Detection and Quantification of Calcitonin Gene-Related Peptide (CGRP) in Human Plasma Using a Modified Enzyme-Linked Immunosorbent Assay

Calcitonin gene-related peptide (CGRP) is a vasoactive neuropeptide that plays a putative role in the pathophysiology of migraine headaches and may be a candidate for biomarker status. CGRP is released from neuronal fibers upon activation and induces sterile neurogenic inflammation and arterial vasodilation in the vasculature that receives trigeminal efferent innervation. The presence of CGRP in the peripheral vasculature has spurred investigations to detect and quantify this neuropeptide in human plasma using proteomic assays, such as the enzyme-linked immunosorbent assay (ELISA). However, its half-life of 6.9 min and the variability in technical details of assay protocols, which are often not fully described, have yielded inconsistent CGRP ELISA data in the literature. Here, a modified ELISA protocol for the purification and quantification of CGRP in human plasma is presented. The procedural steps involve sample collection and preparation, extraction using a polar sorbent as a means of purification, additional steps to block non-specific binding, and quantification via ELISA. Further, the protocol has been validated with spike and recovery and linearity of dilution experiments. This validated protocol can theoretically be used to quantify CGRP concentrations in the plasma of individuals not only with migraine, but also with other diseases in which CGRP may play a role.

Growth Differentiation Factor-15 Predicts Mortality and Heart Failure Exacerbation But Not Ventricular Arrhythmias in Patients With Cardiomyopathy

Background Heart failure (HF) has been increasing in prevalence, and a need exists for biomarkers with improved predictive and prognostic ability. GDF-15 (growth differentiation factor-15) is a novel biomarker associated with HF mortality, but no serial studies of GDF-15 have been conducted. This study aimed to investigate the association between GDF-15 levels over time and the occurrence of ventricular arrhythmias, HF hospitalizations, and all-cause mortality. Methods and Results We used a retrospective case-control design to analyze 148 patients with ischemic and nonischemic cardiomyopathies and primary prevention implantable cardioverter-defibrillator (ICD) from the PROSe-ICD (Prospective Observational Study of the ICD in Sudden Cardiac Death Prevention) cohort. Patients had blood drawn every 6 months and after each appropriate ICD therapy and were followed for a median follow-up of 4.6 years, between 2005 to 2019. We compared serum GDF-15 levels within ±90 days of an event among those with a ventricular tachycardia/fibrillation event requiring ICD therapies and those hospitalized for decompensated HF. A comparator/control group comprised patients with GDF-15 levels available during 2-year follow-up periods without events. Median follow-up was 4.6 years in the 148 patients studied (mean age 58±12, 27% women). The HF cohort had greater median GDF-15 values within 90 days (1797 pg/mL) and 30 days (2039 pg/mL) compared with the control group (1062 pg/mL, both P<0.0001). No difference was found between the ventricular tachycardia/fibrillation subgroup within 90 days (1173 pg/mL, P=0.60) or 30 days (1173 pg/mL, P=0.78) and the control group. GDF-15 was also significantly predictive of mortality (hazard ratio, 3.17 [95% CI, 2.33-4.30]). Conclusions GDF-15 levels are associated with HF hospitalization and mortality but not ventricular arrhythmic events.

Effects of Ramelteon on the Prevention of Postoperative Delirium in Older Patients Undergoing Orthopedic Surgery: The RECOVER Randomized Controlled Trial

OBJECTIVES

Postoperative delirium, associated with negative consequences including longer hospital stays and worse cognitive and physical outcomes, is frequently accompanied by sleep-wake disturbance. Our objective was to evaluate the efficacy and short-term safety of ramelteon, a melatonin receptor agonist, for the prevention of postoperative delirium in older patients undergoing orthopedic surgery.

DESIGN

A quadruple-masked randomized placebo-controlled trial (Clinical Trials.gov NCT02324153) conducted from March 2017 to June 2019.

SETTING

Tertiary academic medical center.

PARTICIPANTS

Patients aged 65 years or older, undergoing elective primary or revision hip or knee replacement.

INTERVENTION

Ramelteon (8 mg) or placebo MEASUREMENTS: Eighty participants were randomized to an oral gel cap of ramelteon or placebo for 3 consecutive nights starting the night before surgery. Trained research staff conducted delirium assessments for 3 consecutive days starting on postoperative day (POD) 0, after recovery from anesthesia, and on to POD2. A delirium diagnosis was based upon DSM-5 criteria determined by expert panel consensus.

RESULTS

Of 80 participants, five withdrew consent (one placebo, four ramelteon) and four were excluded (four ramelteon) after randomization. Delirium incidence during the 2 days following surgery was 7% (5 of 71) with no difference between the ramelteon versus placebo: 9% (3 of 33) and 5% (2 of 38), respectively. The adjusted odds ratio for postoperative delirium as a function of assignment to the ramelteon treatment arm was 1.28 (95% confidence interval: 0.21-7.93; z-value 0.27; p-value = 0.79). Adverse events were similar between the two groups.

CONCLUSION

In older patients undergoing elective primary or revision hip or knee replacement, ramelteon was not efficacious in preventing postoperative delirium.

Prevalence of Angiotensin II Type 1 Receptor Antibodies in Persons With Hypertension and Relation to Blood Pressure and Medication

BACKGROUND

We aimed to determine the prevalence of antibodies against angiotensin II type 1 receptor (AT1RAb) in hypertensive adults and elucidate the relation of antihypertensive medication type to blood pressure (BP) among persons with and without AT1RAb.

METHODS

Sera from participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study with hypertension were tested for AT1RAb using a commercial Enzyme-linked immunosorbent assay (ELISA) (One Lambda; positive ≥17 units/ml). BP measurements, uncontrolled BP (systolic BP ≥140 and/or diastolic BP ≥90 mm Hg), and effect of BP medication type were compared for AT1RAb positive (+) vs. negative (-) participants using descriptive statistics and multivariable regression.

RESULTS

One hundred and thirty-two (13.1%) participants were AT1RAb+. Compared with AT1RAb-, AT1RAb+ persons were more likely to be white (47% vs. 36.7%; P = 0.03) but had similar comorbid disease burden. In models adjusting for age, sex, and race, AT1RAb+ persons had higher diastolic BP (β = 2.61 mm Hg; SE = 1.03; P = 0.01) compared with AT1RAb- participants. Rates of uncontrolled BP were similar between the groups. AT1RAb+ persons on an angiotensin receptor blocker (ARB; n = 21) had a mean of 10.5 mm Hg higher systolic BP (SE = 4.56; P = 0.02) compared with AT1RAb+ persons using other BP medications. The odds of uncontrolled BP among AT1RAb+ participants on an ARB was 2.05 times that of those on other medications. AT1RAb- persons prescribed an angiotensin-converting enzyme inhibitor (ACEi) had 1.8 mm Hg lower diastolic BP (SE = 0.81; P = 0.03) than AT1RAb- persons not prescribed an ACEi.

CONCLUSIONS

AT1RAb was prevalent among hypertensive adults and was associated with higher BP among persons on an ARB.

Leveraging naturally occurring variation in financial stress to examine associations with inflammatory burden among older adults

BACKGROUND

Financial strain is associated with earlier disability and mortality, but causal links are underexplored, partly because it is unethical to randomise people to financial stress. This study leverages naturally occurring random variation in days since monthly Social Security payment arrival among older adults to test associations with inflammatory biomarkers.

METHODS

Biomarker data, including tumour necrosis factor (TNF)-α, interleukin (IL)-6 and C reactive protein (CRP), was collected from 2155 non-working healthy adults aged 70-79 years, participating in the Health, Aging and Body Composition Study. Days since payment arrival was independent of all demographic, socioeconomic or health characteristics measured in this study. Restricted cubic spline models estimated associations separately for each week of the month, stratified by financial strain status (interaction term p value for TNF-α model <0.05).

RESULTS

Among financially strained older adults, more days since payment arrival was associated with higher TNF-α levels during the first week of the month (coefficient=0.102). Associations with IL-6 and CRP differed depending on the degree of financial strain (interaction term p values <0.05). Those with low, but not high, strain had lower levels of IL-6 (coefficient=-0.152) and CRP (coefficient=-0.179) during the first week.

CONCLUSIONS

Days since monthly payments were associated with inflammatory cytokines among older adults who have difficulty making ends meet financially and associations depended on financial strain severity, suggesting that results are attributable to monthly variation in financial stress. Future research should examine whether more frequent Social Security disbursement would modify financial strain and inflammatory biomarkers.

