Beukenlaan 137
5616 VD Eindhoven
The Netherlands
+31 85064 55 82
info@clinlabint.com
PanGlobal Media is not responsible for any error or omission that might occur in the electronic display of product or company data.
Featured Articles
Chromogranin A as a biomarker for the detection of neuroendocrine tumours
Neuroendocrine tumours (NETs) are a heterogeneous group of tumours that vary depending on their anatomical sites, functionality and hormones produced. They are often silent clinically, and diagnosis is usually delayed. Chromogranin A (CgA) is the best-known general biomarker which is used for the diagnosis and management of NETs. It can be measured in serum or plasma using different analytical methods that include RIA, IRMA or ELISA. Raised circulating CgA is considered to be a relatively sensitive marker for the diagnosis of NET. As the test is rather non-specific, the diagnostic yield can be improved if other non-NET related conditions with raised CgA including renal failure, cardiac, hepatic and inflammatory diseases and use of proton pump inhibitor (PPI) are excluded.
by Dr Elham AlRisi and Prof. Waad-Allah S. Mula-Abed
Introduction
Neuroendocrine tumours (NETs) are a group of tumours that are usually derived from the cells of the nervous and endocrine systems. The tumours are characterized by being rare, heterogeneous and may affect different tissues and organs with neuroendocrine elements including the gastroenteropancreatic system, lungs, thyroid, parathyroid, pituitary, sympathoadrenals, and other tissues [1]. The NETs are distinctive in that their structural components of cells have the ability to synthesize, store, and secret bioactive amines and peptide hormones, a phenomenon termed ‘amine precursor uptake and decarboxylation’ (APUD) [2]. Although NETs may be considered rare, there is, however, increasing interest in their diagnosis, reported incidence and increased survival duration over time, suggesting that NETs are more prevalent than were previously reported.
The US Surveillance, Epidemiology, and End Results (SEER) Program registries in their search from 1973 to 2004, identified 35 618 patients with NETs with a significant increase in the reported annual age-adjusted incidence of NETs from 1973 (1.09/100 000) to 2004 (5.25/100 000). Using the SEER registry data, the estimated 29-year limited-duration prevalence of NETs in January 2004, was found to be 9263 and the estimated 29-year limited-duration prevalence in the United States on that date was 103 312 cases (35/100 000) [3]. The clinical presentations in patients with NETs vary according to the site where the tumour develops, which can be anywhere in the body and can range from a silent tumour, to one that is associated with an overproduction of the hormone/peptide (with their pathophysiological and clinical sequels) known to be produced by that tissue, or to a metastatic tumour. The growing interest in NETs in recent years is attributed to the increasing medical awareness, availability of laboratory markers for the detection of NETs particularly the chromogranins and the wide use of radiological imaging that have increased the diagnostic yields of these tumours.
Physiology of the granin family including chromogranin A
The secretory granules of the neuroendocrine and endocrine cells contain a family of highly acidic proteins, the granins. The most abundant forms of granins are chromogranin A (CgA), chromogranin B (CgB), secretogranin II (SgII), whereas granins the other forms that include SgIII, VGF, 7B2, and proSAAS are much less distributed in these granules. The granins are involved in the granulogenesis of the secretory granule biogenesis, with some being processed to form numerous peptides that have different physiological activities. CgA, the most studied chromogranin, was first isolated from the chromaffin cells of the adrenal medulla. It is a single polypeptide chain of 439 amino acids and 10 dibasic cleavage sites; the CgA gene is localized on chromosome 14q32 [4, 5].
Chromogranins contribute intracellularly to the overall vesicle biogenesis and facilitate the processing and regulation of other secretory proteins. Processing of chromogranins gives rise to multiple bioactive peptides that include the vasodilator vasostatin (human CgA 1–76), catecholamine release inhibitor catestatin (human CgA 352–372) and dysglycemic peptide pancreastatin (human CgA 250–301) [6]. Pancreastatin regulates glucose metabolism in cells and certain organs by inhibiting glucose-mediated insulin release from pancreatic islet cells, and inhibiting glucose uptake by adipocytes and hepatocytes. Other contributing functions of CgA include its involvement in regulating endothelial barrier, tumour angiogenesis, anti-apoptosis, and vascular structure and permeability [7].
Laboratory methods for the measurement of chromogranin A
There are different approaches for the determination of circulating CgA. The currently available methods include radioimmunoassay (RIA), immunoradiometric assay (IRMA) and enzyme-linked immunosorbent assay (ELISA). The introduction of commercially available ELISA kits for CgA assay (with their advantages of having long shelf life, technical ease, safety of use, and reported reasonable validity) has greatly improved the measurement of CgA in the diagnosis and clinical management of patients with of NETS. Currently there is increasing availability of these kits for measuring CgA in many hospital laboratories.
