Melatonin as a potential anticarcinogen for non-small-cell lung cancer

Natural Compounds for Preventing Age-Related Diseases and Cancers

Aging is a multifaceted process influenced by hereditary factors, lifestyle, and environmental elements. As time progresses, the human body experiences degenerative changes in major functions. The external and internal signs of aging manifest in various ways, including skin dryness, wrinkles, musculoskeletal disorders, cardiovascular diseases, diabetes, neurodegenerative disorders, and cancer. Additionally, cancer, like aging, is a complex disease that arises from the accumulation of various genetic and epigenetic alterations. Circadian clock dysregulation has recently been identified as an important risk factor for aging and cancer development. Natural compounds and herbal medicines have gained significant attention for their potential in preventing age-related diseases and inhibiting cancer progression. These compounds demonstrate antioxidant, anti-inflammatory, anti-proliferative, pro-apoptotic, anti-metastatic, and anti-angiogenic effects as well as circadian clock regulation. This review explores age-related diseases, cancers, and the potential of specific natural compounds in targeting the key features of these conditions.

Melatonin Inhibits AGS Cell Proliferation by Binding to the ATP Binding Site of CDK2 Under Hyperglycemic Conditions

Cancer cells utilize glucose as their primary energy source. The aggressive nature of cancer cells is therefore enhanced in hyperglycemic conditions. This study has been adopted to investigate the therapeutic potential of melatonin against such aggressive proliferation of AGS cells-a human gastric cancer cell line, under hyperglycemic conditions. AGS cells were incubated with high glucose-containing media, and the effects of melatonin have been evaluated, therein. Cell proliferation, ROS generation, flow-cytometric analysis for cell cycle and apoptosis, wound healing, immunoblotting, zymography, reverse zymography assays, in-silico analysis, and kinase activity assays were performed to evaluate the effects of melatonin. We observed that melatonin inhibited the hyperglycemia-induced cell proliferation in a dose-dependent manner. It further altered the expression and activity of MMP-9 and TIMP-1. Moreover, melatonin inhibited AGS cell proliferation by arresting AGS cells in the G0/G1 phase after binding in the ATP binding site of CDK-2, thereby inhibiting its kinase activity. In association, a significant decrease in the expression of cyclin D1, cyclin E, CDK-4, and CDK-2 were observed. In conclusion, these findings suggest that melatonin has anti-gastric cancer potential. Melatonin could therefore be included in future drug designs for gastric cancer-hyperglycemia co-morbidity treatment.

Poor sleep quality association with higher lung cancer risk: a nested case-control study

Background

Little is known about the relationship between sleep quality and lung cancer incidence. Thus, this study was conducted to investigate the potential connection between sleep quality and lung cancer incidence.

Methods

We performed and selected a nested case-control study that included 150 lung cancer cases and 150 matched controls based on the Lianyungang cohort. Univariate and multivariate logistic regression was utilized to investigate the connection between potential risk factors and lung cancer incidence risk.

Results

In this study, the average age of participants was 66.5 ± 9.1 years, with 58.7% being male, and 52.7% reportedly experiencing sleep quality problems. The results of multivariate logistic regression showed that poor sleep quality was connected to an increased lung cancer incidence risk (P = 0.033, odds ratio = 1.83, 95% confidence interval = [1.05-3.19]) compared with those with good sleep quality. The stratified analyses showed a significantly positive connection between poor sleep quality (vs. good sleep quality) and cancer risk in smokers (vs. non-smoker, P for interaction = 0.085). The combined effect analysis indicated that smokers with poor sleep quality suffered from a 2.79-fold increase in cancer incidence rates when compared with non-smokers with good sleep quality.

Conclusions

Poor sleep quality was positively connected to an increased lung cancer incidence risk. In addition, among those individuals with poor sleep quality, smoking increased the lung cancer incidence risk.

The Preventive Effect of Melatonin on Radiation-Induced Oral Mucositis

Melatonin exerts various physiological effects through melatonin receptors and their ability to scavenge free radicals. Radiotherapy is a common treatment for head and neck tumors, but stomatitis, a side effect affecting irradiated oral mucosa, can impact treatment outcomes. This study investigated the preventive effect of melatonin, a potent free radical scavenger, on radiation-induced oral mucositis. Mice were irradiated with 15 Gy of X-ray radiation to the head and neck, and the oral mucosa was histologically compared between a melatonin-administered group and a control group. The results showed that radiation-induced oral mucositis was suppressed in mice administered melatonin before and after irradiation. It was suggested that the mechanism involved the inhibition of apoptosis and the inhibition of DNA damage. From these findings, we confirmed that melatonin has a protective effect against radiation-induced oral mucositis.

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.

Sleep Traits, Night Shift Work and Lung Cancer Risk among Women: Results from a Population-Based Case-Control Study in France (The WELCA Study)

Circadian rhythm disruption due to night shift work and/or sleep disorders is associated with negative health outcomes including cancer. There is only scant evidence of an association with lung cancer, unlike breast and prostate cancer. We explore the role of sleep disorders and night shift work in lung cancer risk among women in a population-based case-control study, including 716 lung cancer cases and 758 controls. Multivariable logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) associated with sleep duration per day (<7 h, 7−7.9 h, ≥8 h), a summary index of sleep disorders, chronotype, and night shift work exposure metrics. When compared to women with an average sleep duration of 7−7.9 h per day, the OR was 1.39 (95% CI 1.04−1.86) in long sleepers (≥8 h) and 1.16 (95% CI 0.86−1.56) in short sleepers (<7 h). Overall, lung cancer was not associated with the sleep disorder index, nor with night shift work, regardless of the duration of night work or the frequency of night shifts. However, elevated OR associated with the sleep disorder index were found in the subgroup of current smokers. The U-shaped association of lung cancer with sleep duration was more particularly pronounced among women who worked at night ≥5 years. Our findings suggested that sleep patterns are associated with lung cancer risk in women with a potential modifying effect by night shift work duration or tobacco smoking.

The ubiquitin-specific protease 8 antagonizes melatonin-induced endocytic degradation of MT1 receptor to promote lung adenocarcinoma growth

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Melatonin can induce the downregulation of the MT₁ receptor.

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MT₁ receptor internalization incurred by melatonin follows the canonical endolysosomal pathway.

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The ubiquitin-specific protease 8 antagonizes the endocytic degradation of the MT₁ receptor.

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The suppression of ubiquitin-specific protease 8 potentiates the cancer-inhibitory effects of melatonin in vitro.

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Combination of USP8 inhibition and melatonin treatment effectively deters tumor growth in xenograft mouse models.

Introduction

The human genome encodes two melatonin receptors (MT₁ and MT₂) that relay melatonin signals to cellular interior. Accumulating evidence has linked melatonin to multiple health benefits, among which its anticancer effects have become well-established. However, the implications of its receptors in lung adenocarcinoma have so far remained incompletely understood.

Objectives

This study aims to investigate the response of the MT₁ receptor to melatonin treatment and its dynamic regulation by ubiquitin-specific protease 8 (USP8) in lung adenocarcinoma.

Methods

The mRNA levels of MT₁ and MT₂ receptors were analyzed with sequencing data. The expression and localization of the MT₁ receptor with melatonin treatment were investigated by immunoblotting, immunofluorescence and confocal microscopy assays. Endocytic deubiquitylases were screened to identify MT₁ association. The effects of USP8 were assessed with shRNA-mediated knockdown and small molecule inhibitor. The combined efficacy of melatonin and USP8 suppression was also evaluated using xenograft animal models.

