Melatonin: A Molecule for Reducing Breast Cancer Risk

Revealing Melatonin's Mysteries: Receptors, Signaling Pathways, and Therapeutics Applications

Melatonin (5-methoxy-acetyl tryptamine) is a sleep-inducing hormone, and the pineal gland produces it in response to the circadian clock of darkness. In the body, MT1 and MT2 receptors are mostly found, having an orthosteric pocket and ligand binding determinants. Melatonin acts by binding on melatonin receptors, intracellular proteins, and orphan nuclear receptors. It inhibits adenyl cyclase and activates phospholipase C, resulting in gene expression and an intracellular alteration environment. Melatonin signaling pathways are also associated with other intracellular signaling pathways, i. e., cAMP/PKA and MAPK/ERK pathways. Relative expression of different proteins depends on the coupling profile of G protein, accounting pharmacology of the melatonin receptor bias system, and mediates action in a Gi-dependent manner. It shows antioxidant, antitumor, antiproliferative, and neuroprotective activity. Different types of melatonin agonists have been synthesized for the treatment of sleeping disorders. Researchers have developed therapeutics that target melatonin signaling, which could benefit a wide range of medical conditions. This review focuses on melatonin receptors, pharmacology, and signaling cascades; it aims to provide basic mechanical aspects of the receptor's pharmacology, melatonin's functions in cancer and neurodegenerative diseases, and any treatments and drugs designed for these diseases. This will allow a basic comparison between the receptors in question, highlighting any parallels and differences that may exist and providing fundamental knowledge about these receptors to future researchers.

Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

Melatonin and 5-fluorouracil combination chemotherapy: opportunities and efficacy in cancer therapy

Combined chemotherapy is a treatment method based on the simultaneous use of two or more therapeutic agents; it is frequently necessary to produce a more effective treatment for cancer patients. Such combined treatments often improve the outcomes over that of the monotherapy approach, as the drugs synergistically target critical cell signaling pathways or work independently at different oncostatic sites. A better prognosis has been reported in patients treated with combination therapy than in patients treated with single drug chemotherapy. In recent decades, 5-fluorouracil (5-FU) has become one of the most widely used chemotherapy agents in cancer treatment. This medication, which is soluble in water, is used as the first line of anti-neoplastic agent in the treatment of several cancer types including breast, head and neck, stomach and colon cancer. Within the last three decades, many studies have investigated melatonin as an anti-cancer agent; this molecule exhibits various functions in controlling the behavior of cancer cells, such as inhibiting cell growth, inducing apoptosis, and inhibiting invasion. The aim of this review is to comprehensively evaluate the role of melatonin as a complementary agent with 5-FU-based chemotherapy for cancers. Additionally, we identify the potential common signaling pathways by which melatonin and 5-FU interact to enhance the efficacy of the combined therapy. Video abstract.

Exploring the Mechanical Perspective of a New Anti-Tumor Agent: Melatonin

Melatonin is a serotonin-derived pineal gland hormone with many biological functions like regulating the sleep-wake cycle, circadian rhythm, menstrual cycle, aging, immunity, and antioxidants. Melatonin synthesis and release are more pronounced during the night, whereas exposure to light decreases it. Evidence is mounting in favor of the therapeutic effects of melatonin in cancer prevention, treatment and delayed onset in various cancer subtypes. Melatonin exerts its anticancer effect through modification of its receptors such as melatonin 1 (MT1), melatonin 2 (MT2), and inhibition of cancer cell proliferation, epigenetic alterations (DNA methylation/demethylation, histone acetylation/deacetylation), metastasis, angiogenesis, altered cellular energetics, and immune evasion. Melatonin performs a significant function in immune modulation and enhances innate and cellular immunity. In addition, melatonin has a remarkable impact on epigenetic modulation of gene expression and alters the transcription of genes. As an adjuvant to cancer therapies, it acts by decreasing the side effects and boosting the therapeutic effects of chemotherapy. Since current treatments produce drug-induced unwanted toxicities and side effects, they require alternate therapies. A recent review article attempts to summarize the mechanistic perspective of melatonin in different cancer subtypes like skin cancer, breast cancer, hepatic cancer, renal cell cancer, non-small cell lung cancer (NSCLC), colon oral, neck, and head cancer. The various studies described in this review will give a firm basis for the future evolution of anticancer drugs.

The Role of Lead and Cadmium in Gynecological Malignancies

Lead and cadmium are non-essential and toxic heavy metals. Their presence and elevated levels can lead to many pathologies. They disrupt the antioxidant properties of many enzymes, consume the resources of antioxidant cells, and thus participate in the generation of oxidative stress, which may result in DNA damage. In addition, they have been found to be carcinogenic through their genotoxic properties. They have been shown to be present in various types of cancer, including cancer of the female reproductive system. Both metals have been recognized as metalloestrogens, which are important in hormone-related cancers. Participation in the oncogenesis of ovarian, endometrial and cervical cancer was analysed in detail, using the available research in this field. We emphasize their role as potential biomarkers in cancer risk and diagnosis as well as advancement of gynaecological malignancies.

