Hormones from tumors: are they ubiquitous?

Gastroenteropancreatic tumours and prohormones

The structures and post-translational maturation of pancreatic and gastrointestinal prohormones are reviewed with emphasis on Danish contributions to today's knowledge. The review describes general, cell-specific, and tumour-specific prohormone-processing patterns. Since prohormone-processing in endocrine tumours is often attenuated, conventional assays that measure only the phenotypic endpoint of hormone gene expression (i.e. the bioactive hormone) do not quantitate tumour activity accurately. In contrast, measurements that include also prohormones and processing intermediates provide more accurate data on hormone synthesis in gastroenteropancreatic endocrine tumours. In order to comply with such demands we have developed a new analytical principle (processing-independent analysis (PIA)) which quantitates the entire translation product irrespective of the degree of processing. The significance of PIA in routine diagnostics awaits prospective evaluation. We hope that the present review illustrates how the tumour biology of endocrine cells in the pancreas and the gut has been an essential research area in Danish gastroenterology and endocrinology--one purpose being improvement of early diagnosis of endocrine tumours in the gut and the pancreas.

Immunohistochemical characterization of endocrine cells in experimental exocrine pancreatic cancer in the Syrian golden hamster

Fifty exocrine pancreatic adenocarcinomas and 57 benign tumors induced in Syrian hamsters by N-nitrosobis(2-oxopropyl)amine (BOP) were examined for the presence of argyrophil cells antiinsulin, -glucagon, -somatostatin, -pancreatic polypeptide (PP), -gastrin/CCK, -vasoactive intestinal polypeptide (VIP), and - neuron-specific enolase (NSE) reactive cells. Argyrophil - and antihormone-reactive cells were found in the normal pancreatic ducts and in the acini, as well as in hyperplastic and atypical ducts/ductules, tubular complexes, benign lesions, and in 80% of ductal adenocarcinomas. Insulin and antiNSE-reactive cells were the most common, followed in decreasing frequency by glucagon, somatostatin, and PP cells. Antigastrin-/CCK-and -VIP-reactive cells were found in two cases. Argyrophil cells were present in about 60% of the tumors with Grimelius staining and in 55% of those with Churukian-Schenk staining. Insulin cells were seen in ductal cancer that had grown into a lymph node and in the lymph node metastases of another cancer. A novel finding was the presence of argyrophil and insulin cells within the lumen of some malignant glandular structures. Coexistence of several peptide cells was found in 52% of the cancers. The presence of argyrophil and hormone-producing cells in induced pancreatic ductal/ductular lesions further strengthens the existence of a close developmental relationship between exocrine and endocrine cells of the pancreas.

The expression of peptide hormones in normal cells and tumour cells

Insight in the mechanisms of peptide hormone expression has grown explosively by elucidation of gene, mRNA and preprohormone structures for most hormone systems during the 1980s. In addition, information about the structure and substrate specificity of many prohormone processing enzymes is rapidly accumulating in these years. The preprohormones vary considerably in size and organization from poly- to monoprotein structures. According to the structural organization and sequence homology the hormones are grouped in families. The prohormones are processed to bioactive peptides by multiple enzymatic modifications during the intracellular transport from the rough endoplasmatic reticulum to the mature secretory granules. The modifications comprise different proteolytic cleavages and amino acid derivatizations. The same prohormone may be expressed in several different cell types that process the precursor in entirely different ways. Awareness of such cell-specific processing patterns is important for the understanding of ectopic synthesis in neuroendocrine tumours.

Gastrin, cholecystokinin and their precursors in acoustic neuromas

Using sequence-specific radioimmunoassays the occurrence of 4 neuropeptides (cholecystokinin (CCK), gastrin, somatostatin, substance P and some of their precursors) was examined in 19 human acoustic nerve tumors and corresponding normal tissue. The normal acoustic nerve tissue obtained by autopsy contained traces of CCK, somatostatin, and substance P (less than or equal to 0.5 pmol/g), but neither proCCK, gastrin nor progastrin. In contrast 8 tumors expressed proCCK (range 0.2-4.5 pmol/g), 3 tumors gastrin (0.1-7.3 pmol/g) and 14 tumors progastrin (0.6-2.2 pmol/g). Traces of somatostatin were present in two and substance P in one tumor. The results show that acoustic neuromas often express the homologous CCK and gastrin genes, but process their propeptides poorly to transmitter-active peptides. The tumor synthesis of gastrin/progastrin contrasts to the rare, sporadic expression of the gastrin gene in normal nerve tissue.

