Arsenic trioxide induces the apoptosis of human breast cancer MCF-7 cells through activation of caspase-3 and inhibition of HERG channels

Arsenic trioxide: applications, mechanisms of action, toxicity and rescue strategies to date

Arsenical medicine has obtained its status in traditional Chinese medicine for more than 2,000 years. In the 1970s, arsenic trioxide was identified to have high efficacy and potency for the treatment of acute promyelocytic leukemia, which promoted many studies on the therapeutic effects of arsenic trioxide. Currently, arsenic trioxide is widely used to treat acute promyelocytic leukemia and various solid tumors through various mechanisms of action in clinical practice; however, it is accompanied by a series of adverse reactions, especially cardiac toxicity. This review presents a comprehensive overview of arsenic trioxide from preclinical and clinical efficacy, potential mechanisms of action, toxicities, and rescue strategies for toxicities to provide guidance or assistance for the clinical application of arsenic trioxide.

Nanotechnological Advancements for the Theranostic Intervention in Anaplastic Thyroid Cancer: Current Perspectives and Future Direction

Anaplastic thyroid cancer is the rarest, most aggressive, and undifferentiated class of thyroid cancer, accounting for nearly forty percent of all thyroid cancer-related deaths. It is caused by alterations in many cellular pathways like MAPK, PI3K/AKT/mTOR, ALK, Wnt activation, and TP53 inactivation. Although many treatment strategies, such as radiation therapy and chemotherapy, have been proposed to treat anaplastic thyroid carcinoma, they are usually accompanied by concerns such as resistance, which may lead to the lethality of the patient. The emerging nanotechnology-based approaches cater the purposes such as targeted drug delivery and modulation in drug release patterns based on internal or external stimuli, leading to an increase in drug concentration at the site of the action that gives the required therapeutic action as well as modulation in diagnostic intervention with the help of dye property materials. Nanotechnological platforms like liposomes, micelles, dendrimers, exosomes, and various nanoparticles are available and are of high research interest for therapeutic intervention in anaplastic thyroid cancer. The pro gression of the disease can also be traced by using magnetic probes or radio-labeled probes and quantum dots that serve as a diagnostic intervention in anaplastic thyroid cancer.

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.

Arsenic and Human Health: Genotoxicity, Epigenomic Effects, and Cancer Signaling

Arsenic is a well-known element because of its toxicity. Humans as well as plants and animals are negatively affected by its exposure. Some countries suffer from high levels of arsenic in their tap water and soils, which is considered a primary arsenic-linked risk factor for living beings. Humans generally get exposed to arsenic by contaminated drinking waters, resulting in many health problems, ranging from cancer to skin diseases. On the other hand, the FDA-certified drug arsenic trioxide provides solutions for various diseases, including several types of cancers. This issue emphasizes the importance of speciation of the metalloid elements in terms of impacts on health. When species get exposed to arsenic, it affects the cells altering their involvement. It can lead to abnormalities in inflammatory mechanisms and the immune system which contribute to the negative impacts generated on the body. The poisoning originating from arsenic gives rise to various biological signs on the body which can be useful for the diagnosis. It is important to find true biomarkers for the detection of arsenic poisoning. In view of its application in medicine and biology, studies on understanding the biological activity of arsenic have increased. In this review, we aim at summarizing the current state of knowledge of arsenic and the mechanism behind its toxicity including genotoxicity, oxidative insults, epigenomic changes, and alterations in cellular signaling.

Network controllability solutions for computational drug repurposing using genetic algorithms

Control theory has seen recently impactful applications in network science, especially in connections with applications in network medicine. A key topic of research is that of finding minimal external interventions that offer control over the dynamics of a given network, a problem known as network controllability. We propose in this article a new solution for this problem based on genetic algorithms. We tailor our solution for applications in computational drug repurposing, seeking to maximize its use of FDA-approved drug targets in a given disease-specific protein-protein interaction network. We demonstrate our algorithm on several cancer networks and on several random networks with their edges distributed according to the Erdős-Rényi, the Scale-Free, and the Small World properties. Overall, we show that our new algorithm is more efficient in identifying relevant drug targets in a disease network, advancing the computational solutions needed for new therapeutic and drug repurposing approaches.