CgA can be measured using plasma or serum specimens. Although plasma CgA has been reported in a few studies to be higher than in serum, the difference may not affect clinical interpretation, particularly if there is consistent use of a single specimen type [6]. Different results might be reported by the different techniques, which might affect the validity indicators using these techniques. There are no universal standards for the techniques used and no universally accepted technique. There are reports that favour RIA over other methods; however, the practical advantages of ELISA techniques, especially the long shelf life, might make them attractive methods for use by many laboratories and might explain their widespread use in today’s practice [8]. Nevertheless, the selection of the analytical method to be used depends on the technical feasibility and convenience in the laboratory.
Chromogranin A and neuroendocrine tumours
CgA and its fragments are usually present in the circulation in equimolar concentration with the secretory activity of the secreting neuroendocrine tissue of both normal subjects and patients with different NETs; hence, CgA concentration in the circulation can be measured to provide information on the diagnosis, prognosis and monitoring of patients with these tumours, if other non-NET related physiological, pathological and pharmacological causes are excluded.
CgA is usually secreted by a variety of NETs, which include: carcinoids, pheochromocytoma, paraganglioma, medullary carcinoma of thyroid, parathyroid adenomas, pulmonary NETs including small cell lung cancer, gastroenteropancreatic (GEP-NETs) including functioning and nonfunctioning pancreatic islet cell tumours, some pituitary adenomas and other APUD tumours. The highest CgA values are observed in small intestine NETs and GEP-NETs associated with MEN1. Moderate-to-high CgA values are noted in pancreatic NETs, Zollinger-Ellison syndrome and gastrinomas. CgA is more frequently elevated in well-differentiated tumours compared to poorly differentiated NETs [9]. Different clinical validity indicators for CgA have been reported by different workers in the different patient cohorts. Yang et al. through their search of 13 studies that included 1260 patients with NETs and 967 healthy controls, reported an overall sensitivity, specificity and diagnostic odds ratio (DOR) of 0.73, 0.95 and 56.3, respectively, while the summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 14.56 and 0.26, respectively [10]. In addition, the area under the curve (AUC) of the circulating CgA in the diagnosis of NETs was 0.896. The pooled sensitivity and specificity values of CgA were 0.73 and 0.95, respectively, whereas the pooled PLR and NLR values were 14.56 and 0.26, respectively for the diagnosis of NETs. All these data suggested a higher diagnostic accuracy of CgA for the diagnosis of NETs. Among the included studies, three different assays were used to measure the circulating CgA, the sensitivity was both 0.74 by ELISA and RIA assays, and 0.69 by IRMA assay. The specificity was 0.93, 0.95 and 1.00 for ELISA, RIA and IRMA assays, respectively.
CgA values also have a prognostic role, as their high levels correlate with poor prognosis and short survival in certain NETS [11]. This relationship is usually limited in patients with gastrinomas, who have high CgA values despite the small primary tumour size and absence of metastases, possibly due to CgA secretion from G cells. Also, CgA values reflect the tumour burden, and monitoring the disease by CgA usually helps in detecting tumour recurrence or progression following treatment by surgery or radiotherapy. In patients with midgut NET, serum CgA level was the first marker to reflect tumour recurrence compared with urinary 5HIAA and radiological measurements [12]. Also, in pheochromocytoma, especially when large and lacking the proper hormonal characterization, CgA may be the only laboratory guide in the diagnosis and management of patients with such tumours [13].
Pitfalls in the interpretation of chromogranin A values
Although CgA is a useful general marker for the diagnosis and management of NETs, its universal secretion by almost all neuroendocrine cells makes its use confounded by its co-elevation in a variety of non-NET conditions including non-NET malignancies [14–16]. Hence, interpretation of CgA results must be done in the context of the overall confounding factors, whether physiological, pharmacological or pathological. Such conditions include the use of proton pump inhibitors (PPIs) or H2-receptor blockers, chronic atrophic gastritis, impaired renal function, cardiac failure, hepatic insufficiency, inflammatory bowel disease, benign prostatic hypertrophy or malignancy, rheumatoid arthritis, untreated essential hypertension, and some non-NET neoplasms. The pattern of elevation in serum CgA in certain non-NET conditions has been suggested recently to be utilized as a biomarker and prognostic marker in the stratification of some chronic diseases. This is particularly the case for heart failure where CgA might have a role in identifying those at higher risk of short- or long-term mortality [17]. The role of CgA in diabetes is not clear. However, CgA and its cleavage fragments, including WE-14, might play a part in the pathogenesis of type 1 diabetes mellitus, possibly as a T-cell autoantigen in pancreatic β-cell destruction [18]. Therefore, CgA might have a potential use as a biomarker in the future [18].
