Melatonin is a potential inhibitor of ovarian cancer: molecular aspects

Melatonin: Current evidence on protective and therapeutic roles in gynecological diseases

Melatonin, a potent antioxidant and free radical scavenger, has been demonstrated to be effective in gynecological conditions and female reproductive cancers. This review consolidates the accumulating evidence on melatonin's multifaceted protective effects in different pathological contexts. In gynecological conditions such as endometriosis, polycystic ovary syndrome (PCOS), and uterine leiomyoma, melatonin has shown promising effects in reducing oxidative stress, inflammation, and hormonal imbalances. It inhibits adhesion molecules' production, and potentially mitigates leukocyte adherence and inflammatory responses. Melatonin's regulatory effects on hormone production and insulin sensitivity in PCOS individuals make it a promising candidate for improving oocyte quality and menstrual irregularities. Moreover, melatonin exhibits significant antitumor effects by modulating various signaling pathways, promoting apoptosis, and suppressing metastasis in breast cancers and gynecological cancers, including ovarian, endometrial, and cervical cancers. Furthermore, melatonin's protective effects are suggested to be mediated by interactions with its receptors, estrogen receptors and other nuclear receptors. The regulation of clock-related genes and circadian clock systems may also contribute to its inhibitory effects on cancer cell growth. However, more comprehensive research is warranted to fully elucidate the underlying molecular mechanisms and establish melatonin as a potential therapeutic agent for these conditions.

Unveiling the Protective Role of Melatonin in Osteosarcoma: Current Knowledge and Limitations

Melatonin, an endogenous neurohormone produced by the pineal gland, has received increased interest due to its potential anti-cancer properties. Apart from its well-known role in the sleep-wake cycle, extensive scientific evidence has shown its role in various physiological and pathological processes, such as inflammation. Additionally, melatonin has demonstrated promising potential as an anti-cancer agent as its function includes inhibition of tumorigenesis, induction of apoptosis, and regulation of anti-tumor immune response. Although a precise pathophysiological mechanism is yet to be established, several pathways related to the regulation of cell cycle progression, DNA repair mechanisms, and antioxidant activity have been implicated in the anti-neoplastic potential of melatonin. In the current manuscript, we focus on the potential anti-cancer properties of melatonin and its use in treating and managing pediatric osteosarcoma. This aggressive bone tumor primarily affects children and adolescents and is treated mainly by surgical and radio-oncological interventions, which has improved survival rates among affected individuals. Significant disadvantages to these interventions include disease recurrence, therapy-related toxicity, and severe/debilitating side effects that the patients have to endure, significantly affecting their quality of life. Melatonin has therapeutic effects when used for treating osteosarcoma, attributed to its ability to halt cancer cell proliferation and trigger apoptotic cell death, thereby enhancing chemotherapeutic efficacy. Furthermore, the antioxidative function of melatonin alleviates harmful side effects of chemotherapy-induced oxidative damage, aiding in decreasing therapeutic toxicities. The review concisely explains the many mechanisms by which melatonin targets osteosarcoma, as evidenced by significant results from several in vitro and animal models. Nevertheless, if further explored, human trials remain a challenge that could shed light and support its utility as an adjunctive therapeutic modality for treating osteosarcoma.

The role of tryptophan derivatives as anti-kinetoplastid agents

Kinetoplastids are the causative agents for a spectrum of vector-borne diseases including Leishmaniasis, Chagas disease and Trypanosomiasis that affect millions of people worldwide. In the absence of safe and effective vaccines, chemotherapy, in conjunction with vector control, remain the most significant control approach for kinetoplastid diseases. However, commercially available treatment for these neglected tropical diseases frequently ends up with toxic side effects and increasing resistance. To meet the rising need for innovative medications, alternative chemotherapeutic agents are required. Moreover, insights into target-based mode of action of chemotherapeutic agents are required if novel drugs that may outwit resistance to commercially available drugs are to be developed. Tryptophan has been implicated in a variety of diseases and disorders due to its fundamental role as a precursor to several bioactive metabolites, as well as its importance in the improvement of health and nutrition, diagnostics, and therapeutics. The regulation of tryptophan metabolism plays a fundamental role in the growth of kinetoplastids. Moreover, the levels of tryptophan may serve as a biomarker to distinguish between the stages of kinetoplastids making it an important amino acid to explore for drug targets. The main aim of this review is thus to provide a comprehensive literature synthesis of tryptophan derivatives to explore as potential anti-kinetoplastids. Here we highlight the role of tryptophan derivatives as chemotherapeutic agents against kinetoplastids. The reviewed compounds provide insights into potential new drug interventions that may combat the increasing problem of anti-kinetoplastid resistance.

