Chetomin induces apoptosis in human triple-negative breast cancer cells by promoting calcium overload and mitochondrial dysfunction

New Ca2+ based anticancer nanomaterials trigger multiple cell death targeting Ca2+ homeostasis for cancer therapy

Calcium ion (Ca2+) is a necessary element for human and Ca2+ homeostasis plays important roles in various cellular process and functions. Recent reaches have targeted on inducing Ca2+ overload (both intracellular and transcellular) for tumor therapy. With the development of nanotechnology, nanoplatform-mediated Ca2+ overload has been safe theranostic model for cancer therapy, and defined a special calcium overload-induced tumor cell death as "calcicoptosis". However, the underlying mechanism of calcicoptosis in cancer cells remains further identification. In this review, we summarized multiple cell death types due to Ca2+ overload that induced by novel anticancer nanomaterials in tumor cells, including apoptosis, autophagy, pyroptosis, and ferroptosis. We reviewed the roles of these anticancer nanomaterials on Ca2+ homeostasis, including transcellular Ca2+ influx and efflux, and intracellular Ca2+ change in the cytosolic and organelles, and connection of Ca2+ overload with other metal ions. This review provides the knowledge of these nano-anticancer materials-triggered calcicoptosis accompanied with multiple cell death by regulating Ca2+ homeostasis, which could not only enhance their efficiency and specificity, but also enlighten to design new cancer therapeutic strategies and biomedical applications.

Antiproliferation and apoptosis studies of estrone pharmacophores in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that shows high metastatic capability and poor prognosis. The aggressive behavior of TNBC may involve amplified EGFR expression. Currently, no targeted therapy has been approved for treating TNBC, which urgently needs novel treatment options. In this study, we report that estrone analogs with novel pharmacophores exhibited high potency toward TNBC cells through multiple mechanisms, inhibition of cell proliferation via EGFR receptor, and induction of mitochondrial apoptosis. Molecular docking studies revealed that hit analogs MMA307 and MMA321 were potent against the EGFR receptor (pdb code: 1M17) in silico and were over 10-fold more potent than sorafenib (positive control) when dosed against MDA-MB-468 cells in vitro. MMA307 and MMA321 induced mitochondrial apoptosis as characterized by condensed nuclei with fragmented chromatin, phosphatidylserine flip and modulated expressions of Apaf1, cytochrome c, and caspases 3 and 9. MMA307 and MMA321 inhibited TNBC proliferation through suppression of EGFR and activated EGFR (Y1068) expressions. Similarly, EGFR signaling pathways, RAF/ERK and AKT/mTOR, were inhibited as pARaf, pERK1/2 (characterizes RAF/ERK pathway) and pAKT, pmTOR, p70S6Kα (characterizes AKT/mTOR pathway) were all suppressed. Moreover, MMA307 and MMA321 inhibited TNBC cell growth through downregulation of cyclin D1 expression and arresting TNBC cells in the G1 phase of cell cycle. This study reports for the first time that estrone congeners with novel pharmacophores may be an effective therapy for TNBC. Findings from this research provide a solid foundation for further preclinical and clinical studies in developing estrone derivatives as novel TNBC therapeutics.

Chaetocochin J exhibits anti-hepatocellular carcinoma effect independent of hypoxia

The most studied epipolythiodioxopiperazine (ETP) alkaloids, such as chetomin, gliotoxin and chaetocin, were reported to exert their antitumor effects through targeting HIF-1α. Chaetocochin J (CJ) is another ETP alkaloid, of which the effect and mechanism on cancer are not fully elucidated. Considering the high incidence and mortality of hepatocellular carcinoma (HCC) in China, in the present study, using HCC cell lines and tumor-bearing mice as models, we explored the anti-HCC effect and mechanism of CJ. Particularly, we investigated whether HIF-1α is related to the function of CJ. The results showed that, both under normoxic and CoCl2 induced-hypoxic conditions, CJ in low concentrations (<1 µM) inhibits the proliferation, induces G2/M phase arrest, leading to the disorder of metabolism, migration, invasion, and caspase-dependent apoptosis in HepG2 and Hep3B cells. CJ also showed anti-tumor effect on a nude xenograft mice model without significant toxicity. Moreover, we demonstrated that the key to CJ's function is mainly associate with its inhibition of PI3K/Akt/mTOR/p70S6K/4EBP1 pathway independent of hypoxia, and it also could suppress the expression of HIF-1α as well as disrupt the binding of HIF-1α/p300 and subsequently inhibits the expression of its target genes under hypoxic condition. These results demonstrated that CJ possessed a hypoxia-independent anti-HCC effects in vitro and in vivo, which was mainly attributable to its inhibition on the upstream pathways of HIF-1α.

