Melatonin combined with endoplasmic reticulum stress induces cell death via the PI3K/Akt/mTOR pathway in B16F10 melanoma cells

Tanshinone IIA induces ER stress and JNK activation to inhibit tumor growth and enhance anti-PD-1 immunotherapy in non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) remains at the forefront of new cancer cases, and there is an urgent need to find new treatments or improve the efficacy of existing therapies. In addition to the application in the field of cerebrovascular diseases, recent studies have revealed that tanshinone IIA (Tan IIA) has anticancer activity in a variety of cancers.

PURPOSE

To investigate the potential anticancer mechanism of Tan IIA and its impact on immunotherapy in NSCLC.

METHODS

Cytotoxicity and colony formation assays were used to detect the Tan IIA inhibitory effect on NSCLC cells. This research clarified the mechanisms of Tan IIA in anti-tumor and programmed death-ligand 1 (PD-L1) regulation by using flow cytometry, transient transfection, western blotting and immunohistochemistry (IHC) methods. Besides, IHC was also used to analyze the nuclear factor of activated T cells 1 (NFAT2) expression in NSCLC clinical samples. Two animal models including xenograft mouse model and Lewis lung cancer model were used for evaluating tumor suppressive efficacy of Tan IIA. We also tested the efficacy of Tan IIA combined with programmed cell death protein 1 (PD-1) inhibitors in Lewis lung cancer model.

RESULTS

Tan IIA exhibited good NSCLC inhibitory effect which was accompanied by endoplasmic reticulum (ER) stress response and increasing Ca2+ levels. Moreover, Tan IIA could suppress the NFAT2/ Myc proto oncogene protein (c-Myc) signaling, and it also was able to control the Jun Proto-Oncogene(c-Jun)/PD-L1 axis in NSCLC cells through the c-Jun N-terminal kinase (JNK) pathway. High NFAT2 levels were potential factors for poor prognosis in NSCLC patients. Finally, animal experiments data showed a stronger immune activation phenotype, when we performed treatment of Tan IIA combined with PD-1 monoclonal antibody.

CONCLUSION

The findings of our research suggested a novel mechanism for Tan IIA to inhibit NSCLC, which could exert anti-cancer effects through the JNK/NFAT2/c-Myc pathway. Furthermore, Tan IIA could regulate tumor PD-L1 levels and has the potential to improve the efficacy of PD-1 inhibitors.

Melatonin improves the viability and ultrastructure of bovine oocyte-granulosa complexes of in vitro cultured early antral follicles

This study aims to investigate the effects of melatonin on follicular growth, viability and ultrastructure, as well as on the levels of mRNA for antioxidant enzymes, reactive oxygen species (ROS) and meiotic progression in oocytes from in vitro cultured bovine early antral follicles. To this end, isolated early antral follicles (500-600 μm) were cultured in TCM-199+ alone or supplemented with 10-6 , 10-7 or 10-8  M melatonin at 38.5°C with 5% CO2 for 8 days. Follicle diameters were evaluated at days 0, 4 and 8 of culture. At the end of culture, ultrastructure, chromatin configuration, viability (calcein-AM and ethidium homodimer-1 staining), and the levels of ROS and mRNA for catalase (CAT), superoxide dismutase (SOD) and peroxiredoxin 6 (PRDX6) and glutathione peroxidase (GPx) were investigated in oocyte-granulosa cell complexes (OGCs). The results showed that early antral follicles cultured with 10-6 and 10-8  M melatonin had a progressive and significant increase in their diameters throughout the culture period (p < .05). Additionally, oocytes from follicles cultured with 10-7 or 10-8  M melatonin had increased fluorescence for calcein-AM, while those cultured with 10-6 or 10-7  M had reduced fluorescence for ethidium homodimer-1. Different from follicles cultured in other treatments, those cultured with 10-8  M melatonin had well-preserved ultrastructure of oocyte and granulosa cells. Melatonin, however, did not influence the levels of ROS, the mitochondrial activity, oocyte meiotic resumption and expression mRNA for SOD, CAT, GPX1 and PRDX6. In conclusion, the presence of 10-8  M melatonin in culture medium improves viability and preserves the ultrastructure of oocyte and granulosa cells of early antral follicles cultured in vitro.

The STING-IRF3 Signaling Pathway, Mediated by Endoplasmic Reticulum Stress, Contributes to Impaired Myocardial Autophagic Flux After Ischemia/Reperfusion

ABSTRACT

This study aimed to determine whether endoplasmic reticulum (ER) stress is involved in impaired autophagy after myocardial ischemia/reperfusion (M-I/R) and elucidate the underlying mechanisms. The expression levels of stimulator of interferon gene (STING) and interferon regulatory transcription factor 3 (IRF3) phosphorylation increased in M-I/R heart tissues and hypoxia-treated/reoxygenation-treated H9c2 cells. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) significantly suppressed the stimulation of STING-IRF3 transcription and alleviated cardiac dysfunction caused by M-I/R injury. In addition, 4-PBA reversed ischemia-induced/reperfusion-induced autophagic flux dysfunction, as demonstrated by a decrease in p 62 and LC3 levels. Similarly, the protective effect of STING deficiency on myocardial cell damage was achieved by the recovery of autophagic flux. Conversely, the protective effect of 4-PBA against hypoxia/reoxygenation injury in cardiomyocytes was offset by STING overexpression, wherein the activated STING-IRF3 pathway promoted the expression of Rubicon (a negatively-regulated autophagic molecule) by binding to the Rubicon promoter. Rubicon ablation effectively counteracts the adverse effects of STING overexpression in cardiomyocytes. The data showed that STING-IRF3 signaling of ER stress receptors is particularly important in the progression of physiological M-I/R caused by the inhibition of autophagic flow in vivo and in vitro.

Cucurbitacin B induces apoptosis in colorectal cells through reactive oxygen species generation and endoplasmic reticulum stress pathways

Cucurbitacin B (CuB) is a member of the cucurbitacin family, which has shown potent anticancer pharmacological activity. Prolonged or severe endoplasmic reticulum stress (ERS) induces apoptosis; therefore, the present study investigated whether CuB may activate the ERS pathway to induce apoptosis. HT-29 and SW620 colorectal cancer (CRC) cells were treated with a range of concentrations of CuB for 48 h, and the viability and proliferation of cells were determined using Cell Counting Kit 8 (CCK8) and colony formation assays. Subsequently, the appropriate CuB concentration (5 µM) was selected for treatment of CRC cells for 48 h. Western blot analysis was used to measure the expression levels of ERS-related proteins, flow cytometry was used to evaluate apoptosis, the dichlorodihydrofluorescein diacetate fluorescent probe was used to detect reactive oxygen species (ROS) production, and the relationship between ROS and ERS was determined by western blot analysis. Furthermore, flow cytometry was used to evaluate apoptosis after treatment with the ERS inhibitor 4-phenylbutyric acid, the ROS inhibitor N-acetylcysteine and following knockdown of CHOP expression. In addition, western blot analysis was performed to measure Bax and Bcl2 protein expression levels, and a CCK8 assay was performed to evaluate the viability of cells following knockdown of CHOP. Notably, CuB treatment increased apoptosis and inhibited cell proliferation in CRC cell lines, and these effects were mediated by ROS and ROS-regulated activation of the PERK and XBP1 ERS pathways. In conclusion, CuB may induce apoptosis in HT-29 and SW620 CRC cells via ROS and ERS.

