Ectopic ACTH production in carcinoma of the lung

A Case of Pancreatic Neuroendocrine Tumor with Liver Metastases Demonstrating the Possibility of Enhanced ACTH Production by the SACI Test

Objective

ACTH-producing pancreatic NETs have a propensity to metastasize, and in patients with metastases, there is no established method yet to precisely determine if the excess ACTH is produced by the primary or the metastatic tumors. Localizing the source of production of ACTH in such cases is important for devising suitable treatment strategies and evaluating the benefit of local therapies from the viewpoint of control of Cushing's syndrome.

Methods

We performed the selective arterial calcium injection (SACI) test combined with selective portal and hepatic venous sampling in a 32-year-old female patient with ectopic ACTH-producing pancreatic NET and liver metastases.

Results

The blood level of ACTH after Ca loading was significantly elevated only in the vessels thought to be directly feeding the pancreatic tumor, and Ca loading from any artery did not significantly increase ACTH concentrations in the hepatic veins compared to the main trunk of the portal vein.

Conclusions

The present case demonstrates that there might be an ACTH-producing p-NET that responds to Ca loading. Further in vitro studies are required to validate this possibility.

Na, K-ATPase α1 cooperates with its endogenous ligand to reprogram immune microenvironment of lung carcinoma and promotes immune escape

Dysregulated endocrine hormones (EHs) contribute to tumorigenesis, but how EHs affect the tumor immune microenvironment (TIM) and the immunotherapy of non-small cell lung cancer (NSCLC) is still unclear. Here, endogenous ouabain (EO), an adrenergic hormone, is elevated in patients with NSCLC and closely related to tumor pathological stage, metastasis, and survival. EO promotes the suppression of TIM in vivo by modulating the expression of immune checkpoint proteins, in which programmed cell death protein ligand 1 (PD-L1) plays a major role. EO increases PD-L1 transcription; however, the EO receptor Na- and K-dependent adenosine triphosphatase (Na, K-ATPase) α1 interacts with PD-L1 to trigger the endocytic degradation of PD-L1. This seemingly contradictory result led us to discover the mechanism whereby EO cooperates with Na, K-ATPase α1 to finely control PD-L1 expression and dampen tumoral immunity. In conclusion, the Na, K-ATPase α1/EO signaling facilitates immune escape in lung cancer, and manipulation of this signaling shows great promise in improving immunotherapy for lung adenocarcinoma.

Nivolumab-induced hypophysitis causing secondary adrenal insufficiency after transient ACTH elevation

A 62-year-old man was referred to our department for elevation of plasma ACTH and cortisol levels during nivolumab administration for renal cell carcinoma. Although his ACTH and cortisol levels had been maintained within their reference ranges, they were elevated to 232.7 pg/mL and 21.9 μg/dL, respectively, after eight courses of nivolumab without any subjective symptoms or Cushing's sign. He was hospitalized for endocrinological investigation. ACTH and cortisol returned to their normal ranges (29.18 pg/mL and 11.4 μg/dL, respectively) in the early morning on day 1, but fell down sharply to 3.7 pg/mL and 1.6 μg/dL, respectively, in the early morning on day 2 without subjective symptoms or vital sign changes. Brain magnetic resonance imaging showed no abnormality in his pituitary gland. ACTH response to CRH was apparently normal, but cortisol did not respond to increased ACTH. A rapid ACTH stimulation test showed slightly reduced response of cortisol to exogenous ACTH (1-24). These findings and his clinical course suggested secondary adrenal insufficiency arising from nivolumab-induced hypophysitis. In previous reports, most cases of immune checkpoint inhibitor (ICI)-induced hypophysitis were diagnosed based on adrenal insufficiency symptoms or hyponatremia with low ACTH and cortisol. The ACTH elevation observed in the present case may reflect destruction of the pituitary gland, suggesting that this finding may be important for early detection of ICI-induced hypophysitis. Our case underlines the necessity of close monitoring for subsequent onset of adrenal insufficiency when ACTH elevation is observed during ICI administration.

Small-cell lung cancer: what we know, what we need to know and the path forward

Small-cell lung cancer (SCLC) is a deadly tumour accounting for approximately 15% of lung cancers and is pathologically, molecularly, biologically and clinically very different from other lung cancers. While the majority of tumours express a neuroendocrine programme (integrating neural and endocrine properties), an important subset of tumours have low or absent expression of this programme. The probable initiating molecular events are inactivation of TP53 and RB1, as well as frequent disruption of several signalling networks, including Notch signalling. SCLC, when diagnosed, is usually widely metastatic and initially responds to cytotoxic therapy but nearly always rapidly relapses with resistance to further therapies. There were no important therapeutic clinical advances for 30 years, leading SCLC to be designated a 'recalcitrant cancer'. Scientific studies are hampered by a lack of tissue availability. However, over the past 5 years, there has been a worldwide resurgence of studies on SCLC, including comprehensive molecular analyses, the development of relevant genetically engineered mouse models and the establishment of patient-derived xenografts. These studies have led to the discovery of new potential therapeutic vulnerabilities for SCLC and therefore to new clinical trials. Thus, while the past has been bleak, the future offers greater promise.

Paraneoplastic syndromes associated with lung cancer

Paraneoplastic syndromes are signs or symptoms that occur as a result of organ or tissue damage at locations remote from the site of the primary tumor or metastases. Paraneoplastic syndromes associated with lung cancer can impair various organ functions and include neurologic, endocrine, dermatologic, rheumatologic, hematologic, and ophthalmological syndromes, as well as glomerulopathy and coagulopathy (Trousseau’s syndrome). The histological type of lung cancer is generally dependent on the associated syndrome, the two most common of which are humoral hypercalcemia of malignancy in squamous cell carcinoma and the syndrome of inappropriate antidiuretic hormone secretion in small cell lung cancer. The symptoms often precede the diagnosis of the associated lung cancer, especially when the symptoms are neurologic or dermatologic. The proposed mechanisms of paraneoplastic processes include the aberrant release of humoral mediators, such as hormones and hormone-like peptides, cytokines, and antibodies. Treating the underlying cancer is generally the most effective therapy for paraneoplastic syndromes, and treatment soon after symptom onset appears to offer the best potential for symptom improvement. In this article, we review the diagnosis, potential mechanisms, and treatments of a wide variety of paraneoplastic syndromes associated with lung cancer.

