A phase II study of tamoxifen plus melatonin in metastatic solid tumour patients

Melatonin effect on breast and ovarian cancers by targeting the PI3K/Akt/mTOR pathway

Melatonin, the hormone of the pineal gland, possesses a range of physiological functions, and recently, its anticancer effect has become more apparent. A more thorough understanding of molecular alterations in the components of several signaling pathways as new targets for cancer therapy is needed because of current innate restrictions such as drug toxicity, side effects, and acquired or de novo resistance. The PI3K/Akt/mTOR pathway is overactivated in many solid tumors, such as breast and ovarian cancers. This pathway in normal cells is essential for growth, proliferation, and survival. However, it is an undesirable characteristic in malignant cells. We have reviewed multiple studies about the effect of melatonin on breast and ovarian cancer, focusing on the PI3K/Akt/mTOR pathway. Melatonin exerts its inhibitory effects via several mechanisms. A: Downregulation of downstream or upstream components of the signaling pathway such as phosphatase and tensin homolog (PTEN), phosphatidylinositol (3,4,5)-trisphosphate kinase (PI3K), p-PI3K, Akt, p-Akt, mammalian target of rapamycin (mTOR), and mTOR complex1 (mTORC1). B: Apoptosis induction by decreasing MDM2 expression, a downstream target of Akt, and mTOR, which leads to Bad activation in addition to Bcl-XL and p53 inhibition. C: Induction of autophagy in cancer cells via activating ULK1 after mTOR inhibition, resulting in Beclin-1 phosphorylation. Beclin-1 with AMBRA1 and VPS34 promotes PI3K complex I activity and autophagy in cancer cells. The PI3K/Akt/mTOR pathway overlaps with other intracellular signaling pathways and components such as AMP-activated protein kinase (AMPK), Wnt/β-catenin, mitogen-activated protein kinase (MAPK), and other similar pathways. Cancer therapy can benefit from understanding how these pathways interact and how melatonin affects these pathways.

Role of melatonin in carcinogenesis and metastasis: From mechanistic insights to intermeshed networks of noncoding RNAs

In recent years, seminal studies have been devoted to unraveling the puzzling mysteries associated with the cancer preventive/inhibitory role of melatonin. Our current knowledge of the translational mechanisms and the detailed structural insights have highlighted the characteristically exclusive role of melatonin in the inhibition of carcinogenesis and metastatic dissemination. This mini-review outlines recent discoveries related to mechanistic role of melatonin in prevention of carcinogenesis and metastasis. Moreover, another exciting facet of this mini-review is related to phenomenal breakthroughs linked with regulation of noncoding RNAs by melatonin in wide variety of cancers.

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.

Bioenergetic alteration in gastrointestinal cancers: The good, the bad and the ugly

Cancer cells exhibit metabolic reprogramming and bioenergetic alteration, utilizing glucose fermentation for energy production, known as the Warburg effect. However, there are a lack of comprehensive reviews summarizing the metabolic reprogramming, bioenergetic alteration, and their oncogenetic links in gastrointestinal (GI) cancers. Furthermore, the efficacy and treatment potential of emerging anticancer drugs targeting these alterations in GI cancers require further evaluation. This review highlights the interplay between aerobic glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (OXPHOS) in cancer cells, as well as hypotheses on the molecular mechanisms that trigger this alteration. The role of hypoxia-inducible transcription factors, tumor suppressors, and the oncogenetic link between hypoxia-related enzymes, bioenergetic changes, and GI cancer are also discussed. This review emphasizes the potential of targeting bioenergetic regulators for anti-cancer therapy, particularly for GI cancers. Emphasizing the potential of targeting bioenergetic regulators for GI cancer therapy, the review categorizes these regulators into aerobic glycolysis/ lactate biosynthesis/transportation and TCA cycle/coupled OXPHOS. We also detail various anti-cancer drugs and strategies that have produced pre-clinical and/or clinical evidence in treating GI cancers, as well as the challenges posed by these drugs. Here we highlight that understanding dysregulated cancer cell bioenergetics is critical for effective treatments, although the diverse metabolic patterns present challenges for targeted therapies. Further research is needed to comprehend the specific mechanisms of inhibiting bioenergetic enzymes, address side effects, and leverage high-throughput multi-omics and spatial omics to gain insights into cancer cell heterogeneity for targeted bioenergetic therapies.

Synthesis of Red-Light-Responsive Pheophorbide-a Tryptamine Conjugated Photosensitizers for Photodynamic Therapy

Six methyl pheophorbide-a derivatives were prepared by linking a tryptamine side chain at the C-13¹ , C-15² and C-17³ positions of pheophorbide-a. Prepared conjugates were characterized and evaluated for their photocytotoxicity against A549 cells. The conjugate 6 a with strong absorption at 413 nm (Soret band), 663-671 nm (Q bands) and comparable fluorescence quantum yield (0.26) was found to exhibit significant cytotoxicity (659 nM). Molecular integration of pheophorbide-a and tryptamines showed synergistic effects as the most potent conjugate 6 a was identified with enhanced photocytotoxicity when compared to methyl pheophorbide-a. The conjugate 6 a was smoothly taken up by A549 cells and exhibited intracellular localization predominantly to lysosome in the cytoplasm. Upon photoirradiation 6 a generated singlet oxygen to show potent cytotoxicity toward A549 cells.