Circadian rhythm-related factors of PER and CRY family genes function as novel therapeutic targets and prognostic biomarkers in lung adenocarcinoma

The period (PER) and cryptochrome (CRY) families play critical roles in circadian rhythms. The imbalance of circadian factors may lead to the occurrence of cancer. Expressions of PER and CRY family members decrease in various cancers. Nevertheless, expression levels, genetic variations, and molecular mechanisms of PER and CRY family members in lung adenocarcinoma (LUAD) and their correlations with prognoses and immune infiltration in LUAD patients are still unclear. In this study, to identify their biological functions in LUAD development, comprehensive high-throughput techniques were applied to analyze the relationships of expressions of PER and CRY family members with genetic variations, molecular mechanisms, and immune infiltration. The present results showed that transcription levels of PER1 and CRY2 in LUAD were significantly downregulated. High expression levels of PER2, PER3, CRY1, and CRY2 indicated longer overall survival. Some cancer signaling pathways were related to PER and CRY family members, such as cell-cycle, histidine metabolism, and progesterone-mediated oocyte maturation pathways. Expressions of PER and CRY family members significantly affected the infiltration of different immune cells. In conclusion, our findings may help better understand the molecular basis of LUAD, and provide new perspectives of PER and CRY family members as novel biomarkers for LUAD.

Physiological and pharmacological perspectives of melatonin

The pineal gland is a interface between light-dark cycle and shows neuro-endocrine functions. Melatonin is the primary hormone of pineal gland, secreted at night. The night-time melatonin peak regulates the physiological functions at dark. Melatonin has several unique features as it synchronises internal rhythm with daily and seasonal variations, regulates circadian rhythm and sleep-wake cycle. Physiologically melatonin involves in detoxification of free radicals, immune functions, neuro-protection, oncostatic effects, cardiovascular functions, reproduction, and foetal development. The precise functions of melatonin are exhibited by specific receptors. In relation to pathophysiology, impaired melatonin secretion promotes sleep disorder, cancer progression, type-2 diabetes, and neurodegenerative diseases. Several reports have highlighted the therapeutic benefits of melatonin specially related to cancer protection, sleep disorder, psychiatric disorders, and jet lag problems. This review will touch the most of the area of melatonin-oriented health impacts and its therapeutic aspects.

Protective Role of Melatonin and Its Metabolites in Skin Aging

The skin, being the largest organ in the human body, is exposed to the environment and suffers from both intrinsic and extrinsic aging factors. The skin aging process is characterized by several clinical features such as wrinkling, loss of elasticity, and rough-textured appearance. This complex process is accompanied with phenotypic and functional changes in cutaneous and immune cells, as well as structural and functional disturbances in extracellular matrix components such as collagens and elastin. Because skin health is considered one of the principal factors representing overall “well-being” and the perception of “health” in humans, several anti-aging strategies have recently been developed. Thus, while the fundamental mechanisms regarding skin aging are known, new substances should be considered for introduction into dermatological treatments. Herein, we describe melatonin and its metabolites as potential “aging neutralizers”. Melatonin, an evolutionarily ancient derivative of serotonin with hormonal properties, is the main neuroendocrine secretory product of the pineal gland. It regulates circadian rhythmicity and also exerts anti-oxidative, anti-inflammatory, immunomodulatory, and anti-tumor capacities. The intention of this review is to summarize changes within skin aging, research advances on the molecular mechanisms leading to these changes, and the impact of the melatoninergic anti-oxidative system controlled by melatonin and its metabolites, targeting the prevention or reversal of skin aging.

Therapeutic Target Analysis and Molecular Mechanism of Melatonin - Treated Leptin Resistance Induced Obesity: A Systematic Study of Network Pharmacology

BACKGROUND

Obesity is a medical problem with an increased risk for other metabolic disorders like diabetes, heart problem, arthritis, etc. Leptin is an adipose tissue-derived hormone responsible for food intake, energy expenditure, etc., and leptin resistance is one of the significant causes of obesity. Excess leptin secretion by poor diet habits and impaired hypothalamic leptin signaling leads to LR. Melatonin a sleep hormone; also possess antioxidant and anti-inflammatory properties. The melatonin can attenuate the complications of obesity by regulating its targets towards LR induced obesity.

AIM

The aim of this study includes molecular pathway and network analysis by using a systems pharmacology approach to identify a potential therapeutic mechanism of melatonin on leptin resistance-induced obesity.

METHODS

The bioinformatic methods are used to find therapeutic targets of melatonin in the treatment of leptin resistance-induced obesity. It includes target gene identification using public databases, Gene ontology, and KEGG pathway enrichment by 'ClusterProfiler' using the R language, network analysis by Cytoscape, and molecular Docking by Autodock.

RESULTS

We obtained the common top 33 potential therapeutic targets of melatonin and LR-induced obesity from the total melatonin targets 254 and common LR obesity targets 212 using the data screening method. They are involved in biological processes related to sleep and obesity, including the cellular response to external stimulus, chemical stress, and autophagy. From a total of 180 enriched pathways, we took the top ten pathways for further analysis, including lipid and atherosclerosis, endocrine, and AGE-RAGE signaling pathway in diabetic complications. The top 10 pathways interacted with the common 33 genes and created two functional modules. Using Cytoscape network analysis, the top ten hub genes (TP53, AKT1, MAPK3, PTGS2, TNF, IL6, MAPK1, ERBB2, IL1B, MTOR) were identified by the MCC algorithm of the CytoHubba plugin. From a wide range of pathway classes, melatonin can reduce LR-induced obesity risks by regulating the major six classes. It includes signal transduction, endocrine system, endocrine and metabolic disease, environmental adaptation, drug resistance antineoplastic, and cardiovascular disease.

CONCLUSION

The pharmacological mechanism of action in this study shows the ten therapeutic targets of melatonin in LR-induced obesity.