Severe hyponatremia caused by secondary adrenal insufficiency in a patient with giant pituitary prolactinoma

A 55-year-old-man was admitted to Saiseikai Central Hospital, Tokyo, Japan, complaining of nausea and appetite loss, and was found to have severe hyponatremia. Despite severe hyponatremia and plasma hypo-osmolarity, urinary sodium excretion was not reduced. A brain magnetic resonance imaging (MRI) scan revealed a giant pituitary prolactinoma, and endocrinological tests showed a markedly increased prolactin level. Despite the observation that the basal plasma ACTH level was normal, serum cortisol and urinary cortisol excretion levels were low. Rapid ACTH loading sufficiently stimulated an increase in serum cortisol levels, suggesting secondary adrenal insufficiency. Notably, loading of CRH induced a good ACTH response; however, the serum cortisol response remained low. In contrast, the continuous daily administration of exogenous ACTH dramatically increased serum cortisol levels. These discrepant responses may have been caused by the low biological activity of innate ACTH. Following partial resection of the prolactinoma, postoperative adjuvant therapy with cabergoline effectively reduced prolactin levels, but did not improve the hyponatremia. In contrast, hydrocortisone replacement therapy recovered the serum sodium level to the normal range. The present case is the first report describing a link between severe hyponatremia and biologically inactive circulating ACTH as a likely result of giant prolactinoma.

Clinical and organizational factors in the initial evaluation of patients with lung cancer: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines

BACKGROUND

This guideline is intended to provide an evidence-based approach to the initial evaluation of patients with known or suspected lung cancer. It also includes an assessment of the impact of timeliness of care and multidisciplinary teams on outcome.

METHODS

The applicable current medical literature was identified by a computerized search and evaluated using standardized methods. Recommendations were framed using the approach described by the Guidelines Oversight Committee of the American College of Chest Physicians. Data sources included MEDLINE and the Cochrane Database of Systematic Reviews.

RESULTS

Initial evaluation should include a thorough history and physical examination; CT imaging; pulmonary function tests; and hemoglobin, electrolyte, liver function, and calcium levels. Additional testing for distant metastases and paraneoplastic syndromes should be determined on the basis of these results. Paraneoplastic syndromes may have an adverse impact on cancer treatment, so they should be controlled rapidly with the goal of proceeding with definitive cancer treatment in a timely manner. Although the relationship between timeliness of care and survival is difficult to quantify, efforts to deliver timely care are reasonable and should be balanced with the need to attend to other dimensions of health-care quality (eg, safety, effectiveness, efficiency, equality, consistency with patient values and preferences). Quality care will require multiple disciplines. Although it is difficult to assess the impact, we suggest that a multidisciplinary team approach to care be used, particularly for patients requiring multimodality therapy.

CONCLUSIONS

The initial evaluation of patients with lung cancer should include a thorough history and physical examination, pulmonary function tests, CT imaging, basic laboratory tests, and selective testing for distant metastases and paraneoplastic syndromes.

Expression of melanocortin receptors in human prostate cancer cell lines: MC2R activation by ACTH increases prostate cancer cell proliferation

The melanocortin receptors (MCRs 1-5) are G protein coupled-receptors (GPCRs) that regulate food intake, inflammation, skin pigmentation, sexual function and steroidogenesis. Their peptide ligands, the melanocortins, are α-, β- and γ-melanocyte-stimulating hormone and adrenocorticotropic hormone (ACTH) all of which are secreted from the anterior pituitary gland under hypothalamic control. MC2R binds ACTH but has no affinity for the other melanocortins and is, thereby, pharmacologically different from MCRs that bind those ligands. Evidence suggests that elevated GPCRs transactivate the androgen receptor (AR), the critical mediator of prostate cell growth, and consequently promote prostate cancer cell proliferation. It may be that reduced central melanocortin signaling is coincidental with reversal of prostate cancer cachexia, but no data are available on the expression of, or the role for, MCRs in prostate cancer. Here, we show that MCR (1-5) mRNAs are expressed in androgen-dependent LNCaP and androgen-independent PC3 and DU-145 human prostate cancer cell lines. Further, MC2R, the specific target of ACTH, is expressed in LNCaP, PC3 and DU-145 cells. Among the several synthetic MCR peptide ligands that we used, only ACTH promoted concentration-dependent cell proliferation in the three cell lines as shown by MTT cell proliferation assay. In LNCaP cells, the effect was additive with testosterone stimulation and was partially blunted with SHU9119, a non-selective MCR antagonist. In the same cells, ACTH induced cAMP production and increased AR nuclear labeling in immunocytochemical assays. Our observations suggest that MC2R is involved in prostate carcinogenesis and that targeting MC2R signaling may provide a novel avenue in prostate carcinoma treatment.

Lung cancer-induced paraneoplastic syndromes

PURPOSE OF REVIEW

Paraneoplastic syndromes occur commonly in patients with lung cancer, especially cancers of neuroendocrine origin. The syndromes can be the first clinical manifestation of malignant disease or a harbinger of cancer recurrence. To update the knowledge that would facilitate the care of lung cancer patients with paraneoplastic syndromes, this review focuses on the epidemiology, pathogenesis, clinical features, and current management of the more common and clinically relevant syndromes.

RECENT FINDINGS

Certain combinations of clinical signs and symptoms (endocrine, neurologic, immunologic, dermatologic, metabolic, constitutional, and hematologic) are associated with lung carcinoma as a manifestation of the secretion of cytokines and hormones by these cells or as an associated immunologic response. These syndromes can be categorized by common causative mechanisms: hormonal syndromes, autoimmune syndromes, and other syndromes of less clear cause. Recent advances in medical technology have allowed better understanding of these syndromes and the development of novel diagnostic and therapeutic tools.

SUMMARY

Increased awareness of paraneoplastic syndromes associated with lung cancer should lead to the earlier recognition and diagnosis of malignancies, thereby improving the overall prognosis of patients and alleviating associated comorbidities. Despite the recent advances in recognizing and treating paraneoplastic syndromes, many questions remain to be answered.

Cushing syndrome secondary to ectopic adrenocorticotropic hormone secretion: the University of Texas MD Anderson Cancer Center Experience

BACKGROUND

Cushing syndrome (CS) secondary to ectopic adrenocorticotropic hormone (ACTH) secretion (EAS) has been described in association with a variety of tumors. The current experience with this syndrome was based on a few case series and individual case reports. Limited data were available about the tumors associated with CS-EAS in a cancer center setting. In this report, the authors have described their experience with CS-EAS at The University of Texas MD Anderson Cancer Center to further enhance the current understanding and management of this syndrome.

METHODS

This was a retrospective review of 43 patients with CS-EAS who were diagnosed between 1979 and 2009 at The University of Texas MD Anderson Cancer Center.

RESULTS

Different neuroendocrine tumors were associated with CS-EAS. Twenty-one patients (48.9%) had tumors located in the chest cavity, with bronchial carcinoid and small cell lung cancer representing the 2 most common causes. The ACTH source remained occult in 4 patients (9.3%) despite extensive workup. Clinical presentation varied, and the classic features of CS were not evident in some patients. Death occurred in 27 patients (62.8%), and the median overall survival was 32.2 months. Major morbidities included new-onset or worsening hyperglycemia (77%), symptomatic venous thromboembolism (14%), and infections (23%).