Angiotensin receptor autoantibodies as exposures that modify disease progression: Cross sectional, longitudinal and in vitro studies of prostate cancer

Circulating angiotensin type I receptor (AT1R) agonistic autoantibodies (AT1RaAbs) that bind and chronically activate the receptor have been associated with a number of diseases suggesting that while the autoantibodies are not necessarily causative they may promote disease progression. The prostate has a local renin angiotensin system. The current study examines associations between AT1RaAbs and prostate cancer (PCA), disease-free survival (DFS), overall survival (OS) and AT1RaAb effects on PCA cell phenotype. In a cross-sectional set of serum obtained from 151 men diagnosed with PCA, nonmalignant prostate disease or no disease, higher serum AT1RaAb levels were associated with PCA and non-organ confined PCA. The odds ratio for PCA was 6.3 (95% confidence interval 2.2 to 18) for a positive 1:1600 titer and 18 (95% confidence interval 6.9 to 45) at AT1RaAb levels > 1.04 μg/ml, (p < 0.0001). In a longitudinal set of pre-diagnosis samples from 109 men, DFS hazard ratios of 2.2 (95% confidence interval 1.4 to 3.5) and 1.6 (95% confidence interval 1.0 to 2.5) for most proximal to diagnosis and most distal to diagnosis samples, respectively, were found for high versus low AT1RaAb groups. Hazard ratios for OS in most proximal and distal samples were 2.4 (95% confidence interval 1.6 to 3.6) and 1.8 (95% confidence interval 1.1 to 2.8), respectively. Accelerated failure modeling of survival indicated that a 1 μg/ml increase in AT1RaAb levels was associated with a reduction of DFS and OS by 20% at the most proximal time point and by 15% at the most distal time points. Adjusting for age, did not affect the association with DFS in proximal samples but changed distal time point DFS and OS to a 10% decrease for every 1 μg/ml increase in AT1RaAb. Additional adjustments for body mass index, systolic blood pressure and prostate-specific antigen did not appreciably alter these associations. AT1RaAb treatment of PC3, DU145, and LNCaP cells significantly increased the maximal growth rate approximately 2-fold and invasiveness approximately 3-fold. Conclusions: These observations provide evidence supporting AT1RaAbs as exposures that may modify prostate cancer progression and indicate they may be predictive markers for risk stratification.

Chitotriosidase, a marker of innate immunity, is elevated in patients with primary breast cancer

BACKGROUND

Cancer progression has been associated with altered immune cell function and activation. Neopterin, which is secreted by interferon-γ stimulated macrophages, exhibits an association with multiple cancer types and metastatic disease. Chitotriosidase, which is secreted by chronically activated macrophages and granulocyte-macrophage colony-stimulating factor stimulated neutrophils has not been studied in the setting of cancer.

OBJECTIVE

The goal of this discovery study was to screen chitotriosidase for diagnostic capacity in detecting cancer and compare its operating characteristics with those of neopterin.

METHODS

Serum from subjects with breast (n= 66) or prostate (n= 70) cancer, and from 204 subjects free of malignant disease were studied. Chitotriosidase was measured by enzyme activity assay, while neopterin was measured by a competitive enzyme immunoassay. Statistical analyses included group comparisons by Mann Whitney U test, diagnostic capacity by receiver operating characteristics (ROC) curve analysis and biomarker associations with physiologic and clinical measures by Spearman correlation.

RESULTS

Chitotriosidase activity was significantly higher in both cancer types compared with gender matched controls, though only in breast cancer was the diagnostic capacity significant (area under the ROC curve of 0.97 ± 0.01). In contrast, neopterin was significantly elevated in prostate cancer and exhibited discriminatory capacity (area under the ROC curve of 0.76 ± 0.05). Age, BMI, % body fat and metastasis were variables that correlated with neopterin, but not chitotriosidase levels.

CONCLUSIONS

The operating characteristics of serum chitotriosidase were different from neopterin and further analysis of chitotriosidase as a biomarker for breast cancer is warranted.

Discovery and Validation of Agonistic Angiotensin Receptor Autoantibodies as Biomarkers of Adverse Outcomes

BACKGROUND

Agonistic angiotensin II type 1 receptor autoantibodies (AT1RaAbs) have not been associated with functional measures or risk for adverse health outcomes. AT1RaAbs could be used to stratify patient risk and to identify patients who can benefit from angiotensin receptor blocker treatment.

METHODS

Demographic and physiological covariates were measured in a discovery set of community-dwelling adults from Baltimore (N=255) and AT1RaAb associations with physical function tests and outcomes assessed. A group from Chicago (N=60) was used for validation of associations and to explore the impact of angiotensin receptor blocker treatment.

RESULTS

The Baltimore group had 28 subjects with falls, 32 frail subjects, and 5 deaths. Higher AT1RaAbs correlated significantly with interleukin-6 (Spearman r=0.33, P<0.0001), systolic blood pressure (Spearman r=0.28, P<0.0001), body mass index (Spearman r=0.28, P<0.0001), weaker grip strength (Spearman r=-0.34, P<0.01), and slower walking speed (Spearman r=-0.30, P<0.05). Individuals with high AT1RaAbs were 3.9 (95% confidence interval, 1.38-11.0) times more likely to be at high risk after adjusting for age (P<0.05). Every 1 µg/mL increase in AT1RaAbs increased the odds of falling 30% after adjusting for age, sex, body mass index, and blood pressure. The Chicago group had 46 subjects with falls and 60 deaths. Serum AT1RaAb levels were significantly correlated with grip strength (Spearman r=-0.57, P<0.005), walking speed (Spearman r=-0.47, P<0.005), and falls (Spearman r=0.30, P<0.05). Every 1 µg/mL increase in AT1RaAbs, decreased time to death by 9% after adjusting for age, sex, body mass index, and blood pressure. Chronic treatment with angiotensin receptor blockers was associated with better control of systolic blood pressure and attenuation of decline in both grip strength and time to death.

CONCLUSIONS

In older individuals, higher AT1RaAb levels were associated with inflammation, hypertension, and adverse outcomes. Angiotensin receptor blocker treatment may blunt the harm associated with high levels of AT1RaAb.

Stability and degradation of fibroblast growth factor 23 (FGF23): the effect of time and temperature and assay type

There is growing need for a reliable assay for measuring fibroblast growth factor 23 (FGF23), a regulator of phosphorus and vitamin D. In this work, we analyze and compare the performance of three available assays, including the effect of temperature and time. This knowledge will allow for better understanding of FGF23 in the future.

INTRODUCTION

Intact and C-terminal FGF23 (iFGF23 and cFGF23) concentrations are important in the diagnosis of hypo- and hyperphosphatemic diseases. The effects of temperature, storage, and specimen handling on FGF23 levels are not well known. We investigated the effects of various factors on plasma and serum measurement of FGF23 using three different assays.

METHODS

Serum and plasma FGF23 were measured using three commercially available ELISA assays-two measuring iFGF23 and one measuring cFGF23. Samples from subjects with known FGF23 disorders were stored at 4, 22, and 37 °C and analyzed at different intervals up to 48 hours (h). A subset of samples underwent repeated freeze-thaw cycles, and samples frozen at -80 °C for up to 60 months were reanalyzed. The effect of adding a furin convertase inhibitor on FGF23 degradation was investigated using samples stored at 37 °C for 48 h. Intact FGF23 levels were measured from plasma samples of four different groups to test the correlation of the two assays.

RESULTS

Plasma FGF23 levels were stable when stored at 4 and 22 °C for 48 h. Both plasma and serum FGF23 levels demonstrated relative stability after five freeze-thaw cycles. Long-term storage at -80 °C for 40 months induced some variability in FGF23 levels. The addition of a furin inhibitor did not affect FGF23 degradation. Intact FGF23 levels showed good correlation only at the upper limit of the assay range when comparing the two assays.

CONCLUSIONS

Sample type, handling, and choice of assay are factors that affect FGF23 levels and should be considered when measuring this hormone.

Osteoblast function and bone histomorphometry in a murine model of Rett syndrome

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder due to mutations affecting the neural transcription factor MeCP2. Approximately 50% of affected females have decreased bone mass. We studied osteoblast function using a murine model of RTT. Female heterozygote (HET) and male Mecp2-null mice were compared to wild type (WT) mice. Micro-CT of tibia from 5 week-old Mecp2-null mice showed significant alterations in trabecular bone including reductions in bone volume fraction (-29%), number (-19%), thickness (-9%) and connectivity density (-32%), and increases in trabecular separation (+28%) compared to WT. We also found significant reductions in cortical bone thickness (-18%) and in polar moment of inertia (-45%). In contrast, cortical and trabecular bone from 8 week-old WT and HET female mice were not significantly different. However, mineral apposition rate, mineralizing surface and bone formation rate/bone surface were each decreased in HET and Mecp2-null mice compared to WT mice. Histomorphometric analysis of femurs showed decreased numbers of osteoblasts but similar numbers of osteoclasts compared to WT, altered osteoblast morphology and decreased tissue synthesis of alkaline phosphatase in Mecp2-null and HET mice. Osteoblasts cultured from Mecp2-null mice, which unlike WT osteoblasts did not express MeCP2, had increased growth rates, but reductions in mRNA expression of type I collagen, Runx2 and Osterix compared to WT osteoblasts. These results indicate that MeCP2 deficiency leads to altered bone growth. Osteoblast dysfunction was more marked in Mecp2-null male than in HET female mice, suggesting that expression of MeCP2 plays a critical role in bone development.