Therapeutic effects of melatonin on endometriosis, targeting molecular pathways: Current knowledge and future perspective

Endometriosis, the very serious disease in women creates a huge financial burden worldwide, which is comparable to diabetes mellitus. In addition to the typical pelvic pain, endometriosis is related to low life quality and decreased work efficiency; clinical consequences include mood complaints, metabolic impairments, inflammation, immunologic problems, and elevated malignancy risks. Several risk factors are correlated with endometriosis including elevated oxidative and nitrosative stress, long-lasting inflammation, raised immune tolerance, as well as autoimmunity. Melatonin is a natural molecule present throughout both the plant and animal kingdoms. It has numerous functions as an antioxidant and anti-inflammatory agent. Due to the anti-proliferative, antioxidant, anti-inflammatory, and anti-invasive features of melatonin, it performances as a beneficial agent to limit endometriosis; this involves several pathways including antiestrogenic, antioxidant, anti-inflammatory, and anti-apoptosis effects, as well as reducing the growth of E2-induced endometriotic tissue. Moreover, melatonin can favor sleep quality and decrease the unwanted signs in the patients. However, most of the data on melatonin accured from experimental works and additional clinical trials are needed. This review summarizes what is currently known regarding the influence of melatonin on endometriosis. AVAILABILITY OF DATA AND MATERIAL: Not applicable.

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 Melatonin in Pregnancy and the Health Benefits for the Newborn

In the last few years, there have been significant evolutions in the understanding of the hormone melatonin in terms of its physiology, regulatory role, and potential utility in various domains of clinical medicine. Melatonin's properties include, among others, the regulation of mitochondrial function, anti-inflammatory, anti-oxidative and neuro-protective effects, sleep promotion and immune enhancement. As it is also bioavailable and has little or no toxicity, it has been proposed as safe and effective for the treatment of numerous diseases and to preserve human health. In this manuscript, we tried to evaluate the role of melatonin at the beginning of human life, in pregnancy, in the fetus and in newborns through newly published literature studies.

Review of Under-Recognized Adjunctive Therapies for Cancer

Patients and providers may not be aware that several adjunctive measures can significantly improve the quality of life, response to treatment, and possibly outcomes for cancer patients. This manuscript presents a review of practical under-recognized adjunctive therapies that are effective including exercise; stress-reduction techniques such as mindfulness, massage, yoga, Tai Chi, breathing exercises; importance of sleep quality; diet modifications such as calorie restriction at the time of chemotherapy and avoidance of high carbohydrate foods; supplements such as aspirin, green tea, turmeric, and melatonin; and repurposed prescription medications such as metformin and statins. Each recommendation should be tailored to the individual patient to assure no contraindications.

Melatonin Reverses the Warburg-Type Metabolism and Reduces Mitochondrial Membrane Potential of Ovarian Cancer Cells Independent of MT1 Receptor Activation