Paraneoplastic syndromes

A given cancer is a disease which combines a paraneoplastic syndrome with an invasive tumour capable of giving rise to metastases. Surgeons, radiotherapists, medical oncologists and experimental scientists are primarily interested in the tumour. Tumours of tissues and organs which do not normally produce hormones might, during the neoplastic transformation, begin to secrete hormones or substances able to mimic hormones in their effects on other tissues in the organism. The number of known hormones has increased considerably in the last 20 years. It has been found that even in the absence of clinical signs there are often secretory abnormalities and changes in the hormone balance in cancer. The tumour-paraneoplastic syndrome interaction is bidirectional. That paraneoplastic syndromes are dependent upon the tumour, is universally accepted; the reverse, that the tumour might depend on the paraneoplastic syndrome is not part of the current way of thinking. To treat cancer patients, instead of debating the cause and effect in the tumour-paraneoplastic syndrome pair with the classical idea of acting as close to the cause as possible, it seems better, in all circumstances, to treat both the tumour and the paraneoplastic syndrome, even if only subclinical.

Opioid-like immunoreactants in human cervical cancer

Cervical carcinoma cell lines produce several polypeptide hormones. While screening human cervical cancers for such factors we have found many tumors to be immunoreactive for opioid peptides. The tumors were collected at surgery or prior to actinotherapy, fixed in buffered formalin, paraffin-embedded, and immunocytochemically stained using the PAP method. The localization of opioid-like immunoreactivity was investigated using a primary antiserum recognizing the Tyr-Gly-Gly-Phe sequence common to all known opioid peptides. The presence of neuropeptide Y (NPY) and peptide histidine methionine (PHM), both known to be present in normal human cervical tissue, was also investigated using specific antisera. Controls included staining controls and absorption controls, using Sepharose-coupled antigen and were all negative. Out of 40 cervical carcinomas, 27 displayed varying numbers of opioid-immunoreactive cells. In 12 normal cervical specimens no specific staining was observed. None of the tumors displayed any NPY-like or PHM-like immunoreactivity. The growth of cervical carcinoma seems therefore to be accompanied by a destruction of the local peptidergic innervation of blood vessels and smooth muscle cells. The demonstration of opioid-like immunoreactants and the known immunoregulatory properties of these peptides, indicate that opioid peptides may be important in the regulation of growth of human cervical carcinoma.

Tumors secreting human TNF/cachectin induce cachexia in mice

Anorexia and weight loss are serious complications that adversely effect the prognosis of cancer patients. It has been suggested that TNF/cachectin may cause cachexia. To determine if TNF/cachectin can induce progressive weight loss in tumor-bearing animals, a clone of the human TNF/cachectin gene was isolated and inserted into a mammalian expression vector. This construct was transfected into CHO cells, and a cell line (CHO/TNF-20) that secretes TNF/cachectin was isolated. A cell line (CHO/CMV-Neo) that contains the same expression vector without the TNF/cachectin gene was also isolated. Nude mice injected intraperitoneally with CHO/TNF-20 cells died more quickly than mice injected with CHO/CMV-Neo cells. Eighty-seven percent of mice inoculated intramuscularly with CHO/TNF-20 cells developed severe cachexia and weight loss. All mice bearing CHO/CMV-Neo tumors maintained or increased their body weight. We conclude that mice bearing tumors that secrete TNF/cachectin develop progressive wasting and die more quickly than mice bearing control tumors.

