ADAM 12 as a first-trimester maternal serum marker in screening for Down syndrome

Role of ADAM and ADAMTS Disintegrin and Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy (NP) involves intricate processes starting with egg fertilization, proceeding to embryo implantation, placentation and gestation, and culminating in parturition. These pregnancy-related processes require marked uteroplacental and vascular remodeling by proteolytic enzymes and metalloproteinases. A disintegrin and metalloproteinase (ADAM) and ADAM with thrombospondin motifs (ADAMTS) are members of the zinc-dependent family of proteinases with highly conserved protein structure and sequence homology, which include a pro-domain, and a metalloproteinase, disintegrin and cysteine-rich domain. In NP, ADAMs and ADAMTS regulate sperm-egg fusion, embryo implantation, trophoblast invasion, placental angiogenesis and spiral arteries remodeling through their ectodomain proteolysis of cell surface cytokines, cadherins and growth factors as well as their adhesion with integrins and cell-cell junction proteins. Preeclampsia (PE) is a serious complication of pregnancy characterized by new-onset hypertension (HTN) in pregnancy (HTN-Preg) at or after 20 weeks of gestation, with or without proteinuria. Insufficient trophoblast invasion of the uterine wall, inadequate expansive remodeling of the spiral arteries, reduced uteroplacental perfusion pressure, and placental ischemia/hypoxia are major initiating events in the pathogenesis of PE. Placental ischemia/hypoxia increase the release of reactive oxygen species (ROS), which lead to aberrant expression/activity of certain ADAMs and ADAMTS. In PE, abnormal expression/activity of specific ADAMs and ADAMTS that function as proteolytic sheddases could alter proangiogenic and growth factors, and promote the release of antiangiogenic factors and inflammatory cytokines into the placenta and maternal circulation leading to generalized inflammation, endothelial cell injury and HTN-Preg, renal injury and proteinuria, and further decreases in uteroplacental blood flow, exaggeration of placental ischemia, and consequently fetal growth restriction. Identifying the role of ADAMs and ADAMTS in NP and PE has led to a better understanding of the underlying molecular and vascular pathways, and advanced the potential for novel biomarkers for prediction and early detection, and new approaches for the management of PE.

From putative brain tumor marker to high cognitive abilities: Emerging roles of a disintegrin and metalloprotease (ADAM) 12 in the brain

ADAM (a disintergin and metalloprotease) 12 is a member of the large family of multidomain metalloprotease-disintegrins, which possess cell-binding and metalloprotease properties. The enzyme is responsible for the shedding of a number of membrane-bound proteins (heparin-binding-EGF, insulin-like growth factor 2-binding proteins 3 and 5, oxytocinase, glycoprotein non-metastatic melanoma protein B and basigin). In rat and human CNS, ADAM12 is predominantly localized in white and gray matter oligodendrocytes. In addition it can be detected in astrocytes, neurons and endothelial cells. Its function in healthy brain is not well established yet, but prominent roles in CNS development, myelination and high cognitive abilities are discussed. There is increasing evidence that ADAM12 is involved in numerous major diseases of the CNS, which are summarized in the present review (brain tumors, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer´s disease, stroke, schizophrenia, autism and bipolar disorder).

First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first trimester ultrasound markers alone, and in combination with first trimester serum tests for the detection of Down's syndrome.

SEARCH METHODS

We carried out extensive literature searches including MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), and The Database of Abstracts of Reviews of Effects (the Cochrane Library 2011, Issue 7). We checked reference lists and published review articles for additional potentially relevant studies.

SELECTION CRITERIA

Studies evaluating tests of first trimester ultrasound screening, alone or in combination with first trimester serum tests (up to 14 weeks' gestation) for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 126 studies (152 publications) involving 1,604,040 fetuses (including 8454 Down's syndrome cases). Studies were generally good quality, although differential verification was common with invasive testing of only high-risk pregnancies. Sixty test combinations were evaluated formed from combinations of 11 different ultrasound markers (nuchal translucency (NT), nasal bone, ductus venosus Doppler, maxillary bone length, fetal heart rate, aberrant right subclavian artery, frontomaxillary facial angle, presence of mitral gap, tricuspid regurgitation, tricuspid blood flow and iliac angle 90 degrees); 12 serum tests (inhibin A, alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (ßhCG), total hCG, pregnancy-associated plasma protein A (PAPP-A), unconjugated oestriol (uE3), disintegrin and metalloprotease 12 (ADAM 12), placental growth factor (PlGF), placental growth hormone (PGH), invasive trophoblast antigen (ITA) (synonymous with hyperglycosylated hCG), growth hormone binding protein (GHBP) and placental protein 13 (PP13)); and maternal age. The most frequently evaluated serum markers in combination with ultrasound markers were PAPP-A and free ßhCG.Comparisons of the 10 most frequently evaluated test strategies showed that a combined NT, PAPP-A, free ßhCG and maternal age test strategy significantly outperformed ultrasound markers alone (with or without maternal age) except nasal bone, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). In both direct and indirect comparisons, the combined NT, PAPP-A, free ßhCG and maternal age test strategy showed superior diagnostic accuracy to an NT and maternal age test strategy (P < 0.0001). Based on the indirect comparison of all available studies for the two tests, the sensitivity (95% confidence interval) estimated at a 5% FPR for the combined NT, PAPP-A, free ßhCG and maternal age test strategy (69 studies; 1,173,853 fetuses including 6010 with Down's syndrome) was 87% (86 to 89) and for the NT and maternal age test strategy (50 studies; 530,874 fetuses including 2701 Down's syndrome pregnancies) was 71% (66 to 75). Combinations of NT with other ultrasound markers, PAPP-A and free ßhCG were evaluated in one or two studies and showed sensitivities of more than 90% and specificities of more than 95%.High-risk populations (defined before screening was done, mainly due to advanced maternal age of 35 years or more, or previous pregnancies affected with Down's syndrome) showed lower detection rates compared to routine screening populations at a 5% FPR. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under-ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting test sensitivity. Conversely, for the NT, PAPP-A, free ßhCG and maternal age test strategy, detection rates and false positive rates increased with maternal age in the five studies that provided data separately for the subset of women aged 35 years or more.

AUTHORS' CONCLUSIONS

Test strategies that combine ultrasound markers with serum markers, especially PAPP-A and free ßhCG, and maternal age were significantly better than those involving only ultrasound markers (with or without maternal age) except nasal bone. They detect about nine out of 10 Down's affected pregnancies for a fixed 5% FPR. Although the absence of nasal bone appeared to have a high diagnostic accuracy, only five out of 10 affected Down's pregnancies were detected at a 1% FPR.

First and second trimester serum tests with and without first trimester ultrasound tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 (or the specific area of chromosome 21 implicated in causing Down's syndrome) rather than two. It is the commonest congenital cause of mental disability. Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal) and false negative screening tests (i.e. a fetus with Down's syndrome will be missed). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester serum markers with and without first trimester ultrasound markers for the detection of Down's syndrome in the antenatal period, as combinations of markers.