Coping with Oxidative Stress in Reproductive Pathophysiology and Assisted Reproduction: Melatonin as an Emerging Therapeutical Tool

Infertility is an increasing global public health concern with socio-psychological implications for affected couples. Remarkable advances in reproductive medicine have led to successful treatments such as assisted reproductive techniques (ART). However, the search for new therapeutic tools to improve ART success rates has become a research hotspot. In the last few years, pineal indolamine melatonin has been investigated for its powerful antioxidant properties and its role in reproductive physiology. It is considered a promising therapeutical agent to counteract the detrimental effects associated with oxidative stress in fertility treatments. The aim of the present narrative review was to summarize the current state of the art on the importance of melatonin in reproductive physiology and to provide a critical evaluation of the data available encompassing basic, translational and clinical studies on its potential use in ART to improve fertility success rates.

Oncostatic activities of melatonin: Roles in cell cycle, apoptosis, and autophagy

Melatonin, the major secretory product of the pineal gland, not only regulates circadian rhythms, mood, and sleep but also has actions in neoplastic processes which are being intensively investigated. Melatonin is a promising molecule which considered a differentiating agent in some cancer cells at both physiological and pharmacological concentrations. It can also reduce invasive and metastatic status through receptors MT1 and MT2 cytosolic binding sites, including calmodulin and quinone reductase II enzyme, and nuclear receptors related to orphan members of the superfamily RZR/ROR. Melatonin exerts oncostatic functions in numerous human malignancies. An increasing number of studies report that melatonin reduces the invasiveness of several human cancers such as prostate cancer, breast cancer, liver cancer, oral cancer, lung cancer, ovarian cancer, etc. Moreover, melatonin's oncostatic activities are exerted through different biological processes including antiproliferative actions, stimulation of anti-cancer immunity, modulation of the cell cycle, apoptosis, autophagy, the modulation of oncogene expression, and via antiangiogenic effects. This review focuses on the oncostatic activities of melatonin that targeted cell cycle control, with special attention to its modulatory effects on the key regulators of the cell cycle, apoptosis, and telomerase activity.

Melatonin inhibits lipid accumulation to repress prostate cancer progression by mediating the epigenetic modification of CES1

BACKGROUND

Androgen deprivation therapy (ADT) is the main clinical treatment for patients with advanced prostate cancer (PCa). However, PCa eventually progresses to castration-resistant prostate cancer (CRPC), largely because of androgen receptor variation and increased intratumoral androgen synthesis. Several studies have reported that one abnormal lipid accumulation is significantly related to the development of PCa. Melatonin (MLT) is a functionally pleiotropic indoleamine molecule and a key regulator of energy metabolism. The aim of our study is finding the links between CRPC and MLT and providing the basis for MLT treatment for CRPC.

METHODS

We used animal CRPC models with a circadian rhythm disorder, and PCa cell lines to assess the role of melatonin in PCa.

RESULTS

We demonstrated that MLT treatment inhibited tumor growth and reversed enzalutamide resistance in animal CRPC models with a circadian rhythm disorder. A systematic review and meta-analysis demonstrated that MLT is positively associated with an increased risk of developing advanced PCa. Restoration of carboxylesterase 1 (CES1) expression by MLT treatment significantly reduced lipid droplet (LD) accumulation, thereby inducing apoptosis by increasing endoplasmic reticulum stress, reducing de novo intratumoral androgen synthesis, repressing CRPC progression and reversing the resistance to new endocrine therapy. Mechanistic investigations demonstrated that MLT regulates the epigenetic modification of CES1. Ces1-knockout (Ces-/- ) mice verified the important role of endogenous Ces1 in PCa.

CONCLUSIONS

Our findings provide novel preclinical and clinical information about the role of melatonin in advanced PCa and characterize the importance of enzalutamide combined with MLT administration as a therapy for advanced PCa.

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 suppresses chronic restraint stress-mediated metastasis of epithelial ovarian cancer via NE/AKT/β-catenin/SLUG axis

Chronic stress has been shown to facilitate progression of epithelial ovarian cancer (EOC), however, the neuro-endocranial mechanism participating in this process still remains unclear. Here, we reported that chronic restraint stress (CRS) promoted the abdominal implantation metastasis of EOC cells and the expression of epithelial–mesenchymal transition-related markers in tumor-bearing mouse model, including TWIST, SLUG, SNAIL, and β-catenin. We observed that β-catenin co-expressed with SLUG and norepinephrine (NE) in tumor tissues obtained from nude mice. Further ex vivo experiments revealed that NE promoted migration and invasion of ovarian cancer cells and SLUG expression through upregulating expression and improving transcriptional function of β-catenin in vitro. A human phosphor-kinase array suggested that NE activated various kinases in ovarian cancer cells, and we further confirmed that AKT inhibitor reduced NE-mediated pro-metastatic impacts and activation of the β-catenin/SLUG axis. Furthermore, the expression levels of NE and β-catenin were examined in ovarian tumor tissues by using tumor tissue arrays. Results showed that the expression levels of both NE and β-catenin were associated with poor clinical stage of serous EOC. Moreover, we found that melatonin (MLT) effectively reduced the abdominal tumor burden of ovarian cancer induced by CRS, which was partially related to the inhibition of the NE/AKT/β-catenin/SLUG axis. Collectively, these findings suggest a novel mechanism for CRS-mediated ovarian cancer metastasis and MLT has a potential therapeutic efficacy against ovarian cancer.