The short-term and long-term impact of a brief aging research training program for medical students

Summer training in aging research for medical students is a strategy for improving the pipeline of medical students into research careers in aging and clinical care of older adults. Johns Hopkins University has been offering medical students a summer experience of mentored research, research training, and clinical shadowing since 1994. Long-term outcomes of this program have not been described. The authors surveyed all 191 participants who had been in the program from 1994-2010 (60% female and 27% underrepresented minorities) and received a 65.8% (N = 125) response rate. The authors also conducted Google and other online searches to supplement study findings. Thirty-seven percent of those who have completed training are now in academic medicine, and program participants have authored or coauthored 582 manuscripts. Among survey respondents, 95.1% reported that participation in the Medical Student Training in Aging Research program increased their sensitivity to the needs of older adults. This program may help to build commitment among medical students to choose careers in aging.

WISP1/CCN4: a potential target for inhibiting prostate cancer growth and spread to bone

Prostate cancer (PC) is a leading cause of death in men however the factors that regulate its progression and eventual metastasis to bone remain unclear. Here we show that WISP1/CCN4 expression in prostate cancer tissues was up-regulated in early stages of the disease and, further, that it correlated with increased circulating levels of WISP1 in the sera of patients at early stages of the disease. WISP1 was also elevated in the mouse prostate cancer model TRAMP in the hypoplastic diseased tissue that develops prior to advanced carcinoma formation. When the ability of anti-WISP1 antibodies to reduce the spread of PC3-Luc cells to distant sites was tested it showed that twice weekly injections of anti-WISP1 antibodies reduced the number and overall size of distant tumors developed after intracardiac (IC) injection of PC3-Luc cells in mice. The ability of antibodies against WISP1 to inhibit growth of PC3-Luc cancer cells in mice was also evaluated and showed that twice weekly injections of anti-WISP1 antibodies reduced local tumor growth when examined in xenografts. To better understand the mechanism of action, the migration of PC3-Luc cells through membranes with or without a Matrigel™ barrier showed the cells were attracted to WISP1, and that this attraction was inhibited by treatment with anti-WISP1 antibodies. We also show the expression of WISP1 at the bone-tumor interface and in the stroma of early grade cancers suggested WISP1 expression is well placed to play roles in both fostering growth of the cancer and its spread to bone. In summary, the up-regulation of WISP1 in the early stages of cancer development coupled with its ability to inhibit spread and growth of prostate cancer cells makes it both a potential target and an accessible diagnostic marker for prostate cancer.

Serum chitotriosidase, a putative marker of chronically activated macrophages, increases with normal aging

BACKGROUND

Chitotriosidase (ChT) is secreted by chronically activated macrophages in Gaucher's disease. We hypothesize that circulating levels of ChT are altered with normal aging, reflecting age-related chronic macrophage activation. Potential sources that might contribute to altered levels were assessed by measuring systemic levels of ChT are α-naphthyl acetate esterase, a macrophage lysosomal enzyme; granulocyte-macrophage colony-stimulating factor (GM-CSF), which stimulates neutrophilic granule release of ChT; interleukin-6 (IL-6); and neopterin, a macrophage activation marker.

METHODS

Serum was obtained from 315 healthy participants whose age ranged from 18 to 92 years. Anthropometric measures included percent body fat and body mass index. ChT and α-naphthyl acetate esterase levels were measured by enzyme activity assays. GM-CSF, IL-6, and neopterin concentrations were measured by commercial enzyme-linked immunosorbent assays. Serum marker values were statistically analyzed using nonparametric tests.

RESULTS

Six percent of the participants had undetectable ChT levels. A positive association with age was observed for ChT and IL-6, whereas a negative correlation with age was seen for α-naphthyl acetate esterase and GM-CSF. ChT values were not associated with α-naphthyl acetate esterase or GM-CSF levels. ChT was independently associated with IL-6 and neopterin levels, but statistical significance was attenuated when controlled for age.

CONCLUSIONS

The data are consistent with increased serum ChT activity not arising from altered macrophage lysosomal enzyme trafficking or GM-CSF-stimulated release of neutrophil granule stores. The association of ChT with age remains significant after controlling for neopterin and IL-6 changes with age, suggesting that ChT levels reflect a macrophage state distinct from acute macrophage activation or inflammatory state.

Plasma neopterin level as a marker of peripheral immune activation in amnestic mild cognitive impairment and Alzheimer's disease

OBJECTIVE

Alterations of the immune system play important roles in Alzheimer's disease (AD). The primary purpose of this study was to compare the plasma levels of neopterin, a marker of cellular immune activity, in amnestic mild cognitive impairment (aMCI), early (mild to moderate) AD, and cognitively normal controls. In addition, the correlation of plasma neopterin with interferon-gamma (IFN-γ) and interleukin-6 (IL-6) was also examined.

METHODS

Plasma samples from patients with mild-to-moderate AD (N = 34), aMCI (N = 27), and cognitively normal controls (N = 30) were obtained from the Johns Hopkins Alzheimer's Disease Research Center. Plasma neopterin, IFN-γ, and IL-6 levels were measured using commercially available ELISAs. Multiple linear regression was performed to study differences in the baseline neopterin levels between normal, aMCI, and AD patients. Pearson correlation coefficients were estimated for neopterin and IFN-γ and IL-6 levels. All analyses were conducted using SAS (SAS Institute, Inc., Cary, NC) and GraphPad Prism version 5.00 for Window (GraphPad Software, San Diego, CA, USA).

RESULTS

AD subjects had significantly higher neopterin values compared with aMCI (β = 0.202, p = 0.004) and normal (β = 0.263, p = 0.0004) subjects. There was no statistically significant difference between normal and aMCI subjects. Significant associations between neopterin and IFN-γ (r = 0.41, p < 0.0001) and IL-6 (r = 0.35, p = 0.0006) levels were found.

CONCLUSIONS

Our study demonstrates that peripheral immune response may be stronger in later stages of AD pathophysiology, when dementia has developed.

Changes in bone biomarker concentrations and musculoskeletal symptoms among breast cancer patients initiating aromatase inhibitor therapy and women without a history of cancer

The objectives of this study were to examine: (1) changes in bone formation (osteocalcin) and bone resorption (cross-linked N-telopeptides of bone type I collagen [NTXs]) markers, as well as calcium, phosphorus, and intact parathyroid hormone, over the first 6 months of aromatase inhibitor (AI) therapy among a cohort of breast cancer patients compared with a group of unexposed women without a history of cancer; and (2) whether bone marker changes were associated with musculoskeletal pain. Eligible breast cancer patients (n = 49) and postmenopausal women without a history of cancer (n = 117) were recruited and followed for 6 months. At baseline, 3 months, and 6 months, a questionnaire was administered to assess pain and medication use, and a blood sample was drawn. Results showed that, among the breast cancer patients, calcium concentrations decreased significantly (-7.8% change; p = 0.013) and concentrations of NTXs increased significantly from baseline to 6 months (9.6% change; p = 0.012). Changes were not observed for women in the comparison group. Statistically significant differences in percent change between the breast cancer patients and the women in the comparison group were observed for calcium at 6 months (-7.8% versus 0.0%; p = 0.025), phosphorus at 6 months (-5.1% versus 16.7%; p = 0.003), NTXs at 6 months (9.6% versus -0.7%; p = 0.017), and osteocalcin at 6 months (11.5% versus -3.6%; p = 0.016). No statistically significant associations were observed between bone turnover marker changes and musculoskeletal pain among the breast cancer patients, although baseline NTXs were higher among women with onset or increase in pain compared with those reporting no pain (p = 0.08). Findings from this study suggest that AIs cause changes in bone turnover during the first 6 months of treatment; however, these changes are not associated with musculoskeletal pain. Breast cancer patients initiating AI therapy should be assessed and monitored for fracture risk using known clinical risk factors, including bone density, and managed appropriately.

IL-6-independent association of elevated serum neopterin levels with prevalent frailty in community-dwelling older adults

BACKGROUND

neopterin is a monocyte/macrophage-derived immune activation marker and its levels increase with age. Frailty is an important clinical syndrome of old age. Previous studies have shown significant association between elevated interleukin-6 (IL-6) levels and frailty. The objective of this study was to evaluate IL-6-independent association of serum neopterin levels with prevalent frailty.

METHODS

this is a cross-sectional study in community-dwelling older adults recruited from residential and retirement communities in Baltimore, MD, USA. Frailty was determined using validated screening criteria. Serum neopterin and IL-6 levels were measured using standard enzyme-linked immunosorbent assay. Pearson correlation and multivariate linear regression analysis was performed to assess the relationship between log(neopterin) and log(IL-6). Odds ratios (ORs) for frailty were calculated using log(neopterin) and log(IL-6) as continuous measures and across tertiles of neopterin and IL-6 levels, adjusting for age, race, sex, education and body mass index.

