Melatonin: from basic research to cancer treatment clinics

Melatonin

Melatonin is a ubiquitous molecule and widely distributed in nature, with functional activity occurring in unicellular organisms, plants, fungi and animals. In most vertebrates, including humans, melatonin is synthesized primarily in the pineal gland and is regulated by the environmental light/dark cycle via the suprachiasmatic nucleus. Pinealocytes function as 'neuroendocrine transducers' to secrete melatonin during the dark phase of the light/dark cycle and, consequently, melatonin is often called the 'hormone of darkness'. Melatonin is principally secreted at night and is centrally involved in sleep regulation, as well as in a number of other cyclical bodily activities. Melatonin is exclusively involved in signaling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. Synthesis of melatonin also occurs in other areas of the body, including the retina, the gastrointestinal tract, skin, bone marrow and in lymphocytes, from which it may influence other physiological functions through paracrine signaling. Melatonin has also been extracted from the seeds and leaves of a number of plants and its concentration in some of this material is several orders of magnitude higher than its night-time plasma value in humans. Melatonin participates in diverse physiological functions. In addition to its timekeeping functions, melatonin is an effective antioxidant which scavenges free radicals and up-regulates several antioxidant enzymes. It also has a strong antiapoptotic signaling function, an effect which it exerts even during ischemia. Melatonin's cytoprotective properties have practical implications in the treatment of neurodegenerative diseases. Melatonin also has immune-enhancing and oncostatic properties. Its 'chronobiotic' properties have been shown to have value in treating various circadian rhythm sleep disorders, such as jet lag or shift-work sleep disorder. Melatonin acting as an 'internal sleep facilitator' promotes sleep, and melatonin's sleep-facilitating properties have been found to be useful for treating insomnia symptoms in elderly and depressive patients. A recently introduced melatonin analog, agomelatine, is also efficient for the treatment of major depressive disorder and bipolar affective disorder. Melatonin's role as a 'photoperiodic molecule' in seasonal reproduction has been established in photoperiodic species, although its regulatory influence in humans remains under investigation. Taken together, this evidence implicates melatonin in a broad range of effects with a significant regulatory influence over many of the body's physiological functions.

The role of melatonin in immuno-enhancement: potential application in cancer

Melatonin, a neurohormone produced mainly by the pineal gland, is a modulator of haemopoiesis and of immune cell production and function, both in vivo and in vitro. Physiologically, melatonin is associated with T-helper 1 (Th1) cytokines, and its administration favours Th1 priming. In both normal and leukaemic mice, melatonin administration results in quantitative and functional enhancement of natural killer (NK) cells, whose role is to mediate defenses against virus-infected and cancer cells. Melatonin appears to regulate cell dynamics, including the proliferative and maturational stages of virtually all haemopoietic and immune cells lineages involved in host defense - not only NK cells but also T and B lymphocytes, granulocytes and monocytes - in both bone marrow and tissues. In particular, melatonin is a powerful antiapoptotic signal promoting the survival of normal granulocytes and B lymphocytes. In mice bearing mid-stage leukaemia, daily administration of melatonin results in a survival index of 30-40% vs. 0% in untreated mice. Thus, melatonin seems to have a fundamental role as a system regulator in haemopoiesis and immuno-enhancement, appears to be closely involved in several fundamental aspects of host defense and has the potential to be useful as an adjuvant tumour immunotherapeutic agent.

Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in advanced non-small-cell lung cancer patients with low performance status

BACKGROUND

The prognosis of low performance status (PS) patients with advanced non-small-cell-lung cancer (NSCLC) is dismal. In these patients, we have determined the survival, clinical benefits, and toxicity of a multidrug regimen, based on cyclophosphamide and biotherapeutical agents.

METHODS

Patients with a diagnosis of stage IIIB or stage IV NSCLC, no previous surgery or chemoradiotherapy, and an Eastern Cooperative Oncology Group (ECOG) PS equal to or greater than 2 received a daily combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide.

RESULTS

Twenty-eight (28) patients were enrolled. The median age was 64 years (range, 35-74). The PS was 2 and 3 in 78.6% and 21.4% of patients, respectively. The median overall survival (intent-to-treat analysis) was 12.9 months (range, 1.5-33.5 months), The overall survival rates at 1 and 2 years were 51.2% and 21.1%, respectively. The side-effects were very mild, mostly consisting of diarrhoea, nausea/vomiting, and drowsiness of grade 1-2. Most patients experienced an improvement of both respiratory (cough and dyspnoea) and general (pain, fatigue, and insomnia) symptoms.

CONCLUSIONS

Low PS patients with advanced NSCLC may benefit from a combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide, in terms of survival and quality of life, with very low side-effects.

Circulating Melatonin Levels: Possible Link Between Parkinson’s Disease and Cancer Risk?

Lower rates of cancer mortality/incidence in patients with Parkinson's disease (PD) have given rise to speculations about risk or preventative factors common to both diseases, including life-style factors (such as smoking) and genetic susceptibility. Melatonin, a hormone known for its sleep regulatory effects, may play an important role in carcinogenesis as suggested by substantial laboratory and less direct epidemiologic evidence. Particularly, a reduction in melatonin, such as experienced by persons who are exposed to light at night, appears to increase cancer risk. Variations in melatonin levels have been linked to PD in several different ways. Some studies show higher morning melatonin levels in PD patients than in healthy controls. One could speculate that the sleep disorders that affect almost two thirds of those suffering from PD and can precede PD motor symptoms by several years may be associated with variations in melatonin levels. Moreover, in animal models, interventions that increase the bioavailability of melatonin appears to increase the severity of parkinsonian symptoms, whereas reduction in melatonin by pinealectomy or exposure to bright light can enhance recovery from parkinsonisms symptoms. Finally, preliminary epidemiological evidence suggests that longer years of working night shifts is associated with a reduced risk of PD among participants of the Nurses' Health Study (NHS), whereas longer hours of sleep appear to increase their risk. In sum, while lower melatonin concentrations may predict a higher cancer risk, there is also some evidence that they may be associated with a lower risk of PD. We therefore hypothesize that elevated circulating melatonin levels in PD patients may contribute to their lower cancer rates.