Transcriptomic analysis on the effects of melatonin in gastrointestinal carcinomas

BACKGROUND

Melatonin has been shown with anticancer property and therapeutic potential for tumors. However, there lacks a systematic study on the molecular pathways of melatonin and its antitumor effects in gastrointestinal carcinomas.

METHODS

Using the gene expression profiles of four cancer cell lines from three types of gastrointestinal carcinomas before and after melatonin treatment, including gastric carcinoma (GC), colorectal carcinoma (CRC) and hepatocellular carcinoma (HCC), differentially expressed genes (DEGs) and biological pathways influenced by melatonin were identified. The qRT-PCR analyses were performed to validate the effects of melatonin on 5-FU resistance-related genes in CRC.

RESULTS

There were 17 pathways commonly altered by melatonin in the three cancer types, including FoxO signaling pathways enriched by the upregulated DEGs and cell cycle signaling pathways enriched by the downregulated DEGs, confirmed the dual role of melatonin to tumor growth, pro-apoptosis and anti-proliferation. DEGs upregulated in the three types of cancer tissues but reversely downregulated by melatonin were commonly enriched in RNA transport, spliceosome and cell cycle signaling pathways, which indicate that melatonin might exert antitumor effects through these pathways. Our results further showed that melatonin can downregulate the expression levels of 5-FU resistance-related genes, such as thymidylate synthase in GC and ATR, CHEK1, BAX and MYC in CRC. The qRT-PCR results demonstrated that melatonin enhanced the sensitivity of CRC 5-FU resistant cells by decreasing the expression of ATR.

CONCLUSIONS

Melatonin exerts the effects of pro-apoptosis and anti-proliferation on gastrointestinal carcinomas, and might increase the sensitivity of 5-FU in GC and CRC patients.

Melatonin: An atypical hormone with major functions in the regulation of angiogenesis

Melatonin (N-acetyl-5-methoxytryptamine), a pleotropic molecule with a wide distribution, has received considerable attention in recent years, mostly because of its various major effects on tissues or cells since it has both receptor-dependent and receptor-independent actions over a wide range of concentrations. These biological and physiological functions of melatonin include regulation of circadian rhythms by modulating the expression of core oscillator genes, scavenging the reactive oxygen species and reactive nitrogen species, modulating the immune system and inflammatory response, and exerting cytoprotective and antiapoptotic effects. Given the multiple critical roles of melatonin, dysregulation of its production or any disruption in signaling through its receptors may have contributed in the development of a wide range of disorders including type 2 diabetes, aging, immune-mediated diseases, hypertension, and cancer. Herein, we focus on the modulatory effects of melatonin on angiogenesis and its implications as a therapeutic strategy in cancer and related diseases.

Pharmacological, Mechanistic, and Pharmacokinetic Assessment of Novel Melatonin-Tamoxifen Drug Conjugates as Breast Cancer Drugs

Tamoxifen is used to prevent and treat estrogen receptor-positive (ER+) breast cancer (BC); however, its chronic use can increase uterine cancer risk and induce tamoxifen resistance. Novel melatonin-tamoxifen drug conjugates may be promising to treat BC and may help offset the adverse effects of tamoxifen usage alone due to the presence of melatonin. We synthesized and screened five drug conjugates (C2, C4, C5, C9, and C15 linked) for their effects on BC cell (MCF-7, tamoxifen-resistant MCF-7, mouse mammary carcinoma, MDA-MB-231, and BT-549) viability, migration, and binding affinity to melatonin receptor 1 (MT1R) and estrogen receptor 1 (ESR1). C4 and C5 demonstrated the most favorable pharmacological characteristics with respect to binding profiles (affinity for ESR1 and MT1R) and their potency/efficacy to inhibit BC cell viability and migration in four phenotypically diverse invasive ductal BC cell lines. C4 and C5 were further assessed for their actions against tamoxifen-resistant MCF-7 cells and a patient-derived xenograft triple-negative BC cell line (TU-BcX-4IC) and for their mechanisms of action using selective mitogen-activated protein kinase kinase MEK1/2, MEK5, and phosphoinositide 3-kinase (PI3K) inhibitors. C4 and C5 inhibited tamoxifen-resistant MCF-7 cells with equal potency (IC₅₀ = 4-8 μM) and efficacy (∼90% inhibition of viability and migration) but demonstrated increased potency (IC₅₀ = 80-211 μM) and efficacy (∼140% inhibition) to inhibit migration versus cell viability (IC₅₀ = 181-304 mM; efficacy ∼80% inhibition) in TU-BcX-4IC cells. Unique pharmacokinetic profiles were observed, with C4 having greater bioavailability than C5. Further assessment of C4 and C5 demonstrates that they create novel pharmacophores within each BC cell that is context specific and involves MEK1/2/pERK1/2, MEK5/pERK5, PI3K, and nuclear factor κB. These melatonin-tamoxifen drug conjugates show promise as novel anticancer drugs and further preclinical and clinical evaluation is warranted.

