Melatonin enhances arsenic trioxide-induced cell death via sustained upregulation of Redd1 expression in breast cancer cells

The stress-responsive protein REDD1 and its pathophysiological functions

Regulated in development and DNA damage-response 1 (REDD1) is a stress-induced protein that controls various cellular functions, including metabolism, oxidative stress, autophagy, and cell fate, and contributes to the pathogenesis of metabolic and inflammatory disorders, neurodegeneration, and cancer. REDD1 usually exerts deleterious effects, including tumorigenesis, metabolic inflammation, neurodegeneration, and muscle dystrophy; however, it also exhibits protective functions by regulating multiple intrinsic cell activities through either an mTORC1-dependent or -independent mechanism. REDD1 typically regulates mTORC1 signaling, NF-κB activation, and cellular pro-oxidant or antioxidant activity by interacting with 14-3-3 proteins, IκBα, and thioredoxin-interacting protein or 75 kDa glucose-regulated protein, respectively. The diverse functions of REDD1 depend on cell type, cellular context, interaction partners, and cellular localization (e.g., mitochondria, endomembrane, or cytosol). Therefore, comprehensively understanding the molecular mechanisms and biological roles of REDD1 under pathophysiological conditions is of utmost importance. In this review, based on the published literature, we highlight and discuss the molecular mechanisms underlying the REDD1 expression and its actions, biological functions, and pathophysiological roles.

Honey: A Promising Therapeutic Supplement for the Prevention and Management of Osteoporosis and Breast Cancer

Osteoporosis and breast cancer are serious diseases that have become a significant socioeconomic burden. There are biochemical associations between the two disorders in terms of the amended function of estrogen, receptor activator of nuclear factor kappa beta ligand, oxidative stress, inflammation, and lipid accumulation. Honey as a functional food with high antioxidant and anti-inflammatory properties can contribute to the prevention of various diseases. Its health benefits are mainly related to the content of polyphenols. This review aims to summarize the current knowledge from in vitro, animal, and human studies on the use of honey as a potential therapeutic agent for osteoporosis and breast cancer. Preclinical studies have revealed a beneficial impact of honey on both bone health (microstructure, strength, oxidative stress) and breast tissue health (breast cancer cell proliferation and apoptosis, tumor growth rate, and volume). The limited number of clinical trials, especially in osteoporosis, indicates the need for further research to evaluate the potential benefits of honey in the treatment. Clinical studies related to breast cancer have revealed that honey is effective in increasing blood cell counts, interleukin-3 levels, and quality of life. In summary, honey may serve as a prospective therapeutic supplement for bone and breast tissue health.

Antitumor effect of melatonin on breast cancer in experimental models: A systematic review

Breast cancer is the most frequent malignant neoplasm in females. While conventional treatments such as chemotherapy and radiotherapy are available, they are highly invasive and toxic to oncological patients. Melatonin is a promising molecule for the treatment of breast cancer with antitumor effects on tumorigenesis and tumor progression. The aim of this systematic review was to synthesize knowledge about the antitumor effect of melatonin on breast cancer in experimental models and propose the main mechanisms of action already described in relation to the processes regulated by melatonin. PubMed, Web of Science, and Embase databases were used. The inclusion criteria were in vitro and in vivo experimental studies that used different formulations of melatonin as a treatment for breast cancer, without year or language restrictions. Risk of bias for studies was assessed using the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) tool. Data from selected articles were presented as narrative descriptions and tables. Seventy-five articles on different breast cancer cell lines and experimental models treated with melatonin alone, or in combination with other compounds were included. Melatonin showed antitumor effects on proliferative pathways related to the cell cycle and tumorigenesis, tumor death, angiogenesis, and tumor metastasis, as well as on oxidative stress and immune regulatory pathways. These effects were either dependent or independent of melatonin receptors. Herein, we clarify the antitumor action of melatonin on different tumorigenic processes in breast cancer in experimental models. Systematic review registration: PROSPERO database (CRD42022309822/https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022309822).

Breast Cancer and Arsenic Anticancer Effects: Systematic Review of the Experimental Data from In Vitro Studies

Arsenic is a known environmental carcinogenic agent. However, under certain circumstances, it may exert anticancer effects. In this systematic review, we aim to provide information on recent developments in studies on arsenic antitumor effects in breast cancer. Research included in the review refers to experimental data from in vitro studies. The data was collected using search terms "breast cancer," "arsenic," and "anticancer" (25.05.2021). Only studies in English and published in the last 10 years were included. The search identified 123 studies from the EBSCOhost, PubMed, and Scopus databases. In the selection process, thirty full-texts were evaluated as eligible for the review. The literature of the last decade provides a lot of information on mechanisms behind anticancer effects of arsenic on breast cancer. Similar to arsenic-induced carcinogenesis, these mechanisms include the activation of the redox system and the increased production of free radicals. Targets of arsenic action are systems of cell membranes, mitochondria, pathways of intracellular transmission, and the genetic apparatus of the cell. Beneficial effects of arsenic use are possible due to significant metabolic differences between cancer and healthy cells. Further efforts are needed in order to establish modes and doses of treatment with arsenic that would provide anticancer activity with minimal toxicity.

Nutritional Sensor REDD1 in Cancer and Inflammation: Friend or Foe?

Regulated in Development and DNA Damage Response 1 (REDD1)/DNA Damage-Induced Transcript 4 (DDIT4) is an immediate early response gene activated by different stress conditions, including growth factor depletion, hypoxia, DNA damage, and stress hormones, i.e., glucocorticoids. The most known functions of REDD1 are the inhibition of proliferative signaling and the regulation of metabolism via the repression of the central regulator of these processes, the mammalian target of rapamycin (mTOR). The involvement of REDD1 in cell growth, apoptosis, metabolism, and oxidative stress implies its role in various pathological conditions, including cancer and inflammatory diseases. Recently, REDD1 was identified as one of the central genes mechanistically involved in undesirable atrophic effects induced by chronic topical and systemic glucocorticoids widely used for the treatment of blood cancer and inflammatory diseases. In this review, we discuss the role of REDD1 in the regulation of cell signaling and processes in normal and cancer cells, its involvement in the pathogenesis of different diseases, and the approach to safer glucocorticoid receptor (GR)-targeted therapies via a combination of glucocorticoids and REDD1 inhibitors to decrease the adverse atrophogenic effects of these steroids.

Understanding the Mechanism of Action of Melatonin, Which Induces ROS Production in Cancer Cells

Reactive oxygen species (ROS) constitute a group of highly reactive molecules that have evolved as regulators of important signaling pathways. In this context, tumor cells have an altered redox balance compared to normal cells, which can be targeted as an antitumoral therapy by ROS levels and by decreasing the capacity of the antioxidant system, leading to programmed cell death. Melatonin is of particular importance in the development of innovative cancer treatments due to its oncostatic impact and lack of adverse effects. Despite being widely recognized as a pro-oxidant molecule in tumor cells, the mechanism of action of melatonin remains unclear, which has hindered its use in clinical treatments. The current review aims to describe and clarify the proposed mechanism of action of melatonin inducing ROS production in cancer cells in order to propose future anti-neoplastic clinical applications.