Melatonin as antioxidant, geroprotector and anticarcinogen

The effect of the pineal indole hormone melatonin on the life span of mice, rats and fruit flies has been studied using various approaches. It has been observed that in female CBA, SHR, SAM and transgenic HER-2/neu mice long-term administration of melatonin was followed by an increase in the mean life span. In rats, melatonin treatment increased survival of male and female rats. In D. melanogaster, supplementation of melatonin to nutrient medium during developmental stages produced contradictory results, but and increase in the longevity of fruit flies has been observed when melatonin was added to food throughout the life span. In mice and rats, melatonin is a potent antioxidant both in vitro and in vivo. Melatonin alone turned out neither toxic nor mutagenic in the Ames test and revealed clastogenic activity at high concentration in the COMET assay. Melatonin has inhibited mutagenesis and clastogenic effect of a number of indirect chemical mutagens. Melatonin inhibits the development of spontaneous and 7-12-dimethlbenz(a)anthracene (DMBA)- or N-nitrosomethylurea-induced mammary carcinogenesis in rodents; colon carcinogenesis induced by 1,2-dimethylhydrazine in rats, N-diethylnitrosamine-induced hepatocarcinogenesis in rats, DMBA-induced carcinogenesis of the uterine cervix and vagina in mice; benzo(a)pyrene-induced soft tissue carcinogenesis and lung carcinogenesis induced by urethan in mice. To identify molecular events regulated by melatonin, gene expression profiles were studied in the heart and brain of melatonin-treated CBA mice using cDNA gene expression arrays (15,247 and 16,897 cDNA clone sets, respectively). It was shown that genes controlling the cell cycle, cell/organism defense, protein expression and transport are the primary effectors for melatonin. Melatonin also increased the expression of some mitochondrial genes (16S, cytochrome c oxidases 1 and 3 (COX1 and COX3), and NADH dehydrogenases 1 and 4 (ND1 and ND4)), which agrees with its ability to inhibit free radical processes. Of great interest is the effect of melatonin upon the expression of a large number of genes related to calcium exchange, such as Cul5, Dcamkl1 and Kcnn4; a significant effect of melatonin on the expression of some oncogenesis-related genes was also detected. Thus, we believe that melatonin may be used for the prevention of premature aging and carcinogenesis.

Urinary 6-sulfatoxymelatonin levels and their correlations with lifestyle factors and steroid hormone levels

Exposure to light at night, as experienced by rotating night shift workers, has been related to lower circulating levels of melatonin, a hormone with recognized cancer protective properties. However, little is known about the relationship of other lifestyle factors or endogenous sex steroid hormones with melatonin levels. We examined cross-sectional associations of age, reproductive and menopausal factors, body mass index (BMI), alcohol consumption, smoking history, night shift work, as well as several other breast cancer risk factors, and circulating sex steroid hormone levels with creatinine-adjusted morning urinary melatonin (6-sulfatoxymelatonin, aMT6s) levels. Participants were 459 healthy, primarily premenopausal (age range 33-50 yr) women from the Nurses' Health Study II (NHS II). Using multiple linear regression, we computed least-square mean hormone levels across categories of lifestyle factors. Age was inversely related to aMT6s levels, particularly before menopause (premenopausal women, <or=39 yr versus >or=49 yr; aMT6s, 20.8 ng/mg versus 11.8 ng/mg creatinine; P for trend, 0.02). In multivariate analyses, BMI was significantly and inversely associated with aMT6s levels (P for trend, <0.01). Higher pack-years of smoking were associated with significantly lower aMT6s levels (never smoker versus 15+ pack-years, aMT6s = 17.4 ng/mg versus 12.3 ng/mg creatinine; P for trend, 0.04). We also observed a positive association between parity and aMT6s levels (P for trend, <0.01), but no other reproductive factors nor any of the sex hormones (estradiol, progesterone, estrone, estrone sulfate, dehydroepiandrostenedione, dehydroepiandrostenedione sulfate, testosterone, and androstenedione), as measured either in the luteal or the follicular phase of the menstrual cycle, were significantly associated with aMT6s. In conclusion, higher age, BMI, and heavy smoking were significantly related to lower levels of melatonin, whereas parity was significantly associated with higher aMT6s levels. Melatonin levels may be one mechanism through which these factors influence the development of cancer, but more studies are needed to elucidate these mechanisms definitively.

Night work and risk of breast cancer

BACKGROUND

Melatonin shows potential oncostatic activity and is acutely suppressed by light exposure. Some evidence suggests an association between night work and breast cancer risk, possibly through the melatonin pathway.

METHODS

In a cohort of premenopausal nurses, we prospectively studied the relation between rotating night shift work and breast cancer risk. Total number of months during which the nurses worked rotating night shifts was first assessed at baseline in 1989 and periodically updated thereafter. We used Cox proportional hazards models to calculate relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS

Among 115,022 women without cancer at baseline, 1,352 developed invasive breast cancer during 12 years of follow up. Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating night shift work (multivariate RR = 1.79; 95% CI = 1.06-3.01). There was no increase in risk associated with fewer years of rotating night work.

CONCLUSION

Our results suggest a modestly elevated risk of breast cancer after longer periods of rotating night work. Additional studies are warranted to rule out small sample size or uncontrolled sources for confounding as alternative explanations.

Night work and breast cancer risk: a systematic review and meta-analysis

The association between occupations that involve night shift work (a surrogate for exposure to light at night with subsequent melatonin suppression) and breast cancer risk is uncertain. We therefore conducted a systematic review and meta-analysis of observational studies to assess the effects of night work on breast cancer risk. Data sources were MEDLINE from January 1960 to January 2005, experts in the field, bibliographies, and abstracts. Search terms included night work terms, flight personnel terms, cancer terms, and risk terms. Independent data extraction by two authors using standardised forms was performed. The method of DerSimonian and Laird was used to derive combined estimates and Egger's; and Begg and Mazumdar's tests for publication bias were conducted. Based on 13 studies, including seven studies of airline cabin crew and six studies of other night shift workers, the aggregate estimate for all studies combined was 1.48 (95% CI, 1.36-1.61), with a similar significant elevation of breast cancer risk among female airline cabin crew (standardised incidence ratio (SIR), 1.44; 95% CI, 1.26-1.65), and female night workers (relative risk (RR), 1.51; 95% CI, 1.36-1.68) separately. We found some evidence suggesting confounding due to incomplete adjustment for breast cancer risk factors, with smaller effects in the studies that more completely adjusted for reproductive history and other confounding factors. Egger's and Begg and Mazumdar's tests for publication bias showed no significant asymmetry (P>0.05). Studies on night shift work and breast cancer risk collectively show an increased breast cancer risk among women. Publication bias is unlikely to have influenced the results.