Melatonin as a regulator of apoptosis in leukaemia: molecular mechanism and therapeutic perspectives

Leukaemia is a dangerous malignancy that causes thousands of deaths every year throughout the world. The rate of morbidity and mortality is significant despite many advancements in therapy strategies for affected individuals. Most antitumour medications used now in clinical oncology use apoptotic signalling pathways to induce cancer cell death. Accumulated data have shown a direct correlation between inducing apoptosis in cancer cells with higher tumour regression and survival. Until now, the efficacy of melatonin as a powerful antitumour agent has been firmly established. A change in melatonin concentrations has been reported in multiple tumours such as endometrial, hematopoietic, and breast cancers. Findings show that melatonin's anticancer properties, such as its prooxidation function and ability to promote apoptosis, indicate the possibility of utilizing this natural substance as a promising agent in innovative cancer therapy approaches. Melatonin stimulates cell apoptosis via the regulation of many apoptosis facilitators, including mitochondria, cytochrome c, Bcl-2, production of reactive oxygen species, and apoptosis receptors. This paper aimed to further assess the anticancer effects of melatonin through the apoptotic pathway, considering the role that cellular apoptosis plays in the pathogenesis of cancer. The effect of melatonin may mean that it is appropriate for use as an adjuvant, along with other therapeutic approaches such as radiotherapy and chemotherapy.

Melatonin induces cell cycle arrest and suppresses tumor invasion in urinary bladder urothelial carcinoma

Urinary bladder urothelial carcinoma (UBUC) encompasses about 90% of all bladder cancer cases, and the mainstream treatment is the transurethral resection of the bladder tumor followed by intravesical instillation. High rates of mortality, recurrence, and progression in bladder cancer have stimulated the search for alternative adjuvant therapies. The aim of this study was to investigate the potential of melatonin as adjuvant therapy in bladder cancer. Cell viability and clonogenic ability were assessed by an MTT assay and colony formation. Cell cycle and apoptosis analysis were performed by flow cytometry and Hoechst 33342 staining, while cell metastasis capacity was measured by wound healing and transwell assays. Potential mechanisms were investigated by an oncology array and verified via western blotting. The melatonin treatment significantly reduced T24 and UMUC3 bladder cancer cell proliferation and clonogenic ability. G1 arrest and sub-G1 accumulation in the T24 and UMUC3 cells led to cell proliferation suppression and cell death, and Hoechst 33342 staining further verified the apoptosis induction directly by melatonin. Moreover, melatonin weakened cell motility and invasiveness. Based on the oncology array results, we demonstrated that melatonin exerts its anti-cancer effect by down-regulating the HIF-1α and NF-κB pathways and downstream pathways, including Bcl-2, leading to cell cycle arrest and apoptosis induction in the UBUC cells. Overall, these findings support the potential of melatonin as adjuvant therapy in bladder cancer.

Mechanism of action and promising clinical application of melatonin from a dermatological perspective

Melatonin is the main neuroendocrine product in the pineal gland. Melatonin can regulate circadian rhythm-related physiological processes. Evidence indicates an important role of melatonin in hair follicles, skin, and gut. There appears to be a close association between melatonin and skin disorders. In this review, we focus on the latest research of the biochemical activities of melatonin (especially in the skin) and its promising clinical applications.

The role of unfolded protein response-associated miRNAs in immunogenic cell death amplification: A literature review and bioinformatics analysis

Immunogenic cell death (ICD) is a type of cellular death that is elicited in response to the specific types of anti-cancer therapies and enhances the anti-tumor immune responses by the combination of antigenicity and adjuvanticity of dying tumor cells. There is a well-established interlink between endoplasmic reticulum stress (ERS) and ICD elicited by anti-cancer therapies. Most recent evidences support that unfolded protein response (UPR)-associated miRNAs can be key players in the ERS-induced ICD. Hence, in the present study, we conducted a literature review on the role of these miRNAs and associated molecular pathways that may regulate ICD. We first collected UPR-associated miRNAs that promote ERS-induced apoptosis and then focused on microRNAs (miRNAs) that promote ERS-induced apoptosis via PERK/eIF2α/ATF4/CHOP pathway activation, as the main core for ICD and release of damage-associated molecular patterns. To better identify PERK/eIF2α/ATF4/CHOP pathway-inducing miRNAs that can be used as potential therapeutic targets for improving ICD in cancer treatment, we did a comprehensive bioinformatics analysis and network construction. Our results showed that "pathways in cancer", "MAPK signaling pathway", "PI3K-Akt signaling pathway", and "Cellular senescence", which correlate with UPR components and ERS induction, were among the significant signaling pathways related to the target genes of these miRNAs. Furthermore, a protein-protein interaction (PPI) network was constructed, which revealed the involvement of the PPI-extracted hub genes in the regulation of proliferation and apoptosis. In conclusion, we propose that these types of miRNAs can be considered as the potential cancer therapy options for better induction of ICD in combination with other ICD inducers.

Melatonin as a Repurposed Drug for Melanoma Treatment

Melanoma is the most aggressive type of skin cancer, with a greater risk of metastasis and a higher prevalence and mortality rate. This cancer type has been demonstrated to develop resistance to the known treatment options such as conventional therapeutic agents and targeted therapy that are currently being used as the standard of care. Drug repurposing has been explored as a potential alternative treatment strategy against disease pathophysiologies, including melanoma. To that end, multiple studies have suggested that melatonin produced by the pineal gland possesses anti-proliferative and oncostatic effects in experimental melanoma models. The anticarcinogenic activity of melatonin is attributed to its ability to target a variety of oncogenic signaling pathways, including the MAPK pathways which are involved in regulating the behavior of cancer cells, including cell survival and proliferation. Additionally, preclinical studies have demonstrated that melatonin in combination with chemotherapeutic agents exerts synergistic effects against melanoma. The goal of this review is to highlight the mechanistic insights of melatonin as a monotherapy or combinational therapy for melanoma treatment.

Interactions of melatonin with various signaling pathways: implications for cancer therapy

Melatonin is a neuro-hormone with conserved roles in evolution. Initially synthetized as an antioxidant molecule, it has gained prominence as a key molecule in the regulation of the circadian rhythm. Melatonin exerts its effect by binding to cytoplasmic and intra-nuclear receptors, and is able to regulate the expression of key mediators of different signaling pathways. This ability has led scholars to investigate the role of melatonin in reversing the process of carcinogenesis, a process in which many signaling pathways are involved, and regulating these pathways may be of clinical significance. In this review, the role of melatonin in regulating multiple signaling pathways with important roles in cancer progression is discussed, and evidence regarding the beneficence of targeting malignancies with this approach is presented.