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.

Targeting Cell Death Mechanism Specifically in Triple Negative Breast Cancer Cell Lines

Triple negative breast cancer (TNBC) is currently associated with a lack of treatment options. Arsenic derivatives have shown antitumoral activity both in vitro and in vivo; however, their mode of action is not completely understood. In this work we evaluate the response to arsenate of the double positive MCF-7 breast cancer cell line as well as of two different TNBC cell lines, Hs578T and MDA-MB-231. Multimodal experiments were conducted to this end, using functional assays and microarrays. Arsenate was found to induce cytoskeletal alteration, autophagy and apoptosis in TNBC cells, and moderate effects in MCF-7 cells. Gene expression analysis showed that the TNBC cell lines’ response to arsenate was more prominent in the G2M checkpoint, autophagy and apoptosis compared to the Human Mammary Epithelial Cells (HMEC) and MCF-7 cell lines. We confirmed the downregulation of anti-apoptotic genes (MCL1, BCL2, TGFβ1 and CCND1) by qRT-PCR, and on the protein level, for TGFβ2, by ELISA. Insight into the mode of action of arsenate in TNBC cell lines it is provided, and we concluded that TNBC and non-TNBC cell lines reacted differently to arsenate treatment in this particular experimental setup. We suggest the future research of arsenate as a treatment strategy against TNBC.

Effect of astaxanthin and melatonin on cell viability and DNA damage in human breast cancer cell lines

BACKGROUND

Astaxanthin is a xanthophyll pigment found in algae and marine animals, having strong anti-oxidative, anti-tumoral, and anti-inflammatory effects. Additionally, melatonin has shown inhibitory effects on the growth of human breast cancer cells. The aim of the present study was to evaluate the effect of astaxanthin and the combined effects of astaxanthin and melatonin on breast cancer cells and the non-tumoral breast cell line.

MATERIALS AND METHODS

The human breast cancer cell lines, T47D and MDA-MB-231, and non-tumorigenic cell line MCF 10A were treated and compared to astaxanthin, melatonin, and co-administration of these two compounds. Cell viability, apoptosis induction, Bcl-2 protein expression, and DNA damage were measured by MTT assay, acridine orange/ethidium bromide (AO/EB) staining, immunocytochemistry, and comet assay.

RESULTS

Astaxanthin at lower doses than melatonin reduced cell viability and Bcl2 expression, induced apoptosis and DNA damage in MDA-MB-231 and T47D. Meanwhile, the effects of astaxanthin on cell cytotoxicity, apoptosis, and DNA damage in MCF10A cells are insignificant compared to MDA-MB-231 and T47D. Moreover, the results indicated that astaxanthin in T47D cells caused more cell death compared to MDA-MB-231 cells. Astaxanthin induced cell death on breast cancer cells and without cell cytotoxicity for non-cancerous cells.

CONCLUSION

Furthermore, the presence of astaxanthin increased the function of melatonin-induced cell death in breast cancer cells.

Based on Activation of p62-Keap1-Nrf2 Pathway, Hesperidin Protects Arsenic-Trioxide-Induced Cardiotoxicity in Mice

Background: Hesperidin (HES) is a flavonoid glycoside found in the tangerine peel and has antioxidant properties. Arsenic trioxide (ATO) is an anti-tumour drug; however, its serious cardiotoxicity limits its clinical application. In addition, the protection of HES against ATO-induced cardiotoxicity has not been explored.

Objective: The study aims to investigate and identify the underlying effect and mechanism of HES on ATO-induced cardiotoxicity.

Methods: Fifty mice were randomly assigned to five groups. Mice were orally given HES:100 or 300 mg/kg/day concurrently and given ATO intraperitoneal injections: 7.5 mg/kg/day for 1 week. Blood and heart tissues were collected for examination. Evaluated in serum was the levels of creatine kinase (CK), lactate dehydrogenase (LDH) and cardiac troponin I (cTnI). In addition, evaluated in heart tissues were the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), catalase (CAT), tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), Caspase-3, cleaved-Caspase-3, p62, Kelch-like ECH-associated protein 1 (Keap1), and nuclear factor erythroid 2-related factor 2 (Nrf2). The heart tissues were also examined for histopathology and mitochondrial ultrastructure.

Results: Compared with the ATO group, the HES treatment groups reduced the levels of CK, LDH, cTnI, ROS, MDA, TNF-α, IL-6, Bax, Caspase-3, cleaved-Caspase-3 and Keap1 and enhanced the levels of SOD, GSH, CAT, Bcl-2, p62 and Nrf2.

Conclusions: The results demonstrate that HES protects against ATO-induced cardiotoxicity, through inhibiting oxidative stress, and subsequent inflammation and apoptosis. The underlying results are closely related to the regulation of the p62-Keap1-Nrf2 signalling pathway.

Empowering Melatonin Therapeutics with Drosophila Models

Melatonin functions as a central regulator of cell and organismal function as well as a neurohormone involved in several processes, e.g., the regulation of the circadian rhythm, sleep, aging, oxidative response, and more. As such, it holds immense pharmacological potential. Receptor-mediated melatonin function mainly occurs through MT1 and MT2, conserved amongst mammals. Other melatonin-binding proteins exist. Non-receptor-mediated activities involve regulating the mitochondrial function and antioxidant cascade, which are frequently affected by normal aging as well as disease. Several pathologies display diseased or dysfunctional mitochondria, suggesting melatonin may be used therapeutically. Drosophila models have extensively been employed to study disease pathogenesis and discover new drugs. Here, we review the multiple functions of melatonin through the lens of functional conservation and model organism research to empower potential melatonin therapeutics to treat neurodegenerative and renal diseases.

Melatonin: a pleiotropic hormone as a novel potent therapeutic candidate in arsenic toxicity

BACKGROUND

Arsenic is a natural element which exists in the environment in inorganic and organic forms. In humans, the main reason for the toxicity of arsenic is its uptake via water sources. As polluted water and the problems associated with it can be found in many countries. Therefore, considering all these positive effects of melatonin, this review is aimed at melatonin supplementation therapy on arsenic toxicity which seems to be a suitable therapeutic agent to eliminate the adverse effects of arsenic.

METHODS AND RESULTS

It is seen in previous studies that chronic exposure to arsenic could cause serious dys functions of organs and induce different degrees of toxicities that is one of the first hazardous materials in the classification of substances by the United States Environmental Protection Agency so leads to costly cleanup operations burdening the economy. Arsenic harmfulness degree depends on the bioavailability, chemical form, valence state, detoxification, and metabolism of human body. The oxidative stress has a major role in arsenic-induced toxicity; on the other hand, it was discovered that melatonin is a powerful scavenger for free radical and it's an extensive-spectrum antioxidant.