Chemical diversity and biological activities of specialized metabolites from the genus Chaetomium: 2013-2022

Chaetomium (Chaetomiaceae), a large fungal genus consisting of at least 400 species, has been acknowledged as a promising resource for the exploration of novel compounds with potential bioactivities. Over the past decades, emerging chemical and biological investigations have suggested the structural diversity and extensive potent bioactivity of the specialized metabolites in the Chaetomium species. To date, over 500 compounds with diverse chemical types have been isolated and identified from this genus, including azaphilones, cytochalasans, pyrones, alkaloids, diketopiperazines, anthraquinones, polyketides, and steroids. Biological research has indicated that these compounds possess a broad range of bioactivities, including antitumor, anti-inflammatory, antimicrobial, antioxidant, enzyme inhibitory, phytotoxic, and plant growth inhibitory activities. This paper summarizes current knowledge referring to the chemical structure, biological activity, and pharmacologic potency of the specialized metabolites in the Chaetomium species from 2013 to 2022, which might provide insights for the exploration and utilization of bioactive compounds in this genus both in the scientific field and pharmaceutical industry.

Biomonitoring of Indoor Air Fungal or Chemical Toxins with Caenorhabditis elegans nematodes

Bad indoor air quality due to toxins and other impurities can have a negative impact on human well-being, working capacity and health. Therefore, reliable methods to monitor the health risks associated with exposure to hazardous indoor air agents are needed. Here, we have used transgenic Caenorhabditis elegans nematode strains carrying stress-responsive fluorescent reporters and evaluated their ability to sense fungal or chemical toxins, especially those that are present in moisture-damaged buildings. Liquid-based or airborne exposure of nematodes to mycotoxins, chemical agents or damaged building materials reproducibly resulted in time- and dose-dependent fluorescent responses, which could be quantitated by either microscopy or spectrometry. Thus, the C. elegans nematodes present an easy, ethically acceptable and comprehensive in vivo model system to monitor the response of multicellular organisms to indoor air toxicity.

Epipolythiodioxopiperazine-Based Natural Products: Building Blocks, Biosynthesis and Biological Activities

Epipolythiodioxopiperazines (ETPs) are fungal secondary metabolites that share a 2,5-diketopiperazine scaffold built from two amino acids and bridged by a sulfide moiety. Modifications of the core and the amino acid side chains, for example by methylations, acetylations, hydroxylations, prenylations, halogenations, cyclizations, and truncations create the structural diversity of ETPs and contribute to their biological activity. However, the key feature responsible for the bioactivities of ETPs is their sulfide moiety. Over the last years, combinations of genome mining, reverse genetics, metabolomics, biochemistry, and structural biology deciphered principles of ETP production. Sulfurization via glutathione and uncovering of the thiols followed by either oxidation or methylation crystallized as fundamental steps that impact expression of the biosynthesis cluster, toxicity and secretion of the metabolite as well as self-tolerance of the producer. This article showcases structure and activity of prototype ETPs such as gliotoxin and discusses the current knowledge on the biosynthesis routes of these exceptional natural products.