Melatonin Induces Autophagy via Reactive Oxygen Species-Mediated Endoplasmic Reticulum Stress Pathway in Colorectal Cancer Cells

Even though an increasing number of anticancer treatments have been discovered, the mortality rates of colorectal cancer (CRC) have still been high in the past few years. It has been discovered that melatonin has pro-apoptotic properties and counteracts inflammation, proliferation, angiogenesis, cell invasion, and cell migration. In previous studies, melatonin has been shown to have an anticancer effect in multiple tumors, including CRC, but the underlying mechanisms of melatonin action on CRC have not been fully explored. Thus, in this study, we investigated the role of autophagy pathways in CRC cells treated with melatonin. In vitro CRC cell models, HT-29, SW48, and Caco-2, were treated with melatonin. CRC cell death, oxidative stress, and autophagic vacuoles formation were induced by melatonin in a dose-dependent manner. Several autophagy pathways were examined, including the endoplasmic reticulum (ER) stress, 5′–adenosine monophosphate-activated protein kinase (AMPK), phosphoinositide 3-kinase (PI3K), serine/threonine-specific protein kinase (Akt), and mammalian target of rapamycin (mTOR) signaling pathways. Our results showed that melatonin significantly induced autophagy via the ER stress pathway in CRC cells. In conclusion, melatonin demonstrated a potential as an anticancer drug for CRC.

Melatonin as an Adjuvant to Antiangiogenic Cancer Treatments

Melatonin is a hormone with different functions, antitumor actions being one of the most studied. Among its antitumor mechanisms is its ability to inhibit angiogenesis. Melatonin shows antiangiogenic effects in several types of tumors. Combination of melatonin and chemotherapeutic agents have a synergistic effect inhibiting angiogenesis. One of the undesirable effects of chemotherapy is the induction of pro-angiogenic factors, whilst the addition of melatonin is able to overcome these undesirable effects. This protective effect of the pineal hormone against angiogenesis might be one of the mechanisms underlying its anticancer effect, explaining, at least in part, why melatonin administration increases the sensitivity of tumors to the inhibitory effects exerted by ordinary chemotherapeutic agents. Melatonin has the ability to turn cancer totally resistant to chemotherapeutic agents into a more sensitive chemotherapy state. Definitely, melatonin regulates the expression and/or activity of many factors involved in angiogenesis which levels are affected (either positively or negatively) by chemotherapeutic agents. In addition, the pineal hormone has been proposed as a radiosensitizer, increasing the oncostatic effects of radiation on tumor cells. This review serves as a synopsis of the interaction between melatonin and angiogenesis, and we will outline some antiangiogenic mechanisms through which melatonin sensitizes cancer cells to treatments, such as radiotherapy or chemotherapy.

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.

Mitochondrial function is controlled by melatonin and its metabolites in vitro in human melanoma cells

Melanoma is a leading cause of cancer deaths worldwide. Although immunotherapy has revolutionized the treatment for some patients, resistance towards therapy and unwanted side effects remain a problem for numerous individuals. Broad anti-cancer activities of melatonin are recognized; however, additional investigations still need to be elucidated. Herein, using various human melanoma cell models, we explore in vitro the new insights into the regulation of melanoma by melatonin and its metabolites which possess, on the other side, high safety profiles and biological meaningful. In this study, using melanotic (MNT-1) and amelanotic (A375, G361, Sk-Mel-28) melanoma cell lines, the comparative oncostatic responses, the impact on melanin content (for melanotic MNT-1 melanoma cells) as well as the mitochondrial function controlled by melatonin, its precursor (serotonin), a kynuric (N¹ -acetyl-N² -formyl-5-methoxykynuramine, AFMK) and indolic pathway (6-hydroxymelatonin, 6(OH)MEL and 5-methoxytryptamine, 5-MT) metabolites were assessed. Namely, significant disturbances were observed in bioenergetics as follows: (i) uncoupling of oxidative phosphorylation (OXPHOS), (ii) attenuation of glycolysis, (iii) dissipation of mitochondrial transmembrane potential (mtΔΨ) accompanied by (iv) massive generation of reactive oxygen species (ROS), and (v) decrease of glucose uptake. Collectively, these results together with previously published reports provide a new biological potential and make an imperative to consider using melatonin or its metabolites for complementary future treatments of melanoma-affected patients; however, these associations should be additionally investigated in clinical setting.

Melatonin and Cancer: A Polyhedral Network Where the Source Matters

Melatonin is one of the most phylogenetically conserved signals in biology. Although its original function was probably related to its antioxidant capacity, this indoleamine has been “adopted” by multicellular organisms as the “darkness signal” when secreted in a circadian manner and is acutely suppressed by light at night by the pineal gland. However, melatonin is also produced by other tissues, which constitute its extrapineal sources. Apart from its undisputed chronobiotic function, melatonin exerts antioxidant, immunomodulatory, pro-apoptotic, antiproliferative, and anti-angiogenic effects, with all these properties making it a powerful antitumor agent. Indeed, this activity has been demonstrated to be mediated by interfering with various cancer hallmarks, and different epidemiological studies have also linked light at night (melatonin suppression) with a higher incidence of different types of cancer. In 2007, the World Health Organization classified night shift work as a probable carcinogen due to circadian disruption, where melatonin plays a central role. Our aim is to review, from a global perspective, the role of melatonin both from pineal and extrapineal origin, as well as their possible interplay, as an intrinsic factor in the incidence, development, and progression of cancer. Particular emphasis will be placed not only on those mechanisms related to melatonin’s antioxidant nature but also on the recently described novel roles of melatonin in microbiota and epigenetic regulation.

Molecular Mechanisms of Melatonin-Mediated Cell Protection and Signaling in Health and Disease

Melatonin, an endogenously synthesized indolamine, is a powerful antioxidant exerting beneficial action in many pathological conditions. Melatonin protects from oxidative stress in ischemic/reperfusion injury, neurodegenerative diseases, and aging, decreases inflammation, modulates the immune system, inhibits proliferation, counteracts the Warburg effect, and promotes apoptosis in various cancer models. Melatonin stimulates antioxidant enzymes in the cells, protects mitochondrial membrane phospholipids, especially cardiolipin, from oxidation thus preserving integrity of the membranes, affects mitochondrial membrane potential, stimulates activity of respiratory chain enzymes, and decreases the opening of mitochondrial permeability transition pore and cytochrome c release. This review will focus on the molecular mechanisms of melatonin effects in the cells during normal and pathological conditions and possible melatonin clinical applications.

Zinc application alleviates the adverse renal effects of arsenic stress in a protein quality control way in common carp

The potential antagonistic mechanism between zinc (Zn) and arsenic (As) on renal toxicity was investigated in common carp. The results showed that by increased Zn efflux and retention (as reflected by zinc transporter 1 (ZnT-1), Zrt- and Irt- 1ike protein (ZIP) and metallothionein (MT) expression), Zn co-administration significantly recovered the antioxidant function (catalase, CAT) and the level of renal barrier function (Occludin, Claudins and Zonula Occludens) in comparison to As treatment. Interestingly, Zn co-administration with As resulted in carps undergoing reduction of heat shock response (HSPs), a low induction of autophagy flux (Beclin-1, microtubule-associated protein 1 light chain 3 (LC3) and sequestosome 1 (P62)) and decreased endoplasmic reticulum (ER) stress (activating transcription factor 6 (ATF-6), inositol requiring-1α (IRE1) and PKR-like ER kinase (PERK)) in the aspect of mRNA or protein levels. All these alleviated protein quality control processes induced by Zn under As stress was correlated with the no longer loosen tight connection, less swollen endoplasmic reticulum as well as reduced formation of autophagosomes and autophagic vesicles. Mechanically, post-transcriptional regulated protein quantities compromising phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway was demonstrated true causative forces inside the cell for Zn against As poisoning. In conclusion, we suggested the potential renal protective effect of Zn supplementation against As exposure by the modulation of protein quality control processes.

