Novel Anthraquinone Compounds Induce Cancer Cell Death through Paraptosis

Cytoplasmic Vacuolization: A Fascinating Morphological Alteration From Cellular Stress to Cell Death

Cytoplasmic vacuolization is a cellular morphological alteration characterized by the presence of substantial vacuole-like structures originating from various cellular organelles. This phenomenon is often observed in various anticancer treatments, including chemotherapeutic drugs, and photodynamic therapy (PDT), and is frequently linked with cell death. Nevertheless, the precise mechanisms underlying cytoplasmic vacuolization and ensuing cell death remain ambiguous. Cytoplasmic vacuolization associated cell death (CVACD) is a complex process characterized by cellular stress, encompassing ER stress, heightened membrane permeability, ion imbalance, and mitochondrial dysfunction. The MAPK signaling pathway is closely associated with the activation of CVACD. This review provides a thorough examination of contemporary studies on cytoplasmic vacuolization in mammalian cells, elucidating its etiology, origins, and molecular pathways. Additionally, it highlights the potential of CVACD as an innovative therapeutic strategy for cancer.

Rhein: An Updated Review Concerning Its Biological Activity, Pharmacokinetics, Structure Optimization, and Future Pharmaceutical Applications

Rhein is a natural active ingredient in traditional Chinese medicine that has attracted much attention due to its wide range of pharmacological activities. However, its clinical application is limited by low water solubility, poor oral absorption, and potential toxicity to the liver and kidneys. Recently, advanced extraction and synthesis techniques have made it possible to develop derivatives of rhein, which have better pharmacological properties and lower toxicity. This article comprehensively summarizes the biological activity and action mechanism of rhein. Notably, we found that TGF-β1 is the target of rhein improving tissue fibrosis, while NF-κB is the main target of its anti-inflammatory effect. Additionally, we reviewed the current research status of the pharmacokinetics, toxicology, structural optimization, and potential drug applications of rhein and found that the coupling and combination therapy of rhein and other active ingredients exhibit a synergistic effect, significantly enhancing therapeutic efficacy. Finally, we emphasize the necessity of further studying rhein's pharmacological mechanisms, toxicology, and development of analogs, aiming to lay the foundation for its widespread clinical application as a natural product and elucidate its prospects in modern medicine.

Discovery and optimization of anthraquinone derivatives containing substituted bisbenzyloxy groups as a novel scaffold damaged endoplasmic reticulum and against hepatocellular carcinoma cells

This paper reports the antitumor activity and possible mechanism of anthraquinone derivatives containing substituted bisbenzyloxy groups. Series of anthraquinone derivatives containing substituted bisbenzyloxy groups were designed and synthesized by etherification and esterification. The antitumor activities of the synthesized substituted bisbenzyloxy anthraquinone derivatives on liver cancer cell Huh7, triple negative breast cancer cell line MDA-MB-231 and lung cancer cell A549 were in the order of methoxy substitution > methyl substitution > chloral substitution. Among these, the Compound KA-MO-g showed strong antitumor activity, especially against liver cancer Huh7 cells. Further studies on the antitumor mechanism showed that the Compound KA-MO-g simultaneously activated three pathways of endoplasmic reticulum stress (ERS), also caused impairment of endoplasmic reticulum (ER) functions, such as glycoprotein synthesis and disulfide bond formation are impeded and caused calcium overload, then increased mitochondrial ROS, damaged of mitochondria, changed of apoptosis-related protein levels, activated Caspase 3, induced the apoptosis of Huh7 cells. Because KA-MO-g showed strong antitumor activity, it is expected to be a new candidate drug for treating liver cancer and is worth further study.

9,10-Dioxoanthracenyldithiocarbamates effectively inhibit the proliferation of non-small cell lung cancer by targeting multiple protein tyrosine kinases

Anthraquinones have attracted considerable interest in the realm of cancer treatment owing to their potent anticancer properties. This study evaluates the potential of a series of new anthraquinone derivatives as anticancer agents for non-small-cell lung cancer (NSCLC). The compounds were subjected to a range of tests to assess their cytotoxic and apoptotic properties, ability to inhibit colony formation, pro-DNA damage functions, and capacity to inhibit the activity of tyrosine kinase proteins (PTKs). Based on the research findings, it has been discovered that most active derivatives (i84, i87, and i90) possess a substantial capability to impede the viability of NSCLC while having mostly a negligible effect on the human kidney cell line. Moreover, the anthraquinones displayed pro-apoptotic and genotoxic attributes while blocking the phosphorylation of multiple PTKs. Collectively, our findings indicate that these derivatives may demonstrate promising potential as effective anticancer agents for lung cancer treatment.

Compound 4a induces paraptosis in liver cancer through endoplasmic reticulum stress mediated by the calreticulin protein

BACKGROUND AND PURPOSE

Emerging evidence has highlighted that paraptosis may be an effective strategy for treating liver cancer. In our previous studies, Compound 4a induced paraptosis in cancer cells. Here, the characteristics of Compound 4a-induced paraptosis were further revealed and, for the first time, the target and related molecular mechanisms of Compound 4a-induced paraptosis in liver cancer were defined.