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), the Database of Abstracts of Reviews of Effectiveness (the Cochrane Library 25 August 2011), MEDION (25 August 2011), the Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), the National Research Register (Archived 2007), and Health Services Research Projects in Progress database (25 August 2011). We did not apply a diagnostic test search filter. We did forward citation searching in ISI citation indices, Google Scholar and PubMed 'related articles'. We also searched reference lists of retrieved articles SELECTION CRITERIA: Studies evaluating tests of combining first and second trimester maternal serum markers in women up to 24 weeks of gestation for Down's syndrome, with or without first trimester ultrasound markers, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Twenty-two studies (reported in 25 publications) involving 228,615 pregnancies (including 1067 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high risk pregnancies. Ten studies made direct comparisons between tests. Thirty-two different test combinations were evaluated formed from combinations of eight different tests and maternal age; first trimester nuchal translucency (NT) and the serum markers AFP, uE3, total hCG, free βhCG, Inhibin A, PAPP-A and ADAM 12. We looked at tests combining first and second trimester markers with or without ultrasound as complete tests, and we also examined stepwise and contingent strategies.Meta-analysis of the six most frequently evaluated test combinations showed that a test strategy involving maternal age and a combination of first trimester NT and PAPP-A, and second trimester total hCG, uE3, AFP and Inhibin A significantly outperformed other test combinations that involved only one serum marker or NT in the first trimester, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate. However, the evidence was limited in terms of the number of studies evaluating this strategy, and we therefore cannot recommend one single screening strategy.

AUTHORS' CONCLUSIONS

Tests involving first trimester ultrasound with first and second trimester serum markers in combination with maternal age are significantly better than those without ultrasound, or those evaluating first trimester ultrasound in combination with second trimester serum markers, without first trimester serum markers. We cannot make recommendations about a specific strategy on the basis of the small number of studies available.

Prospects of electrochemical immunosensors for early diagnosis of preeclampsia

Preeclampsia is a vascular multisystem disorder that accounts for varying degree of morbidity and mortality of mother and the fetus. This can be significantly averted if diagnosed at an early (18-20 weeks) stage of gestation, as there is no known way to prevent preeclampsia. In spite of extensive work on biomarker discovery, the existing method for its detection is mostly based on colorimetric immunoassays whose sensitivity is ranging in nanomolar range. Further, it has also been observed that change in the expression of a single biomarker is not sufficient to diagnose this condition. So, for early diagnosis (by 18-20 weeks), an immuno-diagnostic platform with detection limits in picomolar range and beyond along with the ability to do simultaneous detection of multiple analyte would be of great importance. A nano-immunosensors with an electrochemical readout system can be a potential alternative that promises for the ultrasensitive detection of analyte with high specificity as well as suitability for on-site analysis. Coupling the lateral flow technology with immunosensors would make it feasible to detect more than one biomarker simultaneously on a microchip. This review intends to summarize the potential preeclampsia biomarkers, limitations of existing diagnostic methods along with the recent advancements, and prospects to develop electrochemical immunosensors for early clinical diagnosis.

Urine tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21, or the specific area of chromosome 21 implicated in causing Down's syndrome, rather than two. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life. The risk of a Down's syndrome affected pregnancy increases with advancing maternal age.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester urine markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), EMBASE (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2011, Issue 7), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (archived 2007), Health Services Research Projects in Progress database (25 August 2011). We studied reference lists and published review articles.

SELECTION CRITERIA

Studies evaluating tests of maternal urine in women up to 24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC (receiver operating characteristic) meta-analytical methods to analyse test performance and compare test accuracy. We performed analysis of studies allowing direct comparison between tests. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 19 studies involving 18,013 pregnancies (including 527 with Down's syndrome). Studies were generally of high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Twenty-four test combinations were evaluated formed from combinations of the following seven different markers with and without maternal age: AFP (alpha-fetoprotein), ITA (invasive trophoblast antigen), ß-core fragment, free ßhCG (beta human chorionic gonadotrophin), total hCG, oestriol, gonadotropin peptide and various marker ratios. The strategies evaluated included three double tests and seven single tests in combination with maternal age, and one triple test, two double tests and 11 single tests without maternal age. Twelve of the 19 studies only evaluated the performance of a single test strategy while the remaining seven evaluated at least two test strategies. Two marker combinations were evaluated in more than four studies; second trimester ß-core fragment (six studies), and second trimester ß-core fragment with maternal age (five studies).In direct test comparisons, for a 5% false positive rate (FPR), the diagnostic accuracy of the double marker second trimester ß-core fragment and oestriol with maternal age test combination was significantly better (ratio of diagnostic odds ratio (RDOR): 2.2 (95% confidence interval (CI) 1.1 to 4.5), P = 0.02) (summary sensitivity of 73% (CI 57 to 85) at a cut-point of 5% FPR) than that of the single marker test strategy of second trimester ß-core fragment and maternal age (summary sensitivity of 56% (CI 45 to 66) at a cut-point of 5% FPR), but was not significantly better (RDOR: 1.5 (0.8 to 2.8), P = 0.21) than that of the second trimester ß-core fragment to oestriol ratio and maternal age test strategy (summary sensitivity of 71% (CI 51 to 86) at a cut-point of 5% FPR).

AUTHORS' CONCLUSIONS

Tests involving second trimester ß-core fragment and oestriol with maternal age are significantly more sensitive than the single marker second trimester ß-core fragment and maternal age, however, there were few studies. There is a paucity of evidence available to support the use of urine testing for Down's syndrome screening in clinical practice where alternatives are available.

First trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. However, no test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

The aim of this review was to estimate and compare the accuracy of first trimester serum markers for the detection of Down's syndrome in the antenatal period, both as individual markers and as combinations of markers. Accuracy is described by the proportion of fetuses with Down's syndrome detected by screening before birth (sensitivity or detection rate) and the proportion of women with a low risk (normal) screening test result who subsequently had a baby unaffected by Down's syndrome (specificity).

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 25 August 2011), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (Archived 2007), Health Services Research Projects in Progress database (25 August 2011). We did forward citation searching ISI citation indices, Google Scholar and PubMed 'related articles'. We did not apply a diagnostic test search filter. We also searched reference lists and published review articles.  

SELECTION CRITERIA

We included studies in which all women from a given population had one or more index test(s) compared to a reference standard (either chromosomal verification or macroscopic postnatal inspection). Both consecutive series and diagnostic case-control study designs were included. Randomised trials where individuals were randomised to different screening strategies and all verified using a reference standard were also eligible for inclusion. Studies in which test strategies were compared head-to-head either in the same women, or between randomised groups were identified for inclusion in separate comparisons of test strategies. We excluded studies if they included less than five Down's syndrome cases, or more than 20% of participants were not followed up.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC meta-analytical methods or random-effects logistic regression methods to analyse test performance and compare test accuracy as appropriate. Analyses of studies allowing direct and indirect comparisons between tests were undertaken.

MAIN RESULTS

We included 56 studies (reported in 68 publications) involving 204,759 pregnancies (including 2113 with Down's syndrome). Studies were generally of good quality, although differential verification was common with invasive testing of only high-risk pregnancies. We evaluated 78 test combinations formed from combinations of 18 different tests, with or without maternal age; ADAM12 (a disintegrin and metalloprotease), AFP (alpha-fetoprotein), inhibin, PAPP-A (pregnancy-associated plasma protein A, ITA (invasive trophoblast antigen), free βhCG (beta human chorionic gonadotrophin), PlGF (placental growth factor), SP1 (Schwangerschafts protein 1), total hCG, progesterone, uE3 (unconjugated oestriol), GHBP (growth hormone binding protein), PGH (placental growth hormone), hyperglycosylated hCG, ProMBP (proform of eosinophil major basic protein), hPL (human placental lactogen), (free αhCG, and free ßhCG to AFP ratio. Direct comparisons between two or more tests were made in 27 studies.Meta-analysis of the nine best performing or frequently evaluated test combinations showed that a test strategy involving maternal age and a double marker combination of PAPP-A and free ßhCG significantly outperformed the individual markers (with or without maternal age) detecting about seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). Limited evidence suggested that marker combinations involving PAPP-A may be more sensitive than those without PAPP-A.

