of the mutated protein was observed prior to Cre expression, following Cre expression in either T cells or neurons only the mutated CREB protein was detected.

Quasi-steady-state displacement response of whole human cadaveric knees in a MRI scanner

It is important to determine the three-dimensional nonuniform deformation of articular cartilage in its native environment. A new magnetic resonance imaging (MRI)-based technique (cartilage deformation by tag registration (CDTR)) has been developed, which can determine such deformations provided that the compressive load-displacement response of the knee reaches a quasi-steady state during cyclic loading. The objectives of this study were (1) to design and construct an apparatus to cyclically compress human cadaveric knees to physiological loads in a MRI scanner, (2) to determine the number of load cycles required to reach a quasi-steady-state load-displacement response for cyclic loading of human cadaveric knees, and (3) to collect sample MR images of undeformed and deformed states of tibiofemoral cartilage free of artifact while using the apparatus within a MRI scanner. An electropneumatic MRI-compatible apparatus was constructed to fit in a clinical MRI scanner, and a slope criterion was defined to indicate the point at which a quasi-steady-state load-displacement response, which would allow the use of CDTR, occurred during cyclic loading of a human knee. The average number of cycles required to reach a quasi-steady-state load-displacement response according to the slope criterion defined herein for three cadaveric knee joints was 356+/-69. This indicates that human knee joint specimens can be cyclically loaded such that deformation is repeatable according to MRI requirements of CDTR. Sample images of tibiofemoral cartilage were obtained for a single knee joint. These images demonstrate the usefulness of the apparatus in a MRI scanner. Thus the results of this study are a crucial step toward developing a MRI-based method to determine the deformations of articular cartilage in whole human cadaveric knees.

Evidence of specialized bromate-reducing bacteria in a hollow fiber membrane biofilm reactor

Bromate is a carcinogenic disinfection by-product formed from bromide during ozonation or advanced oxidation. We previously observed bromate reduction in a hydrogen-based, denitrifying hollow fiber membrane biofilm reactor (MBfR). In this research, we investigated the potential existence of specialized bromate-reducing bacteria. Using denaturing gradient gel electrophoresis (DGGE), we compared the microbial ecology of two denitrifying MBfRs, one amended with nitrate as the electron acceptor and the other with nitrate plus bromate. The DGGE results showed that bromate exerted a selective pressure for a putative, specialized bromate-reducing bacterium, which developed a strong presence only in the reactor with bromate. To gain further insight into the capabilities of specialized, bromate-reducing bacteria, we explored bromate reduction in a control MBfR without any primary electron acceptors. A grown biofilm in the control MBfR reduced bromate without previous exposure, but the rate of reduction decreased over time, especially after perturbations resulting in biomass loss. The decrease in bromate reduction may have been the result of the toxic effects of bromate. We also used batch tests of the perchlorate-reducing pure culture, Dechloromonas sp. PC1 to test bromate reduction and growth. Bromate was reduced without measurable growth. Based on these results, we speculate bromate's selective pressure for the putative, specialized BRB observed in the DGGE was not growth related, but possibly based on resistance to bromate toxicity.

An MRI-based method to align the compressive loading axis for human cadaveric knees

There is a need to align the mechanical axis of the tibia with the axis of loading for studies involving tibiofemoral compression to interpret results and to ensure repeatability of loading within and among specimens. Therefore, the objectives of this study were (1) to develop a magnetic resonance imaging (MRI)-based alignment method for use with apparatuses applying tibiofemoral joint compression, (2) to demonstrate the usefulness of the method by aligning cadaveric knees in an apparatus that could apply tibiofemoral joint compression, and (3) to quantify the error associated with the alignment method. A four degree-of-freedom adjustable device was constructed to allow determination and alignment of the mechanical axis of the tibia of cadaveric knee joints with the axis of loading of an apparatus applying tibiofemoral joint compression. MRI was used to determine the locations of bony landmarks in three dimensions defining the mechanical axis of the tibia relative to an initial orientation of the four degree-of-freedom device. Adjustment values of the device were then computed and applied to the device to align the mechanical axis of the tibia with the axis of a compressive loading apparatus. To demonstrate the usefulness of the method, four cadaveric knees were aligned in the compressive loading apparatus. The vectors describing the mechanical axis of the tibia and the loading axis of the apparatus before and after adjustment of the four degree-of-freedom device were computed for each cadaveric knee. After adjustment of the four degree-of-freedom device, the mechanical axis of the tibia was collinear with the loading axis of the apparatus for each cadaveric knee. The errors in the adjustment values introduced by inaccuracies in the MR images were quantified using the Monte Carlo technique. The precisions in the translational and rotational adjustments were 1.20 mm and 0.90 deg respectively. The MR-based alignment method will allow consistent interpretation of results obtained during tibiofemoral compressive studies conducted using the apparatus described in this paper by providing a well-defined loading axis. The alignment method can also be adapted for use with other apparatuses applying tibiofemoral compression.

The first human cell line-derived erythropoietin, epoetin-? (Dynepo®), in the management of anemia in patients with chronic kidney disease

AIMS

To evaluate the efficacy and safety of the first human cell line-derived erythropoietin, epoetin-delta, in the management of anemia in patients with chronic kidney disease.