A novel biflavone from Reineckia carnea induces apoptosis of human renal cancer 786-O cells

Renal cell carcinoma (RCC) is a common malignant tumor of the urinary system, which is highly invasive, metastatic, and insensitive to radiotherapy and chemotherapy. Chinese herbal medicine has always been an important source of anti-tumor drug development. Reineckia carnea Kunth is a traditional herb commonly used by the Miao nationality in southwest China. In this study, the extract of Reineckia carnea was isolated and purified by reverse phase preparative chromatography and other chromatographic techniques. According to the physicochemical properties and spectral data, the structure of the compound was identified, and a novel biflavone compound named Reineckia-biflavone A (RFA) was obtained. The result of antiproliferative activity showed that RFA had cytotoxicity on 786-O cells with an IC50 value of 19.34 μmol/L. The results of CCK-8 and hemolysis assays showed that RFA was not significantly cytotoxic to both red blood cells (RBC) and peripheral blood mononuclear cells (PBMC). By Hoechst 33258 apoptosis staining, typical apoptotic morphology was observed under fluorescence microscope. RFA could induce the apoptosis of 786-O cells with the increase of apoptosis rate. The cell cycle tests showed that the cell proportion was obviously arrested in the S phase. At the same time, RFA could decrease the mitochondrial membrane potential and increase the intracellular free Ca2+ concentration. Western blot showed that the expression levels of pro-apoptotic proteins (Bax, Caspase-3, Cleaved Caspase-3, and Cytochrome c) in cells rose, while the expression level of anti-apoptotic proteins (Bcl-2) declined significantly. In conclusion, this study suggests that the RFA is a new biflavone determined by SciFinder retrieval. The apoptosis may be triggered by RFA through the mitochondrial pathway, which is mediated by up-regulating the intracellular calcium ion, down-regulating the mitochondrial membrane potential, and changing the apoptosis-related proteins.

Naturally derived indole alkaloids targeting regulated cell death (RCD) for cancer therapy: from molecular mechanisms to potential therapeutic targets

Regulated cell death (RCD) is a critical and active process that is controlled by specific signal transduction pathways and can be regulated by genetic signals or drug interventions. Meanwhile, RCD is closely related to the occurrence and therapy of multiple human cancers. Generally, RCD subroutines are the key signals of tumorigenesis, which are contributed to our better understanding of cancer pathogenesis and therapeutics. Indole alkaloids derived from natural sources are well defined for their outstanding biological and pharmacological properties, like vincristine, vinblastine, staurosporine, indirubin, and 3,3′-diindolylmethane, which are currently used in the clinic or under clinical assessment. Moreover, such compounds play a significant role in discovering novel anticancer agents. Thus, here we systemically summarized recent advances in indole alkaloids as anticancer agents by targeting different RCD subroutines, including the classical apoptosis and autophagic cell death signaling pathways as well as the crucial signaling pathways of other RCD subroutines, such as ferroptosis, mitotic catastrophe, necroptosis, and anoikis, in cancer. Moreover, we further discussed the cross talk between different RCD subroutines mediated by indole alkaloids and the combined strategies of multiple agents (e.g., 3,10-dibromofascaplysin combined with olaparib) to exhibit therapeutic potential against various cancers by regulating RCD subroutines. In short, the information provided in this review on the regulation of cell death by indole alkaloids against different targets is expected to be beneficial for the design of novel molecules with greater targeting and biological properties, thereby facilitating the development of new strategies for cancer therapy.

A Review on Bioactive Compounds from Marine-Derived Chaetomium Species

Filamentous marine fungi have proven to be a plentiful source of new natural products. Chaetomium, a widely distributed fungal genus in the marine environment, has gained much interest within the scientific community. In the last 20 years, many potential secondary metabolites have been detected from marine-derived Chaetomium. In this review, we attempt to provide a comprehensive summary of the natural products produced by marine-derived Chaetomium species. A total of 122 secondary metabolites that were described from 2001 to 2021 are covered. The structural diversity of the compounds, along with details of the sources and relevant biological properties are also provided, while the relationships between structures and their bioactivities are discussed. It is our expectation that this review will be of benefit to drug development and innovation.

