Plumbagin induces G2-M arrest and autophagy by inhibiting the AKT/mammalian target of rapamycin pathway in breast cancer cells

Rapamycin increases leukemia cell sensitivity to chemotherapy by regulating mTORC1 pathway-mediated apoptosis and autophagy

This study investigated the effect of rapamycin alone and in combination with chemotherapy (doxorubicin and cytarabine) on AML. Human acute monocytic leukemia cell line SHI-1 and NPG AML model mice created by intravenous injection of SHI-1 cell were treated with rapamycin, chemotherapy, or rapamycin plus chemotherapy. Analysis by cell counting kit-8, western blot, flow cytometry, and immunohistochemistry was performed, and results suggested that both rapamycin and chemotherapy inhibited proliferation of SHI-1 cells both in vitro and in vivo, suppressed neoplasm growth in vivo, and promoted survival of NPG AML mice. The antitumor effect of rapamycin plus chemotherapy was better than that of rapamycin alone and chemotherapy alone. In addition, western blot results demonstrated that rapamycin inhibited the phosphorylation of mTOR downstream targets 4EBP1 and S6K1 in SHI-1 cells, and increased the pro-apoptosis-related protein Bax and autophagy-associated proteins Beclin-1, LC3B-II, and ATG5 while reducing the anti-apoptosis-related protein Bcl-2. In conclusion, the results of this study indicate that rapamycin acts synergistically with doxorubicin and cytarabine in AML treatment, and its underlying mechanism might be associated with mTORC1 pathway-mediated apoptosis and autophagy.

Biological Potential of Carnivorous Plants from Nepenthales

Since Charles Darwin and his book carnivorous plants have aroused interest and heated debate. In addition, there is growing interest in this group of plants as a source of secondary metabolites and in the application of their biological activity. The aim of this study was to trace the recent literature in search of the application of extracts obtained from families Droseraceae, Nepenthaceae, and Drosophyllaceae to show their biological potential. The data collected in the review clearly indicate that the studied Nepenthales species have great biological potential in terms of antibacterial, antifungal, antioxidant, anti-inflammatory, and anticancer use. We proposed that further investigations should include: (i) bioactivity-guided investigations of crude plant extract to connect a particular type of action with a specific compound or a group of metabolites; (ii) a search for new bioactive properties of carnivorous plants; (iii) establishment of molecular mechanisms associated with specific activity. Furthermore, further research should be extended to include less explored species, i.e., Drosophyllum lusitanicum and especially Aldrovanda vesiculosa.

Plumbagin Exhibits Genotoxicity and Induces G2/M Cell Cycle Arrest via ROS-Mediated Oxidative Stress and Activation of ATM-p53 Signaling Pathway in Hepatocellular Cells

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone, PLB), a naturally occurring naphthoquinone mainly isolated from the plant Plumbago zeylanica L., has been proven to possess anticancer activities towards multiple types of cancer. Although there has been an increasing amount of research regarding its anticancer effects, the association between oxidative stress, genotoxicity and the cell cycle arrest induced by PLB still remains unclear. Therefore, it is important to investigate their potential connections and the involvement of DNA damage and the ataxia telangiectasia mutated protein (ATM)-p53 signaling pathway in PLB’s anticancer mechanism. The present study showed that PLB exposure significantly reduced HCC cell viability and colony formation. In addition, PLB-induced G2/M cell cycle arrest, oxidative stress, and DNA damage was detected, which could be almost blocked by NAC pretreatment. PLB could trigger a DNA damage response by activating cell cycle checkpoints such as ATM, checkpoint kinase 1 (Chk1), checkpoint kinase 2 (Chk2) and p53. Meanwhile, the key modulator of the G2/M transition factor, Cell Division Cycle 25C (cdc25C), was significantly downregulated in an ROS-dependent manner. Furthermore, pretreatment with ATM and p53 inhibitors (KU55933 and Pifithrin-α) could reduce the occurrence of G2/M cell cycle arrest by inhibiting the activation of the ATM-p53 pathway. Taken together, these results indicate that ROS-mediated oxidative stress plays a key role in PLB-induced G2/M cell cycle arrest mediated by the ATM-p53 pathway.

M, K M, Dey T, Zargar MI, Singh J. Recent advance of herbal medicines in cancer- a molecular approach

Bioactive compounds are crucial for an extensive range of therapeutic uses, and some exhibit anticancer activity. Scientists advocate that phytochemicals modulate autophagy and apoptosis, involved in the underlying pathobiology of cancer development and regulation. The pharmacological aiming of the autophagy-apoptosis signaling pathway using phytocompounds hence offers an auspicious method that is complementary to conventional cancer chemotherapy. The current review aims to explore the molecular level of the autophagic-apoptotic pathway to know its implication in the pathobiology of cancer and explore the essential cellular process as a druggable anticancer target and therapeutic emergence of naturally derived phytocompound-based anticancer agents. The data in the review were collected from scientific databases such as Google search, Web of Science, PubMed, Scopus, Medline, and Clinical Trials. With a broad outlook, we investigated their cutting-edge scientifically revealed and/or searched pharmacologic effects, a novel mechanism of action, and molecular signaling pathway of phytochemicals in cancer therapy. In this review, the evidence is focused on molecular pharmacology, specifically caspase, Nrf2, NF-kB, autophagic-apoptotic pathway, and several mechanisms to understand their role in cancer biology.

Plumbagin rescues the granulosa cell's pyroptosis by reducing WTAP-mediated N6-methylation in polycystic ovary syndrome

The survival of ovary granulosa cells (GC) is critical in the initiation and progression of polycystic ovary syndrome (PCOS) in females. Here, we found that the PCOS process is accompanied by massive GC pyroptosis resulting from Caspase-1 inflammasome activation. Administration of plumbagin, an effective compound isolated from plant medicine, can prevent the pyroptosis of GC and the onset of PCOS. Mechanistic study indicates the over-activation of the inflammasome in GC is due to the upregulation of WTAP, a key regulator of the RNA N6-methylase complex. WTAP mediates the mRNA N6-methylation of NLRP3 inflammasome component ASC and enhances ASC RNA stability, which results in the overactivation of the inflammasome in GCs from the PCOS model. Plumbagin treatment suppresses the WTAP-mediated N6-methylation of ASC mRNA and reduces the pyroptosis of GCs. This study supports the profound potential of plumbagin in PCOS treatment.

Plumbagin Suppresses Breast Cancer Progression by Downregulating HIF-1α Expression via a PI3K/Akt/mTOR Independent Pathway under Hypoxic Condition

Hypoxia-inducible factor-1α (HIF-1α) is a major transcriptional regulator that plays a crucial role in the hypoxic response of rapidly growing tumors. Overexpression of HIF-1α has been associated with breast cancer metastasis and poor clinical prognosis. Plumbagin, the main phytochemical from Plumbago indica, exerts anticancer effects via multiple mechanisms. However, its precise mechanisms on breast cancer cells under hypoxic conditions has never been investigated. This study aims to examine the anticancer effect of plumbagin on MCF-7 cell viability, transcriptional activity, and protein expression of HIF-1α under normoxia and hypoxia-mimicking conditions, as well as reveal the underlying signaling pathways. The results demonstrate that plumbagin decreased MCF-7 cell viability under normoxic conditions, and a greater extent of reduction was observed upon exposure to hypoxic conditions induced by cobalt chloride (CoCl₂). Mechanistically, MCF-7 cells upregulated the expression of HIF-1α protein, mRNA, and the VEGF target gene under CoCl₂-induced hypoxia, which were abolished by plumbagin treatment. In addition, inhibition of HIF-1α and its downstream targets did not affect the signaling transduction of the PI3K/Akt/mTOR pathway under hypoxic state. This study provides mechanistic insight into the anticancer activity of plumbagin in breast cancer cells under hypoxic conditions by abolishing HIF-1α at transcription and post-translational modifications.