CONCLUSIONS

In patients with CS-EAS who attended a comprehensive cancer center, tumors originating in the chest cavity were the leading tumors associated with this syndrome. The authors suspect that CS-EAS is under reported because of the atypical presentation in some patients. Thus, they suggest careful evaluation of patients with neuroendocrine tumors to avoid missing coexisting CS-EAS.

Development of Cushing's syndrome during effective chemotherapy for small cell lung cancer

Paraneoplastic Cushing's syndrome caused by ectopic adrenocorticotropin (ACTH) production has been reported. However, most cases of this syndrome are diagnosed before first-line chemotherapy or at the time of disease recurrence. Here, we present a 53-year-old man who gradually developed the symptoms of Cushing's syndrome during effective chemotherapy for small cell lung cancer. His symptoms were controlled using mitotane, but his primary cancer progressed and he died 5 months after the start of chemotherapy. This very rare case of Cushing's syndrome associated with small cell lung cancer during effective chemotherapy is presented here.

Establishment and characterization of a novel cell line derived from a human small cell lung carcinoma that secretes parathyroid hormone, parathyroid hormone-related protein, and pro-opiomelanocortin

There are few case reports describing small cell lung carcinoma (SCLC), which secrete parathyroid hormone (PTH)-related protein (PTHrP) and result in hypercalcemia. We have established a novel cell line, derived from a 37-year-old woman with SCLC, which produced PTH, PTH-rP, and a part of proopiomelanocortin (POMC), and led to hypercalcemia. The cell line, named SS-1, was grown as floating cell clusters in DMEM/F12 medium supplemented with 10% fetal bovine serum and had a population doubling time of 72 h. The modal chromosome number was 47 (88%); marker chromosomes were not observed. The SS-1 cell line secreted not only PTHrP but also PTH, and both were decreased by CaCl(2) administration. Decreasing the concentration of Ca(++) in the growth medium stimulated the secretion of both PTHrP and PTH. The cell line had calcium sensing receptor (Cas-R). Since PTHrP and PTH secretion from the SS-1 cells was related to Ca(++) concentration in the growth medium, the cell line might be useful for the study of PTH-rP and PTH regulation as well as for SCLC analysis. In addition, the cells secreted N terminal POMC, the precursor of adrenocorticotropic hormone, in response to stimulation with corticotropin releasing hormone. In summary, we established a novel cell line, SS-1 from SCLC, which produced PTHrP, PTH and N terminal POMC.

Plasma ACTH in patients with bronchogenic carcinoma

Immunoreactive ACTH before and five hours after administration of 2 mg of dexamethasone was determined in patients examined in hospital for abnormalities on chest X-ray. Thirty patients had primary bronchial cancer, 15 had other lung conditions, mostly inflammatory infiltrations. The mean total ACTH and ACTH after dexamethasone suppression were significantly higher in the patients with bronchial cancer than in patients with other lung lesions or healthy controls. ACTH in plasma after administration of glucocorticoids was predominantly big ACTH. Several of the cancer patients had, however, ACTH levels within the same range as the other subjects. These results indicate that plasma ACTH determinations are of limited value as tumour markers for the detection of lung cancer although it is still possible that repeated sampling in patients with elevated ACTH levels may be of value when monitoring the therapy.

Cushing's syndrome due to ectopic ACTH production by (neuroendocrine) prostate carcinoma

Ectopic adrenocorticotropin (ACTH) secretion accounts for less than 10% of all causes of endogenous Cushing's syndrome (CS) and is usually associated with neuroendocrine tumors and small cell carcinoma of the lung. We report the case of a 62-year-old man with CS due to ectopic ACTH production by small cell carcinoma of the prostate. He presented with severe hypercortisolism and associated symptoms. Plasma neuron specific enolase (NSE) was grossly elevated. Despite performing a laparoscopic bilateral adrenalectomy, the patient died as a result of sepsis with multi-organ failure. Post-mortem immunohistochemical staining of prostate tumor tissue showed ACTH expression. ACTH staining was also performed in four additional patients with small cell carcinoma of the urinary tract without CS. None of these additional cases showed a positive staining for ACTH. Although a rare cause of ectopic ACTH production, neuroendocrine prostate carcinoma should be considered in male patients with Cushing's syndrome, in particular in those with an occult source of ACTH overproduction.

Multiple forms of corticotropin (adrenocorticotropic hormone, ACTH) and their significance

Big corticotropin (adrenocroticotropic hormone, ACTH), an immunoreactive form of ACTH with low biological activity and which elutes in the void volume on Sephadex G-50 gel filtration, is found in plasma and extracts of human pituitary and tumour. Controlled tryptic digestion of big ACTH releases a product with full corticotropic activity which is indistinguishable from the (1-39) ACTH with respect to size, charge and susceptibility to tryptic digestion. Immunoreactive ACTH, predominantly in the big form, is found in virtually all tissue extracts of carcinoma primary to or metastatic from the lung, but not of carcinoma metastatic to the lung, and even in precancerous lung lesions. The absence of clinical Cushing syndrome in patients with carcinoma of the lung and moderate elevation of plasma concentrations of ACTH is due to the low biological activity of big ACTH. Prolonged survival (for more than two years) of patients with lung carcinoma has been observed only in those whose plasma ACTH is low before therapy or after resection of the lung tumour. Rabbit, rat and mouse pituitaries contain an intermediate sized ACTH but the usual 1-39 peptide predominates in the pituitaries of monkey, sheep, dog, cat and guinea pig, as well as man. The hormonal form of ACTH appears to be an important factor regulating the cortisol/corticosterone ratio in mammalian adrenal corticoid secretion because administration of porcine ACTH to rabbits alters the adrenal secretory pattern so as to decrease corticosterone production and increase cortisol production.

Endocrine paraneoplastic syndromes in lung cancer

Lung tumors are capable of synthesizing and secreting peptide proteins (hormones) that lead to a variety of endocrine paraneoplastic syndromes. Knowledge about the clinical manifestations, pathophysiology, and treatment of these syndromes has evolved over time. This article provides an up-to-date overview of this knowledge.

Heterogeneity of so-called neuroendocrine lung tumors

The diagnosis of neuroendocrine (NE) lung tumor is dependent on a number of observations: organoid structure, dense core granules, and various molecular components, including chromogranin A, neurosecretory enolase, synaptophysin, neural cell adhesion molecules, and others. None of these is specific for lung tumors. The Kulchitsky cell, which has these characteristics, forms a carcinoid, which exemplifies the NE tumor. It is euploid, has few mitoses, no necrosis and a 5- to 10-year survival of over 90%. When carcinoids show malignant characteristics, i.e., increased mitoses and necrosis, they have been labeled atypical and have a survival of 50%. Because all other non-small cell lung tumors, especially large cell tumors, may show one or more of these things because of the inherent heterogeneity of lung tumors, the term NE has been applied to them without real evidence that this affects survival with or without chemotherapy. This is expensive and without clinical significance.