CONCLUSION

Due to its highly lipophilic and small size properties, melatonin accesses all intracellular organs by easily passing via the cell membrane and prevents protein, DNA damage, and lipid peroxidation. In particular, melatonin, by protecting and reducing oxidative stress in mitochondria, can normalize homeostasis and mitochondrial function and ultimately prevent apoptosis and cell death.

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.

siRNA Knockdown of REDD1 Facilitates Aspirin-Mediated Dephosphorylation of mTORC1 Target 4E-BP1 in MDA-MB-468 Human Breast Cancer Cell Line

Background

Mutations within genes encoding components of the PI3K/AKT/mTOR (phosphoinositide 3-kinase/protein kinase B/mechanistic target of rapamycin) signaling axis frequently activate the pathway in breast cancer, making it an attractive therapeutic target. Inhibition of mTORC1 (mechanistic target of rapamycin complex 1) activity upon aspirin treatment has been reported in breast cancer cells harboring PI3KCA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) mutation and is considered to account for anticancer action.

Methods

MDA-MB-468 (harbors mutated PTEN (phosphatase and TENsin homolog)), MCF-7 (PI3KCA-mutated), MDA-MB-231 (no PI3K pathway mutations) cancer cell lines and MCF10A non-cancerous breast epithelial cells were employed for the assessment of modulation of mTORC1 signaling by aspirin. Targeted amplicon-based next-generation sequencing using the Ion Torrent technology was carried out to determine gene expression changes following drug treatment. Western blot was performed to analyze the expression and phosphorylation of proteins. Knockdown by siRNA approach was applied to assess the role of REDD1/DDIT4 (DNA damage-inducible transcript 4) in mTORC1 inhibition by aspirin.

Results

We show a decline in phosphorylation of mTORC1 downstream substrate 4E-BP1 (eukaryotic translation initiation factor 4E-binding protein 1) in response to treatment with aspirin and its metabolite salicylic acid in MDA-MB-468, MCF-7, MDA-MB-231, and MCF10A cell lines. We further demonstrate a novel molecular response to aspirin in breast cancer cells. Specifically, we found that aspirin and salicylic acid increase the expression of REDD1 protein, that is known for its suppressive function towards mTORC1. Unexpectedly, we observed that siRNA knockdown of REDD1 expression facilitated aspirin-mediated suppression of mTORC1 downstream substrate 4E-BP1 phosphorylation in the MDA-MB-468 cell line. REDD1 downregulation slightly encouraged reduction in 4E-BP1 phosphorylation by aspirin in MCF-7 cells but did not elicit a reproducible effect in the MDA-MB-231 cell line. siRNA knockdown of REDD1 did not affect the expression of phosphorylated form of 4E-BP1 following aspirin treatment in MCF10A non-cancerous breast epithelial cells.

Conclusion

The current findings suggest that REDD1 downregulation might improve the anticancer activity of aspirin in a subset of breast tumors.

A review of the mechanism of DDIT4 serve as a mitochondrial related protein in tumor regulation

DDIT4 is a mitochondrial and tumor-related protein involved in anti-tumor therapy resistance, proliferation, and invasion, etc. Its expression level increases under the stress such as chemotherapy, hypoxia, and DNA damage. A number of clinical studies have confirmed that DDIT4 can change the behavior of tumor cells and the prognosis of patients with cancer. However, the role of DDIT4 in promoting or suppressing cancer is still inconclusive. This article summarized the four characteristics of DDIT4 including a mitochondria-related protein, interactions with various protein molecules, immune and metabolic cell related proteins and participator in the oxygen sensing pathway, which may be related to the progress of cancer.

A Brief Overview of the Paradoxical Role of Glucocorticoids in Breast Cancer

Glucocorticoids (GCs) are stress hormones that play multiple roles in the regulation of cancer cell differentiation, apoptosis, and proliferation. Some types of cancers, such as hematological malignancies, can be effectively treated by GCs, whereas the responses of epithelial cancers to GC treatment vary, even within cancer subtypes. In particular, GCs are frequently used as supporting treatment of breast cancer (BC) to protect against chemotherapy side effects. In the therapy of nonaggressive luminal subtypes of BC, GCs can have auxiliary antitumor effects due to their cytotoxic actions on cancer cells. However, GCs can promote BC progression, colonization of distant metastatic sites, and metastasis. The effects of GCs on cell proliferation vary with BC subtype and its molecular profile and are realized via the activation of glucocorticoid receptor (GR), a well-known transcriptional factor involved in the regulation of the expression of multiple genes, cell-cell adhesion, and cell migration and polarity. This review focuses on the roles of GC signaling in the adhesion, migration, and metastasis of BC cells. We discuss the molecular mechanisms of GC actions that lead to BC metastasis and propose alternative pharmacological uses of GCs for BC treatment.

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.

Realgar Nanoparticles Inhibit Migration, Invasion and Metastasis in a Mouse Model of Breast Cancer by Suppressing Matrix Metalloproteinases and Angiogenesis

BACKGROUND

Realgar, a traditional Chinese medicine, has shown antitumor efficacy in several tumor types. We previously showed that realgar nanoparticles (nano-realgar) had significant antileukemia, anti-lung cancer and anti-liver cancer effects. In addition, the anti-tumor effects of nanorealgar were significantly better than those of ordinary realgar.

OBJECTIVE

To explore the inhibitory effects and molecular mechanisms of nano-realgar on the migration, invasion and metastasis of mouse breast cancer cells.

METHODS

Wound-healing migration assays and Transwell invasion assays were carried out to determine the effects of nano-realgar on breast cancer cell (4T1) migration and invasion. The expression levels of matrix metalloproteinase (MMP)-2 and -9 were measured by Western blot. A murine breast cancer metastasis model was established, administered nano-realgar for 32 days and monitored for tumor growth and metastasis by an in vivo optical imaging system. Finally, living imaging and hematoxylin and eosin (HE) staining were used to measure the morphology and pathology of lung and liver cancer cell metastases, respectively. Angiogenesis was assessed by CD34 immunohistochemistry.

RESULTS

Nano-realgar significantly inhibited the migration and invasion of breast cancer 4T1 cells and the expression of MMP-2 and -9. Meanwhile, nano-realgar effectively suppressed the abilities of tumor growth, metastasis and angiogenesis in the murine breast cancer metastasis model in a time- and dosedependent manner.

CONCLUSION

Nano-realgar significantly inhibited migration and invasion of mouse breast cancer cells in vitro as well as pulmonary and hepatic metastasis in vivo, which may be closely correlated with the downexpression of MMP-2 and -9 and suppression of tumor neovascularization.