Tight association of autophagy and cell cycle in leukemia cells

Background

Autophagy plays an essential role in maintaining cellular homeostasis and in the response to cellular stress. Autophagy is also involved in cell cycle progression, yet the relationship between these processes is not clearly defined.

Results

In exploring this relationship, we observed that the inhibition of autophagy impaired the G2/M phase-arresting activity of etoposide but enhanced the G1 phase-arresting activity of palbociclib. We further investigated the connection of basal autophagy and cell cycle by utilizing the autophagosome tracer dye Cyto-ID in two ways. First, we established a double-labeling flow-cytometric procedure with Cyto-ID and the DNA probe DRAQ5, permitting the cell cycle phase-specific determination of autophagy in live cells. This approach demonstrated that different cell cycle phases were associated with different autophagy levels: G1-phase cells had the lowest level, and G2/M-phase cells had the highest one. Second, we developed a flow-cytometric cell-sorting procedure based on Cyto-ID that separates cell populations into fractions with low, medium, and high autophagy. Cell cycle analysis of Cyto-ID-sorted cells confirmed that the high-autophagy fraction contained a much higher percentage of G2/M-phase cells than the low-autophagy fraction. In addition, Cyto-ID-based cell sorting also proved to be useful for assessing other autophagy-related processes: extracellular flux analysis revealed metabolic differences between the cell populations, with higher autophagy being associated with higher respiration, higher mitochondrial ATP production, and higher glycolysis.

Conclusion

This work provides clear evidence of high autophagy in G2/M-phase cells by establishing a novel cell sorting technique based on Cyto-ID.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00334-8.

Autophagy Modulators in Coronavirus Diseases: A Double Strike in Viral Burden and Inflammation

Coronaviruses are the etiologic agents of several diseases. Coronaviruses of critical medical importance are characterized by highly inflammatory pathophysiology, involving severe pulmonary impairment and infection of multiple cell types within the body. Here, we discuss the interplay between coronaviruses and autophagy regarding virus life cycle, cell resistance, and inflammation, highlighting distinct mechanisms by which autophagy restrains inflammatory responses, especially those involved in coronavirus pathogenesis. We also address different autophagy modulators available and the rationale for drug repurposing as an attractive adjunctive therapy. We focused on pharmaceuticals being tested in clinical trials with distinct mechanisms but with autophagy as a common target. These autophagy modulators act in cell resistance to virus infection and immunomodulation, providing a double-strike to prevent or treat severe disease development and death from coronaviruses diseases.

Antiviral Activity of Zinc Oxide Nanoparticles Mediated by Plumbago indica L. Extract Against Herpes Simplex Virus Type 1 (HSV-1)

INTRODUCTION

Plumbago indica L. is considered a valuable source in the Plumbaginaceae family for various types of active compound such as alkaloids, phenolics and saponins. To promote the usage of P. indica in the bionanotechnology field, zinc oxide nanoparticles (ZnONPs) were biosynthesized by using its alcoholic extract. The inhibitory effects of ZnONPs and the plant extract were also evaluated against HSV-1.

METHODS

ZnONPs were described by the following techniques, UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The phenolic and flavonoid contents of P. indica extract, which are accountable for bioreduction, formation and stabilization of the nanoparticles, were analyzed by HPLC technique. The antiviral assessment was implemented on both agents by using Vero cell lines.

RESULTS

DLS revealed that the average size of ZnONPs was 32.58 ± 7.98 nm and the zeta potential was -20.8 mV. The observation of TEM analysis revealed that the particle size of ZnONPs varied from 2.56 to 8.83 nm. The XRD analysis verified the existence of pure crystals of hexagonal shapes of nanoparticles of ZnO with a main average size of 35.28 nm that is approximating to the values of particle size acquired by SEM analysis (19.64 and 23.21 nm). The HPLC analysis of P. indica ethanolic extract showed that gallic acid, chlorogenic acid and rutin were the major compounds, with concentrations equal to 8203.99, 2965.95 and 1144.99 µg/g, respectively. Regarding the antiviral assessment, the synthesized uncalcinated ZnONPs were found to exhibit a promising activity against HSV-1, with CC50 and IC50 values equal to 43.96 ± 1.39 and 23.17 ± 2.29 µg/mL, respectively.

CONCLUSION

The green synthesized ZnONPs are considered promising adjuvants to enhance the efficacy of HSV-1 drugs.

Antiparasitic Effect of Stilbene and Terphenyl Compounds against Trypanosoma cruzi Parasites

Background: Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi. No progress in the treatment of this pathology has been made since Nifurtimox was introduced more than fifty years ago, and this drug is considered very aggressive and may cause several adverse effects. This drug currently has severe limitations, including a high frequency of undesirable side effects and limited efficacy and availability, so research to discover new drugs for the treatment of Chagas disease is imperative. Many drugs available on the market are natural products as found in nature or compounds designed based on the structure and activity of these natural products. Methods: This study evaluated the in vitro antiparasitic activity of a series of previously synthesized stilbene and terphenyl compounds in T. cruzi epimastigotes and intracellular amastigotes. The action of the most selective compounds was investigated by flow cytometric analysis to evaluate the mechanism of cell death. The ability to induce apoptosis or caspase-1 inflammasomes was assayed in macrophages infected with T. cruzi after treatment, comparing it with that of Nifurtimox. Results: The stilbene ST18 was the most potent compound of the series. It was slightly less active than Nifurtimox in epimastigotes but most active in intracellular amastigotes. Compared to Nifurtimox, it was markedly less cytotoxic when tested in vitro on normal cells. ST18 was able to induce a marked increase in parasites positive for Annexin V and monodansylcadaverine. Moreover, ST18 induced the activation, in infected macrophages, of caspase-1, a conserved enzyme that plays a major role in controlling parasitemia, host survival and the onset of the adaptive immune response in Trypanosoma infection. Conclusions: The antiparasitic activity of ST18 together with its ability to activate caspase-1 in infected macrophages and its low toxicity toward normal cells makes this compound interesting for further clinical investigation.

Light emitting diodes optimisation for secondary metabolites production by Droseraceae plants

The most abundant active compound in Droseraceae is plumbagin, a naphthoquinone widely used for medical purposes due to its antimicrobial, antitussive, antimalarial and anticancer properties. In this work, we created a light-emitting diode (LED) based culture illumination setup as an alternative to fluorescent lamps traditionally used as a light source in plant in vitro cultures. The plants of Drosera binata and Drosera peltata cultured under LED illumination grew equally well and produced similar amounts of biologically active compounds as plants grown under fluorescent lamps. The plants were cultured on two media differing in mineral composition, sucrose content and pH. Secondary metabolites were extracted with ethanol from the plants after harvesting. The extracts were subjected to HPLC and microbiological analyses. We observed differences in morphology and secondary metabolism between plants of the same species grown on different media. However, we did not note significant changes in secondary metabolite yield under assessed lighting conditions. We propose LEDs as a more efficient, eco-friendly and economically reasonable source of light for big scale in vitro production of plumbagin in Drosera species than fluorescent lamps.