Melatonin in the treatment of cancer: a systematic review of randomized controlled trials and meta-analysis

Most observational studies show an association between melatonin and cancer in humans. We conducted a systematic review of randomized controlled trials (RCTs) of melatonin in solid tumor cancer patients and its effect on survival at 1 yr. With the aid of an information specialist, we searched 10 electronic databases from inception to October 2004. We included trials using melatonin as either sole treatment or as adjunct treatment. Prespecified criteria guided our assessment of trial quality. We conducted a meta-analysis using a random effects model. We included 10 RCTs published between 1992 and 2003 and included 643 patients. All trials included solid tumor cancers. All trials were conducted at the same hospital network, and were unblinded. Melatonin reduced the risk of death at 1 yr (relative risk: 0.66, 95% confidence interval: 0.59-0.73, I2=0%, heterogeneity P<or=0.56). Effects were consistent across melatonin dose, and type of cancer. No severe adverse events were reported. The substantial reduction in risk of death, low adverse events reported and low costs related to this intervention suggest great potential for melatonin in treating cancer. Confirming the efficacy and safety of melatonin in cancer treatment will require completion of blinded, independently conducted RCTs.

Biotransformation of melatonin in human breast cancer cell lines: role of sulfotransferase 1A1

The biologically active melatonin metabolite, 6-hydroxymelatonin (6-OHMel), is conjugated to form 6-hydroxymelatonin sulfate (6-OHMelS). To elucidate the role of the sulfotransferase (SULT) enzyme 1A1, considerably expressed in normal and malignant human breast cells, we measured the formation of 6-OHMelS by ELISA in hormone-dependent MCF-7 and hormone-independent MDA-MB231 (MDA) breast cancer cell lines after stable transfection with SULT1A1. In parent MDA cells, low SULT1A1 mRNA expression was associated with moderate 6-OHMelS formation as determined after application (24 hr) of 0.1 microM 6-OHMel. As expected, overexpression of SULT1A1 in MDA cells resulted in a 2.9- and 110-fold increase in 6-OHMelS in the cytosol and cellular supernatant respectively. Furthermore, 6.3- and 115-fold increases were observed after 0.5 microM, and 12.6- and 101-fold increases after 1 microM 6-OHMel respectively. In MCF-7 cells, because of high basal SULT1A1 expression, only two- to threefold increases in 6-OHMelS were observed after transfection with the enzyme. In total, 866 and 539 pmol/mg protein 6-OHMelS were formed from 1 microM 6-OHMel in SULT1A1 overexpressing MDA and MCF-7 cells, respectively, whereas application of 1 microM melatonin produced only <1% of 6-OHMelS. Possible interactions with the SULT1A1 substrate tamoxifen (tam), an anti-estrogen applied in the therapy of breast cancer, were also studied. A concentration of 1 microM tam increased 6-OHMelS formation by approximately threefold in the presence of 1 microM melatonin or 1 microM 6-OHMel respectively. However, no alterations were detected after application of 1 microM 4-hydroxy-tamoxifen. In summary, we demonstrate the importance of SULT1A1 for the biotransformation of 6-OHMel in human breast cancer cells. Our data further suggest that tam can modulate melatonin biotransformation.

Antioxidant activity of melatonin and a pinoline derivative on linoleate model system

This study aimed at investigating the in vitro protective effects of GWC22, a novel pinoline derivative [6-ethyl-1-(3-methoxyphenyl)-2-propyl-1,2,3,4-tetrahydro-beta-carboline] chlorhydrate, against radiation-induced oxidation of linoleate initiated by hydroxyl radicals ((*)OH). Using linoleate micelles (10(-2) m) as lipid model, two indexes of peroxidation have been measured, i.e. conjugated dienes and hydroperoxides. Similar determinations were performed with melatonin in order to compare the protective effects of the two compounds. It was observed that, the higher the concentration of GWC22 (or melatonin) (3 x 10(-5) to 10(-4) m), the stronger the antioxidant ability. In these in vitro assays, GWC22 showed a better antioxidant effect than melatonin for a given antioxidant concentration. A reaction scheme has been proposed to explain the inhibitory effect of an antioxidant via the propagating steps of the lipid peroxidation. Indeed, we have suggested that melatonin and GWC22 may compete with the fatty acid to scavenge lipid peroxyl radicals (LOO(*)). We have estimated a lower limit for the LOO(*) rate constant for GWC22 (>/=1.4 x 10(5)/m/s) and for melatonin (>/=2.8 x 10(4)/m/s) assuming that the k-value of the propagating step in linoleate (LOO(*) + linoleate) was 1.4 x 10(3)/m/s. The difference of reactivity between melatonin and GWC22 in this model system is assumed to be related to their relative lipophilicity.

Antiproliferative activity of melatonin by transcriptional inhibition of cyclin D1 expression: a molecular basis for melatonin-induced oncostatic effects

Melatonin is endowed with a growth inhibitory effect in MCF-7 breast cancer cells whose mechanism has been related to an antiestrogenic activity exerted by inhibition of binding of the estradiol-estrogen receptor complex to its DNA responsive element. Looking for downstream gene determinants of this effect, we performed a transcriptome profiling by high-density microarrays of estrogen-treated MCF-7 cells exposed or not to melatonin. We found that cyclin D1 was one of the main downregulated genes by melatonin. Validation experiments clearly confirm that in MCF-7 cells the estrogen-induced growth inhibitory activity of melatonin is consistently associated with inhibition of estrogen-elicited cyclin D1 induction. This effect is almost purely transcriptional. Reporter gene assays indicate that the same portion of the cyclin D1 promoter which confers estrogen sensitivity, encompassing a potential cAMP responsive element binding site, is repressed by melatonin. Transcriptional downregulation of cyclin D1 is the key molecular event for melatonin's antiproliferative activity, as this activity can be completely and selectively rescued by transient cyclin D1 overexpression. Finally, we provide indirect evidence that the effect of melatonin on the cyclin D1 promoter is mediated by the c-jun and ATF-2 proteins, known to bind the minimal estrogen-sensitive cyclin D1 promoter element. These findings establish for the first time a molecular link between melatonin and its effects on the cell cycle, providing at the same time a rationale for its use in adjuvant chemotherapy.