EXPERIMENTAL APPROACH

The effects and mechanism of Compound 4a in liver cancer cells were studied in in vitro and in vivo (BALB/c-nude xenograft model) experiments, and the targets of Compound 4a that trigger paraptosis were identified and confirmed via mass spectrometry-based drug affinity responsive target stability (DARTS) analyses, siRNA experiments and a cellular thermal shift assay (CETSA). The function and distribution of calreticulin (CRT) protein were detected via Cal-520 AM and immunofluorescence staining, respectively.

KEY RESULTS

Compound 4a effectively induced paraptosis-like cell death in liver cancer, both in vitro and in vivo, and its effect was comparable with the first-line anti-liver cancer drug oxaliplatin but with a higher safety profile. We identified the CRT protein as a target of Compound 4a, which caused cellular endoplasmic reticulum stress (ERS) and calcium overload. CRT knockdown weakened the anti-liver cancer activity of Compound 4a, which may be related to the inhibition of paraptosis.

CONCLUSION

Compound 4a represents a potentially safe and effective agent for the treatment of liver cancer. The characteristics of Compound 4a-triggered paraptosis was clarified and a unique function of CRT in paraptosis was revealed.

Exploring paraptosis as a therapeutic approach in cancer treatment

A variety of cell death pathways play critical roles in the onset and progression of multiple diseases. Paraptosis, a unique form of programmed cell death, has gained significant attention in recent years. Unlike apoptosis and necrosis, paraptosis is characterized by cytoplasmic vacuolization, swelling of the endoplasmic reticulum and mitochondria, and the absence of caspase activation. Numerous natural products, synthetic compounds, and newly launched nanomedicines have been demonstrated to prime cell death through the paraptotic program and may offer novel therapeutic strategies for cancer treatment. This review summarizes recent findings, delineates the intricate network of signaling pathways underlying paraptosis, and discusses the potential therapeutic implications of targeting paraptosis in cancer treatment. The aim of this review is to expand our understanding of this unique cell death process and explore the potential therapeutic implications of targeting paraptosis in cancer treatment.

Activation of autophagy, paraptosis, and ferroptosis by micheliolide through modulation of the MAPK signaling pathway in pancreatic and colon tumor cells

Micheliolide (MCL), a naturally occurring sesquiterpene lactone, has demonstrated significant anticancer properties through the induction of various programmed cell death mechanisms. This study aimed to explore MCL's effects on autophagy, paraptosis, and ferroptosis in pancreatic and colon cancer cells, along with its modulation of the MAPK signaling pathway. MCL was found to substantially suppress cell viability in these cancer cells, particularly in MIA PaCa-2 and HT-29 cell lines. The study identified that MCL induced autophagy by enhancing the levels of autophagy markers such as Atg7, p-Beclin-1, and Beclin-1, which was attenuated by the autophagy inhibitor 3-MA. Furthermore, MCL was found to facilitate paraptosis, indicated by decreased Alix and in-creased ATF4 and CHOP levels. It also promoted ferroptosis, as demonstrated by the reduced expression of SLC7A11, elevated TFRC levels, and increased intracellular iron. Additionally, MCL activated the MAPK signaling pathway, marked by the phosphorylation of JNK, p38, and ERK, linked with an increase in ROS production that is vital in regulating these cell death mechanisms. These findings propose that MCL is a versatile anticancer agent, capable of activating various cell death pathways by modulating MAPK signaling and ROS levels. These results emphasize the therapeutic promise of MCL in treating cancer, pointing to the necessity of further in vivo investigations to confirm these effects and determine its potential clinical uses.

A multi-mode Rhein-based nano-platform synergizing ferrotherapy/chemotherapy-induced immunotherapy for enhanced tumor therapy

Ferroptosis has emerged as a promising strategy for treating triple-negative breast cancer (TNBC) due to bypassing apoptosis and triggering immunogenic cell death (ICD) of tumor cells. However, the antitumor efficacy has been limited by the insufficient intracellular ferrous iron concentration required for ferroptosis and inadequate antitumor immune response. To address these limitations, we designed a multi-mode nano-platform (MP-FA@R-F NPs), which exhibited a synergistic effect of ferroptosis, apoptosis and induced immune response for enhanced antitumor therapy. MP-FA@R-F NPs target folate receptors, which are over-expressed on the tumor cell's surface to promote intracellular uptake. The cargoes, including Rhein and Fe3O4, would be released in intracellular acid, accelerating by NIR laser irradiation. The released Rhein induced apoptosis of tumor cells mediated by the caspase 3 signal pathway, while the released Fe3O4 triggered ferroptosis through the Fenton reaction and endowed the nanoplatform with magnetic resonance imaging (MRI) capabilities. In addition, ferroptosis-dying tumor cells could release damage-associated molecular patterns (DAMPs) to promote T cell activation and infiltration for immune response and induce immunogenic cell death (ICD) for tumor immunotherapy. Together, MP-FA@R-F NPs represent a potential synergistic ferro-/chemo-/immuno-therapy strategy with MRI guidance for enhanced antitumor therapy. STATEMENT OF SIGNIFICANCE: The massive strategies of cancer therapy based on ferroptosis have been emerging in recent years, which provided new insights into designing materials for cancer therapy. However, the antitumor efficacy of ferroptosis is still unsatisfactory, mainly due to insufficient intracellular pro-ferroptotic stimuli. In the current study, we designed a multi-mode nano-platform (MP-FA@R-F NPs), which represented a potential synergistic ferro-/chemo-/immuno-therapy strategy with MRI guidance for enhanced antitumor therapy.