METHODS

This was a multicenter, randomized, double-blind, parallel-group, active-control, Phase III study. Patients aged > or = 18 years with chronic renal disease requiring hemodialysis, with hemoglobin (Hb) levels in the range 9.6-12.4 g/dl, and who had been treated with recombinant erythropoietin for > or = 90 days before study entry were eligible. In the initial double-blind comparative study phase, patients were randomized in a 3:1 ratio to 24-week treatment with either intravenous (i.v.) epoetin-delta (ED) or epoetin-alpha (EA). Patients then entered a 28-week open-label phase, receiving i.v. ED at a dose equal to that of i.v. ED or EA which they received at the end of the blinded phase.

RESULTS

In total, 752 patients were randomized, of whom 555 patients subsequently received ED and 191 patients EA, with 583 patients (77.5%) completing the double-blind phase and entering the open-label phase. There was no significant difference between groups for the primary endpoint: the average Hb level from Weeks 12-24 of the study. The adjusted mean average Hb level for the modified intent-to-treat (mITT) population was 11.57 g/dl in the ED group (n = 491, mean dose 63.5 IU/kg) and 11.56 g/dl in the EA group (n = 175, mean dose 62.8 IU/kg). Efficacy was maintained on long-term use. Data for Weeks 12-52 show that ED maintained patients' Hb levels in the target range (10-12 g/dl) with a mean Hb level of 11.31 g/dl at a mean ED dose of 63.7 IU/kg. ED therapy was well tolerated, with a similar overall incidence of adverse events (AEs) (94.4%) to the EA group (92.1%) in the double-blind phase (most common events: hypotension, upper respiratory tract infection, muscle cramps, headache). AEs occurring during the open-label phase were generally similar in type and frequency to those reported during the double-blind phase.

CONCLUSIONS

The human cell line-derived erythropoietin, epoetin-delta, provides an effective, well tolerated new option for the management of anemia in patients with chronic kidney disease.

Detection of cognitive decline after coronary surgery: a comparison of computerized and conventional tests

BACKGROUND

Postoperative cognitive decline is a common complication after coronary artery bypass graft (CABG) surgery. Postoperative cognitive decline is defined on the basis of change in cognitive function detected with repeated assessments using neuropsychological tests. Therefore improvement in neuropsychological testing instruments may increase our understanding of postoperative cognitive decline.

METHODS

Fifty patients undergoing CABG surgery completed both a conventional and a computerized battery of tests before and 6 days after CABG surgery. Fifty age- and education-matched controls completed the same test batteries 6 days apart. The reliability and the sensitivity to postoperative cognitive decline were computed for each battery.

RESULTS

Both test batteries detected postoperative cognitive decline 6 days after CABG surgery. For the computerized battery, the reliability of the reaction times (intraclass correlation 0.89-0.92) was greater than for any test from the conventional battery (intraclass correlation 0.56-0.71), although accuracy measures were less reliable (intraclass correlation 0.61-0.89). The computerized battery detected all the cases of POCD identified by the conventional test battery and also five cases that were classified as normal by the conventional tests.

CONCLUSION

Computerized tests are suitable for measuring cognitive change after CABG surgery and may detect change in a greater proportion of patients 6 days after CABG surgery than conventional neuropsychological tests.

Soluble IL-6 receptor levels in patients on chronic hemodialysis

Osteitis fibrosa, a part of the spectrum of renal osteodystrophy, is characterized by high bone turnover as a result of high circulating levels of parathyroid hormone (PTH). It is well accepted that the bone resorptive effects of PTH occur, at least in part, by inducing osteoblasts to secrete cytokines that stimulate both differentiation and activation of osteoclasts. One such cytokine, interleukin 6 (IL-6), exerts its actions via the IL-6 receptor (IL-6R), which has alpha and beta subunits. The alpha subunit binds IL-6 and exists in both membrane bound and soluble forms which can interact with the signal transducing components of the receptor or beta subunits and result in the same biological effect. Abnormalities in the IL-6 system have the potential to affect bone turnover and to modulate the effects of PTH. In this regard, we examined the levels of circulating soluble IL-6 receptor (sIL-6R) and plasma intact PTH in 27 patients on hemodialysis, of whom 15 were on therapy with vitamin D compounds and 12 were vitamin D naive. The results were compared to values obtained from 9 healthy controls. Blood samples were obtained pre-dialysis and sIL-6R levels were determined using a commercially available enzyme immunoassay, which measures biologically active sIL-6R. In patients on chronic hemodialysis, plasma levels of sIL-6R were 123.4 +/- 11.01 ng/ml. In healthy controls, the levels were 99.61 +/- 11.52 ng/ml, values not significantly different from those found in dialysis patients. PTH values ranged from 7-1,709 pg/ml in patients on hemodialysis; however, there was no correlation between intact PTH levels and the levels of sIL-6R. Similarly, vitamin D therapy did not influence the levels of sIL-6R. These data indicate that using an assay which is specific for biologically active sIL-6R, the levels of this receptor in patients on hemodialysis are similar to those found in normal individuals and neither the levels of PTH nor vitamin D therapy alter this aspect of IL-6 action.