Resistance to Intervention: Paclitaxel in Breast Cancer

Breast cancer stands as the most prevalent cancer in women globally, and contributes to the highest percentage of mortality due to cancer-related deaths in women. Paclitaxel (PTX) is heavily relied on as a frontline chemotherapy drug in breast cancer treatment, especially in advanced metastatic cancer. Generation of resistance to PTX often derails clinical management and adversely affects patient outcomes. Understanding the molecular mechanism of PTX resistance is necessary to device methods to aid in overcoming the resistance. Recent studies exploring the mechanism of development of PTX resistance have led to unveiling of a range novel therapeutic targets. PTX resistance pathways that involve major regulatory proteins/RNAs like RNF8/Twist/ROR1, TLR, ErbB3/ErbB2, BRCA1- IRIS, MENA, LIN9, MiRNA, FoxM1 and IRAK1 have expanded the complexity of resistance mechanisms, and brought newer insights into the development of drug targets. These resistance-related targets can be dealt with synthetic/natural therapeutics in combination with PTX. The present review encompasses the recent understanding of PTX resistance mechanisms in breast cancer and possible therapeutic combinations to overcome resistance.

Antiproliferation Activity and Apoptotic Mechanism of Soursop (Annona muricata L.) Leaves Extract and Fractions on MCF7 Breast Cancer Cells

Introduction

Breast cancer is the second most common cancer in women globally, and the incidence rate has increased annually. Traditional medicine is frequently used as a cancer treatment, and soursop or Annona muricata L (A. muricata) is a traditional medicinal plant that has been widely used as an anticancer treatment and requires more thorough study.

Methods

In this research, we prepared ethanol extract and three solvents, ie, ethyl acetate, n-hexane and water fractions of A. muricata leaves and assessed their antiproliferation and cytotoxic activity on MCF7 breast cancer cells compared with that on CV1 normal kidney cells; observation of cell morphology by stained with mixture of propidium iodide and 4',6-diamidino-2-phenylindole indicated that this treatment induced an ongoing process of apoptotic cell death in MCF7 cells. To clarify the cell death mechanism via apoptosis, we assessed the mRNA expression in the caspase cascade of caspase-9, caspase-3, and PARP-1, and anti-apoptotic, Bcl-2 which mediated cytotoxic activity of extracts and ethyl acetate fractions of A. muricata leaves against MCF7 cells.

Results

The ethanol extract, ethyl acetate, n-hexane, and water fractions of A. muricata leaves had IC₅₀ values of 5.3, 2.86, 3.08, and 48.31 µg/mL, respectively, in MCF7 cells but had no activity in CV1 cells. The high cytotoxic activity of A. muricata leaves was reflected by changes in the morphology of cancer cells that appeared after 6 h exposure to A. muricata leaf extract and ethyl acetate fraction; the membrane and nucleus of cells undergoing apoptosis were characterized by the rupture and loss of membranes and nuclei. The mechanism that mediates this cytotoxic activity in MCF7 cells was mediated through a decrease in the expression of Bcl-2 mRNA and an increase in caspase-9 and caspase-3 mRNA expression.

Conclusion

Therefore, the leaves of the medicinal plant A. muricata contained compounds that on extraction exerted a highly effective activity as an anticancer treatment for breast cancer via induced apoptotic cell death.

Bioinformatics Study of Sea Cucumber Peptides as Antibreast Cancer Through Inhibiting the Activity of Overexpressed Protein (EGFR, PI3K, AKT1, and CDK4)

Breast cancer is the most common type of cancer in women globally. The overexpressed proteins, including EGFR, PI3K, AKT1, and CDK4, have a role in the growth of breast cancer cells. The 3D peptide structure of sea cucumber Cucumaria frondosa was modeled and then docked with EGFR, PI3K, AKT1, and CDK4 proteins using AutoDock Vina software. The docking result, which has the best binding affinity value, is continued with molecular dynamics simulation. The docking results showed that all peptides bind to the active sites of the four proteins. WPPNYQW and YDWRF peptides bind to proteins with lower binding affinity values than positive controls. The four proteins were in a stable state when complexed with the WPPNYQW peptide, which was seen from the RMSD and RMSF value. PI3K-YDWRF and AKT1-YDWRF complexes are stable, characterized by high RMSD values and increased volatility in several amino acids. WPPNYQW peptide has high potential as an antibreast cancer agent because it binds to the active sites of the four proteins with low binding affinity values and stable interactions. Meanwhile, the YDWRF peptide interacts with the four proteins with low binding affinity values, but the interaction is only stable on PI3K and AKT1 proteins.

Plumbagin: A Potential Anti-cancer Compound

Cancer is a deadly disease, which has significantly increased in both developed and developing nations. Treatment of cancer utilizing radiotherapy or chemotherapy actuates a few issues which incorporate spewing, sickness, unpalatable reactions, and so forth. In this specific situation, an alternative drug source, which can effectively treat cancer is of prime importance. Products that are obtained from plant sources are utilized for the treatment of various diseases due to their non-harmful nature. Medicinal plants contain different bioactive compounds, which possess an important role in the prevention of different diseases such as cancer. Plumbagin is a bioactive compound, which is mainly present in Plumbaginaceae family and has been explored for its anticancer activity. Plumbagin basically inactivates the Akt/NF-kB, MMP-9 and VEGF pathways that are essential for cancer cell development. Therefore, it is important to review the role of plumbagin in different cancer cells in order to find an alternative drug to overcome this disease. The present review provides a summary of anticancer activity of plumbagin in various cancers and its mode of action.

Anti-Cancer Stem Cells Potentiality of an Anti-Malarial Agent Quinacrine: An Old Wine in a New Bottle

Quinacrine (QC) is a tricyclic compound and a derivative of 9-aminoacridine. It has been widely used to treat malaria and other parasitic diseases since the last century. Interestingly, studies have revealed that it also displays anti-cancer activities. Here, we have discussed the anti-cancer mechanism of QC along with its potentiality to specifically target cancer stem cells. The anti-cancer action of this drug includes DNA intercalation, inhibition of DNA repair mechanism, prevention of cellular growth, cell cycle arrest, inhibition of DNA and RNA polymerase activity, induction of autophagy, promotion of apoptosis, deregulation of cell signaling in cancer cells and cancer stem cells, inhibition of metastasis and angiogenesis. In addition, we have also emphasized on the synergistic effect of this drug with other potent chemotherapeutic agents and mentioned its different applications in anti-cancer therapy.