Tumor markers in bronchogenic carcinoma. Superiority of tissue polypeptide antigen to carcinoembryonic antigen and carbohydrate antigenic determinant 19-9

One hundred six patients with histologically proven bronchogenic carcinoma were tested for carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA), and carbohydrate antigenic determinant 19-9 (CA19-9). A total of 349 CEAs, 350 TPAs, and 317 CA19-9s were measured. In addition, sera were assayed from 57 patients with pulmonary benign diseases and their CEA, TPA, and CA19-9 levels were used as negative controls for specificity and accuracy. One hundred twenty healthy subjects provided our normal CA19-9 reference value. Sensitivity, specificity, and accuracy were obtained for CEA, TPA, and CA19-9, respectively. Significant intermarker correlations were found both at diagnosis and during follow-up, CEA and CA19-9 being the most closely related substances. The percentage of patients with elevated levels of TPA increased significantly according to tumor load. Individual values of TPA related significantly to the stage of disease. Concentrations of CEA, TPA, and CA19-9 varied significantly during the course of the illness in relation to treatment response; however, TPA showed the closest relationship to the clinical status assessments of the follow-up period. Abnormal pretreatment levels of TPA were significantly associated with a poor outcome. Biomarker combinations were clinically evaluated by calculating the mean of the percentage of the reference value for each combined marker. Using this method, any association of TPA with CEA and/or CA19-9 revealed neither a greater diagnostic accuracy nor a more reliable predictive capacity for the above clinical variables than TPA evaluated on its own. The authors believe that a single TPA assay should be added to the initial and subsequent clinical assessments of patients with bronchogenic carcinoma.

Cushing's syndrome due to ectopic proopiomelanocortin gene expression by islet cell carcinoma of the pancreas

Expression of proopiomelanocortin (POMC) was studied in a male patient with Cushing's syndrome and ectopic production of ACTH by a pancreatic carcinoma. Plasma ACTH levels (greater than 200 pg/ml) were elevated, and elevated serum cortisol and urinary free cortisol were partially suppressed to 25% of basal levels by high-dose dexamethasone. Petrosal and jugular vein sampling did not yield a gradient of ACTH. Immunohistochemical staining of tumor tissue removed at pancreatectomy was positive for ACTH and beta endorphin, and negative for corticotropin-releasing factor (CRF). Tumor cells cultured in vitro secreted ACTH and beta-endorphin, which comigrated with their respective radiolabeled standards on gel chromatography. Hydrocortisone suppressed in vitro ACTH secretion and CRF (100 nM) stimulated ACTH by 50% during 72 hours of incubation. Agarose gel electrophoresis of poly-(A) mRNA extracts of tumor tissue followed by hybridization with 32P-cDNA for POMC revealed 2 distinct RNA species. The major RNA species (about 1.0 kb) was smaller than authentic pituitary POMC mRNA (about 1.1 kb); a larger precursor band also was visualized, suggesting either processing or degradation of tumor-POMC mRNA. Cytoplasmic dot blot hybridization of tumor mRNA with POMC cDNA yielded a positive signal with increasing amounts of RNA blotted. Immunohistochemistry and radioimmunoassay (RIA) of ACTH, in vitro regulation of ACTH secretion, and expression of POMC mRNA species by this tumor document expression of the human POMC gene by an islet carcinoma associated with Cushing's syndrome.

Elevated beta-human chorionic gonadotropin and a search for cancer

Elevated human chorionic gonadotropin levels may be an early, and occasionally the only, manifestation of embryonal cell carcinoma. A 24-year-old man presented with gynecomastia, galactorrhea, and elevated beta-human chorionic gonadotropin levels, which led to an extensive (but nonrevealing) search, including computed tomography and selective testicular vein catheterization, for malignancy. Since the testicle was considered as the most likely site of tumor, right orchiectomy and right common iliac lymph node biopsy were performed. The testicle was normal, but the lymph node contained elements of embryonal and choriocarcinoma. Following chemotherapy, beta-human chorionic gonadotropin levels were normalized and the patient appears "cured." This case emphasizes the need for an extensive search for malignancy and consideration of orchiectomy in such instances in order to achieve a favorable outcome.

Pathophysiology of malnutrition in the adult cancer patient

A number of common metastatic cancers are associated with marked weight loss at the time of diagnosis. Cancer patients with weight loss at the time of diagnosis have decreased mean survival compared to similar cancer patients without weight loss. Provision of excess calories alone does not appear to change median survival in patients with advanced cancer and many patients either maintain body weight or lose weight while receiving calories which would be predicted to result in weight gain. The authors recently have extended their studies to head and neck cancer patients without detectable metastatic disease in order to detect systemic metabolic effects of a localized tumor. These patients failed to gain weight despite the administration of apparently adequate calories by continuous enteral alimentation. Abnormalities of carbohydrate metabolism with secondary effects on fat and protein metabolism have been identified in several populations of patients with common cancers. These abnormalities offer potential points of intervention which may enhance nutritional therapy as rehabilitation and as a potential biological modifier of the response of specific cancers to chemotherapy, radiation therapy, or surgery.

