Chromogranin a Measurement in Neuroendocrine Tumors

An Italian Program of External Quality Control for Chromogranin A (CgA) Assay: State of the Art of Cga Measurement

Chromogranin A (CgA) is a secretory protein produced by many neuroendocrine cells. Circulating levels of CgA have been found to be elevated in a variety of neuroendocrine tumors and may facilitate the diagnosis and management of patients with functioning as well as non-functioning forms. However, up to now the analytical methods used for assaying intact CgA and CgA-derived peptides in the circulation of patients have not been monitored in Italy by an external quality control program.

Within the framework of a Ministry of Health project an external quality control program was developed to investigate the state of the art of CgA determination in Italy and to monitor the performance of laboratories carrying out this assay. This paper deals primarily with the former of these aspects.

Every laboratory received the study protocol together with a questionnaire to be returned before receipt of the samples to be assayed. Serum and plasma samples obtained from a pool of routine specimens were prepared at three different concentrations of CgA, aliquoted, frozen at –80°C and mailed in dry ice to the participating laboratories. Of the 43 laboratories, 21 used IRMA, 21 used ELISA and one used RIA. There was a wide range in the time of kit utilization and the number of samples assayed per year, which indicated that the participating group was heterogeneous with regard to their experience in the determination of CgA. Most laboratories routinely used serum and plasma for IRMA and ELISA, respectively, and different data fitting approaches were employed. Further analyses will investigate the possible influence of these pre-analytical factors on laboratory performance.

Comparison between Two Methods in the Determination of Circulating Chromogranin A in Neuroendocrine Tumors (NETs): Results of a Prospective Multicenter Observational Study

Several methods for analyzing CgA using either monoclonal or polyclonal antibodies have been developed, which differ in their diagnostic performance. The present paper describes the results of a prospective multicenter study aimed at comparing the clinical value of the two most widely used commercially available CgA assay kits in patients affected by neuroendocrine tumors (NETs). Two hundred sixty-one patients from 40 different centers and 99 healthy subjects were evaluated. CgA levels were measured with two different methods, a two-step immunoradiometric assay (IRMA) and an enzyme-linked immunosorbent assay (ELISA). CgA was measured centrally by two reference laboratories, one of which used IRMA and the other ELISA, and it was measured by the participating institutions with the method routinely used by each of them. The major findings of the present study were: (i) the two assays for the determination of CgA present good diagnostic performance; (ii) both assays are robust and guarantee comparable results when applied in different settings (central vs local laboratory); (iii) the negative/positive cutoff points (87 ng/mL for IRMA and 21.3 U/L for ELISA) were established according to standardized criteria; (iv) the results obtained with the two assays in basal clinical samples of patients affected by NETs show an apparently satisfactory correlation (rs=0.843, p<0.0001). However, a possibly clinically meaningful 36% discordance rate was found. These findings support the hypothesis that the two CgA kits might provide partially different information.

Accuracy and Clinical Correlates of Two Different Methods for Chromogranin A Assay in Neuroendocrine Tumors

Measurement of chromogranin A (CgA) plays a major role in the management of neuroendocrine tumors (NET); however, reliable assaying of CgA is made difficult by the rapid hydrolysis following its release into the bloodstream. This study was aimed at the assessment of two assays for CgA in NET patients. CgA was measured in 93 patients by means of an enzyme-linked immunosorbent assay (ELISA) and an immunoradiometric assay (IRMA). The specificity and sensitivity of CgA were evaluated in relation to tumor histology. The clinical accuracy of the two assays was evaluated by receiver-operating characteristic (ROC) curve analysis. Regression analysis demonstrated different immunoreactivity for CgA of the antibodies used in the two kits (r=0.61). The two assays had different accuracy also in classifying patients according to their clinical condition (91% vs 64% specificity and 79% vs 79% sensitivity for the ELISA and IRMA assay, respectively) and tumor histology (81% vs 85% sensitivity for the ELISA and IRMA assays, respectively, in carcinoids; 92% vs 67% sensitivity for the ELISA and IRMA assays, respectively, in pancreatic islet cell tumors). The different clinical accuracy of the two assays was confirmed by the ROC analysis (AUC=0.90 vs AUC=0.87 for the ELISA and IRMA assays, respectively). In conclusion, because of the poor standardization of the commercially available measurement tools the clinical accuracy of CgA measurement depends on the assay used. This makes it difficult to compare CgA values measured with different kits and affects the clinical accuracy of the different assays for CgA.