Ovarian cancer (OC) is the most lethal gynecologic malignancy, and melatonin has shown various antitumor properties. Herein, we investigated the influence of melatonin therapy on energy metabolism and mitochondrial integrity in SKOV-3 cells and tested whether its effects depended on MT1 receptor activation. SKOV-3 cells were exposed to different melatonin concentrations, and experimental groups were divided as to the presence of MT1 receptors (melatonin groups) or receptor absence by RNAi silencing (siRNA MT1+melatonin). Intracellular melatonin levels increased after treatment with melatonin independent of the MT1. The mitochondrial membrane potential of SKOV-3 cells decreased in the group treated with the highest melatonin concentration. Melatonin reduced cellular glucose consumption, while MT1 knockdown increased its consumption. Interconversion of lactate to pyruvate increased after treatment with melatonin and was remarkable in siRNA MT1 groups. Moreover, lactate dehydrogenase activity decreased with melatonin and increased after MT1 silencing at all concentrations. The UCSC XenaBrowser tool showed a positive correlation between the human ASMTL gene and the ATP synthase genes, succinate dehydrogenase gene (SDHD), and pyruvate dehydrogenase genes (PDHA and PDHB). We conclude that melatonin changes the glycolytic phenotype and mitochondrial integrity of SKOV-3 cells independent of the MT1 receptor, thus decreasing the survival advantage of OC cells.

Molecular and cellular mechanisms of melatonin in breast cancer

Breast cancer is considered as one of the most important health problems due to its poor prognosis and high rate of mortality and new diagnosed cases. Annually, a great number of deaths are reported in men and women; this means that despite all the improvements in cancer diagnosis and treatment, still, an intense need for more effective approaches exists. Melatonin is a multivalent compound which has a hand in several cellular and molecular processes and therefore, is an appropriate candidate for treatment of many diseases like cancer. Currently, considerable properties of this agent have oriented the research towards investigating its effects specifically in breast cancer. In this review, we gathered a bunch of evidence in order to give a new sight for breast cancer treatment utilizing melatonin. We expect that in coming years, melatonin will become one of the most common therapeutic drugs with lesser side-effects than other chemotherapeutic drugs.

[Melatonin inhibits growth and metastasis of MDA-MB-231 breast cancer cells by activating autophagy]

OBJECTIVE

To investigate the effects of melatonin on the growth and metastasis of MDA-MB-231 breast cancer cells and explore the mechanism.

METHODS

MDA-MB-231 cells were treated with 1, 3 or 5 mmol/L melatonin, and the changes in cell proliferation were examined using CCK-8 assay. Colony-forming assay and wound healing assay were used to assess the effects of melatonin treatmnent on colony-forming ability and migration of the cells. Flow cytometry and immunofluoresnce assay were employed to examine apoptosis and positive staining for autophagy-related proteins in the cells treated with 3 mmol/L melatonin. The effects of melatonin treatment alone or in combination with 3-methyladenine (3-MA) on the expressions of the proteins associated with autophagy (LC3, P62 and Beclin1), apoptosis (Bcl2 and Bax) and epithelial-mesenchymal transition (E-cadherin and Snail) were examined with Western blotting.

RESULTS

Melatonin treatment significantly inhibited the proliferation of breast cancer cells in a concentration- and time-dependent manner (P < 0.05), suppressed colony-forming ability and migration (P < 0.01), and promoted apoptosis of the cells (P < 0.01). Melatonin treatment alone significantly increased the expressions of Bax (P < 0.05), E-cadherin, LC3-II/LC3-I, and Beclin1 and lowered the expressions of Bcl2 (P < 0.05), Snail, P62 (P < 0.05), and Bcl2/Bax ratio (P < 0.01) in the cells, and caused enhanced positive staining of Beclin1 protein and attenuated staining of P62 protein. Compared with melatonin treatment alone, melatonin treatment combined with 3-MA significantly decreased the expressions of Beclin1 (P < 0.001), LC3-II/LC3-I (P < 0.05), Bax (P < 0.01), and E-cadherin (P < 0.001) and increased the expressions of Bcl2 (P < 0.05), Snail, and Bcl2/Bax ratio (P < 0.01).

CONCLUSION

Melatonin can induce autophagy of MDA-MB-231 breast cancer cells to inhibit cell proliferation and metastasis and promote cell apoptosis, and suppressing autophagy can weaken the inhibitory effect of melatonin on the growth and metastasis of breast cancer cells.