Melatonin: A Potential Therapeutic Option for Breast Cancer

Melatonin has significant inhibitory effects in numerous cancers, especially breast cancer. In estrogen receptor (ER)-positive human breast cancer, the oncostatic actions of melatonin are mainly achieved by suppressing ER mRNA expression and ER transcriptional activity via the MT1 receptor. Melatonin also regulates the transactivation of nuclear receptors, estrogen-metabolizing enzymes, and the expression of related genes. Furthermore, melatonin suppresses tumor aerobic glycolysis, critical cell-signaling pathways relevant to cell proliferation, survival, metastasis, and overcomes drug resistance. Studies in animal and human models indicate that disruption of the circadian nocturnal melatonin signal promotes the growth, metabolism, and signaling of human breast cancer, resulting in resistance to hormone therapy and chemotherapy, which may be reversed by melatonin.

The potential therapeutic effects of melatonin on breast cancer: An invasion and metastasis inhibitor

Breast cancer is the most common cancer among women and its metastasis which generally observed at the last stage is the major cause of breast cancer-related death. Therefore, the agents that have the potential to prevent metastatic and invasive nature of breast cancer can open up new therapeutic strategies. Melatonin, a major hormone of pineal gland, is a powerful anti-cancer agent. There are growing evidence regarding the protective effect of melatonin against cancer invasion and metastasis. The anti-metastatic feature of melatonin accompanies with suppression of tumor proliferation, induction of tumor apoptosis, regulation of the cell cycle, modulating angiogenesis, impediment of invasion, and induction of cancer cells sensitivity to the chemotherapy agents. More recently, anti-metastatic effect of melatonin through affecting cancer stem cells and vascular mimicry has been identified. Thus, the aim of this review is to discuss the potential therapeutic effect of melatonin on breast cancer via modulating the cells invasion and metastasis.

A Systematic Review of the Various Effect of Arsenic on Glutathione Synthesis In Vitro and In Vivo

Background

Arsenic is a toxic metalloid widely present in nature, and arsenic poisoning in drinking water is a serious global public problem. Glutathione is an important reducing agent that inhibits arsenic-induced oxidative stress and participates in arsenic methylation metabolism. Therefore, glutathione plays an important role in regulating arsenic toxicity. In recent years, a large number of studies have shown that arsenic can regulate glutathione synthesis in many ways, but there are many contradictions in the research results. At present, the mechanism of the effect of arsenic on glutathione synthesis has not been elucidated.

Objective

We will conduct a meta-analysis to illustrate the effects of arsenic on GSH synthesis precursors Glu, Cys, Gly, and rate-limiting enzyme γ-GCS in mammalian models, as well as the regulation of p38/Nrf2 of γ-GCS subunit GCLC, and further explore the molecular mechanism of arsenic affecting glutathione synthesis.

Results

This meta-analysis included 30 studies in vivo and 58 studies in vitro, among which in vivo studies showed that arsenic exposure could reduce the contents of GSH (SMD = -2.86, 95% CI (-4.45, -1.27)), Glu (SMD = -1.11, 95% CI (-2.20,-0.02)), and Cys (SMD = -1.48, 95% CI (-2.63, -0.33)), with no statistically significant difference in p38/Nrf2, GCLC, and GCLM. In vitro studies showed that arsenic exposure increased intracellular GSH content (SMD = 1.87, 95% CI (0.18, 3.56)) and promoted the expression of p-p38 (SMD = 4.19, 95% CI (2.34, 6.05)), Nrf2 (SMD = 4.60, 95% CI (2.34, 6.86)), and GCLC (SMD = 1.32, 95% CI (0.23, 2.41)); the p38 inhibitor inhibited the expression of Nrf2 (SMD = -1.27, 95% CI (-2.46, -0.09)) and GCLC (SMD = -5.37, 95% CI (-5.37, -2.20)); siNrf2 inhibited the expression of GCLC, and BSO inhibited the synthesis of GSH. There is a dose-dependent relationship between the effects of exposure on GSH in vitro. Conclusions. These indicate the difference between in vivo and in vitro studies of the effect of arsenic on glutathione synthesis. In vivo studies have shown that arsenic exposure can reduce glutamate and cysteine levels and inhibit glutathione synthesis, while in vitro studies have shown that chronic low-dose arsenic exposure can activate the p38/Nrf2 pathway, upregulate GCLC expression, and promote glutathione synthesis.

Melatonin triggers the anticancer potential of phenylarsine oxide via induction of apoptosis through ROS generation and JNK activation

Melatonin, a safe endogenous hormone and a natural supplement, has recently been recognized to have antiproliferative effects and the ability to sensitize cells to other anticancer therapies. Phenylarsine oxide (PAO) has anticancer potential but it is considered as a toxic agent. In this study we combined melatonin to reduce the toxicity while securing the anti-cancer effects of PAO. Cell viability was determined by MTT assay, whereas cytotoxic assays were performed using an LDH cytotoxicity assay kit. Cell cycle analysis, Annexin V/PI staining, the mitochondrial membrane potential (MMP), mitochondrial calcium and reactive oxygen species (ROS) generation were analyzed using flow cytometry. Sytox stained cells were visualized by fluorescence microscopy and the expression of proteins was detected by western blotting. Melatonin increased the anticancer potential of PAO by decreasing the cell viability and increasing LDH release in various cancer cells. The mode of cell death was determined to be typical apoptosis, as evidenced by Annexin V/PI-stained cells, PARP cleavage, and caspase-3 activation, and with significant modulations in the expression of proapoptotic, antiapoptotic and cell cycle-related proteins. ROS generation played a critical role in induction of cell death by this combined treatment, which is validated by reversal of cytotoxicity upon cotreatment with NAC. Furthermore, the activation of MAPKs, especially JNK, contributed to the induction of cell death, accompanied by endoplasmic reticulum stress and autophagy, affirmed by the abrogation of cytotoxicity after JNK-IN-8 and TUDCA application. Melatonin showed promising potential as a chemotherapeutic agent in combination with PAO to achieve a better anticancer response.