Down-regulation of RdRp complex and activated immune response due to increased arsenic level leads to decreased corona virus replication

Corona virus is pandemic and responsible for more than 5.6 million deaths. It was observed that its severity was reported in varied ways in different countries and even in different states of India. This variation was critically evaluated in the area with high contamination of Arsenic (As) to understand the arsenic toxicity and Covid epidemiology and associated health effects in the human population. It was reported that the area with low arsenic contamination has a very high incidence rate of Corona infection in the world. Even in the Indian scenario, high As-contaminated states like West Bengal, Jharkhand and Bihar, the incidence rate is 1.994%, 1.114% and 0.661%, respectively. In contrast, states with the least arsenic contamination have a very high corona incidence rate like 6.308, 17.289 and 4.351, respectively. It was evident that Arsenic inhibits the RdRp complex, which leads to the inhibition of viral genome replication. The PAMP associated pathway was activated by Arsenic and effectively bound with viral spike proteins leading to effective clearance of virus through activation of TNF alpha and IL-1. It finally leads to increased production of IgE, IgG and IGA. Arsenic also enhances inflammatory response against the virus through increased production of cytokine. The high arsenic level also induces apoptosis in viral infected cells through Bax/Bak pathway. It activates cytochrome-c and caspase-3 activity, inducing apoptosis in viral infected cells through PARP activation in the nucleus. These combined findings suggest that high arsenic contamination causes replication inhibition, activates an inflammatory response, increases antibody production, and finally leads to apoptosis through the mitochondrial pathway. People residing in arsenic hit areas are at a very low threat of corona infection.

Ethnopharmacological study of natural products used for traditional cancer therapy in Algeria

Traditional and complementary medicine constitutes an important, and often underestimated, source of healthcare for multiple diseases including cancer. However, little is known about the ethnomedical knowledge and practices in Northern Africa. The main objective of this study is to identify and analyze the variety of natural products used in Algerian ethnopharmacology for cancer therapy. For this purpose, semi-structured interviews with 225 traditional healers, herbalists and practitioners were realized in twelve locations in Algeria throughout field studies performed from June 2015 to July 2019. Interviews covered popular and vernacular names of the natural product, mode of use and administration, dose, period of treatment, toxicity and side effects among other data. The obtained results reveal the use of 113 medicinal plants (belonging to 53 families and 104 genera), 10 animal species and various products and by-products from different origins such as honey, olive oil, thorns, urine, milk, animal fat and the alkaline water of Zamzam. Basing on the frequency of citation (FC), use reports (UR) and use value (UV), the most used natural products for cancer treatment are honey (FC = 181, UR = 194, UV = 0.65), Nigella sativa L. (FC = 131, UR = 152, UV = 0.54), Aristolochia longa L. (FC = 118, UR = 144, UV = 0.51), Berberis vulgaris L. (FC = 111, UR = 142, UV = 0.51), Curcuma longa L. (FC = 107, UR = 121, UV = 0.43), Trigonella foenum-graecum L. (FC = 102; UR = 119, UV = 0.43), Citrus limon (L.) Obseck (FC = 97, UR = 120, UV = 0.43), Artemisia herba-alba Asso (FC = 92, UR = 115, UV = 0.41) and the holy water 'Zamzam' (FC = 110, UR = 110, UV = 0.43) respectively. Mixtures of two or more ingredients were frequently used. The use of Pelophylax saharicus skin' was reported for the first time for the treatment of visible tumors and skin cancer. This is the first study documenting the traditional uses of various natural products for cancer treatment in Algeria. Our findings are relevant to document the traditional uses of numerous natural products and to provide background basis to search for novel compounds for cancer therapy.

Arsenic trioxide and BIBR1532 synergistically inhibit breast cancer cell proliferation through attenuation of NF-κB signaling pathway

AIMS

Despite the remarkable anti-proliferative effects of Arsenic trioxide (ATO) in breast cancer cells, the requirement of high, toxic concentrations to induce apoptosis may cause serious side effects in patients. In the present study, we aimed to use BIBR1532, an hTERT inhibitor, in combination with ATO to sensitize MCF7 and MDA-231 cells to lower concentrations of ATO.