Therapeutic potential of melatonin in colorectal cancer: Focus on lipid metabolism and gut microbiota

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies. The occurrence and development of CRC are complicated processes. Obesity and dysbacteriosis have been increasingly regarded as the main risk factors for CRC. Understanding the etiology of CRC from multiple perspectives is conducive to screening for some potential drugs or new treatment strategies to limit the serious side effects of conventional treatment and prolong the survival of CRC patients. Melatonin, a natural indoleamine, is mainly produced by the pineal gland, but it is also abundant in other tissues, including the gastrointestinal tract, retina, testes, lymphocytes, and Harder's glands. Melatonin could participate in lipid metabolism by regulating adipogenesis and lipolysis. Additionally, many studies have focused on the potential beneficial effects of melatonin in CRC, such as promotion of apoptosis; inhibition of cell proliferation, migration, and invasion; antioxidant activity; and immune regulation. Meaningfully, gut microbiota is the main determinant of all aspects of health and disease (including obesity and tumorigenesis). The gut microbiota is of great significance for understanding the relationship between obesity and increased risk of CRC. Although the current understanding of how the melatonin-mediated gut microbiota coordinates a variety of physiological and pathological activities is fairly comprehensive, there are still many unknown topics to be explored in the face of a complex nutritional status and a changeable microbiota. This review summarizes the potential links among melatonin, lipid metabolism, gut microbiota, and CRC to promote the development of melatonin as a preventive and therapeutic agent for CRC.

Membrane Melatonin Receptors Activated Cell Signaling in Physiology and Disease

The pineal hormone melatonin has attracted great scientific interest since its discovery in 1958. Despite the enormous number of basic and clinical studies the exact role of melatonin in respect to human physiology remains elusive. In humans, two high-affinity receptors for melatonin, MT1 and MT2, belonging to the family of G protein-coupled receptors (GPCRs) have been cloned and identified. The two receptor types activate Gi proteins and MT2 couples additionally to Gq proteins to modulate intracellular events. The individual effects of MT1 and MT2 receptor activation in a variety of cells are complemented by their ability to form homo- and heterodimers, the functional relevance of which is yet to be confirmed. Recently, several melatonin receptor genetic polymorphisms were discovered and implicated in pathology-for instance in type 2 diabetes, autoimmune disease, and cancer. The circadian patterns of melatonin secretion, its pleiotropic effects depending on cell type and condition, and the already demonstrated cross-talks of melatonin receptors with other signal transduction pathways further contribute to the perplexity of research on the role of the pineal hormone in humans. In this review we try to summarize the current knowledge on the membrane melatonin receptor activated cell signaling in physiology and pathology and their relevance to certain disease conditions including cancer.

Breast Cancer Risk Among Female Health Professionals: A 35-Year Population-Based Longitudinal Cohort Study in Taiwan

INTRODUCTION

Breast cancer is the most frequently diagnosed cancer among women worldwide. Previous studies have found a higher risk in nurses but no clear relationship among other health professionals. This study aims to investigate the risks of incident breast cancer among female health professionals compared with that among nonhealth professionals in Taiwan.

METHODS

This longitudinal observational cohort study included >35 years (1979-2016) of data from 4 nationwide population-based databases in Taiwan and identified matched cohorts with 1-to-2 propensity score matching between 277,543 health professionals and 555,086 nonhealth professionals. This study calculated total person-years for study subjects and compared breast cancer incidence between matched health and nonhealth professionals. Multivariable Cox proportional hazards and competing risk analyses were used, stratified by birth age, job tenure categories, and types of health professional license. Statistical analyses were conducted in 2019-2020.

RESULTS

Health professionals had a significantly higher risk of breast cancer (hazard ratio=1.34, 95% CI=1.28-1.41; subdistribution hazard ratio=1.36, 95% CI=1.30, 1.42). Elevated risk of breast cancer incidence was associated with birth age, job tenure, and several health professional license types, including physician, pharmacist, registered nurse, midwife, medical technologist, and psychologist.

CONCLUSIONS

Elevated breast cancer risk was found overall in female health professionals. Regular ultrasonography for younger women and mammography for those aged >45 years may be necessary in the annual labor physical examination for female health professionals.

Protective role of melatonin in breast cancer: what we can learn from women with blindness

PURPOSE

This review proposes an overall vision of the protective and therapeutic role of melatonin in breast cancer: from the specific cases of blind women and their reduction of breast cancer incidence to all clinical uses of the sleep hormone in breast cancer.

METHODS

We reviewed studies focused on (1) the correlation between blindness and breast cancer, (2) the correlation between melatonin and breast cancer occurrence in the general population, (3) melatonin therapeutic use in breast cancer, and (4) we discussed the properties of melatonin that could explain an anticancer effect.

RESULTS

(1) Seven studies of breast cancer risk in blind women related significant incidence decreases, up to 57%, among totally blind women. The limited number of studies and the absence of adjustment for confounding factors in most studies limit conclusions. None of these studies established melatonin profiles to determine whether blind women with a decreased breast cancer incidence produced higher levels of melatonin. (2) In the general population, 5 meta-analyses and 12 prospective-cohort studies focused on melatonin levels at recruitment and breast cancer occurrence. All reported the absence of correlation in premenopausal women, whereas in postmenopausal women, most studies showed significantly decreased risk for women with highest melatonin levels. (3) The therapeutic interest of melatonin associated with chemotherapy, radiotherapy, and hormonotherapy is poorly documented in breast cancer to conclude on a positive effect. (4) Melatonin effects on mammary carcinogenesis were only reported in in vitro and animal studies that demonstrated antiestrogenic, antioxidant, oncostatic, and immunomodulatory properties.

CONCLUSION

The preventive role of high endogenous melatonin on breast cancer as well as its beneficial therapeutic use remains to be proven.