Cyst Reduction by Melatonin in a Novel Drosophila Model of Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) causes progressive cystic degeneration of the renal tubules, the nephrons, eventually severely compromising kidney function. ADPKD is incurable, with half of the patients eventually needing renal replacement. Treatments for ADPKD patients are limited and new effective therapeutics are needed. Melatonin, a central metabolic regulator conserved across all life kingdoms, exhibits oncostatic and oncoprotective activity and no detected toxicity. Here, we used the Bicaudal C (BicC) Drosophila model of polycystic kidney disease to test the cyst-reducing potential of melatonin. Significant cyst reduction was found in the renal (Malpighian) tubules upon melatonin administration and suggest mechanistic sophistication. Similar to vertebrate PKD, the BicC fly PKD model responds to the antiproliferative drugs rapamycin and mimics of the second mitochondria-derived activator of caspases (Smac). Melatonin appears to be a new cyst-reducing molecule with attractive properties as a potential candidate for PKD treatment.

Naringin Combined with NF-κB Inhibition and Endoplasmic Reticulum Stress Induces Apoptotic Cell Death via Oxidative Stress and the PERK/eIF2α/ATF4/CHOP Axis in HT29 Colon Cancer Cells

Currently, combination therapy is considered the most effective solution for a selective chemotherapeutic effect in the treatment of colon cancer. This study investigated the death of both colon cancer HT29 cells and healthy vascular smooth muscle TG-Ha-VSMC cells (VSMCs) induced by naringin combined with endoplasmic reticulum (ER) stress and NF-κB inhibition. Naringin combined with tunicamycin and BAY 11-7082 suppressed the proliferation of HT29 cells in a dose-dependent manner and induced particularly apoptotic death without significantly affecting healthy VSMCs according to Annexin V/PI staining and AO/EB staining analyses. Insufficient antioxidant defense and heat shock response as well as excessive ROS generation were observed in HT29 cells following combination therapy. Quantitative real-time PCR and western blot analysis demonstrated that drug combination-induced mitochondrial apoptosis was activated through the ROS-mediated PERK/eIF2α/ATF4/CHOP pathway. Additionally, naringin combination significantly reduced the sXBP expression induced by tunicamycin+BAY 11-7082 in a dose-dependent manner. In conclusion, this study found that naringin combined with tunicamycin+BAY 11-7082 efficiently induced apoptotic cell death in HT29 colon cancer cells via oxidative stress and the PERK/eIF2α/ATF4/CHOP pathway, suggesting that naringin combined with tunicamycin plus BAY 11-7082 could be a new combination therapy strategy for effective colon cancer treatment with minimal side effects on healthy cells.

Melatonin and urological cancers: a new therapeutic approach

Urological cancers are responsible for thousands of cancer-related deaths around the world. Despite all developments in therapeutic approaches for cancer therapy, the absence of efficient treatments is a critical and vital problematic issue for physicians and researchers. Furthermore, routine medical therapies contribute to several undesirable adverse events for patients, reducing life quality and survival time. Therefore, many attempts are needed to explore potent alternative or complementary treatments for great outcomes. Melatonin has multiple beneficial potential effects, including anticancer properties. Melatonin in combination with chemoradiation therapy or even alone could suppress urological cancers through affecting essential cellular pathways. This review discusses current evidence reporting the beneficial effect of melatonin in urological malignancies, including prostate cancer, bladder cancer, and renal cancer.

Melatonin regulates chicken granulosa cell proliferation and apoptosis by activating the mTOR signaling pathway via its receptors

Melatonin is a key regulator of follicle granular cell maturation and ovulation. The mammalian target of rapamycin (mTOR) pathway plays an important role in cell growth regulation. Therefore, our aim was to investigate whether the mTOR signaling pathway is involved in the regulation of melatonin-mediated proliferation and apoptotic mechanisms in granulosa cells. Chicken follicle granular cells were cultured with melatonin (0, 2, 20, or 200 μmol/L) for 48 h. The results showed that melatonin treatment enhanced proliferation and suppressed apoptosis in granular cells at 20 μmol/L and 200 μmol/L (P < 0.05) by upregulation of cyclin D1 (P < 0.01) and Bcl-2 (P < 0.01) and downregulation of P21, caspase-3, Beclin1, and LC3-II (P < 0.01). The effects resulted in the activation of the mTOR signaling pathway by increasing the expression of avTOR, PKC, 4E-BP1, S6K (P < 0.05), p-mTOR, and p-S6K. We added an mTOR activator and inhibitor to the cells and identified the optimal dose (10 μmol/L MHY1485 and 100 nmol/L rapamycin) for subsequent experiments. The combination of 20 μmol/L melatonin and 10 μmol/L MHY1485 significantly enhanced granulosa cell proliferation (P < 0.05), while 100 nmol/L rapamycin significantly inhibited proliferation and enhanced apoptosis (P < 0.05), but this action was reversed in the 20-μmol/L melatonin and 100-nmol/L rapamycin cotreatment groups (P < 0.05). This was confirmed by mRNA and protein expression that was associated with proliferation, apoptosis, and autophagy (P < 0.05). The combination of 20 μmol/L melatonin and 10 μmol/L MHY1485 also activated the mTOR pathway upstream genes PI3K, AKT1, and AKT2 and downstream genes PKC, 4E-BP1, and S6K (P < 0.05), as well as protein expression of p-mTOR and p-S6K. Rapamycin significantly inhibited the mTOR pathway-related genes mRNA levels (P < 0.05). In addition, activation of the mTOR pathway increased melatonin receptor mRNA levels (P < 0.05). In conclusion, these findings demonstrate that melatonin regulates chicken granulosa cell proliferation and apoptosis by activating the mTOR signaling pathway via its receptor.

MCM7 silencing promotes cutaneous melanoma cell autophagy and apoptosis by inactivating the AKT1/mTOR signaling pathway

Cutaneous melanoma (CM) has become a major public health concern. Studies illustrate that minichromosome maintenance protein 7 (MCM7) participate in various diseases including skin disease. Our study aimed to study the effects of MCM7 silencing on CM cell autophagy and apoptosis by modulating the AKT threonine kinase 1 (AKT1)/mechanistic target of rapamycin kinase (mTOR) signaling pathway. Initially, microarray analysis was used to screen the CM-related gene expression data as well as differentially expressed genes. Subsequently, MCM7 expression vector and lentivirus RNA used for MCM7 silencing (LV-shRNA-MCM7) were constructed, and these vectors, dimethyl sulfoxide (DMSO) and AKT activator SC79 were then introduced into CM cell line SK-MEL-2 to validate the role of MCM7 in cell autophagy, viability, apoptosis, cell cycle, migration, and invasion. To further investigate the regulatory mechanisms of MCM7 in CM progress, the expression of MCM7, AKT1, mTOR, cyclin D1, as well as autophagy and apoptosis relative factors, such as LC3B, SOD2, DJ-1, p62, Bcl-2, Bax, and caspase-3 in melanoma cells was determined. MCM7 might mediate the AKT1/mTOR signaling pathway to influence the progress of melanoma. MCM7 silencing contributed to the increased expression of Bax, capase-3, and autophagy-related genes (LC3B, SOD2, and DJ-1), but decreased the expression of Bcl-2, which suggested that MCM7 silencing promoted autophagy and cell apoptosis. At the same time, MCM7 silencing also attenuated cell viability, invasion, and migration, and reduced the cyclin D1 expression and protein levels of p-AKT1 and p-mTOR. Taken together, MCM7 silencing inhibited CM via inactivation of the AKT1/mTOR signaling pathway.