Season, Sun, Sex, and Cervical Cancer

INTRODUCTION

Sunlight's UV B component, a known cellular immunosupressant, carcinogen, and activator of viral infections, is generally seasonally available. Venereal human papillomavirus (HPV) transmission, at least in part, causes cervical cancer. We have previously inspected the monthly rates of venereal HPV infection and sunlight fluency in Southern Holland over 16 consecutive years. Both peak in August with at least 2-fold seasonality. The amount of available sunlight and the rate of Papanicolaou (Pap) smear screen-detected HPV are positively correlated. We now investigate whether premalignant and malignant cervical epithelial changes are also seasonal and related to seasonal sunlight fluency.

METHODS

We have studied >900,000 consecutive, serially independent, interpretable screening Pap smears obtained by a single cervical cancer screening laboratory in Leiden, Holland, during a continuous 16-year span from 1983 through 1998. The average monthly rates of premalignant and malignant epithelial change were inspected and the annual patterns contrasted to the annual pattern of sunlight fluency at this global location and to monthly average HPV infection rate. Because HPV is venereally transmitted, Dutch seasonal sexual behavior was evaluated by assessment of the annual pattern of Dutch conception frequency as a competing cause for cervical cancer seasonality.

RESULTS

(a) Twice as many premalignant and malignant epithelial changes were found among Pap smears obtained in the summer months, with an August peak concurrent with histopathologic evidence of HPV infection and sunlight fluency in Southern Holland. (b) Monthly sunlight fluency is correlated positively with both the monthly rates of Pap smear-detected cervical epithelial dysplasia and carcinomatous histopathology, as well as HPV. (c) Conception frequency, in this location, peaks in Spring not summer, and has a 4.8% annual amplitude.

CONCLUSIONS

(a) Cervical epithelial HPV infection and HPV-induced cervical epithelial dysplasia and carcinomatous change may each be novel sun exposure risks and thereby behaviorably avoidable. (b) Because screening Pap smears uncover many abnormalities that resolve spontaneously (false positives), these data may argue for screening and follow-up Pap smear examinations in seasons other than summer in the Northern Hemisphere, to diminish the false-positive smear rate. Global data are available to confirm and further test each of these conclusions.

Urinary Melatonin Levels and Breast Cancer Risk

Exposure to light at night suppresses melatonin production, and night-shift work (a surrogate for such exposure) has been associated with an increased risk of breast cancer. However, the association between circulating melatonin levels and breast cancer risk is unclear. In a prospective case-control study nested within the Nurses' Health Study II cohort, we measured the concentration of the major melatonin metabolite, 6-sulphatoxymelatonin (aMT6s), in the first morning urine of 147 women with invasive breast cancer and 291 matched control subjects. In logistic regression models, the relative risk (reported as the odds ratio [OR]) of invasive breast cancer for women in the highest quartile of urinary aMT6s compared with those in the lowest was 0.59 (95% confidence interval [CI] = 0.36 to 0.97). This association was essentially unchanged after adjustment for breast cancer risk factors or plasma sex hormone levels but was slightly weakened when the analysis included 43 case patients with in situ breast cancer and their 85 matched control subjects (OR = 0.70, 95% CI = 0.47 to 1.06). The exclusion of women who had a history of night-shift work left our findings largely unchanged. These prospective data support the hypothesis that higher melatonin levels, as measured in first morning urine, are associated with a lower risk of breast cancer.

A role of melatonin in neuroectodermal-mesodermal interactions: the hair follicle synthesizes melatonin and expresses functional melatonin receptors

Since mammalian skin expresses the enzymatic apparatus for melatonin synthesis, it may be an extrapineal site of melatonin synthesis. However, evidence is still lacking that this is really the case in situ. Here, we demonstrate melatonin-like immunoreactivity (IR) in the outer root sheath (ORS) of mouse and human hair follicles (HFs), which corresponds to melatonin, as shown by radioimmunoassay and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The melatonin concentration in organ-cultured mouse skin, mouse vibrissae follicles, and human scalp HFs far exceeds the respective melatonin serum level and is significantly increased ex vivo by stimulation with norepinephrine (NE), the key stimulus for pineal melatonin synthesis. By real-time PCR, transcripts for the melatonin membrane receptor MT2 and for the nuclear mediator of melatonin signaling, retinoid orphan receptor alpha (ROR)alpha, are detectable in murine back skin. Transcript levels for these receptors fluctuate in a hair cycle-dependent manner, and are maximal during apoptosis-driven HF regression (catagen). Melatonin may play a role in hair cycle regulation, since its receptors (MT2 and RORalpha) are expressed in murine skin in a hair cycle-dependent manner, and because it inhibits keratinocyte apoptosis and down-regulates ERalpha expression. Therefore, the HF is both, a prominent extrapineal melatonin source, and an important peripheral melatonin target tissue. Regulated intrafollicular melatonin synthesis and signaling may play a previously unrecognized role in the endogenous controls of hair growth, for example, by modulating keratinocyte apoptosis during catagen and by desensitizing the HF to estrogen signaling. As a prototypic neuroectodermal-mesodermal interaction model, the HF can be exploited for dissecting the obscure role of melatonin in such interactions in peripheral tissues.