RESULTS

one hundred and thirty-three individuals with a mean age of 84 years (range 72-97) completed the study. Neopterin levels were significantly higher in frail older adults than those in non-frail controls [median: 8.94 versus 8.35 nM, respectively, P < 0.001 t-test on log(neopterin)]. Log(neopterin) was significantly associated with prevalent frailty, adjusting for log(IL-6). Participants in the top tertile of neopterin had OR of 3.80 [95% confidence interval (CI) = 1.36-10.6, P < 0.01] for frailty. As expected, participants in the top tertile of IL-6 had OR of 3.29 (95% CI = 1.21-7.86, P < 0.05) for frailty. Log(neopterin) correlated with log(IL-6) (correlation coefficient = 0.19, P < 0.05). Moreover, OR for participants in the top neopterin tertile remained significant after adjusting for IL-6 (OR = 3.97, 95% CI = 1.15-13.72, P < 0.05).

CONCLUSION

elevated neopterin levels had IL-6-independent association with prevalent frailty, suggesting potential monocyte/macrophage-mediated immune activation in the frail elderly.

The biology of aging and frailty

In developing and validating the concept of frailty as a geriatric syndrome, it has been necessary to distinguish the clinical expression of frailty from normal age-related changes and other age-related disease pathologies. A framework for excluding potentially confounding disease and a working clinical tool to diagnose frailty have been provided. The associations between frailty and other pathophysiologies has also been shown. However, investigating the underlying biologic basis for the geriatric syndrome of frailty by studying basic homeostatic pathways and mechanisms has not proceeded at the same rate. The following article provides an overview of the homeostatic pathways emphasized in research on aging and explains how this science may help to stimulate frailty research.

Comparison of conventional ELISA with electrochemiluminescence technology for detection of amyloid-β in plasma

Plasma amyloid-β (Aβ) level could be useful as a non-invasive biomarker in Alzheimer's disease research. We compared a multiplex electrochemiluminescence detection method with a well established ELISA method for plasma Aβ quantification. Compared to the ELISA method, the electrochemiluminescence detection method demonstrates a statistically significant, but modest correlation. The reasons for this may include the differences in the affinities of antibodies, and purity and source of Aβ peptides used as standards. However, the advantages of electrochemiluminescence detection technology include short processing time and small sample volume. This comparison demonstrates the need for a further study in optimizing this system.

Serum levels of the immune activation marker neopterin change with age and gender and are modified by race, BMI, and percentage of body fat

BACKGROUND

Neopterin, a GTP metabolite expressed by macrophages, is a marker of immune activation. We hypothesize that levels of this serum marker alter with donor age, reflecting increased chronic immune activation in normal aging. In addition to age, we assessed gender, race, body mass index (BMI), and percentage of body fat (%fat) as potential covariates.

METHODS

Serum was obtained from 426 healthy participants whose age ranged from 18 to 87 years. Anthropometric measures included %fat and BMI. Neopterin concentrations were measured by competitive ELISA. The paired associations between neopterin and age, BMI, or %fat were analyzed by Spearman's correlation or by linear regression of log-transformed neopterin, whereas overall associations were modeled by multiple regression of log-transformed neopterin as a function of age, gender, race, BMI, %fat, and interaction terms.

RESULTS

Across all participants, neopterin exhibited a positive association with age, BMI, and %fat. Multiple regression modeling of neopterin in women and men as a function of age, BMI, and race revealed that each covariate contributed significantly to neopterin values and that optimal modeling required an interaction term between race and BMI. The covariate %fat was highly correlated with BMI and could be substituted for BMI to yield similar regression coefficients.

CONCLUSION

The association of age and gender with neopterin levels and their modification by race, BMI, or %fat reflect the biology underlying chronic immune activation and perhaps gender differences in disease incidence, morbidity, and mortality.

Small integrin-binding proteins as serum markers for prostate cancer detection

PURPOSE

The small integrin-binding ligand N-linked glycoprotein (SIBLING) gene family includes bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), matrix extracellular phosphoglycoprotein (MEPE), and osteopontin (OPN). Previous studies have separately reported elevated expression of BSP, OPN, or DSPP in prostate tumor paraffin sections. We hypothesized that SIBLINGs may be informative serum markers for subjects with prostate cancer.

METHODS

Expression levels of SIBLINGs in biopsies of normal tissue and tumors from prostate were determined by cDNA array and by immunohistochemical staining with monoclonal antibodies. Competitive ELISAs for measuring total BSP, DSPP, MEPE, and OPN were applied to a test group of 102 subjects with prostate cancer and 110 normal subjects and a validation group of 90 subjects.

RESULTS

BSP, DMP1, DSPP, and OPN exhibited elevated mRNA expression and protein levels in biopsies. BSP, DSPP, and OPN were elevated in serum from prostate cancer subjects, with serum DSPP exhibiting the greatest difference, yielding an area under the receiver operator characteristic curve value of 0.98. Serum BSP and OPN levels were significantly elevated only in late stages, whereas DSPP was significantly elevated at all stages. Optimal serum value cutoff points derived for BSP, OPN, and DSPP were applied as a validation test to a new group of 90 subjects and DSPP yielded a sensitivity of 90% and a specificity of 100%.

CONCLUSION

Of the SIBLING gene family members, DSPP appears to be a strong candidate for use in serum assays for prostate cancer detection.

Surgical blood loss during femoral rodding in children with osteogenesis imperfecta

BACKGROUND

Historically, patients with osteogenesis imperfecta (OI) have been reported to be at risk for significant surgical bleeding secondary to abnormalities in platelet function. By reviewing the operative blood loss in OI patients undergoing femoral osteotomies and rodding, we hoped to identify risk factors for excessive bleeding.

METHODS

A retrospective review of 22 patients with 52 inserted femoral rods was conducted under Institutional Review Board approval. Information concerning patients and procedures was collected. Associations with mean blood loss were made for categorical variables using the unpaired t-test and for continuous variables using correlation. Multivariate linear regression was used to test the influence of potential risk factors for excessive bleeding.

RESULTS

The mean blood loss was 197 cc (standard deviation [SD] 129 cc, range 10-500 cc). The adjusted mean blood loss (ratio of actual blood loss divided by the total predicted blood volume [Custer and Rau in "The Harriet Lane Handbook," 18th edn. Mosby-Elsevier, Philadelphia, p 382, 2009]) was 0.16 (SD 0.13, range 0.01-0.44). Six blood transfusions were required out of 42 cases for a transfusion rate of 14%. The mean blood loss in those patients who were transfused was 279 cc compared with 182 cc for those not transfused. There were no differences in the adjusted mean blood loss between acute fracture treatment versus elective reconstruction (P = 0.08), nor between primary rodding versus revision rodding (P = 0.66). Older patients tended to have lower adjusted mean blood loss, though this was not significant (P = 0.07). Increasing number of osteotomies tended to lead to increased adjusted mean blood loss (P = 0.05). There was no association between operative time and adjusted mean blood loss (P = 0.36). When adjusting for procedure characteristics, increasing age was associated with decreasing adjusted mean blood loss (P = 0.008).

CONCLUSION

Predicting blood loss for femoral rodding in patients with OI is difficult, with no differences between revision and primary procedures or elective versus trauma cases. The blood loss in our patients undergoing femoral rodding was manageable, and the transfusion rate was reasonably low. Although massive blood loss has been described in patients with OI in the literature, we found that femoral rodding did not pose excessive risk of transfusion in our OI population.

Upregulated monocytic expression of CXC chemokine ligand 10 (CXCL-10) and its relationship with serum interleukin-6 levels in the syndrome of frailty

Frailty is an important geriatric syndrome that predicts disability and mortality. Substantial evidence suggests inflammation marked by elevated IL-6 levels as a key pathophysiologic factor that contributes to frailty. CXCL-10, a potent pro-inflammatory chemokine, has increased levels with age and is implicated in several inflammatory conditions. To better understand molecular mechanisms of inflammation activation in frailty, we evaluated monocytic expression of CXCL-10 and other inflammatory pathway genes by pathway-specific gene array analysis and quantitative RT-PCR. Frailty status was determined by the validated criteria. Sixteen pairs of community-dwelling frail and age-, race-, and sex-matched non-frail participants (mean age 83 years, range 72-94) completed the study. Here we report that frail participants had higher CXCL-10 expression levels than matched non-frail controls (1.05+/-0.88 versus 0.53+/-0.39, p=0.04). CXCL-10 expression correlated with IL-6 levels only in frail participants (Spearman correlation coefficient r=0.52, p=0.03). Furthermore, frailty-associated CXCL-10 upregulation was highly correlated with IL-6 elevation, both measured by frail-over-non-frail ratios (r=0.93, p<0.0001). These findings suggest upregulated monocytic expression of CXCL-10 as an important molecular mechanism that contributes to inflammation activation in frail older adults. Therapeutic implications include potential development of CXCL-10-based interventional strategies for the prevention and treatment of frailty in older adults.