Melatonin-Induced Cytoskeleton Reorganization Leads to Inhibition of Melanoma Cancer Cell Proliferation

Neuroindole melatonin, a hormone synthesized during the night mainly-but not exclusively-by the pineal gland of all vertebrates, functions as an adapting signal to the light-dark cycle. Its antioxidant, neuroprotective, anti-inflammatory, and antitumor properties are all well-known and widely reported. Melanoma is one of the most common carcinomas among developed countries and a type of tumor particularly difficult to fight back in medium/advanced stages. In contrast to other types of cancer, influence of melatonin on melanoma has been scarcely investigated. Thus, we have chosen the murine melanoma model B16-F10 cell line to study antiproliferative and antitumoral actions of melatonin. For this purpose, we combined both, cell culture and in vivo models. Melatonin reduced either, growth rate or migration of B16-F10 cells. Furthermore, melanin synthesis was altered by melatonin, promoting its synthesis. Melatonin also induced a G2/M cell cycle arrest and altered the cytoskeletal organization. To corroborate these results, we tested the effect of melatonin in the in vivo model of B16-F10 cell injection in the tail vein, which causes numerous lung metastases. Two different strategies of melatonin administration were used, namely, in drinking water, or daily intraperitoneal injection. However, contrary to what occurred in cell culture, no differences were observed between control and melatonin treated groups. Results obtained led us to conclude that melatonin exerts an antiproliferative and anti-migrating effect on this melanoma model by interfering with the cytoskeleton organization, but this pharmacological effect cannot be translated in vivo as the indole did not prevent metastasis in the murine model, suggesting that further insights into the effects of the indole in melanoma cells should be approached to understand this apparent paradox.

Melatonin: An important anticancer agent in colorectal cancer

Colorectal cancer is one of the most common cancers among the elderly, which is also seen in the forms of hereditary syndromes occurring in younger individuals. Numerous studies have been conducted to understand the molecular and cellular pathobiology underlying colorectal cancer. These studies have found that cellular signaling pathways are at the core of colorectal cancer pathology. Because of this, new agents have been proposed as possible candidates to accompany routine therapy regimens. One of these agents is melatonin, a neuro-hormone known best for its essential role in upholding the circadian rhythm and orchestrating the many physiologic changes it accompanies. Melatonin is shown to be able to modulate many signaling pathways involved in many essential cell functions, which if deregulated cause an accelerated pace towards cancer. More so, melatonin is involved in the regulation of immune function, tumor microenvironment, and acts as an antioxidant agent. Many studies have focused on the beneficial effects of melatonin in colorectal cancers, such as induction of apoptosis, increased sensitivity to chemotherapy agents and radiotherapy, limiting cellular proliferation, migration, and invasion. The present review aims to illustrate the known significance of melatonin in colorectal cancer and to address possible clinical use.

Melatonin Prevents Oxidative Stress-Induced Mitochondrial Dysfunction and Apoptosis in High Glucose-Treated Schwann Cells via Upregulation of Bcl2, NF-κB, mTOR, Wnt Signalling Pathways

Neuropathy is a complication that affects more than 50% of long-standing diabetic patients. One of the causes of diabetes neuropathy (DN) is the apoptosis of Schwann cells due to prolonged exposure to high glucose and build-up of oxidative stress. Melatonin is a hormone that has a known antioxidant property. In this study, we investigated the protective effect of melatonin on high glucose-induced Schwann cells' apoptosis. Our results revealed that high glucose promoted apoptosis via mitochondrial-related oxidative stress and downregulated Bcl-2 family proteins in Schwann cells. In this signalling pathway, Bcl-2, Bcl-XL and Mcl-1 proteins were down-regulated while p-BAD and Puma proteins were up-regulated by high glucose treatment. Besides, we also proved that high glucose promoted apoptosis in Schwann cells through decreasing the p-NF-κB in the NF-κB signalling pathway. Key regulators of mTOR signalling pathway such as p-mTOR, Rictor and Raptor were also down-regulated after high glucose treatment. Additionally, high glucose treatment also decreased the Wnt signalling pathway downstream proteins (Wnt 5a/b, p-Lrp6 and Axin). Our results showed that melatonin treatment significantly inhibited high glucose-induced ROS generation, restored mitochondrial membrane potential and inhibited high glucose-induced apoptosis in Schwann cells. Furthermore, melatonin reversed the alterations of protein expression caused by high glucose treatment. Our results concluded that melatonin alleviates high glucose-induced apoptosis in Schwann cells through mitigating mitochondrial-related oxidative stress and the alterations of Bcl-2, NF-κB, mTOR and Wnt signalling pathways.

Melatonin: A new inhibitor agent for cervical cancer treatment

Cervical cancer is one of the most common cancers between women and is known as the third leading cause of female cancer related deaths annually. Its detection in early stages allows it to be a preventable and generally treatable disease. Increasing evidence revealed, a variety of internal and external factors are associated with initiation and progression of cervical cancer pathogenesis. Human papilloma virus infection is found as a major cause of cervical cancer. Other molecular and biochemical alterations as well as genetic and epigenetic changes are related cervical cancer progression. Current treatment options often have severe side effects and toxicities thus, new adjuvant agents having synergistic effects and ability to decrease different side effects and toxicities are needed. Melatonin is an indolamine compound secreted from the pineal gland which shows wide range anticancer activities. A large amount of studies indicated inhibitory effects of melatonin against various types of cancers. In addition, experimental evidence reports inhibitory effects of melatonin as an adjuvant therapy on cervical cancer by targeting a sequence of different molecular mechanisms. Herein, for first time, we summarized anticervical cancer effects of melatonin and its underlying molecular mechanisms.

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

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

Melatonin synergizes BRAF-targeting agent vemurafenib in melanoma treatment by inhibiting iNOS/hTERT signaling and cancer-stem cell traits

BACKGROUND

As the selective inhibitor of BRAF kinase, vemurafenib exhibits effective antitumor activities in patients with V600 BRAF mutant melanomas. However, acquired drug resistance invariably develops after its initial treatment.