DSTYK Enhances Chemoresistance in Triple-Negative Breast Cancer Cells

Breast cancer, as the most prevalent cancer in women, is responsible for more than 15% of new cancer cases and about 6.9% of all cancer-related death in the US. A major cause of therapeutic failure in breast cancer is the development of resistance to chemotherapy, especially for triple-negative breast cancer (TNBC). Therefore, how to overcome chemoresistance is the major challenge to improve the life expectancy of breast cancer patients. Our studies demonstrate that TNBC cells surviving the chronic treatment of chemotherapeutic drugs show significantly higher expression of the dual serine/threonine and tyrosine protein kinase (DSTYK) than non-treated parental cells. In our in vitro cellular models, DSTYK knockout via the CRISPR/Cas9-mediated technique results in apoptotic cell death of chemoresistant cells upon drug treatment. Moreover, DSTYK knockout promotes chemotherapeutic drug-induced tumor cell death in an orthotopic mouse model. These findings suggest that DSTYK exerts an important and previously unknown role in promoting chemoresistance. Our studies provide fundamental insight into the role of DSTYK in chemoresistance in TNBC cells and lay the foundation for the development of new strategies targeting DSTYK for improving TNBC therapy.

Neochlorogenic acid anchors MCU-based calcium overload for cancer therapy

Cancer is a major threat to human health worldwide, yet the clinical therapies remain unsatisfactory. In this study, we found that a Tetrastigma hemsleyanum leaves flavone (TLF) intervention could achieve tumor inhibition. Besides, neochlorogenic acid (NA), which had the highest absorbance peak in the HPLC profile of TLF, showed superior anti-proliferation ability over TLF, and could effectively trigger apoptosis, restrain migration, and facilitate cytoskeleton collapse, suggesting its key role in TLF's anticancer property. Molecular docking analysis suggested that NA was capable of binding with mitochondrial Ca²⁺ uniporter (MCU), and further experiments confirmed that NA upregulated the MCU level to permit excess calcium ion influx, leading to mitochondrial calcium imbalance, dysfunction, structure alteration, and ROS elevation. Moreover, tumor-bearing mice were applied to further confirm the excellent tumor inhibition ability of NA under Ca²⁺-abundant conditions. Therefore, this study uncovered that NA could effectively trigger robust MCU-mediated calcium overload cancer therapy, which could be utilized in novel strategies for future cancer treatment.

Development of a High-throughput NanoBRET Screening Platform to Identify Modulators of the RAS/RAF Interaction

Activating mutations in RAS are found in approximately 30% of human cancers, resulting in the delivery of a persistent signal to critical downstream effectors that drive tumorigenesis. RAS-driven malignancies respond poorly to conventional cancer treatments and inhibitors that target RAS directly are limited; therefore, the identification of new strategies and/or drugs to disrupt RAS signaling in tumor cells remains a pressing therapeutic need. Taking advantage of the live-cell bioluminescence resonance energy transfer (BRET) methodology, we describe the development of a NanoBRET screening platform to identify compounds that modulate binding between activated KRAS and the CRAF kinase, an essential effector of RAS that initiates ERK cascade signaling. Using this strategy, libraries containing synthetic compounds, targeted inhibitors, purified natural products, and natural product extracts were evaluated. These efforts resulted in the identification of compounds that inhibit RAS/RAF binding and in turn suppress RAS-driven ERK activation, but also compounds that have the deleterious effect of enhancing the interaction to upregulate pathway signaling. Among the inhibitor hits identified, the majority were compounds derived from natural products, including ones reported to alter KRAS nanoclustering (ophiobolin A), to impact RAF function (HSP90 inhibitors and ROS inducers) as well as some with unknown targets and activities. These findings demonstrate the potential for this screening platform in natural product drug discovery and in the development of new therapeutic agents to target dysregulated RAS signaling in human disease states such as cancer.

Piperine and Celecoxib synergistically inhibit colon cancer cell proliferation via modulating Wnt/β-catenin signaling pathway

BACKGROUND

Celecoxib (CXB), a selective COX-2 inhibitor NSAID, has exhibited prominent anti-proliferative potential against numerous cancers. However, its low bioavailability and long term exposure related cardiovascular side effects, limit its clinical application. In order to overcome these limitations, natural bioactive compounds with lower toxicity profile are used in combination with therapeutic drugs. Therfore, in this study Piperine (PIP), a natural chemo-preventive agent possessing drug bioavailability enhancing properties, was considered to be used in combination with low doses of CXB.

PURPOSE

We hypothesized that the combination of PIP with CXB will have a synergistic anti-proliferative effect on colon cancer cells.