AUTHORS' CONCLUSIONS

Tests involving two markers in combination with maternal age, specifically PAPP-A, free βhCG and maternal age are significantly better than those involving single markers with and without age. They detect seven out of 10 Down's affected pregnancies for a fixed 5% FPR. The addition of further markers (triple tests) has not been shown to be statistically superior; the studies included are small with limited power to detect a difference.The screening blood tests themselves have no adverse effects for the woman, over and above the risks of a routine blood test. However some women who have a 'high risk' screening test result, and are given amniocentesis or chorionic villus sampling (CVS) have a risk of miscarrying a baby unaffected by Down's. Parents will need to weigh up this risk when deciding whether or not to have an amniocentesis or CVS following a 'high risk' screening test result.

A disintegrin and metalloproteinase-12 (ADAM12): function, roles in disease progression, and clinical implications

BACKGROUND

A disintegrin and metalloproteinase-12 (ADAM12) is a member of the greater ADAM family of enzymes: these are multifunctional, generally membrane-bound, zinc proteases for which there are forty genes known (21 of these appearing in humans). ADAM12 has been implicated in the pathogenesis of various cancers, liver fibrogenesis, hypertension, and asthma, and its elevation or decrease in human serum has been linked to these and other physiological/pathological conditions.

SCOPE

In this review, we begin with a brief overview of the ADAM family of enzymes and protein structure. We then discuss the role of ADAM12 in the progression and/or diagnosis of various disease conditions, and we will conclude with an exploration of currently known natural and synthetic inhibitors.

MAJOR CONCLUSION

ADAM12 has potential to emerge as a successful drug target, although targeting the metalloproteinase domain with any specificity will be difficult to achieve due to structural similarity between the members of the ADAM and MMP family of enzymes. Overall, more research is required to establish ADAM12 being as a highly desirable biomarker and drug target of different diseases, and their selective inhibitors as potential therapeutic agents.

GENERAL SIGNIFICANCE

Given the appearance of elevated levels of ADAM12 in various diseases, particularly breast cancer, our understanding of this enzyme both as a biomarker and a potential drug target could help make significant inroads into both early diagnosis and treatment of disease.

Evaluation of ADAM-12 as a diagnostic biomarker of ectopic pregnancy in women with a pregnancy of unknown location

Background

Ectopic pregnancy (EP) remains the most life-threatening acute condition in modern gynaecology. It remains difficult to diagnose early and accurately. Women often present at emergency departments in early pregnancy with a ‘pregnancy of unknown location’ (PUL) and diagnosis/exclusion of EP is challenging due to a lack of reliable biomarkers. Recent studies suggest that serum levels of a disintegrin and metalloprotease protein-12 (ADAM-12) can be used differentiate EP from viable intrauterine pregnancy (VIUP). Here we describe a prospective study evaluating the performance of ADAM-12 in differentiating EP from the full spectrum of alternative PUL outcomes in an independent patient cohort.

Methodology/Principal Findings

Sera were collected from 120 patients at their first clinical presentation with a PUL and assayed for ADAM-12 by ELISA. Patients were categorized according to final pregnancy outcomes. Serum ADAM-12 concentrations were increased in women with histologically-confirmed EP (median 442 pg/mL; 25%–75% percentile 232–783 pg/mL) compared to women with VIUP (256 pg/mL; 168–442 pg/mL) or miscarriage (192 pg/mL; 133–476 pg/mL). Serum ADAM-12 did not differentiate histologically-confirmed EP from spontaneously resolving PUL (srPUL) (416 pg/mL; 154–608 pg/mL). The diagnostic potential of ADAM-12 was only significant when ‘ambiguous’ PUL outcomes were excluded from the analysis (AROC = 0.6633; P = 0.03901).

Conclusions/Significance

When measured in isolation, ADAM-12 levels had limited value as a diagnostic biomarker for EP in our patient cohort. The development of a reliable serum biomarker-based test for EP remains an ongoing challenge.

Second trimester serum tests for Down's Syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 - or the specific area of chromosome 21 implicated in causing Down's syndrome - rather than two. It is the commonest congenital cause of mental retardation. Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  

OBJECTIVES

To estimate and compare the accuracy of second trimester serum markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to May 2007), EMBASE (1980 to 18 May 2007), BIOSIS via EDINA (1985 to 18 May 2007), CINAHL via OVID (1982 to 18 May 2007), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2007, Issue 1), MEDION (May 2007), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (May 2007), The National Research Register (May 2007), Health Services Research Projects in Progress database (May 2007). We studied reference lists and published review articles.  

SELECTION CRITERIA

Studies evaluating tests of maternal serum in women at 14-24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Fifty-nine studies involving 341,261 pregnancies (including 1,994 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Seventeen studies made direct comparisons between tests. Fifty-four test combinations were evaluated formed from combinations of 12 different tests and maternal age; alpha-fetoprotein (AFP), unconjugated oestriol (uE3), total human chorionic gonadotrophin (hCG), free beta human chorionic gonadotrophin (βhCG), free alpha human chorionic gonadotrophin (αhCG), Inhibin A, SP2, CA125, troponin, pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PGF) and proform of eosinophil major basic protein (ProMBP).Meta-analysis of 12 best performing or frequently evaluated test combinations showed double and triple tests (involving AFP, uE3, total hCG, free βhCG) significantly outperform individual markers, detecting six to seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate. Tests additionally involving inhibin performed best (eight out of every 10 Down's syndrome pregnancies) but were not shown to be significantly better than standard triple tests in direct comparisons. Significantly lower sensitivity occurred in women over the age of 35 years. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting the accuracy of the sensitivity.

AUTHORS' CONCLUSIONS

Tests involving two or more markers in combination with maternal age are significantly more sensitive than those involving one marker. The value of combining four or more tests or including inhibin have not been proven to show statistically significant improvement. Further study is required to investigate reduced test performance in women aged over 35 and the impact of differential pregnancy loss on study findings.

Modeling Down syndrome screening performance using first-trimester serum markers

OBJECTIVE

To evaluate the modeled predictive value of three current screening markers (pregnancy-associated plasma protein-A (PAPP-A), free β-human chorionic gonadotropin (free β-hCG), and nuchal translucency (NT)) and four potential screening markers (a disintegrin and metalloprotease 12 (ADAM12), total hCG, placental protein 13 (PP13), and placental growth factor (PlGF)) for Down syndrome using different screening strategies.

METHODS

All markers were measured in stored first-trimester serum of 151 Down syndrome cases and 847 controls. All marker levels were expressed as gestational age-specific multiples of the median (MoMs) and comparisons were made using the Mann-Whitney U-test. Detection rates (DRs) for fixed false-positive rates (FPRs) were modeled using different screening strategies.

RESULTS

Significantly different median MoMs for Down syndrome cases compared to controls were found for PAPP-A (0.49 vs. 1.00; P < 0.0001), free β-hCG (1.70 vs. 1.01; P < 0.0001), ADAM12 (0.89 vs. 1.00; P < 0.0001), total hCG (1.28 vs. 1.00; P < 0.0001), PlGF (0.80 vs. 1.00; P < 0.0001) and NT (1.74 vs. 1.01; P < 0.0001). The lower PP13 MoM in Down syndrome cases (0.91 vs. 1.00) was not statistically significant (P = 0.061). Adding the four new markers to the current screening strategy (i.e. first-trimester combined test) led to an increase in DR from 77% to 80% at a 5% FPR. The modeled application of a two-sample screening strategy (with some markers assessed early and others later in the first trimester) increased the DR to 89%. In a two-step contingent screening model, using an intermediate risk range of 1 in 100 to 1 in 2000 at biochemical screening (using all markers), the overall DR was 77%, but it was predicted that only 33% of women would require referral for NT measurement.