A systems pharmacology approach to identify the autophagy-inducing effects of Traditional Persian medicinal plants

Aging is correlated with several complex diseases, including type 2 diabetes, neurodegeneration diseases, and cancer. Identifying the nature of this correlation and treatment of age-related diseases has been a major subject of both modern and traditional medicine. Traditional Persian Medicine (TPM) embodies many prescriptions for the treatment of ARDs. Given that autophagy plays a critical role in antiaging processes, the present study aimed to examine whether the documented effect of plants used in TPM might be relevant to the induction of autophagy? To this end, the TPM-based medicinal herbs used in the treatment of the ARDs were identified from modern and traditional references. The known phytochemicals of these plants were then examined against literature for evidence of having autophagy inducing effects. As a result, several plants were identified to have multiple active ingredients, which indeed regulate the autophagy or its upstream pathways. In addition, gene set enrichment analysis of the identified targets confirmed the collective contribution of the identified targets in autophagy regulating processes. Also, the protein-protein interaction (PPI) network of the targets was reconstructed. Network centrality analysis of the PPI network identified mTOR as the key network hub. Given the well-documented role of mTOR in inhibiting autophagy, our results hence support the hypothesis that the antiaging mechanism of TPM-based medicines might involve autophagy induction. Chemoinformatics study of the phytochemicals using docking and molecular dynamics simulation identified, among other compounds, the cyclo-trijuglone of Juglans regia L. as a potential ATP-competitive inhibitor of mTOR. Our results hence, provide a basis for the study of TPM-based prescriptions using modern tools in the quest for developing synergistic therapies for ARDs.

DNA damage response and breast cancer development: Possible therapeutic applications of ATR, ATM, PARP, BRCA1 inhibition

Breast cancer is the most common and significant cancers in females regarding the loss of life quality. Similar to other cancers, one of the etiologic factors in breast cancer is DNA damage. A plethora of molecules are responsible for sensing DNA damage and mediating actions which lead to DNA repair, senescence, cell cycle arrest and if damage is unbearable to apoptosis. In each of these, aberrations leading to unrepaired damage was resulted in uncontrolled proliferation and cancer. Another cellular function is autophagy defined as a process eliminating of unnecessary proteins in stress cases involved in pathogenesis of cancer. Knowing their role in cancer, scholars have tried to develop strategies in order to target DDR and autophagy. Further, the interactions of DDR and autophagy plus their regulatory role on each other have been focused simultaneously. The present review study has aimed to illustrate the importance of DDR and autophagy in breast cancer according to the related studies and uncover the relation between DDR and autophagy and its significance in breast cancer therapy.

Molecular Insights into the Multifunctional Role of Natural Compounds: Autophagy Modulation and Cancer Prevention

Autophagy is a vacuolar, lysosomal degradation pathway for injured and damaged protein molecules and organelles in eukaryotic cells, which is controlled by nutrients and stress responses. Dysregulation of cellular autophagy may lead to various diseases such as neurodegenerative disease, obesity, cardiovascular disease, diabetes, and malignancies. Recently, natural compounds have come to attention for being able to modulate the autophagy pathway in cancer prevention, although the prospective role of autophagy in cancer treatment is very complex and not yet clearly elucidated. Numerous synthetic chemicals have been identified that modulate autophagy and are favorable candidates for cancer treatment, but they have adverse side effects. Therefore, different phytochemicals, which include natural compounds and their derivatives, have attracted significant attention for use as autophagy modulators in cancer treatment with minimal side effects. In the current review, we discuss the promising role of natural compounds in modulating the autophagy pathway to control and prevent cancer, and provide possible therapeutic options.

Dietary molecules and experimental evidence of epigenetic influence in cancer chemoprevention: An insight

The world-wide rate of incidence of cancer disease has been only modestly contested by the past and current preventive and interventional strategies. Hence, the global effort towards novel ideas to contain the disease still continues. Constituents of human diets have in recent years emerged as key regulators of carcinogenesis, with studies reporting their inhibitory potential against all the three stages vis-a-vis initiation, promotion and progression. Unlike drugs which usually act on single targets, these dietary factors have an advantage of multi-targeted effects and pleiotropic action mechanisms, which are effective against cancer that manifest as a micro-evolutionary and multi-factorial disease. Since most of the cellular targets have been identified and their consumption considered relatively safe, these diet-derived agents often appear as molecules of interest in repurposing strategies. Currently, many of these molecules are being investigated for their ability to influence the aberrant alterations in cell's epigenome for epigenetic therapy against cancer. Targeting the epigenetic regulators is a new paradigm in cancer chemoprevention which acts to reverse the warped-up epigenetic alterations in a cancer cell, thereby directing it towards a normal phenotype. In this review, we discuss the significance of dietary factors and natural products as chemopreventive agents. Further, we corroborate the experimental evidence from existing literature, reflecting the ability of a series of such molecules to act as epigenetic modifiers in cancer cells, by interfering with molecular events that map the epigenetic imprints such as DNA methylation, histone acetylation and non-coding RNA mediated gene regulation.

Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells

Rosmarinic acid (RA) is a polyphenolic compound with various pharmacological properties, including, anti-inflammatory, immunomodulatory, and neuroprotective, as well as having antioxidant and anticancer activities. This study evaluated the effects and mechanisms of RA in two racially different triple-negative breast cancer (TNBC) cell lines. Results obtained show that RA significantly caused cytotoxic and antiproliferative effects in both cell lines in a dose- and time-dependent manner. Remarkably, RA induced cell cycle arrest-related apoptosis and altered the expression of many apoptosis-involved genes differently. In MDA-MB-231 cells, RA arrested the cells in the G0/G1 phase. In contrast, the data suggest that RA causes S-phase arrest in MDA-MB-468 cells, leading to a 2-fold increase in the apoptotic effect compared to MDA-MB-231 cells. Further, in MDA-MB-231 cells, RA significantly upregulated the mRNA expression of three genes: harakiri (HRK), tumor necrosis factor receptor superfamily 25 (TNFRSF25), and BCL-2 interacting protein 3 (BNIP3). In contrast, in the MDA-MB-468 cell line, the compound induced a significant transcription activation in three genes, including TNF, growth arrest and DNA damage-inducible 45 alpha (GADD45A), and BNIP3. Furthermore, RA repressed the expression of TNF receptor superfamily 11B (TNFRSF11B) in MDA-MB-231 cells in comparison to the ligand TNF superfamily member 10 (TNFSF10) and baculoviral IAP repeat-containing 5 (BIRC5) in MDA-MB-468 cells. In conclusion, the data suggest that the polyphenol RA may have a potential role in TNBC therapies, particularly in MDA-MB-468 cells.

Inhibiting the Activity of NADPH Oxidase in Cancer

Significance: The primary function of NADPH oxidases (NOX1-5 and dual oxidases DUOX1/2) is to produce reactive oxygen species (ROS). If inadequately regulated, NOX-associated ROS can promote oxidative stress, aberrant signaling, and genomic instability. Correspondingly, NOX isoforms are known to be overexpressed in multiple malignancies, thus constituting potential therapeutic targets in cancer. Recent Advances: Multiple genetic studies aimed at suppressing the expression of NOX proteins in cellular and animal models of cancer have provided support for the notion that NOXs play a pro-tumorigenic role. Further, large drug screens and rational design efforts have yielded inhibitor compounds, such as the diphenylene iodonium (DPI) analog series developed by our group, with increased selectivity and potency over "first generation" NOX inhibitors such as apocynin and DPI. Critical Issues: The precise role of NOX enzymes in tumor biology remains poorly defined. The tumorigenic properties of NOXs vary with cancer type, and precise tools, such as selective inhibitors, are needed to deconvolute NOX contribution to cancer development. Most NOX inhibitors developed to date are unspecific, and/or their mechanistic and pharmacological characteristics are not well defined. A lack of high-resolution crystal structures for NOX functional domains has hindered the development of potent and selective inhibitors. Future Directions: In-depth studies of NOX interactions with the tumor microenvironment (e.g., cytokines, cell-surface antigens) will help identify new approaches for NOX inhibition in cancer.