Catestatin and vasostatin concentrations in healthy dogs

Background

The neuroendocrine glycoprotein chromogranin A is a useful biomarker in humans for neuroendocrine tumors and stress. Chromogranin A can be measured in both blood and saliva. The objective of this study was to investigate concentrations of and correlation between the chromogranin A epitopes catestatin and vasostatin in healthy dogs accustomed to the sample collection procedures. Blood and saliva samples were collected from 10 research Beagle dogs twice daily for 5 consecutive days, and from 33 privately-owned blood donor dogs in association with 50 different blood donation occasions. All dogs were familiar with sample collection procedures. During each sampling, stress behavior was scored by the same observer using a visual analog scale (VAS) and serum cortisol concentrations. Catestatin and vasostatin were analyzed using radioimmunoassays for dogs.

Results

The dogs showed minimal stress behavior during both saliva sampling and blood sampling as monitored by VAS scores and serum cortisol concentrations. Few and insufficient saliva volumes were obtained and therefore only catestatin could be analyzed. Catestatin concentrations differed significantly and did not correlate significantly with vasostatin concentrations (P < 0.0001). Age, gender, breed, and time of sample collection did not significantly affect concentrations of plasma catestatin, vasostatin, and saliva catestatin.

Conclusions

The normal ranges of plasma catestatin (0.53–0.98 nmol/l), vasostatin (0.11–1.30 nmol/l), and saliva catestatin (0.31–1.03 nmol/l) concentrations in healthy dogs accustomed to the sampling procedures were determined. Separate interpretation of the different chromogranin A epitopes from either saliva or plasma is recommended.

NANETS consensus guideline for the diagnosis and management of neuroendocrine tumors: well-differentiated neuroendocrine tumors of the thorax (includes lung and thymus)

Neuroendocrine tumors (NETs) of the thorax, including bronchial and thymic neuroendocrine NETs, are often referred to as NETs of the foregut. The incidence and prevalence of NETs are increasing in the United States as demonstrated in the Surveillance, Epidemiology, and End Results from 1973 to 2004 (J Clin Oncol. 2008;26[18]:3063-3072). Although the majority of bronchial and thymic NETs are sporadic, approximately 5% to 10% can be associated with hereditary syndrome, multiple endocrine neoplasms type 1 (Nat Rev Cancer. 2005;5[5]:367-375). Diagnosis is made by tissue pathology, allowing for characterization and classification of the NET. Radiologic evaluation is performed to determine the extent of disease involvement. Clinical symptoms from hormonal overproduction or from paraneoplastic processes are medically managed to improve patients' quality of life. Locoregional disease can be curative with surgery; however, distant or metastatic disease is rarely curable. Therapeutic options for metastatic/advanced NETs of the thorax are mainly to palliate symptoms. Final treatment recommendations for patients with either bronchial or thymic NETs should be individualized, weighing the risks and benefits of therapy.

Identification and quantification of glycoproteins using ion-pairing normal-phase liquid chromatography and mass spectrometry