Upregulated ex vivo expression of stress-responsive inflammatory pathway genes by LPS-challenged CD14(+) monocytes in frail older adults

Frailty has been increasingly recognized as an important clinical syndrome in old age. The frailty syndrome is characterized by chronic inflammation, decreased functional and physiologic reserve, and increased vulnerability to stressors, leading to disability and mortality. However, molecular mechanisms that contribute to inflammation activation and regulation in frail older adults have not been investigated. To begin to address this, we conducted a pathway-specific gene array analysis of 367 inflammatory pathway genes by lipopolysaccharide (LPS)-challenged CD14(+) monocytes from 32 community-dwelling frail and age-, race-, and sex-paired nonfrail older adults (mean age 83 years, range 72-94). The results showed that ex vivo LPS-challenge induced average 2.0-fold or higher upregulated expression of 116 genes in frail participants and 85 genes in paired nonfrail controls. In addition, frail participants had 2-fold or higher upregulation in LPS-induced expression of 7 stress-responsive genes than nonfrail controls with validation by quantitative real time RT-PCR. These findings suggest upregulated expression of specific stress-responsive genes in monocyte-mediated inflammatory pathway in the syndrome of frailty with potential mechanistic and interventional implications.

ELISA and multiplex technologies for cytokine measurement in inflammation and aging research

Over the last decade there has been an enormous expansion of research focused on defining the role of inflammation in aging, age-related diseases, disability, and frailty. The availability of methods to measure cytokines and other inflammatory mediators or markers with high sensitivity and specificity is critically important. Enzyme-linked immunosorbent assay (ELISA), the most widely used and best validated method, is limited by its ability to measure only a single protein in each sample. Recent developments in serum cytokine quantification technology include multiplex arrays, which offer the potential of better evaluating the complexity and dynamic nature of inflammatory responses and offer substantial cost and sample savings over traditional ELISA measurements. Despite potential advantages of this new technology, experience with these techniques is limited, and it has not emerged to date as the gold standard in inflammatory mediator measurement. This article reviews ELISA and the emerging multiplex technologies, compares the cost and effectiveness of recently developed multiplex arrays with traditional ELISA technology, and provides specific recommendations for investigators interested in measuring serum inflammatory mediators in older adults.

Structural requirements for bone sialoprotein binding and modulation of matrix metalloproteinase-2

Bone sialoprotein (BSP) has been shown to induce limited gelatinase activity in latent matrix metalloproteinase-2 (MMP-2) without removal of the propeptide and to restore enzymatic activity to MMP-2 previously inhibited by tissue inhibitor of matrix metalloproteinase-2 (TIMP2). The current study identifies structural domains in human BSP and MMP-2 that contribute to these interactions. The 26 amino acid domain encoded by exon 4 of BSP is shown by a series of binding and activity assays to be involved in the displacement of MMP-2's propeptide from the active site and thereby inducing the protease activity. Binding assays in conjunction with enzyme activity assays demonstrate that both amino- and carboxy-terminal domains of BSP contribute to restoration of activity to TIMP2-inhibited MMP-2, while the MMP-2 hemopexin domain is not required for reactivation.

Impact on bone of an estrogen receptor-alpha gene loss of function mutation

CONTEXT

The kindred described is the only known instance of a germ line loss of function mutation of estrogen receptor (ER)-alpha.

OBJECTIVE

Our objective was to assess the impact of a loss of function mutation in the ER-alpha gene on histomorphometry, bone volumetric density, bone geometry and skeletal growth, and ER-alpha heterozygosity on spine density and adult height in an extended pedigree.

DESIGN AND PARTICIPANTS

A longitudinal follow-up of the propositus with homozygous loss of function mutation of ER-alpha and single contact evaluation of the kindred were performed.

MAIN OUTCOME MEASURES

Iliac crest bone biopsy and peripheral quantitative computed tomography of propositus with serial measures of areal spine bone mineral density (aBMD) by dual-energy x-ray absorptiometry and bone age were performed. Members of pedigree were evaluated for ER-alpha mutation carrier status and spine aBMD.

RESULTS

Bone biopsy revealed marked osteopenia (cortex: 641 microm), low trabecular volume (10.6%), decreased thickness (76.2 microm), normal trabecular number, and low activation frequency (0.099/yr). Radial periosteal circumference was similar, endosteal circumference larger, and trabecular and cortical volumetric bone mineral density markedly lower (158 and 1092 mg/cm(3), respectively) than controls. Spine aBMD at age 28.5 yr (0.745 g/cm(2)) decreased to 0.684 g/cm(2) (Z score -3.85) in 3.5 yr. Bone age advanced from 15-17.5 yr. Kindred analysis revealed that gene carriers had spine aBMD Z scores less than zero (P = 0.003), but carriers and nonmutant members were similar (-0.84 +/- 0.26 vs. -0.64 +/- 0.16).

CONCLUSION

Homozygous ER-alpha disruption markedly affects bone growth, mineral content, and structure but not periosteal circumference. ER-alpha heterozygosity appears to not impair spine aBMD.

Bone sialoprotein binding to matrix metalloproteinase-2 alters enzyme inhibition kinetics

Bone sialoprotein (BSP) is a secreted glycophosphoprotein normally restricted in expression to skeletal tissue that is also induced by multiple neoplasms in vivo. Previous work has shown that BSP can bind to matrix metalloproteinase-2 (MMP-2). Because of MMP-2 activity in promoting tumor progression, potential therapeutic inhibitors were developed, but clinical trials have been disappointing. The effect of BSP on MMP-2 modulation by inhibitors was determined with purified components and in cell culture. Enzyme inhibition kinetics were studied using a low-molecular weight freely diffusable substrate and purified MMP-2, BSP, and natural (tissue inhibitor of matrix metalloproteinase-2) and synthetic (ilomastat and oleoyl- N-hydroxylamide) inhibitors. We determined parameters of enzyme kinetics by varying substrate concentrations at different fixed inhibitor concentrations added to MMP-2 alone, MMP-2 and BSP, or preformed MMP-2-BSP complexes and solving a general linear mixed inhibition rate equation with a global curve fitting program. Two in vitro angiogenesis model systems employing human umbilical vein endothelial cells (HUVECs) were used to follow BSP modulation of MMP-2 inhibition and tubule formation. The presence of BSP increased the competitive K I values between 15- and 47-fold for natural and synthetic inhibitors. The extent of tubule formation by HUVECs cocultured with dermal fibroblasts was reduced in the presence of inhibitors, while the addition of BSP restored vessel formation. A second HUVEC culture system demonstrated that tubule formation by cells expressing BSP could be inhibited by an activity blocking antibody against MMP-2. BSP modulation of MMP-2 activity and inhibition may define its biological role in promoting tumor progression.

T-lymphocytes expressing CC chemokine receptor-5 are increased in frail older adults

OBJECTIVES

To evaluate the frequencies of T-lymphocytes expressing CC chemokine receptor-5 (CCR5(+) T-cells) and their relationship with frailty in older adults.

DESIGN

Case-control study with an age-, race-, and sex-matched design.

SETTING

General Clinical Research Center.

PARTICIPANTS

Community-dwelling adults aged 72 and older from Baltimore, Maryland.

METHODS

Frailty was determined using five validated criteria: weakness, slow walking speed, fatigue, low physical activity, and weight loss. Those meeting three or more of these five criteria were defined as frail and those with none as nonfrail. Complete blood counts were performed to obtain peripheral lymphocyte counts using an automated (Coulter) counter. Peripheral blood was collected for surface immunofluorescent staining of CCR5 and other T-cell markers.

RESULTS

Twenty-six frail and matched nonfrail participants (mean age+/-standard deviation 83.8+/-5.3, range 72-94) completed the study. Frail participants had higher CCR5(+), CCR5(+)CD8(+), and CCR5(+)CD45RO(-) T-cell counts than matched nonfrail controls (349+/-160/mm(3) vs 194+/-168/mm(3), P=.02; 208+/-98/mm(3) vs 105+/-62/mm(3), P=.02; and 189+/-149/mm(3) vs 52+/-36/mm(3), P=.01; respectively). Furthermore, there was a trend toward graded increase in these T-cell counts across the frailty scores in frail participants (e.g., CCR5(+)CD8(+) counts of 123+/-52/mm(3), 248+/-115/mm(3), and 360+/-215/mm(3) for those with frailty scores of 3, 4, and 5, respectively).

CONCLUSION

These initial results suggest an expansion of the CCR5(+) T-cell subpopulation in frailty. They provide a basis for further characterization of CCR5(+) T-cells and their role in frailty, with potential therapeutic implications.

Small integrin-binding ligand N-linked glycoproteins (SIBLINGs): multifunctional proteins in cancer

Numerous components and pathways are involved in the complex interplay between cancer cells and their environment. The family of glycophosphoproteins comprising osteopontin, bone sialoprotein, dentin matrix protein 1, dentin sialophosphoprotein and matrix extracellular phosphoglycoprotein - small integrin-binding ligand N-linked glycoproteins (SIBLINGs) - are emerging as important players in many stages of cancer progression. From their detection in various human cancers to the demonstration of their key functional roles during malignant transformation, invasion and metastasis, the SIBLINGs are proteins with potential as diagnostic and prognostic tools, as well as new therapeutic targets.

