Serum chromogranin A in the control of patients on long-term treatment with inhibitors of acid secretion

Correlation between clinicopathological characteristics and the clinical prognosis of patients with gastroenteropancreatic neuroendocrine tumors

Gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) are one of the most common types of NETs, accounting for 65-75% of all NETs. However, epidemiological characteristics of patients with GEP-NETs in China are still lacking. The present retrospective study aimed to investigate the local epidemiology of GEP-NETs and assess the prognostic factors in China. The data of 267 patients with GEP-NETs who were admitted to the First Affiliated Hospital of Bengbu Medical College (Bengbu, China) and the Affiliated Hospital of West Anhui Health Vocational College (Lu'an, China) were retrospectively reviewed. The clinical and pathological characteristics of the patients, as well as follow-up information, were collected, and the 5-year survival rate was calculated. Kaplan-Meier curves and log-rank analysis were used to analyze the prognostic factors. The stomach (100/267; 37.5%) was the most common site of GEP-NETs and the liver (25/39; 64.1%) was the most common metastatic site. A total of 166 (62.2%) and 219 (82.0%) patients had positive results for chromogranin A (CgA) and synaptophysin (Syn), respectively. The percentage of patients with tumor grade G1, G2 and G3 was 33.3, 21.0 and 45.7%, respectively. The 5-year overall survival rate was 79.7%, and the age, tumor site, distant metastasis and tumor grading upon diagnosis were all prognostic factors. In conclusion, the present case series investigated the epidemiology and prognostic factors of GEP-NETs in China. CgA and Syn could be used as diagnostic markers for NETs and the stomach was the most common primary tumor site. Lymph node metastasis, tumor site, distant metastasis and tumor grading were important prognostic factors.

Biochemical Assessment of Pheochromocytoma and Paraganglioma

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances.

Circulating Neuroendocrine Tumor Biomarkers: Past, Present and Future

Neuroendocrine tumors are a heterogeneous group of neoplasms originating from the diffuse endocrine system. Depending on primary location and hormonal status, they range in terms of clinical presentation, prognosis and treatment. Functional tumors often develop symptoms indicating an excess of hormones produced by the neoplasm (exempli gratia insulinoma, glucagonoma and VIPoma) and can be diagnosed using monoanalytes. For non-functional tumors (inactive or producing insignificant amounts of hormones), universal biomarkers have not been established. The matter remains an important unmet need in the field of neuroendocrine tumors. Substances researched over the years, such as chromogranin A and neuron-specific enolase, lack the desired sensitivity and specificity. In recent years, the potential use of Circulating Tumor Cells or multianalytes such as a circulating microRNA and NETest have been widely discussed. They offer superior diagnostic parameters in comparison to traditional biomarkers and depict disease status in a more comprehensive way. Despite a lot of promise, no international standards have yet been developed regarding their routine use and clinical application. In this literature review, we describe the analytes used over the years and cover novel biomarkers that could find a use in the future. We discuss their pros and cons while showcasing recent advances in the field of neuroendocrine tumor biomarkers.

Proton pump inhibitors and rebound acid hypersecretion

Rebound acid hypersecretion is defined as an increase in gastric acid secretion above pre-treatment levels after cessation of antisecretory therapy. Proton pump inhibitors (PPIs) have been proved to be more effective than histamine-2 receptor antagonists in suppressing intragastric acidity and have therefore become the main choice for management of acid-related complaints. Recent studies have shown that PPI therapy-elicited rebound acid hypersecretion could in turn induce acid-related symptoms. This makes it difficult for patients to cease PPI therapy. Hypergastrinemia is an important mechanism that leads to rebound acid hypersecretion. To reduce the occurrence of rebound acid hypersecretion, efforts should be made to restrict indications for using PPIs.

Dyspeptic symptom development after discontinuation of a proton pump inhibitor: a double-blind placebo-controlled trial

OBJECTIVES

Conflicting data exist on whether discontinuation of proton pump inhibitors (PPIs) is associated with rebound secretion of gastric acid.

METHODS

A total of 48 healthy Helicobacter pylori-negative volunteers (24 females) were randomized in a double-blinded manner to treatment with either pantoprazole 40 mg or placebo once daily for 28 days. Dyspeptic symptoms were registered daily using the Glasgow dyspepsia score (GDS) 2 weeks before, during, and 6 weeks after treatment. Plasma levels of gastrin and serum levels of chromogranin-A levels were measured before, during, and after treatment.

RESULTS

During the 2 weeks before treatment, the placebo group had a mean GDS of 0.20 + or - 0.7 compared with the pantoprazole group score of 0.54 + or - 1.3 (NS). No significant differences between the symptom severity scores of the two groups were shown during the treatment period. During the first week after discontinuation of treatment, the pantoprazole group had a mean symptom score of 5.7 + or - 11.7 vs. 0.74 + or - 2.6 in the placebo group (P<0.01). A total of 11 out of 25 (44%) subjects in the pantoprazole group developed dyspepsia compared with 2 out of 23 (9%) in the placebo group (P<0.01). During the second week of follow-up, the pantoprazole group had a mean symptom score of 1.6 + or - 3.4 compared with 0 + or - 0 in the placebo group (P<0.05). There were no significant differences in the mean symptom score for the pantoprazole group (1.1 + or - 0.6) compared with the placebo group (0.4 + or - 0.3) during the third week of follow-up. Symptom scores during the first week after treatment correlated with basal (P<0.01) and meal-stimulated (P<0.01) gastrin levels at the end of treatment.