METHODS

Immunohistochemical staining was performed to detect the expression of iNOS and hTERT, p-p65, Epcam, CD44, PCNA in mice with melanoma xenografts. The proliferation and migration of melanoma cells were detected by MTT, tumorsphere culture, cell cycle, cell apoptosis, AO/EB assay and colony formation, transwell assay and scratch assay in vitro, and tumor growth differences were observed in xenograft nude mice. Changes in the expression of key molecules in the iNOS/hTERT signaling pathways were detected by western blot. Nucleus-cytoplasm separation, and immunofluorescence analyses were conducted to explore the location of p50/p65 in melanoma cell lines. Flow cytometry assay were performed to determine the expression of CD44. Pull down assay and ChIP assay were performed to detect the binding ability of p65 at iNOS and hTERT promoters. Additionally, hTERT promoter-driven luciferase plasmids were transfected in to melanoma cells with indicated treatment to determine luciferase activity of hTERT.

RESULTS

Melatonin significantly and synergistically enhanced vemurafenib-mediated inhibitions of proliferation, colony formation, migration and invasion and promoted vemurafenib-induced apoptosis, cell cycle arresting and stemness weakening in melanoma cells. Further mechanism study revealed that melatonin enhanced the antitumor effect of vemurafenib by abrogating nucleus translocation of NF-κB p50/p65 and their binding at iNOS and hTERT promoters, thereby suppressing the expression of iNOS and hTERT. The elevated anti-tumor capacity of vemurafenib upon co-treatment with melatonin was also evaluated and confirmed in mice with melanoma xenografts.

CONCLUSIONS

Collectively, our results demonstrate melatonin synergizes the antitumor effect of vemurafenib in human melanoma by inhibiting cell proliferation and cancer-stem cell traits via targeting NF-κB/iNOS/hTERT signaling pathway, and suggest the potential of melatonin in antagonizing the toxicity of vemurafenib and augmenting its sensitivities in melanoma treatment.

Potential use of melatonin in skin cancer treatment: A review of current biological evidence

Skin cancer, particularly melanoma, is a leading cause of death worldwide. The therapeutic methods for this malignancy are not effective, and due to the side effects of these treatments, applying an appropriate alternative or complementary treatment is important. According to available data, melatonin as the main product of the pineal gland has oncostatic and antitumoral properties. Also, melatonin acts as an anti-inflammatory and reactive oxygen species inducer agent which suppresses the growth of tumors. It also has apoptosis induction characteristics through regulating signaling pathways, including heat shock protein 70, nuclear factor-erythroid 2 p45-related factor 2 and others. Thus, adding melatonin to chemo- and radiotherapy may have synergistic therapeutic effects and increase the survival time in patients with skin cancer. Few clinical studies have evaluated the efficacy of melatonin in skin cancer. Based on the related mechanisms, this review discusses about how melatonin may improve outcomes in skin cancer patients.

Therapeutic potential of melatonin related to its role as an autophagy regulator: A review

There are several pathologies, syndromes, and physiological processes in which autophagy is involved. This process of self-digestion that cells trigger as a survival mechanism is complex and tightly regulated, according to the homeostatic conditions of the organ. However, in all cases, its relationship with oxidative stress alterations is evident, following a pathway that suggests endoplasmic reticulum stress and/or mitochondrial changes. There is accumulating evidence of the beneficial role that melatonin has in the regulation and restoration of damaged autophagic processes. In this review, we focus on major physiological changes such as aging and essential pathologies including cancer, neurodegenerative diseases, viral infections and obesity, and document the essential role of melatonin in the regulation of autophagy in each of these different situations.

Melatonin May Increase Anticancer Potential of Pleiotropic Drugs

Melatonin (N-acetyl-5-methoxytryptamine) is not only a pineal hormone, but also an ubiquitary molecule present in plants and part of our diet. Numerous preclinical and some clinical reports pointed to its multiple beneficial effects including oncostatic properties, and as such, it has become one of the most aspiring goals in cancer prevention/therapy. A link between cancer and inflammation and/or metabolic disorders has been well established and the therapy of these conditions with so-called pleiotropic drugs, which include non-steroidal anti-inflammatory drugs, statins and peroral antidiabetics, modulates a cancer risk too. Adjuvant therapy with melatonin may improve the oncostatic potential of these drugs. Results from preclinical studies are limited though support this hypothesis, which, however, remains to be verified by further research.

Ecto-Calreticulin is essential for an efficient immunogenic cell death stimulation in mouse melanoma

Skin melanoma remains one of the most aggressive and difficult to treat human malignancy, with an increasing incidence every year. Although surgical resection represents the best therapeutic approach, this is only feasible in cases of early diagnosis. Furthermore, the established malignancy is resistant to all therapeutic strategies employed so far, resulting in an unacceptable patient survival rate. Although the immune-mediated therapeutic approaches, based on anti-PD1 or anti-CTLA4, are very promising and under clinical trial experimentation, they could conceal not yet fully emerged pitfalls such as the development of autoimmune diseases. Therefore, alternative therapeutic approaches are still under investigation, such as the immunogenic cell death (ICD) process. Here we show that the lack of calreticulin translocation onto mouse melanoma cell membrane prevents the stimulation of an effective ICD response in vivo.

Synergistic anti-oomycete effect of melatonin with a biofungicide against oomycetic black shank disease

Human health, food safety, and agriculture have been threatened by oomycetic diseases caused by notorious pathogenic oomycetes. Chemical oomyceticides are the main approaches in control of pathogenic oomycetes. However, the overused chemical oomyceticides have resulted in serious environmental pollution and drug resistance. The eco-friendly bio-oomyceticides are required for sustainable development through screening synergistic drug combinations. In this study, Phytophthora nicotianae (P. nicotianae), as one of the most destructive oomycetic diseases in agriculture, was used as a model system to screen the novel bio-oomyceticides based on drug combination. The results showed that treatment of melatonin or ethylicin (IUPAC Name: 1-ethylsulfonylsulfanylethane) alone displayed similar phenotypes such as the inhibition of the hyphal growth, reduction of the cell viability, and suppression of the virulence of P. nicotianae. Importantly, melatonin and ethylicin shared the same targets of interfering with the amino acid metabolism, overexpressing apoptosis-inducing factor, and dysregulating the virulence-related genes. Furthermore, strong synergism against P. nicotianae was induced by combining melatonin with ethylicin. Under treatment of the combination of melatonin and ethylicin, the expression of genes associated with amino acid, the apoptosis-inducing factor, and the virulence-related genes was much more significantly dysregulated than that of single drug treatment. Thus, the tobacco black shank caused by P. nicotianae can be successfully controlled using the combination of melatonin and ethylicin. These observations suggest that the synergistic effect based on the combination of melatonin and ethylicin is an eco-friendly alternative for the control of the destructive oomycetic diseases.

Melatonin for the prevention and treatment of cancer

The epidemiological studies have indicated a possible oncostatic property of melatonin on different types of tumors. Besides, experimental studies have documented that melatonin could exert growth inhibition on some human tumor cells in vitro and in animal models. The underlying mechanisms include antioxidant activity, modulation of melatonin receptors MT1 and MT2, stimulation of apoptosis, regulation of pro-survival signaling and tumor metabolism, inhibition on angiogenesis, metastasis, and induction of epigenetic alteration. Melatonin could also be utilized as adjuvant of cancer therapies, through reinforcing the therapeutic effects and reducing the side effects of chemotherapies or radiation. Melatonin could be an excellent candidate for the prevention and treatment of several cancers, such as breast cancer, prostate cancer, gastric cancer and colorectal cancer. This review summarized the anticancer efficacy of melatonin, based on the results of epidemiological,experimental and clinical studies, and special attention was paid to the mechanisms of action.