Putting cancer to sleep at night: the neuroendocrine/circadian melatonin signal

Physiological and pharmacological blood concentrations of melatonin inhibit tumorigenesis in a variety of in vivo and in vitro experimental models of neoplasia. Evidence indicates that melatonin's anticancer effects are exerted via inhibition of cell proliferation and a stimulation of differentiation and apoptosis. A new mechanism by which physiological and pharmacological blood levels of melatonin inhibit cancer growth in vivois via a melatonin-induced suppression of tumor linoleic acid (LA) uptake and its metabolism to the important mitogenic signaling molecule 13-hydroxyoctadecadienoic acid (13-HODE). Melatonin suppresses cAMP formation and inhibits tumor uptake of LA and its metabolism to 13-HODE via a melatonin receptor-mediated mechanism in both tissue-isolated rat hepatoma 7288 CTC and human breast cancer xenografts. It has been postulated that in industrialized societies, light at night, by suppressing melatonin production, poses a new risk for the development of breast cancer and, perhaps, other cancers as well. In support of this hypothesis, light during darkness suppresses nocturnal melatonin production and stimulates the LA metabolism and growth of rat hepatoma and human breast cancer xenografts. Nocturnal dietary supplementation with melatonin, at levels contained in a melatonin-rich diet, inhibits rat hepatoma growth via the mechanisms described above. The nocturnal melatonin signal organizes tumor metabolism and growth within circadian time structure that can be further reinforced by appropriately timed melatonin supplementation. Dietary melatonin supplementation working in concert with the endogenous melatonin signal has the potential to be a new preventive/therapeutic strategy to optimize the host/cancer balance in favor of host survival and quality of life.

A comparison of the action of amifostine and melatonin on DNA-damaging effects and apoptosis induced by idarubicin in normal and cancer cells

Amifostine is a well-known cell protector and its actions involve free radical scavenging, which is also considered as a mechanism underlying the protective actions of melatonin, a secretory product of the pineal gland. In this work we compared the action of 14 mM amifostine and 50 microM melatonin on DNA damage and apoptosis induced by idarubicin in normal human lymphocytes, leukemic K562 cells and HeLa cancer cells. We employed the alkaline comet assay and pulse-field gel electrophoresis to estimate DNA damage. Apoptosis was evaluated by caspase 3 activity assay assisted by the comet assay to evaluate DNA fragmentation and DAPI staining for detection of morphological changes in chromatin. We found that idarubicin induced apoptosis in normal and cancer cells and its level was correlated with the extent of DNA strand breaks. Amifostine reduced apoptosis and DNA damage in normal cells, but it potentiated these effects in cancer cells in this in vitro study. Melatonin protected both normal and cancer cells against genotoxic treatment and apoptosis induced by idarubicin. We conclude that despite its recognized potential as an antioxidant, melatonin should be considered with caution when used in combination with cancer chemotherapy agents, especially in the case of leukemias.

Simultaneous spectrofluorimetric and spectrophotometric determination of melatonin and pyridoxine in pharmaceutical preparations by multivariate calibration methods

Partial least-squares (PLS) calibration and principal component regression (PCR) methods were utilized for the simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT). Since emission and adsorption spectra of these drugs overlap, PY and MT cannot be directly determined by fluorimetric nor by spectrophotometric methods. Full-spectrum multivariate calibration PLS and PCR methods were developed for both fluorimetry and spectrophotometry. The conditions were optimized for fluorimetric as well as for spectrophotometric determination of both drugs. The simultaneous determination of PY and MT was carried out in mixtures by recording the emission fluorescence spectrum between 324 and 500 nm (lambda(ex) 285 nm) for fluorimetry, and by recording the absorption spectrum between 250 and 350 nm for spectrophotometry (lambda(max(PY)) 310 nm, lambda(max(MT)) 278 nm). The experimental calibration matrixes were designed orthogonally. At the optimum conditions, dynamic ranges were 0.04-1.3 and 0.1-4 microg ml(-1) for fluorimetry and 1-22 and 1-24 microg ml(-1) for spectrophotometry for MT and PY, respectively. The calibration concentrations were prepared in the dynamic ranges. The parameters of the chemometrics procedure for the simultaneous determination of MT and PY were optimized, and the proposed methods were validated with prediction set. Finally the procedures were successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of PY and MT in synthetic mixtures and in a pharmaceutical formulation.

Melatonin-induced modulation of glucose metabolism in primary cultures of rabbit kidney-cortex tubules

The effect of melatonin on glucose metabolism in the presence and absence of insulin has been investigated in the primary cultures of renal tubules grown in a defined medium. In the absence of glucose in the medium containing 5 microg/mL of insulin and 2 mm alanine + 5 mm glycerol + 0.5 mm octanoate, 100 nm melatonin stimulated both glucose and lactate synthesis, while in the medium devoid of insulin melatonin action was negligible. Melatonin-induced increase in glucose and lactate synthesis was accompanied by an enhancement of alanine and glycerol consumption. In view of measurements of [U-14C]L-alanine and [U-14C]L-glycerol incorporation into glucose, it is likely that melatonin increased alanine utilization for glucose production, while accelerated lactate synthesis was because of an enhanced glycerol consumption. As (i) 10 nm luzindole attenuated the stimulatory action of melatonin on glucose formation and (ii) the indole induced a decrease in intracellular cAMP level, it seems likely that in renal tubules melatonin binds to ML1 membrane receptor subtype. In view of a decline of intracellular fructose-1,6-bisphosphate content accompanied by a significant rise in hexose-6-phosphate and glucose levels, melatonin might result in an acceleration of flux through fructose-1,6-bisphosphatase probably because of an increase in the active, dephosphorylated form of this enzyme. Thus, the administration of melatonin in combination with insulin might be beneficial for diabetic therapy because of protection against hypoglycemia.