Results

Bioinformatic analysis revealed increased expression of the MT₁ receptor in lung adenocarcinoma tissues. Melatonin treatment leads to the downregulation of the MT₁ receptor in lung adenocarcinoma cells, which is attributed to receptor endocytosis and lysosomal degradation via the canonical endo-lysosomal route. USP8 negatively regulates the endocytic degradation of the MT₁ receptor incurred by melatonin exposure and thus protects lung adenocarcinoma cell growth. USP8 suppression by knockdown or pharmacological inhibition effectively deters cancer cell proliferation and sensitizes lung adenocarcinoma cells to melatonin in vitro. Furthermore, USP8 silencing significantly potentiates the anticancer effects of melatonin in xenograft tumor models.

Conclusion

The MT₁ receptor responds to melatonin treatment and is endocytosed for lysosomal degradation that is counteracted by USP8. The inhibition of USP8 demonstrates tumor-suppressive effects and thus can be exploited as potential therapeutic strategy either as monotherapy or combined therapy with melatonin.

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.

Melatonin: A smart molecule in the DNA repair system

DNA repair is an important pathway for the protection of DNA molecules from destruction. DNA damage can be produced by oxidative reactive nitrogen or oxygen species, irritation, alkylating agents, depurination and depyrimidination; in this regard, DNA repair pathways can neutralize the negative effects of these factors. Melatonin is a hormone secreted from the pineal gland with an antioxidant effect by binding to oxidative factors. In addition, the effect of melatonin on DNA repair pathways has been proven by the literature. DNA repair is carried out by several mechanisms, of which homologous recombination repair (HRR) and non-homologous end-joining (NHEJ) are of great importance. Because of the importance of DNA repair in DNA integrity and the anticancer effect of this pathway, we presented the effect of melatonin on DNA repair factors regarding previous studies conducted in this area.

Mechanistic Insights of Anti-Immune Evasion by Nobiletin through Regulating miR-197/STAT3/PD-L1 Signaling in Non-Small Cell Lung Cancer (NSCLC) Cells

Tumor immune escape is a common process in the tumorigenesis of non-small cell lung cancer (NSCLC) cells where programmed death ligand-1 (PD-L1) expression, playing a vital role in immunosuppression activity. Additionally, epidermal growth factor receptor (EGFR) phosphorylation activates Janus kinase-2 (JAK2) and signal transduction, thus activating transcription 3 (STAT3) to results in the regulation of PD-L1 expression. Chemotherapy with commercially available drugs against NSCLC has struggled in the prospect of adverse effects. Nobiletin is a natural flavonoid isolated from the citrus peel that exhibits anti-cancer activity. Here, we demonstrated the role of nobiletin in evasion of immunosuppression in NSCLC cells by Western blotting and real-time polymerase chain reaction methods for molecular signaling analysis supported by gene silencing and specific inhibitors. From the results, we found that nobiletin inhibited PD-L1 expression through EGFR/JAK2/STAT3 signaling. We also demonstrated that nobiletin exhibited p53-independent PD-L1 suppression, and that miR-197 regulates the expression of STAT3 and PD-L1, thereby enhancing anti-tumor immunity. Further, we evaluated the combination ability of nobiletin with an anti-PD-1 monoclonal antibody in NSCLC co-culture with peripheral blood mononuclear cells. Similarly, we found that nobiletin assisted the induction of PD-1/PD-L1 blockade, which is a key factor for the immune escape mechanism. Altogether, we propose nobiletin as a modulator of tumor microenvironment for cancer immunotherapy.

Melatonin inhibits lung cancer development by reversing the Warburg effect via stimulating the SIRT3/PDH axis

Recently, the morbidity and mortality from lung cancer have continued to increase. Mitochondrial dysfunction plays a key role in apoptosis, proliferation, and the bioenergetic reprogramming of cancer cells, especially for energy metabolism. Herein, we investigated the ability of melatonin (MLT) to influence lung cancer growth and explored the association between mitochondrial functions and the progression of lung tumors. The deacetylase, sirtuin 3 (Sirt3), is a pivotal player in maintenance of mitochondrial function, among participating in ATP production by regulating the acetylone and pyruvate dehydrogenase complex (PDH). We initially found that MLT inhibited lung cancer growth in the Lewis mouse model. Similarly, we observed that MLT inhibited the proliferation of lung cancer cells (A549, PC9, and LLC cells), and the underlying mechanism of MLT was related to reprogramming cancer cell metabolism, accompanied by a shift from cytosolic aerobic glycolysis to oxidative phosphorylation (OXPHOS). These changes were accompanied by higher ATP production, an elevated ATP production-coupled oxygen consumption rate (QCR), higher ROS levels, higher mito-ROS levels, and lower lactic acid secretion. Additionally, we observed that MLT improved mitochondrial membrane potential and the activities of complexes Ⅰ and Ⅳ in the electron transport chain. Importantly, we also found and verified that the foregoing changes resulted from activation of Sirt3 and PDH. As a result of these changes, MLT significantly enhanced mitochondrial energy metabolism to reverse the Warburg effect via increasing PDH activity with stimulation of Sirt3. Collectively, these findings suggest the potential use of melatonin as an anti-lung cancer therapy and provide a mechanistic basis for this proposal.

Detection of Serotonin, Melatonin, and Their Metabolites in Honey

Melatonin and serotonin, products of tryptophan metabolism, are endogenous neurotransmitters and hormones. We have identified and quantified these metabolites in natural honey from Australia, USA, and Poland using a Xevo G2 XS qTof LC-MS. To help ensure correct product identification, some samples were prepurified by RP-HPLC based on the retention times of standards, prior to LC-MS. The concentrations of the metabolites of interest depended on the source of the honey. For Australian honey, levels for melatonin and 2-hydroxymelatonin were 0.91 and 0.68 ng/g, respectively. Melatonin was detected in one brand of US commercial honey at 0.48 ng/g, while a second brand contained serotonin at 88.2 ng/g. In Polish natural honey, 20.6 ng/g of serotonin and 40.8 ng/g of N-acetylserotonin (NAS) were detected, while in Polish commercial honey 25.9 ng/g of serotonin and 7.30 ng/g of NAS were present. We suggest that addictive and health-related properties of honey may be in part dependent on the presence of serotonin, melatonin, and their metabolites, and that these compounds may play a role in the colony activities of bees.

Immunomodulation: An immune regulatory mechanism in carcinoma therapeutics

Cancer has been generally related to the possession of numerous mutations which interrupt important signaling pathways. Nevertheless, deregulated immunological signaling is considered as one of the key factors associated with the development and progression of cancer. The signaling pathways operate as modular network with different components interacting in a switch-like fashion with two proteins interplaying between each other leading to direct or indirect inhibition or stimulation of down-stream factors. Genetic, epigenetic, and transcriptomic alterations maintain the pathological conduit of different signaling pathways via affecting diverse mechanisms including cell destiny. At present, immunotherapy is one of the best therapies opted for cancer treatment. The cancer immunotherapy strategy includes harnessing the specificity and killing mechanisms of the immunological system to target and eradicate malignant cells. Targeted therapies utilizing several little molecules including Galunisertib, Astragaloside-IV, Melatonin, and Jervine capable of regulating key signaling pathways can effectively help in the management of different carcinomas.