SR18292 exerts potent antitumor effects in multiple myeloma via inhibition of oxidative phosphorylation

AIMS

Multiple myeloma (MM) was recently reported to rely on increased oxidative phosphorylation (OXPHOS) for survival, providing a potential opportunity for MM therapy. Herein, we aimed to propose a novel targeted drug for MM treatment, followed by the exploration of reason for OXPHOS enhancement in MM cells.

MATERIALS AND METHODS

The expression of OXPHOS genes and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) was analyzed using bioinformatics analyses, followed by verification in MM cell lines. The effects of SR18292 on OXPHOS were measured by qRT-PCR, Western blot, transmission electron microscopy, oxygen consumption rate and so on. The proliferation and apoptosis were evaluated by CCK-8, flow cytometry and Western blot. The efficiency and safety of SR18292 were assessed in a mouse model of MM.

KEY FINDINGS

The OXPHOS genes were generally overexpressed in MM cells, which was associated with poorer prognosis of MM patients. PGC-1α, a transcriptional coactivator, was upregulated in MM cells, and MM patients with higher PGC-1α expression exhibited increased enrichment of the OXPHOS gene set. Treatment with SR18292 (an inhibitor of PGC-1α) significantly impaired the proliferation and survival of MM cells due to OXPHOS metabolism dysfunction, which leads to energy exhaustion and oxidative damage. Besides, SR18292 potently inhibited tumor growth at a well-tolerated dose in MM model mice.

SIGNIFICANCE

The overexpression of OXPHOS gene set mediated by upregulated PGC-1α provides a structural basis for enhanced OXPHOS in MM cells, and SR18292 (a PGC-1α inhibitor) exerts potent antimyeloma effects, offering a potential tangible avenue for MM therapy.

Up and down-regulation of mRNA in the cytotoxicity and genotoxicity of Plumbagin in HepG2/C3A

Studies that evaluated the mechanisms of action of Plumbagin (PLB) and its toxicity may contribute to future therapeutic applications of this compound. We investigate biomarker important in the mechanisms of action correlate the expression of mRNA with the cytotoxic and genotoxic effects of PLB on HepG2/C3A. In the analysis of cytotoxicity, PLB decreased cell viability and membrane integrity at concentrations ≥ 15μM. Xenobiotic-metabolizing system showed strong mRNA induction of CYP1A1, CYP1A2, and CYP3A4, suggesting extensive metabolization. PLB induced apoptosis and an increase in the mRNA expression of genes BBC3, CASP3, and CASP8. At a concentration of 15μM, there was a reduction in the expression of PARP1 mRNA and an increase in the expression of BECN1 mRNA, suggesting that PLB may also induce cell death by autophagy. PLB induced an arrest at the G2/M phase due to DNA damage, as observed in the comet assay. This damage is associated with the increased mRNA expression of genes p21, GADD45A, and H2AFX and with changes in the expression of proteins H2AX, p21, p53, Chk1, and Chk2. These results allow a better understanding of the cellular action of PLB and of its toxicity, thereby contributing to the development of PLB-based drugs, with markers of mRNA expression possibly playing a role as indicators for monitoring toxicity in human cells.

Plumbagin Induces Cell Cycle Arrest and Apoptosis in A431 Cisplatin-Resistant Cancer Cells

The onset of drug resistance represents the leading cause of chemotherapy failure in clinics. In the last decades, natural compounds have emerged as possible anticancer strategies used either alone or in combination with chemotherapeutic drugs, in order to overcome drug resistance. In fact, plant-derived therapies present biological activity and minimal side effects showing promising roles in the resensitization of resistant cancer cells. This work was aimed at investigating the anticancer potential of the natural naphthoquinone plumbagin in a cisplatin-resistant cancer cell line. The results indicated cytotoxic and pro-oxidant activity of plumbagin in both sensitive (A431wt) and cisplatin-resistant (A431/Pt) human cervix squamous carcinoma cell lines. Moreover, plumbagin treatment induced cell cycle arrest and apoptosis in A431/Pt cells and the inhibition of retinoblastoma complex, suggesting a stronger activity on the cisplatin-resistant cell line. Taken together, the data indicate appreciable in vitro anticancer activity of plumbagin, suggesting that this natural compound could become a tool to overcome cisplatin resistance. Although further studies are necessary, this work underlines a promising role of plumbagin in the resensitization of cisplatin-resistant cancer cells.

Improved drug delivery and anti-tumor efficacy of combinatorial liposomal formulation of genistein and plumbagin by targeting Glut1 and Akt3 proteins in mice bearing prostate tumor

Despite the plethora of significant research progress made to develop novel strategies for the treatment of prostate cancer, this disease remains one of the major global health challenges among men. However, using a co-treatment approach utilizing two or more anticancer drugs has shown tremendous success in the treatment of many cancer types. Nanoliposomes are well known to encapsulate multiple drugs and deliver them at the desired site. In this work, we report the synthesis of nanoliposomes (∼100 nm) encapsulating two drugs, plumbagin, and genistein, to synergistically inhibit the growth of prostate cancer cells. The combination of plumbagin and genistein drugs was found inhibiting xenograft prostate tumor growth by ∼80 % without any appreciable toxicity. Mechanistically, the combination of plumbagin and genistein containing nanoliposomes leads to the inhibition of PI3K/AKT3 signaling pathway as well as the decreased population of Glut-1 transporters to impart the retardation in tumor growth. Decrease in proliferative cells and blood vessels are early biological processes that laid the foundation of the observed anti-tumor effect. Thus, a novel, and non-toxic liposomal formulation, containing plumbagin and genistein drugs, is reported, which can deliver anticancer agents to prostate tumors and inhibit the growth.

Misaponin B Induces G2/M Arrest, Cytokinesis Failure and Impairs Autophagy

Saponins are a group of naturally occurring plant glycosides with the features of their strong foam-forming properties and multibiological effects such as antitumor activity. Though Misaponin B, one of the triterpenoid saponins from Madhuca longifolia, is known to have spermicidal and antioxidant activity, the other biological activities have been never reported so far. Thus, in the present study, the antitumor mechanism of Misaponin B was investigated in A549 and AsPC-1 cancer cells. Misaponin B exerted significant cytotoxicity in A549, H460, SKOV3, and AsPC-1 cancer cells. Among them, A549 and AsPC-1 cells were more susceptible to Misaponin B. Misaponin B induced G2/M arrest and cytokinesis failure and increased the expression of LC3B and p62 with autophagic vacuoles and GFP-LC3 punctae in A549 and AsPC-1 cells. Furthermore, Misaponin B suppressed autophagy flux in A549 cells transfected by GFP-mRFP-LC3 constructs by showing merged yellow color by autophagy flux assay. Overall, our findings provide evidences that Misaponin B induces G2M arrest and impairs autophagy in A549 and AsPC-1 cells.