A new cause of Zollinger-Ellison syndrome: non-small cell lung cancer

Numerous epidemiologic studies suggest a relationship between lung cancer and peptic ulcer disease. Furthermore, various lung cancers synthesize and release a number of peptides such as gastrin and gastrin-releasing peptide that could cause acid hypersecretion; however, Zollinger-Ellison syndrome (ZES), because of a lung tumor, has never been described. We report such a patient for the first time. A 60-year-old man with a non-small cell lung carcinoma (large cell type) presented with diarrhea, heartburn, abdominal pain, and duodenal ulcers. Evaluation showed ZES was present (fasting hypergastrinemia, hyperchlorhydria) and control of all symptoms by omeprazole. No abdominal or cardiac tumor, the other known locations of gastrinomas causing ZES, was found on detailed tumor imaging studies. Resection of the lung tumor resulted in a decrease in gastrin levels to normal values. Plasma radioimmunoassays showed elevated gastrin, chromogranin A and normal levels of gastrin-releasing peptide, and 9 other hormones. The tumor showed similar immunocytochemical results. The characteristics of this case are compared with 100 cases of sporadic abdominal gastrinomas, and the evidence reviewed suggests why ZES should be considered in patients with lung cancer with peptic symptoms.

Gene regulation of vasopressin and vasopressin receptors in cancer

It is proposed that neuropeptide production by tumours is an important part of a special process of oncogenic transformation rather than a pre-existing condition of progenitor cells; this concept is called Selective Tumour gene Expression of Peptides essential for Survival (STEPS). All small-cell lung cancers and breast cancers evidently express the vasopressin gene, and this gene seems to be structurally normal in all but exceptional cases. Vasopressin gene expression in cancer cells leads to the production of both normal and abnormal forms of tumour vasopressin mRNA and proteins. Although the necessary post-translational processing enzymes are expressed in these cells, most processing seems to be extragranular, and most of the protein products become components of the plasma membrane. Small-cell lung cancer and breast cancer cells also express normal genes for all vasopressin receptors and produce normal vasopressin receptor mRNAs and V1a and V1b receptor proteins, and the vasopressin-activated calcium mobilising (VACM) protein; plus both normal and abnormal forms of the V2 receptor. Through these receptors, vasopressin exercises multifaceted effects on tumour growth and metabolism. A normal protein vasopressin gene promoter seems to be present in small-cell lung cancer cells, and this promoter contains all of the transcriptional elements known to be involved in gene regulation within hypothalamic neurones. Since these elements largely account for regulation of tumour gene expression observed in vitro, it is likely that as yet unknown factors are selectively produced by tumours in vivo to account for the observed seemingly autonomous or unregulated production of hormone in tumour patients. Promoter elements thought to be responsible for selective vasopressin gene expression in small-cell lung cancer probably include an E-box and a neurone restrictive silencer element close to the transcription start site. It is possible that transcription factors acting at these same elements can explain selective vasopressin expression, not only in small-cell tumours, but also in all other tumours such as breast cancer. By extrapolation, similar mechanisms might also be responsible for the expression of additional features that characterize the 'neuroendocrine' profile of these cancers.

Expression of pancreatitis-associated protein (PAP) mRNA in gastrointestinal cancers

CONCLUSION

Pancreatitis-associated protein (PAP) mRNA is expressed in some cases of gastric and colorectal cancers resulting from an ectopic expression in dedifferentiated cancer cells.

BACKGROUND

The PAP gene is identical to the hepatoma-intestine-pancreas (HIP) gene, which is expressed in hepatoma. Expression in cancer might be another characteristic of PAP.

METHODS

Fresh surgical specimens of 100 gastrointestinal cancers, 14 benign digestive diseases, and six normal organs were studied with nonisotopic in situ hybridization (ISH) using biotin-labeled cDNA probe.

RESULTS

PAP mRNA was detected in 10% (6/60) of gastric cancers, 21.4% (6/28) of colorectal cancers, 20.0% (1/5) of pancreatic cancers and 0% of biliary tract (three), esophageal (one), and hepatocellular cancers (three). Reverse transcription-polymerase chain reaction (RT-PCR) detected PAP mRNA in these ISH-positive cases. PAP mRNA was not detected in noncancerous portions, benign disease tissues, or normal organs except for the small intestine. There was no relationship between PAP mRNA expression and any clinicopathological factors.

Pulmonary neuroendocrine cell system in pediatric and adult lung disease

In humans lungs affected by naturally occurring pulmonary disease, the pulmonary neuroendocrine cell system, which is normally arranged in a sparse but even distribution throughout the respiratory tract, increases in size. It is likely that the stimulus for this is pulmonary injury and that its purpose is the paracrine regulation of the restoration of pulmonary tissues to their normal state, an hypothesis supported by studies of animal lungs subjected to experimental injury as well as of the development of human and animal lungs in utero. Initially, this increase involves the development of interrupted rows of neuroendocrine cells. In the later stages, however, development of more disorderly intraepithelial aggregates can occur and the small, locally invasive neuroendocrine cell lesions known as tumourlets may occasionally result. Both of these latter structures often contain secretory products not found in the neuroendocrine cells of normal human lungs, probably indicating a derangement of what appears to be a fundamentally physiological response. It is likely that, in some circumstances, this disorderly change may contribute to pulmonary disease as well as being the result of it.

Gastrin levels in serum and bronchoalveolar lavage fluid of patients with lung cancer: comparison with patients with chronic obstructive pulmonary disease

BACKGROUND

The gastrin gene is known to be expressed in all classes of bronchogenic carcinomas. Furthermore, high levels of gastrin have been reported in both the bronchoalveolar lavage (BAL) fluid and serum of patients with lung cancer. Based on these preliminary data a study was conducted to evaluate the usefulness of gastrin measurements in the diagnosis and staging of lung cancer.

METHODS

Thirty-five patients with lung cancer (26 non-small cell (NSCLC) and nine small cell (SCLC)) and 25 patients with chronic obstructive pulmonary disease underwent fibreoptic bronchoscopy and BAL. Gastrin levels were determined in both BAL fluid and the serum and compared with each other and with staging.

RESULTS

No difference was found between the gastrin levels in the BAL fluid or serum of the study groups. There was no correlation with the stage in NSCLC and no correlation was found between the gastrin levels in the serum and the BAL fluid. A significant difference was seen in gastrin levels in BAL fluid between extensive and limited SCLC (p < 0.05).

CONCLUSION

There is no evidence of clinical usefulness for gastrin measurements in lung cancer.

