Demonstration of Chromogranin A in human neuroendocrine cell lines by immunohistology and immunoassay

Superficial primary small cell carcinoma of the esophagus: clinicopathological and immunohistochemical analysis of 15 cases

Primary esophageal small cell carcinoma (PESCC) is a relatively rare and aggressive tumor with poor prognosis. Systemic spreading and metastasis often occur at diagnosis. Although 5-year survival rate of superficial squamous cell carcinoma of the esophagus can be 86.1%, 5-year survival rate of superficial PESCC is still relatively low. This study mainly retrospectively analyzed clinicopathological and immunohistochemical features of 15 cases of superficial PESCC in our hospital from 1990 to 2004, in order to find suitable diagnostic markers and applicable therapies for this disease. The records mainly included presenting symptoms, demographics, diagnostic method, histopathology, follow-up, and therapy. Immunohistochemical staining of chromogranin A (CgA), neuron-specific enolase (NSE), synaptophysin (Syn), neuronal cell adhesion molecules (CD56), thyroid transcription factor-1 (TTF-1), cytokeration 34betaE12 (CK34betaE12), cytokeratin (AE1/AE3), and cytokeratin 10/13 was performed. Incidence of superficial PESCC accounted for 4.8% of that of superficial carcinoma of the esophagus during the same period. Initial symptoms of all patients were dysphagia or accompanied with retrosternal pain and upper abdominal pain, and duration of these symptoms was 75 days averagely. Mean age of patients was 58.8 years old, and the male-to-female ratio was 2.75 : 1. Lesions were mainly located at middle thoracic esophagus. One, 2, and 5-year survival rates were 66.7, 33.3, and 6.7%, respectively. The median survival time was 19 months and mean survival time was 23.7 months after diagnosis. The percentages of PESCC samples with positive immunoreactivity were NSE 100%, Syn 100%, AE1/AE3 100%, CD56 93.3%, TTF-1 60%, CgA 53.3%, CK34betaE12 6.7%, and cytokeratin 10/13 0%, respectively. Our study suggested that PESCC was a rare and aggressive tumor with high malignancy. Superficial PESCC had rapid progression and poor prognosis compared with superficial squamous cell carcinoma of the esophagus at the same stage. The systemic therapy based on combination of postoperative chemotherapy and radiotherapy might be an effective approach for the treatment of superficial PESCC as a systemic disease. Higher proportion of positive labeling of NSE, Syn, AE1/AE3, CD56, TTF-1, and CgA in PESCC was valuably applied in diagnosis and differential diagnosis.

A new human chromogranin 'A' immunoradiometric assay for the diagnosis of neuroendocrine tumours

We investigated whether plasma chromogranin A (CgA), measured by a new immunoradiometric assay, may be a sensitive and specific marker of phaeochromocytoma and of other neuroendocrine tumours. This study involved 121 patients of whom 20 with phaeochromocytoma, 28 with other neuroendocrine tumours (19 gastroenteropancreatic tumors, 3 medullary thyroid and 6 small cell lung carcinomas), 25 with solid nonfunctioning adrenocortical tumours and 48 with essential hypertension. In addition, 130 normal subjects were taken as controls. Plasma catecholamines were measured by using high-performance liquid chromatography, and CgA by a two-site sandwich immunoradiometric assay involving monoclonal antibodies raised against the unprocessed central domain (145-245) of human CgA. Plasma CgA in controls (49.0 +/- 3.1 ng ml(-1), mean +/- SE) and in essential hypertensives (50.8 +/- 3.5 ng ml(-1)) was lower (P< 0.0001) than in adrenocortical tumours (91.8 +/- 13.2 ng ml(-1)), in phaeochromocytomas (254 +/- 49 ng ml(-1)) and in patients with other neuroendocrine tumours (469 +/- 84 ng ml(-1)). Plasma CgA and catecholamines identified 13 and 18 out of 20 phaeochromocytomas with sensitivity of 65% and 90%, respectively. Combined measurement of both markers improved sensitivity up to 100%. In the other neuroendocrine tumours, CgA was abnormal in 23/28 cases (sensitivity 82%) and in 6 it was the only circulating marker of disease. In gastroenteropancreatic tumours, CgA measurement identified all cases (sensitivity 100%). Specificity of CgA in patients with essential hypertension was 98%. In conclusion, CgA determination showed high sensitivity in identifying gastroenteropancreatic tumours and, in association with catecholamines, in detecting patients with phaeochromocytoma. CgA sometimes appeared to be the only circulating marker of disease. Since the specificity of CgA proved to be excellent, this assay may be useful for diagnosis both of functioning and non-functioning neuroendocrine tumours.