Modulation of burst firing of neurons in nucleus reticularis of the thalamus by GluN2C-containing NMDA receptors

The GluN2C subunit of the NMDA receptor is enriched in the neurons in nucleus reticularis of the thalamus (nRT), but its role in regulating their function is not well understood. We found that deletion of GluN2C subunit did not affect spike frequency in response to depolarizing current injection or hyperpolarization-induced rebound burst firing of nRT neurons. D-cycloserine or CIQ (GluN2C/GluN2D positive allosteric modulator) did not affect the depolarization-induced spike frequency in nRT neurons. A newly identified highly potent and efficacious co-agonist of GluN1/GluN2C NMDA receptors, AICP, was found to reduce the spike frequency and burst firing of nRT neurons in wildtype but not GluN2C knockout. This effect was potentially due to facilitation of GluN2C-containing receptors because inhibition of NMDA receptors by AP5 did not affect spike frequency in nRT neurons. We evaluated the effect of intracerebroventricular injection of AICP. AICP did not affect basal locomotion or prepulse inhibition but facilitated MK-801-induced hyperlocomotion. This effect was observed in wildtype but not in GluN2C knockout mice demonstrating that AICP produces GluN2C-selective effects in vivo Using a chemogenetic approach we examined the role of nRT in this behavioral effect. Gq or Gi coupled DREADDs were selectively expressed in nRT neurons using cre-dependent viral vectors and PV-Cre mouse line. We found that similar to AICP effect, activation of Gq but not Gi coupled DREADD facilitated MK-801-induced hyperlocomotion. Together, these results identify a unique role of GluN2C-containing receptors in the regulation of nRT neurons and suggest GluN2C-selective in vivo targeting of NMDA receptors by AICP. SIGNIFICANCE STATEMENT: The nucleus reticularis of the thalamus composed of GABAergic neurons is termed as guardian of the gateway and is an important regulator of corticothalamic communication which may be impaired in autism, non-convulsive seizures and other conditions. We found that strong facilitation of tonic activity of GluN2C subtype of NMDA receptors using AICP, a newly identified glycine-site agonist of NMDA receptors, modulates the function of reticular thalamus neurons. AICP was also able to produce GluN2C-dependent behavioral effects in vivo. Together, these finding identify a novel mechanism and a pharmacological tool to modulate activity of reticular thalamic neurons in disease states.

Melatonin inhibits breast cancer cell invasion through modulating DJ-1/KLF17/ID-1 signaling pathway

Breast cancer is the most common neoplastic disorder diagnosed in women. The main goal of this study was to explore the effect of melatonin against breast cancer metastasis and compared this with the actions of taxol (a well-known chemotherapeutic drug), and the impact of their combination against breast cancer metastasis. Melatonin showed no cytotoxic effect while taxol showed antiproliferative and cytotoxic effects on MCF-7 and MDA-MB-231 cells. Furthermore, melatonin inhibited the generation of reactive oxygen species. Melatonin and taxol clearly decreased cell migration and invasion at low doses, especially those matching the normal physiological concentration at night. Melatonin and taxol markedly reduced DJ-1 and ID-1 and increased KLF17 messenger RNA and protein expression levels. The present results also showed that melatonin and taxol induced GSK3-β nuclear and Snail cytosolic localization. These changes were accompanied by a concurrent rise in E-cadherin expression. The above data show that normal levels of melatonin may help in preventing breast cancer metastasis through inhibiting DJ-1/KLF17/ID-1 signaling pathway. The combination of melatonin and taxol is a potent candidate against breast cancer metastasis, better than using melatonin or taxol as a single drug.

Tamoxifen Never Ceases to Amaze: New Findings on Non-Estrogen Receptor Molecular Targets and Mediated Effects

Tamoxifen is a first targeted drug that continues to be the gold standard in treatment of estrogen receptor positive breast cancer for almost 50 years. The current review is an update of the paper published in 2012. We provide the new data on the tamoxifen targets that are the key points of signaling cascades activating cellular proliferation, which determines aggressiveness of disease and chemotherapy resistance or sensitivity. Some inspiring clinical cases dealing with tamoxifen efficiency in treatment of different tumors are discussed. Additionally, the review includes data on antiviral, antibacterial, antifungal and antiparasitic activity of tamoxifen.

