Wachstumsbeeinflussende Hormone und Tumorwachstum

The history of circadian rhythm research in Austria

In view of the recent revival of interest in circadian biology and circadian epidemiology at the Medical University of Vienna, it seems appropriate to highlight the rich and pioneering history of circadian research in Austria. Among the forefathers of circadian research in Vienna are Otto Marburg (1874-1948), who discovered important elements of the pineal gland physiology, Robert Hofstätter (1883-1970), who used pineal gland extract in obstetrics/gynecology, and Paul Engel (1907-1997), who discovered that the pineal gland was controlled by light. More recently, Vera Lapin (1920-2007) showed that surgical removal of the pineal gland increased tumor growth, while Franz Waldhauser (*1946) investigated melatonin in conjunction with night work. Michael Kundi (*1950) and his team conducted among the first studies demonstrating differences in rhythms of night workers and early evidence for health impairments among them. Furthermore, Vienna-born Erhard Haus (1926-2013) pioneered the discovery of the role and importance of melatonin in relation to numerous diseases. This rich pioneering contribution of scientists in Vienna or with roots in Vienna is continued today by a new generation of chronobiologists, epidemiologists and clinicians in Vienna whose new insights contribute to the rapidly developing field of circadian rhythms research. Current topics and contributions relate to the impact of circadian rhythm disruption on health, and the application of chronotherapeutic approaches in clinical and preventive settings.

The Anti-tumor Activity of Pineal Melatonin and Cancer Enhancing Life Styles in Industrialized Societies

This review discusses the potential role of the anti-tumor activity of pineal melatonin for the aetiology and prevention of cancers related to life-styles in industrialized societies, e.g. frequent long-distance flights as well as chronic night shift work leading to circadian disturbances of neuroendocrine parameters including melatonin. Experimental studies show that melatonin controls not only the growth of well-differentiated cancers, but also possesses anti-carcinogenic properties. Therefore, it is plausible that disturbances of circadian melatonin rhythmicity could be functionally involved in elevated cancer risks among aircrew members and nurses frequently working on night shifts. Due to the suppression of melatonin by light it can be assumed that too much artificial light at night could, at least in part, be responsible for generally increasing rates of e.g. breast cancer in industrialized countries. It is discussed under which conditions a transient substitutional therapy with melatonin could be justified or which forms of living could help to physiologically foster melatonin secretion to optimise control over cancerous growth and development.

Melatonin in cancer patients and in tumor-bearing animals

A review of findings is given which relate to the levels of circulating melatonin as well as the urinary excretion of its main peripheral metabolite 6-sulphatoxymelatonin (aMT6s) in patients with different types of cancer as well as in tumor-bearing animals. Clinical results show that circulating melatonin tends to be depressed in patients with primary tumors of different histological types including both endocrine-dependent (mammary, endometrial, prostate cancer) and endocrine-independent tumors (lung, gastric, colorectal cancer). Reduction of melatonin is most pronounced in patients with advanced localized primary tumors, such as mammary and prostate cancer where a clear negative correlation with tumor-size exists. The phenomenon of a reduction of circulating melatonin appears to be a transient one since patients with recidives show a normalization of melatonin. Surgical removal of the primary tumor does, however, not lead to normalization indicating that complex systemic changes appear to be involved in the down-regulation of melatonin. It is unclear at present, whether circulating melatonin is depleted in cancer patients due to a reduced production by the pineal gland or due to certain peripheral metabolic processes, although no evidence for an enhanced hepatic degradation to aMT6s, the main peripheral metabolite of melatonin, was found. The reduction of circulating melatonin is accompanied by neuroendocrine changes affecting the circadian secretion of the adenohypophyseal hormones prolactin, somatotropin and thyroid-stimulating hormone. In contrast to the above-described types of tumors many patients with ovarian cancer show highly elevated levels of melatonin perhaps due to the production of tissue-specific growth factors that could affect pineal melatonin secretion. Experiments with tumor-bearing animals clearly demonstrate that nocturnal circulating melatonin is modulated due to malignant growth. Detailed investigations with chemically induced mammary tumors in rats and serial transplants derived thereof show that slow-growing and well-differentiated tumors containing epithelial cell elements (adenocarcinomas and carcinosarcomas) lead to an enhanced production of melatonin involving activation of the rate-limiting enzyme of pineal melatonin biosynthesis (serotonin N-acetyltransferase) probably due to elevation of the sympathetic tone in response to a stimulation of the cellular immune system by malignant growth. As opposed to that nocturnal melatonin is depleted in animals with fast-growing mammary tumor transplants when myoepithelial-mesenchymal conversion leads to pure sarcomas. The reduction of melatonin appears to be due to either a reduced availability of the precursor amino acid tryptophan because of a glucocorticoid-induced activation of the hepatic enzyme tryptophan 2,3-dioxygenase or a direct peripheral degradation of melatonin via indoleamine 2,3-dioxygenase expressed in tumor and/or other tissues. The significance of these clinical and experimental findings relating to melatonin is discussed both in terms of their practical application as a possible tumor marker and from a theoretical point of view to understand better the mechanisms involved in complex host-tumor interactions involving the neuroimmunoendocrine network.