The proteomic landscape of ovarian cancer cells in response to melatonin

Ovarian cancer (OC) is the most lethal gynecological malignancy with a highly negative prognosis. Melatonin is an indoleamine secreted by the pineal gland during darkness and has shown antitumor activity in both in vitro and in vivo experiments. Herein, we investigated the influence of melatonin on the proteome of human ovarian carcinoma cells (SKOV-3 cell line) using the Ultimate 3000 LC Liquid NanoChromatography equipment coupled to a Q-Exactive mass spectrometry. After 48 h of treatment, melatonin induced a significant cytotoxicity especially with the highest melatonin concentration. The proteomic profile revealed 639 proteins in the control group, and 98, 110, and 128 proteins were altered by melatonin at the doses of 0.8, 1.6, and 2.4 mM, respectively. Proteins associated with the immune system and tricarboxylic acid cycle were increased in the three melatonin-exposed groups of cells. Specifically, the dose of 2.4 mM led to a reduction in molecules associated with protein synthesis, especially those of the ribosomal protein family. We also identified 28 potential genes shared between normal ovarian tissue and OC in all experimental groups, and melatonin was predicted to alter genes encoding ribosomal proteins. Notably, the set of proteins changed by melatonin was linked to a better prognosis for OC patients. We conclude that melatonin significantly alters the proteome of SKOV-3 cells by changing proteins involved with the immune response and mitochondrial metabolism. The concentration of 2.4 mM of melatonin promoted the largest number of protein changes. The evidence suggests that melatonin may be an effective therapeutic strategy against OC.

The Therapeutic Potential of Common Herbal and Nano-Based Herbal Formulations against Ovarian Cancer: New Insight into the Current Evidence

Ovarian cancer (OCa) is characterized as one of the common reasons for cancer-associated death in women globally. This gynecological disorder is chiefly named the "silent killer" due to lacking an association between disease manifestations in the early stages and OCa. Because of the disease recurrence and resistance to common therapies, discovering an effective therapeutic way against the disease is a challenge. According to documents, some popular herbal formulations, such as curcumin, quercetin, and resveratrol, can serve as an anti-cancer agent through different mechanisms. However, these herbal products may be accompanied by some pharmacological limitations, such as poor bioavailability, instability, and weak water solubility. On the contrary, using nano-based material, e.g., nanoparticles (NPs), micelles, liposomes, can significantly solve these limitations. Therefore, in the present study, we will summarize the anti-cancer aspects of these herbal and-nano-based herbal formulations with a focus on their mechanisms against OCa.

Acute melatonin administration improves exercise tolerance and the metabolic recovery after exhaustive effort

The present study investigated the effects of acute melatonin administration on the biomarkers of energy substrates, GLUT4, and FAT/CD36 of skeletal muscle and its performance in rats subjected to exhaustive swimming exercise at an intensity corresponding to the maximal aerobic capacity (tlim). The incremental test was performed to individually determine the exercise intensity prescription and 48 h after, the animals received melatonin (10 mg·kg^-1) or vehicles 30 min prior to tlim. Afterwards, the animals were euthanized 1 or 3 h after the exhaustion for blood and muscles storage. The experiment 1 found that melatonin increased the content of glycogen and GLUT4 in skeletal muscles of the animals that were euthanized 1 (p < 0.05; 22.33% and 41.87%) and 3 h (p < 0.05; 37.62% and 57.87%) after the last procedures. In experiment 2, melatonin enhanced the tlim (p = 0.01; 49.42%), the glycogen content (p < 0.05; 40.03%), GLUT4 and FAT/CD36 in exercised skeletal muscles (F = 26.83 and F = 25.28, p < 0.01). In summary, melatonin increased energy substrate availability prior to exercise, improved the exercise tolerance, and accelerated the recovery of muscle energy substrates after the tlim, possibly through GLUT4 and FAT/CD36.