CONCLUSIONS

First-trimester Down syndrome screening may be improved by adding new markers to the current screening test and by applying different screening strategies. The application of a two-sample screening model resulted in the highest predicted DR, but this should be confirmed in population-based prospective studies.

Screening for pre-eclampsia--lessons from aneuploidy screening

BACKGROUND

Antenatal screening for aneuploidy is an established routine clinical practice worldwide. The same statistical methodology, developed and refined over three decades, might be adapted to screening for pre-eclampsia.

METHODS

The published literature is reviewed for evidence that the methodology is valid for pre-eclampsia using first trimester maternal serum PP13, PAPP-A, PlGF, ADAM12 and inhibin A, together with MAP and uterine artery Doppler PI. Risk is estimated for both early onset pre-eclampsia, requiring delivery before 34 weeks, or late onset disease. Prior risk from the background prevalence multiplied by likelihood ratios (LRs) for ethnicity, parity, adiposity and family history is multiplied by an LR from the screening marker profile. Markers are expressed in multiples of the gestation-specific median and adjusted for body mass, ethnicity and smoking status as appropriate. A standardized population with a fixed distribution of risk factors and a multi-variate Gaussian model of marker profiles is used to predict performance.

RESULTS

There is sufficient published data to estimate individual risks reasonably well. Modeling predicts that using PAPP-A and one other serum marker, together with the physical markers more than two-thirds of early and one-third of late onset cases can be detected by classifying less than 2% of pregnancies as high risk; three-quarters of early case could be detected with a 5% high risk rate.

CONCLUSION

Whilst more data on some markers is still required modeling so far suggests that extending first trimester aneuploidy screening programs to include pre-eclampsia screening would yield a high detection. However, prospective studies are needed to verify the model predictions.

First trimester screening for trisomy 21 in gestational week 8-10 by ADAM12-S as a maternal serum marker

BACKGROUND

A disintegrin and metalloprotease 12 (ADAM12-S) has previously been reported to be significantly reduced in maternal serum from women with fetal aneuploidy early in the first trimester and to significantly improve the quality of risk assessment for fetal trisomy 21 in prenatal screening. The aim of this study was to determine whether ADAM12-S is a useful serum marker for fetal trisomy 21 using the mixture model.

METHOD

In this case control study ADAM12-S was measured by KRYPTOR ADAM12-S immunoassay in maternal serum from gestational weeks 8 to 11 in 46 samples of fetal trisomy 21 and in 645 controls. Comparison of sensitivity and specificity of first trimester screening for fetal trisomy 21 with or without ADAM12-S included in the risk assessment using the mixture model.

RESULTS

The concentration of ADAM12-S increased from week 8 to 11 and was negatively correlated with maternal weight. Log MoM ADAM12-S was positively correlated with log MoM PAPP-A (r = 0.39, P < 0.001), and with log MoM free beta hCG (r = 0.21, P < 0.001). The median ADAM12-S MoM in cases of fetal trisomy 21 in gestational week 8 was 0.66 increasing to approx. 0.9 MoM in week 9 and 10. The use of ADAM12-S along with biochemical markers from the combined test (PAPP-A, free beta hCG) with or without nuchal translucency measurement did not affect the detection rate or false positive rate of fetal aneuploidy as compared to routine screening using PAPP-A and free β-hCG with or without nuchal translucency.

CONCLUSION

The data show moderately decreased levels of ADAM12-S in cases of fetal aneuploidy in gestational weeks 8-11. However, including ADAM12-S in the routine risk does not improve the performance of first trimester screening for fetal trisomy 21.

ADAM12 is an effective marker in the second trimester of pregnancy for prenatal screening of Down syndrome

OBJECTIVE

To estimate the use of maternal serum ADAM12 as a second-trimester Down syndrome serum marker.

METHODS

Samples from a total of 46 Down syndrome pregnancies and 184 unaffected singleton pregnancies matched for gestational age and maternal weight were retrieved from storage and measured for ADAM12; 35 false-positive pregnancies were included among the controls to assess reductions in false-positive rates by inclusion of ADAM12 in the risk calculation of an algorithm that used alpha-fetoprotein (AFP) and human chorionic gonadotrophin (hCG) (double screen).

RESULTS

ADAM12 was measured and expressed as multiple of the gestation-specific median (MoM) and corrected for maternal weight. The median ADAM12 level in the affected pregnancies was 1.26 MoM compared with 1.0 MoM in the unaffected control pregnancies (p < 0.05). In unaffected pregnancies, there was a significant correlation between ADAM12 and AFP (r = 0.314) but not hCG (r = 0.018). Statistical modeling predicted that ADAM12 as a second serum marker could increase the detection rate from 48 to 85%, while reducing the false-negative and false-positive rates.

CONCLUSION

ADAM12 can be used as an effective second-trimester serum marker for prenatal screening of Down syndrome.

ADAM 12 may be used to reduce the false positive rate of first trimester combined screening for Down syndrome

BACKGROUND

ADAM12 has been shown to be an efficient maternal serum marker for Down syndrome (DS) in the first trimester; but recent studies, using a second generation assay, have not confirmed these findings. We examined the efficiency of a second generation assay for ADAM12.

MATERIALS AND METHODS

ADAM12 concentrations were determined in 28 first trimester DS and 503 control pregnancies using a novel Research Delfia ADAM12 kit. Log10MoM distributions of ADAM12 and correlations with other markers were established. Population performance of screening was estimated by Monte Carlo simulation.

RESULTS

ADAM12 was significantly reduced in the first trimester in DS pregnancies with a log10MoM of -0.1621 (equivalent to 0.68 MoM) (p < 0.001). The reduction decreased with advancing gestational age. ADAM12 used with PAPP-A + hCG beta + NT (CUB screening) increased the detection rate (DR) from 86% to 89% for a false positive rate (FPR) of 5%. When used for a fixed DR of 90%, the addition of ADAM12 resulted in a 25% reduction of the FPR.

CONCLUSION

ADAM12 is a moderately effective DS marker. It is not a cost-effective addition to CUB screening, but may be used to reduce the FPR in selected high-risk cases.

Free leptin index and PAPP-A: a first trimester maternal serum screening test for pre-eclampsia

BACKGROUND

Prophylaxis with low-dose aspirin may reduce the risk of pre-eclampsia (PE) if introduced in first trimester. The performance of first trimester maternal serum screening for PE using free leptin index (fLI) and PAPP-A, where fLI = leptin/leptin soluble receptor was studied.

METHODS

First trimester serum samples from 126 PE pregnancies and 289 control pregnancies were studied. fLI and PAPP-A were converted into gestational age and maternal weight independent log MoM values of PAPP-A and fLI. The screening performance of markers was studied by receiver-operator-characteristics curves. The performance of population screening was estimated by Monte Carlo simulation.

RESULTS

fLI was significantly (p < 0.001) elevated [mean log MoM 0.2165 (SD: 0.2604)] compared to controls [mean log MoM -0.0368 (SD: 0.3132)] and PAPP-A was significantly (p < 0.001) reduced [mean log MoM -0.0133 (SD: 0.2661)] compared to controls [mean log MoM 0.0474 (SD: 0.2521)] in PE pregnancies. There was no correlation between fLI and PAPP-A in control or PE pregnancies. Combined fLI and PAPP-A screening for PE had estimated population detection rates of 22% and 35% for false positives rates of 6% and 12%, respectively.