Glycoprotein structure determination and quantification by MS requires efficient isolation of glycopeptides from a proteolytic digest of complex protein mixtures. Here we describe that the use of acids as ion-pairing reagents in normal-phase chromatography (IP-NPLC) considerably increases the hydrophobicity differences between non-glycopeptides and glycopeptides, thereby resulting in the reproducible isolation of N-linked high mannose type and sialylated glycopeptides from the tryptic digest of a ribonuclease B and fetuin mixture. The elution order of non-glycopeptides relative to glycopeptides in IP-NPLC is predictable by their hydrophobicity values calculated using the Wimley-White water/octanol hydrophobicity scale. O-linked glycopeptides can be efficiently isolated from fetuin tryptic digests using IP-NPLC when N-glycans are first removed with PNGase. IP-NPLC recovers close to 100% of bacterial N-linked glycopeptides modified with non-sialylated heptasaccharides from tryptic digests of periplasmic protein extracts from Campylobacter jejuni 11168 and its pglD mutant. Label-free nano-flow reversed-phase LC-MS is used for quantification of differentially expressed glycopeptides from the C. jejuni wild-type and pglD mutant followed by identification of these glycoproteins using multiple stage tandem MS. This method further confirms the acetyltransferase activity of PglD and demonstrates for the first time that heptasaccharides containing monoacetylated bacillosamine are transferred to proteins in both the wild-type and mutant strains. We believe that IP-NPLC will be a useful tool for quantitative glycoproteomics.

Comparison between two commercially available chromogranin A assays in detecting neuroendocrine differentiation in prostate cancer and benign prostate hyperplasia

BACKGROUND

Chromogranin A (CgA) is the neuroendocrine (NE) marker most frequently employed in detecting NE differentiation in prostate cancer patients, either at the tissue level or in the general circulation.

METHODS

We compared the two commercially CgA assay kits in detecting NE differentiation, in benign hyperplasia (BPH) or prostate cancer (PC) patients (pts). 170 pts with BPH, 107 with BPH+inflammation, and 136 PC pts entered the study. CgA was measured in each patient with the immunoradiometric assay (IRMA) and with the enzyme-linked immunoabsorbent assay (ELISA).

RESULTS

A moderate relationship was found between CgA measured with IRMA and ELISA in the whole population (Spearman's R=0.65, p<0.05), in BPH pts (R=0.76, p<0.05), in BPH+inflammation pts (R=0.53, p<0.05) and in PC pts (R=0.60, p<0.05). Twenty-two out of 62 pts (35.4%) with elevated ELISA CgA did not have increased IRMA CgA; by contrast, 21/61 pts (34.4%) with elevated IRMA CgA were not recognized as abnormal by the ELISA kit.

CONCLUSIONS

CgA measured by the two assays provided a significant discordance rate, suggesting that the two kits might elicit different information.

Neuroendocrine phenotype of non-small cell lung carcinoma: immunohistological evaluation and biochemical study

AIMS AND METHODS

The prevalence and distribution of neuroendocrine differentiation in non-small cell lung cancer (NSCLC) was estimated by assays for synaptophysin (SYN), chromogranin A (CgA), Leu7 and neuron-specific enolase (NSE). Serum NSE and CgA were determined in parallel to find the values of these markers for distinguishing neuroendocrine differentiation in NSCLC. Fifty-eight resected NSCLC specimens and 34 sera of NSCLC patients entered the study. Neuroendocrine differentiation was graded according to the percentage of neuroendocrine tumor cells as NE0--0%, NE1-NE4--1%->76%. Serum NSE <12.5 ng/mL and serum CgA <46 U/L were taken as cutoff levels.

RESULTS

63.8% (37/58) of NSCLC were scored as NE1-NE4 according to the SYN, CgA and Leu7 levels; 34.5% as NE1; 29.3% as NE2-NE4. 56.8% of tumors were positive for SYN, 34.4% for CgA, 22.4% for Leu7, and 79.3% for NSE. A significant relationship was found between tumor SYN and tumor CgA expression, and between tumor SYN expression and tumor stage. Adenocarcinomas showed a significantly higher rate of neuroendocrine differentiation than squamous cell carcinomas. All normal serum CgA levels corresponded to a lack of CgA expression in the tumors. The increased serum NSE levels presented by 26% of NSCLC patients (mainly <16 ng/mL) did not correlate with tumor NSE expression.