Effects of endoplasmic reticulum stress on autophagy and apoptosis of human leukemia cells via inhibition of the PI3K/AKT/mTOR signaling pathway

The present study aimed to explore the regulatory effects of endoplasmic reticulum stress (ERS) on the phosphoinositide 3‑kinase (PI3K)/AKT serine/threonine kinase 1 (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, and its subsequent effects on autophagy and apoptosis of human leukemia cells. Human leukemia cells were cultured and treated with various concentrations of tunicamycin for 0, 24, 48, 72 and 90 h. Subsequently, human leukemia cells were assigned into the ER activation group, which was treated with 100 ng/ml tunicamycin, the ER activation + TO901317 (PI3K inhibitor) group, and the control group. An MTT assay was conducted to detect cell proliferation. In addition, a monodansylcadaverine (MDC) assay was used to detect the formation of autophagosomes and Annexin V‑fluorescein isothiocyanate/propidium iodide double staining was used to examine cell apoptosis. Western blotting was performed to detect the expression levels of 78‑kDa glucose‑regulated protein (GRP78), phosphorylated (p)‑protein kinase R‑like endoplasmic reticulum kinase (PERK), p‑α subunit of eukaryotic initiation factor 2 (eIF2α), microtubule‑associated protein 1A/1B‑light chain 3 (LC3), caspase‑3, CCAAT‑enhancer‑binding protein homologous protein (CHOP), PI3K, AKT and mTOR. Treatment with 100 ng/ml tunicamycin for 72 h was considered the optimal condition for further experiments. Compared with in cells prior to treatment, human leukemia cells treated with tunicamycin exhibited increased expression of p‑PERK, p‑eIF2α and GRP78 after 72 h (P<0.05). In addition, the expression levels of mTOR, AKT and PI3K were decreased in the ER activation group compared with in the control and ER activation + TO901317 groups (P<0.05). Compared with in the control group, cell proliferation was inhibited and MDC fluorescence intensity was increased in the ER activation group (P<0.05). Furthermore, compared with in the control and ER activation + TO901317 groups, western blotting indicated that the expression levels of LC3‑II were increased in the ER activation group (P<0.05). The apoptotic rate was also higher in the ER activation group compared with in the control group (P<0.05), and caspase‑3 and CHOP expression was elevated in the ER activation group (P<0.05). These findings indicated that ERS may induce autophagy and apoptosis of human leukemia cells via inhibiting the PI3K/AKT/mTOR signaling pathway.

Melatonin and Cancer Hallmarks

Melatonin is a natural indoleamine produced by the pineal gland that has many functions, including regulation of the circadian rhythm. Many studies have reported the anticancer effect of melatonin against a myriad of cancer types. Cancer hallmarks include sustained proliferation, evading growth suppressors, metastasis, replicative immortality, angiogenesis, resisting cell death, altered cellular energetics, and immune evasion. Melatonin anticancer activity is mediated by interfering with various cancer hallmarks. This review summarizes the anticancer role of melatonin in each cancer hallmark. The studies discussed in this review should serve as a solid foundation for researchers and physicians to support basic and clinical studies on melatonin as a promising anticancer agent.

Activation of endoplasmic reticulum stress promotes autophagy and apoptosis and reverses chemoresistance of human small cell lung cancer cells by inhibiting the PI3K/AKT/mTOR signaling pathway

OBJECTIVE

This study aims to investigate the effects of endoplasmic reticulum stress (ERS) on autophagy, apoptosis and chemoresistance of human small cell lung cancer (SCLC) cells via the PI3K/AKT/mTOR signaling pathway.

RESULTS

The expressions of ERS-related proteins (PEAK, eIF2α and CHOP) up-regulated, autophagy-related proteins (LC3, LC3-II and Beclin1) and apoptosis-related proteins (Bax and procaspase-3) down-regulated in NCI-H446 and H69 cells after tunicamycin treatment for 24 h. Compared with the blank group, the tunicamycin, BEZ235 and tunicamycin + BEZ235 groups exhibited decreased expressions of p-PI3K, p-AKT and p-mTOR, and increased expressions of autophagy-related proteins (LC3, LC3-II and Beclin1) and apoptosis proteins (Bax and procaspase-3), and the most obvious changes were observed in the tunicamycin + BEZ235 group.

MATERIALS AND METHODS

CCK-8 assay was applied to select the best cell line from five SCLC cell lines (NCI-H446, H69, H526, H146 and H209). Finally, NCI-H446 and H69 cells were selected for further experiments. NCI-H446/CDDP and H69/CDDP were selected and divided into the blank group, tunicamycin (an ESR inducer) group, BEZ235 (inhibitors of PI3K/AKT/mTOR pathway) group and tunicamycin + BEZ235 group. Cell apoptosis was detected by flow cytometry. Autophagy was observed by fluorescence microscopy and flow cytometry. Western blotting was used to detect the expressions of ERS-related proteins, autophagy-related proteins, apoptosis-related proteins and PI3K/AKT/mTOR pathway-related proteins.

CONCLUSIONS

Our findings provide evidence that the activation of ERS could promote autophagy and apoptosis and reverse chemoresistance of human SCLC cells by inhibiting the PI3K/AKT/mTOR pathway.

Down-regulation of CHERP inhibits neuroblastoma cell proliferation and induces apoptosis through ER stress induction

Neuroblastoma is a childhood tumor that is derived from the sympathetic nervous system. In recent years, great progress has been made in our understanding of neuroblastoma. However, applying theories to improve disease outcomes remains challenging. In this study, we observed that calcium homeostasis endoplasmic reticulum protein (CHERP) was involved in the maintenance of neuroblastoma cell proliferation and tumorigenicity. Moreover, elevated CHERP expression was positively correlated with poor patient survival, whereas low CHERP expression was predictive of better outcomes. Additional functional studies showed that CHERP knockdown inhibited neuroblastoma cell proliferation in vitro and resulted in defective tumorigenicity in vivo. Moreover, CHERP depletion suppressed neuroblastoma cell proliferation by inducing endoplasmic reticulum stress and cell apoptosis. Considering the functional roles of CHERP in neuroblastoma development and maintenance, CHERP might function as a novel therapeutic target for neuroblastoma patients.

Melatonin and Hippo Pathway: Is There Existing Cross-Talk?

Melatonin is an indolic hormone that regulates a plethora of functions ranging from the regulation of circadian rhythms and antioxidant properties to the induction and maintenance of tumor suppressor pathways. It binds to specific receptors as well as to some cytosolic proteins, leading to several cellular signaling cascades. Recently, the involvement of melatonin in cancer insurgence and progression has clearly been demonstrated. In this review, we will first describe the structure and functions of melatonin and its receptors, and then discuss both molecular and epidemiological evidence on melatonin anticancer effects. Finally, we will shed light on potential cross-talk between melatonin signaling and the Hippo signaling pathway, along with the possible implications for cancer therapy.