REDD1 overexpression in oral squamous cell carcinoma may predict poor prognosis and correlates with high microvessel density

The association between the hypoxia-inducible gene termed regulated in development and DNA damage responses 1 (REDD1) and microvessel density (MVD) in human oral cancer has rarely been reported. The present study aimed to explore REDD1 expression in oral squamous cell carcinoma (OSCC), its clinical prognostic significance and its correlation with angiogenesis. REDD1 expression in 23 pairs of fresh-frozen OSCC and matched peritumoral mucosal tissues was quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Furthermore, 74 formalin-fixed paraffin-embedded OSCC tissues were collected to detect REDD1 expression and CD34-positive MVD by immunohistochemistry (IHC). The association between REDD1 expression and MVD, patients' clinicopathological characteristics and cancer-associated survival rate was also evaluated using the log-rank (Mantel-Cox) test. The results from RT-qPCR and western blotting demonstrated that REDD1 expression was significantly higher in OSCC tissues compared with peritumoral mucosal tissues (P<0.05). In addition, the results from IHC revealed that REDD1 expression was higher in OSCC tissues compared with peritumoral tissues. Furthermore, REDD1 expression was associated with advanced clinical stage, poorer tumor differentiation, lymphatic metastasis and tumor recurrence (P=0.000, P=0.003, P=0.006 and P<0.001, respectively). Additionally, REDD1 overexpression was positively correlated with MVD (r=0.7316; P<0.001). The results from Kaplan-Meier survival analysis demonstrated a significantly reduced disease-free survival and overall survival in patients with OSCC and high REDD1 expression (P<0.001). REDD1 may therefore serve as a novel prognostic biomarker, a key regulatory checkpoint that could coordinate angiogenesis and a new therapeutic target for patients with OSCC.

Different Effects of Melatonin on X-Rays-Irradiated Cancer Cells in a Dose-Dependent Manner

The purpose of this study is to investigate the effects of melatonin on the radiosensitivity of HeLa cells. Concentration from 10 to 1000 µM of melatonin was used on HeLa cells before X-rays irradiation (IR). The cellular inactivation effect was analyzed by clonogenic assay, and cell growth was measured by MTT assay at various concentrations. Ten micrometer melatonin promoted the cell-killing effects of IR, while 1000-µM melatonin prevented IR-induced cellular inactivation. Further analysis revealed that 1000-µM melatonin protected the cells from IR-induced reactive oxygen species damage, as the oxidative stress measured by fluorescent microscopy and fluorescence-activated cell sorting using 2,7-dichlorofluorescein diacetate staining. This is further confirmed by melatonin receptor agonist, which has no antioxidant capacity. A 10-µM melatonin, on the contrary, enhanced the cell-killing effects of IR by activating c-Jun NH2-terminal kinase (JNK) signaling. c-Jun NH2-terminal kinase signaling activation was indicated by Western blot of phosphorylated JNK. We used JNK inhibitor to further confirm the involvement of JNK signaling in the cell-killing enhancement of 10-µM melatonin administration. Our results suggest the importance of dose-dependent effects in melatonin application for radiotherapy.

Aging, Melatonin, and the Pro- and Anti-Inflammatory Networks

Aging and various age-related diseases are associated with reductions in melatonin secretion, proinflammatory changes in the immune system, a deteriorating circadian system, and reductions in sirtuin-1 (SIRT1) activity. In non-tumor cells, several effects of melatonin are abolished by inhibiting SIRT1, indicating mediation by SIRT1. Melatonin is, in addition to its circadian and antioxidant roles, an immune stimulatory agent. However, it can act as either a pro- or anti-inflammatory regulator in a context-dependent way. Melatonin can stimulate the release of proinflammatory cytokines and other mediators, but also, under different conditions, it can suppress inflammation-promoting processes such as NO release, activation of cyclooxygenase-2, inflammasome NLRP3, gasdermin D, toll-like receptor-4 and mTOR signaling, and cytokine release by SASP (senescence-associated secretory phenotype), and amyloid-β toxicity. It also activates processes in an anti-inflammatory network, in which SIRT1 activation, upregulation of Nrf2 and downregulation of NF-κB, and release of the anti-inflammatory cytokines IL-4 and IL-10 are involved. A perhaps crucial action may be the promotion of macrophage or microglia polarization in favor of the anti-inflammatory phenotype M2. In addition, many factors of the pro- and anti-inflammatory networks are subject to regulation by microRNAs that either target mRNAs of the respective factors or upregulate them by targeting mRNAs of their inhibitor proteins.

Mitochondrial functions and melatonin: a tour of the reproductive cancers

Cancers of the reproductive organs have a strong association with mitochondrial defects, and a deeper understanding of the role of this organelle in preneoplastic-neoplastic changes is important to determine the appropriate therapeutic intervention. Mitochondria are involved in events during cancer development, including metabolic and oxidative status, acquisition of metastatic potential, resistance to chemotherapy, apoptosis, and others. Because of their origin from melatonin-producing bacteria, mitochondria are speculated to produce melatonin and its derivatives at high levels; in addition, exogenously administered melatonin accumulates in the mitochondria against a concentration gradient. Melatonin is transported into tumor cell by GLUT/SLC2A and/or by the PEPT1/2 transporters, and plays beneficial roles in mitochondrial homeostasis, such as influencing oxidative phosphorylation and electron flux, ATP synthesis, bioenergetics, calcium influx, and mitochondrial permeability transition pore. Moreover, melatonin promotes mitochondrial homeostasis by regulating nuclear DNA and mtDNA transcriptional activities. This review focuses on the main functions of melatonin on mitochondrial processes, and reviews from a mechanistic standpoint, how mitochondrial crosstalk evolved in ovarian, endometrial, cervical, breast, and prostate cancers relative to melatonin's known actions. We put emphasis on signaling pathways whereby melatonin interferes within cancer-cell mitochondria after its administration. Depending on subtype and intratumor metabolic heterogeneity, melatonin seems to be helpful in promoting apoptosis, anti-proliferation, pro-oxidation, metabolic shifting, inhibiting neovasculogenesis and controlling inflammation, and restoration of chemosensitivity. This results in attenuation of development, progression, and metastatic potential of reproductive cancers, in addition to lowering the risk of recurrence and improving the life quality of patients.

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.

Melatonin and inflammation-Story of a double-edged blade

Melatonin is an immune modulator that displays both pro- and anti-inflammatory properties. Proinflammatory actions, which are well documented by many studies in isolated cells or leukocyte-derived cell lines, can be assumed to enhance the resistance against pathogens. However, they can be detrimental in autoimmune diseases. Anti-inflammatory actions are of particular medicinal interest, because they are observed in high-grade inflammation such as sepsis, ischemia/reperfusion, and brain injury, and also in low-grade inflammation during aging and in neurodegenerative diseases. The mechanisms contributing to anti-inflammatory effects are manifold and comprise various pathways of secondary signaling. These include numerous antioxidant effects, downregulation of inducible and inhibition of neuronal NO synthases, downregulation of cyclooxygenase-2, inhibition of high-mobility group box-1 signaling and toll-like receptor-4 activation, prevention of inflammasome NLRP3 activation, inhibition of NF-κB activation and upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). These effects are also reflected by downregulation of proinflammatory and upregulation of anti-inflammatory cytokines. Proinflammatory actions of amyloid-β peptides are reduced by enhancing α-secretase and inhibition of β- and γ-secretases. A particular role in melatonin's actions seems to be associated with the upregulation of sirtuin-1 (SIRT1), which shares various effects known from melatonin and additionally interferes with the signaling by the mechanistic target of rapamycin (mTOR) and Notch, and reduces the expression of the proinflammatory lncRNA-CCL2. The conclusion on a partial mediation by SIRT1 is supported by repeatedly observed inhibitions of melatonin effects by sirtuin inhibitors or knockdown.