Targeting paraptosis in cancer: opportunities and challenges

Cell death can be classified into two primary categories: accidental cell death and regulated cell death (RCD). Within RCD, there are distinct apoptotic and non-apoptotic cell death pathways. Among the various forms of non-apoptotic RCD, paraptosis stands out as a unique mechanism characterized by distinct morphological changes within cells. These alterations encompass cytoplasmic vacuolization, organelle swelling, notably in the endoplasmic reticulum and mitochondria, and the absence of typical apoptotic features, such as cell shrinkage and DNA fragmentation. Biochemically, paraptosis distinguishes itself by its independence from caspases, which are conventionally associated with apoptotic death. This intriguing cell death pathway can be initiated by various cellular stressors, including oxidative stress, protein misfolding, and specific chemical compounds. Dysregulated paraptosis plays a pivotal role in several critical cancer-related processes, such as autophagic degradation, drug resistance, and angiogenesis. This review provides a comprehensive overview of recent advancements in our understanding of the mechanisms and regulation of paraptosis. Additionally, it delves into the potential of paraptosis-related compounds for targeted cancer treatment, with the aim of enhancing treatment efficacy while minimizing harm to healthy cells.

Synthesis, characterization and discovery of multiple anticancer mechanisms of dibutyltin complexes based on salen-like ligands

A series of novel dibutyltin complexes based on salen-like ligands (S01-S03) were synthesized and characterized using ultraviolet-visible spectra，infrared spectra, 1H, 13C, and 119Sn nuclear magnetic resonance, high-resolution mass spectrometry, X-ray crystallography, and thermogravimetric analysis. Complex S03 had excellent anticancer activity in vitro (IC50 = 1.5 ± 0.2 μM in CAL-27 cell lines), which highly activated ROS expression levels and induced apoptosis and cell cycle arrest at the G2/M phase. Interestingly, complex S03 induced cancer cell death through multiple mechanisms (mitochondrial pathway, ER-stress pathway, and DNA damage pathway). This study reveals new mechanisms of organotin complexes and provides new insights into the development of organotin metal complexes as anticancer drugs in the future, and compounds with multiple anticancer mechanisms may be a new strategy for delaying or overcoming drug resistance to chemotherapy and target therapy.

Ferritinophagy-mediated apoptosis and paraptosis induction involved MAPK and PI3K/AKT pathway in mechanism of an iron chelator

Melanoma cells were more resistant to ferroptosis with still poor therapy outcomes. Sensitizing melanoma cell to the ferroptosis inducer was a crucial strategy for treatment of melanoma. In the present study, 2,2'-di-pyridylketone hydrazone dithiocarbamate s-butyric acid (DpdtbA) displayed superior inhibitory activity than ferroptosis inducer Erastin in melanoma cells, which prompt us to explore the underlying mechanism. The analyses from flow cytometry and Western blot showed that the growth inhibition of DpdtbA against SK-MEL-28 and A375 cells involved apoptosis induction and G1 phase arrest. Surprisingly, the cytoplasmic vacuoles were found upon the treatment; transmission electron microscopy and endoplasmic reticulum (ER) staining revealed that the cytoplasmic vacuoles were in ER; while down-regulation of alix and requirement of protein synthesis suggested there was an occurrence of paraptosis. However, both NAC and 3-MA could significantly attenuate the cytoplasmic vacuolization and growth inhibition, hinting that both ROS and autophagy involved the paraptosis induction. The additional evidence revealed that there was an occurrence of continuous ferritinophagy, which was responsible for the ROS production. Downregulation of NCOA4 clearly attenuated the apoptosis and paraptosis induction. In addition, activation of MAPK involved regulation of paraptosis, but only ERK and JNK had role in the formation of cytoplasmic vacuoles and growth inhibition. Furthermore, a ROS dependent regulation of PI3K/AKT pathway was also involved. Taken together, our result firstly demonstrated that a continuous ferritinophagy contributed to the apoptosis and paraptosis induction, highlighting that the lysosomal labile iron pool had a crucial role in control of melanoma cell fate.

Therapeutic Potential of 1,8-Dihydroanthraquinone Derivatives for Breast Cancer

Breast cancer (BC) is the most common malignancy among women worldwide. In recent years, significant progress has been made in BC therapy. However, serious side effects resulting from the use of standard chemotherapeutic drugs, as well as the phenomenon of multidrug resistance (MDR), limit the effectiveness of approved therapies. Advanced research in the BC area is necessary to create more effective and safer forms of therapy to improve the outlook for individuals diagnosed with this aggressive neoplasm. For decades, plants and natural products with anticancer properties have been successfully utilized in treating various medical conditions. Anthraquinone derivatives are tricyclic secondary metabolites of natural origin that have been identified in plants, lichens, and fungi. They represent a few botanical families, e.g., Rhamnaceae, Rubiaceae, Fabaceae, Polygonaceae, and others. The review comprehensively covers and analyzes the most recent advances in the anticancer activity of 1,8-dihydroanthraquinone derivatives (emodin, aloe-emodin, hypericin, chrysophanol, rhein, and physcion) applied both individually, or in combination with other chemotherapeutic agents, in in vitro and in vivo BC models. The application of nanoparticles for in vitro and in vivo evidence in the context of 1,8-dihydroanthraquinone derivatives was also described.