Mechanism of retinoic acid induced attenuation of PTH action in UMR 106-01 cells

Studies from our laboratory in osteoblast-like cells have shown that the increase in EGF receptor expression in response to PTH was cyclic AMP mediated and was blocked by treatment with retinoic acid (RA). The present studies investigate the mechanism for this effect of RA on PTH actions. UMR 106-01 cells were exposed to RA and were tested for cAMP response to PTH as well as for (125)I PTH binding. cAMP production in response to PTH was markedly decreased by RA (25.1 +/- 1.6% of control) whereas there was only a slight decrease in PTH binding in response to RA. For the study of adenylate cyclase activity, membranes were isolated from intact cells that had been exposed to RA. Treatment with RA decreased PTH-stimulated adenylate cyclase activity; however, forskolin-stimulated enzyme activity was unchanged. Treatment of intact cells with pertussis toxin, to inactivate Gi, did not alter the inhibitory effect of RA on PTH-stimulated adenylate cyclase activity. Addition of GppNHp, a non-hydrolyzable analogue of GTP, completely restored the response to PTH in the membranes. Therefore, we examined the activity of IMP dehydrogenase, the rate-limiting enzyme for GTP biosynthesis, and GMP reductase which counteracts the effect of the synthetic enzyme. Treatment with RA for 48 hours increased GMP reductase activity by 240.9 +/- 24.2% and decreased IMP dehydrogenase activity to 67.5 +/- 8.8% of control values. These data indicate that RA impairs the response to PTH in intact cells. This blunted response was preserved in membrane preparations but was corrected by GTP. The RA-induced alterations of enzymes involved in the GTP biosynthetic pathway in a direction that favors a decrease in GTP biosynthesis provide an explanation for the inhibitory effect of RA on PTH actions.

Strategies to minimize bone disease in renal failure

The skeletal disorders associated with renal insufficiency result from alterations in calcium, phosphorus, and vitamin D metabolism. Each requires intervention to prevent and control the problem. Hyperparathyroidism and its treatment can also result in extraskeletal complications. To prevent the development of parathyroid hyperplasia and the skeletal complications of chronic kidney disease, it is desirable to initiate interventions early in the course of kidney disease; however, many patients present with established hyperparathyroidism and additional strategies are necessary to suppress hyperparathyroidism. Mainstays of this approach are the control of phosphorus and the use of vitamin D analogs. Phosphorus control requires the use of phosphate binders, preferably non-calcium-containing binders, to prevent intestinal phosphorus absorption. Vitamin D analogs are used to suppress hyperparathyroidism and have the potential to have lesser toxicity than calcitriol. Paricalcitol is the most widely used vitamin D analog in this country and it effectively suppresses hyperparathyroidism with only minimal effects on calcium and phosphorus. A substantial body of data in experimental animals supports the use of paricalcitol as a preferential therapeutic agent. Recently, an additional vitamin D sterol, doxercalciferol, has been introduced, which is metabolized to 1,25-dihydroxyvitamin D(2). Although initially thought to have lesser toxicity than its vitamin D(3) counterpart, recent studies have not provided support for a major difference in this regard. Doxercalciferol is also effective in lowering parathyroid hormone (PTH), though hypercalcemia in hyperphosphatemic episodes occurred relatively frequently during the clinical studies. As these therapeutic strategies are undertaken, it is important not to oversuppress PTH and decrease bone turnover to abnormally low levels because of the risk for adynamic renal bone disease. It is possible that when bone turnover is abnormally low, the extraskeletal deposition of calcium in blood vessels and other tissues is enhanced. Accordingly, constant monitoring is required during treatment, with emphasis on minimizing the calcium load, and, if monitored correctly, a satisfactory control of hyperparathyroidism may be achieved with the agents currently available.

Vitamin D analogues for the management of secondary hyperparathyroidism

Secondary hyperparathyroidism complicating chronic kidney disease requires therapy to minimize the effects of parathyroid hormone (PTH) on bone and other tissues. Low levels of calcitriol in blood play a major role in the initiation and maintenance of hyperparathyroidism. Accordingly, administration of calcitriol has been demonstrated to be an effective form of therapy. While this therapy is effective in controlling hyperparathyroidism, side effects of calcitriol, including increased intestinal absorption of calcium and phosphate, often complicate therapy by giving rise to hypercalcemia and hyperphosphatemia, which may be important risk factors for extraskeletal calcifications. Over the last several years, interest has turned toward vitamin D analogs, which may be able to affect parathyroid function with lesser effects on calcium and phosphorus in serum, and thereby, minimizing the undesirable toxicities of vitamin D therapy. Two vitamin D analogs are available in this country for the control of hyperparathyroidism in the setting of advanced kidney disease, and include 19-nor-1,25-dihydroxyvitamin D(2) (paricalcitol), and more recently, 1-alpha-hydroxyvitamin D(2) (doxercalciferol). 19-nor-1,25-dihydroxyvitamin D(2) is widely used and was evaluated extensively in animals, revealing that this vitamin D sterol had a selective effect on increasing PTH suppression, with lesser effects on calcium and phosphorus metabolism. These studies lead to clinical trials which showed the efficacy of this therapy in that PTH could be lowered satisfactorily in patients with calcium and phosphorus values within the normal range. The selectivity of 19-nor-1,25-dihydroxyvitamin D(2) seen in animals has also been found in humans, such that therapy with this sterol can achieve control of hyperparathyroidism with a wider therapeutic window than the predecessor, calcitriol. 1-alpha-hydroxyvitamin D(2) has recently been introduced, but in contrast to paracalcitol, there is little reason to believe that there is any selectivity in its actions in terms of suppressing PTH, compared with its ability to raise serum calcium or phosphorus in serum. However, this vitamin D sterol can effectively decrease PTH levels in patients with advanced renal failure. Comparative studies of paricalcitol and doxercalciferol have not been undertaken at the present time. Further studies on the mechanism of actions might explain the differences between these sterols and their effects on the intestinal absorption of calcium and phosphate. At the present, the use of vitamin D analogs can achieve control of hyperparathyroidism with a wider therapeutic window than the native sterol, calcitriol.