Anticancer effects of melatonin via regulating lncRNA JPX-Wnt/β-catenin signalling pathway in human osteosarcoma cells

Osteosarcoma (OS) is a type of malignant primary bone cancer, which is highly aggressive and occurs more commonly in children and adolescents. Thus, novel potential drugs and therapeutic methods are urgently needed. In the present study, we aimed to elucidate the effects and mechanism of melatonin on OS cells to provide a potential treatment strategy for OS. The cell survival rate, cell viability, proliferation, migration, invasion and metastasis were examined by trypan blue assay, MTT, colony formation, wound healing, transwell invasion and attachment/detachment assay, respectively. The expression of relevant lncRNAs in OS cells was determined by real-time qPCR analysis. The functional roles of lncRNA JPX in OS cells were further examined by gain and loss of function assays. The protein expression was measured by western blot assay. Melatonin inhibited the cell viability, proliferation, migration, invasion and metastasis of OS cells (Saos-2, MG63 and U2OS) in a dose-dependent manner. Melatonin treatment significantly downregulated the expression of lncRNA JPX in Saos-2, MG63 and U2OS cells. Overexpression of lncRNA JPX into OS cell lines elevated the cell viability and proliferation, which was accompanied by the increased metastasis. We also found that melatonin inhibited the OS progression by suppressing the expression of lncRNA JPX via regulating the Wnt/β-catenin pathway. Our results suggested that melatonin inhibited the biological functions of OS cells by repressing the expression of lncRNA JPX through regulating the Wnt/β-catenin signalling pathway, which indicated that melatonin might be applied as a potentially useful and effective natural agent in the treatment of OS.

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 and Therapeutic Potential of Melatonin in Various Type of Cancers

Cancer is a large group of diseases and the second leading cause of death worldwide. Lung, prostate, colorectal, stomach, and liver cancers are the most common types of cancer in men, whereas breast, colorectal, lung, cervical, and thyroid cancers are the most common among women. Presently, various treatment strategies, including surgical resection combined with chemotherapy, radiotherapy, nanotherapy, and immunotherapy, have been used as conventional treatments for patients with cancer. However, the clinical outcomes of advanced-stage disease remain relatively unfavorable owing to the emergence of chemoresistance, toxicity, and other undesired detrimental side effects. Therefore, new therapies to overcome these limitations are indispensable. Recently, there has been considerable evidence from experimental and clinical studies suggesting that melatonin can be used to prevent and treat cancer. Studies have confirmed that melatonin mitigates the pathogenesis of cancer by directly affecting carcinogenesis and indirectly disrupting the circadian cycle. Melatonin (MLT) is nontoxic and exhibits a range of beneficial effects against cancer via apoptotic, antiangiogenic, antiproliferative, and metastasis-inhibitory pathways. The combination of melatonin with conventional drugs improves the drug sensitivity of cancers, including solid and liquid tumors. In this manuscript, we will comprehensively review some of the cellular, animal, and human studies from the literature that provide evidence that melatonin has oncostatic and anticancer properties. Further, this comprehensive review compiles the available experimental and clinical data analyzing the history, epidemiology, risk factors, therapeutic effect, clinical significance, of melatonin alone or in combination with chemotherapeutic agents or radiotherapy, as well as the underlying molecular mechanisms of its anticancer effect against lung, breast, prostate, colorectal, skin, liver, cervical, and ovarian cancers. Nonetheless, in the interest of readership clarity and ease of reading, we have discussed the overall mechanism of the anticancer activity of melatonin against different types of cancer. We have ended this report with general conclusions and future perspectives.

Melatonin provides protection against cisplatin-induced ovarian damage and loss of fertility in mice

RESEARCH QUESTION

Can melatonin provide non-invasive ovarian protection against damage caused by cis-diamminedichloroplatinum (cisplatin) and preserve fertility in female cancer patients? And if so, what is the possible mechanism?

DESIGN

Athymic BALB/c nude tumour-bearing female mice were used to demonstrate whether melatonin affects the antineoplastic effect when co-administrated with cisplatin. Sexually mature and newborn C57BL/6 female mice were used to evaluate the potential effects of melatonin on the ovarian follicle pool, pregnancy rate and litter number in cisplatin-treated mice. The ovaries underwent immunohistochemical, TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) and gene array analysis to explore the underlying mechanism. In addition, granulosa cells were isolated to investigate the potential protective mechanism of melatonin.