Targeting GDP-Dissociation Inhibitor Beta (GDI2) with a Benzo[a]quinolizidine Library to Induce Paraptosis for Cancer Therapy

Inducing paraptosis, a nonapoptotic form of cell death, has great therapeutic potential in cancer therapy, especially for drug-resistant tumors. However, the specific molecular target(s) that trigger paraptosis have not yet been deciphered yet. Herein, by using activity-based protein profiling, we identified the GDP-dissociation inhibitor beta (GDI2) as a manipulable target for inducing paraptosis and uncovered benzo[a]quinolizidine BQZ-485 as a potent inhibitor of GDI2 through the interaction with Tyr245. Comprehensive target validation revealed that BQZ-485 disrupts the intrinsic GDI2-Rab1A interaction, thereby abolishing vesicular transport from the endoplasmic reticulum (ER) to the Golgi apparatus and initiating subsequent paraptosis events including ER dilation and fusion, ER stress, the unfolded protein response, and cytoplasmic vacuolization. Based on the structure of BQZ-485, we created a small benzo[a]quinolizidine library by click chemistry and discovered more potent GDI2 inhibitors using a NanoLuc-based screening platform. Leveraging the engagement of BQZ-485 with GDI2, we developed a selective GDI2 degrader. The optimized inhibitor (+)-37 and degrader 21 described in this study exhibited excellent in vivo antitumor activity in two GDI2-overexpressing pancreatic xenograft models, including an AsPc-1 solid tumor model and a transplanted human PDAC tumor model. Altogether, our findings provide a promising strategy for targeting GDI2 for paraptosis in the treatment of pancreatic cancers, and these lead compounds could be further optimized to be effective chemotherapeutics.

A Native Drug-Free Macromolecular Therapeutic to Trigger Mutual Reinforcing of Endoplasmic Reticulum Stress and Mitochondrial Dysfunction for Cancer Treatment

Drug-free macromolecular therapeutics are promising alternatives to traditional drugs. Nanomedicines with multiple organelles targeting can potentially increase the efficacy. Herein, a drug-free macromolecular therapeutic was designed to formulate endoplasmic reticulum (ER) and mitochondria dual-targeting nanoparticles (EMT-NPs), which can synergistically elicit ER stress and mitochondrial dysfunction. In vitro experiments indicated that EMT-NPs could effectively enter ER and mitochondria at an approximate ratio of 2 to 3. Subsequently, EMT-NPs could upregulate ER stress-related protein expression (IRE1α, CHOP), boosting calcium ion (Ca²⁺) efflux and activating the caspase-12 signaling cascade in cancer cells. In addition, EMT-NPs induced direct oxidative stress in mitochondria; some mitochondrial-related apoptotic events such as decreased mitochondrial membrane potential (MMP), upregulation of Bax, cytochrome c release, and caspase-3 activation were also observed for tumor cells upon incubation with EMT-NPs. Furthermore, the leaked Ca²⁺ from ER could induce mitochondrial Ca²⁺ overloading to further augment cancer cell apoptosis. In brief, mitochondrial and ER signaling networks collaborated well to promote cancer cell death. Extended photoacoustic and fluorescence imaging served well for the treatment of in vivo patient-derived xenografts cancer model. This drug-free macromolecular strategy with multiple subcellular targeting provides a potential paradigm for cancer theranostics in precision nanomedicine.

Novel anthraquinone derivatives trigger endoplasmic reticulum stress response and induce apoptosis

Background: Endoplasmic reticulum (ER) stress is a therapeutic target in cancer given its regulation of bioenergetics and cell death. Methodology & results: We synthesized 14 ER stress-triggered anthraquinone derivatives by introducing an amino group at the 3-position side chain of the lead compound obtained previously. Most of the anthraquinone derivatives exhibited good antitumor activity due to their ability to induce ER damage through cytoplasmic vacuoles. The mechanisms of ER stress caused by compound KA-4c were related to increasing the expression levels of the ATF6 and Bip proteins and upregulating CHOP and cleaved PARP. Conclusion: Compound KA-4c triggers ER stress response and induces apoptosis via the ATF6-CHOP signaling pathway.

Synthesis of ruthenium polypyridine complexes with benzyloxyl groups and their antibacterial activities against Staphylococcus aureus

Four new ruthenium polypyridyl complexes, [Ru(bpy)₂(BPIP)](PF₆)₂ (Ru(II)-1), [Ru(dtb)₂(BPIP)](PF₆)₂ (Ru(II)-2), [Ru(dmb)₂(BPIP)](PF₆)₂ (Ru(II)-3) and [Ru(dmob)₂(BPIP)](PF₆)₂ (Ru(II)-4) (bpy = 2,2'-bipyridine, dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dmob = 4,4'-dimethoxy-2,2'-bipyridine and BPIP = 2-(3,5-bis(benzyloxyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) had been synthesized and characterized. Their antimicrobial activities were investigated against Staphylococcus aureus (S. aureus) and four complexes showed obvious antibacterial effect, especially the minimum inhibition concentration (MIC) value of Ru(II)-3 was only 4 μg/mL. In addition, Ru(II)-3 was able to kill bacteria quickly and inhibit the formation of biofilm. Meanwhile, the cooperative effect between Ru(II)-3 and general antibiotics were tested and the results showed that Ru(II)-3 could enhance the susceptibility of S. aureus to different types of antibiotics. Most importantly, Ru(II)-3 hardly showed cytotoxicity to mammalian erythrocytes both in homelysis experiment and G. mellonella model. After being injected with high doses of the Ru(II)-3in vivo, the G. mellonella worms still exhibited high survival rates. Finally, a mouse skin infection model and G. mellonella infection model was built to determine the antibacterial activity of Ru(II)-3in vivo. The antibacterial mechanism of Ru(II)-3 was probably related to the membrane-disruption. Taken together, ruthenium polypyridine complexes with benzyloxyl groups had the potential to develop an attractive and untraditional antibacterial agent with new mode of action.