Paricalcitol dosing according to body weight or severity of hyperparathyroidism: a double-blind, multicenter, randomized study

Vitamin D therapy for patients with end-stage renal disease (ESRD) on hemodialysis therapy has relied on patient dry weight to determine the initial dose of medication. Obtaining a patient's dry weight can be difficult, and no correlation has been established between a patient's body weight and severity of secondary hyperparathyroidism. We conducted a double-blind, double-dummy, randomized, 12-week, multicenter trial to compare the incidence of hypercalcemia (single occurrence) between two dosing regimens: one regimen based on baseline intact parathyroid hormone (iPTH; PTH/80) level, and the other regimen based on patient body weight (0.04 microgram/kg). One hundred twenty-five adult patients with ESRD on maintenance hemodialysis therapy were enrolled at multiple sites. Before treatment, all patients were required to have PTH levels of 300 pg/mL or greater, calcium levels of 8.0 mg/dL or greater and 10.5 mg/dL or less, and a calcium x phosphorus (Ca x P) product of 70 or less. Patients were randomized to one of two regimens: the nonrandomized treatment was also administered as a placebo dummy. No incidence of hypercalcemia occurred in either treatment group during the study. Patients treated according to the formula iPTH/80 required fewer dose adjustments and achieved the first of four consecutive reductions from baseline PTH level of 30% or greater more rapidly than patients treated based on body weight (P = 0.0306). Incidences of elevated Ca x P product levels were similar between treatment groups. Treatment with paricalcitol injection based on degree of secondary hyperparathyroidism incurred no greater risk for hypercalcemia and achieved meaningful therapeutic results with fewer dose adjustments than dosing based on patient body weight.

A long-term, multicenter study of the efficacy and safety of paricalcitol in end-stage renal disease

BACKGROUND

Paricalcitol is a vitamin D analog approved for the prevention and treatment of secondary hyperparathyroidism associated with chronic renal failure. This study was designed to evaluate the long-term efficacy and safety of paricalcitol. Additional analysis evaluated the effects of paricalcitol in hypocalcemic and hyperphosphatemic subpopulations.

PATIENTS AND METHODS

One hundred sixty-four end-stage renal disease (ESRD) patiesnts on hemodialysis were treated in an open-label, multicenter study lasting up to 13 months in duration. After a baseline or washout period, an initial starting dose of 0.04-0.393 microg/kg was given 2-3 times per week. This dose was adjusted at the discretion of the investigator according to the patient's intact parathyroid hormone level (iPTH), calcium level, and calcium-phosphorus (Ca x P) product. The therapy was intended to reproduce expected clinical use of paricalcitol. Patients represented a wide cross-section of the ESRD population, and were not excluded from the study based on age or underlying disease.

RESULTS

The mean paricalcitol dose level throughout the study was 0.10 microg/kg. The mean iPTH levels (baseline mean 628.3 +/- 27.65 pg/ml) decreased rapidly during the first 4 months of therapy, and reached the designated target range (100-300 pg/ml) by month 5 (mean 295.3 +/- 25.69 pg/ml). A maximum mean decrease in iPTH level of 409 +/- 35.01 pg/ml was seen at month 13. Throughout the course of the study, the mean normalized calcium level was maintained well within the normal range (9.44-9.94 mg/dl). The mean phosphorus level was maintained in an acceptable range throughout the study (5.92-6.53 mg/dl). Mean Ca x P product was maintained between 52 and 65. Mean alkaline phosphatase levels decreased significantly from baseline with a maximum mean decrease of 62 +/- 17.3 U/l observed at month 9. In 34 initially hypocalcemic patients (mean of 7.7 mg/dl) iPTH levels decreased from baseline, on average, by 443 +/- 81.86 pg/ml while mean calcium levels rose by 1.2 +/- 0.23 mg/dl to reach the normal range. In 35 initially hyperphosphatemic patients (mean of 8.0 mg/dl) iPTH levels decreased, on average, by 515 +/- 103.31 pg/ml with an associated mean decrease in phosphorus of 0.57 +/- 0.52 mg/dl. Adverse events that were considered by the investigator to have a possible. probable, or definite relationship to study drug occurred in 26% of patients. Other than expected temporary effects of hypercalcemia and hyperphosphatemia. the only possible trends for causally-related adverse events were for nausea/vomiting and metallic taste.

CONCLUSIONS

This long-term study of paricalcitol demonstrates that it rapidly and effectively suppresses iPTH levels in a wide spectrum of ESRD patients and caused no unexpected adverse events.

The evolution of assays for parathyroid hormone

Recent progress in the assay of parathyroid hormone has revealed that commercially available assays for intact parathyroid hormone also measure additional parathyroid hormone peptides that appear to be truncated at the amino-terminal region and have the elution position on high-performance liquid chromatography of parathyroid hormone 7-84. Specific assays have been developed that measure only the true or 'whole', 84-amino-acid peptide. Such 'whole' parathyroid hormone assays have led to the discovery of new findings that suggest that parathyroid hormone fragments such as parathyroid hormone 7-84, which have hitherto been considered to be biologically inactive, may actually have biologic effects. These data, coupled with the emerging discovery of additional receptors for parathyroid hormone peptides, suggest that parathyroid hormone fragments might have potentially important actions, at least in the setting of renal failure.