DDIT4 promotes gastric cancer proliferation and tumorigenesis through the p53 and MAPK pathways

Background

Gastric cancer (GC) is one of the most common malignancies worldwide, particularly in China. DNA damage-inducible transcript 4 (DDIT4) is a mammalian target of rapamycin inhibitor and is induced by various cellular stresses; however, its critical role in GC remains poorly understood. The present study aimed to investigate the potential relationship and the underlying mechanism between DDIT4 and GC development.

Methods

We used western blotting, real-time polymerase chain reaction, and immunohistochemical or immunofluorescence to determine DDIT4 expression in GC cells and tissues. High-content screening, cell counting kit-8 assays, colony formation, and in vivo tumorigenesis assays were performed to evaluate cell proliferation. Flow cytometry was used to investigate cell apoptosis and cell cycle distribution.

Results

DDIT4 was upregulated in GC cells and tissue. Furthermore, downregulating DDIT4 in GC cells inhibited proliferation both in vitro and in vivo and increased 5-fluorouracil-induced apoptosis and cell cycle arrest. In contrast, ectopic expression of DDIT4 in normal gastric epithelial cells promoted proliferation and attenuated chemosensitivity. Further analysis indicated that the mitogen-activated protein kinase and p53 signaling pathways were involved in the suppression of proliferation, and increased chemosensitivity upon DDIT4 downregulation.

Conclusion

DDIT4 promotes GC proliferation and tumorigenesis, providing new insights into the role of DDIT4 in the tumorigenesis of human GC.

Electronic supplementary material

The online version of this article (10.1186/s40880-018-0315-y) contains supplementary material, which is available to authorized users.

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.

Arsenic disulfide‑induced apoptosis and its potential mechanism in two‑ and three‑dimensionally cultured human breast cancer MCF‑7 cells

In China, arsenic disulfide (As2S2) has been used for the treatment of hematological malignancies. The present study aimed to evaluate the effects of As2S2 on the human breast cancer MCF‑7 cell line cultured in both two‑dimensional (2D) monolayers and three‑dimensional (3D) spheroids to explore its therapeutic potential in breast cancer treatment. Cellular viability and the induction of apoptosis were examined with a cell counting kit‑8 (CCK‑8) assay and flow cytometric analysis, respectively. Alterations in the expression levels of apoptosis‑associated proteins, including Bcl‑2‑associated X protein (Bax), B‑cell lymphoma 2 (Bcl‑2), p53, and caspase‑7, as well as the cell survival‑associated proteins, phosphatidylinositol 3‑kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR), were assessed by western blotting. Although a dose‑dependent reduction in cell viability, which occurred in association with the induction of apoptosis triggered by the addition of 2‑24 µM As2S2, was observed in both 2D‑ and 3D‑culture systems, 3D spheroids were less sensitive to the cytotoxic effect of As2S2 compared with the 2D cultured cells. A significant increase in the expression levels of Bax, p53, and caspase‑7 was observed in treated 2D‑cultured cells, whereas a similar increase in the expression levels of Bax was only confirmed in treated 3D spheroids, although there was a trend towards the increased expression of p53 and caspase‑7 in the 3D spheroids. These results suggested that these molecules are closely associated with As2S2‑mediated cytotoxicity in the two culture systems, and further suggested that the difference in the sensitivity to As2S2 between 2D monolayers and 3D spheroids may be attributed to the differential alterations in the expression levels of proteins associated with cell mortality. Significant downregulation of the expression levels of Bcl‑2, PI3K, Akt and mTOR was observed in the two culture systems. Taken together, the results of the present study demonstrated that As2S2 inhibits cell viability and induces apoptosis in both 2D‑ and 3D‑ cultured MCF‑7 cells, which may be associated with activation of the pro‑apoptotic pathway and the inhibition of pro‑survival signaling. These results have provided novel insights into clinical applications of As2S2 in the treatment of patients with breast cancer.

Combination of melatonin and rapamycin for head and neck cancer therapy: Suppression of AKT/mTOR pathway activation, and activation of mitophagy and apoptosis via mitochondrial function regulation

Head and neck squamous cell carcinoma (HNSCC) clearly involves activation of the Akt mammalian target of rapamycin (mTOR) signalling pathway. However, the effectiveness of treatment with the mTOR inhibitor rapamycin is often limited by chemoresistance. Melatonin suppresses neoplastic growth via different mechanisms in a variety of tumours. In this study, we aimed to elucidate the effects of melatonin on rapamycin-induced HNSCC cell death and to identify potential cross-talk pathways. We analysed the dose-dependent effects of melatonin in rapamycin-treated HNSCC cell lines (Cal-27 and SCC-9). These cells were treated with 0.1, 0.5 or 1 mmol/L melatonin combined with 20 nM rapamycin. We further examined the potential synergistic effects of melatonin with rapamycin in Cal-27 xenograft mice. Relationships between inhibition of the mTOR pathway, reactive oxygen species (ROS), and apoptosis and mitophagy reportedly increased the cytotoxic effects of rapamycin in HNSCC. Our results demonstrated that combined treatment with rapamycin and melatonin blocked the negative feedback loop from the specific downstream effector of mTOR activation S6K1 to Akt signalling, which decreased cell viability, proliferation and clonogenic capacity. Interestingly, combined treatment with rapamycin and melatonin-induced changes in mitochondrial function, which were associated with increased ROS production, increasing apoptosis and mitophagy. This led to increase cell death and cellular differentiation. Our data further indicated that melatonin administration reduced rapamycin-associated toxicity to healthy cells. Overall, our findings suggested that melatonin could be used as an adjuvant agent with rapamycin, improving effectiveness while minimizing its side effects.

Inhibiting MT2-TFE3-dependent autophagy enhances melatonin-induced apoptosis in tongue squamous cell carcinoma

Autophagy modulation is a potential therapeutic strategy for tongue squamous cell carcinoma (TSCC). Melatonin possesses significant anticarcinogenic activity. However, whether melatonin induces autophagy and its roles in cell death in TSCC are unclear. Herein, we show that melatonin induced significant apoptosis in the TSCC cell line Cal27. Apart from the induction of apoptosis, we demonstrated that melatonin-induced autophagic flux in Cal27 cells as evidenced by the formation of GFP-LC3 puncta, and the upregulation of LC3-II and downregulation of SQSTM1/P62. Moreover, pharmacological or genetic blockage of autophagy enhanced melatonin-induced apoptosis, indicating a cytoprotective role of autophagy in melatonin-treated Cal27 cells. Mechanistically, melatonin induced TFE3^(Ser321) dephosphorylation, subsequently activated TFE3 nuclear translocation, and increased TFE3 reporter activity, which contributed to the expression of autophagy-related genes and lysosomal biogenesis. Luzindole, a melatonin membrane receptor blocker, or MT2-siRNA partially blocked the ability of melatonin to promote mTORC1/TFE3 signaling. Furthermore, we verified in a xenograft mouse model that melatonin with hydroxychloroquine or TFE3-siRNA exerted a synergistic antitumor effect by inhibiting autophagy. Importantly, TFE3 expression positively correlated with TSCC development and poor prognosis in patients. Collectively, we demonstrated that the melatonin-induced increase in TFE3-dependent autophagy is mediated through the melatonin membrane receptor in TSCC. These data also suggest that blocking melatonin membrane receptor-TFE3-dependent autophagy to enhance the activity of melatonin warrants further attention as a treatment strategy for TSCC.