Dexmetomidine promotes the activity of breast cancer cells through miR-199a/HIF-1α axis

BACKGROUND

Breast cancer, as one of the most common malignant tumors in women, is still a great threat to women all over the world. Dexmetomidine (DMED) is a highly selective α2-adrenergic receptor agonist, which has attracted much attention in recent years. This study aimed to clarify the potential mechanism of DMED in regulating the activity of breast cancer cells.

METHODS

Breast cancer cell lines MCF-7 and MDA-MB-231 were treated with DMED. The levels of miR-199a and HIF-1α mRNA were detected using quantitative real-time polymerase chain reaction (QRT-PCR); the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and transwell assays were applied to monitor the activity of breast cancer cells; the apoptosis of breast cancer cells was detected using the caspase-3 activity assay and flow cytometry; binding of miR-199a and HIF-1α was assessed using double luciferase reporter gene assay, and western blot was employed to monitor the level of HIF-1α in cells.

RESULTS

The cytotoxicity and apoptosis of MCF-7 and MDA-MB-231 cells was inhibited by DMED. It also downregulated the expression of miR-199a in breast cancer cells and enhanced the downregulation of miR-199a to promote the activity of breast cancer cells and inhibit apoptosis. Also, miR-199a targeted HIF-1α. Further functional experiments confirmed that DMED promoted the progression of breast cancer through the miR-199a/HIF-1α axis.

CONCLUSIONS

DMED promotes the activity of breast cancer cells through miR-199a/HIF-1αaxis. This can provide some reference for DMED in the clinical treatment of breast cancer.

A New Paradigm in the Relationship between Melatonin and Breast Cancer: Gut Microbiota Identified as a Potential Regulatory Agent

In this review we summarize a possible connection between gut microbiota, melatonin production, and breast cancer. An imbalance in gut bacterial population composition (dysbiosis), or changes in the production of melatonin (circadian disruption) alters estrogen levels. On the one hand, this may be due to the bacterial composition of estrobolome, since bacteria with β-glucuronidase activity favour estrogens in a deconjugated state, which may ultimately lead to pathologies, including breast cancer. On the other hand, it has been shown that these changes in intestinal microbiota stimulate the kynurenine pathway, moving tryptophan away from the melatonergic pathway, thereby reducing circulating melatonin levels. Due to the fact that melatonin has antiestrogenic properties, it affects active and inactive estrogen levels. These changes increase the risk of developing breast cancer. Additionally, melatonin stimulates the differentiation of preadipocytes into adipocytes, which have low estrogen levels due to the fact that adipocytes do not express aromatase. Consequently, melatonin also reduces the risk of breast cancer. However, more studies are needed to determine the relationship between microbiota, melatonin, and breast cancer, in addition to clinical trials to confirm the sensitizing effects of melatonin to chemotherapy and radiotherapy, and its ability to ameliorate or prevent the side effects of these therapies.

Implications of Lifestyle and Occupational Factors on the Risk of Breast Cancer in Shiftwork Nurses

Shift work that involves circadian disruption has been highlighted as a likely carcinogenic factor for breast cancer in humans. Also, unhealthy lifestyle habits observed in night work nurses could be causally related to an increase in the incidence of estrogen-positive breast tumours in this population. Assessing baseline risk of breast cancer in nurses is essential. The objective of this study was to analyze the risk of breast cancer that nurses had in relation to their lifestyle and labour factors related to shift work. A cross-sectional descriptive study through a questionnaire about sociodemographic variables, self-perception of health, and working life was designed. The sample consisted of 966 nurses. The relationship between variables was tested. A binary logistic regression and a classification and regression tree were performed. The most significant labour variables in relation to the risk of breast cancer were the number of years worked (more than 16 years; p < 0.01; OR = 8.733, 95% CI = 2.811, 27.134) and the total years performing more than 3 nights per month (10 or more years; p < 0.05; OR = 2.294, 95% CI = 1.008, 5.220). Also, the nights worked throughout life (over 500; OR = 4.190, 95% CI = 2.118, 8.287) were significant in the analysis. Nurses who had or ever had breast cancer valued their self-perceived health more negatively (p < 0.001) and referred a lower quality of sleep (p < 0.001) than the non-cases nurses. The occupational factors derived from night work could have several impacts on nurses' health and their family-work balance. Promoting healthy lifestyles, informing about shift work risks, and adjusting shift work schedules are critical methods to decrease the possible effects of circadian disruption in nurses.

Using dynamic cell communication improves treatment strategies of breast cancer

Several insights from the clinical treatment of breast cancer patients have revealed that only a portion of patients achieve the expected curative effect after traditional targeted therapy, that surgical treatment may promote the development of cancer metastasis, and that the optimal combination of neoadjuvant chemotherapy and traditional treatment is not clear. Therefore, a more precise classification of breast cancer and selection of treatment methods should be undertaken to improve the efficacy of clinical treatment. In the clinical treatment of breast cancer, cell communication molecules are often selected as therapeutic targets. However, various cell communications are not static. Their dynamic changes are related to communicating cells, communicating molecules, and various intertwined internal and external environmental factors. Understanding the dynamic microenvironment can help us improve therapeutic efficacy and provide new ways to more accurately determine the cancer status. Therefore, this review describes multiple types of cellular communication in the breast cancer microenvironment and incorporates internal and external environmental factors as variable signaling factors in cell communication. Using dynamic and developmental concepts, we summarize the functional changes in signaling molecules and cells to aid in the diagnosis and treatment of breast cancer.

