Melatonin regulates tumor aggressiveness under acidosis condition in breast cancer cell lines

Melatonin controls cell proliferation and modulates mitochondrial physiology in pancreatic stellate cells

We have investigated the effects of melatonin on major pathways related with cellular proliferation and energetic metabolism in pancreatic stellate cells. In the presence of melatonin (1 mM, 100 µM, 10 µM, or 1 µM), decreases in the phosphorylation of c-Jun N-terminal kinase and of p44/42 and an increase in the phosphorylation of p38 were observed. Cell viability dropped in the presence of melatonin. A rise in the phosphorylation of AMP-activated protein kinase was detected in the presence of 1 mM and 100 µM melatonin. Treatment with 1 mM melatonin decreased the phosphorylation of protein kinase B, whereas 100 µM and 10 µM melatonin increased its phosphorylation. An increase in the generation of mitochondrial reactive oxygen species and a decrease of mitochondrial membrane potential were noted following melatonin treatment. Basal and maximal respiration, ATP production by oxidative phosphorylation, spare capacity, and proton leak dropped in the presence of melatonin. The expression of complex I of the mitochondrial respiratory chain was augmented in the presence of melatonin. Conversely, in the presence of 1 mM melatonin, decreases in the expression of mitofusins 1 and 2 were detected. The glycolysis and the glycolytic capacity were diminished in cells treated with 1 mM or 100 µM melatonin. Increases in the expression of phosphofructokinase-1 and lactate dehydrogenase were noted in cells incubated with 100 µM, 10 µM, or 1 µM melatonin. The expression of glucose transporter 1 was increased in cells incubated with 10 µM or 1 µM melatonin. Conversely, 1 mM melatonin decreased the expression of all three proteins. Our results suggest that melatonin, at pharmacological concentrations, might modulate mitochondrial physiology and energy metabolism in addition to major pathways involved in pancreatic stellate cell proliferation.

Melatonin Regulates the Daily Levels of Plasma Amino Acids, Acylcarnitines, Biogenic Amines, Sphingomyelins, and Hexoses in a Xenograft Model of Triple Negative Breast Cancer

Metabolic dysregulation as a reflection of specific metabolite production and its utilization is a common feature of many human neoplasms. Melatonin, an indoleamine that is highly available during darkness, has a variety of metabolic functions in solid tumors. Because plasma metabolites undergo circadian changes, we investigated the role of melatonin on the profile of amino acids (AAs), biogenic amines, carnitines, sphingolipids, and hexoses present in the plasma of mice bearing xenograft triple negative breast cancer (MDA-MB-231 cells) over 24 h. Plasma concentrations of nine AAs were reduced by melatonin, especially during the light phase, with a profile closer to that of non-breast cancer (BC) animals. With respect to acylcarnitine levels, melatonin reduced 12 out of 24 molecules in BC-bearing animals compared to their controls, especially at 06:00 h and 15:00 h. Importantly, melatonin reduced the concentrations of asymmetric dimethylarginine, carnosine, histamine, kynurenine, methionine sulfoxide, putrescine, spermidine, spermine, and symmetric dimethylarginine, which are associated with the BC metabolite sets. Melatonin also led to reduced levels of sphingomyelins and hexoses, which showed distinct daily variations over 24 h. These results highlight the role of melatonin in controlling the levels of plasma metabolites in human BC xenografts, which may impact cancer bioenergetics, in addition to emphasizing the need for a more accurate examination of its metabolomic changes at different time points.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

The antioxidant effects of melatonin in blood platelets during exposure to electromagnetic radiation – an in vitro study

Objectives

The article presents the results of an in vitro study aimed at identifying changes in parameters of oxidative stress – concentration of malondialdehyde (MDA), enzymatic activity of superoxide dismutase (SOD-1) and protective antioxidant role of melatonin (MLT) during the exposure of blood platelets to electromagnetic radiation (EMR) emitted by monitors.

Methods

Platelets were exposed to an EMR for 30- and 60 min. generated by monitors (1 kHz frequency, 220 V/m intensity). In each sample the level of SOD-1 activity and concentration of MDA were determined.

Results

The MDA concentration increased significantly after 30-and 60-min. irradiation, as compared to control values (2.53 vs 1.36; 3.64 vs 1.36 nmol/109 blood platelets) and after the addition of MLT it decreased (2.53 vs 1.55; 3.64 vs 1.12 nmol/109 blood platelets). The activity of SOD-1 increased significantly compared to control values after 30 min. and 60 min. of exposure to EMR (1.97vs 0.75; 2.08 vs 0.75 U/g of protein), and significantly decreased after the addition of MLT only in samples exposed for 60 min. (2.08 vs 0.95 U/g of protein).

Discussion

The results demonstrated the possibly negative effect of EMR on oxygen metabolism of blood platelets and indicated a possible protective role of melatonin in this process.