Circadian regulation of cell cycle and apoptosis proteins in mouse bone marrow and tumor

Proapoptotic drugs such as docetaxel displayed least toxicity and highest antitumor efficacy following dosing during the circadian rest phase in mice, suggesting that cell cycle and apoptotic processes could be regulated by the circadian clock. In study 1, mouse bone marrow and/or tumor were obtained every 4 h for 24 h in C3H/HeN mice with or without MA13/C mammary adenocarcinoma in order to determine the circadian patterns in cell-cycle phase distribution and BCL-2 anti-apoptotic protein expression. In study 2, mouse bone marrow from B6D2F1 mice was sampled every 3 h for 24 h in order to confirm the BCL-2 rhythm and to study its relation with 24 h changes in the expression of proapoptotic BCL-2-associated X protein (BAX) protein and clock genes mPer2, mBmal1, mClock, and mTim mRNAs. The rhythms in G1-, S- or G2/M-phase cells were shifted in tumor compared with bone marrow. In the tumor, the mean proportion of G2/M-phase cells increased by 75% from late rest to late activity span (P from cosinor = 0.001). No 24 h rhythm was found for BCL-2 in tumors. In contrast to this, in the bone marrow, mean BCL-2 expression varied 2.8-fold in B6D2F1 mice (P=0.025) and 3- or 4.5-fold in tumor-bearing and nontumor-bearing C3H/HeN mice, with a peak during the early rest span (P=0.024 and P<0.001, respectively). BAX varied fivefold during the 24 h span with a major peak occurring near mid-activity (P=0.007). The mean mRNAs of mPer2, mClock, and mBmal1 varied twofold to threefold over the 24 h, with high values during the activity span (P<0.05). In the tumor, the circadian organization in cell-cycle phase distribution was shifted and BCL2 rhythm was ablated. Conversely, a molecular circadian clock likely regulated BCL-2 and BAX expression in the bone marrow, increasing cellular protection against apoptosis during the rest span.

Effects of indole fatty alcohols on the differentiation of neural stem cell derived neurospheres

In a search for inducers of neuronal differentiation to treat neurodegenerative diseases such as Alzheimer's disease, a series of indole fatty alcohols (IFAs) were prepared. 13c (n = 18) was able to promote the differentiation of neural stem cell derived neurospheres into neurons at a concentration of 10 nM. Analysis of the expression of the Notch pathway genes in neurospheres treated during the differentiation phase with 13c (n = 18) revealed a significant decrease in the transcription of the Notch 4 receptor.

Protective properties of melatonin-loaded nanoparticles against lipid peroxidation

The aim of this study was to prepare melatonin-loaded nanoparticles (nanocapsules and nanospheres) by nanoprecipitation, using Eudragit S100 as polymer. The potential of these systems to protect lipids against peroxidation was evaluated in comparison to melatonin in aqueous solution and nanoemulsion. Liposomes and microsomes were used as model of a lipid membrane and lipid peroxidation was induced by free radical ascorbyl. Nanocapsule and nanosphere suspensions presented total recoveries of melatonin near 100% and associated drug around 55%. The zeta potential values were negative and the hydrodynamic diameter of particles were lower than 255 nm. The results demonstrate that the lipids were protected against peroxidation from 8 to 51% due to the presence of the melatonin and that this effect depended on the drug dose, the type of the lipid substrate and the type of colloid, in which melatonin was incorporated. Nanocapsules and nanospheres provided an important increase in the antioxidant effect of melatonin against lipid peroxidation.

Melatonin protects against ionizing radiation-induced oxidative damage in corpus cavernosum and urinary bladder in rats

The objective of this study was to examine the potential radioprotective properties of pharmacological doses of melatonin on corpus cavernosum and bladder tissues of whole-body irradiated (IR) rats. A total of 32 male Sprague-Dawley rats were exposed to irradiation performed with a LINAC which produced 6 MV photons at a focus 100 cm distant from the skin. Under ketamine anesthesia, each rat received a single whole-body dose of 800 cGy. Immediately before and after IR, rats were treated with either saline or melatonin (20 and 10 mg/kg, i.p.) and decapitated at 12 hr after exposure to irradiation. Another group of rats was followed for 72 hr after IR, where melatonin injections were repeated once daily. Tissue levels of malondialdehyde (MDA), an index of lipid peroxidation, and glutathione (GSH), a key antioxidant, were estimated in corpus cavernosum and urinary bladder. Tissues were also examined microscopically. The results demonstrate that both 12 and 72 hr following IR, tissue levels of MDA were elevated (P < 0.001), while GSH levels were reduced (P < 0.01) in both tissues. On the other hand, melatonin reversed these changes significantly (P < 0.05-0.01), concomitant with the improvement in histological appearances. Our results show that whole-body irradiation causes oxidative damage in the tissues of the genitourinary system. As melatonin administration reversed oxidative organ injury, as assessed by biochemical and histopathological findings, it is suggested that supplementing cancer patients with adjuvant therapy of melatonin may have some benefit for successful radiotherapy.

Melatonin as a radioprotective agent: a review

Melatonin (N-acetyl-5-methoxytryptamine), the chief secretory product of the pineal gland in the brain, is well known for its functional versatility. In hundreds of investigations, melatonin has been documented as a direct free radical scavenger and an indirect antioxidant, as well as an important immunomodulatory agent. The radical scavenging ability of melatonin is believed to work via electron donation to detoxify a variety of reactive oxygen and nitrogen species, including the highly toxic hydroxyl radical. It has long been recognized that the damaging effects of ionizing radiation are brought about by both direct and indirect mechanisms. The direct action produces disruption of sensitive molecules in the cells, whereas the indirect effects ( approximately 70%) result from its interaction with water molecules, which results in the production of highly reactive free radicals such as *OH, *H, and e(aq)- and their subsequent action on subcellular structures. The hydroxyl radical scavenging ability of melatonin was used as a rationale to determine its radioprotective efficiency. Indeed, the results from many in vitro and in vivo investigations have confirmed that melatonin protects mammalian cells from the toxic effects of ionizing radiation. Furthermore, several clinical reports indicate that melatonin administration, either alone or in combination with traditional radiotherapy, results in a favorable efficacy:toxicity ratio during the treatment of human cancers. This article reviews the literature from laboratory investigations that document the ability of melatonin to scavenge a variety of free radicals (including the hydroxyl radical induced by ionizing radiation) and summarizes the evidence that should be used to design larger translational research-based clinical trials using melatonin as a radioprotector and also in cancer radiotherapy. The potential use of melatonin for protecting individuals from radiation terrorism is also considered.

Mindfulness-based stress reduction in relation to quality of life, mood, symptoms of stress and levels of cortisol, dehydroepiandrosterone sulfate (DHEAS) and melatonin in breast and prostate cancer outpatients

OBJECTIVES

This study investigated the relationships between a mindfulness-based stress reduction meditation program for early stage breast and prostate cancer patients and quality of life, mood states, stress symptoms, and levels of cortisol, dehydroepiandrosterone-sulfate (DHEAS) and melatonin.