A Case Control Study on Serum Levels of Potential Biomarkers in Male Breast Cancer Patients

The global incidence of breast cancer among men is steadily growing. Despite this, compared to female breast cancer patients, there are very few studies on biomarkers in male breast cancer patients. A cross-sectional case control study was carried out to determine the serum levels of melatonin, ghrelin, dopamine, serotonin, epinephrine, and GABA in male breast cancer. All the recruited patients were obese, old, and had recently been diagnosed with the disease. They had not received any treatment for the cancer until the time of the study. Melatonin and epinephrine serum levels were significantly higher in breast cancer patients compared to their age-matched controls, whereas ghrelin, dopamine, GABA, and serotonin serum levels were lower in patients compared to the control group. The serum levels of most of the studied biomarkers in male breast cancer patients were similar to those observed in female breast cancer patients, except for serum melatonin levels.

Night Work and Breast Cancer Risk in Nurses: Multifactorial Risk Analysis

Night work has been highlighted by the International Agency for Research on Cancer (IARC) as a likely carcinogenic factor for humans, associated with breast cancer and professions that require continuity of work. Knowing the impact that short and long-term night work has on the nurses' collective seems a priority, therefore, this study aims to analyse the relationship between night work and the development of breast cancer risk factors in nurses. For this, a cross-sectional study through an online questionnaire on breast cancer risk variables and working life was designed. The study was conducted in Spain and the sample consisted of 966 nurses, of whom 502 were healthy participants and 56 were breast cancer patients. These two groups were compared in the analyses. A descriptive analysis was performed, and the relationship was tested using χ2 independence test and OR calculation. The CHAID (Chi Square Automatic Interaction Detection) data mining method allowed for the creation of a segmentation tree for the main risk variables. The most significant risk variables related to working life have been the number of years worked, nights worked throughout life, and years working more than 3 nights per month. Exceeding 16 years of work has been significant for women and men. When the time worked is less than 16 years, the number of cases increases if there is a family history of cancer and if there have been more than 500 nights of work. High-intensity night work seems more harmful at an early age. The accumulation of years and nights worked increase the risk of breast cancer when factors such as sleep disturbance, physical stress, or family responsibilities come together.

Antioxidants for the Treatment of Breast Cancer: Are We There Yet?

Breast cancer is the most frequent cancer and the leading cause of cancer death in women. Oxidative stress and the generation of reactive oxygen species (ROS) have been related to cancer progression. Compared to their normal counterparts, tumor cells show higher ROS levels and tight regulation of REDOX homeostasis to maintain a low degree of oxidative stress. Traditionally antioxidants have been extensively investigated to counteract breast carcinogenesis and tumor progression as chemopreventive agents; however, there is growing evidence indicating their potential as adjuvants for the treatment of breast cancer. Aimed to elucidate whether antioxidants could be a reality in the management of breast cancer patients, this review focuses on the latest investigations regarding the ambivalent role of antioxidants in the development of breast cancer, with special attention to the results derived from clinical trials, as well as their potential use as plausible agents in combination therapy and their power to ameliorate the side effects attributed to standard therapeutics. Data retrieved herein suggest that antioxidants play an important role in breast cancer prevention and the improvement of therapeutic efficacy; nevertheless, appropriate patient stratification based on “redoxidomics” or tumor subtype is mandatory in order to define the dosage for future standardized and personalized treatments of patients.

Melatonin as an Oncostatic Molecule Based on Its Anti-Aromatase Role in Breast Cancer

Breast cancer is the most common type of cancer. In the developmental stages of breast cancer, estrogens are strongly involved. As estrogen synthesis is regulated by the enzyme aromatase, targeting the activity of this enzyme represents a therapeutic option. The pineal hormone melatonin may exert a suppressive role on aromatase activity, leading to reduced estrogen biosynthesis. A melatonin-mediated decrease in the expression of aromatase promoters and associated genes would provide suitable evidence of this molecule’s efficacy as an aromatase inhibitor. Furthermore, melatonin intensifies radiation-induced anti-aromatase effects and counteracts the unwanted disadvantages of chemotherapeutic agents. In this manner, this review summarizes the inhibitory role of melatonin in aromatase action, suggesting its role as a possible oncostatic molecule in breast cancer.

ASMT Regulates Tumor Metastasis Through the Circadian Clock System in Triple-Negative Breast Cancer

Objective

Triple-negative (PR^-, ER^-, HER-2^-) breast cancer (TNBC) is regarded as more aggressive and more likely to recur after medical care. Emerging evidence has demonstrated that the circadian clock system regulates cell-signaling pathways critical to cancer cell proliferation, survival and metastasis, meaning that it could be a good candidate for TNBC treatment. As such, the aim of the current study was to examine the molecular mechanism by which the circadian clock system contributes to cancer progression in TNBC.

Methods

Cancer cells and primary breast cancer tissues were immunostained for the measurement of circadian clock proteins (CLOCK, BMAL1 and PER1) and acetylserotonin methyltransferase (ASMT). The association between ASMT and clock proteins was assessed using siRNA and Western blot. Transwell assays were used to detect cancer cell migration and invasion while MTT assays were utilized to evaluate cell proliferation.

Results

Circadian clock proteins (CLOCK, BMAL1, and PER1) and ASMT expression were higher in TNBC and triple positive breast cancer (TPBC) compared with para-carcinoma tissues (PCTs). Intriguingly, there was an obvious correlation between circadian clock proteins and ASMT expression in both TPBC and TNBC. Similarly, circadian clock proteins and ASMT were expressed to a greater extent in BT-474 (triple-positive) cells than in MDA-MB-231 (triple-negative) cells. The inhibition of ASMT reduced circadian clock protein levels in both breast cancer cell lines. Further analysis showed that the expression levels of ASMT and circadian clock proteins did not correlate with clinical parameters such as age, tumor size, histologic grade and CK5/6, but increased significantly with lymphatic invasion in TNBC. In agreement with this finding, knockdown of ASMT significantly leads to reductions in migration and invasion in MDA-MB-231 cells. However, over-expression of CLOCK reversed the decreases seen in ASMT inhibited cells.