Melatonin decreases bone marrow and lymphatic toxicity of adriamycin in mice bearing TLX5 lymphoma

When CBA male mice bearing TLX5 lymphoma were treated in the evening with a single i.v. dose of adriamycin (20-40 mg/Kg), the administration of a single pharmacological dose of melatonin (10 mg/kg s.c.) 1 hr earlier reduced the acute mortality from 10/24 to 2/24. The increase in survival time caused by adriamycin over drug untreated controls was not reduced by melatonin. The administration of melatonin alone did not cause any antitumor or evident toxic effect. Melatonin also attenuated the reduction caused by adriamycin in the number of bone marrow GM-CFU, and of CD3+, CD4+ and CD8+ splenic T-lymphocyte subsets. Reduced and total glutathione levels were decreased in the bone marrow and in the liver cells of the animals treated with adriamycin, and were significantly restored by melatonin. Moreover, lipid peroxidation by adriamycin was reduced by melatonin, as indicated by malondialdehyde measurement in the liver of the treated animals. These data indicate that the protective effects of melatonin against the host toxicity of the prooxidant antitumor drug, adriamycin, might be attributed at least partially to its antioxidant properties. These findings appear of interest in relation to the physiological rhythmic levels of endogenous melatonin and to the chronotoxicology of anthracyclines.

Urinary melatonin levels in human breast cancer patients

Urinary melatonin levels were measured in 10 postmenopausal Indian women suffering from advanced stages of breast cancer and in 9 well-matched women with non-endocrine complaints, mostly uterovaginal prolapse. Urines of each patient were collected over a period of 2-3 days in four 4-hourly intervals from 6 a.m. to 10 p.m. and one 8-hourly interval from 10 p.m. to 6 a.m. Serum LH, FSH, prolactin, estradiol and cortisol levels at 11 a.m. were determined as well as estrogen and progesterone receptors of the breast tumors. It was found that 24 hour urinary melatonin excretion in cancer patients was on the average 31% decreased as compared to the controls. This change was accompanied by a 33% increase in serum cortisol levels in the cancer patients. The melatonin excretion patterns of the cancer patients were not synchronized as compared to synchronized patterns of the controls. The number of tumors tested for steroid receptors does not yet allow to conclude if melatonin is different in patients with or without hormone-dependent tumors. The data suggest that pineal melatonin secretion may be modified in quantity as well as rhythmicity in breast cancer patients.

The role of the pineal gland in neuroendocrine control mechanisms of neoplastic growth

A survey of papers read during a workshop held in Vienna, 1977, is given showing that the pineal gland can be considered a model for research on neuroendocrine control mechanisms in neoplastic growth. From data obtained by different authors it can be concluded that the role of the pineal indole melatonin is very important in regard of the incidence and the development of tumours. On the basis of all the facts mentioned in this paper it is obvious that pineal gland activity should be included into the neuroendocrine factors studied in relation with oncogenic processes. For future research a number of experimental approaches, which need special emphasis, are recommended.

Pineal effects on metabolism and glucose homeostasis: evidence for lines of humoral mediation of pineal influences on tumor growth

Results from animal experiments support the hypothesis that pineal gland function can influence some aspects of tissue metabolism and glucose homeostasis. Evidence of pineal effects on particular endocrine and sympatheto-adrenal targets contributes to an understanding of indirect routes by which pineal activity can possibly affect the growth and activity of some kinds of tumors, in part through nutrient and metabolic effects in the tissue environment of the tumor cells.