Conclusion
Chromogranin A is a secretory protein of neuroendocrine origin that is usually present with its fragments in the circulation as a result of the secretory activity of the secreting neuroendocrine cells of both normal subjects and patients with different NETs. It is the best-known general biomarker which is increasingly used for the diagnosis and management of NETs. It can be measured in plasma or serum using different analytical methods that include RIA, IRMA or ELISA. Raised circulating CgA is considered to be a relatively sensitive marker for the diagnosis of NET particularly if there is clinical suspicion and other work-up investigations that are in plan. Its measurement is also of value in monitoring the progress of treatment and prognosis of the disease. The diagnostic yield is improved if other non-NET related diseases or conditions are considered and excluded prior to the interpretation of CgA values. These conditions include the use of PPIs or H2-receptor blockers, chronic atrophic gastritis, impaired renal, cardiac, or hepatic insufficiency, inflammatory bowel disease, rheumatoid arthritis, and some non-NET neoplasms.
References
1. Kaltsas GA, Besser GM, Grossman AB. The diagnosis and medical management of advanced neuroendocrine tumors. Endocr Rev. 2004; 25(3): 458–511.
2. Pearse AG. Common cytochemical and ultrastructural characteristics of cells producing polypeptide hormones (the APUD series) and their relevance to thyroid and ultimobranchial C cells and calcitonin. Proc R Soc Lond B Biol Sci. 1968; 170(1018): 71–80.
3. Yao JC, Hassan M, Phan A, Dagohoy C, Leary C, Mares JE, Abdalla EK, Fleming JB, Vauthey JN, Rashid A, Evans DB. One hundred years after “carcinoid”: epidemiology of and prognostic factors for neuroendocrine tumors in 35,825 cases in the United States. J Clin Oncol. 2008; 26(18): 3063–3072.
4. Banks P, Helle K. The release of protein from the stimulated adrenal medulla. Biochem J 1965; 97(3): 40C–41C.
5. Bartolomucci A, Possenti R, Mahata SK, Fischer-Colbrie R, Loh YP, Salton SR. The extended granin family: structure, function, and biomedical implications. Endocr Rev. 2011; 32(6): 755–797.
6. Bech PR, Martin NM, Ramachandran R, Bloom SR. The biochemical utility of chromogranin A, chromogranin B and cocaine- and amphetamine-regulated transcript for neuroendocrine neoplasia. Ann Clin Biochem. 2014; 51(1): 8–21.
7. Taupenot L, Harper KL, O’Connor DT. The chromogranin-secretogranin family. N Engl J Med. 2003; 348(12): 1134–1149.
8. Stridsberg M, Eriksson B, Oberg K, Janson ET. A comparison between three commercial kits for chromogranin a measurements. J Endocrinol. 2003; 177(2): 337–341.
9. Modlin IM, Gustafsson BI, Moss SF, Pavel M, Tsolakis AV, Kidd M. Chromogranin A- biological function and clinical utility in neuro endocrine tumor disease. Ann Surg Oncol. 2010; 17(9): 2427–2443.
10. Yang X, Yang Y, Li Z, Cheng C, Yang T, Wang C, Liu L, Liu S. Diagnostic value of circulating chromogranin a for neuroendocrine tumors: a systematic review and meta-analysis. PLoS One 2015; 10(4): e0124884.
11. Ekeblad S, Skogseid B, Dunder K, Oberg K, Eriksson B. Prognostic factors and survival in 324 patients with pancreatic endocrine tumours treated at a single institution. Clin Cancer Res. 2008; 14(23): 7789–7803.
12. Welin S, Strisberg M, Cunningham J, Granberg D, Skogseid B, Oberg K, Eriksson B, Janson ET. Elevated plasma chromogranin A is the first indication of recurrence in radically operated midgut carcinoid tumors. Neuroendocrinology 2009; 89(3): 302–307.
13. Mula-Abed WA, Ahmed R, Ramadhan FA, Al-Kindi MK, Al-Busaidi NB, Al-Muslahi HN, Al-Lamki MA. A rare case of adrenal pheochromocytoma with unusual clinical and biochemical presentation: A case report and literature review. Oman Med J. 2015; 30(5): 382–390.
14. Gut P, Czarnywojtek A, Fischbach J, Bączyk M, Ziemnicka K, Wrotkowska E, Gryczyńska M, Ruchała M. Chromogranin A – unspecific neuroendocrine marker. Clinical utility and potential diagnostic pitfalls. Arch Med Sci. 2016; 12(1): 1–9.
15. Glinicki P, Jeske W. Chromogranin A (CgA) – the influence of various factors in vivo and in vitro, and existing disorders on its concentration in blood. Endokrynol Pol. 2011; 62(Suppl 1): 25–28 (in Polish).
16. Capellino S, Lowin T, Angele P, Falk W, Grifka J, Straub RH. Increased chromogranin A levels indicate sympathetic hyperactivity in patients with rheumatoid arthritis and systemic lupus erythematosus. J Rheumatol. 2008; 35(1): 91–99.