Conclusion

Our study suggests that ASMT regulates the circadian clock system in breast cancer and inhibition of ASMT reduces the invasiveness of triple-negative breast cancer cells by downregulating clock protein in a certain extent, indicating the potential value of ASMT as a drug target for TNBC treatment.

Melatonin activity and receptor expression in endometrial tissue and endometriosis

STUDY QUESTION

Are melatonin receptors (melatonin receptor 1A (MR1A) and melatonin receptor 1B (MR1B)) expressed in human endometrium and endometriotic tissue, and does melatonin affect endometrial cell proliferation?

SUMMARY ANSWER

Melatonin receptors are expressed in human eutopic endometrium, endometriomas and peritoneal lesions, although to different extents, and melatonin treatment attenuated estradiol-induced endometrial epithelial cell proliferation in culture.

WHAT IS KNOWN ALREADY

Melatonin decreased endometriotic lesion volume in a rat model of endometriosis. Melatonin treatment reduced pain scores in and analgesic use by women with endometriosis.

STUDY DESIGN, SIZE, DURATION

Basic science study using human endometrial tissue and an endometrial epithelial cell line.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Measurement of melatonin receptor expression (mRNA and protein) in women with surgically confirmed endometriosis (endometrioma (n = 20) or peritoneal lesion (n = 11) alone) and women without surgical evidence of endometriosis (control, n = 15). Collection of endometrial and endometriotic tissue samples, gynecologic history and demographic information. Quantification of estradiol (1.0 nM) and melatonin (0.1 nM-1.0 μM) ± estradiol-induced endometrial epithelial cell proliferation in cultures of endometrial epithelial cells (CRL-1671) following 24 and 48 hours of culture.

MAIN RESULTS AND THE ROLE OF CHANCE

MR1A and MR1B were localized by immunohistochemistry in glandular epithelial cells of endometrial biopsies from women with and without endometriosis. Both receptors were expressed in eutopic and ectopic endometrial tissue. mRNA expression of MR1A and MR1B was significantly greater in peritoneal lesions than in either endometriomas or eutopic endometrium. However, protein expression of MR1A was decreased in peritoneal lesions compared to control eutopic endometrium, whereas MR1B expression did not differ between the groups. Melatonin (0.1 nM-1.0 μM) treatment inhibited estradiol (1.0 nM)-induced endometrial epithelial cell proliferation at 48 hours but not 24 hours of culture.

LIMITATIONS, REASONS FOR CAUTION

Beneficial effects of melatonin seen in culture have yet to be comprehensively evaluated in women with endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that melatonin may be useful as an adjunct to current endometriosis treatments.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Canadian Institutes of Health Research (grant MOP142230 to W.G.F.). A.A.M. is supported by a resident research grant through the Physicians Services Incorporated Foundation. The authors have no conflicts of interest.

Melatonin: an endogenous miraculous indolamine, fights against cancer progression

PURPOSE

Melatonin is an amphipathic indolamine molecule ubiquitously present in all organisms ranging from cyanobacteria to humans. The pineal gland is the site of melatonin synthesis and secretion under the influence of the retinohypothalamic tract. Some extrapineal tissues (skin, lens, gastrointestinal tract, testis, ovary, lymphocytes, and astrocytes) also enable to produce melatonin. Physiologically, melatonin regulates various functions like circadian rhythm, sleep-wake cycle, gonadal activity, redox homeostasis, neuroprotection, immune-modulation, and anticancer effects in the body. Inappropriate melatonin secretion advances the aging process, tumorigenesis, visceral adiposity, etc. METHODS: For the preparation of this review, I had reviewed the literature on the multidimensional activities of melatonin from the NCBI website database PubMed, Springer Nature, Science Direct (Elsevier), Wiley Online ResearchGate, and Google Scholar databases to search relevant articles. Specifically, I focused on the roles and mechanisms of action of melatonin in cancer prevention.

RESULTS

The actions of melatonin are primarily mediated by G-protein coupled MT1 and MT2 receptors; however, several intracellular protein and nuclear receptors can modulate the activity. Normal levels of the melatonin protect the cells from adverse effects including carcinogenesis. Therapeutically, melatonin has chronomedicinal value; it also shows a remarkable anticancer property. The oncostatic action of melatonin is multidimensional, associated with the advancement of apoptosis, the arrest of the cell cycle, inhibition of metastasis, and antioxidant activity.

CONCLUSION

The present review has emphasized the mechanism of the anti-neoplastic activity of melatonin that increases the possibilities of the new approaches in cancer therapy.

Anticancer Melatplatin Prodrugs: High Effect and Low Toxicity, MT1-ER-Target and Immune Response In Vivo

Multitargeted therapy could rectify various oncogenic pathways to block tumorigenesis and progression. The combination of endocrine-, immune-, and chemotherapy might exert a highly synergistic effect against certain tumors. Herein, a series of smart Pt(IV) prodrugs 3-6, named Melatplatin, were rationally designed not only to multitarget DNA, MT1, and estrogen receptor (ER) but also to activate immune response. Melatplatin, conjugating first-line chemotherapeutic Pt drugs with human endogenous melatonin (MT), significantly enhanced drug efficacy especially in ER high-expression (ER⁺) cells, among which 3 presented the most potent cytotoxicity toward ER⁺ MCF-7 with nanomolar IC₅₀ values 100-fold lower than cisplatin. Melatplatin could bind well to melatonin receptor (MT1) according to molecular docking. Besides, 3 evidently increased intracellular accumulation and DNA damage, upregulated γH2AX and P53, and silenced NF-κB to induce massive apoptosis. Most strikingly, 3 effectively inhibited tumor growth and attenuated systemic toxicity compared to cisplatin in vivo, promoting lymphocyte proliferation in spleen to achieve immune modulation.