Detection of chromogranin A in human gastric adenocarcinomas using a sensitive immunohistochemical technique

Neuroendocrine cells are often disclosed in human gastric adenocarcinomas and may be recognised by their immunoreactivity towards chromogranin A. However, in dedifferentiated neuroendocrine tumour cells, the chromogranin A content may be reduced making it difficult to detect with conventional immunohistochemical methods. We therefore used a sensitive signal amplification technique in order to evaluate chromogranin A immunoreactivity and thus neuroendocrine differentiation in 40 gastric adenocarcinomas. Neuroendocrine cells were visualised by means of a monoclonal chromogranin A antibody and the avidin-biotin peroxidase complex technique, without and with addition of tyramide signal amplification. Double immunohistochemistry towards chromogranin A and Ki-67 were used to disclose proliferation in the neoplastic cells. A marked increase in the number of carcinomas containing chromogranin A-immunoreactive neoplastic cells was noted when applying the tyramide signal amplification technique. In addition, the number of immunoreactive cells within each tumour increased, and in some cases almost all the neoplastic cells became immunoreactive. Chromogranin A-immunoreactive tumour cells showing signs of proliferation were found in the majority of these carcinomas. In conclusion, we have disclosed widespread immunoreactivity towards chromogranin A in a proportion of gastric adenocarcinomas when enhancing the signal with tyramide signal amplification. Neuroendocrine differentiation is thus a common finding in gastric carcinomas when using sensitive methods.

New molecular aspects in the diagnosis and therapy of neuroendocrine tumors of the gastroenteropancreatic system

The nature and biology of neuroendocrine cells and of tumors derived therefrom have been the subject of intense research using cell biological and molecular approaches. Diagnostic procedures for establishing the diagnosis of a neuroendocrine tumor have been improved through the development of new serological markers and imaging procedures. Histopathological diagnosis has been refined by the introduction of a broad spectrum of marker proteins for different subtypes of neuroendocrine neoplasms. The high receptor specificity of somatostatin analogues such as octreotide or lanreotide has made these drugs valuable tools in diagnosis and therapy, and some of the achievements made as well as future directions are reviewed in this article. Another substance in use for therapy of neuroendocrine tumors is interferon-a, whose signal transduction mechanism has been investigated considerably during the past several years. In addition to biotherapy with somatostatin analogues and/or interferon-a, chemotherapy is an accepted strategy in the treatment of advanced neuroendocrine tumor disease derived from the foregut. In this context, streptozotocin has caught some attention due to its somewhat selective toxicity against neuroendocrine tumor cells. Some recent studies on the role of the glucose transporter isoform GLUT2 may provide insight into streptozotocin's action. The multiple endocrine neoplasia type-1 gene has recently been cloned, sequenced and identified as a gene potentially involved in the development of the familial cancer syndrome of multiple endocrine neoplasia type 1 (MEN-1). Mutations of this putative tumor suppressor gene have been described, and the abundance of mutations in MEN-1-related tumors as well as sporadic neuroendocrine tumors at MEN-1 locations have been demonstrated. Whether determination of MEN-1 mutations will be valuable for clinical routine is under investigation.

Detection of chromogranin A mRNA in small cell lung carcinoma using a new, highly sensitive in situ hybridization method with a non-radioisotope oligonucleotide probe

BACKGROUND

Immunoreactivity for chromogranin A (Cg A) is associated with the presence of neurosecretory granules in tumor cells, but immunohistochemical staining for Cg A may be absent in small cell lung carcinoma (SCLC), which has only a few secretory granules. Localization of Cg A mRNA is a useful indicator of the site of synthesis of a particular protein and possibly the rate of synthesis, and it is not dependent on posttranslation events within the cells. However, it is difficult to detect the low levels of mRNA copies using the standard non-radioisotope (RI) oligonucleotide probe.

METHODS

The authors analyzed Cg A mRNA in 20 cases of SCLC in formalin fixed, paraffin embedded tissue using a new, highly sensitive in situ hybridization method that was developed from the maximized immunohistochemistry (ImmunoMax) method. They also investigated Cg A mRNA in nonsmall cell lung carcinoma (NSCLC), including ten cases each of adenocarcinoma and squamous cell carcinoma of the lung.

RESULTS

All examined SCLC tissues showed a positive reaction for Cg mRNA. No NSCLC specimens showed any positive reaction for Cg A mRNA.