METHODS

Fifty-nine patients with breast cancer and 10 with prostate cancer enrolled in an eight-week Mindfulness-Based Stress Reduction (MBSR) program that incorporated relaxation, meditation, gentle yoga, and daily home practice. Demographic and health behavior variables, quality of life, mood, stress, and the hormone measures of salivary cortisol (assessed three times/day), plasma DHEAS, and salivary melatonin were assessed pre- and post-intervention.

RESULTS

Fifty-eight and 42 patients were assessed pre- and post-intervention, respectively. Significant improvements were seen in overall quality of life, symptoms of stress, and sleep quality, but these improvements were not significantly correlated with the degree of program attendance or minutes of home practice. No significant improvements were seen in mood disturbance. Improvements in quality of life were associated with decreases in afternoon cortisol levels, but not with morning or evening levels. Changes in stress symptoms or mood were not related to changes in hormone levels. Approximately 40% of the sample demonstrated abnormal cortisol secretion patterns both pre- and post-intervention, but within that group patterns shifted from "inverted-V-shaped" patterns towards more "V-shaped" patterns of secretion. No overall changes in DHEAS or melatonin were found, but nonsignificant shifts in DHEAS patterns were consistent with healthier profiles for both men and women.

CONCLUSIONS

MBSR program enrollment was associated with enhanced quality of life and decreased stress symptoms in breast and prostate cancer patients, and resulted in possibly beneficial changes in hypothalamic-pituitary-adrenal (HPA) axis functioning. These pilot data represent a preliminary investigation of the relationships between MBSR program participation and hormone levels, highlighting the need for better-controlled studies in this area.

Melatonin and cancer risk: does light at night compromise physiologic cancer protection by lowering serum melatonin levels?

The suprachiasmatic nuclei in the hypothalamus, one of the most important physiological determinants of alertness and performance, drive a circadian pacemaker in mammals, with an intrinsic period averaging 24 h. Light is the primary stimulus to the disruption and resetting of this pacemaker, which is expressed in changing melatonin rhythms. Melatonin production in humans decreases when people are exposed to light at night. Since melatonin shows potential oncostatic action in a variety of tumours, it is possible that lowered serum melatonin levels caused by exposure to light at night enhance the general tumour development. Cancer is the second leading cause of death in industrialised countries like the United States, where a significant proportion of workers engage in shift work, making a hypothesised relation between light exposure at night and cancer risk relevant. Observational studies support an association between night work and cancer risk. We hypothesise that the potential primary culprit for this observed association is the lack of melatonin, a cancer-protective agent whose production is severely diminished in people exposed to light at night.

Light at Night and Cancer Risk¶

Environmental lighting powerfully suppresses the physiologic release of melatonin, which typically peaks in the middle of the night. This decreased melatonin production has been hypothesized to increase the risk of cancer. Evidence from experimental studies supports a link between melatonin and tumor growth. There is also fairly consistent indirect evidence from observational studies for an association between melatonin suppression, using night work as a surrogate, and breast cancer risk.

Determination of melatonin in human plasma with solid-phase extraction, high-performance liquid chromatography and fluorescence detection

A new bioanalytical method for the determination of melatonin in plasma with high-performance liquid chromatography (HPLC) and fluorescence detection preceded by solid-phase extraction has been developed and validated. Melatonin was extracted from 3 mL plasma using a Waters Oasis HLB solid-phase extraction cartridge and the elute was evaporated to dryness and dissolved in 200 microl mobile phase; acetonitrile-phosphate buffer, 0.01 M pH 7.2 (25:75, v/v). 125 microL was injected into the HPLC system and separation was carried out on a Waters SymmetryShield RP18 column 5 microm (250 x 4.6 mm). Excitation and emission wavelengths were set to 285 nm and 345 nm, respectively. The HPLC system was able to separate melatonin and internal standard (5-fluorotryptamine) from other endogenous indole compounds such as serotonin and tryptophan. Determination down to 0.10 nmol/L was possible, with an intra-assay precision of about 13%. Melatonin was stable in plasma for at least 30 days at about 23 degrees C.

Protective effect of melatonin against fractionated irradiation-induced epiphyseal injury in a weanling rat model

The effects of melatonin, a free-radical scavenger and a general antioxidant, on radiation-induced growth plate injury have not been studied previously. The purpose of this study was to determine the potential benefits of sparing longitudinal bone growth by fractionated radiotherapy alone compared with pretreatment with melatonin that provides differential radioprotection of normal cells. Weanling 4-wk-old (75-100 g) male Sprague-Dawley rats were randomly assigned to one of three groups: Group R received fractionated radiation alone (n = 8); groups M5 (n = 8) and M15 (n = 7) received 5 or 15 mg/kg melatonin prior to fractionated radiation, respectively. The distal femur and proximal tibia in the right leg of each animal were exposed to a therapeutic X-irradiation dose (25 Gy total in three fractions) with the contralateral left leg as the non-irradiated control. Melatonin was administered intraperitoneally to the animals 30 min before radiation exposure. Six weeks after treatment, the rats were killed and the lower limbs disarticulated, skeletonized, radiographed, and bone growth was calculated based on measurement of the bone lengths. Fractionated radiation resulted in a mean percent overall limb growth loss of 41.2 +/- 9.5 and a mean percent overall limb discrepancy of 11.2 +/- 2.2. The administration of 5 or 15 mg/kg melatonin before each of the three fractions of radiotherapy reduced the mean percent overall limb growth loss to 33.9 +/- 5.8 and 32.2 +/- 4.5, respectively, and the mean percent overall limb discrepancy to 9.4 +/- 1.6 and 8.9 +/- 1.1, respectively; these values were significantly different compared with irradiation alone (range: P = 0.01-0.04). When compared with Group R, the growth arrest recovered by 5 or 15 mg/kg melatonin was 19.7 and 24.1% for the tibia, 7 and 18.6% for the femur, and 17.7 and 21.8% for the total limb, respectively. These results support further investigation of melatonin in combination with fractionation for potential use in growing children requiring radiotherapy to the extremity for malignant tumors.