Melatonin in Cancer Treatment: Current Knowledge and Future Opportunities

Melatonin is a pleotropic molecule with numerous biological activities. Epidemiological and experimental studies have documented that melatonin could inhibit different types of cancer in vitro and in vivo. Results showed the involvement of melatonin in different anticancer mechanisms including apoptosis induction, cell proliferation inhibition, reduction in tumor growth and metastases, reduction in the side effects associated with chemotherapy and radiotherapy, decreasing drug resistance in cancer therapy, and augmentation of the therapeutic effects of conventional anticancer therapies. Clinical trials revealed that melatonin is an effective adjuvant drug to all conventional therapies. This review summarized melatonin biosynthesis, availability from natural sources, metabolism, bioavailability, anticancer mechanisms of melatonin, its use in clinical trials, and pharmaceutical formulation. Studies discussed in this review will provide a solid foundation for researchers and physicians to design and develop new therapies to treat and prevent cancer using melatonin.

Role of NLRP3 inflammasome in COVID-19 and periodontitis: Possible protective effect of melatonin

Daily new information emerges regarding the COVID-19, infection of SARS-CoV-2, which is considered a global pandemic. Angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) are required to complete the viral invasion pathway and are present in the oral mucosa, gingiva and periodontal pocket. Thus, increasing the likelihood of periodontitis and gingivitis caused by COVID-19. The cytokine storm during COVID-19 similarly arises during periodontal inflammation. Studies have reported that NOD-Like Receptor family pyrin domain-containing 3 (NLRP3) inflammasome is significant in the cytokine storm. Recently, the course of the COVID-19 has been related to the melatonin levels in both COVID-19 and periodontal diseases. It is known that melatonin prevents the activation of NLRP3 inflammasome. In light of these findings, we think that melatonin treatment during COVID-19 or periodontal diseases may prevent the damage seen in periodontal tissues by preventing the activation of NLRP3 inflammasome.

4sc-202 and Ink-128 cooperate to reverse the epithelial to mesenchymal transition in OSCC

Treatment of oral squamous cell carcinoma remains a challenge due to a high incidence of treatment resistance, which is followed by tumor recrudescence and metastasis to the lymph nodes. Thus, it is important to explore novel inhibitors of OSCC. Here, we aimed to identify drugs that may cooperate with histone deacetylase inhibitors to reverse the EMT, inhibit EMT and cell migration and invasion, and contribute to therapeutic efficacy. We found that treatment with 4sc-202 potently reversed the EMT and thereby inhibited cell migration and invasion in vitro, in part by inducing expression of the FoxO1 tumor-suppressor gene. Furthermore, 4sc-202 also synergized with Ink-128 to inhibit tumor migration and invasion in vitro. Mechanistically, 4sc-202 induced FoxO1 expression, whereas Ink-128 promoted nuclear translocation of FoxO1. Our findings indicated that FoxO1 might reverse the EMT by interacting with Twist1 in OSCC. In conclusion, we identified an effective combination therapy involving class I histone deacetylase and mammalian target of rapamycin complex 1/2 inhibition that effectively blocked the EMT of tumor cells by upregulating FoxO1 expression to inhibit Twist1 transcription. These data have implications for developing new targets for early diagnosis and treatment of OSCC.

The inhibitory effect of melatonin on human prostate cancer

Prostate cancer (PCa) is one of the most commonly diagnosed human cancers in males. Nearly 191,930 new cases and 33,330 new deaths of PCa are estimated in 2020. Androgen and androgen receptor pathways played essential roles in the pathogenesis of PCa. Androgen depletion therapy is the most used therapies for primary PCa patients. However, due to the high relapse and mortality of PCa, developing novel noninvasive therapies have become the focus of research. Melatonin is an indole-like neurohormone mainly produced in the human pineal gland with a prominent anti-oxidant property. The anti-tumor ability of melatonin has been substantially confirmed and several related articles have also reported the inhibitory effect of melatonin on PCa, while reviews of this inhibitory effect of melatonin on PCa in recent 10 years are absent. Therefore, we systematically discuss the relationship between melatonin disruption and the risk of PCa, the mechanism of how melatonin inhibited PCa, and the synergistic benefits of melatonin and other drugs to summarize current understandings about the function of melatonin in suppressing human prostate cancer. We also raise several unsolved issues that need to be resolved to translate currently non-clinical trials of melatonin for clinic use. We hope this literature review could provide a solid theoretical basis for the future utilization of melatonin in preventing, diagnosing and treating human prostate cancer.

The melatonergic pathway and its interactions in modulating respiratory system disorders

Melatonin is a key intracellular neuroimmune-endocrine regulator and coordinator of multiple complex and interrelated biological processes. The main functions of melatonin include the regulation of neuroendocrine and antioxidant system activity, blood pressure, rhythms of the sleep-wake cycle, the retardation of ageing processes, as well as reseting and optimizing mitochondria and thereby the cells of the immune system. Melatonin and its agonists have therefore been mooted as a treatment option across a wide array of medical disorders. This article reviews the role of melatonin in the regulation of respiratory system functions under normal and pathological conditions. Melatonin can normalize the structural and functional organization of damaged lung tissues, by a number of mechanisms, including the regulation of signaling molecules, oxidant status, lipid raft function, optimized mitochondrial function and reseting of the immune response over the circadian rhythm. Consequently, melatonin has potential clinical utility for bronchial asthma, chronic obstructive pulmonary disease, lung cancer, lung vascular diseases, as well as pulmonary and viral infections. The integration of melatonin's effects with the alpha 7 nicotinic receptor and the aryl hydrocarbon receptor in the regulation of mitochondrial function are proposed as a wider framework for understanding the role of melatonin across a wide array of diverse pulmonary disorders.

Anti-Warburg Effect of Melatonin: A Proposed Mechanism to Explain its Inhibition of Multiple Diseases

Glucose is an essential nutrient for every cell but its metabolic fate depends on cellular phenotype. Normally, the product of cytosolic glycolysis, pyruvate, is transported into mitochondria and irreversibly converted to acetyl coenzyme A by pyruvate dehydrogenase complex (PDC). In some pathological cells, however, pyruvate transport into the mitochondria is blocked due to the inhibition of PDC by pyruvate dehydrogenase kinase. This altered metabolism is referred to as aerobic glycolysis (Warburg effect) and is common in solid tumors and in other pathological cells. Switching from mitochondrial oxidative phosphorylation to aerobic glycolysis provides diseased cells with advantages because of the rapid production of ATP and the activation of pentose phosphate pathway (PPP) which provides nucleotides required for elevated cellular metabolism. Molecules, called glycolytics, inhibit aerobic glycolysis and convert cells to a healthier phenotype. Glycolytics often function by inhibiting hypoxia-inducible factor-1α leading to PDC disinhibition allowing for intramitochondrial conversion of pyruvate into acetyl coenzyme A. Melatonin is a glycolytic which converts diseased cells to the healthier phenotype. Herein we propose that melatonin's function as a glycolytic explains its actions in inhibiting a variety of diseases. Thus, the common denominator is melatonin's action in switching the metabolic phenotype of cells.