Site-specific phosphorylation of human p53 protein determined by mass spectrometry

Human recombinant p53 (r-p53) protein was studied by mass spectrometry (MS) to determine site-specific posttranslational differences between basal and hyperphosphorylated r-p53. Wild-type p53 was basally expressed after baculovirus infection while a parallel preparation was treated with the phosphatase inhibitor okadaic acid during the terminal stages of expression to create a hyperphosphorylated form of p53 known for its higher DNA binding and transcriptional activation. After immunoaffinity and HPLC purification, MALDI/MS measured a higher molecular mass for r-p53 from okadaic acid treatment relative to control, suggesting a higher phosphorylation state. This was supported by an acidic shift of r-p53 isoforms separated by gel isoelectric focusing. Employing a variety of mass spectrometric analyses combined with separation and affinity techniques, six specific phosphorylation sites of p53 were identified. The MS data indicated that hyperphosphorylated p53 showed a higher degree of phosphorylation than basal p53 at specific amino- and carboxy-terminal sites. In particular, ESI-MS demonstrated that Ser(315) was entirely phosphorylated after okadaic acid treatment, as confirmed biochemically by CDK2 kinase assay and by isoelectric focusing. In summary, MS analysis uniquely revealed increased, site-specific phosphorylations on p53 after phosphatase inhibition, particularly at Ser(315), which may be critical molecular events in defining p53 activity.

High-sensitivity array analysis of gene expression for the early detection of disseminated breast tumor cells in peripheral blood

Early detection is an effective means of reducing cancer mortality. Here, we describe a highly sensitive high-throughput screen that can identify panels of markers for the early detection of solid tumor cells disseminated in peripheral blood. The method is a two-step combination of differential display and high-sensitivity cDNA arrays. In a primary screen, differential display identified 170 candidate marker genes differentially expressed between breast tumor cells and normal breast epithelial cells. In a secondary screen, high-sensitivity arrays assessed expression levels of these genes in 48 blood samples, 22 from healthy volunteers and 26 from breast cancer patients. Cluster analysis identified a group of 12 genes that were elevated in the blood of cancer patients. Permutation analysis of individual genes defined five core genes (P < or = 0.05, permax test). As a group, the 12 genes generally distinguished accurately between healthy volunteers and patients with breast cancer. Mean expression levels of the 12 genes were elevated in 77% (10 of 13) untreated invasive cancer patients, whereas cluster analysis correctly classified volunteers and patients (P = 0.0022, Fisher's exact test). Quantitative real-time PCR confirmed array results and indicated that the sensitivity of the assay (1:2 x 10(8) transcripts) was sufficient to detect disseminated solid tumor cells in blood. Expression-based blood assays developed with the screening approach described here have the potential to detect and classify solid tumor cells originating from virtually any primary site in the body.

Inactivation of DNA mismatch repair by increased expression of yeast MLH1

Inactivation of DNA mismatch repair by mutation or by transcriptional silencing of the MLH1 gene results in genome instability and cancer predisposition. We recently found (P. V. Shcherbakova and T. A. Kunkel, Mol. Cell. Biol. 19:3177-3183, 1999) that an elevated spontaneous mutation rate can also result from increased expression of yeast MLH1. Here we investigate the mechanism of this mutator effect. Hybridization of poly(A)(+) mRNA to DNA microarrays containing 96.4% of yeast open reading frames revealed that MLH1 overexpression did not induce changes in expression of other genes involved in DNA replication or repair. MLH1 overexpression strongly enhanced spontaneous mutagenesis in yeast strains with defects in the 3'-->5' exonuclease activity of replicative DNA polymerases delta and epsilon but did not enhance the mutation rate in strains with deletions of MSH2, MLH1, or PMS1. This suggests that overexpression of MLH1 inactivates mismatch repair of replication errors. Overexpression of the PMS1 gene alone caused a moderate increase in the mutation rate and strongly suppressed the mutator effect caused by MLH1 overexpression. The mutator effect was also reduced by a missense mutation in the MLH1 gene that disrupted Mlh1p-Pms1p interaction. Analytical ultracentrifugation experiments showed that purified Mlh1p forms a homodimer in solution, albeit with a K(d) of 3.14 microM, 36-fold higher than that for Mlh1p-Pms1p heterodimerization. These observations suggest that the mismatch repair defect in cells overexpressing MLH1 results from an imbalance in the levels of Mlh1p and Pms1p and that this imbalance might lead to formation of nonfunctional mismatch repair complexes containing Mlh1p homodimers.

The effect of vitamin E and vitamin C supplementation on LDL oxidizability and neutrophil respiratory burst in young smokers

OBJECTIVE

The purpose of this study was to determine the effect of vitamin E and/or vitamin C supplementation on low-density lipoprotein (LDL) oxidizability and neutrophil (PMN) superoxide anion production in young smokers.

METHODS

Thirty smokers with a <5 pack-year history were randomly assigned to take placebo; vitamin C (1 g/day); vitamin E (400 IU/day), or both vitamins in a double-blind fashion. Subjects took the supplements for 8 weeks. At weeks 0 and 8, blood was collected for isolation of LDL and PMN, and for antioxidant vitamin analysis. LDL was oxidized with a copper (Cu) catalyst, and oxidation was measured by formation of conjugated dienes over a 5-hour time course. Lag times and maximum oxidation rates were calculated from the time course data. PMN superoxide anion release was assessed by respiratory burst after stimulation with phorbol ester and opsonized zymosan, and their ability to oxidize autologous LDL following treatment with the above stimuli was measured with the conjugated diene assay.