RESULTS

Melatonin not only enhanced the anti-cancer effect of cisplatin in tumour-bearing nude mice, but also reduced ovarian toxicity and preserved long-term fertility in cisplatin-treated C57BL/6 female mice. When co-administrated, melatonin was able to reduce the DNA damage and toxic effects on lipid peroxidation in the ovaries caused by cisplatin. Specifically, melatonin was able to largely restore lipid peroxidation in granulosa cells and thus prevent ovarian follicles from being depleted.

CONCLUSIONS

Melatonin has the potential to be used as a chemotherapeutic adjuvant to simultaneously improve the outcome of anti-cancer treatment and preserve ovarian function during cisplatin chemotherapy. Notably, its properties of DNA protection and antioxidant effects on follicles may benefit female cancer survivors and prevent premature ovarian failure as well as fertility loss caused by chemotherapy.

Central and peripheral actions of melatonin on reproduction in seasonal and continuous breeding mammals

Under field conditions, especially for mammals that inhabit high latitudes, the regulation of seasonal breeding activity to ensure delivery of the young at the time most conducive to their survival is essential. This is most frequently accomplished by the annual reproductive cycle being linked to seasonal photoperiod changes which determine the nocturnal duration of the pineal melatonin signal. Mating can occur during any season that ensures spring/early summer delivery of the offspring. Thus, the season of mating is determined by the duration of pregnancy. The precise hormonal control of the annual cycle of reproduction by melatonin is accomplished at the level of the hypothalamo-pituitary axis which, in turn, determines the physiological state of the gonad and adnexa due to the regulation of pituitary gonadotrophin release. Many species are continuous rather than seasonal breeders. In these species, melatonin has a minor hormonal influence on the central regulation of reproduction but, nevertheless, its antioxidant functions at the level of the gonads support optimal reproductive physiology. Possibly like all cells, those in the ovary, e.g., granulosa cells and oocytes (less is known about melatonin synthesis by the testes or spermatogenic cells), synthesize melatonin which is used locally to combat free radicals and reactive nitrogen species which would otherwise cause oxidative/nitrosative stress to these critically important cells. Oxidative damage to the oocyte, zygote, blastocyst, etc., results in an abnormal fetus which is either sloughed or gives rise to an unhealthy offspring. The importance of the protection of the gametes (both oocytes and sperm) from oxidative molecular mutilation cannot be overstated. Fortunately, as a highly effective free radical scavenger and indirect antioxidant (by upregulating antioxidant enzyme), locally-produced melatonin is in the optimal location to protect the reproductive system from such damage.

Two neuroendocrine G protein-coupled receptor molecules, somatostatin and melatonin: Physiology of signal transduction and therapeutic perspectives

Recent studies have shown that G protein-coupled receptors (GPCRs), the largest signal-conveying receptor family, are targets for mutations occurring frequently in different cancer types. GPCR alterations associated with cancer development represent significant challenges for the discovery and the advancement of targeted therapeutics. Among the different molecules that can activate GPCRs, we focused on two molecules that exert their biological actions regulating many typical features of tumorigenesis such as cellular proliferation, survival, and invasion: somatostatin and melatonin. The modulation of signaling pathways, that involves these two molecules, opens an interesting scenario for cancer therapy, with the opportunity to act at different molecular levels. Therefore, the aim of this review is the analysis of the biological activity and the therapeutic potential of somatostatin and melatonin, displaying a high affinity for GPCRs, that interfere with cancer development and maintenance.

The Association of Sleep Disorders, Obesity and Sleep-Related Hypoxia with Cancer

BACKGROUND

Sleep disorders have emerged as potential cancer risk factors.

OBJECTIVE

This review discusses the relationships between sleep, obesity, and breathing disorders with concomitant risks of developing cancer.

RESULTS

Sleep disorders result in abnormal expression of clock genes, decreased immunity, and melatonin release disruption. Therefore, these disorders may contribute to cancer development. Moreover, in sleep breathing disorder, which is frequently experienced by obese persons, the sufferer experiences intermittent hypoxia that may stimulate cancer cell proliferation.