CONCLUSIONS

The prevalence of neuroendocrine differentiation in NSCLC varies and depends on the immunohistochemical criteria used; this warrants standardization of the immunohistochemical criteria for neuroendocrine differentiation in NSCLC. NSE expression in the tumor and a mild increase in serum NSE are poor markers for distinguishing neuroendocrine differentiation in NSCLC.

Hybridisation of [76Br]-labelled antisense oligonucleotides to Chromogranin A mRNA verified by RT-PCR

Methods have been developed to label oligonucleotides (ODNs) in the 5'-position with (76)Br via a prosthetic group on a hexylamino-linker. The purpose of the study was to explore whether the labelling procedure would prevent specific hybridisation by using reverse transcription-polymerase chain reaction (RT-PCR) followed by sequencing of the PCR product. Antisense ODNs (30 mer, specific for rat Chromogranin A [CgA] mRNA) with phosphodiester (O-ODN) or phosphothioate (S-ODN) backbone, either unlabelled or labelled with (76)Br, served as one of the primers in individual PCR reactions. Using O-ODN as a primer, irrespective of being labelled or not, a selected 225-bp PCR fragment was successfully amplified. However, no amplification was obtained using S-ODN as a primer. The proper PCR products were only detected in the sample prepared from the adrenal gland, but not in that from the heart, liver or kidney. Autoradiographic recording of the gel, after gel electrophoresis, revealed radioactive signals corresponding to the amplified PCR products. The sequence of the PCR product matched the rat CgA mRNA sequence obtained from the EMBL database. RT-PCR is an attractive method to identify the selective binding of modified ODNs to target mRNA. This method confirmed that the labelling with (76)Br did not change the hybridisation ability of antisense O-ODN.

Circulating levels of angiogenic cytokines can predict tumour progression and prognosis in neuroendocrine carcinomas

OBJECTIVE

The growth behaviour of well-differentiated neuroendocrine carcinomas of the gastro-entero-pancreatic system varies greatly and parameters predicting their prognosis are lacking. The aim of our study was to investigate whether tumour growth could be correlated with the release of proangiogenic factors into the circulation.

PATIENTS AND METHODS

Circulating vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), basic fibroblast growth factor (bFGF) and angiogenin were measured in 38 patients with advanced neuroendocrine carcinomas and compared to healthy age-matched controls. In 20 patients, angiogenic cytokine levels were measured at consecutive time points and correlated to tumour progression as assessed by abdominal CT scan, MRI and chromogranin A levels.

RESULTS

VEGF levels were elevated in patients compared to controls (P < 0.002) and clearly associated with tumour progression (P < 0.005). Angiogenin levels were significantly higher in patients than in controls (P < 0.003), while high IL-8 levels were predictive of shorter survival. Angiogenin and bFGF levels were correlated neither with tumour growth nor with patient survival.

CONCLUSIONS

VEGF and IL-8 are associated with tumour progression and might qualify as markers of prognosis and therapy control in patients with neuroendocrine carcinomas. Our results support the notion that specific anti-angiogenic therapies should be evaluated in neuroendocrine carcinoma patients.

Impact of chromogranin A measurement in the work-up of neuroendocrine tumors

Since the development of the first immunoassay for circulating chromogranin A in 1984, a lot of studies have evaluated its clinical impact in neuroendocrine tumors. Initially studied in pheochromocytoma patients, the clinical impact of chromogranin A has rapidly extended to most neuroendocrine tumours, sometimes in combination with other eutopic or ectopic secretions. In our experience, CgA demonstrates a variable sensitivity between NET primary and a high specificity. Our results suggest that CgA should be routinely screened in foregut-derived NET and abandoned in the routine screening of medullary thyroid carcinoma. In addition, in phaeochromocytoma and ileum-NET patients, CgA demonstrates a comparable sensitivity with urinary reference markers and its impact on the follow-up will form a key point when recommending routine screening. Both tumor burden and secretory activity should be taken into account when interpreting CgA results.