Antioxidants as precision weapons in war against cancer chemotherapy induced toxicity - Exploring the armoury of obscurity

Cancer is the leading cause of mortality worldwide, accounting for almost 13% of deaths in the world. Among the conventional cancer treatments, chemotherapy is most frequently carried out to treat malignant cancer rather than localised lesions which is amenable to surgery and radiotherapy. However, anticancer drugs are associated with a plethora of side effects. Each drug, within every class, has its own set of adverse reactions which may cause patient incompliance and deterioration of the quality of life. One of the major causes of adverse reactions, especially for drugs targeting DNA, is the excessive production of reactive oxygen species (ROS) and subsequent build up of oxidative stress. To curb these undesired side effects, several dietary supplements have been tested, amongst which antioxidants have gained increasing popularity as adjuvant in chemotherapy. However, many oncologists discourage the use of antioxidant rich food supplements because these may interfere with the modalities which kill cancer by generating free radicals. In the present review, all studies reporting concomitant use of several antioxidants with chemotherapy are indiscriminately included and discussed impartially.

The effect of supplementation of thirteen different antioxidants and their analogues as a single agent or in combination with chemotherapy has been compiled in this article. The present review encompasses a total of 174 peer-reviewed original articles from 1967 till date comprising 93 clinical trials with a cumulative number of 18,208 patients, 56 animal studies and 35 in vitro studies. Our comprehensive data suggests that antioxidant has superior potential of ameliorating chemotherapeutic induced toxicity. Antioxidant supplementation during chemotherapy also promises higher therapeutic efficiency and increased survival times in patients.

Melatonin and Fertoprotective Adjuvants: Prevention against Premature Ovarian Failure during Chemotherapy

Premature ovarian failure is one of the side effects of chemotherapy in pre-menopausal cancer patients. Preservation of fertility has become increasingly important in improving the quality of life of completely recovered cancer patients. Among the possible strategies for preserving fertility such as ovarian tissue cryopreservation, co-treatment with a pharmacological adjuvant is highly effective and poses less of a burden on the human body. Melatonin is generally produced in various tissues and acts as a universally acting antioxidant in cells. Melatonin is now more widely used in various biological processes including treating insomnia and an adjuvant during chemotherapy. In this review, we summarize the information indicating that melatonin may be useful for reducing and preventing premature ovarian failure in chemotherapy-treated female patients. We also mention that many adjuvants other than melatonin are developed and used to inhibit chemotherapy-induced infertility. This information will give us novel insights on the clinical use of melatonin and other agents as fertoprotective adjuvants for female cancer patients.

Melatonin and IL-25 modulate apoptosis and angiogenesis mediators in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumour cells

BACKGROUND

Melatonin has oncostatic actions and IL-25 is active in inflammatory processes that induce apoptosis in tumor cells AIM: The aim of this study was to evaluate melatonin and IL-25 in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumor cells cultured as monolayers and tridimensional structures.

MATERIALS AND METHODS

The cells were treated with melatonin, IL-25 and IL-17B silencing gene and performed cell viability, gene and protein expression of caspase-3 and VEGFA (Vascular endothelial growth factor A) and an apoptosis membrane protein array.

RESULTS

Treatment with 1 mM of melatonin reduced cell viability of both tumor cell lines, all treatments alone and combined significantly increased caspase-3 cleaved and proteins involved in the apoptotic pathway and reduced pro-angiogenic VEGFA, confirming the effectiveness of these potential promising treatments.

CONCLUSION

This is the first study evaluating the potential use of these strategies in CF-41 and CMT-U229 cell lines and together encourages subsequent in vitro and in vivo studies for further exploration of clinical applications.

The therapeutic application of melatonin in supportive care and palliative medicine

Melatonin is a hormone produced mainly in the pineal gland. Plasma levels exhibit a circadian variation with the highest concentration occurring at night. The human biologic effects of melatonin depend upon the time of day it is made available. One of these effects is the setting and resetting of circadian clocks (chronobiotic effect). Additionally, it may be a potent antioxidant and immunomodulator and has been shown to have anti-tumor, anticytokine, anti-insomnia, and anticachexia effects. Melatonin has also been shown to improve survival and performance status in patients with advanced cancer. Objective tumor response occurs with melatonin alone or when combined with interleukin-2 (IL-2). Further, melatonin reduces radiation- and chemotherapeutic-induced toxicity. Symptomatic and circadian disruption is linked to increased cancer risk. The chronobiotic capacity of melatonin to reset circadian clocks may provide a verifiable strategy to reduce cancer risk and enhance quality of life by diminishing cancer-induced circadian disruption.