CONCLUSIONS

A 4-week course of pantoprazole seems to induce dyspeptic symptoms in previously asymptomatic healthy H. pylori-negative subjects. The correlation between symptom score and gastrin levels suggests that these symptoms are due to acid rebound hypersecretion and seem to be related to the degree of acid inhibition.

Expression of neuroendocrine markers in non-small cell lung cancer

Neuroendocrine (NE) differentiation is reported in some cases of non-small cell lung cancer (NSCLC). The aim of this study was to evaluate the expression of NE markers in NSCLC using novel sensitive methods. 20 cases of NSCLC were examined using immunohistochemical (IHC) and immunoelectron microscopy (IEM) methods. In addition, circulating levels of the NE markers chromogranin A (CgA) and neuron-specific enolase (NSE) were measured. Using conventional IHC methods, two tumours (10%) showed immunoreactivity for synaptophysin (SYN), one (5%) for Cg and four (20%) for neural cell adhesion molecule (NCAM). Adding the tyramide signal amplification (TSA) technique, the number of immunoreactive tumours for both SYN and CgA increased to five (25%). No increased immunoreactivity was achieved for NCAM. Nine tumours (45%) were immunoreactive for SYN, CgA or NCAM. Using IEM, one of five representative samples that revealed IHC reactivity for CgA showed immunogold labelling of CgA in cytoplasmic vesicles. Elevated levels of circulating CgA or NSE did not correlate with positive IHC findings. In conclusion, using sensitive IHC methods NE differentiation was seen in a greater proportion of NSCLC than previously reported. Sensitive methods may improve our understanding of the tumour biology and represent an important diagnostic tool for future therapeutic modalities.

Rebound acid hypersecretion after long-term inhibition of gastric acid secretion

BACKGROUND

Rebound acid hypersecretion develops after the use of acid inhibitors.

AIM

To estimate the duration of hypersecretion and to elucidate the role of the enterochromaffin-like (ECL) cell in rebound acid hypersecretion.

METHODS

Patients waiting for anti-reflux surgery who had used a proton pump inhibitor daily > 1 year were included. All patients discontinued taking acid inhibiting drugs after the operation. Basal and pentagastrin stimulated acid output was measured at 4, 8, 16 and 26 weeks postoperatively. Oxyntic mucosal biopsies were collected before and 26 weeks after the operation for counting of histidine decarboxylase (HDC) immunoreactive cells. Serum chromogranin A (CgA) and gastrin were measured before and at 4, 8, 16 and 26 weeks after the operation.

RESULTS

Pentagastrin stimulated acid secretion was higher at 4 and 8 weeks than at 26 weeks after the operation. Gastrin and CgA were significantly reduced at 4 and 8 weeks, respectively. The number of HDC immunoreactive cells was reduced by 60% at 26 weeks postoperative.

DISCUSSION

Rebound acid hypersecretion lasts more than 8 weeks, but less than 26 weeks after long-term proton pump inhibition.

CONCLUSION

The findings indicate that not only the parietal cell mass, but also ECL cell mass and activity are involved in the mechanism of acid hypersecretion.

Gastric secretion

Overlapping neural, hormonal, and paracrine pathways finely regulate gastric acid secretion. In rats and guinea pigs, most of the intrinsic neural innervation to the gastric mucosa originates in the myenteric plexus. In contrast, human stomachs have a clearly defined submucosal plexus that contains a variety of transmitters including nitric oxide, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), substance P, and calcitonin gene-related peptide (CGRP). Although GRP is known to participate in meal-stimulated acid secretion by releasing gastrin in a variety of laboratory animals, recent studies were unable to demonstrate a role for endogenous GRP in meal-stimulated gastrin secretion in humans. Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin-glucagon-VIP family, has been localized to gastric mucosal neurons and may participate in vagally mediated acid secretion. Two novel peptides, ghrelin and leptin, have been localized to the stomach. Peripheral administration of ghrelin stimulates and of leptin inhibits acid secretion. The binding of secretagogues to parietal cells generates changes in second messengers that regulate the translocation and activation of the proton pump, HK-ATPase. In resting cells, HK-ATPase is contained within cytoplasmic tubulovesicles in an inactive form. At stimulation, the tubulovesicles fuse with the apical canaliculi and the HK-ATPase is incorporated into the apical membrane where it actively pumps H ions in exchange for K. Acute infection with Helicobacter pylori results in hypochlorhydria, whereas chronic infection can cause either hypo- or hyperchlorhydria, depending on the distribution of the infection and the degree of corpus gastritis. Recent studies suggest that inflammatory cytokines, produced in response to the organism, can play a role in the perturbations in acid and gastrin secretion induced by H. pylori.

Long-term safety of proton pump inhibitors: risks of gastric neoplasia and infections

After Helicobacter pylori eradication was introduced and largely eliminated the need for maintenance therapy for peptic ulcer disease, gastroesophageal reflux disease (GERD) became the main indication for prolonged gastric acid inhibition. The drug effect on GERD depends on the degree of acid inhibition, thus the efficacious proton pump inhibitors are preferred. The proton pump inhibitors have few immediate side effects, the main concern being the profound hypoacidity and hypergastrinaemia they induce. In short-term, hypergastrinaemia causes rebound hyperacidity, possibly worsening GERD and reducing the efficacy of histamine H(2) blockers. In the long-term, hypergastrinaemia causes enterochromaffin-like cell hyperplasia and carcinoids. Since enterochromaffin-like cells may be important in gastric carcinogenesis, iatrogenic hypergastrinaemia may predispose to carcinoma. Gastric hypoacidity also increases gut bacterial infections, and the barrier function of acid against viral and prion infections requires further assessment.