Worldwide melatonin research: a bibliometric analysis of the published literature between 2015 and 2019

This study presents a bibliometric analysis of the publications on melatonin research from the Scopus database during the period 2015-2019. Based on the keywords used, which are related to melatonin in the article title, the study retrieved 4411 documents for further analysis using various tools. We used Microsoft Excel to conduct the frequency analysis, VOSviewer for data visualization, and Harzing's Publish or Perish for citation metrics and analysis. This study reports the results using standard bibliometric indicators such as the growth of publications, authorship patterns, collaboration, and prolific authors, country contribution, most active institutions, preferred journals, and top-cited articles. Based on our findings, there is a continuous growth of publications on melatonin research for 5 years since 2015. China was the largest contributor to melatonin research, followed by the United States. The Journal of Pineal Research published the most number of publications related to melatonin research. Our findings suggest that the role of melatonin in plant and food sciences, as well as in cancer, may in later years take over the clusters that earlier dominated melatonin research.

New insights into antimetastatic signaling pathways of melatonin in skeletomuscular sarcoma of childhood and adolescence

Melatonin is an indole produced by the pineal gland at night under normal light or dark conditions, and its levels, which are higher in children than in adults, begin to decrease prior to the onset of puberty and continue to decline thereafter. Apart from circadian regulatory actions, melatonin has significant apoptotic, angiogenic, oncostatic, and antiproliferative effects on various cancer cells. Particularly, the ability of melatonin to inhibit skeletomuscular sarcoma, which most commonly affects children, teenagers, and young adults, is substantial. In the past few decades, the vast majority of references have focused on the concept of epithelial-mesenchymal transition involvement in invasion and migration to allow carcinoma cells to dissociate from each other and to degrade the extracellular matrix. Recently, researchers have applied this idea to sarcoma cells of mesenchymal origin, e.g., osteosarcoma and Ewing sarcoma, with their ability to initiate the invasion-metastasis cascade. Similarly, interest of the effects of melatonin has shifted from carcinomas to sarcomas. Herein, in this state-of-the-art review, we compiled the knowledge related to the molecular mechanism of antimetastatic actions of melatonin on skeletomuscular sarcoma as in childhood and during adolescence. Utilization of melatonin as an adjuvant with chemotherapeutic drugs for synergy and fortification of the antimetastatic effects for the reinforcement of therapeutic actions are considered.

Melatonin as a potential inhibitor of kidney cancer: A survey of the molecular processes

Studies have shown that despite the decreasing mortality rates of kidney cancer patients, its incidence is increasing. Therefore, a comprehensive re-evaluation of treatment options is necessary to provide appropriate treatments for the increasing number of patients. Moreover, the side effects caused by surgery, which is the main treatment of this disease, may lead to higher morbidity rates. Consequently, new safer approaches must be examined and considered. Major advancements have been made in the field of targeted agents as well as treatments based on immunotherapy since renal cell carcinoma (RCC) does not respond well to chemotherapy. While the therapeutic options for this cancer are increasing, the resulting complexity of selecting the best strategy for treating the patients is daunting. Moreover, each therapeutic option must be evaluated concerning toxicity, cost, and clinical advantages. Several characteristics, which are beneficial for cancer therapies have been attributed to melatonin. For decades, investigations have explored the application of melatonin in the treatment of cancer; insufficient attention has been paid to this molecule at the clinical level. Melatonin plays a role in cancer therapy due to its anti-tumor effects as well as by enhancing the efficacy of other drugs as an adjuvant. In this review, we discuss different roles of melatonin in the treatment of kidney cancer. The studies concerned with the applications of melatonin as an adjuvant in the immunotherapy of patients with kidney cancer are summarized. Also, we highlight the apoptotic and anti-angiogenic effects of melatonin on renal cancer cells which are mediated by different molecules (e.g., HIF-1 and VEGF, ADAMTS1, and MMP-9) and signaling pathways (e.g., P56, P52, and JNK). Furthermore, we take a look into available data on melatonin's ability to reduce the toxicities caused by kidney carcinogens, including ochratoxin A, potassium bromate, and Fe-NTA.

Melatonin inhibits Warburg-dependent cancer by redirecting glucose oxidation to the mitochondria: a mechanistic hypothesis

Melatonin has the ability to intervene in the initiation, progression and metastasis of some experimental cancers. A large variety of potential mechanisms have been advanced to describe the metabolic and molecular events associated with melatonin's interactions with cancer cells. There is one metabolic perturbation that is common to a large number of solid tumors and accounts for the ability of cancer cells to actively proliferate, avoid apoptosis, and readily metastasize, i.e., they use cytosolic aerobic glycolysis (the Warburg effect) to rapidly generate the necessary ATP required for the high metabolic demands of the cancer cells. There are several drugs, referred to as glycolytic agents, that cause cancer cells to abandon aerobic glycolysis and shift to the more conventional mitochondrial oxidative phosphorylation for ATP synthesis as in normal cells. In doing so, glycolytic agents also inhibit cancer growth. Herein, we hypothesize that melatonin also functions as an inhibitor of cytosolic glycolysis in cancer cells using mechanisms, i.e., downregulation of the enzyme (pyruvate dehydrogenase kinase) that interferes with the conversion of pyruvate to acetyl CoA in the mitochondria, as do other glycolytic drugs. In doing so, melatonin halts the proliferative activity of cancer cells, reduces their metastatic potential and causes them to more readily undergo apoptosis. This hypothesis is discussed in relation to the previously published reports. Whereas melatonin is synthesized in the mitochondria of normal cells, we hypothesize that this synthetic capability is not present in cancer cell mitochondria because of the depressed acetyl CoA; acetyl CoA is necessary for the rate limiting enzyme in melatonin synthesis, arylalkylamine-N-acetyltransferase. Finally, the ability of melatonin to switch glucose oxidation from the cytosol to the mitochondria also explains how tumors that become resistant to conventional chemotherapies are re-sensitized to the same treatment when melatonin is applied.

Association Between Night-Shift Work and Cancer Risk: Updated Systematic Review and Meta-Analysis

Background: Nightshift work introduces light at night and causes circadian rhythm among night workers, who are considered to be at increased risk of cancer. However, in the last 2 years, nine population-based studies reported insignificant associations between night-shift work and cancer risks. We aimed to conduct an updated systematic review and meta-analysis to ascertain the effect of night-shift work on the incidence of cancers. Methods: Our protocol was registered in PROSPERO and complied with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Embase, PubMed, and Web of Science databases were used to comprehensively search studies published up to May 31, 2019. The random-effect model (Der Simonian-Laird method) was carried out to combine the risk estimates of night-shift work for cancers. The dose-response meta-analysis was performed to verify whether the association was in a dose-dependent manner. Results: Our literature searching retrieved 1,660 publications. Included in the meta-analyses were 57 eligible studies with 8,477,849 participants (mean age 55 years; 2,560,886 men, 4,220,154 women, and 1,696,809 not mentioned). The pooled results showed that night-shift work was not associated with the risk of breast cancer (OR = 1.009, 95% CI = 0.984-1.033), prostate cancer (OR = 1.027, 95% CI = 0.982-1.071), ovarian cancer (OR = 1.027, 95% CI = 0.942-1.113), pancreatic cancer (OR = 1.007, 95% CI = 0.910-1.104), colorectal cancer (OR = 1.016, 95% CI = 0.964-1.068), non-Hodgkin's lymph (OR = 1.046, 95% CI = 0.994-1.098), and stomach cancer (OR = 1.064, 95% CI = 0.971-1.157), while night-shift work was associated with a reduction of lung cancer (OR = 0.949, 95% CI = 0.903-0.996), and skin cancer (OR = 0.916, 95% CI = 0.879-0.953). The dose-response meta-analysis found that cancer risk was not significantly elevated with the increased light exposure of night- shift work. Conclusion: This systematic review of 57 observational studies did not find an overall association between ever-exposure to night-shift work and the risk of breast, prostate ovarian, pancreatic, colorectal, non-Hodgkin's lymph, and stomach cancers.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