Melatonin as a Therapeutic Agent for the Inhibition of Hypoxia-Induced Tumor Progression: A Description of Possible Mechanisms Involved

Hypoxia has an important role in tumor progression via the up-regulation of growth factors and cellular adaptation genes. These changes promote cell survival, proliferation, invasion, metastasis, angiogenesis, and energy metabolism in favor of cancer development. Hypoxia also plays a central role in determining the resistance of tumors to chemotherapy. Hypoxia of the tumor microenvironment provides an opportunity to develop new therapeutic strategies that may selectively induce apoptosis of the hypoxic cancer cells. Melatonin is well known for its role in the regulation of circadian rhythms and seasonal reproduction. Numerous studies have also documented the anti-cancer properties of melatonin, including anti-proliferation, anti-angiogenesis, and apoptosis promotion. In this paper, we hypothesized that melatonin exerts anti-cancer effects by inhibiting hypoxia-induced pathways. Considering this action, co-administration of melatonin in combination with other therapeutic medications might increase the effectiveness of anti-cancer drugs. In this review, we discussed the possible signaling pathways by which melatonin inhibits hypoxia-induced cancer cell survival, invasion, migration, and metabolism, as well as tumor angiogenesis.

An updated review of mechanistic potentials of melatonin against cancer: pivotal roles in angiogenesis, apoptosis, autophagy, endoplasmic reticulum stress and oxidative stress

Cancers are serious life-threatening diseases which annually are responsible for millions of deaths across the world. Despite many developments in therapeutic approaches for affected individuals, the rate of morbidity and mortality is high. The survival rate and life quality of cancer patients is still low. In addition, the poor prognosis of patients and side effects of the present treatments underscores that finding novel and effective complementary and alternative therapies is a critical issue. Melatonin is a powerful anticancer agent and its efficiency has been widely documented up to now. Melatonin applies its anticancer abilities through affecting various mechanisms including angiogenesis, apoptosis, autophagy, endoplasmic reticulum stress and oxidative stress. Regarding the implication of mentioned cellular processes in cancer pathogenesis, we aimed to further evaluate the anticancer effects of melatonin via these mechanisms.

Melatonin downregulates TRPC6, impairing store-operated calcium entry in triple-negative breast cancer cells

Melatonin has been reported to induce effective reduction in growth and development in a variety of tumors, including breast cancer. In triple-negative breast cancer (TNBC) cells, melatonin attenuates a variety of cancer features, such as tumor growth and apoptosis resistance, through a number of still poorly characterized mechanisms. One biological process that is important for TNBC cells is store-operated Ca2+ entry (SOCE), which is modulated by TRPC6 expression and function. We wondered whether melatonin might intersect with this pathway as part of its anticancer activity. We show that melatonin, in the nanomolar range, significantly attenuates TNBC MDA-MB-231 cell viability, proliferation, and migration in a time- and concentration-dependent manner, without having any effect on nontumoral breast epithelial MCF10A cells. Pretreatment with different concentrations of melatonin significantly reduced SOCE in MDA-MB-231 cells without altering Ca2+ release from the intracellular stores. By contrast, SOCE in MCF10A cells was unaffected by melatonin. In the TNBC MDA-MB-468 cell line, melatonin not only attenuated viability, migration, and SOCE, but also reduced TRPC6 expression in a time- and concentration-dependent manner, without altering expression or function of the Ca2+ channel Orai1. The expression of exogenous TRPC6 overcame the effect of melatonin on SOCE and cell proliferation, and silencing or inhibition of TRPC6 impaired the inhibitory effect of melatonin on SOCE. These findings indicate that TRPC6 downregulation might be involved in melatonin's inhibitory effects on Ca2+ influx and the maintenance of cancer hallmarks and point toward a novel antitumoral mechanism of melatonin in TNBC cells.

Towards an Integral Therapeutic Protocol for Breast Cancer Based upon the New H+-Centered Anticancer Paradigm of the Late Post-Warburg Era

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H+) dynamics of cancer, allows for the understanding and integration of the many dualisms, confusions, and paradoxes of the disease. The new H+-related, wide-ranging model can embrace, from a unique perspective, the many aspects of the disease and, at the same time, therapeutically interfere with most, if not all, of the hallmarks of cancer known to date. The pH-related armamentarium available for the treatment of BC reviewed here may be beneficial for all types and stages of the disease. In this vein, we have attempted a megasynthesis of traditional and new knowledge in the different areas of breast cancer research and treatment based upon the wide-ranging approach afforded by the hydrogen ion dynamics of cancer. The concerted utilization of the pH-related drugs that are available nowadays for the treatment of breast cancer is advanced.

Melatonin modulates proliferation of pancreatic stellate cells through caspase-3 activation and changes in cyclin A and D expression

In this study, the effects of melatonin (1 μM-1 mM) on pancreatic stellate cells (PSC) have been examined. Cell viability and proliferation, caspase-3 activation, and the expression of cyclin A and cyclin D were analyzed. Our results show that melatonin decreased PSC viability in a time- and concentration-dependent manner. This effect was not inhibited by treatment of cells with MT1, MT2, calmodulin, or ROR-alpha inhibitors prior to melatonin addition. Activation of caspase-3 in response to melatonin was detected. The expression of cyclin A and cyclin D was decreased in cells treated with melatonin. Finally, changes in BrdU incorporation into the newly synthesized DNA of proliferating cells were also observed in the presence of melatonin. We conclude that melatonin, at pharmacological concentrations, modulates proliferation of PSC through activation of apoptosis and involving crucial regulators of the cell cycle. These actions might not require specific melatonin receptors. Our observations suggest that melatonin, at high doses, could potentially exert anti-fibrotic effects and, thus, could be taken into consideration as supportive treatment in the therapy of pancreatic diseases.