Vitamin D3 and Salinomycin synergy in MCF-7 cells cause cell death via endoplasmic reticulum stress in monolayer and 3D cell culture

1α, 25, dihydroxyvitamin D₃ (1,25D), the active form of vitamin D₃, has antitumor properties in several cancer cell lines in vitro. Salinomycin (Sal) has anticancer activity against cancer cell lines. This study aims to examine the cytotoxic and antiproliferative effect of Sal associated with 1,25D on MCF-7 breast carcinoma cell line cultured in monolayer (2D) and three-dimensional models (mammospheres). We also aim to evaluate the molecular mechanism of Sal and 1,25D-mediated effects. We report that Sal and 1,25D act synergistically in MCF-7 mammospheres and monolayer causing G1 cell cycle arrest, reduction of mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) overproduction with a long-lasting cytotoxic response represented by clonogenic and mammosphere assay. We observed the induction of cell death by apoptosis with upregulation in mRNA levels of apoptosis-related genes (CASP7, CASP9, and BBC3). Extensive cytoplasmic vacuolization, a morphological characteristic found in paraptosis, was also seen and could be triggered by endoplasmic reticulum stress (ER) as we found transcriptional upregulation of genes related to ER stress (ATF6, GADD153, GADD45G, EIF2AK3, and HSPA5). Overall, Sal and 1,25D act synergistically, inhibiting cell proliferation by activating simultaneously multiple death pathways and may be a novel and promising luminal A breast cancer therapy strategy.

Induction of Paraptosis by Cyclometalated Iridium Complex-Peptide Hybrids and CGP37157 via a Mitochondrial Ca2+ Overload Triggered by Membrane Fusion between Mitochondria and the Endoplasmic Reticulum

We previously reported that a cyclometalated iridium (Ir) complex-peptide hybrid (IPH) 4 functionalized with a cationic KKKGG peptide unit on the 2-phenylpyridine ligand induces paraptosis, a relatively newly found programmed cell death, in cancer cells (Jurkat cells) via the direct transport of calcium (Ca²⁺) from the endoplasmic reticulum (ER) to mitochondria. Here, we describe that CGP37157, an inhibitor of a mitochondrial sodium (Na⁺)/Ca²⁺ exchanger, induces paraptosis in Jurkat cells via intracellular pathways similar to those induced by 4. The findings allow us to suggest that the induction of paraptosis by 4 and CGP37157 is associated with membrane fusion between mitochondria and the ER, subsequent Ca²⁺ influx from the ER to mitochondria, and a decrease in the mitochondrial membrane potential (ΔΨ_m). On the contrary, celastrol, a naturally occurring triterpenoid that had been reported as a paraptosis inducer in cancer cells, negligibly induces mitochondria-ER membrane fusion. Consequently, we conclude that the paraptosis induced by 4 and CGP37157 (termed paraptosis II herein) proceeds via a signaling pathway different from that of the previously known paraptosis induced by celastrol, a process that negligibly involves membrane fusion between mitochondria and the ER (termed paraptosis I herein).

Drug Discovery of Plausible Lead Natural Compounds That Target the Insulin Signaling Pathway: Bioinformatics Approaches

The growing smooth talk in the field of natural compounds is due to the ancient and current interest in herbal medicine and their potentially positive effects on health. Dozens of antidiabetic natural compounds were reported and tested in vivo, in silico, and in vitro. The role of these natural compounds, their actions on the insulin signaling pathway, and the stimulation of the glucose transporter-4 (GLUT4) insulin-responsive translocation to the plasma membrane (PM) are all crucial in the treatment of diabetes and insulin resistance. In this review, we collected and summarized a group of available in vivo and in vitro studies which targeted isolated phytochemicals with possible antidiabetic activity. Moreover, the in silico docking of natural compounds with some of the insulin signaling cascade key proteins is also summarized based on the current literature. In this review, hundreds of recent studies on pure natural compounds that alleviate type II diabetes mellitus (type II DM) were revised. We focused on natural compounds that could potentially regulate blood glucose and stimulate GLUT4 translocation through the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. On attempt to point out potential new natural antidiabetic compounds, this review also focuses on natural ingredients that were shown to interact with proteins in the insulin signaling pathway in silico, regardless of their in vitro/in vivo antidiabetic activity. We invite interested researchers to test these compounds as potential novel type II DM drugs and explore their therapeutic mechanisms.