Meroterpenoids from the Brown Alga Cystoseira usneoides as Potential Anti-Inflammatory and Lung Anticancer Agents

The anti-inflammatory and anticancer properties of eight meroterpenoids isolated from the brown seaweed Cystoseira usneoides have been evaluated. The algal meroterpenoids (AMTs) 1-8 were tested for their inhibitory effects on the production of the pro-inflammatory cytokines tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), and the expression of cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) in LPS-stimulated THP-1 human macrophages. The anticancer effects were assessed by cytotoxicity assays against human lung adenocarcinoma A549 cells and normal lung fibroblastic MRC-5 cells, together with flow cytometry analysis of the effects of these AMTs on different phases of the cell cycle. The AMTs 1-8 significantly reduced the production of TNF-α, IL-6, and IL-1β, and suppressed the COX-2 and iNOS expression, in LPS-stimulated cells (p < 0.05). The AMTs 1-8 displayed higher cytotoxic activities against A549 cancer cells than against MRC-5 normal lung cells. Cell cycle analyses indicated that most of the AMTs caused the arrest of A549 cells at the G2/M and S phases. The AMTs 2 and 5 stand out by combining significant anti-inflammatory and anticancer activities, while 3 and 4 showed interesting selective anticancer effects. These findings suggest that the AMTs produced by C. usneoides may have therapeutic potential in inflammatory diseases and lung cancer.

The Inhibitory Mechanisms of Tumor PD-L1 Expression by Natural Bioactive Gallic Acid in Non-Small-Cell Lung Cancer (NSCLC) Cells

Non-small-cell lung cancer (NSCLC) is the most common lung cancer subtype and accounts for more than 80% of all lung cancer cases. Epidermal growth factor receptor (EGFR) phosphorylation by binding growth factors such as EGF activates downstream prooncogenic signaling pathways including KRAS-ERK, JAK-STAT, and PI3K-AKT. These pathways promote the tumor progression of NSCLC by inducing uncontrolled cell cycle, proliferation, migration, and programmed death-ligand 1 (PD-L1) expression. New cytotoxic drugs have facilitated considerable progress in NSCLC treatment, but side effects are still a significant cause of mortality. Gallic acid (3,4,5-trihydroxybenzoic acid; GA) is a phenolic natural compound, isolated from plant derivatives, that has been reported to show anticancer effects. We demonstrated the tumor-suppressive effect of GA, which induced the decrease of PD-L1 expression through binding to EGFR in NSCLC. This binding inhibited the phosphorylation of EGFR, subsequently inducing the inhibition of PI3K and AKT phosphorylation, which triggered the activation of p53. The p53-dependent upregulation of miR-34a induced PD-L1 downregulation. Further, we revealed the combination effect of GA and anti-PD-1 monoclonal antibody in an NSCLC-cell and peripheral blood mononuclear-cell coculture system. We propose a novel therapeutic application of GA for immunotherapy and chemotherapy in NSCLC.

Self-reported sleep quality as prognostic for survival in lung cancer patients

Purpose

Sleep is essential for life, as well as having a major impact on quality of life. Not much attention has been given to this important factor in the care of lung cancer patients.

Patients and Methods

We retrospectively analyzed a cohort of 404 lung cancer patients treated in our institute between 2010 and 2018. Data about sleep quality, distress and pain were self-reported by questionnaires administered to patients at their first clinic visit to the Institute of Oncology. Sex, age, histology, stage, smoking and marital status were extracted from the patients’ charts. Uni- and multi-variate analyses were carried out to evaluate the correlation of these factors with survival.

Results

Most patients reported some level of distress and pain. Sleep abnormalities were reported by 58.7% of patients. Distress, pain and bad sleep were correlated with shorter survival in univariate analyses; however, only sleep remained associated with survival in multivariate analysis. Patients reporting bad sleep had a median survival of 16 months, compared to 27 months for patients reporting good sleep (hazard ratio 1.83, 95% C.I. 1.27–2.65). Frequent arousals at night were more tightly correlated with survival than difficulty falling asleep.

Conclusion

Sleep quality, as reported by lung cancer patients, is highly correlated with survival. Further studies are required to comprehend whether poor sleep quality is directly impacting survival or is a result of the cancer aggressiveness and patients’ conditions.

The Protective Effects of Melatonin Against LPS-Induced Septic Myocardial Injury: A Potential Role of AMPK-Mediated Autophagy

Aim: Melatonin is an indolamine secreted by the pineal gland, as well as most of the organs and tissues. In addition to regulating circadian biology, studies have confirmed the multiple pharmacological effects of melatonin. Melatonin provides a strong defense against septic myocardial injury. However, the underlying mechanism has not been fully described. In this study, we investigated the protective effects of melatonin against lipopolysaccharide (LPS)-induced myocardial injury as well as the mechanisms involved. Methods: Mice were intraperitoneally injected with LPS to induce a septic myocardial injury model or an LPS shock model, depending on the dose of LPS. Melatonin was given (20 mg/kg/day, via intraperitoneal injection) for a week prior to LPS insult. 6 h after LPS injection, echocardiographic analysis, TUNEL staining, transmission electron microscopy (TEM), western blot, quantitative real-time PCR and ELISA were used to investigate the protective effects of melatonin against LPS induced myocardial injury. AMPK inhibitor, autophagy activator and inhibitor, siRNAs were used for further validation. Results: Survival test showed that melatonin significantly increased the survival rate after LPS-induced shock. In the sepsis model, melatonin markedly ameliorated myocardial dysfunction, decreased the release of inflammatory cytokines, activated AMP-activated protein kinase (AMPK), improved mitochondrial function, and activated autophagy. To confirm whether the protection of melatonin was mediated by AMPK and autophagy, Compound C, an AMPK inhibitor; 3-MA, an autophagy inhibitor; and Rapamycin (Rapa), an autophagy activator, were used in this study. AMPK inhibition down-regulated autophagy, abolished protection of melatonin, as indicated by significantly decreased cardiac function, increased inflammation and damaged mitochondrial function. Furthermore, autophagy inhibition by 3-MA significantly impaired the protective effects of melatonin, whereas autophagy activation by Rapa reversed LPS + Compound C induced myocardial injury. In addition, in vitro studies further confirmed the protection of melatonin against LPS-induced myocardial injury and the mechanisms involving AMPK-mediated autophagy signaling. Conclusions: In summary, our results demonstrated that melatonin protects against LPS-induced septic myocardial injury by activating AMPK mediated autophagy pathway.