Determination of the elimination half-life of fibroblast growth factor-23

CONTEXT

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic disease caused by mesenchymal tumors that secrete fibroblast growth factor-23 (FGF-23), a newly-described vitamin D and phosphate-regulating hormone. Surgical removal of the tumor, the ectopic source of circulating FGF-23, offers the opportunity to determine the elimination half-life of FGF-23.

OBJECTIVE

The aim of the study was to determine the elimination half-life of FGF-23.

PATIENTS/METHODS

The tumors were removed from three patients with TIO, and serum samples were taken every 30 min for up to 72 h after the operation. FGF-23 was measured by both a C-terminal/intact assay and an intact assay, and the elimination half-life was determined by one phase exponential decay methodology.

SETTING

The Mark O. Hatfield Clinical Research Center of the National Institutes of Health, a tertiary referral clinical research center, was the setting for the study.

RESULTS

The elimination life of FGF-23 as determined by C-terminal/intact and intact assays was 46 +/- 12 and 58 +/- 34 min, respectively.

CONCLUSIONS

The plasma half-life of serum FGF-23 is in the range of 46-58 min.

Activation of (Na++K+)-ATPase induces positive inotropy in intact mouse heart in vivo

OBJECTIVE

We have recently identified an activation site on (Na+ + K+)-ATPase and found that binding of antibody SSA412 to this specific site of the enzyme markedly augments (Na+ + K+)-ATPase catalytic activity. Demonstration of whether activation of (Na+ + K+)-ATPase affects heart function in animal in vivo was the object of this investigation.

METHODS

Male wild-type CD-1 mouse and specific antibody SSA412 were used for the study. A pressure-volume micromanometer-conductance catheter in anesthetized mouse assessed in vivo cardiac functions.

RESULTS

Specific antibody SSA412 infusion in mouse shifted pressure-volume loop leftward with increased stroke volume and enhanced end-systolic elastance. Global systolic parameters such as ejection fraction and cardiac output, and load independent contractile parameters including dP/dtmax/IP, PMX/EDV, Ees, and PRSW, were all increased without any effect on relaxation following administration of SSA412. Cardiac preload indexed by EDV and afterload by ESP did not alter, suggesting that SSA412-enhanced myocardial performance is a direct cardiac effect caused by the activation of (Na+ + K+)-ATPase.

CONCLUSION

Our study provides the first in vivo physiological evidence to demonstrate that activation of (Na+ + K+)-ATPase induces significant positive inotropic effect in intact animal heart. The finding may lead to new therapeutic strategies for the treatment of heart failure.

The role of mutant UDP-N-acetyl-alpha-D-galactosamine-polypeptide N-acetylgalactosaminyltransferase 3 in regulating serum intact fibroblast growth factor 23 and matrix extracellular phosphoglycoprotein in heritable tumoral calcinosis

CONTEXT

Familial tumoral calcinosis (TC) results from disruptions in phosphate metabolism and is characterized by high serum phosphate with normal or elevated 1,25 dihydroxyvitamin vitamin D concentrations and ectopic and vascular calcifications. Recessive loss-of-function mutations in UDP-N-acetyl-alpha-D-galactosamine-polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) and fibroblast growth factor-23 (FGF23) result in TC.

OBJECTIVE

The objective of the study was to determine the relationship between GALNT3 and FGF23 in familial TC.

DESIGN, SETTING, AND PATIENTS

We assessed the major biochemical defects and potential genes involved in patients with TC.

INTERVENTION

Combination therapy consisted of the phosphate binder Sevelamer and the carbonic anhydrase inhibitor acetazolamide.

RESULTS

We report a patient homozygous for a GALNT3 exon 1 deletion, which is predicted to truncate the encoded protein. This patient had high serum FGF23 concentrations when assessed with a C-terminal FGF23 ELISA but low-normal FGF23 levels when tested with an ELISA for intact FGF23 concentrations. Matrix extracellular phosphoglycoprotein has been identified as a possible regulator of phosphate homeostasis. Serum matrix extracellular phosphoglycoprotein levels, however, were normal in the family with GALNT3-TC and a kindred with TC carrying the FGF23 S71G mutation. The tumoral masses of the patient with GALNT3-TC completely resolved after combination therapy.

CONCLUSIONS

Our findings demonstrate that GALNT3 inactivation in patients with TC leads to inadequate production of biologically active FGF23 as the most likely cause of the hyperphosphatemic phenotype. Furthermore, combination therapy may be effective for reducing the tumoral burden associated with familial TC.

Bone sialoprotein mediates the tumor cell-targeted prometastatic activity of transforming growth factor beta in a mouse model of breast cancer

Transforming growth factor betas (TGF-beta) play a dual role in carcinogenesis, functioning as tumor suppressors early in the process, and then switching to act as prometastatic factors in late-stage disease. We have previously shown that high molecular weight TGF-beta antagonists can suppress metastasis without the predicted toxicities. To address the underlying mechanisms, we have used the 4T1 syngeneic mouse model of metastatic breast cancer. Treatment of mice with a monoclonal anti-TGF-beta antibody (1D11) significantly suppressed metastasis of 4T1 cells to the lungs. When metastatic 4T1 cells were recovered from lungs of 1D11-treated and control mice, the most differentially expressed gene was found to be bone sialoprotein (Bsp). Immunostaining confirmed the loss of Bsp protein in 1D11-treated lung metastases, and TGF-beta was shown to regulate and correlate with Bsp expression in vitro. Functionally, knockdown of Bsp in 4T1 cells reduced the ability of TGF-beta to induce local collagen degradation and invasion in vitro, and treatment with recombinant Bsp protected 4T1 cells from complement-mediated lysis. Finally, suppression of Bsp in 4T1 cells reduced metastasis in vivo. We conclude that Bsp is a plausible mediator of at least some of the tumor cell-targeted prometastatic activity of TGF-beta in this model and that Bsp expression in metastases can be successfully suppressed by systemic treatment with anti-TGF-beta antibodies.

Dentin matrix protein 1 enhances invasion potential of colon cancer cells by bridging matrix metalloproteinase-9 to integrins and CD44

The up-regulation of various matrix metalloproteinases (MMP), certain cell receptors such as integrins and CD44, and the SIBLING family of integrin-binding glycophosphoproteins have been reported separately and in various combinations for many types of tumors. The mechanisms by which these different proteins may be interacting and enhancing the ability of a cancer cell to survive and metastasize have become an interesting issue in cancer biology. Dentin matrix protein 1 (DMP1) has been known for a number of years to bind to CD44 and ArgGlyAsp sequence-dependent integrins. This SIBLING was recently shown to be able to specifically bind and activate proMMP-9 and to make MMP-9 much less sensitive to inhibition by tissue inhibitors of metalloproteinases and synthetic inhibitors. In this study, we used a modified Boyden chamber assay to show that DMP1 enhanced the invasiveness of the MMP-9 expressing colon cancer cell line, SW480, through Matrigel in a dose-dependant manner. DMP1 (100 nmol/L) increased invasion 4-fold over controls (86.1 +/- 13.9 versus 22.3 +/- 9.8, P < 0.001). The enhanced invasive potential required the presence of MMP-9 and at least one of the cell surface receptors, CD44, alpha(v)beta(3), or alpha(v)beta(5) integrin. The bridging of MMP-9 to the cell surface receptors was shown by both pull-down and fluorescence activated cell sorting experiments. Because all of these proteins were also shown by immunohistochemistry to be expressed in serial sections of a colon adenocarcinoma, we have hypothesized that the MMP-9/DMP1/cell surface complexes observed to enhance cell invasion in vitro may be aiding metastatic events in vivo.

Fibroblast growth factor-23 is regulated by 1alpha,25-dihydroxyvitamin D

Serum FGF-23 regulation was studied in patients with hypoparathyroidism or pseudohypoparathyroidism treated with calcitriol. Serum FGF-23 levels changed in parallel in response to changes in serum 1,25-D, suggesting that FGF-23 may be regulated by 1,25-D. In addition, the phosphaturic effect of FGF-23 may be diminished in the absence of PTH action on the kidney.

INTRODUCTION

Fibroblast growth factor (FGF)-23 is a recently described hormone that has been shown to be involved in the regulation of phosphate and vitamin D metabolism. The physiologic role of FGF-23 in mineral metabolism and how serum FGF-23 levels are regulated have yet to be elucidated. Three patients with mineral metabolism defects that allowed for the investigation of the regulation of FGF-23 were studied.

MATERIALS AND METHODS

Patient 1 had postsurgical hypoparathyroidism and Munchausen's syndrome and consumed a pharmacologic dose of calcitriol. Patient 2 had postsurgical hypoparathyroidism and fibrous dysplasia of bone. She was treated with increasing doses of calcitriol followed by synthetic PTH(1-34). Patient 3 had pseudohypoparathyroidism type 1B and tertiary hyperparathyroidism. She underwent parathyroidectomy, which was followed by the development of hungry bone syndrome and hypocalcemia, requiring treatment with calcitriol. Serum FGF-23 and serum and urine levels of mineral metabolites were measured in all three patients.