MAIN METHODS

Breast cancer cell lines MCF7 and MDA-231 were cultured and treated with different doses of ATO and BIBR1532 for 48 h and its effects on cell survival and proliferation were analyzed by MTT, crystal violet staining, colony formation assay, cell cycle, AnnexinV/PI and Real-time PCR tests.

KEY FINDINGS

ATO and BIBR1532 synergistically inhibited proliferation and colony-forming ability of breast cancer cells. Besides, BIBR1532 augmented ATO-induced cytotoxic effects via triggering G1 cell cycle arrest and induction of apoptosis coupled with the down-regulation of NF-κB target genes that were involved in cell cycle progression (e.g. CCND1 and CDK6) and prevention of apoptosis such as Bcl-2, Bcl-xl, c-IAP2, and Survivin Respectively. Moreover, ATO-BIBR1532 significantly reduced the mRNA expression level of RELA, NFKB1, and several validated target genes of the NF-κB signaling pathway including NFKBIA, VEGFC, c-Myc, and hTERT.

SIGNIFICANCE

The combination of ATO and BIBR1532 synergistically induced its anti-proliferative effect in breast cancer cells by targeting the two key cancer-related pathways, hTERT and NF-κB, and disrupting their feed-forward loop at the same time which result in the reduction of NF-κB transcriptional activity and subsequent down-regulation of its target genes.

Focus on Triple-Negative Breast Cancer: Potassium Channel Expression and Clinical Correlates

Despite improvements in early diagnosis and treatment, breast cancer is still a major health problem worldwide. Among breast cancer subtypes, the most challenging and harder to treat is represented by triple-negative molecular subtype. Due to its intrinsic features this subtype cannot be treated neither with hormonal therapy (since it does not express estrogen or progesterone receptors) nor with epidermal growth factor receptor 2 (HER2) inhibitors (as it does not express high levels of this protein). For these reasons, the standard of care for these patients is represented by a combination of surgery, radiation therapy and chemotherapy. In this scenario, searching for novel biomarkers that might help both in diagnosis and therapy is mandatory. In the last years, it was shown that different families of potassium channels are overexpressed in primary breast cancers. The altered ion channel expression may be useful for diagnostic and therapeutic purposes due to some peculiar characteristics of this class of molecules. Ion channels are defined as pore-forming transmembrane proteins regulating passive ion fluxes in the cells. Ion channels represent good potential markers since, being localized at the plasma membrane level, their detection and block with specific drugs and antibodies might be fast and tunable. This review focuses on triple-negative breast cancers and recapitulates the current knowledge about potassium channels' clinical relevance and their potential use in the clinical setting, for triple-negative breast cancer diagnosis and therapy.

Downregulation of RBBP6 variant 1 during arsenic trioxide-mediated cell cycle arrest and curcumin-induced apoptosis in MCF-7 breast cancer cells

Aim

To determine the expression patterns of the RBBP6 spliced variants during arsenic trioxide-mediated cell cycle arrest and curcumin-induced apoptosis in MCF-7 cells.

Materials & methods

As₂O₃ and curcumin were used to study cytotoxicity, cell cycle arrest, apoptosis and the expression of RBBP6 variants. The MUSE Cell Analyser was used to analyze cell cycle arrest, apoptosis and multicaspase activity while apoptosis was further confirmed using microscopy. Semi-quantitative RT-PCR was employed to quantitate the expression of the RBBP6 variants.

Results

This study showed that the MCF-7 cells expressed RBBP6 variant 1 but lacked both variant 2 and variant 3. Both As₂O₃ and curcumin significantly downregulated RBBP6 variant 1 (p < 0.001).

Conclusion

RBBP6 variants are promising therapeutic targets.