STUDY DESIGN

The potency of PIP and CXB alone and in combination was evaluated in HT-29 human colon adenocarcinoma cells and mechanism of growth inhibition was investigated by analyzing the players in apoptotic and Wnt/β-catenin signaling pathways.

METHODS

The effect of PIP on the oral bioavailability of CXB in mice was investigated using HPLC analysis. The study investigated the synergistic anti-proliferative effect of CXB and PIP on HT-29 cells and IEC-6 non-tumorigenic rat intestinal epithelial cells by SRB cell viability assay. Further, the cellular and molecular mechanism(s) involved in the anti-proliferative combinatorial effect was extensively explored in HT-29 cells by flow cytometry and western blotting. The in vivo efficacy of this combination was studied in CT26.WT tumor syngeneic Balb/c mice model.

RESULTS

PIP as a bioenhancer increased the oral bioavailability of CXB (129%). The IC50 of CXB and PIP were evaluated to select doses for combination treatment of HT-29 cells. The drug combinations having combination index (CI) less than 1 were screened using CompuSyn software. These combinations were significantly cytotoxic to HT-29 cells but IEC-6 were least effected. Further, the mechanism behind CXB and PIP mediated cell death was explored. The co-treatment led to reactive oxygen species generation, mitochondrial dysfunction, caspase activation and enhanced apoptosis in HT-29 cells. Additionally, the combination treatment synergistically modulated Wnt/β-catenin pathway, downregulated the stemness markers and boosted therapeutic response in CT26 syngeneic Balb/c mice.

CONCLUSION

The outcomes of the study suggests that combining CXB and PIP offers a novel approach for the treatment of colon cancer.

A novel strategy for tumor therapy: targeted, PAA-functionalized nano-hydroxyapatite nanomedicine

The rapid development of nanotechnology has provided new strategies for the treatment of tumors. Nano-scale hydroxyapatite (HAP), as the main component of hard tissues in humans and vertebrates, have been found to specifically inhibit tumor cells. However, achieving controllable synthesis of HAP and endowing it with cancer cell-targeting properties remain enormous challenges. To solve this problem, we developed polyacrylic acid-coordinated hydroxyapatite nanoparticles (HAP-PAA) and further chemically grafted them with folic acid (HAP-PAA-FA) for cancer treatment in this study. The nucleation sites and steric hindrance provided by the PAA greatly inhibited the agglomeration of the nanoparticles, and at the same time, the excess functional groups further modified the surface of nanoparticles to achieve targeting efficiency. The spherical, low-crystallinity HAP-PAA nanoparticles exhibited good tumor cell lethality. After grafting the nanoparticles with folic acid for molecular targeting, their cellular uptake and specific killing ability of tumor cells were further enhanced. The HAP-PAA-FA nanoparticle system exerted a regulatory effect on the tumor microenvironment and had good biological safety. All the above results indicate that this research will broaden the application of hydroxyapatite in tumor treatment.

n→π* Interactions Modulate the Disulfide Reduction Potential of Epidithiodiketopiperazines

Epithiodiketopiperazines (ETPs) are a structurally complex class of fungal natural products with potent anticancer activity. In ETPs, the diketopiperazine ring is spanned by a disulfide bond that is constrained in a high-energy eclipsed conformation. We employed computational, synthetic, and spectroscopic methods to investigate the physicochemical attributes of this atypical disulfide bond. We find that the disulfide bond is stabilized by two n→π* interactions, each with large energies (3-5 kcal/mol). The n→π* interactions in ETPs make disulfide reduction much more difficult, endowing stability in physiological environments in a manner that could impact their biological activity. These data reveal a previously unappreciated means to stabilize a disulfide bond and highlight the utility of the n→π* interaction in molecular design.