Fat metabolism and cancer

Progressive weight loss and anorexia are frequent phenomena in cancer patients. Although cachexia is an expected occurrence in the terminal stages of nearly all malignancies, it may be a presenting sign when the tumor burden is quite small. Lipid depletion occurs out of proportion to the protein loss and accounts for most of the weight loss in cancer. Lipids, more specifically fatty acids, are the major source of fuel in mammals and may also be used in the synthesis of new cell products. Lipolysis and lipogenesis are under the influence of several important enzymes and peptide hormones that may be modulated by a variety of exogenous factors. There is evidence that cancer patients have lost the normal homeostatic responses to decreased energy intake or starvation that allow a decrease in oxygen consumption and protein sparing. An increase in Cori cycle activity or futile recycling of metabolic products occurs with a net energy expenditure rather than energy production. Clinical studies have shown that the body lipid depletion accompanying tumor progression is not solely secondary to decreased food intake and may be reproduced by the transplantation of certain noninvasive tumors to normal hosts. Elevated basal lipolysis has occasionally been seen early in tumor growth. Such findings suggest the presence of a tumor-associated factor responsible for this increase in lipid mobilization. Some of the potential mechanisms for the altered lipid metabolism seen in cancer have been discussed. Metabolic substrates may be remodeled and directed away from fuel-efficient into energy-requiring pathways. An increased energy expenditure may occur as a result of the energy costs of tumor synthesis, an uncoupling of oxidative phosphorylation, or energy-requiring futile cycling. An overall depletion of lipid may be the final outcome of the inhibition of lipid deposition. TNF/cachectin has recently been found to suppress the activity and synthesis of several key lipogenic enzymes, including lipoprotein lipase. Abnormalities in insulin secretion or sensitivity may be involved in the decrease of fat storage in malignancy. Insulin also exerts a significant antilipolytic effect by its antagonism of hormone-sensitive lipase. Mediators of lipolysis and abnormal lipid metabolism may occur in a number of clinical conditions and include ectopic hormone production, growth factors, and tumor-associated lipolytic factors (lipid mobilizing factor, toxohormone).

Rheumatologic manifestations of cancer

A variety of musculoskeletal syndromes have been described in association with malignancy. The majority of such descriptions have dealt with the connective tissue disorder as a paraneoplastic syndrome, frequently the presenting feature of an otherwise occult malignancy. This may range from the well known syndrome of HOA, heralding lung cancer, to a lesser known association of pyogenic arthritis due to an unusual enteric pathogen, signaling colon cancer. Conversely, the connective tissue disorder may precede the malignancy, and by virtue of its pathophysiology or its therapy, foster the subsequent development of cancer. Awareness of these associations may lead to earlier cancer detection, and hence, potentially more effective therapy.

Nonmetastatic bladder cancer associated with hypercalcemia, thrombocytosis and leukemoid reaction

We reviewed 4 patients with urothelial bladder cancer and hypercalcemia but without evidence of bony metastasis. Of the patients 2 presented with a leukemoid reaction (1 also had thrombocytosis). None of the patients had evidence of bone metastases or other causes of hypercalcemia, such as hyperparathyroidism, sarcoidosis or vitamin D intoxication. All 4 patients received aggressive therapy for the tumors. In each instance the serum calcium returned to normal following radiation therapy or tumor removal, lending support to the theory of humoral hypercalcemia of cancer. A diagnostic and therapeutic approach to such patients is outlined.