Survivin Splice Variants in Arsenic Trioxide (As₂O₃)-Induced Deactivation of PI3K and MAPK Cell Signalling Pathways in MCF-7 Cells

Several pathways are deregulated during carcinogenesis but most notably, tumour cells can lose cell cycle control and acquire resistance to apoptosis by expressing a number of anti-apoptotic proteins such as the Inhibitors of Apoptosis Protein (IAP) family of proteins that include survivin, which is implicated in cancer development. There is no study which had proven that arsenic trioxide (As₂O₃) has any effect on the splicing machinery of survivin and its splice variants, hence this study was aimed at determining the cytotoxic effect of As₂O₃ and its effect on the expression pattern of survivin splice variants in MCF-7 cells. As₂O₃ inhibited the growth of the MCF-7 cells in a concentration-dependent manner. The Muse^® Cell Analyser showed that As₂O₃-induced G2/M cell cycle arrest, promoted caspase-dependent apoptosis without causing any damage to the mitochondrial membrane of MCF-7 cells. As₂O₃ also deactivated two survival pathways, Mitogen-Activated Protein Kinase (MAPK) and Phosphoinositide 3-Kinase (PI3K) signalling pathways in MCF-7 cells. Deactivation of the two pathways was accompanied by the upregulation of survivin 3α during As₂O₃-induced G2/M cell cycle arrest and apoptosis. Survivin 2B was found to be upregulated only during As₂O₃-induced G2/M cell cycle arrest but downregulated during As₂O₃-induced apoptosis. Survivin wild-type was highly expressed in the untreated MCF-7 cells, the expression was upregulated during As₂O₃-induced G2/M cell cycle arrest and it was downregulated during As₂O₃-induced apoptosis. Survivin variant ΔEx3 was undetected in both untreated and treated MCF-7 cells. Survivin proteins were localised in both the nucleus and cytoplasm in MCF-7 cells and highly upregulated during the As₂O₃-induced G2/M cell cycle arrest, which can be attributed to the upregulation of survivin-2B. This study has provided the first evidence showing that the novel survivin 2B splice variant may be involved in the regulation of As₂O₃-induced G2/M cell cycle arrest only. This splice variant can therefore, be targeted for therapeutic purposes against Luminal A breast cancer cells.

Boron inhibits apoptosis in hyperapoptosis condition: Acts by stabilizing the mitochondrial membrane and inhibiting matrix remodeling

An abnormally high apoptosis has been associated with a number of clinical conditions including embryonal malformations and various pathologies such as neuronal degeneration and diabetes. In this study, boron is reported to inhibit apoptosis in hyperapoptosis conditions as demonstrated in a model of hyperapoptosis. Boron is a metalloid which is present in food in small amounts and is suggested here to inhibit apoptosis by stabilizing the mitochondrial membrane structure, thus preventing matrix remodeling and the release of cytochrome c, an apoptosis-inducer protein from the mitochondrion. The protective effect was assessed by measuring the changes in mitochondrial membrane potential, the levels of cytochrome c and downstream activation of caspase 3, besides phosphatidylserine exposure on the cell surface and DNA damage. The study has implication in clinical conditions characterized by hyperapoptosis as seen in certain embryonal malformations and various pathologies.

Synthesis and characterisation of arsenic nanoparticles and its interaction with DNA and cytotoxic potential on breast cancer cells

Therapeutic applications of arsenic trioxide (ATO) are limited due to their severe adverse effects. However, nanoparticles of ATO might possess inimitable biologic effects based on their structure and size which differ from their parent molecules. Based on this conception, AsNPs were synthesized from ATO and comparatively analysed for their interaction mechanism with DNA using spectroscopic & electrochemical techniques. Finally, anti-proliferative activity was assessed against different breast cancer cells (MDA-MB-231 & MCF-7) and normal non-cancerous cells (HEK-293). The DNA interaction study revealed that AsNPs and ATO exhibit binding constant values in the order of 10⁶ which indicates strong binding interaction. Binding of AsNPs did not disturb the structural integrity of DNA, on the other hand an opposing effect was observed with ATO through biophysical techniques. Further, in vitro study, confirms cytotoxicity of ATO and AsNPs against different cells, however at particular concentration ATO exhibits more cytotoxicity than that of AsNPs. Furthermore, cytotoxicity was confirmed through acridine orange and comet assay. In conclusion, AsNPs are safer than ATO with comparable efficacy and might be a suitable candidate for the development of novel therapeutic agent against breast cancer and other solid tumours.