Ectopic ACTH syndrome

Ectopic ACTH syndrome represents a cancer-induced amplification of a property [proopiomelanocortin (POMC) peptides production] normally present in the cells from which the cancer originated but with aberrant posttranslational processing of POMC resulting in a greatly elevated secretion of ACTH precursors. The classic ectopic ACTH-producing tumors described in the 1960s were highly malignant but more recently slowly growing tumors such as carcinoids are reported with increasing frequency. Clinical features of patients with ectopic ACTH were analyzed, including biochemical abnormalities, plasma ACTH, cortisol and urinary steroids. Dynamic tests such as high-dose dexamethasone suppression, metyrapone and ovine-CRH (oCRH) stimulation were explored, as well as inferior petrosal sinus ACTH sampling before and after oCRH. Among the tumor markers examined, elevation of ACTH precursors was uniformly present followed by increased output of calcitonin, gut hormones, oncofetal and placental hormones in decreasing order. Since more than 90% of ectopic ACTH tumors are neuroendocrine in nature exhibiting APUD characteristics, their 2 markers, neuron-specific enolase and chromogranins are very useful. The imaging procedures for localization of the tumor ranged from chest X-rays to computed tomography and magnetic resonance of the chest and abdomen. Abdominal ultrasonography was also useful. Finally somatostatin receptor scintigraphy permitted demonstration of unrecognized tumors and/or metastases, even when the tumors were occult. The ACTH content, immunostaining for APUD markers and altered POMC processing were evaluated in ectopic tumors and/or metastases. Occult ectopic ACTH syndrome of more than 4-6 months of symptoms without the emergence of an obvious source was reviewed. Since the tumors are often clinically and biochemically undistinguishable from pituitary-dependent Cushing's disease, inferior petrosal sinus sampling for ACTH after oCRH stimulation established the diagnosis in over 90% of the cases. 60% of the occult tumors were thoracic carcinoids (3/4 bronchial carcinoids), followed by small cell lung cancer and pancreatic neuroendocrine tumors. In 12% the primary etiology was not detected. The rare syndrome of ectopic CRH syndrome (6 published cases) leading to excessive stimulation of the pituitary which became hyperplastic and secreted excessive amounts of ACTH is discussed. Finally, the 12 published cases and 1 unreported patient with ectopic CRH-ACTH tumors were reviewed, the majority being metastatic small cell lung carcinomas, bronchial and thymic carcinoids.

Expression patterns of messenger ribonucleic acids encoding prohormone convertases (PC2 and PC3) in human pituitary adenomas

OBJECTIVE

Prohormone convertases (PC2 and PC3) have been reported to play an important role for prohormone processing in rodent pituitaries. However, expression of mRNAs encoding these enzymes has not been characterized in human pituitaries. In addition, altered or insufficient prohormone processing has been reported in some human pituitary adenomas. Thus, the expression patterns of these mRNAs in non-tumorous and tumorous human pituitaries should be examined.

DESIGN

Total RNAs were extracted from non-tumorous or tumorous human pituitaries to analyse PC2 and PC3 mRNA expression.

SAMPLES

Five ACTH producing adenomas, 11 GH producing adenomas, one PRL producing adenoma and five non-functioning adenomas were obtained at surgery. Two non-tumorous pituitaries were also included in this study.

MEASUREMENTS

The contents were quantitatively measured by Northern blot analysis using rat PC3 cDNA or human PC2 cDNA as a probe. The method was also developed for the detection of PC2 mRNA by Southern blot analysis of reverse transcriptase-polymerase chain reaction (RT-PCR) products.

RESULTS

PC2 and PC3 mRNAs in non-tumorous samples were detected by Northern blot analysis whereas their contents in tumorous samples varied from high levels to undetectable. Marked variation of PC3 mRNA levels was observed among GH producing adenomas. ACTH producing adenomas were observed to express PC3 mRNA. Northern blot analysis also revealed that PC2 mRNA levels in ACTH producing adenomas were low except for one sample. PC2 mRNA expression in GH producing adenomas was confirmed by Southern blot analysis of RT-PCR products. This procedure also confirmed the various levels of PC2 mRNA expression among ACTH producing adenomas.

CONCLUSION

The expression of PC2 and PC3 mRNA in human pituitaries has been confirmed. However, their expression has been observed to vary quantitatively and not to be restricted to certain types of pituitary cells.

Panhypopituitarism caused by solitary parasellar metastasis from lung cancer

Clinical panhypopituitarism caused by cancer with parasellar metastasis and hypothalamic invasion is very rare. This report concerns a lung cancer patient who had solitary parasellar metastasis with diabetes insipidus and panhypopituitarism as an initial manifestation, which was documented by contrast-enhanced computed tomographic scan, Gd-DTPA-enhanced magnetic resonance imaging, and endocrinologic studies.

Production of immunoreactive atrial natriuretic polypeptide in neuroendocrine tumors

BACKGROUND

Peptide hormone synthesis in neuroendocrine tumors is a well-recognized phenomenon. However, production in neuroendocrine tumors of atrial natriuretic polypeptide (ANP), a newly discovered peptide hormone from the heart, has not been studied extensively.

METHODS

The presence of immunoreactive human ANP (IR-hANP) in neuroendocrine tumors was determined using a specific human ANP radioimmunoassay. Neuroendocrine tumors examined included 9 small cell carcinomas of the uterus, 28 small cell carcinomas of the lung, 20 carcinoid tumors, 54 pancreatic endocrine tumors, 17 neuroblastic tumors, 14 pheochromocytomas, and 14 medullary carcinomas of the thyroid. Twenty atrial tissues also were examined as the control. Molecular size of IR-hANP in the extracts of atrial and tumor tissues was determined by gel chromatography.

RESULTS

IR-hANP was detected in the extracts of small cell carcinoma of the uterus, small cell carcinoma of the lung, and carcinoid tumor, with concentrations ranging from 3.1 to 210 ng/g wet weight tissue. No IR-hANP was detected in the extracts of pancreatic endocrine tumor, neuroblastic tumor, pheochromocytoma, and medullary carcinoma of the thyroid. The frequency of production of IR-hANP in neuroendocrine tumors was highest in small cell carcinoma of the uterus (44%), followed by small cell carcinoma of the lung (18%) and carcinoid tumor (15%). IR-hANP present in the extracts of small cell carcinomas of the uterus had molecular size heterogeneity, with three fragments in addition to alpha-, beta- and gamma-human ANP.

CONCLUSIONS

These results indicate that IR-hANP is produced by neuroendocrine tumors and that the molecular size of IR-hANP in tumor tissues is different from that in atrial tissues.