CONCLUSIONS

The detection of Cg A mRNA using the new, highly sensitive in situ hybridization method with a non-RI oligonucleotide probe can be used to characterize neuroendocrine differentiation of lung tumors even when the Cg A protein is not detected by immunohistochemistry. The authors believe this is a first step toward better diagnosis and treatment for patients with SCLC.

Prognostic factors in resected non-small cell lung cancer: an immunohistochemical study of 39 cases

Non-small cell lung carcinoma (NSCLC) is a histologically heterogeneous collection of tumours with variable clinical behaviour. Performance status, tumour stage and histological type have important prognostic implications, but the clinical outcome in an individual patient remains unpredictable. In search of other prognostic factors we studied the expression of several immunohistochemical markers in NSCLC, resected with curative intent. Tumour samples of 19 patients with a postoperative disease-free survival of at least 5 years and those of 20 patients who died of tumour recurrence within 2 years after resection were selected for this study. The populations were matched for age, sex and tumour stage. We investigated the expression of markers for neuroendocrine differentiation, cell adhesion and cell cycle regulation in both populations. None of the investigated immunohistochemical markers distinguished between long- and short-term survivors of resected NSCLC. In stage 1 tumours expression of embryonal NCAM was observed more often in the short survival group (P = 0.026) and in stage 3a EGF-r expression was associated with the long survival group (P = 0.047). However, these findings remained to be confirmed. Expression of Rb, NCAM and embryonal NCAM was not detected in adenocarcinomas, whereas T-Ag and chromogranin A immunoreactivity was absent from squamous cell carcinomas.

Immunoassay and immunohistology studies of chromogranin A as a neuroendocrine marker in patients with carcinoma of the prostate

OBJECTIVES

Neuroendocrine differentiation in carcinoma of the prostate is characterized by the expression of neuroendocrine cell products such as chromogranin A (CgA). We studied serum levels and tissue staining for CgA in prostate cancer to assess their clinical value.

METHODS

In 82 patients with prostate cancer, serum specimens were obtained at diagnosis and studied by both CgA and prostate-specific antigen (PSA) immunoassays. In 43 additional patients with prostate cancer, paraffin-embedded tissue from core biopsies or transurethral resections and serum samples were studied, respectively, by immunohistology and immunoassay for CgA.

RESULTS

In serum samples from the 82 patients in whom CgA and PSA levels were measured, 26 of 82 (32%) had an elevated CgA (greater than 200 ng/mL), and 36 of 82 (44%) had an elevated PSA (greater than 4.0 ng/mL). Of the patients with Stage D2 cancer, 11 of 18 (61%) had an elevated CgA and 6 of 18 (33%) had an elevated PSA. Four of 5 patients with local recurrence had an elevated CgA, but only 1 patient had an elevated PSA. Of the 43 patients in whom serum and tissue CgA studies were performed, 12 (28%) had elevated serum CgA, and 15 of the 43 (35%) had CgA staining in their prostate tissue. Of the 14 of these patients with D2 disease (distant metastases), 9 (64%) had elevated serum levels of CgA and 6 (43%) had positive staining in their prostate tissue. Of the 9 patients with Stage D2 disease and elevated serum CgA, 6 had a normal serum PSA.

CONCLUSIONS

Our studies complement those of others and indicate that CgA has potential as a clinically useful serum and tumor marker for prostate cancer. Serum CgA measurements can identify some patients with advanced disease who do not have elevated serum PSA. However, further studies in larger groups of patients are needed to define the clinical value of CgA as a marker for prostate cancer.

Characterisation of circulating chromogranin A in human cancer patients

The structure of circulating chromogranin A (CgA) of phaeochromocytoma patients was characterised and compared with that of CgA extracted from tumours. Size exclusion chromatography experiments provided evidence that CgA is present in the blood of different patients, as well as in tumour extracts, as multiple forms having different hydrodynamic sizes of 600 kDa (CgA-I), 100 kDa (CgA-II) and 55 kDA (CgA-III). The amount of each CgA form as a proportion of the total antigenic material was different in different patients. Western blot analysis of chromatographic fractions indicated that these forms are made up by polypeptides of similar molecular weight (about 60-70 kDa). All CgA forms express the epitopes recognised by two monoclonal antibodies (A11 and B4E11), directed against residues 68-70 and 81-90 of human CgA. However, their relative immunoreactivity was markedly different. No evidence for the presence of multimeric complexes in the CgA-I fraction was obtained by various immunological and biochemical methods. These results suggest that circulating CgA in phaeochromocytoma patients consists of at least three forms that appear to be made up by polypeptides with similar molecular weight and different hydrodynamic properties and immunoreactivity. We hypothesise that different conformations and shapes contribute to the heterogeneity of circulating CgA.