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.

Catalase down-regulation in cancer cells exposed to arsenic trioxide is involved in their increased sensitivity to a pro-oxidant treatment

Background

Pro-oxidant drugs have been proposed for treating certain cancers but the resistance developed by cancer cells to oxidative stress limits its potential use in clinics. To understand the mechanisms underlying resistance to oxidative stress, we found that the chronic exposure to an H₂O₂-generating system (ascorbate/menadione, Asc/Men) or catalase overexpression (CAT3 cells) increased the resistance of cancer cells to oxidative stress, likely by increasing the antioxidant status of cancer cells.

Methods

Modulation of catalase expression was performed by either protein overexpression or protein down-regulation using siRNA against catalase and aminotriazole as pharmacological inhibitor. The former approach was done by transfecting cells with a plasmid construct containing human catalase cDNA (CAT3 cells, derived from MCF-7 breast cancer cell line) or by generating resistant cells through chronic exposure to an oxidant injury (Resox cells). Cell survival was monitored by using the MTT reduction assay and further calculation of IC₅₀ values. Protein expression was done by Western blots procedures. The formation of reactive oxygen species was performed by flow cytometry. The transcriptional activity of human catalase promoter was assessed by using transfected cells with a plasmid containing the − 1518/+ 16 promoter domain.

Results

Using Resox and CAT3 cells (derived from MCF-7 breast cancer cell line) as models for cancer resistance to pro-oxidative treatment, we found that arsenic trioxide (ATO) remarkably sensitized Resox and CAT3 cells to Asc/Men treatment. Since catalase is a key antioxidant enzyme involved in detoxifying Asc/Men (as shown by siRNA-mediated catalase knockdown) that is overexpressed in resistant cells, we hypothesized that ATO might regulate the expression levels of catalase. Consistently, catalase protein level is decreased in Resox cells when incubated with ATO likely by a decreased transcriptional activity of the catalase promoter.

Conclusions

Our findings support the proposal that ATO should be administered in combination with pro-oxidant drugs to enhance cancer cell death in solid tumors.

Dichloroacetate potentiates tamoxifen-induced cell death in breast cancer cells via downregulation of the epidermal growth factor receptor

Metabolic reprogramming in cancer cells has recently been recognized as an essential hallmark of neoplasia. In this context, metabolic alterations represent an attractive therapeutic target, and encouraging results with drugs targeting various metabolic processes have been obtained in preclinical studies. Recently, several studies have suggested that dichloroacetate (DCA), a specific pyruvate dehydrogenase kinase inhibitor, may be a potential anticancer drug in a large number of diverse tumors. However, the precise mechanism is not fully understood, which is important for the use of DCA in cancer treatment. In the present study, we found that DCA sensitized MCF7 breast cancer cells to tamoxifen-induced cell death by decreasing epidermal growth factor receptor (EGFR) expression. The downregulation of EGFR was caused by degradation of the protein. Furthermore, p38 mitogen-activated protein kinase played an important role in DCA/tamoxifen-induced EGFR degradation. Finally, DCA also promoted comparable tamoxifen-induced cell death in tamoxifen-resistant MCF7 cells, which were established by long-term treatment with tamoxifen. In summary, our results suggest that DCA is an attractive potential drug that sensitizes cells to tamoxifen-induced cell death and overcome tamoxifen resistance via downregulation of EGFR expression in breast cancer cells.

Inhibition of REDD1 Sensitizes Bladder Urothelial Carcinoma to Paclitaxel by Inhibiting Autophagy

Purpose: Regulated in development and DNA damage response-1 (REDD1) is a stress-related protein and is involved in the progression of cancer. The role and regulatory mechanism of REDD1 in bladder urothelial carcinoma (BUC), however, is yet unidentified.Experimental Design: The expression of REDD1 in BUC was detected by Western blot analysis and immunohistochemistry (IHC). The correlation between REDD1 expression and clinical features in patients with BUC were assessed. The effects of REDD1 on cellular proliferation, apoptosis, autophagy, and paclitaxel sensitivity were determined both in vitro and in vivo Then the targeted-regulating mechanism of REDD1 by miRNAs was explored.Results: Here the significant increase of REDD1 expression is detected in BUC tissue, and REDD1 is first reported as an independent prognostic factor in patients with BUC. Silencing REDD1 expression in T24 and EJ cells decreased cell proliferation, increased apoptosis, and decreased autophagy, whereas the ectopic expression of REDD1 in RT4 and BIU87 cells had the opposite effect. In addition, the REDD1-mediated proliferation, apoptosis, and autophagy are found to be negatively regulated by miR-22 in vitro, which intensify the paclitaxel sensitivity via inhibition of the well-acknowledged REDD1-EEF2K-autophagy axis. AKT/mTOR signaling initially activated or inhibited in response to silencing or enhancing REDD1 expression and then recovered rapidly. Finally, the inhibited REDD1 expression by either RNAi or miR-22 sensitizes BUC tumor cells to paclitaxel in a subcutaneous transplant carcinoma model in vivoConclusions: REDD1 is confirmed as an oncogene in BUC, and antagonizing REDD1 could be a potential therapeutic strategy to sensitize BUC cells to paclitaxel. Clin Cancer Res; 24(2); 445-59. ©2017 AACR.