Autophagy modulator scoring system: a user-friendly tool for quantitative analysis of methodological integrity of chemical autophagy modulator studies

Over the past 20 years (1999-2019), we have witnessed a rapid increase in publications involving chemical macroautophagy/autophagy modulators. However, an overview of the methodologies used in these studies is still lacking, and methodology flaws are frequently observed in some reports. To provide an objective and quantitative analysis of studies involving autophagy modulators, we present an Autophagy Modulator Scoring System (AMSS), which is designed to evaluate methodological integrity. AMSS-A includes the autophagy characterization by 4 aspects, namely, autophagosome quantification, autophagy-related biochemical changes, autophagy substrate degradation, and autophagic flux. AMSS-B contains the pharmacological and functional characteristics of chemical autophagy modulators, including lysosomal function, drug targets, autophagy-dependent pharmacological effects, and validation in multiple cell lines and in vivo models. Our analysis shows that of the 385 studies reporting chemical autophagy modulators, only 142 single studies had examined all 4 aspects of autophagy characterization in AMSS-A, and only 10 out of 142 studies had fulfilled all the AMSS criteria in a single study. A comprehensive analysis of the methodologies used in all the studies was made, along with a summary of studies that demonstrated the highest methodological integrity based on AMSS ranking. To test the reliability of the AMSS, a co-efficiency analysis of scores and co-citation values in the co-citation network was performed, and a significant co-efficiency was obtained. Collectively, AMSS provides insight into the methodological integrity of autophagy modulators studies and also offers a user-friendly toolkit to help choose appropriate assays to characterize autophagy modulators.Abbreviations: 3-MA: 3-methyladenine; AMSS: Autophagy Modulator Scoring System; ATG: autophagy-related; BAF: bafilomycin A₁; BECN1: beclin 1; CQ: chloroquine; GFP: green fluorescent protein; LC3: microtubule associated protein 1 light chain 3; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate.

Plumbagin Prevents Secretory Diarrhea by Inhibiting CaCC and CFTR Channel Activities

Secretory diarrhea, which primarily originates through intestinal pathogens and viruses, is a health burden in many regions worldwide. Enterocyte Cl⁻ channels, as the final step in enterotoxin-induced fluid secretion, constitute an attractive class of targets for diarrhea therapy. Chloride channel inhibitors have become a new class of candidates for antisecretion and anti-intestinal motility agents. In the present study, we identified plumbagin as a transmembrane protein 16A (TMEM16A) inhibitor in a cell-based fluorescence-quenching assay, and the IC₅₀ value was ∼12.46 µM. Short-circuit current measurements showed that plumbagin reversibly inhibited the E_act-induced Cl⁻ current on the apical side of TMEM16A-transfected Fischer rat thyroid (FRT) cells with no significant effect on cytoplasmic Ca²⁺ signaling. Notably, plumbagin also inhibited the activity of intestinal epithelial calcium-activated chloride channel (CaCC) and cystic fibrosis transmembrane conductance regulator (CFTR) in both HT-29 cells and mouse colons, but had no effects on the activity of the Na⁺-K⁺ ATPase or K⁺ channels. In in vivo experiments, the administration of plumbagin reduced both Escherichia coli heat-stable enterotoxin (STa)- and cholera toxin (CT)-induced intestinal fluid secretion. In neonatal mouse models of CT- and rotavirus infection-induced diarrhea, 0.4 µg plumbagin inhibited secretory diarrhea by >40% and 50%, respectively, without affecting intestinal epithelial integrity or the rotaviral infection. In addition, plumbagin exerted inhibitory effects on the vasoactive intestinal peptide (VIP)-, prostaglandin E2 (PGE2)-, and 5-hydroxytryptamine (5-HT)-stimulated Cl⁻ currents. In the evaluations of intestinal motility, plumbagin significantly delayed intestinal motility and inhibited intestinal smooth muscle contractility without an evident impact on contractive frequency. Collectively, our results indicate that plumbagin inhibits both Ca²⁺- and cAMP-activated Cl⁻ channels, accounting for the mechanisms of plumbagin inhibition of chloride secretion and intestinal motility. Thus, plumbagin can be a lead compound in the treatment of CT-induced, Traveler’s, and rotaviral diarrhea, as well as other types of secretory diarrhea that result from excessive intestinal fluid secretion and increased intestinal peristalsis.

Maduramicin inactivation of Akt impairs autophagic flux leading to accumulated autophagosomes-dependent apoptosis in skeletal myoblast cells

It has been clinically documented that maduramicin (Mad), a polyether ionophore antibiotic widely used in the control of coccidiosis in poultry worldwide, can elicit skeletal muscle degeneration, heart failure, and even death in animals and humans, if improperly used. Here, we show that Mad induced apoptosis dose-dependently, which was associated with impaired autophagic flux in skeletal myoblast (C2C12 and L6) cells. This is supported by the findings that Mad treatment resulted in increase of autophagosomes with a concomitant elevation of LC3-II and p62 in the cells. Also, Mad increased co-localization of mCherry and GFP tandem-tagged LC3 puncta in the cells, suggesting a blockage of autophagic flux. Furthermore, addition of chloroquine (CQ) strengthened the basic and Mad-enhanced LC3-II and p62 levels, autophagosome formation and cell apoptosis, whereas pretreatment with rapamycin alleviated the effects in the cells exposed to Mad. Moreover, we noticed that Mad treatment inactivated Akt dose-dependently. Inhibition of Akt with inhibitor X potentiated Mad-induced decrease in phosphorylated Akt, and increases in LC3-II and p62 levels, autophagosome formation and cell apoptosis, whereas ectopic expression of constitutively active Akt rendered resistance to these events. Collectively, these results indicate that Mad inactivation of Akt impairs autophagic flux leading to accumulated autophagosomes-dependent apoptosis in skeletal myoblast cells. Our findings suggest that manipulation of Akt activity to improve autophagic flux is a promising strategy against Mad-induced myotoxicity.

Molecular pathways related to the control of proliferation and cell death in 786-O cells treated with plumbagin

Plumbagin (PLB) is a phytochemical being used for centuries in traditional medicines. Recently, its capacity to inhibit the development of human tumors has been observed, through the induction of apoptosis, cell cycle arrest, and inhibition of angiogenesis and metastasis. Here we evaluated the mechanism of action of PLB in the kidney adenocarcinoma 786-O cell line, which are metabolizing cells important for toxicology studies. After the treatment with PLB, we observed increased apoptosis and cell cycle arrest in S and G2/M phases, starting at 5 µM. In addition, PLB was cytotoxic, genotoxic and induced loss of cell membrane integrity. Regarding gene expression, treatment with 7.5 µM PLB reduced the amount of MTOR, BCL2 and ATM transcripts, and increased CDKN1A (p21) transcripts. Phosphorylation levels of yH2AX was increased and MDM2 protein level was reduced following the treatment with PLB, demonstrating its genotoxic effect. Our results suggest that PLB acts in molecular pathways related to the control of proliferation and cell death in 786-O cells.