17. Goetze JP, Hilsted LM, Rehfeld JF, Alehagen U. Plasma chromogranin A is a marker of death in elderly patients presenting with symptoms of heart failure. Endocr Connect. 2014; 3(1): 47–56.
18. Stadinski BD, Delong T, Reisdorph N, Reisdorph R, Powell RL, Armstrong M, Piganelli JD, Barbour G, Bradley B, Crawford F, Marrack P, Mahata SK, Kappler JW, Haskins K. Chromogranin A is an autoantigen in type 1 diabetes. Nat Immunol. 2010; 11(3): 225–231.
The authors
Elham AlRisi MD; Waad-Allah S. Mula-Abed* MBChB MSc FRCPath
Directorate of Laboratory Medicine and Pathology, Royal Hospital, Muscat, Oman
*Corresponding author
E-mail: drsharef@live.com
MTHFR, hyperhomocysteinemia, CAD and T2DM
Individuals with type 2 diabetes mellitus (T2DM) are at increased risk of coronary artery disease (CAD). The C677T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene is associated with elevated plasma levels of homocysteine. The association of the MTHFR gene and the level of homocysteine with development of CAD has been studied in various population groups, including patients with T2DM, but the results have been variable. In practice, plasma homocysteine may be ordered as part of a screen for people with CAD or stroke, or who are at high risk for CAD or stroke but no other known risk factors. Testing of C677T polymorphism with or without elevated homocysteine is not recommended and has no clinical utility.
by Prof. Bakri Saeed and Dr Nisreen Mohammed
Type 2 diabetes mellitus and coronary artery disease
Type 2 diabetes mellitus (T2DM) is a major health problem throughout the world. It is a polygenic and multifactorial disease that is a major risk factor for cardiovascular disease. Cardiovascular disease (CVD) comprises coronary artery disease (CAD), also referred to as coronary heart disease (CHD), or ischemic heart disease (IHD), and cerebrovascular disease.
CAD due to atherosclerosis is a cause of significant morbidity and mortality, and is the leading cause of death worldwide. There are several risk factors for CAD. The well-stablished risk factors for CAD include diabetes mellitus, hypertension, smoking and dyslipidemia. There is growing interest in emerging risk factors for improved understanding of the mechanisms that underline cardiovascular disorders and CAD.
T2DM increases the risk for CAD by 2–4-fold compared to people without diabetes. CVD accounts for about 70% of deaths in people with diabetes. Identification and management of risk factors for CAD is an important aspect of management of diabetes mellitus.
Hyperhomocysteinemia and MTHFR polymorphism
Homocysteine is a sulfur-containing amino acid formed from demethylation of methionine. Methionine is the precursor to S-adenosyl methionine (SAMe) and is one of the essential amino acids. SAMe is a major methyl donor and is involved in numerous biological reactions. Homocysteine is metabolized by either remethylation to methionine or transsulfuration to cystathionine. The former reaction is catalysed by the vitamin B12-dependent methionine synthase. The latter reaction is catalysed by the enzyme cystathionine beta-synthase, which requires vitamin B6.
The methyl donor in the remethylation of homocysteine to methionine is 5-methyltetrahydrofolate. The 5,10-methylene-tetrahydrofolate reductase (MTHFR) enzyme catalyses the reduction of 5,10-methylene-tetrahydrofolate to 5-methyltetrahydrofolate. The enzyme requires B2 (riboflavin) as a cofactor (Fig. 1).
Therefore, hyperhomocysteinemia can result from reduced activity of the enzymes involved in homocysteine metabolism or from deficiency of the vitamins which are needed as cofactors in homocysteine metabolic reactions: folate, vitamin B6 and vitamin B12.
Several mutations in the MTHFR gene have been identified and some of them affect the activity of the enzyme. The commonest MTHFR gene mutation is a cytosine-to-thymidine substitution at nucleotide 677 (C677T), which changes alanine into valine, resulting in a thermolabile enzyme with impaired enzymatic activity and leading to hyperhomocysteinemia.
There are two copies of each gene. Therefore, an individual can be homozygous for the mutated gene or can be heterozygous, having one copy of the C677T variant and one normal copy. The C677T homozygous variant enzyme is thermolabile and demonstrates 70% reduced enzyme activity in vitro. The heterozygous C677T MTHFR enzyme has 35% reduced activity in vitro.
Worldwide, the frequency of MTHFR gene mutations varies among racial and ethnic groups, in Africa MTHFR gene polymorphism is markedly low (below 10%) for the C677T allele. In the European and Asian population, estimates of 18.6% and 20.8% were reported [1].
Association with CAD
In recent years hyperhomocysteinemia has been implicated as a risk factor for CAD, independent of other known risk factors. The primary mechanism by which homocysteine promotes atherosclerosis is by impairing endothelial function, which initiates the chain of events resulting in atherosclerotic plaque formation.