A New and Integral Approach to the Etiopathogenesis and Treatment of Breast Cancer Based upon Its Hydrogen Ion Dynamics

Despite all efforts, the treatment of breast cancer (BC) cannot be considered to be a success story. The advances in surgery, chemotherapy and radiotherapy have not been sufficient at all. Indeed, the accumulated experience clearly indicates that new perspectives and non-main stream approaches are needed to better characterize the etiopathogenesis and treatment of this disease. This contribution deals with how the new pH-centric anticancer paradigm plays a fundamental role in reaching a more integral understanding of the etiology, pathogenesis, and treatment of this multifactorial disease. For the first time, the armamentarium available for the treatment of the different types and phases of BC is approached here from a Unitarian perspective-based upon the hydrogen ion dynamics of cancer. The wide-ranged pH-related molecular, biochemical and metabolic model is able to embrace most of the fields and subfields of breast cancer etiopathogenesis and treatment. This single and integrated approach allows advancing towards a unidirectional, concerted and synergistic program of treatment. Further efforts in this line are likely to first improve the therapeutics of each subtype of this tumor and every individual patient in every phase of the disease.

Targeting Glucose Transporters for Breast Cancer Therapy: The Effect of Natural and Synthetic Compounds

Reprogramming of cellular energy metabolism is widely accepted to be a cancer hallmark. The deviant energetic metabolism of cancer cells-known as the Warburg effect-consists in much higher rates of glucose uptake and glycolytic oxidation coupled with the production of lactic acid, even in the presence of oxygen. Consequently, cancer cells have higher glucose needs and thus display a higher sensitivity to glucose deprivation-induced death than normal cells. So, inhibitors of glucose uptake are potential therapeutic targets in cancer. Breast cancer is the most commonly diagnosed cancer and a leading cause of cancer death in women worldwide. Overexpression of facilitative glucose transporters (GLUT), mainly GLUT1, in breast cancer cells is firmly established, and the consequences of GLUT inhibition and/or knockout are under investigation. Herein we review the compounds, both of natural and synthetic origin, found to interfere with uptake of glucose by breast cancer cells, and the consequences of interference with that mechanism on breast cancer cell biology. We will also present data where the interaction with GLUT is exploited in order to increase the efficiency or selectivity of anticancer agents, in breast cancer cells.

Cell-in-Cell Phenomenon and Its Relationship With Tumor Microenvironment and Tumor Progression: A Review

The term cell-in-cell, morphologically, refers to the presence of one cell within another. This phenomenon can occur in tumors but also among non-tumor cells. The cell-in-cell phenomenon was first observed 100 years ago, and it has since been found in a variety of tumor types. Recently, increasing attention has been paid to this phenomenon and the underlying mechanism has gradually been elucidated. There are three main related process: cannibalism, emperipolesis, and entosis. These processes are affected by many factors, including the tumor microenvironment, mitosis, and genetic factors. There is considerable evidence to suggest that the cell-in-cell phenomenon is associated with the prognosis of cancers, and it promotes tumor progression in most situations. Notably, in pancreatic cancer, the cell-in-cell phenomenon is associated with reduced metastasis, which is the opposite of what happens in other tumor types. Thus, it can also inhibit tumor progression. Studies show that cell-in-cell structure formation is affected by the tumor microenvironment, and that it may lead to changes in cellular characteristics. In this review, we summarize the different cell-in-cell processes and discuss their role in tumor progression and how they are regulated by different mechanisms.

Antiproliferative activity and p53 upregulation effects of chalcones on human breast cancer cells

Chalcones are valuable structures for drug discovery due to their broad bioactivity spectrum. In this study, we evaluated 20 synthetic chalcones against estrogen-receptor-positive breast cancer cells (MCF-7 line) and triple-negative breast cancer (TNBC) cells (MDA-MB-231 line). Antiproliferative screening by MTT assay resulted in two most active compounds: 2-fluoro-4’-aminochalcone (11) and 3-pyridyl-4’-aminochalcone (17). Their IC₅₀ values ranged from 13.2 to 34.7 µM against both cell lines. Selected chalcones are weak basic compounds and maintained their antiproliferative activity under acidosis conditions (pH 6.7), indicating their resistance to ion-trapping effect. The mode of breast cancer cells death was investigated and chalcones 11 and 17 were able to induce apoptosis rather than necrosis in both lines. Antiproliferative target investigations with MCF-7 cells suggested 11 and 17 upregulated p53 protein expression and did not affect Sp1 protein expression. Future studies on chalcones 11 and 17 can define their in vivo therapeutic potential.