ACTH LPH and related peptides in the ectopic ACTH syndrome

Two cases of pancreatic neuroendocrine tumors with ectopic ACTH syndrome during their disease course

Pancreatic neuroendocrine tumors (PanNETs) are rare malignant tumors that occur in the pancreas. They are divided into functioning and non-functioning tumors based on the presence or absence of their specific hormonal hyper-expression symptoms. Adrenocorticotropic hormone (ACTH)-producing PanNETs are rare, functional tumors, and their clinical characteristics and outcomes have not been well reported.Here, we report the cases of two patients with PanNETs who presented with ectopic ACTH syndrome (EAS) during the course of their disease. Case 1 involved a non-functioning PanNET at the time of surgery. During treatment for recurrent liver metastases, the patient presented with EAS and tumor-associated hypercalcemia, probably due to ACTH and parathyroid hormone-related peptide (PTHrP) production from the liver tumor. Case 2 was a gastrinoma, and similar to Case 1, this patient presented with EAS during the treatment of recurrent liver metastases.It is not uncommon for patients with PanNETs to have multiple hormones and develop secondary hormone secretion during their disease course, although tumor phenotypes differ between primary and metastatic sites. In patients with functioning PanNETs, symptom control with anti-hormonal therapy is essential, in addition to anti-tumor therapy, especially for EAS, which is an endocrine emergency disease that requires prompt diagnosis and treatment.

Pars intermedia peptides: studies in adult humans

A combination of radioimmunoassays and chromatography under acid-dissociating conditions has been used to obtain profiles of ACTH and LPH-related peptides in human plasma and cerebrospinal fluid. The spectra of peptides observed in these two fluids differ markedly. ACTH, beta-LPH, gamma-LPH and beta-endorphin are observed in the plasma of normal subjects and patients with increased pituitary ACTH secretion, whereas cerebrospinal fluid contains ACTH, beta-LPH, gamma-LPH and beta-endorphin, a 31 000-molecular-weight putative precursor having ACTH, LPH and gamma-MSH immunoreactivities, as well as pro-gamma-MSH(1-77) and smaller immunoreactive gamma-MSH fragments, alpha-MSH was not observed in blood or cerebrospinal fluid but this pars intermedia peptide and corticotropin-like intermediate lobe peptide (CLIP) were both found in tumour tissues obtained from patients with the ectopic ACTH syndrome. In vitro studies of human pituitary tumour tissues confirmed concomitant secretion of ACTH, beta-LPH, gamma-LPH, beta-endorphin and pro-gamma-MSH, which could be stimulated by a preparation of crude stalk median eminence and synthetic arginine vasopressin, from the rat, and could be suppressed by hydrocortisone. Clinical studies in which electroacupuncture was used to alleviate the symptoms of heroin withdrawal or recurrent pain revealed that concentrations of met-enkephalin and beta-endorphin, respectively, may rise in cerebrospinal fluid in association with relief of symptoms.

Adrenal enlargement and failure of suppression of circulating cortisol by dexamethasone in patients with malignancy

The aim of this study was to further elucidate the activity of the hypothalamo-pituitary-adrenal (HPA) axis in patients with malignancy and to correlate this with the size of the adrenal glands. Fourteen patients with a variety of malignancies were studied prior to receiving cytotoxic chemotherapy. During routine staging computerized tomographic (CT) scans, the size of the body, medial and lateral limbs of the adrenal glands were measured and compared with those of a normal group of patients studied previously. Measurements of 09:00 h serum cortisol and plasma adrenocorticotropic hormone (ACTH) levels were made before and after the administration of dexamethasone (0.5 mg 6-hourly for 48 h) in addition to the peak cortisol response to i.v corticotropin releasing hormone (CRH). Overall, patients with malignancy had significantly larger adrenal glands than patients without malignancy; those with non-haematological malignancies had larger glands than patients with haematological malignancies. Following dexamethasone to suppress circulating cortisol levels, nine patients (64%) demonstrated abnormal resistance with cortisol levels > 50 nmol l(-1): mean value 294 nmol l(-1) (range 67-1147). Those patients who failed to suppress after dexamethasone had significantly larger adrenal glands than those that did suppress and tended to have non-haematological malignancies. ACTH levels were undetectable or low in three patients in whom it was measured and who did not suppress with dexamethasone. Following CRH, the cortisol levels were highest (823 and 853 nmol l(-1)) in two of these patients. Malignancy is associated with diffuse enlargement of the adrenal glands and resistance to dexamethasone-induced suppression of the HPA axis, which is not due to ectopic ACTH secretion. This disturbance of the normal control of the HPA axis is unexplained and its functional significance remains uncertain.