Detection of Chaetomium globosum, Ch. cochliodes and Ch. rectangulare during the Diversity Tracking of Mycotoxin-Producing Chaetomium-Like Isolates Obtained in Buildings in Finland

The diversity of Chaetomium-like isolates in buildings in Finland is poorly documented. This paper describes a set of methods for rapid diversity tracking of 42 indoor Chaetomium-like isolates. These isolates were categorized based on their fluorescence emission, ascomatal hair morphology, responses in three bioassays and resistance/sensitivity to the wetting agent Genapol X-080. Thirty-nine toxigenic isolates were identified [Ch. globosum (n = 35), Ch. cochliodes (n = 2) and Ch. rectangulare (n = 2)]. These isolates were identified down to the species level by tef1α gene sequencing. The major toxic substances in the ethanol extracts of the Ch. globosum and Ch. cochliodes strains were chaetoglobosin, chaetoviridin A and C, chaetomugilin D and chaetomin, identified based on HPLC-UV and mass spectrometry data (MS and MS/MS). Ethanol extracts from pure Ch. globosum cultures exhibited a toxicological profile in the boar sperm motility inhibition assay (BSMI), sperm membrane integrity damage assay (SMID) and inhibition of cell proliferation (ICP) assay, similar to that exhibited by pure chaetoglobosin A. Overall, differences in fluorescence, morphology, toxicity profile, mycotoxin production and sensitivity to chemicals were consistent with those in tef1α sequencing results for species identification. The results indicate the presence of Ch. cochliodes and Ch. rectangulare in Finnish buildings, representing a new finding.

Chetomin, a Hsp90/HIF1α pathway inhibitor, effectively targets lung cancer stem cells and non-stem cells

Non-small cell lung cancer (NSCLC) remains recalcitrant to effective treatment due to tumor relapse and acquired resistance. Cancer stem cells (CSCs) are believed to be one mechanism for relapse and resistance and are consequently considered promising drug targets. We report that chetomin, an active component of Chaetomium globosum, blocks heat shock protein 90/hypoxia-inducible factor 1 alpha (Hsp90/HIF1α) pathway activity. Chetomin also attenuated sphere-forming, a stem cell-like characteristic, of NSCLC CSCs (at ~ nM range) and the proliferation of non-CSCs NSCLC cultures and chemoresistant sublines (at ~ μM range). At these concentrations, chetomin exerted a marginal influence on noncancerous cells originating from several organs. Chetomin markedly decreased in vivo tumor formation in a spontaneous Kras ^LA1 lung cancer model, flank xenograft models, and a tumor propagation flank implanted model at doses that did not produce an observable toxicity to the animals. Chetomin blocked Hsp90/HIF1α pathway activity via inhibiting the Hsp90-HIF1α binding interaction without affecting Hsp90 or Hsp70 protein levels. This study advocates chetomin as a Hsp90/HIF1α pathway inhibitor and a potent, nontoxic NSCLC CSC-targeting molecule.

Synthesis of Potent Cytotoxic Epidithiodiketopiperazines Designed for Derivatization

We describe our design, synthesis, and chemical study of a set of functional epidithiodiketopiperazines (ETPs) and evaluation of their activity against five human cancer cell lines. Our structure-activity relationship-guided substitution of ETP alkaloids offers versatile derivatization while maintaining potent anticancer activity, offering exciting opportunity for their use as there are no examples of complex and potently anticancer (nM) ETPs being directly used as conjugatable probes or warheads. Our synthetic solutions to strategically designed ETPs with functional linkers required advances in stereoselective late-stage oxidation and thiolation chemistry in complex settings, including the application of novel reagents for dihydroxylation and cis-sulfidation of diketopiperazines. We demonstrate that complex ETPs equipped with a strategically substituted azide functional group are readily derivatized to the corresponding ETP-triazoles without compromising anticancer activity. Our chemical stability studies of ETPs along with cytotoxic evaluation of our designed ETPs against A549, DU 145, HeLa, HCT 116, and MCF7 human cancer cell lines provide insights into the impact of structural features on potency and chemical stability, informing future utility of ETPs in chemical and biological studies.

Double the Chemistry, Double the Fun: Structural Diversity and Biological Activity of Marine-Derived Diketopiperazine Dimers

While several marine natural products bearing the 2,5-diketopiperazine ring have been reported to date, the unique chemistry of dimeric frameworks appears to remain neglected. Frequently reported from marine-derived strains of fungi, many naturally occurring diketopiperazine dimers have been shown to display a wide spectrum of pharmacological properties, particularly within the field of cancer and antimicrobial therapy. While their structures illustrate the unmatched power of marine biosynthetic machinery, often exhibiting unsymmetrical connections with rare linkage frameworks, enhanced binding ability to a variety of pharmacologically relevant receptors has been also witnessed. The existence of a bifunctional linker to anchor two substrates, resulting in a higher concentration of pharmacophores in proximity to recognition sites of several receptors involved in human diseases, portrays this group of metabolites as privileged lead structures for advanced pre-clinical and clinical studies. Despite the structural novelty of various marine diketopiperazine dimers and their relevant bioactive properties in several models of disease, to our knowledge, this attractive subclass of compounds is reviewed here for the first time.