Numerous studies looked into the possible association between MTHFR genotypes and plasma homocysteine levels and the incidence of different MTHFR genotypes and hyperhomocysteinemia in CAD patients [2–5]. The results of these studies have been controversial. Several studies have shown the link between the MTHFR C677T gene polymorphism and the risk for CAD but many other studies failed to show association between MTHFR genotypes and plasma homocysteine levels and their role in CAD.
Previous studies in T2DM patients were also controversial. MTHFR polymorphism and hyperhomocysteinemia were shown to be predictors of cardiovascular events among diabetic patients [6, 7], whereas other studies failed to show a role for MTHFR polymorphic variants and homocysteine in increasing susceptibility to cardiovascular disease [8, 9].
Our study
We recently screened 226 consecutive patients with T2DM, <60 years of age, diagnosed according to WHO criteria. Of these, 113 had CAD confirmed by angiography and electrocardiography (ECG) and 113 had no evidence of CAD [10]. PCR and restriction fragment length polymorphism (RFLP) using Hinf1 restriction enzyme were used to determine MTHFR genotypes.
In our study, the T allele had a significant effect on homocysteine level (P value <0.05) and showed strong association with CAD among T2DM patients (odds ratio 6.2, P <0.0001).
Our study indicates that the C677T polymorphism of the MTHFR gene is associated with hyperhomocysteinemia, and the two are independently associated with the presence of CAD in patients with T2DM.
Reasons for controversy
The outcome of these numerous studies and meta-analysis remained contradictory. There was no agreement on the association between MTHFR genotypes and plasma homocysteine levels or the incidence of different MTHFR genotypes and hyperhomocysteinemia in CAD patients.
Plasma homocysteine levels are dependent on interacting nutritional and genetic factors. Some studies suggested that people homozygous for MTHFR C667T polymorphism tend to have hyperhomocysteinemia in the context of low folic acid levels. Supplementation with the vitamins involved in homocysteine metabolism was found to lower plasma homocysteine levels.
Therefore, geographic heterogeneity, nutritional and environmental factors could affect the relationship between MTHFR genotypes and CVD risk in different populations.
Practical points
Homocysteine may be ordered as part of a screen for people with or at high risk of CAD or stroke, especially if there is family history of CAD or stroke but no other known risk factors, such as diabetes, smoking, hypertension, or dyslipidemia. Routine screening of homocysteine, like that of cholesterol, has not been recommended.
Plasma homocysteine concentration may be elevated in B12 and folate deficiency and its measurement has been suggested to give an early indicator of deficiency.
In new-born testing, greatly increased concentrations of homocysteine in the urine and blood suggests a diagnosis of homocystinuria and indicates the need for confirmation of the cause of raised levels.
Most laboratories report normal homocysteine levels in the blood between 5 and 15 µmol/L. Any measurement above 15 µmol/L is considered high.
However, it should be noted that normal levels will vary between ethnic groups and populations. Homocysteine levels increase with age, are lower in pregnancy and are influenced by drugs. These factors should be taken into consideration when interpreting results.
Testing of C677T polymorphism with or without elevated homocysteine is not recommended in patients with CAD or other diseases where MTHFR variants have been implicated, such as thrombophilia or recurrent pregnancy loss.
References
1. Schneider JA, Rees DC, Liu YT, Clegg JB. Worldwide distribution of a common methylenetetrahydrofolate reductase mutation. Am J Hum Genet 1998; 62: 1258–1260.
2. Chehadeh SWEH, Jelinek HF, Al Mahmeed WA, Tay GK, Odama UO, Elghazali GE, et al. Relationship between MTHFR C677T and A1298C gene polymorphisms and complications of type 2 diabetes mellitus in an Emirati population. Meta gene 2016; 9: 70–75.
3. Bickel C, Schnabel R, Zengin E, Lubos E, Rupprecht H, Lackner K, et al. Homocysteine concentration in coronary artery disease: Influence of three common single nucleotide polymorphisms. Nutr Metab Cardiovascular Dis 2017; 27(2): 168–175.
4. Yilmaz H, Isbir S, Agachan B, Ergen A, Farsak B, Isbir T. C677T mutation of methylenetetrahydrofolate reductase gene and serum homocysteine levels in Turkish patients with coronary artery disease. Cell Biochem Funct 2006; 24(1): 87–90.
5. Meisel C, Cascorbi I, Gerloff T, Stangl V, Laule M, Müller JM, et al. Identification of six methylenetetrahydrofolate reductase (MTHFR) genotypes resulting from common polymorphisms: impact on plasma homocysteine levels and development of coronary artery disease. Atherosclerosis 2001; 154(3): 651–658.
6. Lewis SJ, Ebrahim S, Smith GD. Meta-analysis of MTHFR 677C→T polymorphism and coronary heart disease: does totality of evidence support causal role for homocysteine and preventive potential of folate? BMJ 2005; 331(7524): 1053–1058.