Insights on Melatonin as an Active Pharmacological Molecule in Cancer Prevention: What's New?

Along with playing an important role in circadian rhythm, melatonin is thought to play a significant role in preventing cells from damage, as well as in the inhibition of growth and in triggering apoptosis in malignant cells. Its relationship with circadian rhythms, energetic homeostasis, diet, and metabolism, is fundamental to achieve a better comprehension of how melatonin has been considered a chemopreventive molecule, though very few papers dealing with this issue. In this article, we tried to review the most recent evidence regarding the protective as well as the antitumoral mechanisms of melatonin, as related to diet and metabolic balance. From different studies, it was evident that an intracellular antioxidant defense mechanism is activated by upregulating an antioxidant gene battery in the presence of high-dose melatonin in malignant cells. Like other broad-spectrum antioxidant molecules, melatonin plays a vital role in killing tumor cells, preventing metastasis, and simultaneously keeping normal cells protected from oxidative stress and other types of tissue damage.

Selective autophagy, lipophagy and mitophagy, in the Harderian gland along the oestrous cycle: a potential retrieval effect of melatonin

Sexual dimorphism has been reported in many processes. However, sexual bias in favour of the use of males is very present in science. One of the main reasons is that the impact of hormones in diverse pathways and processes such as autophagy have not been properly addressed in vivo. The Harderian gland is a perfect model to study autophagic modulation as it exhibits important changes during the oestrous cycle. The aim of this study is to identify the main processes behind Harderian gland differences under oestrous cycle and their modulator. In the present study we show that redox-sensitive transcription factors have an essential role: NF-κB may activate SQSTM1/p62 in oestrus, promoting selective types of autophagy: mitophagy and lipophagy. Nrf2 activation in dioestrus, leads the retrieval phase and restoration of mitochondrial homeostasis. Melatonin’s receptors show higher expression in dioestrus, leading to decreases in pro-inflammatory mediators and enhanced Nrf2 expression. Consequently, autophagy is blocked, and porphyrin release is reduced. All these results point to melatonin as one of the main modulators of the changes in autophagy during the oestrous cycle.

Melatonin promotes neuroblastoma cell differentiation by activating hyaluronan synthase 3-induced mitophagy

Neuroblastoma is the second most common pediatric malignancy and has a high rate of spontaneous remission. Uncovering the mechanisms underlying neuroblastoma cell differentiation is critical for therapeutic purposes. A neuroblastoma cell line (N2a) treated with either serum withdrawal (<2.5%) or melatonin (>0.1 nmol/L) for 24 hours was used as a cell differentiation research model. Interestingly, the hyaluronan synthase 3 (HAS3) protein was induced in differentiated N2a cells. N2a-allografted nude mice received an intraperitoneal injection of melatonin (40 or 80 mg/kg/day for 3 weeks). The mean tumor volume in mice treated with 80 mg/kg melatonin was smaller than that in PBS-treated mice (1416.3 and 3041.3 mm³ , respectively, difference = 1625 mm³ , *P = 0.0003, n = 7 per group). Compared with the vector control group, N2a cells with forced HAS3 overexpression showed significantly increased neuron length (*P = 0.00082) and neurite outgrowth (*P = 0.00059). Intracellular changes in autophagy, including distorted mitochondria with abnormal circular inner membranes, were detected by transmission electron microscopy (TEM). Our study demonstrated that HAS3-mediated signaling activated by physiological concentrations of melatonin (>0.1 nmol/L) triggered significant N2a cell differentiation. These results provide molecular data with potential clinical relevance for therapeutic drug development.

Metformin and melatonin improve histopathological outcome of NMU-induced mammary tumors in rats

OBJECTIVE

Numerous reports showed inhibition of carcinogenesis after metformin (MF) and melatonin (MEL) administration. However, most in vivo studies used standard diet type, with relatively low fat content. As increase in fat intake may have a considerable impact on malignant transformation, we evaluated the effects of these two substances in a model of mammary carcinogenesis in rats fed a high-fat diet (10%).

METHODS

Mammary tumors were induced by N-methyl-N-nitrosourea (NMU) in female rats of sensitive Sprague-Dawley strain. MF was administered in a diet (0.2%), MEL was administered in drinking water (20 mg/L). The chemoprevention was initiated 12 days prior to tumor initiation, both substances were administered through the termination of the experiment on 16th week after carcinogen application. Analysis of basic parameters of tumor growth, histopathological profile, and serum IGF-1 level were performed together with immunohistochemical detection of Ki67 (proliferation marker) and caspase-3 and BCL-2 (apoptosis markers) in mammary cancer cells.

RESULTS

Although neither tumor incidence nor frequency were changed after MF and/or MEL administration, MF and MEL decreased high-grade/low-grade (HG/LG) tumor ratio. MEL decreased proliferation in mammary cancer cells; positive correlations between histological grade and Ki67 expressions were found after single administration of both MF and MEL. Serum IGF-1 levels were reduced to the level of intact rats in all groups receiving chemoprevention.