Melatonin induces apoptosis in cholangiocarcinoma cell lines by activating the reactive oxygen species-mediated mitochondrial pathway

We previously demonstrated that melatonin could be used as a chemopreventive agent for inhibiting cholangiocarcinoma (CCA) development in a hamster model. However, the cytotoxic activity of melatonin in cancer remains unclear. In the present study, we investigated the effect of melatonin on CCA cell lines. Human CCA cell lines (KKU-M055 and KKU-M214) were treated with melatonin at concentrations of 0.5, 1 and 2 mM for 48 h. Melatonin treatment exerted a cytotoxic effect on CCA cells by inhibiting CCA cell viability in a concentration-dependent manner. Treatment with melatonin, especially at 2 mM, increased intracellular reactive oxygen species (ROS) production and in turn led to increased oxidative DNA damage and 8-oxodG formation. Moreover, melatonin treatment enhanced the production of cytochrome c leading to apoptosis in a concentration-dependent manner, as indicated by increased expression of apoptosis-related proteins caspase-3 and caspase-7. In conclusion, melatonin acts as a pro-oxidant by activating ROS-dependent DNA damage and thus leading to the apoptosis of CCA cells.

Therapeutic actions of melatonin on gastrointestinal cancer development and progression

Melatonin exerts a multitude of physiological functions including the regulation of the sleep cycle and circadian rhythm. Although the synthesis of melatonin in the pineal gland is regulated by changes in the light/dark cycle, the release of melatonin in the gastrointestinal tract is related to food consumption. Melatonin regulates antioxidative processes and it improves T-helper cell response by stimulating the production of specific cytokines. Melatonin is directly involved in preventing tumor initiation, promotion, and progression in a variety of cancers of the gastrointestinal tract including colorectal cancer, cholangiocarcinoma, hepatocarcinoma, and pancreatic carcinoma. This paper is a review of the literature regarding melatonin in the gastrointestinal tract and as a potential therapy for gastrointestinal cancers.

Pharmacologic concentrations of melatonin have diverse influence on differential expressions of angiogenic chemokine genes in different hepatocellular carcinoma cell lines

This study was to investigate whether melatonin (MLT) at pharmacologic concentrations (1 and 100 μM) had potential to influence the expressions of angiogenic (CCL2, CXCL6, IL8) and angiostatic (CXCL10) chemokine genes in two hepatocellular carcinoma (HCC) cell lines with different characteristics (cell line A, HCC24/KMUH, without susceptible to amphotericin B (AmB)-induced oxidative stress; cell line B, HCC38/KMUH, susceptible to AmB-induced oxidative stress). Differential expression of gene was investigated by quantitative reverse transcriptase-polymerase chain reaction. Two genes related to oxidative stress (SOD2, VNN3) were also studied. One and 100 μM MLT up-regulated CCL2, IL8 and CXCL10 genes in cell line A but down-regulated CCL2, CXCL6, IL8 and SOD2 genes in cell line B. CXCL10 gene was up-regulated by 1 and 100 μM MLT in both cell lines. SOD2 gene was down-regulated by 1 and 100 μM MLT only in cell line B. The magnitudes of gene expression fold changes of CCL2 and IL8 genes in cell line A and CCL2, CXCL6, IL8 and SOD2 genes in cell line B were similar between 1 and 100 μM MLT. The magnitudes of gene expression fold change of up-regulated CXCL10 gene in both cell lines were smaller in 100 μM MLT than in 1 μM MLT. In conclusion, the responses of angiogenic chemokine genes to MLT were mainly determined by the characteristics of cancer cells. The concentration of MLT may be the main determinant for the response of angiostatic CXCL10 gene to MLT. Clinical application of MLT in patients with HCC should consider these effects.

Cellular mechanisms involved in the melatonin inhibition of HT-29 human colon cancer cell proliferation in culture

The antiproliferative and proapoptotic properties of melatonin in human colon cancer cells in culture were recently reported. To address the mechanisms involved in these actions, HT-29 human colon cancer cells were cultured in RPMI 1640 medium supplemented with fetal bovine serum at 37 degrees C. Cell proliferation was assessed by the incorporation of [(3)H]-thymidine into DNA. Cyclic nucleotide levels, nitrite concentration, glutathione peroxidase and reductase activities, and glutathione levels were assessed after the incubation of these cells with the following drugs: melatonin membrane receptor agonists 2-iodo-melatonin, 2-iodo-N-butanoyl-5-methoxytryptamine, 5-methoxycarbonylamino-N-acetyltryptamine (GR-135,531), and the antagonists luzindole, 4-phenyl-2-propionamidotetralin, and prazosin; the melatonin nuclear receptor agonist CGP 52608, and four synthetic kynurenines analogs to melatonin 2-acetamide-4-(3-methoxyphenyl)-4-oxobutyric acid, 2-acetamide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid, 2-butyramide-4-(3-methoxyphenyl)-4-oxobutyric acid and 2-butyramide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid. The results show that the membrane receptors are not necessary for the antiproliferative effect of melatonin and the participation of the nuclear receptor in this effect is suggested. Moreover, the antioxidative and anti-inflammatory actions of melatonin, counteracting the oxidative status and reducing the production of nitric oxide by cultured HT-29 cells seem to be directly involved in the oncostatic properties of melatonin. Some of the synthetic kynurenines exert higher antiproliferative effects than melatonin. The results reinforce the clinical interest of melatonin due to the different mechanisms involved in its oncostatic role, and suggest a new synthetic pathway to obtain melatonin agonists with clinical applications to oncology.