Clinical significance of blood chromogranin A measurement in neuroendocrine tumours

BACKGROUND

Tumour marker measurement gives clinicians useful information for the follow-up and management of patients with neuroendocrine tumours (NETs). The currently used tumour markers for NETs are neuron-specific enolase (NSE) and chromogranin A (CgA). The clinical accuracy of these biomarkers depends on histotype and disease extent. CgA is thought to be the optimal marker for most NETs, as it is independent of the biological characteristics of the tumour.

AIM OF THE STUDY

In this study we investigated the value of CgA assessment with respect to the other biomarkers in the diagnosis and follow-up of patients with different types of NETs. PATIENTS AIND METHODS: We measured CgA, NSE, carcinoembryonic antigen (CEA) and urine 5-hydroxy-3-indoleacetic acid (5-HIAA) in 290 patients with 127 gastroenteropancreatic (GEP) tumours, 49 neuroblastomas, 36 lung tumours, 24 medullary thyroid carcinomas (MTCs). 15 pNETs, 12 paragangliomas. 7 Merkel's cell carcinomas (MCCs) and 20 NETs of unknown origin. CgA and 5-HIAA were quantitated by immunoenzymatic assays, while NSE and CEA were determined by radioimmunoassays.

RESULTS

The biomarkers' specificity in GEP tumours was 86% for CgA, 100% for NSE, 91% for CEA and 100% for 5-HIAA. The corresponding sensitivity was 68% for CgA, 33% for NSE, 15.4% for CEA and 35% for 5-HIAA. The sensitivity of CgA largely depends on disease extent or presence of functioning tumours and is highest in metastatic and syndromic patients. CgA determination in GEP tumour monitoring is useful to evaluate the response to therapy and to follow up patients with liver metastases. In neuroblastomas the overall specificity of NSE and CgA was 50%, and 83%, respectively. In these tumours NSE sensitivity was close to 90% in all clinical stages, while the sensitivity of CgA depended on clinical stage (50% for stage I and II, 60% for stage III and 100% for stage IV tumours). Also in this type of tumour changes in CgA levels correlated with objective response. In paragangliomas CgA measurement may provide useful clinical information. Measurement of CgA is of use in the diagnosis of lung carcinoids, while its value in MTCs, pNETs and MCCs is very limited.

CONCLUSIONS

CgA was confirmed to be the best tumour marker currently available for identifying patients suffering from NETs of the GEP system, lung carcinoids and neuroblastomas. CgA evaluation is recommended in the follow-up of patients with such tumours.

Concurrent occurrence of gastric adenocarcinoma and duodenal neuroendocrine cell carcinoma: a composite tumour or collision tumours ?

BACKGROUND

Neuroendocrine cell (NEC) carcinoma is occasionally accompanied by adenocarcinoma but the relationship between these two morphologically distinct tumours is unclear. Two hypotheses have arisen regarding the mechanism for the association of adenocarcinoma and NEC carcinoma. One is that both are derived from a common multipotential epithelial stem cell. The second hypothesis is that adenocarcinoma and NEC carcinoma arise from a multipotential epithelial stem cell and a primitive NEC, respectively.

AIMS

To elucidate the relationship between the two histologically distinct tumours, adenocarcinoma of the stomach and NEC carcinoma of the duodenum.

PATIENT/METHODS

We present a case in which the tumour extended across the pyloric ring, the gastric portion of which revealed adenocarcinoma while the duodenal portion showed argyrophil NEC carcinoma. The two histologically distinct lesions of the tumour were examined by immunohistochemistry and genetic analysis of p53.

RESULTS

The gastric region was negative for chromogranin A staining but positive for carcinoembryonic antigen (CEA) staining. In contrast, the duodenal region was positive for chromogranin A but negative for CEA. All tumour regions showed a point mutation in p53 gene at exon 7 (GGC (glycine)-->GTC (valine) at codon 245). The distal portion of the duodenal tumour showed an additional point mutation in p53 gene at exon 5 (GCC (alanine)-->GTC (valine) at codon 129).

CONCLUSIONS

The two histologically distinct tumours, adenocarcinoma of the stomach and NEC carcinoma of the duodenum, appear to be derived from a common epithelial cell.