CONCLUSION

Combining PAPP-A and fLI improves screening performance for PE compared to single marker screening.

Maternal serum ADAM12 in Chinese women undergoing screening for aneuploidy in the first trimester

OBJECTIVE

To evaluate the potential of maternal serum using a disintegrin and metalloprotease 12 (ADAM12) as a marker for Trisomy 21 in Chinese pregnant women.

METHODS

Serum samples were collected and stored from women having a viable singleton pregnancy undergoing first trimester screening for Trisomy 21 between 2006 and 2007. Serum concentration of ADAM12 was measured using an automated time-solved immuno-fluorometric assay from 608 stored serum samples (601 Euploidy and 7 Trisomy 21). Regression analysis was used to determine the expected median in Euploidy pregnancies after adjusting for pregnancy characteristics. The level of ADAM12 MoM was compared between Trisomy 21 and Euploidy pregnancies. Expected median levels in Chinese were compared to that published for Caucasians and Afro-Caribbeans.

RESULTS

In Euploidy pregnancies, the concentration of ADAM12 increased with CRL and decreased with maternal weight. The expected median level of ADAM12 in Chinese was significantly lower than Caucasian and Afro-Caribbeans (F=14.2, p<0.0001). There was a significant correlation between log10ADAM12 MoM both log10 pregnancy-associated plasma protein A MoMs (r=0.46; p<0.001) and log10free βhCG MoMs (r=0.08; p=0.048). The median ADAM12 MoM in Trisomy 21 pregnancies was not significantly different from that in Euploidy pregnancies (z=0.18; p=0.88).

CONCLUSION

ADAM12 concentrations in Chinese are lower than those of Caucasians and Afro-Carribeans; that ADAM12 MoM levels in Euploidy and Trisomy 21 pregnancies were not statistically different.

Comparison of first-trimester contingent screening strategies for Down syndrome

OBJECTIVE

To assess the relative performance of a multi-stage first-trimester screening protocol for fetal Down syndrome.

METHODS

Data from 10,767 women who underwent combined ultrasound and biochemistry (BC) screening in the first trimester were reanalyzed using a contingent model approach. Amongst the 10,854 fetuses with known outcome, 32 had Down syndrome, 232 had other abnormalities and 10,590 were unaffected. Nuchal translucency (NT), BC and combined (NT-BC) gestational age-specific risks were calculated for each individual using The Fetal Medicine Foundation risk calculation algorithms (Mixture Model and Biochemistry). Individual patients were categorized as at low, high or intermediate risk according to one of the following three strategies. In 'Strategy-NT-BC' initial screening was performed using both NT and BC. In 'Strategy-BC' initial screening was undertaken using maternal serum markers followed by NT assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000) while in 'Strategy-NT' initial screening was undertaken using NT followed by serum marker assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000). The nasal bone was assessed in those with an intermediate risk as the final stage in each of the three strategies. Those with an adjusted risk of 1 in 100 or higher after nasal bone assessment were reclassified as high risk. Detection and false-positive rates were compared between differing strategies in our local population, and this analysis was also performed with the maternal age for our population standardized to the distribution found in England and Wales.

RESULTS

In our local population the detection rate for a 5% false-positive rate using a combined screening policy (NT-BC) was 88% (95% CI, 75.3-98.9%), and 2.3% had an absent nasal bone. The respective detection rate and false-positive rate of the three multi-stage screening strategies were: Strategy-NT-BC: 87.5 and 2.5%; Strategy-BC: 87.5 and 5%; Strategy-NT: 84.4 and 2.9%. In the contingent Strategy-BC only 29% of those initially screened using serum markers required an NT scan. If the model were applied to a hypothetical obstetric population standardized to the maternal age distribution in England and Wales, the detection and false-positive rates of the same three screening strategies would be: Strategy-NT-BC: 86.2 and 1.9%; Strategy-BC: 82.8 and 4%; Strategy-NT: 75.8 and 2.3%, respectively.

CONCLUSION

First-trimester contingent screening provides detection and false-positive rates comparable to those achieved using combined screening, but could be used to significantly reduce the number of scans performed.

First trimester maternal serum ADAM12s levels in twin pregnancies

BACKGROUND

A disintegrin and metalloprotease 12s (ADAM12s) is a potential first trimester serum marker for fetal trisomy and adverse pregnancy outcome in singletons. In this study, ADAM12s levels in first trimester serum of uncomplicated and complicated twins were evaluated.

METHODS

ADAM12s was studied in maternal serum of 215 twin pregnancies, collected between 2004 and 2008. ADAM12s was measured 'blind to outcome' using AutoDelfia (PerkinElmer, Turku, Finland). As a reference, data from 2423 singletons were used.

RESULTS

The median ADAM12s level was increased in euploid twins [1.61 multiples of the median (MoM); n = 209] compared with singletons. The median ADAM12s MoM was significantly lower in monochorionic (1.36 MoM; n = 41) compared with dichorionic twins (1.67 MoM; n = 168) (Mann-Whitney U test, p = 0.005). Trisomy 21 was identified in two pregnancies. Median ADAM12s MoM in twins complicated by hypertensive disorders (1.77 MoM, n = 35) or small for gestational age fetus (1.54 MoM; n = 24) was not significantly different from uncomplicated twins (1.64 MoM; n = 134).

CONCLUSION

Median ADAM12s MoM in euploid twins was increased compared with singletons. Monochorionic had significantly lower median ADAM12s MoM than dichorionic twins. Median ADAM12s MoMs were not significantly different in twins complicated by hypertensive disorders or small for gestational age fetus compared with uncomplicated twins.

ADAM12s as a first-trimester screening marker of trisomy

OBJECTIVE

To evaluate the potential of maternal serum A Disintegrin And Metalloprotease 12-S (ADAM12s) as an additional marker for the combined test in the Dutch first-trimester national Down syndrome (DS) screening program.

METHODS

Serum samples were collected between 2004 and 2007 as part of the national program. A total of 218 singleton cases of trisomy 21 (DS), 62 trisomy 18 (Edwards syndrome) and 29 trisomy 13 (Patau syndrome) were identified. All cases were matched with controls for gestation, maternal weight and maternal age. The serum concentration of ADAM12s was determined 'blind' to outcome and expressed in multiples of the gestation-specific median for controls (MoM).

RESULTS

The median ADAM12s was 1.00 MoM in controls and in the DS cases at 8, 9, 10, 11, 12, 13 weeks it was 0.45 (n = 3), 0.73 (22), 0.74 (53), 0.85 (37), 0.92 (71), 1.06 (32) MoM, respectively. The median for trisomy 18 was 0.85 MoM and for trisomy 13 0.63 MoM.

CONCLUSION

The ADAM12s MoM values were clearly reduced in early first-trimester for all trisomies. However, the screening performance for DS did not greatly improve adding ADAM12s. ADAM12s could be an additional biochemical marker for first-trimester screening for trisomies other than DS.

Effect of a new marker, ADAM12, on Down risk figures in first trimester screening

OBJECTIVE

To investigate whether incorporating the measurement of ADAM12 in the risk calculation program LifeCycle, can improve Down screening in the first trimester.

METHODS

In a retrospective case control study, maternal serum ADAM12 concentrations were measured and compared in Down syndrome cases (n = 53) and in controls (n = 226) obtained from first trimester (9-12 weeks) screening samples in Oulu and Kuopio University Hospitals. Median concentration ( microg/l), observed and regressed (weight corrected) MoMs of ADAM12 were calculated.