3-Chloroplumbagin Induces Cell Death in Breast Cancer Cells Through MAPK-Mediated Mcl-1 Inhibition

Resistance acquired toward anti-cancer agents is a significant drawback in breast cancer therapy. A key factor contributing to drug resistance is apoptosis suppression associated with the upregulation of anti-apoptotic Bcl-2 family proteins. Specifically, the anti-apoptotic Mcl-1 protein has been shown to play a significant role in drug resistance, making it an important therapeutic target. The present study aimed at determining the antiproliferative activity of 3-chloroplumbagin (ChPL), a naphthoquinone derived from a Dionaea sp., toward breast cancer cells and examining the involvement of Mcl-1 inhibition in ChPL-induced cell death. The results showed that ChPL inhibited breast cancer cell proliferation and induced apoptosis through the intrinsic pathway through down-regulation of anti-apoptotic Bcl-2 family proteins. The induction of apoptosis by ChPL was found to be mediated through MAP kinase signaling inhibition. ChPL inhibited the phosphorylation of MEK and ERK proteins in breast cancer cells, and increased apoptosis induction in cells with reduced ERK expression. Furthermore, ERK silencing decreased the expression of Mcl-1 in ChPL-treated cells. The results of this research indicate that ChPL induces apoptosis in breast cancer cells through MAPK-mediated Mcl-1 inhibition, suggesting further research into its potential in breast cancer treatment.

Novel imidazo[1,2-a]pyridine inhibits AKT/mTOR pathway and induces cell cycle arrest and apoptosis in melanoma and cervical cancer cells

The present study aimed to investigate the anti-cancer activity of imidazo[1,2-a]pyridine 5–7 in the A375 and WM115 melanoma and HeLa cervical cancer cell lines. The viability of cancer cells was analyzed by the MTT assay. Apoptosis was quantified by flow cytometry following staining of the cells with AnnexinV/propidium iodide (PI). The cell cycle was evaluated by flow cytometry after staining of cells with PI. The three compounds inhibited the proliferation of all cells for half maximal inhibitory concentration ranging from 9.7 to 44.6 µM following 48-h treatment. In addition, all cancer cells were more sensitive to compound 6 compared with the other compounds. Treatment with compound 6 induced G₂/M cell cycle arrest and a significant increased level of intrinsic apoptosis in all tested cells. Furthermore, compound 6 reduced the levels of phospho (p)-protein kinase B and p-mechanistic target of rapamycin, and increased levels of the cell cycle inhibitors p53 and p21 and of the apoptosis-associated proteins BCL2 associated X protein and active caspase-9. Silencing p53 in A375 melanoma cells reduced compound 6-induced apoptosis, which suggested that compound 6 may induce p53-partially mediated apoptosis. These results demonstrated that imidazo[1,2-a]pyridines 5–7 are potential effective compounds in the treatment of melanoma and cervical cancers.

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.

Plumbagin Increases Paclitaxel-Induced Cell Death and Overcomes Paclitaxel Resistance in Breast Cancer Cells through ERK-Mediated Apoptosis Induction

ERK is a component of mitogen-activated protein kinases that controls a range of cellular processes including cell proliferation and survival. The upregulation of ERK has been associated with apoptosis inhibition in response to various stimuli including chemotherapeutic agents. Research has suggested that the upregulation of ERK signaling by the anticancer agent paclitaxel leads to acquired resistance of cells to this compound. The presented research focused on determining the role of plumbagin, a naturally derived naphthoquinone, in the sensitization of breast cancer cells to paclitaxel-induced cell death and the involvement of ERK signaling in this process. The results of the study indicated that plumbagin increases the sensitivity of breast cancer cells to paclitaxel. Moreover, a synergistic effect between plumbagin and paclitaxel was observed. Plumbagin was shown to decrease levels of phosphorylated ERK in breast cancer cells and abrogated paclitaxel-induced ERK phosphorylation. The role of ERK in plumbagin-mediated sensitization of breast cancer cells to paclitaxel was shown through the enhancement of the synergistic effect between compounds in cells with decreased ERK expression. Furthermore, plumbagin reduced p-ERK levels in paclitaxel-resistant breast cancer cells and resensitized paclitaxel-resistant cells to this compound. These results imply that plumbagin inhibits ERK activation in breast cancer cells, which plays a role in the sensitization of cells to paclitaxel-induced cell death.

Plumbagin inhibits amyloid-β-induced neurotoxicity: regulation of oxidative stress and nuclear factor erythroid 2-related factor 2 activation

β-Amyloid (Aβ) species probably exert neurotoxic effects in Alzheimer's disease. In the present study, the effect of antioxidant plumbagin was tested against Aβ25-35-induced neurotoxicity in the SH-SY5Y cell line. Cell viability was determined using an MTT assay. Antioxidant status was analyzed through antioxidant enzyme activities, nuclear factor erythroid 2-related factor 2 (Nrf-2), and its downstream protein expressions. Inflammatory response was determined through nuclear factor-κB (NF-κB) pathway and cytokine expressions. Aβ25-35 showed a decrease in cell viability in a concentration-dependent manner. The IC50 value was found to be 17 µM. Pretreatment with plumbagin prevented Aβ25-35-induced toxicity by improving the cell viability up to 96%. Plumbagin inhibited Aβ25-35-induced oxidative stress by decreasing reactive oxygen species and lipid peroxidation. Aβ25-35-induced redox imbalance caused decreased Nrf-2 expression, with downregulation Nrf-2 target proteins heme oxygenase 1 and NAD(P)H dehydrogenase (quinone 1) during Aβ25-35 treatment. However, plumbagin improved the antioxidant defense system by increasing Nrf-2 expression with concomitant upregulation in heme oxygenase 1 and NAD(P)H dehydrogenase (quinone 1). Aβ25-35 induced inflammatory response through upregulated NF-κB, cyclooxygenase-2, and inducible nitric oxide synthase levels. Plumbagin exerted anti-inflammatory effects by decreasing NF-κB, cyclooxygenase-2, and inducible nitric oxide synthase levels. Aβ25-35-induced increases in proinflammatory cytokine (interleukin-8, interleukin-6, and monocyte chemoattractant protein-1) expressions were suppressed by plumbagin pretreatment. Altogether, the present study indicates that plumbagin prevents redox status and inflammatory activation during Aβ25-35-induced toxicity by modulating the antioxidant defense system and Nrf-2 signaling.

Cell Suspension Culture of Plumbago europaea L. Towards Production of Plumbagin

BACKGROUND

Plumbagin is as an important bioactive secondary metabolite found in the roots of Plumbago spp. The only one species, Plumbago europaea L., grows wild in Iran. The therapeutic use of plumbagin is limited due to its insufficient supply from the natural sources as the plants grow slowly and take several years to produce quality roots.

OBJECTIVES

To develop an efficient protocol for the establishment of callus and cell suspension cultures of P. europaea and to evaluate production of plumbagin in callus and cell suspension cultures of P. europaea for the first time.