Safety assessment of the pharmacological excipient, diethylene glycol monoethyl ether (DEGEE), using in vitro and in vivo systems

BACKGROUND

Diethylene glycol monoethyl ether (DEGEE) is widely used as a solubilizer in cosmetics as well as in oral, topical, transdermal and injectable pharmaceutical formulations. Due to the unavailability of detailed toxicological studies on DEGEE, the Scientific Committee on Consumer Products (SCCP) found its toxicological reports to be unsatisfactory, comprising only summaries. Also, a few reports have raised concern on the use of DEGEE as it might cause damage to the kidneys.

OBJECTIVE

Safety assessment of DEGEE using in vitro and in vivo models.

METHODS

In vitro effects of DEGEE (0.5-25 mg/ml) were assessed in the HEK293 human embryonic kidney cells. In vivo effects were evaluated after single acute exposure of DEGEE via intraperitoneal route in Swiss albino mice and further, a 28 days subchronic exposure study was conducted where DEGEE was administered orally, once daily.

RESULTS

DEGEE was cytotoxic to HEK293 cells, and an IC50 of 15 mg/ml was established. An increase in the intracellular levels of ROS and alteration in the mitochondrial membrane potential led to nuclear fragmentation and induction of apoptosis in these cells. Survival rate of animals administered intraperitoneally with a single acute dose of 1000 mg/kg DEGEE was 100% with no significant changes in the behavioural and histological parameters. However, the dose of 3000 mg/kg and above led to total mortality within 14 days of acute exposure. Subchronic oral exposure of 500-2000 mg/kg DEGEE showed no significant changes in the hematological, biochemical and histopathological parameters.

CONCLUSIONS

The in vitro findings indicate that the nephrotoxic potential of DEGEE cannot be ruled out. The results of the in vivo studies reveal that the degree of toxic effects shown by DEGEE varies, depending on the dose, duration of exposure and routes of administration. Therefore, the present findings are of relevance and thorough studies should be conducted before using this substance in clinical formulations. Graphical abstract Evaluation of the toxic potential of Diethylene glycol monoethyl ether.

Salinomycin inhibits breast cancer progression via targeting HIF-1α/VEGF mediated tumor angiogenesis in vitro and in vivo

Cancer is a complex disease wherein cells begin to divideabnormally and spread into surrounding tissues. Angiogenesis plays a crucial role in tumor progression as it is required for sustained growth and metastasis, therefore targeting angiogenesis is a promising therapeutic approach for breast cancer management. Salinomycin (SAL) has been reported to exhibit anticancer response on various types of cancer. In the present study, we explored the antiangiogenic and anticancer efficacy of the polyether ionophore SAL in the breast cancer model. It effectively inhibited cell proliferation, invasion, and migration. It also inhibited the expression of pro-angiogenic cell surface marker CD31 in HUVEC, thereby interrupting the endothelial tubulogenesis. It decreased the HIF-1α transcription factor DNA binding activity to HRE sequence in HUVEC and human breast cancer cells. Further, corresponding to our in vitro findings, SAL suppressed neovascularization in the chick chorioallantoic membrane and the Matrigel plug implanted mice model. Bioluminescence and immunofluorescence imaging revealed that SAL treatment in mice inhibits breast cancer growth and tumor angiogenesis. SAL also suppressed the serum VEGFA level in tumor-bearing mice and induced caspase-dependent apoptosis in breast cancer cells. Taken together our findings suggested that SAL inhibits VEGF induced angiogenesis and breast cancer growth via interrupting HIF-1α/VEGF signalling and could be used as a promising antiangiogenic agent for breast cancer treatment.