RESULTS

There was a significant difference in ADAM12 levels between Downs and controls during the pregnancy weeks 9 + 0 to 10 + 6, but not thereafter. By adding ADAM12 to the marker set used in the risk calculation program, one screening false negative Down syndrome case occurred in the affected population, which did not alter false positive rate.

CONCLUSION

Adding ADAM12 as a parameter in Down screening did not cause radical changes in the risk value. The test might be useful at 9 and 10 weeks in which it might have the potential to improve the performance of the risk assessment especially for women receiving a result close to the high-risk cut-off. The real influence of ADAM12 remains to be elucidated in larger studies incorporating ADAM12 to the risk calculation program.

ADAM12 localizes with c-Src to actin-rich structures at the cell periphery and regulates Src kinase activity

ADAM12 is an active metalloprotease playing an important role in tumour progression. Human ADAM12 exists in two splice variants: a long transmembrane form, ADAM12-L, and a secreted form, ADAM12-S. The subcellular localization of ADAM12-L is tightly regulated and involves intracellular interaction partners and signalling proteins. We demonstrate here a c-Src-dependent redistribution of ADAM12-L from perinuclear areas to actin-rich Src-positive structures at the cell periphery, and identified two separate c-Src binding sites in the cytoplasmic tail of ADAM12-L that interact with the SH3 domain of c-Src with different binding affinities. The association between ADAM12-L and c-Src is transient, but greatly stabilized when the c-Src kinase activity is disrupted. In agreement with this observation, kinase-active forms of c-Src induce ADAM12-L tyrosine phosphorylation. Interestingly, ADAM12-L was also found to enhance Src kinase activity in response to external signals, such as integrin engagement. Thus, we suggest that activated c-Src binds, phosphorylates, and redistributes ADAM12-L to specific sites at the cell periphery, which may in turn promote signalling mechanisms regulating cellular processes with importance in cancer.

Potential markers of preeclampsia--a review

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. The early identification of patients with an increased risk for preeclampsia is therefore one of the most important goals in obstetrics. The availability of highly sensitive and specific physiologic and biochemical markers would allow not only the detection of patients at risk but also permit a close surveillance, an exact diagnosis, timely intervention (e.g. lung maturation), as well as simplified recruitment for future studies looking at therapeutic medications and additional prospective markers. Today, several markers may offer the potential to be used, most likely in a combinatory analysis, as predictors or diagnostic tools. We present here the current knowledge on the biology of preeclampsia and review several biochemical markers which may be used to monitor preeclampsia in a future, that, we hope, is not to distant from today.

ADAM12 as a marker of trisomy 18 in the first and second trimester of pregnancy

BACKGROUND

ADAM12 (a disintegrin and metalloprotease 12) is a placentally derived glycoprotein that appears to be involved in growth and differentiation. The maternal serum concentration of ADAM12 appears to be a very good marker of trisomy 21 in the early first trimester when levels are reduced, and in the second trimester around 16-18 weeks levels are elevated. One small preliminary study of first trimester pregnancies with trisomy 18 found reduced levels in the maternal serum, and we examine herein the potential of ADAM12 as a marker of trisomy 18 in both the first and second trimester of pregnancy.

MATERIALS AND METHODS

The concentration of ADAM12 was determined by a time-resolved immunofluorometric assay in 132 first and 12 second trimester cases of trisomy 18, and 389 first and 341 second trimester gestational age-matched control pregnancies. Medians of normal pregnancies were established by polynomial regression and used to determine the population distribution parameters for the trisomy 18 and control groups. Correlation with previously established pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG) multiples of the median (MoMs) and nuchal translucency thickness (NT) MoM were determined and used to model the performance of first trimester screening with ADAM12 in combination with other first trimester markers.

RESULTS

The maternal serum concentration of ADAM12 in the first trimester was significantly reduced with a median MoM of 0.829 (p < 0.001) and a mean log10 MoM SD of 0.2663 compared to 0.3353 in the controls. In the second trimester small series ADAM12 was significantly increased with a median MoM of 2.09 (p = 0.001) and a mean log10 MoM SD of 0.2607 compared to 0.4318 in controls. There was a significant correlation of ADAM12 MoM with gestational age (r = 0.510) in trisomy 18 cases, and the median MoM increased from 0.51 at 10 weeks to 1.28 at 13 weeks and 2.09 across the 14-18 week window. ADAM12 was correlated with PAPP-A (r = 0.1918) in the first trimester of cases with trisomy 18 but less so with NT (r = 0.1594) and free beta-hCG (r = 0.0938). Modeled detection rates incorporating ADAM12, free beta-hCG, and NT were 92% at 1% false positive rate (88% at 0.5%) A combination of all four markers had a detection rate of 96.5% at a false positive rate of 1% (95% at 0.5%).

CONCLUSION

ADAM12 may be a useful addition to early screening for trisomy 18 alongside other chromosomal anomalies, particularly if biochemical screening can occur before 10 weeks.

Maternal serum ADAM12 (A disintegrin and metalloprotease) in chromosomally abnormal pregnancy at 11-13 weeks

OBJECTIVE

The objective of this study was to investigate the potential value of ADAM12 (A disintegrin and metalloprotease) in first-trimester screening for trisomy 21 and other major chromosomal abnormalities.

STUDY DESIGN

The concentration of ADAM12 was measured at 11-13 weeks in cases of trisomy 21 (n = 49), trisomy 18 (n = 28), trisomy 13 (n = 20), Turner syndrome (n = 29), triploidy (n = 10), and euploid pregnancies (n = 272). The levels of ADAM12, expressed as multiples of median (MoM), were compared in cases and controls and were assessed for association with free beta-human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein A (PAPP-A).

RESULTS

The median ADAM12 value in trisomy 21 (0.961 MoM) was not significantly different from the euploid fetuses (1.013 MoM), but in trisomy 18 (0.697 MoM), trisomy 13 (0.577 MoM), triploidy (0.426 MoM), and Turner syndrome (0.747 MoM), the levels were significantly lower. In both the euploid and aneuploid pregnancies, there was a significant association between ADAM12 and free beta-hCG and PAPP-A.

CONCLUSION

Maternal serum ADAM12 concentration at 11-13 weeks of gestation is unlikely to be useful in first-trimester screening for chromosomal abnormalities because in trisomy 21 the levels are not significantly different from normal, and in the other chromosomal defects, there is a significant association between ADAM12 and the traditional biochemical markers of free beta-hCG and PAPP-A.

Role of uterine artery Doppler in interpreting low PAPP-A values in first-trimester screening for Down syndrome in pregnancies at high risk of impaired placentation

OBJECTIVES

Low maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) are associated with both increased risk of aneuploidies and impaired trophoblastic invasion, while high uterine artery (UtA) resistance is associated with impaired trophoblastic invasion but not with an increased risk of aneuploidies. The aim of this study was to determine whether high UtA resistance plays a role in explaining low PAPP-A levels in the absence of aneuploidies.

METHODS

This was a prospective study of 116 singleton pregnancies at high risk for impaired placentation (having at least one major risk factor: prior history of pre-eclampsia, pregestational diabetes mellitus, chronic hypertension, chronic kidney disease, body mass index >30, autoimmune disorder, thrombophilia or recurrent pregnancy loss), booked for routine assessment of risk for aneuploidies by means of the first-trimester combined screening test (nuchal translucency thickness (NT) + PAPP-A + beta-human chorionic gonadotropin (beta-hCG)). Measurement of NT and the mean UtA pulsatility index (PI) were carried out at the 11 to 13 + 6-week scan. All values were calculated in multiples of the median (MoM) adjusted for gestational age. A cut-off risk of 1/270 at time of sampling was adopted to differentiate high- from low-risk groups for trisomy 21.