Antigenic regions of human chromogranin A and their topographic relationships with structural/functional domains

Chromogranin A is a protein contained in the secretory granules of many neuroendocrine cells. The linear antigenic sites of human chromogranin A were studied by examining the cross-reaction of polyclonal and monoclonal anti-chromogranin A antibodies with native chromogranin A and with synthetic peptides encompassing most of the chromogranin A sequence. Chromogranin A residues 1-20, 47-67, 107-158, 254-297, 331-375, and 395-419 were found to be poorly or not antigenic, while residues 25-46, 163-210, 231-253, 298-314 and 68-106, 222-230, 315-330, 376-394 were found to contain weak and strong antigenic sites, respectively. Residues 68-70 (GAK) and 81-90 (GFEDELSEVL) were strongly recognized by two mouse mAbs (B4E11 and A11, respectively). Since mAb A11 has been previously used for immunohistochemical analysis of chromogranin-A-producing tissues from different species and for in vivo imaging of chromogranin-A-positive endocrine tumors, these results imply that at least part of the 81-90 region is surface-exposed in cryostat tissue sections as well as in vivo. The results may help in selecting new antibodies with improved affinity and immunogenicity for in vivo targeting of chromogranin-A-producing tumors.

Spectrum of neuroendocrine differentiation in lung cancer cell lines featured by cytomorphology, markers, and their corresponding tumors

Lung cancer cell lines which show features of neuroendocrine (NE) differentiation can be divided into 4 types which have distinct clinicopathologic correlates: classic small cell lung cancer (SCLC), variant SCLC, pulmonary carcinoid, and non-small cell lung cancer with NE features (NSCLC-NE). These cell lines form a spectrum regarding their degree of NE differentiation which ranges from high levels seen in carcinoid cell lines to very low which is typical of the variant SCLC. A careful comparison of the properties of tumors and their cell lines and correlating these data with the clinical history of the patient has markedly enhanced the relevance of cell lines as models for NE biology and lung carcinogenesis.

Immunohistochemical and immunoelectron microscopic demonstration of chromogranin A in formalin-fixed tissue of Merkel cell carcinoma

BACKGROUND

Chromogranin A (CGA) is the major protein of neurosecretory granules (NSG) of cells of the diffuse neuroendocrine system, and the amount of CGA corresponds to the number of NSGs.

OBJECTIVE

Because formalin fixation may destroy NSGs, a study was performed to examine the presence of CGA in Merkel cell carcinoma (MCC) to determine whether CGA depends on the presence of intact NSGs.

METHODS

Formalin-fixed, paraffin-embedded tissue of 15 MCCs was investigated by immunohistochemistry and immunoelectron microscopy for the presence of CGA and NSGs.

RESULTS

CGA was demonstrated in 12 of 15 MCCs by immunochemistry and in 6 of 10 MCCs by immunoelectron microscopy although intact NSGs could not be discerned in all cases.

CONCLUSION

CGA remains demonstrable even when no morphologically intact NSGs are present, which suggests that CGA is not exclusively responsible for the electron density of NSGs.

Tissue reactivity of anti-Leu19

Monoclonal antibody anti-Leu19, is a marker of natural killer cells. Since reactivity between anti-Leu7, another natural killer cell marker, and small cell neuroendocrine carcinomas has been described, we evaluated the reactivity of anti-Leu19 in 92 neuroendocrine tumours. Frozen sections in each case were immunostained using the avidin-biotin-peroxidase complex method with monoclonal anti-Leu19. We found Leu19 expression in 93% of the cases. We also evaluated 149 other tumours, including adenocarcinomas, undifferentiated large cell carcinomas, lymphomas, melanomas and soft tissue tumours. We found Leu19 expression in 36% (by liberal interpretative criteria), or 29% (by conservative interpretative criteria) of these cases. Thus, while anti-Leu19 appears to be a sensitive marker for neuroendocrine tumours, a lack of specificity limits its practical application in diagnostic histopathology.