Shaping future strategies for the pharmacological control of tumor cell metastases

The eradication of established metastases in patients with malignant tumors is the single most important objective in clinical oncology. The current panel of antineoplastic agents discovered through random and semiempirical screening procedures has proven largely ineffective in treating disseminated disease and there is a clear and urgent need for more efficient antimetastatic drugs. Unfortunately, although progress has been made in examining the biology of metastatic spread, our understanding of the pharmacology, biochemistry and molecular genetics of this process is meager and insufficient to provide a rational foundation for the design of mechanism-based antineoplastic agents. Faced on the one hand with the failure of existing drugs to control metastatic spread and on the other with a dearth of alternative pharmacological approaches, the prospect of offering significantly improved therapy to the cancer patient of the 1990's is poor. The challenge of the coming decade lies in obtaining better insights into the molecular mechanisms of metastasis and using this information to identify pharmacological opportunities to curtail the proliferation of secondary tumor growths. As a first step toward this goal we need to define more rigorously what constitutes a therapeutic target in malignant disease and what steps in the pathogenesis of cancer metastasis represent the gravest risk to the patient and thus are most eligible for direct pharmacological intervention. In addressing these issues and developing future strategies for antimetastatic drugs, Paget's 100 year-old 'seed and soil' hypothesis continues to offer a useful conceptual framework for analysis of metastatic behavior. Although Paget's proposal has been validated by a century of clinical observation, efforts to define the 'seed and soil' theory in molecular terms have not been attempted. With the advent of more efficient methodologies for culturing human normal and neoplastic cells coupled with the availability of microanalytical technologies it now becomes possible to investigate and identify the complementary biochemical components of the tumor cell 'seed' and organ 'soil' that combine to encourage the proliferation of metastases. With this information the design of specific pharmacological strategies to uncouple the 'seed and soil' relationship may emerge as a potential therapeutic approach for antagonizing the growth of disseminated malignant tumors.

Methylation patterns in the gene for the alpha subunit of chorionic gonadotropin are inherited with variable fidelity in clonal lineages of human fibroblasts

Cytosine methylation in DNA of an endogenous single-copy gene locus, the alpha-subunit of human chorionic gonadotropin (alpha-hCG), was assessed in a mass culture and individual clonal lineages of human diploid fibroblasts. Progressive hypomethylation at -CCGG- sites in this gene occurred during the replicative lifespan of the mass culture and was shown to arise randomly during clonal expansion. Thus, some clones and subclones lost -CCGG- methylation in the alpha-hCG gene region while others maintained essentially complete methylation. These data indicate significant interclonal variability in the fidelity with which DNA methylation is transmitted in an endogenous gene.

Biologically active chorionic gonadotropin: synthesis by the human fetus

The kidney, and to a slight extent the liver, of human fetuses were found to synthesize and secrete the alpha subunit common to glycoprotein hormones. Fetal lung and muscle did not synthesize this protein. Since fetal kidney and liver were previously found to synthesize beta chorionic gonadotropin, their ability to synthesize bioactive chorionic gonadotropin was also determined. The newly synthesized hormone bound to mouse Leydig cells and elicited a biological response: namely, the synthesis of testosterone. These results suggest that the human fetus may participate in metabolic homeostasis during its development.

Human chorionic gonadotropin immunoreactivity in serum of patients with malignant neoplasms

The beta-human chorionic gonadotropin (HCG) radioimmunoassay was used to determine the presence of HCG immunoreactivity in serum of patients (n = 71) with diagnosis of cancer. Of patients with active neoplasia, 60.5% showed HCG immunoactivity above controls (greater than 5 mIU/ml). An apparent degree of correlation was observed with tumor activity in that a case with widespread metastases due to a colonic carcinoma exhibited the highest HCG levels while, in one patient, the level of HCG decreased progressively according to therapeutic response. A high frequency of immunoactive HCG was found in patients with carcinomas of the cervix, breast, gonad, and digestive system and in patients with melanoma. Trophoblastic cells were not evident in the tumors biopsied. Immunologic similarity of HCG secreted by tumors and that contained in serum of pregnant women, of patients with hydatidiform mole, and of males injected with exogenous HCG was shown by parallel inhibition curves in the radioimmunoassay. The positivity of HCG was predominant in cases of cervix carcinoma.

High levels of intracellular bombesin characterize human small-cell lung carcinoma

"Small cells" or "oat cells" characterize a virulent form of lung cancer and share many biochemical properties with peptide-secreting neurones. The neuropeptide bombesin is present in all small-cell lines examined, but not in other lung cancer cell lines, suggesting that bombesinergic precursor cells in lung may give rise to this disease.