7. Bennouar N, Allami A, Azeddoug H, Bendris A, Laraqui A, El Jaffali A, et al. Thermolabile methylenetetrahydrofolate reductase C677T polymorphism and homocysteine are risk factors for coronary artery disease in Moroccan population. J Biomed Biotechnol 2007(1); 80687.
8. Bahadır A, Eroz R, Türker Y. Does the MTHFR C677T gene polymorphism indicate cardiovascular disease risk in type 2 diabetes mellitus patients? Anatolian J Cardiol 2015; 15(7): 524–530.
9. Rahimi Z, Nomani H, Mozafari H, Vaisi-Raygani A, Madani H, Malek-Khosravi S, et al. Factor V G1691A, prothrombin G20210A and methylenetetrahydrofolate reductase polymorphism C677T are not associated with coronary artery disease and type 2 diabetes mellitus in western Iran. Blood Coagul Fibrinolysis 2009; 20(4): 252–256.
10. Mohammed NO, Ali IA, Elamin BK and Saeed BO. The association of methylenetetrahydrofolate reductase gene polymorphism and hyperhomocysteinaemia with coronary artery disease in Sudanese patients with type 2 diabetes. Poster at Focus 2017, Association of Clinical Biochemistry annual meeting.
The authors
Bakri Osman Saeed*1 PhD, MD, FRCPath, FRCP; Nisreen Osman Mohamed2 PhD
1Faculty of Medicine, Sudan International University, Khartoum, Sudan
2Ahfad Centre for Science and Technology, Ahfad University for Women, Khartoum, Sudan
*Corresponding author
E-mail: saeedbakri@hotmail.com
Literarure Review: Brain Biomarkers
Prognostic value of molecular and imaging biomarkers in patients with supratentorial glioma
Lopci E, Riva M, Olivari L, Raneri F, Soffietti R, et al. Eur J Nucl Med Mol Imaging 2017; 44(7): 1155–1164
PURPOSE: We evaluated the relationship between 11C-methionine PET (11C-METH PET) findings and molecular biomarkers in patients with supratentorial glioma who underwent surgery.
METHODS: A consecutive series of 109 patients with pathologically proven glioma (64 men, 45 women; median age 43 years) referred to our Institution from March 2012 to January 2015 for tumour resection and who underwent preoperative 11C-METH PET were analysed. Semi-quantitative evaluation of the 11C-METH PET images included SUVmax, region of interest-to-normal brain SUV ratio (SUVratio) and metabolic tumour volume (MTV). Imaging findings were correlated with disease outcome in terms of progression-free survival (PFS), and compared with other clinical biological data, including IDH1 mutation status, 1p/19q codeletion and MGMT promoter methylation. The patients were monitored for a mean period of 16.7 months (median 13 months).
RESULTS: In all patients, the tumour was identified on 11C-METH PET. Significant differences in SUVmax, SUVratio and MTV were observed in relation to tumour grade (P<0.001). IDH1 mutation was found in 49 patients, 1p/19q codeletion in 58 patients and MGMT promoter methylation in 74 patients. SUVmax and SUVratio were significantly inversely correlated with the presence of IDH1 mutation (P<0.001). Using the 2016 WHO classification, SUVmax and SUVratio were significantly higher in patients with primary glioblastoma (IDH1-negative) than in those with other diffuse gliomas (P<0.001). Relapse or progression was documented in 48 patients (median PFS 8.7 months). Cox regression analysis showed that SUVmax and SUVratio, tumour grade, tumour type on 2016 WHO classification, IDH1 mutation status, 1p/19q codeletion and MGMT promoter methylation were significantly associated with PFS. None of these factors was found to be an independent prognostic factor in multivariate analysis.
CONCLUSION: 11C-METH PET parameters are significantly correlated with histological grade and IDH1 mutation status in patients with glioma. Grade, pathological classification, molecular biomarkers, SUVmax and SUVratio were prognostic factors for PFS in this cohort of patients. The trial was registered with ClinicalTrials.gov (registration: NCT02518061).
Expression of cell cycle regulators and biomarkers of proliferation and regrowth in human pituitary adenomas
Gruppetta M Formosa R, Falzon S, Ariff Scicluna S, Falzon E, et al. Pituitary 2017; 20(3): 358–371
PURPOSE: The pathogenesis of pituitary adenomas (PA) is complex. Ki-67, pituitary tumour transforming gene (PTTG), vascular endothelial growth factor (VEGF), cyclin D1, c-MYC and pituitary adenylate cyclase-activating peptide (PACAP) protein expression was analysed and correlated with tumour and patient characteristics.
METHODS: 74 pituitary tumour samples (48 non-functional PA, 26 functional PAs); immunohistochemical analysis of protein expression, retrospective analysis of MR images and in vitro analysis of octreotide treatment was carried out on GH3 cells.