Natural Berberine-derived Azolyl Ethanols as New Structural Antibacterial Agents against Drug-Resistant Escherichia coli

Natural berberine-derived azolyl ethanols as new structural antibacterial agents were designed and synthesized for fighting with dreadful bacterial resistance. Partial target molecules exhibited potent activity against the tested strains, particularly, nitroimidazole derivative 4d and benzothiazole-2-thoil compound 18b, with low cytotoxicity both exerted strong antibacterial activities against multidrug-resistant Escherichia coli at low concentrations as 0.007 and 0.006 mM, respectively. Meanwhile, the active compounds 4d and 18b possessed the ability to rapidly kill bacteria and observably eradicate the E. coli biofilm by reducing exopolysaccharide content to prevent bacterial adhesion, which was conducive to alleviating the development of E. coli resistance. Preliminary mechanistic explorations suggested that the excellent antibacterial potential of molecules 4d and 18b might be attributed to their ability to disintegrate membrane, accelerate ROS accumulation, reduce bacterial metabolism, and intercalate into DNA groove. These results provided powerful information for the further exploitation of natural berberine derivatives against bacterial pathogens.

Photosensitization of a subcutaneous tumour by the natural anthraquinone parietin and blue light

Photodynamic therapy (PDT) is an anticancer treatment involving administration of a tumour-localizing photosensitizer, followed by activation by light of a suitable wavelength. In previous work, we showed that the natural anthraquinone (AQ) Parietin (PTN), was a promising photosensitizer for photodynamic therapy of leukemic cells in vitro. The present work aimed to analyze the photosensitizing ability of PTN in the mammary carcinoma LM2 cells in vitro and in vivo in a model of subcutaneously implanted tumours. Photodynamic therapy mediated by parietin (PTN-PDT) (PTN 30 µM, 1 h and 1.78 J/cm² of blue light) impaired cell growth and migration of LM2 cells in vitro. PTN per se induced a significant decrease in cell migration, and it was even more marked after illumination (migration index was 0.65 for PTN and 0.30 for PTN-PDT, *p < 0.0001, ANOVA test followed by Tukey's multiple comparisons test), suggesting that both PTN and PTN-PDT would be potential inhibitors of metastasis. Fluorescence microscopy observation indicated cytoplasmic localization of the AQ and no fluorescence at all was recorded in the nuclei. When PTN (1.96 mg) dissolved in dimethyl sulfoxide was topically applied on the skin of mice subcutaneously implanted with LM2 cells, PTN orange fluorescence was strongly noticed in the stratum corneum and also in the inner layers of the tumour up to approximately 5 mm. After illumination with 12.74 J/cm² of blue light, one PDT dose at day 1, induced a significant tumour growth delay at day 3, which was not maintained in time. Therefore, we administered a second PTN-PDT boost on day 3. Under these conditions, the delay of tumour growth was 28% both on days 3 and 4 of the experiment (*p < 0.05 control vs. PTN-PDT, two-way ANOVA, followed by Sidak's multiple comparisons test). Histology of tumours revealed massive tumour necrosis up to 4 mm of depth. Intriguingly, a superficial area of viable tumour in the 1 mm superficial area, and a quite conserved intact skin was evidenced. We hypothesize that this may be due to PTN aggregation in contact with the skin and tumour milieu of the most superficial tumour layers, thus avoiding its photochemical properties. On the other hand, normal skin treated with PTN-PDT exhibited slight histological changes. These preliminary findings encourage further studies of natural AQs administered in different vehicles, for topical treatment of cutaneous malignancies.

Cyclometalated Iridium(III) Complex-Cationic Peptide Hybrids Trigger Paraptosis in Cancer Cells via an Intracellular Ca2+ Overload from the Endoplasmic Reticulum and a Decrease in Mitochondrial Membrane Potential

In our previous paper, we reported that amphiphilic Ir complex–peptide hybrids (IPHs) containing basic peptides such as KK(K)GG (K: lysine, G: glycine) (e.g., ASb-2) exhibited potent anticancer activity against Jurkat cells, with the dead cells showing a strong green emission. Our initial mechanistic studies of this cell death suggest that IPHs would bind to the calcium (Ca²⁺)–calmodulin (CaM) complex and induce an overload of intracellular Ca²⁺, resulting in the induction of non-apoptotic programmed cell death. In this work, we conduct a detailed mechanistic study of cell death induced by ASb-2, a typical example of IPHs, and describe how ASb-2 induces paraptotic programmed cell death in a manner similar to that of celastrol, a naturally occurring triterpenoid that is known to function as a paraptosis inducer in cancer cells. It is suggested that ASb-2 (50 µM) induces ER stress and decreases the mitochondrial membrane potential (ΔΨ_m), thus triggering intracellular signaling pathways and resulting in cytoplasmic vacuolization in Jurkat cells (which is a typical phenomenon of paraptosis), while the change in ΔΨ_m values is negligibly induced by celastrol and curcumin. Other experimental data imply that both ASb-2 and celastrol induce paraptotic cell death in Jurkat cells, but this induction occurs via different signaling pathways.