Preclinical study of a Kv11.1 potassium channel activator as antineoplastic approach for breast cancer

Potassium ion (K⁺) channels have been recently found to play a critical role in cancer biology. Despite that pharmacologic manipulation of ion channels is recognized as an important therapeutic approach, very little is known about the effects of targeting of K⁺ channels in cancer. In this study, we demonstrate that use of the Kv11.1 K⁺ channel activator NS1643 inhibits tumor growth in an in vivo model of breast cancer.

Tumors exposed to NS1643 had reduced levels of proliferation markers, high expression levels of senescence markers, increased production of ROS and DNA damage compared to tumors of untreated mice. Importantly, mice treated with NS1643 did not exhibit significant cardiac dysfunction. In conclusion, pharmacological stimulation of Kv11.1 activity produced arrested TNBC-derived tumor growth by generating DNA damage and senescence without significant side effects. We propose that use of Kv11.1 channels activators could be considered as a possible pharmacological strategy against breast tumors.

Arsenic trioxide inhibits cell growth and motility via up-regulation of let-7a in breast cancer cells

Arsenic trioxide (ATO) has been reported to exert its anti-cancer activities in human cancers. However, the molecular mechanism of ATO-triggered anti-tumor activity has not been fully elucidated. Recently, multiple studies demonstrated that ATO could regulate miRNAs in human cancers. Therefore, in this study, we investigated whether ATO regulated let-7a in breast cancer cells. We found that ATO upregulated let-7a level in breast cancer cells. We also found that up-regulation of let-7a inhibited cell growth and induced apoptosis and retarded cell migration and invasion. We also observed that up-regulation of let-7a enhanced cell growth inhibition and invasion suppression induced by ATO treatment. Our findings suggest that ATO suppressed cell growth, stimulated apoptosis, and retarded cell invasion partly via upregulation of let-7a in breast cancer cells. Our study provides a new anti-tumor mechanism of ATO treatment in breast cancer.

Nanomaterials as nanocarriers: a critical assessment why these are multi-chore vanquisher in breast cancer treatment

Breast cancer is a group of diseases with various subtypes and leads to high mortality throughout the globe. Various conventional techniques are in practice to cure breast cancer but these techniques are linked with various shortcomings. Mostly these treatments are not site directed and cause toxicity towards normal cells. In order to overcome these issues, we need smart system that can deliver anticancer drugs to specific sites. Targeted drug delivery can be achieved via passive or active drug delivery using nanocarriers. This mode of drug delivery is more effective against breast cancer and may help in the reduction of mortality rate. Potentially used nanocarriers for targeted drug delivery belong to organic and inorganic molecules. Various FDA approved nano products are in use to cure breast cancer. However, body's defense system is main limitation for potential use of nano systems. However, this can be overcome by surface modification of nanocarriers. In this review, breast cancer and its types, targeted drug delivery and nanocarriers used to cure breast cancer are discussed. By progressing nanotechnology, we will be able to fight against this life threatening issue and serve the humanity, which is the basic aim of scientific knowledge.

Cadmium, arsenic, selenium and iron- Implications for tumor progression in breast cancer

The aim of this study was to determine Cd (cadmium) and As (arsenic) contents in human breast cancer tissues, investigate their interactions with Se (selenium) and Fe (iron), and assess their further implications for tumor progression. Metal contents were determined in 42 tissue sets (tumor and adjacent tissue) collected from 42 women diagnosed with primary breast cancer. Analytical methods included AAS and ICP-MS techniques. Significantly higher contents of Cd (p=0.0003), Se (p<0.0001) and Fe (p=0.0441) whereas significantly lower content of As (p<0.0001) were observed in tumors as compared to adjacent tissues. There was a significant positive correlation between Cd and As contents in tumor tissue. However, only Cd was significantly associated with histological type of tumor, its size, grading and progesterone receptor status. This study support the role of Cd in breast cancer risk and progression. The possible link between As exposure and breast cancer is still not clear.