RESULTS

Subjects who received vitamin E alone had a significant increase in the lag phase of Cu-catalyzed LDL oxidation (week 0, 118+/-31 min vs. week 8, 193+/-80 min, mean +/- SD, p < 0.05), whereas the vitamin C and placebo groups had no changes in LDL oxidation kinetics. The group receiving both vitamins E and C had a significant reduction in oxidation rate (week 0. 7.4+/-2.3 vs. week 8, 5.1+/-2.1, p < 0.05). There were no significant changes for any group in PMN superoxide anion production or PMN LDL oxidation after stimulation with either phorbol ester or opsonized zymosan. Plasma and LDL vitamin E concentrations were significantly increased in both groups that received vitamin E. The subjects who received vitamin C alone had no significant change in plasma vitamin C concentrations; however, when data were pooled from both groups who received vitamin C, the increases were significant.

CONCLUSION

Vitamin E supplementation of young smokers was effective in reducing Cu-catalyzed LDL oxidizability; however, vitamin E and/or C supplementation showed few significant effects on the more physiologically relevant PMN function. This casts doubt on the ability of antioxidant supplementation to reduce oxidative stress in smokers in vivo. Therefore, smoking cessation remains the only means by which young smokers can prevent premature coronary heart disease.

Linking gene expression patterns to therapeutic groups in breast cancer

A major objective of current cancer research is to develop a detailed molecular characterization of tumor cells and tissues that is linked to clinical information. Toward this end, we have identified approximately one-quarter of all genes that were aberrantly expressed in a breast cancer cell line using differential display. The cancer cells lost the expression of many genes involved in cell adhesion, communication, and maintenance of cell shape, while they gained the expression of many synthetic and metabolic enzymes important for cell proliferation. High-density, membrane-based hybridization arrays were used to study mRNA expression patterns of these genes in cultured cells and archived tumor tissue. Cluster analysis was then used to identify groups of genes, the expression patterns of which correlated with clinical information. Two clusters of genes, represented by p53 and maspin, had expression patterns that strongly associated with estrogen receptor status. A third cluster that included HSP-90 tended to be associated with clinical tumor stage, whereas a forth cluster that included keratin 14 tended to be associated with tumor size. Expression levels of these clinically relevant gene clusters allowed breast tumors to be grouped into distinct categories. Gene expression fingerprints that include these four gene clusters have the potential to improve prognostic accuracy and therapeutic outcomes for breast cancer patients.

Therapy of secondary hyperparathyroidism with 19-nor-1alpha,25-dihydroxyvitamin D2

Secondary hyperparathyroidism contributes to significant morbidity in patients with chronic renal failure. The treatment of this disorder with vitamin D compounds, such as calcitriol, although effective at suppressing parathyroid hormone (PTH) secretion, may promote the development of hypercalcemia and hyperphosphatemia, thus increasing the risk for metastatic calcification. A new vitamin D analogue, 19-nor-1alpha,25-(OH)2D2 (paricalcitol; Zemplar, Abbott Laboratories, Inc, Chicago, IL) has recently been developed for the treatment of secondary hyperparathyroidism, and, in experimental animals, it was found to be less calcemic and phosphatemic than calcitriol. In double-blind clinical trials, paricalcitol effectively decreased the levels of PTH by 60%, yet the mean serum calcium values remained within the normal range. The few episodes of hypercalcemia that occurred in the paricalcitol-treated patients (8 of 400 determinations > or =11.0 mg/dL in 7 patients) were associated with marked decreases in PTH levels (87% +/- 2% less than baseline) and absolute values of PTH less than 100 pg/mL in four of the seven patients. PTH values less than 100 pg/mL, however, occurred in 15 patients, but were not invariably associated with frank hypercalcemia, although serum calcium levels increased to 10.63 +/- 0.3 mg/dL, slightly greater than the upper limits of normal. Additional studies to evaluate the conversion from calcitriol to paricalcitol therapy showed that a dose ratio of 1:4 (calcitriol:paricalcitol) could maintain control of high levels of PTH without significant alterations in serum calcium and phosphorus levels. These studies indicate that effective control of hyperparathyroidism can be achieved with paricalcitol therapy with minimal perturbation of serum calcium and phosphorus levels, and may have a therapeutic advantage over current treatment strategies.

Down-regulation of laminin-5 in breast carcinoma cells

BACKGROUND

Laminin-5 (ln-5), a large heterotrimeric glycoprotein consisting of an alpha 3, beta 3, and gamma 2 chain, is a component of epithelial cell basement membranes that functions as a ligand of the alpha 3 beta 1 and alpha 6 beta 4 integrins to regulate cell adhesion, migration, and morphogenesis. The ln-5 chains show tissue-specific patterns of regulation in tumors derived from different tissues. For example, ln-5 is often up-regulated in gliomas, gastric carcinomas, and squamous carcinomas and down-regulated in prostate and basal cell carcinomas. Ln-5 expression patterns may represent useful tumor markers and help to elucidate the role of ln-5 in tumor progression in different tissue types.

MATERIALS AND METHODS

We have studied ln-5 expression patterns in the breast. mRNA levels were examined in tumor and normal breast epithelial cell lines, tissue samples, and immunomagnetically sorted primary cultures using differential display, Northern blotting, and hybridization arrays. Protein levels were examined by immunoprecipitation. Gene integrity was assessed by Southern blotting of representative cell types.