Therapeutic treatments potentially mediated by melatonin receptors: potential clinical uses in the prevention of osteoporosis, cancer and as an adjuvant therapy

Melatonin's therapeutic potential is grossly underestimated because its functional roles are diverse and its mechanism(s) of action are complex and varied. Melatonin produces cellular effects via a variety of mechanisms in a receptor independent and dependent manner. In addition, melatonin is a chronobiotic agent secreted from the pineal gland during the hours of darkness. This diurnal release of melatonin impacts the sensitivity of melatonin receptors throughout a 24-hr period. This changing sensitivity probably contributes to the narrow therapeutic window for use of melatonin in treating sleep disorders, that is, at the light-to-dark (dusk) or dark-to-light (dawn) transition states. In addition to the cyclic changes in melatonin receptors, many genes cycle over the 24-hr period, independent or dependent upon the light/dark cycle. Interestingly, many of these genes support a role for melatonin in modulating metabolic and cardiovascular physiology as well as bone metabolism and immune function and detoxification of chemical agents and cancer reduction. Melatonin also enhances the actions of a variety of drugs or hormones; however, the role of melatonin receptors in modulating these processes is not known. The goal of this review is to summarize the evidence related to the utility of melatonin as a therapeutic agent by focusing on its other potential uses besides sleep disorders. In particular, its use in cancer prevention, osteoporosis and, as an adjuvant to other therapies are discussed. Also, the role that melatonin and, particularly, its receptors play in these processes are highlighted.

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

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

Melatonin increases the survival time of animals with untreated mammary tumours: Neuroendocrine stabilization

The aim of this study was to evaluate the therapeutic effect of melatonin, the main hormone of the pineal gland, on rats with advanced and untreated mammary tumours. Mammary tumours were chemically induced in Sprague-Dawley rats with the carcinogen 9,10-dimethyl-1,2-bezanthracene (DMBA). After the appearance of tumours the effect of melatonin (5 mg/ml per rat per day) was then evaluated on the survival time, tumour multiplicity, and tumour volume until the death of the animals. In addition, the variations in prolactin, noradrenaline and adrenaline concentrations, and in the percentage of NK cells were evaluated after one month of the treatment with melatonin. Daily administration of melatonin increased significantly the survival time of tumour-bearing animals (p<0.05 with respect to the control non-melatonin-receiving rats). The increased survival time did not correlate, however, with changes in either tumour multiplicity or tumour growth rate. Animals with mammary tumours exhibited an increase (p<0.05 with respect to healthy animals) in prolactin and catecholamine concentrations. The administration of melatonin stabilized the hormone levels, returning them to those in the basal-healthy animals. Rats with mammary tumours also presented lower percentages of NK cells, which were not increased by the administration of melatonin. The results strongly suggest that melatonin per se is beneficial during advanced breast cancer. It increases survival time, maybe by improving the homeostatic and neuroendocrine equilibrium which is imbalanced during advanced breast cancer.

Multifactorial activities of nonsteroidal antiestrogens against leukemia

The antileukemic activity of nonsteroidal antiestrogens was investigated. Tamoxifen, clomiphene and nafoxidine caused a decrease in viability of the estrogen receptor-negative T-lymphoblastic leukemia cell line CCRF/CEM, nafoxidine being the most active. A combination of clomiphene and genistein resulted in a synergistic cytotoxic effect when applied to Molt-3, another T-lymphblastic leukemic cell line. The antiestrogens arrested the cells at G(0)/G(1) phase and induced apoptosis. Using the CCRF/VCR(1000) cell line, which is resistant to vincristine, it was observed that the effect of nafoxidine on modulating drug resistance was manifested at a lower concentration than that causing a direct cytotoxic effect. Nafoxidine inhibited the Pgp pump activity as measured by rhodamine 123 efflux. Combination with verapamil was found to be more effective in abrogating the pump activity. This study points to the multifactorial activities of nonsteroidal antiestrogens against lymphoblastic leukemia and implies their potential use in clinical treatment as antileukemic drugs.

Potentiation of antiproliferative effects of tamoxifen and ethanol on mouse hepatoma cells by melatonin: possible involvement of mitogen-activated protein kinase and induction of apoptosis

Melatonin, the major secretory product of the pineal gland, is in focus of many research areas because of its ability to scavenge free oxygen radicals and thereby protect cells and tissues from radical damage. Some studies suggest melatonin may be a possible therapeutic agent with potential clinical applications against pathological states due to reactive oxygen species. Here, we investigated the effects of melatonin on the mouse hepatoma cell line HEPA 1-6, coincubated with ethanol, and tamoxifen, respectively. Cell proliferation rates were detected by the 3-[4,5 dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide (MTT) proliferation assay. A dose-dependent inhibition of the proliferative activity by melatonin was observed from 640 microM to 3 mM, which was significantly higher (P < 0.01) than with the solvent (ethanol) alone. Concentrations of 320 microM and less had no effect on cell proliferation. This antiproliferative effect might be because of the prolonged activation of mitogen-activated protein kinase which was activated by phosphorylation 15 min after the induction with melatonin. Furthermore, apoptosis was found to be enhanced by melatonin (75% more than with the solvent alone, P < 0.001). Finally, we show that the inhibitory effect of tamoxifen (25 microM) is markedly enhanced by the coincubation with melatonin (1.3 mM) up to 75% (P < 0.001). These data show that the antiproliferative effects of tamoxifen and ethanol, respectively, on mouse hepatoma cell line HEPA 1-6 are enhanced by melatonin. Although at the conditions described here the antiproliferative effects of melatonin occur at supraphysiological concentrations, these data may help to support clinical studies where melatonin is given simultaneously with tamoxifen or other standard chemotherapeutica.