Ectopic ACTH syndrome associated with anorectal carcinoma. Report of a case and review of the literature

A 25-year-old black homosexual was noted to be hypertensive, hypokalemic, and to have a rectal mass. Histopathology of the biopsied lesion revealed a mixture of poorly differentiated squamous cell and undifferentiated small cell carcinoma. Abdominopelvic CT showed multiple liver metastases, minimal local tumor extension, and normal adrenal glands. Despite aggressive treatment, he remained hypertensive and hypokalemic. Endocrine work-up revealed: normal 24-hr VMA and catecholamines, normal serum aldosterone and renin levels, elevated urinary free cortisol (3360 micrograms/24 hr), elevated serum cortisol (60 micrograms/dl), and elevated serum ACTH (1697 pg/dl). Liver biopsy confirmed metastatic anorectal carcinoma, and immunohistochemical stains of the rectal biopsy were positive for ACTH and neuron-specific enolase. Although many types of neoplasms have been associated with ectopic ACTH production, small cell carcinoma of the lung is the most common. While there are many reports of colorectal and anorectal neuroendocrine small cell carcinomas, few of these tumors have been associated with clinical ectopic hormone production. This case represents the first report of the ectopic ACTH syndrome associated with anorectal carcinoma.

Expression of the pro-opiomelanocortin gene in lung neuroendocrine tumours: in situ hybridization and immunohistochemical studies

Neuroendocrine tumours of the lung may be associated with the ectopic adrenocorticotrophin (ACTH) syndrome and may synthesize and secrete ACTH-related peptides in the absence of the syndrome. However, immunocytochemical analysis may not confirm these biochemical findings, particularly in small cell carcinoma, which is poorly granulated. To investigate further the morphological evidence for expression of the pro-opiomelanocortin (POMC) gene in neuroendocrine lung tumours, we have examined a series of 46 small cell carcinomas and 13 carcinoid tumours of the lung by in situ hybridization for POMC mRNA using a digoxigenin-labelled oligoprobe. We have compared the findings with the immunocytochemical detection of ACTH and beta-endorphin. In situ hybridization was positive in 15 of 46 small cell carcinomas (33 per cent) and in 8 of 13 carcinoid tumours (62 per cent). Immunocytochemical staining was positive in only one carcinoid tumour. These in situ hybridization studies have corroborated biochemical data indicating POMC gene expression in a high proportion of lung neuroendocrine tumours. This suggests that the low levels of expression detected by immunocytochemistry may be due to low levels of hormone storage. Multivariate analysis showed a weak negative association between POMC expression and survival in small cell carcinomas, although this did not reach statistical significance.

Ectopic production of ACTH and corticotropin-releasing hormone (CRH)

The most common ectopic production of a pituitary hormone is the one of ACTH leading to Cushing's syndrome. Ectopic ACTH-hypersecretion is the cause of Cushing's syndrome in 10-15% of all cases. The ACTH-secreting tumours are often oat-cell carcinomas of the lung, less frequently pancreatic cancers, hypernephromas, or C-cell carcinomas of the thyroid. Some of these tumours may be benign or semi-benign as the rare carcinoid tumours and cause great problems in the differential diagnosis of ACTH-dependent hypercortisolism. Out of 173 of our patients with Cushing's syndrome observed in the last 12 years 21 were caused by ectopic ACTH-production. Of these 21 patients 13 have a small cell carcinoma of the lung. The ectopic ACTH-syndrome often has typical clinical features caused by the levels of ACTH and cortisol leading to hypocalcemic alkalosis with muscle weakness and wasting, carbohydrate intolerance, and hypertension with oedema. The survival time in many of these patients is not long enough to allow them to develop typical signs of Cushing's syndrome though they are often highly pigmented. These patients are easily diagnosed. However, patients with small tumours which do not cause very elevated ACTH-levels and who have the more typical clinical signs of full-blown Cushing's syndrome are difficult to recognize. For the differential diagnosis of ACTH-dependent Cushing's syndrome the corticotropin-releasing hormone (CRH) stimulation test and dexamethasone suppression test with high doses are helpful. In special cases the venous sampling procedure for ACTH-measurements is necessary, also CT or NMR is helpful. Ectopic CRH-production is a rare cause of ACTH-dependent Cushing's syndrome. Patients with ectopic CRH-production and consecutive ACTH-hypersecretion from the pituitary have not been studied extensively. There are especially no well documented results of the use of the CRH-stimulation test in vivo in this group of patients with Cushing's syndrome. On the other hand, in the documented cases, not only CRH-, but also ACTH-production was found in the tumours. So far, this rare cause of ACTH-dependent Cushing's syndrome has to be excluded or confirmed by the measurement of endogenous CRH-levels. But until now we have not been able to detect one single case of ectopic CRH-production using a sensitive homologous CRH-radioimmunoassay over a period of more than 8 years in which we have seen nearly 120 newly diagnosed patients with ACTH-dependent Cushing's syndrome. Only in the plasma and tumour tissue of two patients of other groups have we found high CRH-levels.

Limited clinical usefulness of plasma corticotropin-releasing hormone, adrenocorticotropin and beta-endorphin measurements as markers of lung cancer

We measured plasma corticotropin-releasing hormone (CRH), ACTH, beta-endorphin (beta-EP), and cortisol levels as possible tumor markers in a sequence of 103, randomly selected, patients with lung cancer but without the ectopic Cushing's syndrome and in 72 age- and sex-matched controls. Plasma CRH levels of cancer patients were similar to those of controls both in patients sampled in the morning or in the afternoon. On the other hand, plasma ACTH levels of cancer patients were significantly higher than control patients both in the morning and in the afternoon and showed a preserved circadian rhythm. However, about 35% of cancer patients sampled in the morning and about 60% of those sampled in the afternoon had ACTH levels within the 95% confidence interval (CI) of controls. Also plasma beta-EP levels were more elevated in cancer patients than controls in the morning but about 33% of them and about 80% of those sampled in the afternoon had beta-EP levels within the 95% CI of controls. Despite the higher plasma ACTH levels, cancer patients had cortisol plasma levels similar to controls with preserved circadian rhythm. In conclusion, although mean plasma ACTH and beta-EP were higher in patients affected by lung cancer, their measurements, as well as those of CRH, have practically no diagnostic value. Perhaps measurement of ACTH levels in the bronchial lavage may be more helpful.

Small cell carcinoma with two paraendocrine syndromes

Simultaneous elevated levels of ectopic arginine vasopressin (AVP) and ectopic adrenocorticotropin (ACTH) were found in a patient with small cell carcinoma (SCC). The finding of one of these paraendocrine syndromes at the time of diagnosis is common; however, the simultaneous presence of both syndromes has been reported in the literature only on four occasions in the past 25 years. This is the only report in which elevated plasma levels of both hormones are documented in a patient who simultaneously fulfills the criteria for the syndrome associated with each ectopically produced peptide. In the English-language literature, this is the first case that demonstrates by immunohistochemical staining the presence of both of these hormones in the patient's neoplasm. In addition to the use of radiographs, the presence of paraendocrine disorders can provide a method of monitoring the patient's response to therapy. The levels of ACTH and AVP were assayed during this patient's course and correlated with disease refractory to therapy, resulting in poor survival.