Molecular insight of arsenic-induced carcinogenesis and its prevention

Population of India and Bangladesh and many other parts of the world are badly exposed to arsenic through drinking water. Due to non-availability of safe drinking water, they are dependent on arsenic-contaminated water. Generally, poverty level is high in those areas with lack of proper nutrition. Arsenic is considered to be an environmental contaminant and widely distributed in the environment due to its natural existence and anthropogenic applications. Contamination of arsenic in both human and animal could occur through air, soil, and other sources. Arsenic exposure mainly occurs in food materials through drinking water with high levels of arsenic in it. High levels of arsenic in groundwater have been found to be associated with various health-related problems including arsenicosis, skin lesions, cardiovascular diseases, reproductive problems, psychological, neurological, immunotoxic, and carcinogenesis. The mechanism of arsenic toxicity consists in its transformation in metaarsenite, which acylates protein sulfhydryl groups, affect on mitochondria by inhibiting succinic dehydrogenase activity and can uncouple oxidative phosphorylation with production of active oxygen species by tissues. A variety of dietary antioxidant supplements are useful to protect the carcinogenetic effects of arsenic. They play crucial role for counteracting oxidative damage and protect carcinogenesis by chelating with heavy metal moiety. Phytochemicals and chelating agents will be beneficial for combating heavy metal-induced carcinogenesis through its biopharmaceutical properties.

Metabolomic Characterizations of Liver Injury Caused by Acute Arsenic Toxicity in Zebrafish

Arsenic is one of the most common metalloid contaminants in groundwater and it has both acute and chronic toxicity affecting multiple organs. Details of the mechanism of arsenic toxicity are still lacking and profile studies at metabolic level are very limited. Using gas chromatography coupled with mass spectroscopy (GC/MS), we first generated metabolomic profiles from the livers of arsenic-treated zebrafish and identified 34 significantly altered metabolite peaks as potential markers, including four prominent ones: cholic acid, glycylglycine, glycine and hypotaurine. Combined results from GC/MS, histological examination and pathway analyses suggested a series of alterations, including apoptosis, glycogenolysis, changes in amino acid metabolism and fatty acid composition, accumulation of bile acids and fats, and disturbance in glycolysis related energy metabolism. The alterations in glycolysis partially resemble Warburg effect commonly observed in many cancer cells. However, cellular damages were not reflected in two conventional liver function tests performed, Bilirubin assay and alanine aminotransferase (ALT) assay, probably because the short arsenate exposure was insufficient to induce detectable damage. This study demonstrated that metabolic changes could reflect mild liver impairments induced by arsenic exposure, which underscored their potential in reporting early liver injury.

In the war against solid tumors arsenic trioxide needs partners

In the past decade, the therapeutic potential of arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL) was recognized. This encouraged other investigators to test the efficacy of ATO in the management of other hematological and solid tumor malignancies. Notably, as a single agent, arsenic trioxide did not benefit patients diagnosed with solid tumors. However, when it was combined with other agents, treatment benefit emerged. In this article, we have summarized the outcome of clinical trials that used arsenic trioxide as a single agent as well as in combination settings in patients diagnosed with solid tumors. We have also reviewed possible additional mechanisms by which ATO may be useful as a chemosensitizer in combination therapy. We hope that our review will encourage clinical investigators to rationally combine ATO with additional chemotherapeutic agents in treating patients diagnosed with solid tumors.

Arsenic trioxide inhibits breast cancer cell growth via microRNA-328/hERG pathway in MCF-7 cells

Arsenic trioxide (As2O3) has been widely used in the treatment of acute promyelocytic leukemia and has been observed to exhibit therapeutic effects in various types of solid tumor. In a previous study by this group, it was shown that As2O3 induces the apoptosis of MCF-7 breast cancer cells through inhibition of the human ether-à-go-go-related gene (hERG) channel. The present study was designed to further investigate the effect of As2O3 on breast cancer cells and to examine the mechanism underlying the regulation of hERG expression. The present study confirmed that As2O3 inhibited tumor growth in vivo, following MCF-7 cell implantation into nude mice. Using computational prediction , it was identified that microRNA (miR)-328 had a binding site in the 3'-untranslated region of hERG mRNA. A luciferase activity assay demonstrated that hERG is a target gene of miR-328. Further investigation using western blot analysis and reverse transcription-quantitative polymerase chain reaction revealed that As2O3 downregulated hERG expression via upregulation of miR-328 expression in MCF-7 cells. In conclusion, As2O3 was observed to inhibit breast cancer cell growth, at least in part, through the miR-328/hERG pathway.