RESULTS

Patient 1 had an acute and marked increase in serum FGF-23 (70 to 670 RU/ml; normal range, 18-108 RU/ml) within 24 h in response to high-dose calcitriol administration. Patient 2 showed stepwise increases in serum FGF-23 from 117 to 824 RU/ml in response to increasing serum levels of 1alpha,25-dihydroxyvitamin D (1,25-D). Finally, before parathyroidectomy, while hypercalcemic, euphosphatemic, with low levels of 1,25-D (10 pg/ml; normal range, 22-67 pg/ml), and with very high serum PTH (863.7 pg/ml; normal range, 6.0-40.0 pg/ml), patient 3 had high serum FGF-23 levels (217 RU/ml). After surgery, while hypocalcemic, euphosphatemic, and with high serum levels of serum 1,25-D (140 pg/ml), FGF-23 levels were higher than preoperative levels (305 RU/ml). It seemed that the phosphaturic effect of FGF-23 was diminished in the absence of PTH or a PTH effect.

CONCLUSIONS

Serum FGF-23 may be regulated by serum 1,25-D, and its phosphaturic effect may be less in the absence of PTH.

Small integrin binding ligand N-linked glycoprotein gene family expression in different cancers

PURPOSE

Members of the small integrin binding ligand N-linked glycoprotein (SIBLING) gene family have the capacity to bind and modulate the activity of matrix metalloproteinases (MMPs). The expression levels of five SIBLING gene family members [bone sialoprotein (BSP), osteopontin (OPN), dentin matrix protein 1 (DMP1), matrix extracellular phosphoglycoprotein (MEPE), and dentin sialophosphoprotein (DSPP)] and certain MMPs were determined using a commercial cancer array.

EXPERIMENTAL DESIGN

Cancer profiling arrays containing normalized cDNA from both tumor and corresponding normal tissues from 241 individual patients were used to screen for SIBLING and MMP expression in nine distinct cancer types.

RESULTS

Significantly elevated expression levels were observed for BSP in cancer of the breast, colon, stomach, rectum, thyroid, and kidney; OPN in cancer of the breast, uterus, colon, ovary, lung, rectum, and thyroid; DMP1 in cancer of the breast, uterus, colon, and lung; and dentin sialophosphoprotein in breast and lung cancer. The degree of correlation between a SIBLING and its partner MMP was found to be significant within a given cancer type (e.g., BSP and MMP-2 in colon cancer, OPN and MMP-3 in ovarian cancer; DMP1 and MMP-9 in lung cancer). The expression levels of SIBLINGs were distinct within subtypes of cancer (e.g., breast ductal tumors compared with lobular tumors). In general, SIBLING expression increased with cancer stage for breast, colon, lung, and rectal cancer.

CONCLUSIONS

These results suggest SIBLINGs as potential markers of early disease progression in a number of different cancer types, some of which currently lack vigorous clinical markers.

Serum levels of matrix extracellular phosphoglycoprotein (MEPE) in normal humans correlate with serum phosphorus, parathyroid hormone and bone mineral density

Matrix extracellular phosphoglycoprotein (MEPE), a member of the Small Integrin Binding Ligand N-linked Glycoprotein (SIBLING) family, is primarily expressed in normal bone and has been proposed as a phosphaturic factor because of high expression and secretion in oncogenic hypophosphatemic osteomalacia tumors. In order to begin to address the role of MEPE in normal human physiology, we developed a competitive ELISA to measure serum levels of MEPE. The ELISA was used to characterize the distribution pattern in a population consisting of 114 normal adult subjects. The mean value of MEPE was 476 +/- 247 ng/ml and levels decreased significantly with increasing age. MEPE levels were also significantly correlated with serum phosphorus and parathyroid hormone (PTH). In addition, MEPE levels correlated significantly with measures of bone mineral density in the femoral neck and total hip in a subset of 50 elderly subjects. The results are consistent with MEPE being involved in phosphate and bone metabolism in a normal population.

Bone Sialoprotein, Matrix Metalloproteinase 2, and v 3 Integrin in Osteotropic Cancer Cell Invasion

BACKGROUND

Bone sialoprotein (BSP) interacts separately with both matrix metalloproteinase 2 (MMP-2) and integrin alpha(v)beta3 and is overexpressed in many metastatic tumors. Its role in tumor biology, however, remains unclear. We investigated whether BSP enhances cancer cell invasiveness by forming a trimolecular complex with MMP-2 and cell-surface integrin alpha(v)beta3.

METHODS

Invasiveness of breast, prostate, lung, and thyroid tumor cell lines was measured with a modified Boyden chamber assay. Binding and co-localization of BSP, MMP-2, and integrin alpha(v)beta3 were investigated with immunoprecipitation and in situ hybridization. All statistical tests were two-sided.

RESULTS

Treatment with BSP increased invasiveness of many breast, prostate, lung, and thyroid cancer cells through Matrigel in a dose-dependent manner. BSP at 50 nM increased the invasiveness of SW-579 thyroid cancer cells (95.2 units, 95% confidence interval [CI] = 90.4 to 100 units) by approximately 10-fold compared with that of untreated control SW-579 cells (9.1 units, 95% CI = 5.7 to 12.5 units) (P<.001). Addition of an inactive mutated BSP, in which BSP's integrin-binding RGD tripeptide was altered, or addition of integrin alpha(v)beta3-blocking antibodies resulted in invasiveness equivalent to that of untreated cells. Inhibiting cellular MMP-2 activity with chemical inhibitors or a specific antibody also blocked BSP-enhanced invasiveness. Osteopontin and dentin matrix protein 1, proteins related to BSP that also bind integrin alpha(v)beta3 and form complexes with other MMPs (but not MMP-2), did not enhance invasiveness. Immunoprecipitation showed that a complex containing BSP, integrin alpha(v)beta3, and MMP-2 formed in vitro. Addition of BSP increased the amount of MMP-2 bound by cells in an integrin-dependent fashion. Co-expression of BSP, integrin alpha(v)beta3, and MMP-2 in papillary thyroid carcinoma cells was shown by in situ hybridization.

CONCLUSION

Cancer cells appear to become more invasive when BSP forms a cell-surface trimolecular complex by linking MMP-2 to integrin alpha(v)beta3.

Evaluation of osteopontin as biomarker for pancreatic adenocarcinoma

OBJECTIVES

Pancreatic adenocarcinoma is a deadly disease with an overall 5-year patient survival of less than 5%. This dismal prognosis of pancreatic cancer is largely due to the advanced stage of the disease at presentation. If pancreatic cancer could be diagnosed more readily and accurately using serum markers, patient survival could theoretically be improved by enabling more patients to avail of surgical resection. One candidate tumor marker recently identified by global gene expression analysis of pancreatic cancer is the secreted glycophosphoprotein osteopontin (OPN). In this study, we evaluate OPN as a serum marker of pancreatic adenocarcinoma.

METHODS

In situ hybridization for OPN was performed on a pancreatic adenocarcinoma tissue microarray. Serum OPN levels were determined in preoperative sera from 50 patients with pancreatic cancer and 22 healthy control individuals by competitive ELISA.

RESULTS

In situ hybridization for OPN performed on a tissue microarray revealed strong OPN mRNA signal in tumor-infiltrating macrophages in 8 of 14 pancreatic adenocarcinomas. In contrast, OPN expression was not seen in the pancreatic cancer cells themselves, nor was it seen in normal pancreatic tissue or in the macrophages distant from the infiltrating cancer. Serum OPN levels, as measured by ELISA, were elevated in the sera of 50 patients with resectable pancreatic adenocarcinoma compared to 22 healthy control individuals (mean +/- SD for OPN was 482 +/- 170 ng/ml and 204 +/- 65 ng/ml, respectively; P < 0.001). Using a cutoff level of 2 SD above the mean for healthy individuals, elevated OPN had sensitivity of 80% and specificity of 97% for pancreatic cancer. In contrast, only 62% of these patients with resectable pancreatic cancer had elevated CA19-9.

CONCLUSIONS

Serum OPN may have utility as a diagnostic marker in patients with pancreatic cancer.