Thiophene-2-carboxamide derivatives of anthraquinone: A new potent antitumor chemotype

The anthraquinone scaffold has long been known as a source of efficacious antitumor drugs. In particular, the various chemical modifications of the side chains in this scaffold have yielded the compounds potent for the wild type tumor cells, their counterparts with molecular determinants of altered drug response, as well as in vivo settings. Further exploring the chemotype of anticancer heteroarene-fused anthraquinones, we herein demonstrate that derivative of anthra[2,3-b]thiophene-2-carboxamide, (compound 8) is highly potent against a panel of human tumor cell lines and their drug resistant variants. Treatment with submicromolar or low micromolar concentrations of 8 for only 30 min was sufficient to trigger lethal damage of K562 chronic myelogenous leukemia cells. Compound 8 (2.5 μM, 3-6 h) induced an apoptotic cell death as determined by concomitant activation of caspases 3 and 9, cleavage of poly(ADP-ribose) polymerase, increase of Annexin V/propidium iodide double stained cells, DNA fragmentation (subG1 fraction) and a decrease of mitochondrial membrane potential. Neither a significant interaction with double stranded DNA nor strong inhibition of the DNA dependent enzyme topoisomerase 1 by 8 were detectable in cell free systems. Laser scanning confocal microscopy revealed that some amount of 8 was detectable in mitochondria as early as 5 min after the addition to the cells; exposure for 1 h caused significant morphological changes and clustering of mitochondria. The bioisosteric analog 2 in which the thiophene ring was replaced with furan was less active although the patterns of cytotoxicity of both derivatives were similar. These results point at the specific role of the sulfur atom in the antitumor properties of carboxamide derivatives of heteroarene-fused anthraquinone.

Purpurin binding interacts with LHPP protein that inhibits PI3K/AKT phosphorylation and induces apoptosis in colon cancer cells HCT-116

Colorectal cancer (CRC) is the leading type of diagnosed cancer; globally, it resides in the fourth-leading origin of cancer-interrelated mortality in the globe. The treatment strategies were chemotherapy and potent radiotherapy. Although chemotherapy treatment can eliminate tumor cells, it remains with unnecessary toxic effects in cancer patients. Therefore, the identification of natural-based compounds, which have selectively inhibiting target proteins with limited toxicity that can facilitate the therapeutic approaches against CRC. In this existing approach, which highlights the binding efficacy of our anthraquinone compound, purpurin against phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) protein restrains the CRC cell growth by inhibiting phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT), cell proliferation, and inducing apoptosis signaling. Primarily, purpurin (36 μM) exposed to HCT-116 cells and incubated for 24 and 48 h could induce reactive oxygen species production, subsequently alter mitochondrion membrane, and increase the apoptotic cells in HCT-116. LHPP, a kind of histidine phosphatase protein, has been considered as a tumor suppressor in numerous carcinomas. However, purpurin-mediated LHPP proteins and its associated molecular events in CRC remain unclear. In our docking studies revealed that purpurin has been strongly interacts with LHPP via hydrophobic and hydrophilic binding interaction. Western blot results confirmed that purpurin enhances the expression of LHPP protein, thereby inhibits the expression of phosphorylated-PI3K/AKT, EGFR, cyclin-D1, PCNA in HCT-116 cells. Moreover, purpurin induces messenger RNA expression of apoptotic genes (Bax, CASP-9, and CASP-3) in HCT-116 cells. Thus, we conclude that purpurin could be a natural and useful compound, which inhibits the growth of CRC cells through the activation of LHPP proteins.

Confirming whether novel rhein derivative 4a induces paraptosis-like cell death by endoplasmic reticulum stress in ovarian cancer cells

Ovarian cancer is the leading cause of death among gynecologic cancer patients. Although platinum-based chemotherapy as a frontline treatment for ovarian cancer has been widely used in clinical settings, its clinical efficacy is not satisfactory due to the resistance of ovarian cancer cells to apoptosis. Therefore, it is of great significance to induce non-apoptotic programed cell death patterns, such as paraptosis, in ovarian cancer. In this study, we aimed to explore the potential anticancer mechanisms of novel rhein derivative 4a, which was modified with rhein as a lead compound. The results showed that a wide range of vacuoles from the endoplasmic reticulum and mitochondria appeared in ovarian SKOV3, SKOV3-PM4, and A2780 cells treated with derivative 4a, and the cell death caused by derivative 4a is a type of non-apoptotic and non-autophagic death, which is caused by expansion and damage of the endoplasmic reticulum or mitochondria, showing the characteristics of para-apoptotic death. Furthermore, derivative 4a stimulated the unfolded protein reaction of ovarian cancer cells by upregulating the expression of Bip78 and activating the PERK-eIF2α-ATF4 pathways. Notably, rhein derivative 4a-induced cell death was positively correlated with activation of p38, ERK, and JNK, and negatively correlated with Alix, a known protein that inhibits paraptosis. In addition, derivative 4a treatment also induced G2/M phase arrest in ovarian cancer cells. Taken together, our study reveals that derivative 4a induces paraptosis, and this finding can serve as a basis in developing a new strategy for the treatment of antiapoptotic ovarian cancer.

Rhein Derivative 4F Inhibits the Malignant Phenotype of Breast Cancer by Downregulating Rac1 Protein

Background

Triple-negative breast cancer is a common malignant tumor with unfavorable prognosis affecting women worldwide; thus, there is an urgent need for novel therapeutic drugs with improved anti-tumor activity. Rac family small GTPase 1 (Rac1) plays an important role in malignant behavior and is a promising therapeutic target. We reported an anthraquinone compound, Rhein, and its derivative, 4F, and investigated their downregulation effects on Rac1 in breast cancer cells in vitro.

Methods

The inhibition of cell proliferation by derivative 4F was investigated in two breast cancer (MDA-MB-231 and MCF-7) and normal breast (MCF-10A) cell lines by cell counting kit-8 assay and growth curves. The role of 4F in cell migration and invasion and cytoskeletal change were assessed by Transwell chamber assay and F-actin staining, respectively. The affinity of Rhein and its derivative for Rac1 protein and the regulation of Rac1 promoter activity were evaluated by molecular docking software and luciferase reporter gene assay, respectively. Rac1 protein expression was determined by western blot assay.