Expression of opioid peptides in tumors

We looked for opioid peptides and their precursors in 108 tumors of both neuroendocrine and nonneuroendocrine origin, using a monoclonal "pan-opioid" antibody, 3-E7, which recognizes the tetrapeptide Tyr-Gly-Gly-Phe (the sequence responsible for pharmacologic activity in all known opioid peptides), in conjunction with polyclonal antibodies directed against representative peptides of each of the three precursors (alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B). Using the avidin-biotin immunoperoxidase technique, we observed consistent cytoplasmic immunoreactivity (at least focally) in all of 15 adrenal pheochromocytomas, all of 6 thyroid medullary carcinomas, and all of 5 pituitary adenomas. Opioid staining was also observed in parathyroid adenomas (8 of 9), pancreatic islet-cell tumors (7 of 10), carcinoid tumors from various sites (18 of 26), and paragangliomas (1 of 2). There was no immunoreactivity in pulmonary small-cell carcinomas, Merkel-cell tumors of skin, neuroblastomas, or any of the non-neuroendocrine tumors examined. The expression of alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B varied from tumor to tumor; however, positive staining with the "pan-opioid" antibody was found in each tumor containing at least one of the three precursors. Opioid peptide immunoreactivity was also detected in non-neoplastic cells of the adrenal medulla, pancreatic islets, pituitary, intestinal and bronchial mucosa, and intestinal myenteric plexuses. We conclude that opioid expression within tumors is most likely due to enhanced expression of a normal cell product and that opioid peptides are useful markers of neuroendocrine differentiation in many tumors.

Ectopic ACTH production by a thymic carcinoid tumour

An ACTH-producing thymic carcinoid tumour was diagnosed in a 10-year-old girl, 8 years after bilateral adrenalectomy for Cushing's syndrome. The peptides produced by the tumour were characterised thoroughly. High circulating levels of beta-endorphin and other peptides may have contributed to mood and behaviour disturbances.

Characterization of opioid peptides in human thyroid medullary carcinoma

A thyroid medullary carcinoma from a man with the multiple endocrine neoplasia syndrome Type IIB was examined for the presence of opioid peptides. The tumor contained peptides derived from all three opioid precursors: pro-opiomelanocortin (POMC), pro-dynorphin, and pro-enkephalin. The tissue concentrations of the various opioid peptides varied considerably. beta-Endorphin, a POMC-derived peptide, was present in concentrations between 9 to 12 pmoles/g tissue; 8 pmoles/g tissue of alpha-neo-endorphin, a pro-dynorphin-derived product, were seen, whereas the pro-enkephalin-associated peptides were present in much lower concentrations (0.6-2.1 pmoles/g tissue). Immunohistochemical studies showed scattered opioid-positive cells in the tumor tissue and in two other thyroid medullary carcinomas. These data demonstrate that malignant neuroendocrine tumors may contain peptides derived from all three families of the endogenous opioids.

Small cell carcinoma cell lines contain opioid peptides and receptors

Two human small cell carcinoma cell lines were assayed for total opioid and beta-endorphin-like immunoreactivity. Small cell carcinoma cell line NCI-H146 contained approximately 1.1 pmol/mg protein of total opioid immunoreactivity. This material was similar in size and immunoreactive determinants to C-terminally modified beta-endorphin. Small cell carcinoma cell line NCI-H187 contained approximately 0.2 pmol/mg protein total opioid immunoreactivity, which was of low molecular weight. NCI-H187 also contained approximately 1.2 pmol/mg protein of material similar in size and immunoreactive determinants to beta-lipotropin. The two small cell carcinoma cell lines were also examined for opioid receptors with the use of [3H]-etorphine as ligand. Both cell lines contained between 50 and 100 fmol/mg protein of specific, saturable, high-affinity opioid receptor binding sites. Together, these findings suggest a possible autocrine role for opioids in small cell carcinoma of the lung.