DISCUSSION

During short- or long- duration sleep, sleep-wake rhythm disruption may occur. Insomnia and obstructive sleep apnea increase cancer risks. In short sleepers, an increased risk of stomach cancer, esophageal squamous cell cancer, and breast cancer was observed. Among long sleepers (>9 hours), the risk of some hematologic malignancies is elevated.

CONCLUSION

Several factors including insomnia, circadian disruption, obesity, and intermittent hypoxia in obstructive sleep apnea are contributing risk factors for increased risk of several types of cancers. However, further studies are needed to determine the more significant of these risk factors and their interactions.

Melatonin and gastrointestinal cancers: Current evidence based on underlying signaling pathways

Gastrointestinal (GI) cancers, leading causes of cancer-related deaths, have been serious challenging human diseases up to now. Because of high rates of mortality, late-stage diagnosis, metastasis to distant locations, and low effectiveness and adverse events of routine standard therapies, the quality of life and survival time are low in patients with GI cancers. Hence, many efforts need to be done to explore and find novel efficient treatments. Beneficial effects of melatonin have been reported in a wide variety of human diseases. Melatonin has antioxidant, anti-inflammatory, antimicrobial, and anticancer effects. Various studies have showed the regulatory effects of melatonin on apoptotsis, autophagy and angiogenesis; these properties result in the inhibition of invasion, migration, and proliferation of GI cancer cells in vivo and in vitro. Together, this review suggests that melatonin in combination with anticancer agents may improve the efficacy of routine medicine and survival rate of patients with cancer.

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.

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.

Potential of Melatonin as Adjuvant Therapy of Oral Cancer in the Era of Epigenomics

The wide variety of epigenetic controls available is rapidly expanding the knowledge of molecular biology even overflowing it. At the same time, it can illuminate unsuspected ways of understanding the etiology of cancer. New emerging therapeutic horizons, then, promise to overcome the current antitumor strategies need. The translational utility of this complexity is particularly welcome in oral cancer (OC), in which natural history is alarmingly disappointing due to the invasive and mutilating surgery, the high relapsing rate, the poor quality of life and the reduced survival after diagnosis. Melatonin activates protective receptor-dependent and receptor-independent processes that prevent tissue cancerisation and inhibit progressive tumor malignancy and metastasis. Related evidence has shown that melatonin pleiotropy encompasses gene expression regulation through all the three best-characterized epigenetic mechanisms: DNA methylation, chromatin modification, and non-coding RNA. OC has received less attention than other cancers despite prognosis is usually negative and there are no significant therapy improvements recorded in the past decade. However, a large research effort is being carried out to elucidate how melatonin´s machinery can prevent epigenetic insults that lead to cancer. In the light of recent findings, a comprehensive examination of biochemistry through which melatonin may reverse epigenetic aberrations in OC is an extraordinary opportunity to take a step forward in the clinical management of patients.

Melatonin attenuates expression of cyclooxygenase-2 (COX-2) in activated microglia induced by lipopolysaccharide (LPS)

Lipopolysaccharide (LPS) is a known neurotoxin and utilized most extensively as a microglial activator for induction of inflammatory neurodegeneration. Melatonin (MEL) is the main secretory product of pineal gland reported to be responsible for a variety of physiological functions. However, the molecular mechanisms underlying the influence of MEL on microglia activation remain unclear. The aim of this study was to investigate the effect of MEL on cyclooxygenase-2 (COX-2) levels in LPS-induced microglia. The results of RT-PCR and Western blot analysis showed that MEL significantly inhibited LPS-mediated upregulation of COX-2 in microglia. Data from ELISA demonstrated that prostaglandin E2 (PGE2), the downstream effector of COX-2, concentrations were also reduced. In addition, MEL was found to decrease activation of ERK1/2, JNK, p38 MAPK, and NF-κB, the upstream signal pathways of COX-2. Taken together, evidence indicates that MEL may attenuate upregulation of COX-2 by blocking the MAPK/NF-κB signaling pathway in LPS-stimulated microglia.