RESULTS

Ln-5 alpha 3, beta 3, and gamma 2 mRNA expression was found to be markedly down-regulated in a panel of breast tumor cell lines when compared with normal breast epithelial cells. Ln-5 mRNA was expressed at relatively high levels in MCF-10A immortal normal breast epithelial cells, long-term cultures of normal breast cells, and sorted primary cultures of normal breast luminal epithelial and myoepithelial cells. Reduced, but detectable, levels of ln-5 tended to be expressed in cell lines derived from early-stage breast tumors, whereas expression was generally not detected in cell lines derived from later-stage tumors. In breast tumor tissue specimens, expression of ln alpha 3 and beta 3 mRNAs tended to be reduced relative to levels observed in adjacent nontumor tissue, whereas in gamma 2 levels were elevated in specimens with increased amounts of myoepithelial cells. These ln-5 expression changes could not be attributed to large-scale mutations or gene rearrangements. Ln-5 protein levels were found to reflect mRNA levels in representative cell lines. At senescence, a growth state believed to suppress tumorigenesis, expression of all three ln-5 mRNAs was up-regulated.

CONCLUSION

The down-regulation of ln-5 mRNA expression in breast tumors cells provides a new molecular marker and suggests that ln-5 functions to control tumor progression in the breast.

19-Nor-1-alpha-25-dihydroxyvitamin D2 (Paricalcitol) safely and effectively reduces the levels of intact parathyroid hormone in patients on hemodialysis

Paricalcitol (19-nor-1alpha-25-dihydroxyvitamin D2), a new vitamin D analog developed for the treatment of secondary hyperparathyroidism, was evaluated in three double-blind, placebo-controlled, dose-escalating, randomized multicenter trials. A total of 78 patients (40 Paricalcitol injection, 38 placebo) achieved treatment phase eligibility, which included intact parathyroid hormone (iPTH) > or = 400 pg/ml, normalized serum calcium levels between 8.0 and 10.0 mg/dl, and calcium x phosphorus product values less than 75. Study end points included a decrease in iPTH of at least 30% or a maximum of five dose escalations. After a 4-wk washout, paricalcitol or placebo was administered intravenously three times per week after dialysis for 12 wk. Study drug was started at a dose of 0.04 microg/kg and was increased by 0.04 microg/kg every 2 wk to a maximal allowable dose of 0.24 microg/kg or until at least a 30% decrease in serum iPTH was achieved. The dose of paricalcitol that decreased iPTH by at least 30% became the maintenance dose. Of 40 patients receiving paricalcitol, 27 (68%) had at least a 30% decrease in serum iPTH for 4 consecutive weeks, compared with three of 38 patients (8%) receiving placebo (P < 0.001). For patients who received 12 wk of treatment with paricalcitol, the levels of iPTH decreased significantly from 795+/-86 to 406+/-106 pg/ml (P < 0.001), whereas the values for PTH were 679+/-41 pg/ml before and 592+/-41 pg/ml after 12 wk of therapy in patients receiving placebo (P=NS). Also, there was a significant difference between treatment groups for the change from baseline PTH levels (P < 0.001). Paricalcitol treatment resulted in a significant reduction in serum alkaline phosphatase from 148+/-23 U/L to 101+/-14 U/L (P < 0.001) in patients treated for 12 wk compared with 120+/-9 U/L to 130+/-11 U/L (P=NS) in patients receiving placebo for 12 wk. Importantly, hypercalcemia did not occur before achieving target serum iPTH levels in any of the paricalcitol-treated patients. There was no significant difference for the change from baseline in serum phosphorus within or between treatment groups. There was no significant difference in adverse events between the paricalcitol and placebo-treated groups. These studies demonstrate that paricalcitol safely and effectively suppresses iPTH levels in hemodialysis patients. This second generation vitamin D analog may have a wider therapeutic window than current vitamin D preparations, and thus may allow reduction in PTH with less hypercalcemia.

Identification and verification of differential display cDNAs using gene-specific primers and hybridization arrays

An accurate and streamlined approach to differential display (DD) band identification and verification is described. To minimize false positives, the strategy avoids the use of impure Northern blot probes obtained from PCR-amplified DD bands. To increase throughput, the cloning of DD bands is replaced by a gene-specific primer approach, and hybridization arrays are used in place of Northern blots. In summary, DD bands obtained with long primers were directly sequenced to allow the design and synthesis of gene-specific primers, which were then used to PCR-amplify homogeneous probes for the verification of expression patterns by hybridization array analysis. Differential expression of 60 of the 63 genes tested was confirmed. Thus, false positives are not inherent to DD. The results demonstrate the power of DD used with hybridization arrays to rapidly generate information on expression patterns of differentially expressed genes.

Terminal differentiation of human breast cancer through PPAR gamma

We have previously demonstrated that PPAR gamma stimulates the terminal differentiation of adipocyte precursors when activated by synthetic ligands, such as the antidiabetic thiazolidinedione (TZD) drugs. We show here that PPAR gamma is expressed at significant levels in human primary and metastatic breast adenocarcinomas. Ligand activation of this receptor in cultured breast cancer cells causes extensive lipid accumulation, changes in breast epithelial gene expression associated with a more differentiated, less malignant state, and a reduction in growth rate and clonogenic capacity of the cells. Inhibition of MAP kinase, shown previously to be a powerful negative regulator of PPAR gamma, improves the TZD ligand sensitivity of nonresponsive cells. These data suggest that the PPAR gamma transcriptional pathway can induce terminal differentiation of malignant breast epithelial cells and thus may provide a novel, nontoxic therapy for human breast cancer.