Altered proopiomelanocortin gene expression in adrenocorticotropin-producing nonpituitary tumors. Comparative studies with corticotropic adenomas and normal pituitaries

In order to assess the mechanisms of proopiomelanocortin (POMC) gene expression in human ACTH-producing tumors, we performed the simultaneous evaluation of POMC products and messenger RNA (mRNA) in tissue fragments obtained from two corticotropic adenomas, five nonpituitary tumors, and two normal human pituitaries. The POMC products were examined using a combination of gel exclusion chromatography and four different radioimmunoassays directed against gamma 3 melanocyte stimulating hormone (gamma 3MSH), ACTH, gamma-lipotropin (gamma LPH), and beta-endorphin. The POMCmRNA was detected and analyzed by dot and northern blot hybridization using a single-stranded genomic DNA probe corresponding to the coding region of the human POMC gene. Tissue concentrations of POMC products and mRNA showed parallel distributions. Immunoreactive gamma 3MSH and gamma LPH patterns revealed only 16-kD fragment- and gamma LPH-like peptides in normal and tumoral pituitaries; additional gamma 3MSH- and/or beta MSH-like peptides were found in all five nonpituitary tumors. A single POMCmRNA of approximately 1,200 bases (b) was detected in normal and tumoral pituitaries; a single identical POMCmRNA was also found in four nonpituitary tumors. A thymic carcinoid tumor, in addition to the 1,200-b POMCmRNA, contained equal amounts of a second larger POMCmRNA of approximately 1,450 b. It is concluded that POMC gene expression appears qualitatively unaltered in corticotropic adenomas. In nonpituitary tumors, in contrast, abnormal POMC processing is frequent; in addition, an extra POMCmRNA was detected in a thymic tumor with a greater length than the normal mRNA; the mechanisms and pathophysiological implications of these modifications remain to be elucidated.

Cushing's syndrome

Cushing's syndrome remains one of the most challenging problems in clinical endocrinology. Cushing's disease is caused in the majority of cases by basophil pituitary microadenomas which may be successfully treated by trans-sphenoidal hypophysectomy. Treatment with metyrapone or o,p'-DDD can always induce a clinical remission but not a cure, and neurotransmitter therapy may be effective in a minority of cases. Pituitary irradiation cures about half of cases in the long-term and may be used for surgical failures. Tumours producing ectopic ACTH are frequently benign, small and occult and may produce a syndrome clinically indistinguishable from Cushing's disease. Biochemical investigations cannot absolutely distinguish pituitary from ectopic sources of ACTH and therefore body CT scanning and percatheter venous sampling are essential diagnostic investigations. Tumour localization may result in resection and complete cure, although even small tumours may have a malignant potential. Adrenal tumours are readily diagnosed by plasma ACTH measurement and adrenal CT scanning. Adrenal adenomas are cured by adrenalectomy. Carcinomas may be treated by a combination of adrenalectomy, radiotherapy and o,p'-DDD, but long-term prognosis is poor.

Extrapulmonary oat-cell carcinoma of the tongue: an electron-microscopic study

An extrapulmonary oat-cell carcinoma arose in the tongue of a 62-year-old man who had a long history of cigarette smoking and ethanol ingestion. At presentation, he had the primary tongue lesion and cervical lymph-node metastases only, and search for a pulmonary primary was negative. Ten months later he died with metastases to liver, cerebrum, ribs, vertebrae, calvarium, and clavicle. Electron microscopy demonstrated cells with cytoplasmic processes and many dense-core neurosecretory granules that had a tendency to concentrate in the processes. Cells were linked by desmosomes. Electron microscopy is necessary for definitive diagnosis of extrapulmonary oat-cell carcinomas.