RESULTS: PTTG expression was negatively associated with age and positively with PA size, regrowth and Ki-67 index. Cyclin D1 correlated with Ki-67 and tumour size. c-MYC negatively correlated with size of tumour and age, and correlated with PTTG expression. Somatostatin analogue treatment was associated with lower Ki-67, PTTG and cyclin D1 expression while T2 hypointense PAs were associated with lower PTTG, cyclin D1, c-MYC and Ki-67. In vitro analyses confirmed the effect of somatostatin analogue treatment on PTTG and cyclin D1 expression.
CONCLUSIONS: Interesting and novel observations on the differences in expression of tumour markers studied are reported. Correlation between Ki-67 expression, PTTG nuclear expression and recurrence/regrowth of PAs, emphasizes the role that Ki-67 and PTTG expression have as markers of increased proliferation. c-MYC and PTTG nuclear expression levels were correlated providing evidence that PTTG induces c-MYC expression in PAs and we propose that c-MYC might principally have a role in early pituitary tumorigenesis. Evidence is shown that the anti-proliferative effect of somatostatin analogue treatment in vivo occurs through regulation of the cell cycle.
Comparison of multiple tau PET measures as biomarkers in aging and Alzheimer’s Disease
Maass A, Landau S, Baker SL, Horng A, Lockhart SN, et al. Neuroimage 2017; 157: 448–463
The recent development of tau-specific positron emission tomography (PET) tracers enables in vivo quantification of regional tau pathology, one of the key lesions in Alzheimer’s disease (AD). Tau PET imaging may become a useful biomarker for clinical diagnosis and tracking of disease progression but there is no consensus yet on how tau PET signal is best quantified. The goal of the current study was to evaluate multiple whole-brain and region-specific approaches to detect clinically relevant tau PET signal. Two independent cohorts of cognitively normal adults and amyloid-positive (Aβ+) patients with mild cognitive impairment (MCI) or AD-dementia underwent [18F]AV-1451 PET. Methods for tau tracer quantification included: (i) in vivo Braak staging, (ii) regional uptake in Braak composite regions, (iii) several whole-brain measures of tracer uptake, (iv) regional uptake in AD-vulnerable voxels, and (v) uptake in a priori defined regions. Receiver operating curves characterized accuracy in distinguishing Aβ− controls from AD/MCI patients and yielded tau positivity cut-offs. Clinical relevance of tau PET measures was assessed by regressions against cognition and MR imaging measures. Key tracer uptake patterns were identified by a factor analysis and voxel-wise contrasts. Braak staging, global and region-specific tau measures yielded similar diagnostic accuracies, which differed between cohorts. While all tau measures were related to amyloid and global cognition, memory and hippocampal/entorhinal volume/thickness were associated with regional tracer retention in the medial temporal lobe. Key regions of tau accumulation included medial temporal and inferior/middle temporal regions, retrosplenial cortex, and banks of the superior temporal sulcus. Our data indicate that whole-brain tau PET measures might be adequate biomarkers to detect AD-related tau pathology. However, regional measures covering AD-vulnerable regions may increase sensitivity to early tau PET signal, atrophy and memory decline.
C-terminal fragments of the amyloid precursor protein in cerebrospinal fluid as potential biomarkers for Alzheimer disease
García-Ayllón MS, Lopez-Font I, Boix CP, Fortea J, Sánchez-Valle R, et al. Sci Rep. 2017; 7(1): 2477
This study assesses whether C-terminal fragments (CTF) of the amyloid precursor protein (APP) are present in cerebrospinal fluid (CSF) and their potential as biomarkers for Alzheimer’s disease (AD). Immunoprecipitation and simultaneous assay by Western blotting using multiplex fluorescence imaging with specific antibodies against particular domains served to characterize CTFs of APP in human CSF. We demonstrate that APP-CTFs are detectable in human CSF, being the most abundant a 25-kDa fragment, probably resulting from proteolytic processing by η-secretase. The level of the 25-kDa APP-CTF was evaluated in three independent CSF sample sets of patients and controls. The CSF level of this 25-kDa CTF is higher in subjects with autosomal dominant AD linked to PSEN1 mutations, in demented Down syndrome individuals and in sporadic AD subjects compared to age-matched controls. Our data suggest that APP-CTF could be a potential diagnostic biomarker for AD.
Blood-based biomarkers for the identification of sports-related concussion
Anto-Ocrah M, Jones CMC, Diacovo D, Bazarian JJ. Neurol Clin 2017; 35(3): 473–485
Sports-related concussions (SRCs) are common among athletes in the United States. Most athletes who sustain an SRC recover within 7 to 10 days; however, many athletes who sustain the injury do not recover as expected and experience prolonged, persistent symptoms. In this document, the authors provide an overview of the empirical evidence related to the use of blood-based brain biomarkers in the athlete population for diagnosis of SRCs, prognosis of recovery and return to play guidelines, and indications of neurodegeneration. The authors also provide a summary of research challenges, gaps in the literature, and future directions for research.