Melatonin: from basic research to cancer treatment clinics

Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger, an indirect antioxidant, as well as an important immunomodulatory agent. In both in vitro and in vivo investigations, melatonin protected healthy cells from radiation-induced and chemotherapeutic drug-induced toxicity. Furthermore, several clinical studies have demonstrated the potential of melatonin, either alone or in combination with traditional therapy, to yield a favorable efficacy to toxicity ratio in the treatment of human cancers. This study reviews the literature from laboratory investigations that document the antioxidant and oncostatic actions of melatonin and summarizes the evidence regarding the potential use of melatonin in cancer treatment. This study also provides rationale for the design of larger translational research-based clinical trials.

Dehydroepiandrosterone and Melatonin: Two Neurohormones

Complementary or alternative medicines in the United States have received prominent attention during recent years. Though there seems to be little rigorous support for the long-term efficacy and safety of these treatments in humans,1-2 the popularity of these natural products persists. It has been estimated that, for 1997, 12 percent of the U.S. population (approximately 24 million people) had used herbal medicines within the previous 12 months, and that 5 billion dollars had been spent on these products during that same year.3 Two of the alternative medicines included are dehydroepiandrosterone (DHEA) and melatonin. DHEA is a hormone produced primarily by the adrenal glands, and is a precursor for endogenous steroid production (e.g., testosterone, estrogen). DHEA is also believed to exert central pharmacologic effects. Melatonin is a hormone produced by the pineal gland and is involved in circadium rhythm maintenance and sleep regulation. Because of extensive physiological effects, these two neuro-hormones are being advocated for the treatment of several medical disorders, as well as for routine ailments. The purpose of this article is to discuss salient, pharmacotherapeutic-related characteristics of each hormone, and to briefly review supporting evidence from studies using human subjects.

Melatonin receptor ligands: synthesis of new melatonin derivatives and comprehensive comparative molecular field analysis (CoMFA) study

The CoMFA methodology was applied to melatonin receptor ligands in order to establish quantitative structure-affinity relationships. One hundred thirty-three compounds were considered: they were either collected from literature or newly synthesized in order to gain information about the less explored positions. To this end, various melatonin derivatives were prepared and their affinity for quail optic tecta melatonin receptor was tested. Compounds were aligned on the putative active conformation of melatonin proposed by our previously reported pharmacophore search, and their relative affinities were calculated from the displacement of 2-[125I]-iodomelatonin on different tissues expressing aMT receptors. Compounds were grouped into three sets according to their topology. Subset A: melatonin-like compounds; subset B: N-acyl-2-amino-8-methoxytetralins and related compounds; subset C:N-acyl-phenylalkylamines and related compounds. CoMFA models were derived for each set, using the steric, electrostatic, and lipophilic fields as structural descriptors; the PLS analyses were characterized by good statistical parameters, taking into account the heterogeneity of the binding data, obtained with different experimental protocols. From the CoMFA model for the melatonin-like compounds, besides the well-known positive effect of 2-substitution, a low steric tolerance for substituents in 1, 6, and 7, and a negative effect of electron-rich 4-substituents were observed; the information provided by the newly synthesized compounds was essential for these results. Moreover, a comprehensive model for the 133 compounds, accounting for a common alignment and a common mode of interaction at the melatonin receptor, was derived (Q2 = 0.769, R2 = 0.905). This model validates our previously reported pharmacophore search and offers a clear depiction of the structure-affinity relationships for the melatonin receptor ligands.

2-[N-Acylamino(C1-C3)alkyl]indoles as MT1 melatonin receptor partial agonists, antagonists, and putative inverse agonists

The synthesis of several novel indole melatonin analogues substituted at the 2-position with acylaminomethyl (8-11), acylaminoethyl (5a-k), or acylaminopropyl (13) side chains is reported. On the basis of a novel in vitro functional assay (specific binding of [35S]GTPgammaS), which can discriminate agonist from partial agonist, antagonist, and inverse agonist ligands, 5a,g, h,j and 13 were shown to be partial agonists, 5d,e and 8-11 competitive antagonists, and 5b,c,k putative inverse agonists. Binding and functional assays were performed on cloned human MT1 receptor. Structure-activity relationship considerations indicate that N-[1-aryl-2-(4-methoxy-1H-indol-2-yl)(C1-C2)alkyl]alkanamides represent a lead structure for this type of ligands.