Opiate receptors: enkephalins and endorphins

Opiate receptors in the central nervous system may be classified according to pharmacological, behavioural, or binding studies. Classical mu-receptors probably have beta-endorphin as an endogenous ligand, and seem to be involved in the modulation of pain perception, low-frequency acupuncture analgesia, and the stimulation of prolactin, growth hormone and thyroid-stimulating hormone release. Met-enkephalin is likely to be an endogenous ligand for the delta-receptors, which predominate in the basal ganglia and limbic systems; such receptors may tonically inhibit the release of corticotrophin-releasing factor. It has been suggested that the newly-described kappa-receptors may inhibit the release of vasopressin and gonadotrophin-releasing factor; dynorphin may be their endogenous ligand. Endogenous opiates controlling cardiovascular and respiratory reflexes are likely to activate mu-receptors, while high-frequency acupuncture may alleviate the symptoms of opiate withdrawal by allowing an increase in Met-enkephalin to activate delta-receptors. In the periphery, beta-endorphin is concentrated in the corticotrophs of the anterior pituitary, and is cosecreted with ACTH and related peptides. Circulating Met-enkephalin originates in the gut, sympathetic nervous system and adrenal medulla. Met-enkephalin may also be extracted from carcinoid tumours and phaeochromocytomas. Elevations in circulating Met-enkephalin may occur in certain disease states with cardiovascular and psychiatric manifestations. However, manipulation of endogenous or exogenous opiates has as yet no certain place in any clinical situation.

Surgical management of the ectopic ACTH syndrome

Most patients with extra-pituitary ACTH-secreting tumors die from carcinoma, but a few can benefit from operation. Of 96 patients with Cushing's syndrome, 11 probably had such tumors. There were three modes of presentation: (1) three had malignant tumors with visceral metastases initially. One (bronchial carcinoid) died without operation. Two with carcinoma (thyroid medullary and islet-cell) underwent adrenalectomy with remission, but died soon. (2) three had apparently benign tumors initially. One (appendicular carcinoid) underwent appendectomy and one (bronchial carcinoid with hilar node metastases) underwent lobectomy. Both had rapid remissions. The third (pheochromocytoma) died after resection of the tumor. (3) five patients had no obvious tumors and underwent adrenalectomy with remission. In one a benign bronchial carcinoid was removed later. Four others remain well, but without localizing signs of tumor. The main biochemical features in all were hypokalemic alkalosis and very high urinary excretion of free cortisol. Seven of the eight patients without visceral metastases are in remission from one to 15 years after operation.

Circulating ACTH and related peptides in lung cancer

The prevalence of high levels of circulating ACTH-like immunoactivity was determined in 134 patients with lung cancer, using reference ranges from 52 age- and sex-matched patients with non-malignant lung disease. Two studies used ACTH radioimmunoassays with different specificities. Study A used an unextracted plasma or serum assay for total ACTH immunoactivity. High serum ACTH levels occurred in 24% of patients with small-cell carcinoma and 3% of patients with non-small-cell cancer. In patients with small-cell carcinoma, levels were high in 12% with limited disease and 32% with extensive disease. Study B used an ACTH assay after plasma extraction by porous glass, which measured mainly regular 1-39 ACTH. Here no lung-cancer patient had levels above the reference range, suggesting that the high levels in Study A may be due to plasma ACTH components which are poorly extracted by porous glass. It is concluded that high circulating ACTH immunoactivity occurs in a minority of patients with lung cancer, particularly those with extensive small-cell carcinoma. Indirect evidence suggests that the high ACTH levels detected with assays for total ACTH are due to molecular forms other than 1-39 ACTH, probably high-mol.-wt species.

Ectopic secretion of ACTH and met-enkephalin from a thymic carcinoid

A 51-year old man presented with the classical features of Cushing's syndrome which had evolved over the previous 5 yr, and was found to have ACTH secretion from an atypical thymic carcinoid tumor. Tumor extract, assayed under conditions designed to prevent artefactual generation of peptides, was found to contain a wide variety of immunoreactive hormones including ACTH, alpha-MSH, CLIP, beta-endorphin and met-enkephalin. The ACTH-related peptides were probably derived from a common precursor, pro-opiocortin, but the presence of met-enkephalin suggests the production of a separate type of precursor molecule. The tumor was locally invasive and, depsite subtotal excision and radiotherapy, continued to secrete large amounts of ACTH. Hypercortisolism was controlled longterm with pharmacological adrenal blockade and steroid replacement.