Rapid reduction in breast cancer mortality with inorganic arsenic in drinking water

BACKGROUND

Arsenic trioxide is effective in treating promyelocytic leukemia, and laboratory studies demonstrate that arsenic trioxide causes apoptosis of human breast cancer cells. Region II in northern Chile experienced very high concentrations of inorganic arsenic in drinking water, especially in the main city Antofagasta from 1958 until an arsenic removal plant was installed in 1970.

METHODS

We investigated breast cancer mortality from 1950 to 2010 among women in Region II compared to Region V, which had low arsenic water concentrations. We conducted studies on human breast cancer cell lines and compared arsenic exposure in Antofagasta with concentrations inducing apoptosis in laboratory studies.

FINDINGS

Before 1958, breast cancer mortality rates were similar, but in 1958-1970 the rates in Region II were half those in Region V (rate ratio RR = 0·51, 95% CI 0·40-0·66; p<0·0001). Women under the age of 60 experienced a 70% reduction in breast cancer mortality during 1965-1970 (RR=0·30, 0·17-0·54; p<0·0001). Breast cancer cell culture studies showed apoptosis at arsenic concentrations close to those estimated to have occurred in people in Region II.

INTERPRETATION

We found biologically plausible major reductions in breast cancer mortality during high exposure to inorganic arsenic in drinking water which could not be attributed to bias or confounding. We recommend clinical trial assessment of inorganic arsenic in the treatment of advanced breast cancer.

AMP-activated protein kinase regulates hERG potassium channel

Besides their role in cardiac repolarization, human ether-a-go-go-related gene potassium (hERG) channels are expressed in several tumor cells including rhabdomyosarcoma cells. The channels foster cell proliferation. Ubiquitously expressed AMP-dependent protein kinase (AMPK) is a serine-/threonine kinase, stimulating energy-generating and inhibiting energy-consuming processes thereby helping cells survive periods of energy depletion. AMPK has previously been shown to regulate Na⁺/K⁺ ATPase, Na⁺/Ca²⁺ exchangers, Ca²⁺ channels and K⁺ channels. The present study tested whether AMPK regulates hERG channel activity. Wild type AMPK (α1β1γ1), constitutively active (γR70Q)AMPK (α1β1γ1(R70Q)), or catalytically inactive (αK45R)AMPK (α1(K45R)β1γ1) were expressed in Xenopus oocytes with hERG. Tail currents were determined as a measure of hERG channel activity by two-electrode-voltage clamp. hERG membrane abundance was quantified by chemiluminescence and visualized by immunocytochemistry and confocal microscopy. Moreover, hERG currents were measured in RD rhabdomyosarcoma cells after pharmacological modification of AMPK activity using the patch clamp technique. Coexpression of wild-type AMPK and of constitutively active (γR70Q)AMPK significantly downregulated the tail currents in hERG-expressing Xenopus oocytes. Pharmacological activation of AMPK with AICAR or with phenformin inhibited hERG currents in Xenopus oocytes, an effect abrogated by AMPK inhibitor compound C. (γR70Q)AMPK enhanced the Nedd4-2-dependent downregulation of hERG currents. Coexpression of constitutively active (γR70Q)AMPK decreased membrane expression of hERG in Xenopus oocytes. Compound C significantly enhanced whereas AICAR tended to inhibit hERG currents in RD rhabdomyosarcoma cells. AMPK is a powerful regulator of hERG-mediated currents in both, Xenopus oocytes and RD rhabdomyosarcoma cells. AMPK-dependent regulation of hERG may be particularly relevant in cardiac hypertrophy and tumor growth.