RESULTS

There were 108 patients deemed to be at low risk for trisomy 21 and eight at high risk. None had chromosomal defects, giving a false-positive rate for trisomy 21 of 6.9%. The greatest differences between patients at low risk and those at high risk for trisomy 21 were found in their PAPP-A (0.98 vs. 0.38 MoM, P < 0.01) and beta-hCG (1.09 vs. 1.77 MoM, P = 0.04) values. Greater NT thickness (1.02 vs. 0.90 MoM) and higher mean UtA-PI (1.05 vs. 0.96 MoM) were recorded in the high-risk group, although the differences did not reach statistical significance (P = 0.19 and 0.40, respectively). After log-transformation there were no significant correlations between mean UtA-PI and NT and between mean UtA-PI and beta-hCG. There was a significant negative linear correlation between mean UtA-PI and PAPP-A (r = -0.331; P < 0.01). After adjusting the PAPP-A values by UtA-PI, the false-positive rate for trisomy 21 decreased to 2.6%.

CONCLUSION

Mean UtA-PI at the 11 to 13 + 6-week scan may be an effect-modifier variable for PAPP-A that should be taken into account in the first-trimester combined screening for aneuploidies, at least in pregnancies at high risk for impaired placentation.

Second trimester maternal serum ADAM12 levels in Down's syndrome pregnancies

OBJECTIVE

To estimate the utility of maternal serum ADAM12 as a Down's syndrome marker.

METHODS

Samples from 71 Down's syndrome affected pregnancies were retrieved from - 20 degrees C storage together with 710 controls matched for gestation and storage time. ADAM12 was measured prior to identification of the affected pregnancies, and expressed in multiples of the gestation-specific median (MoM).

RESULTS

The median ADAM12 level in the affected pregnancies was 1.36 MoM with a 10th-90th centile range of 0.90-1.94 MoM compared with 1.01 and 0.65-1.52 MoM in the unaffected control pregnancies (P = < 0.0001, two-side Wilcoxon Rank Sum Test). The Mahalanobis distance between the medians was 0.96 compared with 0.92, 1.18, 1.07 and 1.24 for alpha-fetoprotein, intact human chorionic gonadotrophin (hCG), unconjugated estriol and inhibin-A respectively in the same samples. In unaffected pregnancies there were highly statistically significant correlations between ADAM12 and each of the other markers; in the affected pregnancies the only significant correlations were with hCG (P< or =0.0001) and inhibin-A (P< or =0.05). Statistical modelling predicted that ADAM12 as a fifth marker could increase the detection rate by 2-3% or reduce the false-positive rate by 0.9-1.7%.

CONCLUSIONS

ADAM12 is a second trimester marker of Down's syndrome, with discriminatory power similar to existing markers. It could be considered in multi-marker combinations.

First-trimester maternal serum a disintegrin and metalloprotease 12 (ADAM12) and adverse pregnancy outcome

OBJECTIVE

To examine the possible association of maternal serum a disintegrin and metalloprotease (ADAM12) in the first trimester of pregnancy and subsequent development of preeclampsia, delivery of small for gestational age (SGA) neonates, and spontaneous preterm delivery.

METHODS

The maternal serum concentration of ADAM12 at 11 0/7 to 13 6/7 weeks was measured in 128 cases of preeclampsia, 88 cases of gestational hypertension, 296 cases with SGA neonates, 58 cases of spontaneous preterm delivery, and 570 controls. Regression analysis was used to determine which of the maternal factors and fetal crown rump length were significant predictors of ADAM12 in the control group, and from the regression model the value in each case and control was expressed as a multiple of median (MoM). The levels of ADAM12 MoM were compared in cases and controls.

RESULTS

In the control group the concentration of ADAM12 increased with fetal crown rump length, decreased with maternal weight and was higher in African-American than in white women. There was a significant association between ADAM12 and pregnancy-associated plasma protein A (r=0.417, P<.001) and between each metabolite and birth weight percentile (r=0.176, P<.001 and r=0.109, P=.009). In the SGA group, the median ADAM12 concentration (0.848 MoM) was lower (P<.001), but in pregnancies complicated by preeclampsia (0.954 MoM), gestational hypertension (1.013 MoM), and spontaneous preterm delivery (1.048 MoM) the levels were not significantly different from controls (1.011 MoM).

CONCLUSION

There is a good correlation between the maternal serum ADAM12 and pregnancy-associated plasma protein A concentration. Measurement of ADAM12 does not provide useful prediction of SGA, preeclampsia, or spontaneous preterm delivery.

LEVEL OF EVIDENCE

II.

The metalloproteinase ADAM-12 regulates bronchial epithelial cell proliferation and apoptosis

OBJECTIVES

The ADAMs (a disintegrin and metalloproteinase) enzymes compose a family of membrane-bound proteins characterized by their multi-domain structure and ADAM-12 expression is elevated in human non-small cell lung cancers. The aim of this study was to investigate the roles played by ADAM-12 in critical steps of bronchial cell transformation during carcinogenesis.

MATERIALS AND METHODS

To assess the role of ADAM-12 in tumorigenicity, BEAS-2B cells were transfected with a plasmid encoding human full-length ADAM-12 cDNA, and then the effects of ADAM-12 overexpression on cell behaviour were explored. Treatment of clones with heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) neutralizing antibodies as well as an EGFR inhibitor allowed the dissection of mechanisms regulating cell proliferation and apoptosis.

RESULTS

Overexpression of ADAM-12 in BEAS-2B cells promoted cell proliferation. ADAM-12 overexpressing clones produced higher quantities of HB-EGF in their culture medium which may rely on membrane-bound HB-EGF shedding by ADAM-12. Targeting HB-EGF activity with a neutralizing antibody abrogated enhanced cell proliferation in the ADAM-12 overexpressing clones. In sharp contrast, targeting of amphiregulin, EGF or transforming growth factor-alpha failed to influence cell proliferation; moreover, ADAM-12 transfectants were resistant to etoposide-induced apoptosis and the use of a neutralizing antibody against HB-EGF activity restored rates of apoptosis to be similar to controls.

CONCLUSIONS

ADAM-12 contributes to enhancing HB-EGF shedding from plasma membranes leading to increased cell proliferation and reduced apoptosis in this bronchial epithelial cell line.

Maternal serum ADAM12s in the late first trimester of pregnancies with Trisomy 21

BACKGROUND

ADAM12s is a placenta-derived glycoprotein that is involved in growth and differentiation, and has been shown to be a potential first-trimester and second-trimester marker of Trisomy 21 and other aneuploides. Maternal ADAM12s concentrations show a considerable temporal variation with gestational age and here we study the levels at 11-13 weeks of gestation to establish the effectiveness or otherwise at a time when other established markers are used.

MATERIALS AND METHODS

Samples collected as part of routine first-trimester screening were retrieved from storage. In total, 46 samples from pregnancies with Trisomy 21 were identified and collected between 11 and 13 weeks of gestation-of these 83% had been identified by combined first-trimester screening. A series of 414 gestational age-matched samples collected during the same period formed the control group. ADAM12s was measured by a new DELFIA assay incorporating two monoclonals (6E6 and 8F8). Results were expressed as weight-corrected multiples of the median (MoM).