A retrospective analysis of immunohistochemical staining in identification of poorly differentiated round cell and spindle cell tumors--results, reagents and costs

Immunohistochemistry has rapidly established a significant role in diagnostic pathology. We use immunohistochemistry as an adjunct to morphological diagnosis and employ a "panel approach" to the classification of poorly differentiated tumors. This retrospective analysis was conducted to examine the efficacy of such an approach, using, as an example, the two most common categories of poorly differentiated tumors, namely, the poorly differentiated round cell tumors and spindle cell tumors. Five hundred and fifty-seven consecutive cases of such tumors, collected over a two-yr period, had been subjected to immunohistochemical staining because specific or definitive categorization of the tumor was not possible on the basis of the examination of hematoxylin and eosin stained sections. The clinical history, gross and microscopic findings, as well as the results of immunohistochemical stains were analyzed. Immunohistochemistry allowed a definitive diagnosis to be assigned in 420 cases (75.4%). It was particularly useful in identifying malignant melanoma of both epithelioid and spindle types and distinguished between melanoma, lymphoma and poorly differentiated carcinoma in 126 cases of such lesions occurring in adult lymph nodes. It was also useful in identifying tumors in small biopsies where poor cytomorphological preservation or small size precluded accurate categorization. The application of appropriately chosen panels of antibodies tailored to a narrow list of differential diagnoses helped to identify myogenous, vascular, nerve sheath and fibrocystic lesions among the group of spindle cell tumors. Immunohistochemistry provided definitive diagnoses in 70% of round cell tumors and 92% of spindle cell tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone-related protein, chromogranin A, and calcitonin gene products in the neuroendocrine skin carcinoma cell lines MKL1 and MKL2

We studied the production of parathyroid-hormone-related protein, chromogranin A, calcitonin and calcitonin-gene-related peptide in the neuroendocrine skin cell line, MKL1, and a subsequently derived cell line designated MKL2. Both cell lines had cytological, histological and electron-microscopic features typical of neuroendocrine differentiation. Immunohistology and radioimmunoassay studies demonstrated the presence of parathyroid-hormone-related protein, chromogranin A, calcitonin-gene-related peptide, and calcitonin in the MKL2 cell line and the last three substances in both cell lines. The secretion of each of the first three substances was regulated by phorbol in the MKL2 cells. Additional immunohistochemical studies demonstrated the variable expression of bombesin, substance P, and vasoactive intestinal polypeptide in MKL2 cells, and the expression of synaptophysin in both MKL1 and MKL2 cells. These studies demonstrate the neuroendocrine characteristics of the MKL cell lines and provide a novel model for studies of the production and interactions of several neuroendocrine proteins and peptides by human skin cells.

Prognostic impact of histologic demonstration of chromogranin A and neuron specific enolase in pulmonary adenocarcinoma

One hundred-fourteen patients with inoperable adenocarcinoma of the lung (ACL) were evaluated by immunohistochemistry with monoclonal antibodies against Neuron Specific Enolase (NSE) and Chromogranin A (Chr A) in order to determine the frequency and prognostic impact of such antigen expression. All patients were previously untreated and received chemotherapy according to a prospective randomized trial. The tumors of 18 patients (16%) had more than 10% positive cells stained with anti-NSE, 59 (52%) had 1-10% positive cells and those of 37 patients (32%) contained no NSE-positive cells. The corresponding figures for Chr A were: 22 patients (19%), 51 patients (45%) and 41 patients (36%), respectively. Forty-four per cent of the patients with more than 10% positive NSE cells responded to chemotherapy (either complete or partial remissions) compared to 17% of the patients with fewer than 10% positive cells (p less than 0.025). The corresponding values for Chr A were 30% responders versus 19% responders (not statistically significant). The median survival for patients with more than 10%, 1-10% or no NSE-positive cells was 262 days, 231 days and 159 days, while, for Chr A it was 245 days, 200 days and 238 days, respectively. The survival curves for both NSE and Chr A according to the various levels of positivity were not significantly different. The presence of neuroendocrine marker in pulmonary adenocarcinoma seems to be associated with increased sensitivity to chemotherapy.

Expression of chromogranin A mRNA in small cell carcinoma of the lung

Chromogranin A (CgA) is the most specific neuroendocrine marker but in small cell carcinoma of the lung (SCCL) CgA immunoreactivity cannot always be detected, possibly owing to poor granularity. The localization of CgA mRNA could be a more useful indicator of CgA synthesis in SCCL. We have therefore studied the expression of CgA mRNA in SCCL, using in situ hybridization and Northern blot analysis, comparing it with CgA immunoreactivity. The expression of CgA mRNA and immunoreactivity in other types of lung tumours was also investigated. Freshly fixed, surgically resected SCCL (n = 5), adenocarcinoma (n = 10), squamous cell carcinoma (n = 10), large cell carcinoma (n = 5), and primary lymphoma (n = 2) were examined. Weak immunoreactivity to CgA was seen in one SCCL but all five strongly expressed CgA mRNA. The specificity of the in situ hybridization signal and the probe was confirmed by the use of a sense probe and Northern blot analysis. Non-SCCLs were negative for both CgA mRNA and immunoreactivity. This study provides evidence for CgA synthesis in SCCL and confirms the specificity of CgA for neuroendocrine differentiation. In situ hybridization appears to be a very useful tool for investigating the nature of tumour cells, especially in the absence of the end product of the gene transcript.