Medullary carcinoma of the thyroid as a cause of Cushing's syndrome: a case with ectopic adrenocorticotropin secretion characterized by double enzyme immunostaining

A case of a medullary carcinoma of the thyroid gland that secreted both calcitonin and adrenocorticotropin (ACTH) is reported. The patient was a 32-year-old man who was referred to the Clinical Center of the National Institutes of Health with radiologic evidence of intrathoracic and hepatic masses accompanied by florid Cushing's syndrome. Serum levels of calcitonin and ACTH were elevated. The thoracic and hepatic masses were resected. The histologic findings were typical of medullary carcinoma of the thyroid with extensive metastases to the liver. The neoplasm had a predominantly solid pattern, and the neoplastic cells were either round or spindled, many with cytologic atypia. Immunohistochemical analysis of fixed, paraffin-embedded sections demonstrated chromogranin, calcitonin, and ACTH in the neoplastic cells. The immunostaining for chromogranin was intense in all of the cells, whereas weaker staining for calcitonin and ACTH was present in scattered cells. Electron microscopy revealed sparse secretory granules in the majority of tumor cells; a minority of neoplastic cells contained numerous granules. We further characterized this neoplasm by performing dual immunohistochemical analysis. This technique clearly demonstrated the presence of ACTH and calcitonin within the same neoplastic cells. Thus, the medullary carcinoma of the thyroid in this patient was the source of ectopic ACTH secretion causing Cushing's syndrome. In addition, this report highlights the value of using double immunostaining to localize both the ACTH and calcitonin within the same cells.

The secretory granule peptides 7B2 and CCB are sensitive biochemical markers of neuro-endocrine bronchial tumours in man

OBJECTIVE

Bronchial tumours are the most frequent cause of the ectopic ACTH syndrome. Two types of tumours are classically responsible: the relatively benign carcinoids and the highly aggressive small cell carcinomas. Both have neuro-endocrine features and are thought to originate from the endocrine component of the bronchial tree. Our objective was to assess the sensitivity of 7B2 and secretogranin 1 as new biochemical markers of neuro-endocrine differentiation in these tumours in comparison with gastrin releasing peptide.

METHODS

Tissue concentration of 7B2, secretogranin 1 fragments (GAWK and CCB), gastrin releasing peptide and beta-endorphin were measured in normal human lung (n = 4), bronchial carcinoid tumours with (n = 5) and without (n = 15) the ectopic ACTH syndrome, small cell carcinomas (n = 2), squamous cell carcinomas (n = 11) and adenocarcinomas (n = 6). Molecular weight forms of immunoreactive--ACTH, -GAWK, -gastrin releasing peptide, and -7B2 were also examined using gel exclusion chromatography and Western blot analysis.

RESULTS

We detected 7B2 immunoreactivity in 19 of 22 neuro-endocrine lung tumours (with values ranging from less than 5 to 555 fmol/mg wet weight tissue), CCB immunoreactivity in 20 of 22 tumours with neuro-endocrine features (with values ranging from less than 5 to 19,875 fmol mg wet weight tissue) and gastrin releasing peptide immunoreactivity in 10 of 22 neuro-endocrine lung tumors (with values ranging from less than 5 to 11,132 fmol/mg wet weight tissue). Immunoreactive 7B2 and CCB were detected neither in tumours with non-endocrine features, nor in the four normal lung specimens. Differing molecular weight forms of immunoreactive 7B2 in two bronchial carcinoids associated with the ectopic ACTH syndrome showed a predominant signal corresponding to a molecular weight of 22 kDa; in addition, a second signal of 19 kDa was also present. The differing molecular weight forms of immunoreactive ACTH related peptides in the five tumours responsible for the ectopic ACTH syndrome showed, in addition to ACTH1-39, the constant presence in variable proportions of corticotrophin-like intermediary lobe peptide (or ACTH18-39). The differing molecular weight forms of immunoreactive GAWK showed heterogeneous results with materials eluting at Kav of 0, 0.3 and 0.4 respectively. In the three bronchial carcinoids studied, two immunoreactive gastrin releasing peptide molecular weight forms were always found at Kav of 0.5 and 0.85 corresponding to gastrin releasing peptide and its fragment 14-27 respectively.

CONCLUSION

Our results show that 7B2 and the two fragments of secretogranin 1 (GAWK and CCB) are the best biochemical markers of neuro-endocrine differentiation in human lung tumours.

A case of cervical carcinoma of the uterus presenting with hyperosmolar non-ketotic coma as a manifestation of ectopic adrenocorticotropic hormone syndrome

A case of advanced cervical carcinoma of the uterus with ectopic adrenocorticotrophic hormone (ACTH) syndrome is described. The patient was seen for general malaise 21 months after surgical treatment of the primary lesion whose histology was undifferentiated small cell carcinoma of the uterine cervix. She had extensive metastases in the liver and the abdominal wall. In addition to the typical clinical manifestations of Cushing's syndrome such as moon face, central obesity and acne vulgaris, hyperglycemia was so severe that she was in a hyperosmolar non-ketotic coma. Endocrinological examinations revealed elevated plasma ACTH and cortisol, and urinary excretion of 17-hydroxycorticosteroids and 17-ketosteroids, which were not suppressed by high-dose dexamethasone administration. Based on these clinical and laboratory findings, a diagnosis of ectopic ACTH syndrome was made. Among the results of other endocrinological examinations conducted to find the etiological cause of the hyperglycemic coma, which seemed to be unusual for ectopic ACTH syndrome, the plasma somatostatin level was abnormally high. Metastatic tumors in the liver obtained at the time of autopsy contained large amounts of both ACTH and somatostatin, and gel filtration studies revealed that the peptides produced by the tumor had the molecular sizes of the biologically active forms of the respective peptides. These observations suggest possible involvement of the somatostatin in deteriorating glucose intolerance to develop hyperglycemic hyperosmolar non-ketotic coma as a drastic disturbance of metabolism.

The use of biomarkers in the prediction of survival in patients with pulmonary carcinoma

Data on ten variables and 16 biomarkers were obtained on 119 patients with newly diagnosed pulmonary cancer. The prognostic value of 16 biomarkers (alpha-1-antitrypsin [AAT], adrenocorticotropic hormone [ACTH], alpha-fetoprotein [AFP], carcinoembryonic antigen [CEA], human chorionic gonadotropin [HCG], immune complexes, immunoglobulins, N-terminal peptide of proopiomelanocortin [NTERM], and tumor-associated antibody [TAA]) was tested by adding these to the model of age, gender, stage, morphology, Feinstein's classification of symptoms, Karnofsky scale, leukocyte count, recent weight loss, and liver enzymes. Using Cox's regression method and a forward stepwise procedure, seven biomarkers (ACTH, AAT, AFP, calcitonin, HCG, TAA, and prolactin) entered the model. Elevated levels of cortisol and TAA were associated with longer survival. The selection of biomarkers by stepwise regression needs to be interpreted with caution, especially since the Z scores were found to be dependent on the particular variables included in the model. Furthermore, when dichotomized on maximum of the normal laboratory values, HCG and AFP were infrequently (2%) elevated. The lack of correlation among the biomarkers supports the hypothesis of random derepression of the genome of cancer cells. Further studies in improved modeling and the formulation of a biomarker index could enhance our understanding of the biology of cancer.