Expression genetics: a different approach to cancer diagnosis and prognosis

Expression genetics is a new approach to the identification of cancer-related genes. Instead of studying gene mutations at the genome level, it focuses on the investigation of heredity at the RNA level. By isolating genes whose expression is up or down regulated in cancers, expression geneticists study their function in the context of gene regulation. A major goal of expression genetics in cancer is to correct gene expression in tumors by the application of potential therapeutic agents.

Complications associated with insertion of jugular venous catheters for hemodialysis: the value of postprocedural radiograph

It is routine in hemodialysis units to require a chest radiograph after the insertion of an internal jugular line for venous access before dialysis is commenced. There are two principal reasons for this: (1) to ensure that no procedural complications have occurred and (2) to verify correct catheter placement. Knowledge of the time delay involved may prompt nephrologists to opt for femoral access (with increased hemodialysis recirculation and need for repeated line placement). The benefit of the postprocedural chest radiograph has never been evaluated in the hemodialysis population. We retrospectively reviewed the data on internal jugular access placement from two large nephrology training centers. Over a 36-month period, 460 internal jugular dialysis catheters were placed in 312 patients. Wherever possible, 15-cm lines were used for the left internal jugular vein and 12-cm lines for the right internal jugular vein. Ultrasound guidance was used in 105 cases (22.8%). There were a total of 90 (19.6%) clinical complications in 62 patients (13.5%). These consisted of carotid artery puncture (n = 35, 7.6%) and hematoma (n = 55, 12%). All of these patients had a normal post-internal jugular chest radiograph. Carotid artery puncture did not occur if ultrasound guidance was used. There was no case of associated pneumothorax. Of the 370 line insertions in 250 patients in whom it was believed clinically that no complication had occurred, the chest radiograph only showed unsuspected line malposition in four cases (1.08%). Routine chest radiographs rarely contribute to the diagnosis of any procedural complications and are of little value after internal jugular access placement, especially if it is believed clinically that no complication occurred.

Coordinate regulation of PTH/PTHrP receptors by PTH and calcitriol in UMR 106-01 osteoblast-like cells

High levels of PTH result in desensitization of target cells to further stimulation with PTH in vivo and in vitro. While studies in vitro demonstrate that the effect of PTH can be direct, it is also possible that studies in vivo may be complicated by the fact that other potential regulators of PTH action, such as increased levels of calcitriol, may play a role. Thus, we examined the actions of calcitriol and PTH on PTH/PTHrP-receptor expression in confluent cultures of UMR 106-01 osteoblast-like cells treated with calcitriol, PTH or both hormones for one to three days. Following these treatments, studies of PTH receptor binding, cAMP generation, and steady-state levels of PTH/PTHrP receptor mRNA were performed. Exposure to PTH resulted in a decrease in PTH stimulated cAMP generation by 88 +/- 2%, and PTH binding by 63 +/- 3%. Levels of PTH/PTHrP-receptor mRNA decreased progressively reaching 20% of control values after three days of PTH (100 nM) treatment. Calcitriol also resulted in a dose and time-dependent decrease in PTH/PTHrP-receptor mRNA, decreasing by 72 +/- 4% after 48 hours. PTH receptor binding and cAMP generation were diminished by 42 +/- 3% and 42 +/- 4%, respectively. Co-incubation of UMR 106-01 cells with submaximal doses of calcitriol and PTH together revealed that the levels of PTH/PTHrP-receptor mRNA were decreased by both hormones together to a greater extent than with either alone. These studies show that both calciotropic hormones, PTH and calcitriol, are potent regulators of PTH/PTHrP-receptor gene expression in UMR 106-01 osteoblast-like cells. Thus, stimulation of calcitriol production by PTH may result in a coordinated down-regulation of PTH receptor expression by these hormones.

Retinoids modulate the effect of PTH and calcitriol on EGF receptor expression in UMR 106-01 cells

Although osteoblast proliferation is a prominent feature of osteitis fibrosa, studies in vitro using osteoblast-like cells have shown that parathyroid hormone (PTH) impairs cell growth. Recent studies in our laboratory have shown that PTH increases epidermal growth factor (EGF) receptor expression in UMR 106-01 osteoblast-like cells, and thus, osteoblast proliferation may occur as a result of an enhanced response of the osteoblast to EGF. In the present studies we investigated the effect of calcitriol and the influence of retinoids on the regulation of EGF receptors. Calcitriol increased 125I-EGF binding 2.5-3-fold after 72 hours of incubation and was maximal at a calcitriol dose of 100 nM. Scatchard analysis showed that this effect was due to increased receptor number. In contrast, all-trans retinoic acid or 9-cis retinoic acid alone, even at 10 microM, caused less than a 50% increase in 125I-EGF binding. However, the effect of calcitriol was totally abolished in the presence of all-trans retinoic acid. 9-cis retinoic acid was equivalent with all-trans retinoic acid in this regard. In the presence of either retinoid, the stimulatory effect of PTH was totally eliminated and EGF binding was actually decreased below control values. Additional studies revealed that retinoic acid decreased PTH-stimulated cAMP generation in a dose-dependent manner. These data are consistent with our previous studies which showed that the effect of PTH on the induction of EGF receptors was mediated by a cAMP-dependent mechanism. The inhibition of the calcitriol effect by retinoids is consistent with the requirement of the retinoid-X-receptor (RXR) for binding of the vitamin D receptor (VDR) to its target sequences in DNA. These data indicate that EGF receptors in UMR 106-01 cells are up-regulated by PTH and calcitriol and that this process can be modulated by retinoids. Retinoids, therefore, may play a major role in the regulation of osteoblast function by PTH and calcitriol.