Antiproliferative and pro-apoptotic activity of melatonin analogues on melanoma and breast cancer cells

Melatonin plays different physiological functions ranging from the regulation of circadian rhythms to tumor inhibition, owing to its antioxidant, immunomodulatory and anti-aging properties. Due to its pleiotropic functions, melatonin has been shown to elicit cytoprotective processes in normal cells and trigger pro-apoptotic signals in cancer cells. The therapeutic potential of melatonin analogues prompted us to investigate the in vitro and in vivo antitumor activity of new melatonin derivatives and explore the underlying molecular mechanisms. The experiments revealed that the new melatonin analogues inhibited the growth of melanoma and breast cancer cells in a dose- and time-dependent manner. In addition, our results indicated that melatonin derivative UCM 1037 could induce apoptosis in melanoma and breast cancer cells, as well as cell necrosis, in MCF-7. Together, apoptosis and necrosis could be two possible mechanisms to explain the cytotoxic effect of the melatonin analogue against cancer cells. The suppression of tumor growth by the melatonin analogues was further demonstrated in vivo in a xenograft mice model. A decrease in the activation of MAPK pathway was observed in all cancer cells following UCM 1037 treatment. Overall, this study describes a promising antitumor compound showing antiproliferative and cytotoxic activity in melanoma and breast cancer cells.

Effects of endoplasmic reticulum stress on the autophagy, apoptosis, and chemotherapy resistance of human breast cancer cells by regulating the PI3K/AKT/mTOR signaling pathway

Nowadays, although chemotherapy is an established therapy for breast cancer, the molecular mechanisms of chemotherapy resistance in breast cancer remain poorly understood. This study aims to explore the effects of endoplasmic reticulum stress on autophagy, apoptosis, and chemotherapy resistance in human breast cancer cells by regulating PI3K/AKT/mTOR signaling pathway. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to detect the cell viability of six human breast cancer cell lines (MCF-7, ZR-75-30, T47D, MDA-MB-435s, MDA-MB-453, and MDA-MB-231) treated with tunicamycin (5 µM), after which MCF-7 cells were selected for further experiment. Then, MCF-7 cells were divided into the control (without any treatment), tunicamycin (8 µ), BEZ235 (5 µ), and tunicamycin + BEZ235 groups. Cell viability of each group was testified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Western blotting was applied to determine the expressions of endoplasmic reticulum stress and PI3K/AKT/mTOR pathway-related proteins and autophagy- and apoptosis-related proteins. Monodansylcadaverine and Annexin V-fluorescein isothiocyanate/propidium iodide staining were used for determination of cell autophagy and apoptosis. Furthermore, MCF-7 cells were divided into the control (without any treatment), tunicamycin (5 µM), cisplatin (16 µM), cisplatin (16 µM) + BEZ235 (5 µM), tunicamycin (5 µM) + cisplatin (16 µM), and tunicamycin (5 µM) + cisplatin (16 µM) + BEZ235 groups. Cell viability and apoptosis were also evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Annexin V-fluorescein isothiocyanate/propidium iodide staining. In MCF-7 cells treated with tunicamycin, cell viability decreased significantly, but PEAK, eIF2, and CHOP were upregulated markedly and p-PI3K, p-AKT, and p-MTOR were downregulated in dose- and time-dependent manners. In the tunicamycin + BEZ235 group, the cell viability was lower and the apoptosis rate was higher than those of the control and monotherapy groups. Compared with the cisplatin group, the tunicamycin + cisplatin group showed a relatively higher growth inhibition rate; the growth inhibition rate substantially increased in the tunicamycin + cisplatin + BEZ235 group than the tunicamycin + cisplatin group. The apoptosis rate was highest in tunicamycin + cisplatin + BEZ235 group, followed by tunicamycin + cisplatin group and then cisplatin group. Our study provide evidence that endoplasmic reticulum stress activated by tunicamycin could promote breast cancer cell autophagy and apoptosis and enhance chemosensitivity of MCF-7 cells by inhibiting the PI3K/AKT/mTOR signaling pathway.

Snapshot: implications for melatonin in endoplasmic reticulum homeostasis

The endoplasmic reticulum (ER) is an important intracellular membranous organelle. Previous studies have demonstrated that the ER is responsible for protein folding and trafficking, lipid synthesis and the maintenance of calcium homeostasis. Interestingly, the morphology and structure of the ER were recently found to be important. Melatonin is a hormone that anticipates the daily onset of darkness in mammals, and it is well known that melatonin acts as an antioxidant by scavenging free radicals and increasing the activity of antioxidant enzymes in the body. Notably, the existing evidence demonstrates that melatonin is involved in ER homeostasis, particularly in the morphology of the ER, indicating a potential protective role of melatonin. This review discusses the existing knowledge regarding the implications for the involvement of melatonin in ER homeostasis.

Melatonin set out to ER stress signaling thwarts epithelial mesenchymal transition and peritoneal dissemination via calpain-mediated C/EBPβ and NFκB cleavage

Peritoneal dissemination of tumor has high mortality and is associated with the loss of epithelial features, acquisition of motile mesenchymal morphology characteristics, and invasive properties by tumor cells. Melatonin is an endogenously produced molecule in all plant species that is known to exert antitumor activity, but to date, its underlying mechanisms and antiperitoneal metastasis efficacy is not well defined. This study determined the antiperitoneal dissemination potential of melatonin in vivo and assessed its association with the inhibition of epithelial-to-mesenchymal transition (EMT) signaling mechanism by endoplasmic reticulum (ER) stress, which may be a major molecular mechanism of melatonin against cancer. The results demonstrate that melatonin inhibited peritoneal metastasis in vivo and activated ER stress in Cignal ERSE Reporter Assay, organelle structure in transmission electron microscopy images, calpain activity, and protein biomarkers like p-elf2α. Moreover, the overexpression of transcription factor C/EBPβ in gastric cancer interacted with NFκB and further regulates COX-2 expression. These were dissociated and downregulated by melatonin, as proven by immunofluorescence imaging, immunoprecipitation, EMSA, and ChIP assay. Melatonin or gene silencing of C/EBPβ decreased the EMT protein markers (E-cadherin, Snail, and Slug) and Wnt/beta-catenin activity by Topflash activity, and increased ER stress markers. In an animal study, the results of melatonin therapy were consistent with those of in vitro findings and attenuated systemic proangiogenesis factor production. In conclusion, C/EBPβ and NFκB inhibition by melatonin may impede both gastric tumor growth and peritoneal dissemination by inducing ER stress and inhibiting EMT.

Endoplasmic reticulum stress-mediated pathways to both apoptosis and autophagy: Significance for melanoma treatment

Melanoma is the most aggressive form of skin cancer. Disrupted intracellular signaling pathways are responsible for melanoma's extraordinary resistance to current chemotherapeutic modalities. The pathophysiologic basis for resistance to both chemo- and radiation therapy is rooted in altered genetic and epigenetic mechanisms that, in turn, result in the impairing of cell death machinery and/or excessive activation of cell growth and survival-dependent pathways. Although most current melanoma therapies target mitochondrial dysregulation, there is increasing evidence that endoplasmic reticulum (ER) stress-associated pathways play a role in the potentiation, initiation and maintenance of cell death machinery and autophagy. This review focuses on the reliability of ER-associated pathways as therapeutic targets for melanoma treatment.