Neuroendocrine alterations in nude mice with a human lung carcinoma producing pro-opiomelanocortin, corticotrophin-releasing hormone and arginine vasopressin

A mucoepidermoid carcinoma of the lung (ICD classification 8430/3) resected from a patient with no clinical signs of pituitary-adrenal alterations was transplanted into 2-month-old athymic nu/nu nude mice, with the purpose of studying the effects exerted by the human tumour on the host hypothalamo-pituitary-adrenal axis. The tumour produces peptides derived from different regions of pro-opiomelanocortin (POMC: ACTH, 7.6 +/- 0.7; N-terminal POMC, 6.6 +/- 0.6; beta-LPH/endorphin, 7.3 +/- 0.7; and alpha-MSH;3.8 +/- 0.5 pmol/g wet tissue) and the neuropeptides corticotrophin-releasing hormone and arginine vasopressin (CRH: 3.6 +/- 0.4 and AVP: 1.1 +/- 0.2 pmol/g wet tissue). Immunohistochemical staining of consecutive sections of the tumour indicated that staining of tumour cells for the different peptides was not uniform and although some cells co-stained with CRH and AVP, POMC-positive cells appeared to be distinct from CRH and AVP cells. Tumour extracts were chromatographed on Sephadex G-75 and fractions monitored for POMC-derived peptides. A single peak with characteristics of alpha-MSH was detected. The ACTH, N-POMC and beta-LPH/endorphin radioimmunoassays (RIA) detected a peak at large molecular weight, eluting at the position expected for POMC. These RIA systems also revealed an ACTH(1-39) peak and another peak which probably correspond to 13 kDa ACTH, a peak eluting at the position of hN-POMC(1-48), a beta-LPH-like peak, and a smaller sized peak which may represent alpha- or gamma-endorphin. The ACTH, N-POMC and beta-LPH/endorphin contents of anterior lobe (AL) extracts, but not neutrointermediate lobe (NIL) extracts, showed a striking decrease in tumour-bearing (TB) nude mice. However, while no difference was seen in the alpha-MSH content of AL extract between TB and control (C) nude mice, it decreased in NIL extracts of TB animals. The contents of CRH and AVP in stalk-median eminence extracts of TB nude mice was significantly lower than that of C nude mice. Basal plasma corticosteroids were raised in TB nude mice at levels comparable to those in stressed C nude mice, and although adrenal weights did not vary between TB and C nude mice, morphological changes indicating hypertrophy were found in the adrenal glands of the host animals. It was concluded that the tumour dramatically alters the hypothalamo-pituitary-adrenal axis of the host, and that it may be a useful model for studying tumour-host interactions in ectopic hormone-producing tumours.

Initiation of pro-opiomelanocortin mRNA from a normally quiescent promoter in a human small cell lung cancer cell line

We describe the characteristics of pro-opiomelanocortin (POMC) mRNA synthesized by a human small cell lung cancer (SCLC) cell line that secretes a peptide immunoreactive with antibodies to the POMC-derived component, adrenocorticotropin. While no alteration in restriction endonuclease pattern or structure was found for the SCLC-derived pomc gene vs. the previously described human pomc gene cloned from a fetal liver library, Northern-blot analysis of SCLC RNA using pomc-derived probes showed a hybridizing transcript more than 300 nucleotides longer than POMC mRNA isolated from human pituitaries, as well as a pomc-gene-hybridizing mRNA the same length as pituitary-derived transcripts. 5' end mapping and primer extension analyses showed that the novel mRNA species is initiated at a site 371 bp upstream from the 5' end identified for pituitary-derived POMC mRNA. We conclude that synthesis of POMC transcripts occurs from an ordinarily quiescent promoter in the SCLC cell line we have studied, as well as from the pomc promoter normally used in pituitary cells.

Corticotrophin-like intermediary lobe peptide as a marker of alternate pro-opiomelanocortin processing in ACTH-producing non-pituitary tumours

In order to evaluate which of human (h) corticotrophin-like intermediary lobe peptide (CLIP) or h beta-melanocyte stimulating hormone5-22 (h beta MSH5-22) was the better marker of alternate pro-opiomelanocortin (POMC) processing, both peptides were simultaneously sought in the same tissue extracts from a normal human pituitary, six corticotrophic adenomas, and four non-pituitary tumours responsible for an ectopic ACTH syndrome. Human CLIP was detected using a combination of gel exclusion chromatography and two different radioimmunoassays (RIAs): a mid-ACTH RIA which recognized ACTH but not CLIP, and a COOH-ACTH RIA which recognized both molecules. Human beta MSH5-22 had been measured previously. Neither hCLIP nor h beta MSH5-22 were detected in the normal or tumoural pituitaries. The four non-pituitary tumours, in contrast, contained both peptides; the hCLIP and h beta MSH5-22 ratios (CLIP/CLIP + ACTH and h beta MSH5-22/h beta MSH5-22 + h gamma LPH) ranged from 40 to 94% and from 24 to 46%, respectively. In a given tissue the hCLIP ratio was always higher than the h beta MSH5-22 ratio. hCLIP is therefore the better marker of alternate POMC processing.

Ectopic hormone production

Current understanding of the phenomenon of ectopic hormone production is largely based on a histopathological and immunocytochemical analysis of peptide hormone secreting tumours arising in non-endocrine tissues. Recent advances in the study of gene regulation show that the tissue-specific expression of genes is a highly sophisticated process and is unlikely to be disturbed by a spontaneous event such as point mutation in DNA. Study of several genes for frequently found ectopic hormones, i.e. prop-opiomelanocortin, vasopressin/neurophysin II, gastrin-releasing peptide, parathyroid hormone-related peptide, calcitonin gene-related peptide and beta-chorionic gonadotropin, suggests they are transcribed as they would be in their natural cell of origin. It is argued therefore that these data are compatible with the concept that the tumour cell of origin was capable of expressing these peptides, if only in a minor or transient manner. In one example, the ectopic ACTH syndrome, it is also necessary to explain the non-suppression of this gene's expression by elevated levels of glucocorticoids. Recent work suggests that this may result from physically present, but biologically inactive glucocorticoid receptors, a phenomenon that has occasionally been noted in hormonally inactive tumour tissue and cell lines.