Results

Compared to Rhein, derivative 4F more strongly inhibited breast cancer cell proliferation, migration, and invasion and also cause cytoskeletal changes like those in paclitaxel. Derivative 4F not only bound more stably to Rac1 but also inhibited Rac1 promoter activity in cells and downregulated Rac1 protein expression.

Conclusions

Rhein derivative 4F is a new anthraquinone compound with better anti-tumor activity than that of the lead compound Rhein in breast cancer. It down-regulated Rac1 expression and may be a small molecule inhibitor of Rac1.

Novel Anthraquinone Compounds Inhibit Colon Cancer Cell Proliferation via the Reactive Oxygen Species/JNK Pathway

A series of amide anthraquinone derivatives, an important component of some traditional Chinese medicines, were structurally modified and the resulting antitumor activities were evaluated. The compounds showed potent anti-proliferative activities against eight human cancer cell lines, with no noticeable cytotoxicity towards normal cells. Among the candidate compounds, 1-nitro-2-acyl anthraquinone-leucine (8a) showed the greatest inhibition of HCT116 cell activity with an IC₅₀ of 17.80 μg/mL. In addition, a correlation model was established in a three-dimensional quantitative structure-activity relationship (3D-QSAR) study using Comparative Molecular Field Analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA). Moreover, compound 8a effectively killed tumor cells by reactive oxygen species (ROS)-JNK activation, causing an increase in ROS levels, JNK phosphorylation, and mitochondrial stress. Cytochrome c was then released into cytoplasm, which, in turn activated the cysteine protease pathway and ultimately induced tumor cell apoptosis, suggesting a potential use of this compound for colon cancer treatment.

Novel anthraquinone compounds as anticancer agents and their potential mechanism

Anthraquinones exhibit a unique anticancer activity. Since their discovery, medicinal chemists have made several structural modifications, resulting in the design and synthesis of a large number of novel anthraquinone compounds with different biological activities. In general, anthraquinone compounds have been considered to have anticancer activity mainly through DNA damage, cycle arrest and apoptosis. However, recent studies have shown that novel anthraquinone compounds may also inhibit cancer through paraptosis, autophagy, radiosensitising, overcoming chemoresistance and other methods. This Review article provides an overview of novel anthraquinone compounds that have been developed as anticancer agents in recent years and focuses on their anticancer mechanism.

Synthesis and screening of novel anthraquinone−quinazoline multitarget hybrids as promising anticancer candidates

Aim: The EGF receptor (EGFR) is overexpressed in multiple epithelial-derived cancers and is considered to be a vital target closely associated with cancer therapy. In this study, a series of novel anthraquinone−quinazoline hybrids targeting several vital sites for cancer therapy were designed and synthesized. Methodology & results: Most of the synthesized hybrids demonstrated excellent antiproliferative activity and downregulation of the expression of EGFR. The most promising compound 7d showed the strongest antiproliferation activity; this compound significantly downregulated the expression of p-EGFR protein, induced a remarkable apoptosis effect, promoted the rearrangement of F-actin filaments and destruction of cytoskeleton, induced DNA damage and enhanced radiosensitivity of A549 cells. Conclusion: The novel anthraquinone−quinazoline hybrid 7d emerges as an anticancer drug candidate with promising multitargeted biological activities.

Small-molecule compounds target paraptosis to improve cancer therapy

According to its different occurrence mechanism, programmed cell death (PCD) is divided into apoptosis, autophagy, necrosis, paraptosis and so on. Paraptosis is morphologically different from apoptosis and autophagy, which exhibit cytoplasmic vacuolation derived from the ER, independent of caspase, absence of apoptotic morphology. Recent researches have implied that a variety of small molecule compounds, such as celastrol, curcumin, can induce paraptosis-associated cell death as the reagent to enhance anti-cancer activity. A better understanding of paraptosis will lay the foundation to develop new therapeutic strategies to treat human cancers that make full use of small-molecule compounds.

Plumbagin induces paraptosis in cancer cells by disrupting the sulfhydryl homeostasis and proteasomal function

Plumbagin (PLB) is an active secondary metabolite extracted from the roots of Plumbago rosea. In this study, we report that plumbagin effectively induces paraptosis by triggering extensive cytoplasmic vacuolation followed by cell death in triple negative breast cancer cells (MDA-MB-231), cervical cancer cells (HeLa) and non-small lung cancer cells (A549) but not in normal lung fibroblast cells (WI-38). The vacuoles originated from the dilation of the endoplasmic reticulum (ER) and were found to be empty. The cell death induced by plumbagin was neither apoptotic nor autophagic. Plumbagin induced ER stress mainly by inhibiting the chymotrypsin-like activity of 26S proteasome as also evident from the accumulation of polyubiquitinated proteins. The vacuolation and cell death were found to be independent of reactive oxygen species generation but was effectively inhibited by thiol antioxidant suggesting that plumbagin could modify the sulfur homeostasis in the cellular milieu. Plumbagin also resulted in a decrease in mitochondrial membrane potential eventually decreasing the ATP production. This is the first study to show that Plumbagin induces paraptosis through proteasome inhibition and disruption of sulfhydryl homeostasis and thus further opens up the lead molecule to potential therapeutic strategies for apoptosis-resistant cancers.