A chromogranin A-derived peptide differentially regulates the secretion of calcitonin gene products

We studied the regulation of the secretion of CT and CGRP by chromogranin A (CgA)-derived peptides in a human lung tumor cell line. The amino-terminal peptide of CgA, CgA1-40, stimulated the secretion of CGRP and inhibited the secretion of CT; both effects occurred in a dose-dependent manner. These studies demonstrate a differential effect of a CgA-derived peptide on two products of the CT gene, CT itself and CGRP. CgA may be processed at its multiple dibasic sites to peptides that specifically regulate the secretion of its coresident hormones, in this case two calcitonin gene products that are present in the same secretory vesicle. This novel mechanism represents a new pathway for the control of calcium regulating hormones.

Distinct patterns of chromogranin A-related species can be demonstrated in endocrine cells

We have studied the pattern of chromogranin A (CgA)-related species in different human endocrine cells that produce CgA and also express the calcitonin gene. Antibodies against CgA peptides that span its linear sequence were used in Western analysis of cell lines derived from medullary thyroid carcinoma (MTC), small cell lung cancers (SCLC), epidermoid cell lung cancer (ECLC) and a pulmonary carcinoid tumor (CRND). Each of the cell lines demonstrated a distinct pattern of CgA-related species. Gel filtration studies also revealed multiple and different forms of immunoreactive CgA in the cell lines. Although proteolysis may contribute to our results, these observations suggest that native CgA is processed to smaller species in a tissue-specific pattern by different endocrine cells. More conclusive studies, however, are necessary to establish that cell processing leads to the specific CgA moieties that we have observed.

A malignant mixed mesodermal tumor of the uterine corpus with hypercatecholaminemia

We report an unusual case of malignant mixed mesodermal tumor of the uterine corpus associated with various symptoms related to overproduction of catecholamine by the tumor cells. Histologically, the tumor was dominated by carcinomatous epithelium with foci of malignant mesenchyma. The type of epithelium was endometrioid with papillary adenocarcinomas containing foci of malignant squamous epithelium. The malignant mesenchyma consisted mainly of a fibrous stroma with many large and bizarre cells and spindle cells mimicking leiomyosarcoma, many of which were pleomorphic and contained large bizarre hyperchromatic nuclei. Foci of atypical adult-type cartilage and neoplastic osteoid formation were noted. In the tumor tissue, membrane-bound neurosecretory-type cytoplasmic granules were demonstrated by electron microscopy and polypeptide hormone synthesis was demonstrated by immunohistochemistry. Furthermore, the patient suffered frequent attacks of sudden hypertension with hypercatecholaminemia.

The effects of forskolin and calcium ionophore A23187 on secretion and cytoplasmic RNA levels of Chromogranin-A and calcitonin

We have studied the regulation of the secretion and cytoplasmic RNA levels of calcitonin (CT) and Chromogranin-A (CgA) to determine if the biosynthesis and secretion of these two substances are controlled in a coordinated fashion. The studies were conducted in two cell lines, a medullary thyroid carcinoma (MTC) cell line and a lung tumor (BEN) cell line. Both cell types secrete CT and CgA. Forskolin treatment resulted in a significant increase in the secretion of CT and CgA in each cell line and in CT-specific cytoplasmic RNA in the MTC cell line. Treatment with calcium ionophore A23187 resulted in significantly increased secretion of both substances in the lung tumor cells but not in the medullary thyroid carcinoma cells. A significant increase in CT-specific or CgA-specific cytoplasmic RNA was not seen in either cell line. We conclude that the secretion of CT and CgA are regulated in a coordinated fashion in these cell lines through processes that are calcium-mediated and processes that involve cyclic AMP-dependent protein kinase A. However, each of these regulatory pathways is not always operative in a given tissue. The coordinate regulation of the secretion of CT and CgA supports the hypothesis that CgA participates in the secretory process of its associated hormones.