Melatonin: an anti-tumor agent for osteosarcoma

Osteosarcoma is the most common bone tumors which consisted of malignant mesenchymal cells generating osteoid and immature bone. It has been showed that osteosarcoma is common in children and adolescents and shows high mortality rate. A variety of therapeutic approaches (i.e., resection surgery, combined with chemotherapy and radiotherapy) have been used as conventional treatments in patients with osteosarcoma. Despite several attempts to improve therapeutic response, the rate of survival for osteosarcoma has not changed during the past 3 decades. Therefore, the discovery and developing new effective therapeutic platforms are required. Along to the established anti-cancer agents, some physiological regulators such melatonin, have been emerged as new anti-cancer agents. Melatonin is an indolamine hormone which is secreted from the pineal glands during the night and acts as physiological regulator. Given that melatonin shows a wide spectrum anti-tumor impacts. Besides different biologic activities of melatonin (e.g., immunomodulation and antioxidant properties), melatonin has a crucial role in the formation of bones, and its deficiency could be directly related to bone cancers. Several in vitro and in vivo experiments evaluated the effects of melatonin on osteosarcoma and other types of bone cancer. Taken together, the results of these studies indicated that melatonin could be introduced as new therapeutic candidate or as adjuvant in combination with other anti-tumor agents in the treatment of osteosarcoma. Herein, we summarized the anti-tumor effects of melatonin for osteosarcoma cancer as well as its mechanism of action.

Histone deacetylase 9 downregulation decreases tumor growth and promotes apoptosis in non-small cell lung cancer after melatonin treatment

Histone deacetylase 9 functions as an oncogene in a variety of cancers, but its role on non-small cell lung cancer (NSCLC) has not been reported. Melatonin was proven to possess anticancer actions, whereas its effect on NSCLC and underlying mechanisms remains poorly understood. In this study, 337 patients with complete clinicopathologic characteristics who underwent NSCLC surgery were recruited for the study. We found that NSCLC patients with high HDAC9 expression were correlated with worse overall survival and poor prognosis. HDAC9 knockdown significantly reduced NSCLC cell growth and induced apoptosis both in vivo and in vitro. Melatonin application also markedly inhibited cell proliferation, metastasis, and invasion and promoted apoptosis in NSCLC cells. Moreover, RNA-seq, real-time quantitative polymerase chain reaction, and western blot analyses showed that melatonin treatment decreased the HDAC9 level in NSCLC cells. A mechanistic study revealed that HDAC9 knockdown further enhanced the anticancer activities of melatonin treatment, whereas HDAC9 overexpression partially reversed the melatonin's anticancer effects. Additionally, the in vivo study found melatonin exerted anti-proliferative and pro-apoptotic effects on xenograft tumors which were also strengthened by HDAC9 knockdown. These results indicated that HDAC9 downregulation mediated the anti-NSCLC actions of melatonin, and targeting HDAC9 may be the novel therapeutic strategy for NSCLC.

Prognostic Impact of Melatonin Receptors MT1 and MT2 in Non-Small Cell Lung Cancer (NSCLC)

Background: Several studies have investigated the inhibitory effect of melatonin on lung cancer cells. There are no data available on the prognostic impact of melatonin receptors MT1 and MT2 in non-small cell lung cancer (NSCLC). Materials and Methods: Immunohistochemical studies of MT1 and MT2 were conducted on NSCLC (N = 786) and non-malignant lung tissue (NMLT) (N = 120) using tissue microarrays. Molecular studies were performed on frozen fragments of NSCLC (N = 62; real time PCR), NMLT (N = 24) and lung cancer cell lines NCI-H1703, A549 and IMR-90 (real time PCR, western blot). Results: The expression of both receptors was higher in NSCLC than in NMLT. Higher MT1 and MT2 expression levels (at protein and mRNA) were noted in squamous cell carcinomas (SCC) compared to adenocarcinomas (AC). MT1 immunoexpression decreased as both the tumour size and the cancer stage increased in the whole cohort, while MT2 decreased as the cancer stage increased, with lymph node involvement (in the whole study group) and increasing malignancy grade (in SCC). Higher expression of MT2 was associated with a favorable prognosis. MT2 was an independent prognostic factor for overall survival (OS) in all analyzed NSCLC and in smoking patients. Conclusions: Our observations may point to the potential prognostic significance of MT2 in NSCLC.

Immunoregulatory role of melatonin in cancer

Melatonin is a ubiquitous indole amine that plays a fundamental role in the regulation of the biological rhythm. Disrupted circadian rhythm alters the expression of clock genes and deregulates oncogenes, which finally promote tumor development and progression. An evidence supporting this notion is the higher risk of developing malignancies among night shift workers. Circadian secretion of the pineal hormone also synchronizes the immune system via a reciprocal association that exists between the immune system and melatonin. Immune cells are capable of melatonin biosynthesis in addition to the expression of its receptors. Melatonin induces big changes in different immune cell proportions, enhances their viability and improves immune cell metabolism in the tumor microenvironment. These effects might be directly mediated by melatonin receptors or indirectly through alterations in hormonal and cytokine release. Moreover, melatonin induces apoptosis in tumor cells via the intrinsic and extrinsic pathways of apoptosis, while it protectsthe immune cells. In general, melatonin has a profound impact on immune cell trafficking, cytokine production and apoptosis induction in malignant cells. On such a basis, using melatonin and resynchronization of sleep cycle may have potential implications in immune function enhancement against malignancies, which will be the focus of the present paper.

The potential therapeutic actions of melatonin in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and lethal disease worldwide. Melatonin, an indoleamine produced in pineal gland, shows anticancer effects on a variety of cancers, especially CRC. After clarifying the pathophysiology of CRC, the association of circadian rhythm with CRC, and the relationship between shift work and the incidence of CRC is reviewed. Next, we review the role of melatonin receptors in CRC and the relationship between inflammation and CRC. Also included is a discussion of the mechanism of gene regulation, control of cell proliferation, apoptosis, autophagy, antiangiogenesis and immunomodulation in CRC by melatonin. A review of the drug synergy of melatonin with other anticancer drugs suggests its usefulness in combination therapy. In summary, the information compiled may serve as comprehensive reference for the various mechanisms of action of melatonin against CRC, and as a guide for the design of future experimental research and for advancing melatonin as a therapeutic agent for CRC.

Melatonin and non-small cell lung cancer: new insights into signaling pathways

Non-small-cell lung cancer (NSCLC) is a type of malignancy with progressive metastasis having poor prognosis and lowered survival resulting from late diagnosis. The therapeutic approaches for the treatment of this incurable cancer are chemo- and radiotherapy. Since current treatments are insufficient and because of drug-induced undesirable side effects and toxicities, alternate treatments are necessary and critical. The role of melatonin, produced in and released from the pineal gland, has been documented as a potential therapy for NSCLC. Melatonin prevents tumor metastasis via inducing apoptosis processes and restraining the autonomous cell proliferation. Moreover, melatonin inhibits the progression of tumors due to its oncostatic, pro-oxidant and anti-inflammatory effects. As a result, the combined treatment with melatonin and chemotherapy may have a synergistic effect, as with some other tumors, leading to a prolonged survival and improved quality of life in patients with NSCLC. This review summarizes the available data, based on the molecular mechanisms and related signaling pathways, to show how melatonin and its supplementation function in NSCLC.