RESULTS

The median MoM ADAM12s rose from 0.914 at 11 weeks to 1.032 at 13 weeks.

CONCLUSIONS

Combining the data from this study and other published studies suggests that ADAM12s is unlikely to be of much additional value when screening for Trisomy 21 in the period 11-13 weeks. More studies are required looking at the potential of ADAM12s prior to 10 weeks.

First-trimester ADAM12s as early markers of trisomy 21: a promise still unfulfilled?

BACKGROUND

Here we study the levels of ADAM12s prior to and after 10 weeks of gestation to establish further the effectiveness or otherwise of ADAM12s as an early screening marker.

MATERIALS AND METHODS

Samples collected as part of routine first-trimester screening were retrieved from storage at - 80 degrees C. In total, 55 samples from pregnancies with trisomy 21 were identified, 31 collected between the 6th and 9th weeks of gestation and 24 collected after the 10th week. A series of 567 gestational age-matched samples collected during the same period formed the control group.

RESULTS

The median, multiples of the median (MoM) ADAM12s, at a median gestation of 10.0 weeks was 0.66, which was significantly lower than in the controls (p = < 0.001) when compared by Mann-Whitney test. The median MoM in those cases (n = 31) collected prior to 10 weeks was 0.618 MoM at a median gestation of 9.1 weeks. In those collected prior to 9 weeks (n = 14) the median was 0.596 at a median gestation of 8.6 weeks.

CONCLUSIONS

The data from this study does not support data from a previous study showing ultra-low levels of ADAM12s in pregnancies affected by trisomy 21 prior to 10 weeks of gestation.

Cellular roles of ADAM12 in health and disease

ADAM12 belongs to the large family of ADAMs (a disintegrin and metalloproteases) and possesses extracellular metalloprotease and cell-binding functions, as well as intracellular signaling capacities. Interest in ADAM12 has increased recently because its expression is related to tumor progression and it is a potential biomarker for breast cancer. It is therefore important to understand ADAM12's functions. Many cellular roles for ADAM12 have been suggested. It is an active metalloprotease, and has been implicated in insulin-like growth factor (IGF) receptor signaling, through cleavage of IGF-binding proteins, and in epidermal growth factor receptor (EGFR) pathways, via ectodomain shedding of membrane-tethered EGFR ligands. These proteolytic events may regulate diverse cellular responses, such as altered cell differentiation, proliferation, migration, and invasion. ADAM12 may also regulate cell-cell and cell-extracellular matrix contacts through interactions with cell surface receptors - integrins and syndecans - potentially influencing the actin cytoskeleton. Moreover, ADAM12 interacts with several cytoplasmic signaling and adaptor molecules through its intracellular domain, thereby directly transmitting signals to or from the cell interior. These ADAM12-mediated cellular effects appear to be critical events in both biological and pathological processes. This review presents current knowledge on ADAM12 functions gained from in vitro and in vivo observations, describes ADAM12's role in both normal physiology and pathology, particularly in cancer, and discusses important areas for future investigation.

First-trimester ADAM12 and PAPP-A as markers for intrauterine fetal growth restriction through their roles in the insulin-like growth factor system

BACKGROUND

PAPP-A is a marker used as part of the most effective method of screening for chromosomal anomalies in the first trimester. ADAM12 is a recently discovered pregnancy associated member of the ADAM (a multidomain glycoprotein metalloprotease) family. Recently, ADAM12 has been shown as a potential marker for early screening for chromosomal anomalies. Both PAPP-A and ADAM12 have been identified as proteases to insulin-like growth factor binding proteins. In this role, they may have a regulatory function in controlling the amount of free bioactive insulin-like growth factor (IGF). We therefore wish to examine if the levels of either of these proteases are related to various growth related adverse pregnancy outcomes.

MATERIALS AND METHODS

PAPP-A and ADAM12 were measured in a subset of samples collected at 11 to 14 weeks as part of an OSCAR clinic screening for chromosomal anomalies. Follow-up of pregnancies screened between September 1999 and August 2003 identified 1705 pregnancies with an outcome of intrauterine fetal demise on or after 24 weeks, preterm delivery at 24-34 weeks or 35-36 weeks, very low birthweight (<1.5 kg), low birthweight (<2.5 kg), large birthweight (>4.5 kg), and birth weight below the 3rd or 5th or 10th centile for gestation. A series of 414 normal outcome pregnancies constituted the control group. Marker levels were adjusted for gestation and maternal weight and the log MoM of the markers were compared using t-test of unequal variance between the control group and the various adverse outcome groups.

RESULTS

ADAM12 and PAPP-A concentrations were reduced in low for gestational age birth weights and in all births with weights below 2.5 kg. There was a linear relationship between the severity of the IUGR and the decrease in PAPP-A and ADAM12. In the larger babies, only ADAM12 was found to be significantly increased in babies above the 90th centile of weight for gestation.

CONCLUSIONS

The results of our study are compatible with the proposed role of ADAM12 and PAPP-A in promoting growth and development by breaking down IGF binding proteins and causing the release of free IGF for uptake into cells to promote growth. In those cases that eventually result in poor fetal growth, levels of PAPP-A and ADAM12 at 11-14 weeks are significantly lower than normal-in this instance, lowered PAPP-A and ADAM12 would result in less free IGF being available for cell uptake and growth stimulation. Further studies may elucidate if screening using such modalities can lead to new potential treatments for poorly growing fetuses.

Aneuploidy screening in the first trimester

This article reviews the performance of first trimester screening for chromosomal anomalies using various combinations of ultrasound and maternal serum biochemical modalities. Detection rates in excess of 90% can be routinely achieved for Trisomy 21, Trisomy 13, Trisomy 18 using a combination of fetal nuchal translucency (NT) thickness and maternal serum free ss-hCG and PAPP-A at 11 + 0 to 13 + 6 weeks of gestation.

ADAM 12 as a second-trimester maternal serum marker in screening for Down syndrome

BACKGROUND

ADAM 12 is a placenta-derived glycoprotein that is involved in growth and differentiation. The maternal serum concentration of ADAM 12 is a potential first-trimester maternal serum marker of Down syndrome (DS). Here we examine the potential of ADAM 12 as a second-trimester maternal serum marker of DS.

MATERIALS AND METHODS

The concentration of ADAM 12 was determined in gestational week 14-19 in 88 DS pregnancies and 341 matched control pregnancies. Medians of normal pregnancies were established by polynomial regression and the distribution of log(10) MoM ADAM 12 values in DS pregnancies and controls determined. Correlations with alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (free beta-hCG) were established and used to model the performance of maternal serum screening with ADAM 12 in combination with other second-trimester serum markers.

RESULTS

The ADAM 12 maternal serum concentration was significantly increased with a median MoM of 1.85 and a mean log(10) MoM (SD) of 0.268 (0.2678) compared to a mean log(10) MoM (SD) of 0.013 (0.4318) in controls. ADAM 12 correlated with maternal weight and ethnicity (with the serum concentration increased in Afro-Caribbeans), but neither with maternal age nor gestational age, and only marginally with AFP (r(DS) = 0.078, r(controls) = 0.093) and free beta-hCG (r(DS) = 0.073, r(controls) = 0.144. The increase in detection rate-for a false positive rate of 5%--by adding ADAM 12 to the double test (AFP + free beta-hCG) was 4%, similar to that of adding uE3 to the double test.

CONCLUSION

ADAM 12 is an efficient second-trimester marker for DS. Further studies should be conducted to determine whether it may be a useful additional or alternative marker to those currently used in the second-trimester.