Light, timing of biological rhythms, and chronodisruption in man

This paper reviews abundant evidence suggesting that causes and course of aging and cancers can be considered as being both light- and rhythm-related. We define chronodisruption as a relevant disturbance of orderly biological rhythms over days and seasons and years in man. Light is the primary external mediator and melatonin a primary internal intermediary of such disturbances, which can result in earlier deaths via premature aging and cancers. We conclude that experimental and epidemiological research can provide further insights into common denominators of these chronic processes and may offer novel and uniform targets for prevention.

Analysis of tumor control and toxicity in patients who have survived at least one year after radiosurgery for brain metastases

PURPOSE

To better evaluate tumor control and toxicity from radiosurgery for brain metastases, we analyzed these outcomes in patients who had survived at least 1 year after radiosurgery.

METHODS AND MATERIALS

We evaluated the results of gamma knife stereotactic radiosurgery (SRS) for 208 brain metastases in 137 patients who were followed for a median of 18 months (range 12-122) after radiosurgery. The median patient age was 53 years (range 3-83). Ninety-nine patients had solitary metastases. Thirty-eight had multiple tumors. Sixty-nine patients underwent initial SRS with whole brain radiotherapy (WBRT), 39 had initial SRS alone, and 27 patients had failed prior WBRT. The median treatment volume was 1.9 cm(3) (range 0.05-21.2). The median marginal tumor dose was 16 Gy (range 12-25). The most common histologic types included non-small-cell lung cancer, breast cancer, melanoma, and renal cell carcinoma, which comprised 37.0%, 22.6%, 13.0%, and 9.13% of the lesions, respectively. Forty-five tumors were associated with extensive edema.

RESULTS

At 1 and 5 years, the local tumor control rate was 89.6% +/- 2.1% and 62.8% +/- 6.9%, distal intracranial relapse occurred in 23% +/- 3.6% and 67.1% +/- 8.7%, and postradiosurgical sequelae developed in 2.8% +/- 1.2% and 11.4% +/- 3.5% of patients, respectively. Multivariate analysis found that local control decreased with tumor volume (p = 0.0002), SRS without WBRT (p = 0.008), and extensive edema (p = 0.024); distal intracranial recurrence correlated with younger patient age (p = 0.0018); and postradiosurgical sequelae increased with increasing tumor volume (p = 0.0085).

CONCLUSION

Long-term control of brain metastases and complication rates in this selective series of patients surviving >or=1 year after radiosurgery were similar to previously reported actuarial estimates. Large metastases and metastases associated with extensive edema can be difficult to control by radiosurgery, particularly without WBRT.

Report from the Radiation Oncology Committee of the Southwest Oncology Group (SWOG)

To achieve the ultimate goal of cancer treatment, which is 100% cancer control with negligible toxicity, the therapeutic window must be enlarged, allowing for higher doses of beneficial treatments with reduced toxicity. The advent of image- and metabolism-guided therapy offers the best opportunity to date for combining modern radiation targeting and imaging techniques. Indeed, for the first time, it is reasonable to locally target metastatic disease with the goal of sterilization. Combining these focal radiation techniques with novel targeted antiproliferative agents and full-dose classic cytotoxic chemotherapy will become more effective as we learn to use these compounds in a less systemically toxic manner and as radiation fields become more defined. In addition, increasing numbers of biologic modifiers of normal tissue response are becoming available, and they suggest great promise for decreasing the normal tissue toxicity resulting from both radiation and chemotherapy treatments. Thus, radiation metastectomy for gross metastases, used together with systemic control of micrometastatic disease, may yield improved survival rates. This hypothesis is ready for testing in cancers of the breast, prostate, colon, and in sarcomas. Enlarging the therapeutic window is a major goal that would allow for an increasingly favorable therapeutic gain.

Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial

Numerous experimental data have documented the oncostatic properties of melatonin. In addition to its potential direct antitumor activity, melatonin has proved to modulate the effects of cancer chemotherapy, by enhancing its therapeutic efficacy and reducing its toxicity. The increase in chemotherapeutic efficacy by melatonin may depend on two main mechanisms, namely prevention of chemotherapy-induced lymphocyte damage and its antioxidant effect, which has been proved to amplify cytotoxic actions of the chemotherapeutic agents against cancer cells. However, the clinical results available at present with melatonin and chemotherapy in the treatment of human neoplasms are generally limited to the evaluation of 1-year survival in patients with very advanced disease. Thus, the present study was performed to assess the 5-year survival results in metastatic non-small cell lung cancer patients obtained with a chemotherapeutic regimen consisting of cisplatin and etoposide, with or without the concomitant administration of melatonin (20 mg/day orally in the evening). The study included 100 consecutive patients who were randomized to receive chemotherapy alone or chemotherapy and melatonin. Both the overall tumor regression rate and the 5-year survival results were significantly higher in patients concomitantly treated with melatonin. In particular, no patient treated with chemotherapy alone was alive after 2 years, whereas a 5-year survival was achieved in three of 49 (6%) patients treated with chemotherapy and melatonin. Moreover, chemotherapy was better tolerated in patients treated with melatonin. This study confirms, in a considerable number of patients and for a long follow-up period, the possibility to improve the efficacy of chemotherapy in terms of both survival and quality of life by a concomitant administration of melatonin. This suggests a new biochemotherapeutic strategy in the treatment of human neoplasms.

Night-shift work and risk of colorectal cancer in the nurses' health study

Exposure to light at night suppresses the physiologic production of melatonin, a hormone that has antiproliferative effects on intestinal cancers. Although observational studies have associated night-shift work with an increased risk of breast cancer, the effect of night-shift work on the risk of other cancers is not known. We prospectively examined the relationship between working rotating night shifts and the risk of colorectal cancers among female participants in the Nurses' Health Study. We documented 602 incident cases of colorectal cancer among 78 586 women who were followed up from 1988 through 1998. Compared with women who never worked rotating night shifts, women who worked 1-14 years or 15 years or more on rotating night shifts had multivariate relative risks of colorectal cancer of 1.00 (95% confidence interval [CI] = 0.84 to 1.19) and 1.35 (95% CI = 1.03 to 1.77), respectively (P(trend) =.04). These data suggest that working a rotating night shift at least three nights per month for 15 or more years may increase the risk of colorectal cancer in women.