Brain biomarkers and pre-injury cognition are associated with long-term cognitive outcome in children with traumatic brain injury
Wilkinson AA, Dennis M, Simic N, Taylor MJ, Morgan BR, et al. BMC Pediatr 2017; 17(1): 173
BACKGROUND: Children with traumatic brain injury (TBI) are frequently at risk of long-term impairments of attention and executive functioning but these problems are difficult to predict. Although deficits have been reported to vary with injury severity, age at injury and sex, prognostication of outcome remains imperfect at a patient-specific level. The objective of this proof of principle study was to evaluate a variety of patient variables, along with six brain-specific and inflammatory serum protein biomarkers, as predictors of long-term cognitive outcome following pediatric TBI.
METHOD: Outcome was assessed in 23 patients via parent-rated questionnaires related to attention deficit hyperactivity disorder (ADHD) and executive functioning, using the Conners 3rd Edition Rating Scales (Conners-3) and Behaviour Rating Inventory of Executive Function (BRIEF) at a mean time since injury of 3.1 years. Partial least squares (PLS) analyses were performed to identify factors measured at the time of injury that were most closely associated with outcome on (1) the Conners-3 and (2) the Behavioural Regulation Index (BRI) and (3) Metacognition Index (MI) of the BRIEF.
RESULTS: Higher levels of neuron specific enolase (NSE) and lower levels of soluble neuron cell adhesion molecule (sNCAM) were associated with higher scores on the inattention, hyperactivity/impulsivity and executive functioning scales of the Conners-3, as well as working memory and initiate scales of the MI from the BRIEF. Higher levels of NSE only were associated with higher scores on the inhibit scale of the BRI.
CONCLUSIONS: NSE and sNCAM show promise as reliable, early predictors of long-term attention-related and executive functioning problems following pediatric TBI.
Biomarkers of stroke recovery: Consensus-based core recommendations from the Stroke Recovery and Rehabilitation Roundtable
Boyd LA, Hayward KS, Ward NS, Stinear CM, Rosso C, et al. Int J Stroke 2017; 12(5): 480-493
The most difficult clinical questions in stroke rehabilitation are “What is this patient’s potential for recovery?” and “What is the best rehabilitation strategy for this person, given her/his clinical profile?” Without answers to these questions, clinicians struggle to make decisions regarding the content and focus of therapy, and researchers design studies that inadvertently mix participants who have a high likelihood of responding with those who do not. Developing and implementing biomarkers that distinguish patient subgroups will help address these issues and unravel the factors important to the recovery process. The goal of the present paper is to provide a consensus statement regarding the current state of the evidence for stroke recovery biomarkers. Biomarkers of motor, somatosensory, cognitive and language domains across the recovery timeline post-stroke are considered; with focus on brain structure and function, and exclusion of blood markers and genetics. We provide evidence for biomarkers that are considered ready to be included in clinical trials, as well as others that are promising but not ready and so represent a developmental priority. We conclude with an example that illustrates the utility of biomarkers in recovery and rehabilitation research, demonstrating how the inclusion of a biomarker may enhance future clinical trials. In this way, we propose a way forward for when and where we can include biomarkers to advance the efficacy of the practice of, and research into, rehabilitation and recovery after stroke.
Brain biomarkers of vulnerability and progression to psychosis
Cannon TD. Schizophr Bull 2016; 42(Suppl 1): S127–132
Identifying predictors and elucidating the fundamental mechanisms underlying onset of psychosis are critical for the development of targeted pre-emptive interventions. This article presents a selective review of findings on risk prediction algorithms and potential mechanisms of onset in youth at clinical high-risk for psychosis, focusing principally on recent findings of the North American Prodrome Longitudinal Study (NAPLS). Multivariate models incorporating risk factors from clinical, demographic, neurocognitive, and psychosocial assessments achieve high levels of predictive accuracy when applied to individuals who meet criteria for a prodromal risk syndrome. An individualized risk calculator is available to scale the risk for newly ascertained cases, which could aid in clinical decision making. At risk individuals who convert to psychosis show elevated levels of proinflammatory cytokines, as well as disrupted resting state thalamo-cortical functional connectivity at baseline, compared with those who do not. Further, converters show a steeper rate of grey matter reduction, most prominent in prefrontal cortex, that in turn is predicted by higher levels of inflammatory markers at baseline. Microglia, resident immune cells in the brain, have recently been discovered to influence synaptic plasticity in health and impair plasticity in disease. Processes that modulate microglial activation may represent convergent mechanisms that influence brain dysconnectivity and risk for onset of psychosis and thus may be targetable in developing and testing preventive interventions.