CONCLUSIONS

MF and MEL administration did not inhibit growth of NMU-induced mammary tumors in rats in a significant manner but both substances ameliorated tumor histopathological profile. Surprisingly, combined treatment had no such effect.

Melatonin Synthesis and Function: Evolutionary History in Animals and Plants

Melatonin is an ancient molecule that can be traced back to the origin of life. Melatonin's initial function was likely that as a free radical scavenger. Melatonin presumably evolved in bacteria; it has been measured in both α-proteobacteria and in photosynthetic cyanobacteria. In early evolution, bacteria were phagocytosed by primitive eukaryotes for their nutrient value. According to the endosymbiotic theory, the ingested bacteria eventually developed a symbiotic association with their host eukaryotes. The ingested α-proteobacteria evolved into mitochondria while cyanobacteria became chloroplasts and both organelles retained their ability to produce melatonin. Since these organelles have persisted to the present day, all species that ever existed or currently exist may have or may continue to synthesize melatonin in their mitochondria (animals and plants) and chloroplasts (plants) where it functions as an antioxidant. Melatonin's other functions, including its multiple receptors, developed later in evolution. In present day animals, via receptor-mediated means, melatonin functions in the regulation of sleep, modulation of circadian rhythms, enhancement of immunity, as a multifunctional oncostatic agent, etc., while retaining its ability to reduce oxidative stress by processes that are, in part, receptor-independent. In plants, melatonin continues to function in reducing oxidative stress as well as in promoting seed germination and growth, improving stress resistance, stimulating the immune system and modulating circadian rhythms; a single melatonin receptor has been identified in land plants where it controls stomatal closure on leaves. The melatonin synthetic pathway varies somewhat between plants and animals. The amino acid, tryptophan, is the necessary precursor of melatonin in all taxa. In animals, tryptophan is initially hydroxylated to 5-hydroxytryptophan which is then decarboxylated with the formation of serotonin. Serotonin is either acetylated to N-acetylserotonin or it is methylated to form 5-methoxytryptamine; these products are either methylated or acetylated, respectively, to produce melatonin. In plants, tryptophan is first decarboxylated to tryptamine which is then hydroxylated to form serotonin.

Therapeutic strategies of melatonin in cancer patients: a systematic review and meta-analysis

Background

Melatonin (MLT), a kind of neuroendocrine active substance, has been reported to function in the treatment of tumors. However, there remain controversies about the curative effect of MLT in tumors in clinical studies. This study investigates the efficacy of MLT on tumor therapeutic strategies by meta-analysis.

Methods

After searching several main literature databases, a total of 5,057 articles were obtained and screened by inclusion and exclusion criteria. The tumor remission rate, overall survival rate, and incidence of side effects were recorded and analyzed in the included study patients. Group analysis and sensitivity analysis were performed to examine the sources of heterogeneity in the pooled studies.

Results

The tumor remission rate in the MLT group was significantly higher than that in the control group (relative risk [RR] =2.25; 95% CI, 1.86–2.71; P<0.00001; I²=9%). Likewise, the MLT group had an overall survival rate of 28.24% (n=294/1,041), which was greatly increased compared with the control group (RR =2.07; 95% CI, 1.55–2.76; P<0.00001; I²=55%). And, MLT could significantly enhance the overall survival rate in non-small-cell lung cancer patients (RR =2.13; 95% CI, 1.41–3.24; P=0.0004; I²=0%) and various solid tumor patients (RR =2.31; 95% CI, 1.78–2.99; P<0.00001; I²=0%). It was further proved that MLT could effectively reduce the incidence of neurotoxicity (RR =0.30, 95% CI, 0.19–0.45; P<0.00001), thrombocytopenia (RR =0.23; 95% CI, 0.16–0.33; P<0.00001), and asthenia (RR =0.43, 95% CI, 0.38–0.49; P<0.00001) during chemotherapy.

Conclusion

MLT exerts positive influence in tumor therapeutic strategies, including improving tumor remission rate and overall survival rate, while reducing the incidence of chemotherapy side effects. Further large-scale randomized clinical trials (RCTs) are urgently required to verify therapeutic effects of MLT in tumors by various clinical research centers.

Evaluation of melatonin and AFMK levels in women with breast cancer

PURPOSE

Changes in the circadian rhythm may contribute to the development of cancer and are correlated with the high risk of breast cancer (BC) in night workers. Melatonin is a hormone synthesized by the pineal gland at night in the absence of light. Levels of melatonin and the metabolite of oxidative metabolism AFMK (acetyl-N-formyl-5-methoxykynurenamine), are suggested as potential biomarkers of BC risk. The aims of this study were to evaluate levels of melatonin and AFMK in women recently diagnosed with BC, women under adjuvant chemotherapy, and night-shift nurses, and compare them with healthy women to evaluate the relation of these compounds with BC risk.

METHODS

Blood samples were collected from 47 women with BC, 9 healthy women, 10 healthy night shift nurses, and 6 patients under adjuvant chemotherapy. Compound levels were measured by mass spectrometry.

RESULTS AND CONCLUSIONS

Our results showed that women with BC had lower levels of melatonin compared to control group women, and even lower in night-shift nurses and in patients under adjuvant chemotherapy. There was no significant difference of AFMK levels between the groups. In addition to this, high levels of melatonin and AFMK were related to patients with metastasis, and high levels of AFMK were related to the presence of lymph node-positive, tumor > 20 mm and patients who sleep with light at night. Our results showed a reduction of melatonin levels in BC patients, suggesting a relation with the disease, and in addition, point to the importance of melatonin supplementation in women that work at night to reduce the BC risk.