Melatonin Increases Bone Mass around the Prostheses of OVX Rats by Ameliorating Mitochondrial Oxidative Stress via the SIRT3/SOD2 Signaling Pathway

Bone mass loss around prostheses is a major cause of implant failure, especially in postmenopausal osteoporosis patients. In osteoporosis, excess oxidative stress largely contributed abnormal bone remodeling. Melatonin, which is synthesized from the pineal gland, promotes osteoblast differentiation and bone formation and has effectively been used to combat oxidative stress. Thus, we determined if melatonin can inhibit oxidative stress to promote osteogenesis and improve bone mass around prostheses in osteoporosis. In this study, we observed that received melatonin at 50 mg/kg body weight significantly increased periprosthetic bone mass as well as implant fixation intensity in ovariectomized (OVX) rats. Meanwhile, it decreased the expression of oxidative stress markers (NAPDH oxidase 2 and cytochrome c) and enhanced expressing level of the formation markers of bones (alkaline phosphatase, osteocalcin, and osterix) around prostheses compared to that in the control group. Additionally, melatonin decreased hydrogen peroxide- (H₂O₂-) induced oxidative stress and restored the osteogenesis potential of MC3T3-E1 cells. Mechanistically, melatonin clearly increased mitochondrial sirtuin 3 (SIRT3) expression and decreased the ratio of acetylated superoxide dismutase 2 (AC-SOD2)/SOD2 compared to the H₂O₂ group. SIRT3 inhibition counteracted the protective effects of melatonin on oxidative stress and bone formation. Together, the results showed that melatonin ameliorated oxidative stress in mitochondrial via the SIRT3/SOD2 signaling pathway, thereby promoting osteogenesis, improving bone mass around the prostheses, and increasing initial stability. Thus, melatonin might be a suitable candidate to decrease the rate of implant failure and lengthen the lifespan of prostheses after total joint arthroplasty.

Melatonin is a potential inhibitor of ovarian cancer: molecular aspects

Ovarian cancer is one of the most common causes of morbidity related to gynecologic malignancies. Possible risk factors are including hereditary ovarian cancer, obesity, diabetes mellitus, alcohol consumption, aging, and smoking. Various molecular signaling pathways including inflammation, oxidative stress, apoptosis and angiogenesis are involved in this progression of ovarian cancer. Standard treatments for recently diagnosed patients are Surgery and chemotherapy such as co-treatment with other drugs such that the exploitation of neoadjuvant chemotherapy is expanding. Melatonin (N-acetyl-5-methoxy-tryptamine), an endogenous agent secreted from the pineal gland, has anti-carcinogenic features, such as regulation of estradiol production, cell cycle modulation, stimulation of apoptosis as well as anti-angiogenetic properties, anti-inflammatory activities, significant antioxidant effects and modulation of various immune system cells and cytokines. Multiple studies have shown the significant beneficial roles of melatonin in various types of cancers including ovarian cancer. This paper aims to shed light on the roles of melatonin in ovarian cancer treatment from the standpoint of the molecular aspects.

Melatonin: Another avenue for treating osteoporosis?

Melatonin is a signal molecule that modulates the biological circadian rhythms of vertebrates. Melatonin deficiency is thought to be associated with several disorders, including insomnia, cancer, and cardiovascular and neurodegenerative diseases. Accumulating evidence has also indicated that melatonin may be involved in the homeostasis of bone metabolism. Age-related reductions in melatonin are considered to be critical factors in bone loss and osteoporosis with aging. Thus, serum melatonin levels might serve as a biomarker for the early detection and prevention of osteoporosis. Compared to conventional antiosteoporosis medicines, which primarily inhibit bone loss, melatonin both suppresses bone loss and promotes new bone formation. Mechanistically, by activating melatonin receptor 2 (MT2), melatonin upregulates the gene expression of alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP2), BMP6, osteocalcin, and osteoprotegerin to promote osteogenesis while inhibiting the receptor activator of NF-kB ligand (RANKL) pathway to suppress osteolysis. In view of the distinct actions of melatonin on bone metabolism, we hypothesize that melatonin may be a novel remedy for the prevention and clinical treatment of osteoporosis.

Melatonin Enhances Cisplatin and Radiation Cytotoxicity in Head and Neck Squamous Cell Carcinoma by Stimulating Mitochondrial ROS Generation, Apoptosis, and Autophagy

Head and neck cancer is the sixth leading cancer by incidence worldwide. Unfortunately, drug resistance and relapse are the principal limitations of clinical oncology for many patients, and the failure of conventional treatments is an extremely demoralizing experience. It is therefore crucial to find new therapeutic targets and drugs to enhance the cytotoxic effects of conventional treatments without potentiating or offsetting the adverse effects. Melatonin has oncostatic effects, although the mechanisms involved and doses required remain unclear. The purpose of this study is to determine the precise underlying mitochondrial mechanisms of melatonin, which increase the cytotoxicity of oncological treatments, and also to propose new melatonin treatments in order to alleviate and reverse radio- and chemoresistant processes. We analyzed the effects of melatonin on head and neck squamous cell carcinoma (HNSCC) cell lines (Cal-27 and SCC-9), which were treated with 0.1, 0.5, 1, and 1.5 mM melatonin combined with 8 Gy irradiation or 10 μM cisplatin. Clonogenic and MTT assays, as well as autophagy and apoptosis, involving flow cytometry and western blot, were performed in order to determine the cytotoxic effects of the treatments. Mitochondrial function was evaluated by measuring mitochondrial respiration, mtDNA content (RT-PCR), and mitochondrial mass (NAO). ROS production, antioxidant enzyme activity, and GSH/GSSG levels were analyzed using a fluorometric method. We show that high concentrations of melatonin potentiate the cytotoxic effects of radiotherapy and CDDP in HNSCC, which are associated with increased mitochondrial function in these cells. In HNSCC, melatonin induces intracellular ROS, whose accumulation plays an upstream role in mitochondria-mediated apoptosis and autophagy. Our findings indicate that melatonin, at high concentrations, combined with cisplatin and radiotherapy to improve its effectiveness, is a potential adjuvant agent.

[Emerging Actions of Pterostilebene on Cancer Research]

紫檀芪（3, 5-二甲氧基-4’-羟基二苯乙烯）是一种主要存在于蓝莓、葡萄和花榈木中的多酚类化合物。已有的研究发现紫檀芪具有抗肺癌、乳腺癌、胃癌、结肠癌等多种肿瘤的抗癌作用。其作用机制涉及调控影响多种肿瘤生物学特性。此外，紫檀芪具有比白藜芦醇更高的生物利用度和生物活性，其抗肿瘤作用和机制值得深入探讨和研究。

Melatonin restricts the viability and angiogenesis of vascular endothelial cells by suppressing HIF-1α/ROS/VEGF

Angiogenesis is an essential process involved in various physiological, including placentation, and pathological, including cancer and endometriosis, processes. Melatonin (MLT), a well-known natural hormone secreted primarily in the pineal gland, is involved in regulating neoangiogenesis and inhibiting the development of a variety of cancer types, including lung and breast cancer. However, the specific mechanism of its anti-angiogenesis activity has not been systematically elucidated. In the present study, the effect of MLT on viability and angiogenesis of human umbilical vein endothelial cells (HUVECs), and the production of vascular endothelial growth factor (VEGF) and reactive oxygen species (ROS), under normoxia or hypoxia was analyzed using Cell Counting kit 8, tube formation, flow cytometry, ELISA and western blot assays. It was determined that the secretion of VEGF by HUVECs was significantly increased under hypoxia, while MLT selectively obstructed VEGF release as well as the production of ROS under hypoxia. Furthermore, MLT inhibited the viability of HUVECs in a dose-dependent manner and reversed the increase in cell viability and tube formation that was induced by hypoxia/VEGF/H₂O₂. Additionally, treatment with an inhibitor of hypoxia inducible factor (HIF)-1α (KC7F2) and MLT synergistically reduced the release of ROS and VEGF, and inhibited cell viability and tube formation of HUVECs. These observations demonstrate that MLT may serve dual roles in the inhibition of angiogenesis, as an antioxidant and a free radical scavenging agent. MLT suppresses the viability and angiogenesis of HUVECs through the downregulation of HIF-1α/ROS/VEGF. In summary, the present data indicate that MLT may be a potential anticancer agent in solid tumors with abundant blood vessels, particularly combined with KC7F2.