A novel dendritic nanocarrier of polyamidoamine-polyethylene glycol-cyclic RGD for "smart" small interfering RNA delivery and in vitro antitumor effects by human ether-à-go-go-related gene silencing in anaplastic thyroid carcinoma cells

The application of RNA interference techniques is promising in gene therapeutic approaches, especially for cancers. To improve safety and efficiency of small interfering RNA (siRNA) delivery, a triblock dendritic nanocarrier, polyamidoamine-polyethylene glycol-cyclic RGD (PAMAM-PEG-cRGD), was developed and studied as an siRNA vector targeting the human ether-à-go-go-related gene (hERG) in human anaplastic thyroid carcinoma cells. Structure characterization, particle size, zeta potential, and gel retardation assay confirmed that complete triblock components were successfully synthesized with effective binding capacity of siRNA in this triblock nanocarrier. Cytotoxicity data indicated that conjugation of PEG significantly alleviated cytotoxicity when compared with unmodified PAMAM. PAMAM-PEG-cRGD exerted potent siRNA cellular internalization in which transfection efficiency measured by flow cytometry was up to 68% when the charge ratio (N/P ratio) was 3.5. Ligand-receptor affinity together with electrostatic interaction should be involved in the nano-siRNA endocytosis mechanism and we then proved that attachment of cRGD enhanced cellular uptake via RGD-integrin recognition. Gene silencing was evaluated by reverse transcription polymerase chain reaction and PAMAM-PEG-cRGD-siRNA complex downregulated the expression of hERG to 26.3% of the control value. Furthermore, gene knockdown of hERG elicited growth suppression as well as activated apoptosis by means of abolishing vascular endothelial growth factor secretion and triggering caspase-3 cascade in anaplastic thyroid carcinoma cells. Our study demonstrates that this novel triblock polymer, PAMAM-PEG-cRGD, exhibits negligible cytotoxicity, effective transfection, “smart” cancer targeting, and therefore is a promising siRNA nanocarrier.

Arsenic trioxide alleviates airway hyperresponsiveness and promotes apoptosis of CD4+ T lymphocytes: evidence for involvement of the ER stress-CHOP pathway

BACKGROUND

Asthma is a chronic inflammatory disorder of the airway. Arsenic trioxide (ATO) is an ancient Chinese medicine, which is used to treat psoriasis, asthma, and acute promyelocytic leukemia.

AIM

We wanted to research the effect of arsenic trioxide on asthma.

METHODS

Using a murine model of asthma, the airway hyperresponsiveness was conducted by the Buxco pulmonary function apparatus. Total cell counts of BALF were counted with a counting chamber. Histopathological analysis of lung tissues was conducted by hematoxylin-eosin or periodic acid-schiff stain. CD4+T cells were purified from the spleen by positive selection, using immunomagnetic beads. Apoptosis measurements were done with Annexin-V/PI staining. Western blot analysis and real time-PCR were performed to assess the expression of C/EBP-homologous protein (CHOP) and glucose-regulated protein 78 (GRP78), respectively. RNA interference was conducted to inhibit the expression of CHOP.

RESULTS

We found that arsenic trioxide treatment alleviated airway hyperresponsiveness and reduced inflammation of the lung in asthmatic mice. Furthermore, arsenic trioxide treatment promoted apoptosis of CD4+T cells in vivo and in vitro. When CD4+T cells were cultured with arsenic trioxide for 5 h at a concentration of 5 μM, the expression of GRP78 and CHOP was increased. Treatment of CD4+T cells with CHOP siRNA, provided partial resistance to arsenic trioxide-induced apoptosis of CD4+T cells

CONCLUSIONS

These data demonstrated that arsenic trioxide can reduce the severity of asthma attacks and induce the apoptosis of CD4+ T cell which the ER stress-CHOP pathway involved.

hERG channel function: beyond long QT

To date, research on the human ether-a-go-go related gene (hERG) has focused on this potassium channel's role in cardiac repolarization and Long QT Syndrome (LQTS). However, growing evidence implicates hERG in a diversity of physiologic and pathological processes. Here we discuss these other functions of hERG, particularly their impact on diseases beyond cardiac arrhythmia.

hERG K+ Channels: Structure, Function, and Clinical Significance

The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.