Evaluation of Osteopontin as Biomarker for Pancreatic Adenocarcinoma

Objective: Pancreatic adenocarcinoma is a deadly disease with an overall 5-year patient survival of less than 5%. This dismal prognosis of pancreatic cancer is largely due to the advanced stage of the disease at presentation. If pancreatic cancer could be diagnosed more readily and accurately using serum markers, patient survival could theoretically be improved by enabling more patients to avail of surgical resection. One candidate tumor marker recently identified by global gene expression analysis of pancreatic cancer is the secreted glycophosphoprotein osteopontin (OPN). In this study, we evaluate OPN as a serum marker of pancreatic adenocarcinoma. Methods: In situ hybridization for OPN was performed on a pancreatic adenocarcinoma tissue microarray. Serum OPN levels were determined in preoperative sera from 50 patients with pancreatic cancer and 22 healthy control individuals by competitive ELISA. Results: In situ hybridization for OPN performed on a tissue microarray revealed strong OPN mRNA signal in tumor-infiltrating macrophages in 8 of 14 pancreatic adenocarcinomas. In contrast, OPN expression was not seen in the pancreatic cancer cells themselves, nor was it seen in normal pancreatic tissue or in the macrophages distant from the infiltrating cancer. Serum OPN levels, as measured by ELISA, were elevated in the sera of 50 patients with resectable pancreatic adenocarcinoma compared to 22 healthy control individuals (mean ± SD for OPN was 482 ± 170 ng/ml and 204 ± 65 ng/ml, respectively; P &lt; 0.001). Using a cutoff level of 2 SD above the mean for healthy individuals, elevated OPN had sensitivity of 80% and specificity of 97% for pancreatic cancer. In contrast, only 62% of these patients with resectable pancreatic cancer had elevated CA19-9. Conclusion: Serum OPN may have utility as a diagnostic marker in patients with pancreatic cancer.

Three small integrin‐binding ligand N‐linked glycoproteins (SIBLINGs) bind and activate specific matrix metalloproteinases

Matrix metalloproteinases (MMPs) are critical for development, wound healing, and for the progression of cancer. It is generally accepted that MMPs are secreted in a latent form (proMMP) and are activated only upon removal of their inhibitory propeptides. This report shows that three members of the SIBLING (Small, Integrin-Binding LIgand, N-linked Glycoprotein) family can specifically bind (Kd approximately equal nM) and activate three different MMPs. Binding of SIBLING to their corresponding proMMPs is associated with structural changes as indicated by quenching of intrinsic tryptophan fluorescence, increased susceptibility to plasmin cleavage, and decreased inhibition by specific natural and synthetic inhibitors. Activation includes both making the proMMPs enzymatically active and the reactivation of the TIMP (tissue inhibitors of MMP) inhibited MMPs. Bone sialoprotein specifically binds proMMP-2 and active MMP-2, while osteopontin binds proMMP-3 and active MMP-3, and dentin matrix protein-1 binds proMMP-9 and active MMP-9. Both pro and active MMP-SIBLING complexes are disrupted by the abundant serum protein, complement Factor H, thereby probably limiting SIBLING-mediated activation to regions immediately adjacent to sites of secretion in vivo. These data suggest that the SIBLING family offers an alternative method of controlling the activity of at least three MMPs.

Six genes expressed in bones and teeth encode the current members of the SIBLING family of proteins

Bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), enamelin (ENAM), matrix extracellular phosphoglycoprotein (MEPE), and osteopontin (OPN) are glycophosphoproteins expressed in bones and/or teeth. Direct comparison of their amino acid sequences do not suggest that they belong to a single genetic family, but a detailed analysis of their chromosomal location and gene structure does. Analysis of human brain mRNA by RT-PCR has led to the discovery of two additional exons thereby making it more convincing that MEPE is a member of the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family. We propose that the members of this SIBLING family are extended, flexible proteins in solution that can facilitate the formation of a number of different complexes. For example, OPN can bridge complement Factor H to either an RGD-dependent integrin or to CD44 forming a membrane-bound complex that actively suppresses the alternate complement pathway. Two possible mechanisms for inhibiting the lytic pathway of alternate complement are presented.

FGF-23 in fibrous dysplasia of bone and its relationship to renal phosphate wasting

FGF-23, a novel member of the FGF family, is the product of the gene mutated in autosomal dominant hypophosphatemic rickets (ADHR). FGF-23 has been proposed as a circulating factor causing renal phosphate wasting not only in ADHR (as a result of inadequate degradation), but also in tumor-induced osteomalacia (as a result of excess synthesis by tumor cells). Renal phosphate wasting occurs in approximately 50% of patients with McCune-Albright syndrome (MAS) and fibrous dysplasia of bone (FD), which result from postzygotic mutations of the GNAS1 gene. We found that FGF-23 is produced by normal and FD osteoprogenitors and bone-forming cells in vivo and in vitro. In situ hybridization analysis of FGF-23 mRNA expression identified "fibrous" cells, osteogenic cells, and cells associated with microvascular walls as specific cellular sources of FGF-23 in FD. Serum levels of FGF-23 were increased in FD/MAS patients compared with normal age-matched controls and significantly higher in FD/MAS patients with renal phosphate wasting compared with those without, and correlated with disease burden bone turnover markers commonly used to assess disease activity. Production of FGF-23 by FD tissue may play an important role in the renal phosphate-wasting syndrome associated with FD/MAS.

FGF-23 in fibrous dysplasia of bone and its relationship to renal phosphate wasting

FGF-23, a novel member of the FGF family, is the product of the gene mutated in autosomal dominant hypophosphatemic rickets (ADHR). FGF-23 has been proposed as a circulating factor causing renal phosphate wasting not only in ADHR (as a result of inadequate degradation), but also in tumor-induced osteomalacia (as a result of excess synthesis by tumor cells). Renal phosphate wasting occurs in approximately 50% of patients with McCune-Albright syndrome (MAS) and fibrous dysplasia of bone (FD), which result from postzygotic mutations of the GNAS1 gene. We found that FGF-23 is produced by normal and FD osteoprogenitors and bone-forming cells in vivo and in vitro. In situ hybridization analysis of FGF-23 mRNA expression identified "fibrous" cells, osteogenic cells, and cells associated with microvascular walls as specific cellular sources of FGF-23 in FD. Serum levels of FGF-23 were increased in FD/MAS patients compared with normal age-matched controls and significantly higher in FD/MAS patients with renal phosphate wasting compared with those without, and correlated with disease burden bone turnover markers commonly used to assess disease activity. Production of FGF-23 by FD tissue may play an important role in the renal phosphate-wasting syndrome associated with FD/MAS.

Age-related changes in human bone proteoglycan structure. Impact of osteogenesis imperfecta

Proteoglycans (PGs) are a family of molecules that undergo extensive post-translational modifications that include addition of glycosaminoglycan (GAG) chains as well as N- and O-linked oligosaccharides to the protein core. PG composition and structure have been reported to alter with age. To test whether the post-translational modifications to PGs can serve as in vitro surrogate end point markers for chronological age, the extent of GAG modifications was determined for PGs derived from normal human bone cells of 14 donors (age range, fetal to 60 years). Isolated cells were steady state radiolabeled with (35)SO(4)(2-) and [(3)H]GlcN. For biglycan and decorin, iduronate content was linearly correlated with age (increased 1.5x between fetal and age 60 years). For the syndecan-like heparan sulfate PG, the N-sulfation of post-natal cells increased over 3.5-fold until reaching a plateau during the 4th decade of life. The amount of O-linked oligosaccharides was also found to decrease as a function of increasing normal donor age, whereas the specific activity of the metabolic precursor pool remained constant regardless of donor age. These age-related changes in post-translational modifications were then used to demonstrate that osteoblasts derived from patients with osteogenesis imperfecta did not exhibit facets of a pre-mature aging, but rather were arrested in a fetal-like phenotypic state. A growth matrix rich in thrombospondin altered PG metabolism in osteoblastic cells, resulting in the production and secretion of the fetal-like (rich in O-linked oligosaccharides) forms of decorin and biglycan. This effect was qualitatively different from the effect of transforming growth factor-beta, which predominantly altered GAGs rather than O-linked oligosaccharides. No other Arg-Gly-Asp protein (fibronectin, vitronectin, type I collagen, osteopontin, and bone sialoprotein) showed any detectable effect on PG metabolism in bone cells. These results indicate that a proper matrix stoichiometry is critical for metabolism of PGs.

Three SIBLINGs (small integrin-binding ligand, N-linked glycoproteins) enhance factor H's cofactor activity enabling MCP-like cellular evasion of complement-mediated attack

Previously we have shown that two members of the newly named SIBLING (small integrin-binding ligand, N-linked glycoproteins) family of proteins, bone sialoprotein, and osteopontin, bound first to a cell surface receptor and then to complement Factor H thereby blocking the lytic activity of the alternative pathway of complement. Another member of this family, dentin matrix protein 1, is shown in this paper to be very similar to osteopontin in that it can bind strongly to Factor H (K(a) approximately 1 nm) and block the lytic activity through either the vitronectin receptor (alpha(V)beta(3) integrin) or CD44. Binding of Factor H to SIBLING localized to the cells surface was demonstrated by fluorescence-activated cell sorting. Extensive overlapping fragment analyses suggests that both dentin matrix protein 1 and osteopontin interact with cell surface CD44 through their amino termini. Similar fragments of bone sialoprotein, like the intact protein, did not functionally interact with CD44. All three proteins are shown to act in conjunction with Factor I, a serum protease that, when complexed to appropriate cofactors, stops the lytic pathway by digesting the bound C3b in a series of proteolytic steps. These results show that at least three members of this family confer membrane cofactor protein-like activity (MCP or CD46) upon cells expressing RGD-binding integrins or CD44. The required order of the assembly of the complex suggests that this cofactor activity is limited to short diffusional distances.