AMPK/PGC1α activation by melatonin attenuates acute doxorubicin cardiotoxicity via alleviating mitochondrial oxidative damage and apoptosis

Doxorubicin (DOX) is a highly effective anticancer anthracycline drug, but its side effects at the level of the heart has limited its widespread clinical application. Melatonin is a documented potent antioxidant, nontoxic and cardioprotective agent, and it is involved in maintaining mitochondrial homeostasis and function. The present study established acute DOX-induced cardiotoxicity models in both H9c2 cells incubated with 1 μM DOX and C57BL/6 mice treated with DOX (20 mg/kg cumulative dose). Melatonin markedly alleviated the DOX-induced acute cardiac dysfunction and myocardial injury. Both in vivo and in vitro studies verified that melatonin inhibited DOX-induced mitochondrial dysfunction and morphological disorders, apoptosis, and oxidative stress via the activation of AMPK and upregulation of PGC1α with its downstream signaling (NRF1, TFAM and UCP2). These effects were reversed by the use of AMPK siRNA or PGC1α siRNA in H9c2 cells, and were also negated by the cotreatment with AMPK inhibitor Compound C in vivo. Moreover, PGC1α knockdown was without effect on the AMPK phosphorylation induced by melatonin in the DOX treated H9c2 cells. Therefore, AMPK/PGC1α pathway activation may represent a new mechanism for melatonin exerted protection against acute DOX cardiotoxicity through preservation of mitochondrial homeostasis and alleviation of oxidative stress and apoptosis.

Promising Antineoplastic Actions of Melatonin

Melatonin is an endogenous indoleamine with an incredible variety of properties and activities. In recent years, an increasing number of studies have investigated this indoleamine’s interaction with cancerous cells. In particular, it seems that melatonin not only has the ability to improve the efficacy of many drugs used in chemotherapy but also has a direct inhibitory action on neoplastic cells. Many publications underlined the ability of melatonin to suppress the proliferation of various cancer cells or to modulate the expression of membrane receptors on these cells, thereby reducing tumor aggressiveness to metastasize. In addition, while melatonin has antiapoptotic actions in normal cells, in many cancer cells it has proapoptotic effects; these dichotomous actions have gained the interest of researchers. The increasing focus on melatonin in the field of oncology and the growing number of studies on this topic require a deep understanding of what we already know about the antineoplastic actions of melatonin. This information would be of value for potential use of melatonin against neoplastic diseases.

Roles of DNA repair enzyme OGG1 in innate immunity and its significance for lung cancer

Cytokines are pivotal mediators of the immune response, and their coordinated expression protects host tissue from excessive damage and oxidant stress. Nevertheless, the development of lung pathology, including asthma, chronic obstructive pulmonary disease, and ozone-induced lung injury, is associated with oxidant stress; as evidence, there is a significant increase in levels of the modified guanine base 7,8-dihydro-8-oxoguanine (8-oxoG) in the genome. 8-OxoG is primarily recognized by 8-oxoguanine glycosylase 1 (OGG1), which catalyzes the first step in the DNA base excision repair pathway. However, oxidant stress in the cell transiently halts enzymatic activity of substrate-bound OGG1. The stalled OGG1 facilitates DNA binding of transactivators, including NF-κB, to their cognate sites to enable expression of cytokines and chemokines, with ensuing recruitments of inflammatory cells. Hence, defective OGG1 will modulate the coordination between innate and adaptive immunity through excessive oxidant stress and cytokine dysregulation. Both oxidant stress and cytokine dysregulation constitute key elements of oncogenesis by KRAS, which is mechanistically coupled to OGG1. Thus, analysis of the mechanism by which OGG1 modulates gene expression helps discern between beneficial and detrimental effects of oxidant stress, exposes a missing functional link as a marker, and yields a novel target for lung cancer.

Melatonin and pancreatic cancer: Current knowledge and future perspectives

Pancreatic cancer has a high mortality rate due to the absence of early symptoms and subsequent late diagnosis; additionally, pancreatic cancer has a high resistance to radio- and chemotherapy. Multiple inflammatory pathways are involved in the pathophysiology of pancreatic cancer. Melatonin an indoleamine produced in the pineal gland mediated and receptor-independent action is the pancreas and other where has both receptors. Melatonin is a potent antioxidant and tissue protector against inflammation and oxidative stress. In vivo and in vitro studies have shown that melatonin supplementation is an appropriate therapeutic approach for pancreatic cancer. Melatonin may be an effective apoptosis inducer in cancer cells through regulation of a large number of molecular pathways including oxidative stress, heat shock proteins, and vascular endothelial growth factor. Limited clinical studies, however, have evaluated the role of melatonin in pancreatic cancer. This review summarizes what is known regarding the effects of melatonin on pancreatic cancer and the mechanisms involved.

Melatonin Inhibits the Progression of Hepatocellular Carcinoma through MicroRNA Let7i-3p Mediated RAF1 Reduction

Melatonin is the main pineal hormone that relays light/dark-cycle information to the circadian system. Recent studies have examined the intrinsic antitumor activity of melatonin in various cancers, including hepatocellular carcinoma (HCC), the primary life-threatening malignancy in both sexes in Taiwan. However, the detailed regulatory mechanisms underlying melatonin’s anti-HCC activity remain incompletely understood. Here, we investigated the mechanisms by which the anti-HCC activity of melatonin is regulated. Human hepatoma cell lines were treated with 1 and 2 mM melatonin, and functional assays were used to dissect melatonin’s antitumor effect in HCC; small-RNA sequencing was performed to identify the microRNAs (miRNAs) involved in the anti-HCC activity of melatonin; and quantitative RT-PCR and Western blotting were used to elucidate how miRNAs regulate melatonin-mediated HCC suppression. Melatonin treatment at both doses strongly inhibited the proliferation, migration and invasion capacities of Huh7 and HepG2 cell lines, and melatonin treatment markedly induced the expression of the miRNA let7i-3p in cells. Notably, transfection of cells with a let7i-3p mimic drastically reduced RAF1 expression and activation of mitogen-activated protein kinase signaling downstream from RAF1, and rescue-assay results demonstrated that melatonin inhibited HCC progression by modulating let7i-3p-mediated RAF1 suppression. Our findings support the view that melatonin treatment holds considerable promise as a therapy for HCC.