Melatonin, a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis

There is highly credible evidence that melatonin mitigates cancer at the initiation, progression and metastasis phases. In many cases, the molecular mechanisms underpinning these inhibitory actions have been proposed. What is rather perplexing, however, is the large number of processes by which melatonin reportedly restrains cancer development and growth. These diverse actions suggest that what is being observed are merely epiphenomena of an underlying more fundamental action of melatonin that remains to be disclosed. Some of the arresting actions of melatonin on cancer are clearly membrane receptor-mediated while others are membrane receptor-independent and involve direct intracellular actions of this ubiquitously-distributed molecule. While the emphasis of melatonin/cancer research has been on the role of the indoleamine in restraining breast cancer, this is changing quickly with many cancer types having been shown to be susceptible to inhibition by melatonin. There are several facets of this research which could have immediate applications at the clinical level. Many studies have shown that melatonin's co-administration improves the sensitivity of cancers to inhibition by conventional drugs. Even more important are the findings that melatonin renders cancers previously totally resistant to treatment sensitive to these same therapies. Melatonin also inhibits molecular processes associated with metastasis by limiting the entrance of cancer cells into the vascular system and preventing them from establishing secondary growths at distant sites. This is of particular importance since cancer metastasis often significantly contributes to death of the patient. Another area that deserves additional consideration is related to the capacity of melatonin in reducing the toxic consequences of anti-cancer drugs while increasing their efficacy. Although this information has been available for more than a decade, it has not been adequately exploited at the clinical level. Even if the only beneficial actions of melatonin in cancer patients are its ability to attenuate acute and long-term drug toxicity, melatonin should be used to improve the physical wellbeing of the patients. The experimental findings, however, suggest that the advantages of using melatonin as a co-treatment with conventional cancer therapies would far exceed improvements in the wellbeing of the patients.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Reactive oxygen species and cancer paradox: To promote or to suppress?

Reactive oxygen species (ROS), a group of highly reactive ions and molecules, are increasingly being appreciated as powerful signaling molecules involved in the regulation of a variety of biological processes. Indeed, their role is continuously being delineated in a variety of pathophysiological conditions. For instance, cancer cells are shown to have increased ROS levels in comparison to their normal counterparts. This is partly due to an enhanced metabolism and mitochondrial dysfunction in cancer cells. The escalated ROS generation in cancer cells contributes to the biochemical and molecular changes necessary for the tumor initiation, promotion and progression, as well as, tumor resistance to chemotherapy. Therefore, increased ROS in cancer cells may provide a unique opportunity to eliminate cancer cells via elevating ROS to highly toxic levels intracellularly, thereby, activating various ROS-induced cell death pathways, or inhibiting cancer cell resistance to chemotherapy. Such results can be achieved by using agents that either increase ROS generation, or inhibit antioxidant defense, or even a combination of both. In fact, a large variety of anticancer drugs, and some of those currently under clinical trials, effectively kill cancer cells and overcome drug resistance via enhancing ROS generation and/or impeding the antioxidant defense mechanism. This review focuses on our current understanding of the tumor promoting (tumorigenesis, angiogenesis, invasion and metastasis, and chemoresistance) and the tumor suppressive (apoptosis, autophagy, and necroptosis) functions of ROS, and highlights the potential mechanism(s) involved. It also sheds light on a very novel and an actively growing field of ROS-dependent cell death mechanism referred to as ferroptosis.

Metformin potentiates the effect of arsenic trioxide suppressing intrahepatic cholangiocarcinoma: roles of p38 MAPK, ERK3, and mTORC1

Background

Arsenic trioxide (ATO) is commonly used in the treatment of acute promyelocytic leukemia (APL), but does not benefit patients with solid tumors. When combined with other agents or radiation, ATO showed treatment benefits with manageable toxicity. Previously, we reported that metformin amplified the inhibitory effect of ATO on intrahepatic cholangiocarcinoma (ICC) cells more significantly than other agents. Here, we investigated the chemotherapeutic sensitization effect of metformin in ATO-based treatment in ICC in vitro and in vivo and explored the underlying mechanisms.

Methods

ICC cell lines (CCLP-1, RBE, and HCCC-9810) were treated with metformin and/or ATO; the anti-proliferation effect was evaluated by cell viability, cell apoptosis, cell cycle, and intracellular-reactive oxygen species (ROS) assays. The in vivo efficacy was determined in nude mice with CCLP-1 xenografts. The active status of AMPK/p38 MAPK and mTORC1 pathways was detected by western blot. In addition, an antibody array was used screening more than 200 molecules clustered in 12 cancer-related pathways in CCLP-1 cells treated with metformin and/or ATO. Methods of genetic modulation and pharmacology were further used to demonstrate the relationship of the molecule. Seventy-three tumor samples from ICC patients were used to detect the expression of ERK3 by immunohistochemistry. The correlation between ERK3 and the clinical information of ICC patients were further analyzed.

Results

Metformin and ATO synergistically inhibited proliferation of ICC cells by promoting cell apoptosis, inducing G0/G1 cell cycle arrest, and increasing intracellular ROS. Combined treatment with metformin and ATO efficiently reduced ICC growth in an ICC xenograft model. Mechanistically, the antibody array revealed that ERK3 exhibited the highest variation in CCLP-1 cells after treatment with metformin and ATO. Results of western blot confirm that metformin and ATO cooperated to inhibit mTORC1, activate AMP-activated protein kinase (AMPK), and upregulate ERK3. Metformin abrogated the activation of p38 MAPK induced by ATO, and this activity was partially dependent on AMPK activation. Inactivation of p38 MAPK by SB203580 or specific short interfering RNA (siRNA) promoted the inactivation of mTORC1 in ICC cells treated with metformin and ATO. Activation of p38 MAPK may be responsible for resistance to ATO in ICC. The relationship between p38 MAPK and ERK3 was not defined by our findings. Finally, AMPK is a newfound positive regulator of ERK3. Overexpression of EKR3 in ICC cells inhibited cell proliferation through inactivation of mTORC1. ERK3 expression is associated with a better prognosis in ICC patients.

Conclusions

Metformin sensitizes arsenic trioxide to suppress intrahepatic cholangiocarcinoma via the regulation of AMPK/p38 MAPK-ERK3/mTORC1 pathways. ERK3 is a newfound potential prognostic predictor and a tumor suppressor in ICC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-017-0424-0) contains supplementary material, which is available to authorized users.

The Pathophysiologic Role of Disrupted Circadian and Neuroendocrine Rhythms in Breast Carcinogenesis

Most physiological processes in the brain and body exhibit daily (circadian) rhythms coordinated by an endogenous master clock located in the suprachiasmatic nucleus of the hypothalamus that are essential for normal health and functioning. Exposure to sunlight during the day and darkness at night optimally entrains biological rhythms to promote homeostasis and human health. Unfortunately, a major consequence of the modern lifestyle is increased exposure to sun-free environments during the day and artificial lighting at night. Additionally, behavioral disruptions to circadian rhythms (ie, repeated transmeridian flights, night or rotating shift work, or sleep disturbances) have a profound influence on health and have been linked to a number of pathological conditions, including endocrine-dependent cancers. Specifically, night shift work has been identified as a significant risk factor for breast cancer in industrialized countries. Several mechanisms have been proposed by which shift work-induced circadian disruptions promote cancer. In this review, we examine the importance of the brain-body link through which circadian disruptions contribute to endocrine-dependent diseases, including breast carcinogenesis, by negatively impacting neuroendocrine and neuroimmune cells, and we consider preventive measures directed at maximizing circadian health.