MATERIAL AND METHODS

Stems and leaves explants were cultured on agar solidified (7% w/v) MS media, supplemented with different combination of 2, 4-D and Kin or 6-Benzylaminopurin (BA) for callus induction. The rapid growing calli were cultured in liquid Murashige and Skoog (MS) media in agitated condition for establishing cell suspension cultures of P. europaea. Moreover, the effects of light and dark conditions on the cell growth, cell viability and plumbagin production in cell suspension cultures of P. europaea were assessed.

RESULTS

Friable calli were successfully induced using stem segments of P. europaea in semisolid MS medium supplemented with 1 mg.L-1 2, 4-Dichlorophenoxy acetic acid (2, 4-D) and 0.5 mg.L-1of kinetin (Kin). Optimal cell growth was obtained when the cells were grown in MS liquid media supplemented with 1 mg.L-1 2, 4-D and 0.5 mg.L-1 kinetin with an initial cell density of ~3×105 cells per ml incubated in the dark at 25 ± 1 °C. Growth curve revealed that the maximum cell growth rate (14.83×105 cells per ml) achieved on the day 18 and the highest plumbagin content (0.9 mg.g-1 Dry Cell Weight (DCW)) in the cells was obtained at the late exponential phase under dark condition which determined by High Performance Liquid Chromatography (HPLC) technique. Based on the obtained results, cell viability remained around 82.73% during the 18 days of cell culture in darkness. These suspension cultures showed continuous and stable production of plumbagin.

CONCLUSIONS

Our study suggests that cell suspension cultures of P. europaea represent an effective system for biosynthesis and production of plumbagin as a valuable bioactive compound.

Influence of copper (I) nicotinate complex and autophagy modulation on doxorubicin-induced cytotoxicity in HCC1806 breast cancer cells

PURPOSE

Doxorubicin is regarded as the most therapeutic active agent available for triple-negative breast cancer (TNBC) treatment. However, the development of drug resistance and toxicity limits its effectiveness. Thus, developing novel strategies for TNBC treatment remains a significant challenge and doxorubicin-based combinations either by metal complexes (Copper I nicotinate complex) or with autophagy modulators could provide novel strategies and alternative strategies contributed to cancer cell death pathways, autophagy and apoptosis.

MATERIALS AND METHODS

The viability of HCC1806 TNBC cells and IC₅₀ values of Doxorubicin (DOX), Torin-1 (TOR), Chloroquine (CQ) and Copper (I) nicotinate complex (CNC) were assessed by MTT assay. ELISA was used for detecting microtubule-associated protein 1 light chain 3 (LC3) level. Real time PCR was used to determine (NBR1) gene expression. Cell cycle analysis and quantitative detection of acid vesicular organelles (AVOs) was performed by flow cytometry. TOR and CQ were used as autophagy modulators for induction and suppression of autophagy, respectively.

RESULTS

The half-maximal inhibition effect of TOR combination with DOX was revealed to the induction of autophagic cell death and apoptotic cell death. On the other hand, combination of CQ with DOX increased the growth inhibitory effect, induced accumulation of AVOs and suppressed apoptotic cell death. However, combination of CNC with DOX inhibited autophagy and induced cell cycle arrest.

CONCLUSION

Doxorubicin drug based combinations either with TOR, CQ or CNC could positively affect DOX effectiveness and reduce DOX doses applied on HCC1806 cells through modulation of autophagy.

Influenza M2 protein regulates MAVS-mediated signaling pathway through interacting with MAVS and increasing ROS production

Influenza A virus can evade host innate immune response that is involved in several viral proteins with complicated mechanisms. To date, how influenza A M2 protein modulates the host innate immunity remains unclear. Herein, we showed that M2 protein colocalized and interacted with MAVS (mitochondrial antiviral signaling protein) on mitochondria, and positively regulated MAVS-mediated innate immunity. Further studies revealed that M2 induced reactive oxygen species (ROS) production that was required for activation of macroautophagy/autophagy and enhancement of MAVS signaling pathway. Importantly, the proton channel activity of M2 protein was demonstrated to be essential for ROS production and antagonizing the autophagy pathway to control MAVS aggregation, thereby enhancing MAVS signal activity. In conclusion, our studies provided novel insights into mechanisms of M2 protein in modulating host antiviral immunity and uncovered a new mechanism into biology and pathogenicity of influenza A virus. Abbreviations: AKT/PKB: AKT serine/threonine kinase; Apo: apocynin; ATG5: autophagy related 5; BAPTA-AM: 1,2-Bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetrakis; BECN1: beclin 1; CARD: caspase recruitment domain; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CQ: chloroquine; DCF: dichlorodihyd-rofluorescein; DPI: diphenyleneiodonium; DDX58: DExD/H-box helicase 58; eGFP: enhanced green fluorescent protein; EGTA: ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid; ER: endoplasmic reticulum; hpi: hours post infection; IAV: influenza A virus; IFN: interferon; IP: immunoprecipitation; IRF3: interferon regulatory factor 3; ISRE: IFN-stimulated response elements; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAVS: mitochondrial antiviral signaling protein; MMP: mitochondrial membrane potential; MOI, multiplicity of infection; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; NC: negative control; NFKB/NF-κB: nuclear factor kappa B; PI3K: class I phosphoinositide 3-kinase; RLR: RIG-I-like-receptor; ROS: reactive oxygen species; SEV: sendai virus; TM: transmembrane; TMRM: tetramethylrhodamine methylester; VSV: vesicular stomatitis virus.

Emerging role of plumbagin: Cytotoxic potential and pharmaceutical relevance towards cancer therapy

Plumbagin is a naphthoquinone derived yellow crystalline phytochemical. Plumbagin has a wide range of biological effects including cytotoxicity against cancer cells both in vitro and in vivo. Due to the pleiotropic nature of plumbagin, it shows the anticancer effect by targeting several molecular mechanisms including apoptosis and autophagic pathways, cell cycle arrest, anti-angiogenic pathways, anti-invasion and anti-metastasis pathways. Among many signaling pathways the key regulatory genes regulated by plumbagin are NF-kβ, STAT3, and AKT, etc. Plumbagin is also a potent inducer of ROS, suppressor of cellular glutathione, and causes DNA strand break by oxidative DNA base damages. In vivo studies suggested that plumbagin significantly reduces the tumor weight and volume in dose-dependent manner without any side effects in tested model organisms. Another exciting aspect of plumbagin is the ability to re-sensitize the chemo and radioresistant cancer cells when used in combination or alone. Nano encapsulation of plumbagin overcomes the poor water solubility and bioavailability obstacles, enhancing the pharmaceutical relevance with better therapeutic efficacy. Moreover, plumbagin can be introduced as a future phytotherapeutic anticancer drug after fully satisfied preclinical and clinical trials.

Afrocyclamin A, a triterpene saponin, induces apoptosis and autophagic cell death via the PI3K/Akt/mTOR pathway in human prostate cancer cells

BACKGROUND

Afrocyclamin A, an oleanane-type triterpene saponin, was isolated from Androsace umbellata which used as a traditional herbal medicine.

PURPOSE

This study aimed to explore the anticancer activity of afrocyclamin A on human prostate cancer cells in vitro as well as in vivo.

METHODS

Cytotoxicity, cell cycle distribution, apoptosis, and autophagic cell death were measured following exposure to afrocyclamin A. In vivo antitumor activity of afrocyclamin A was assessed in a xenograft model. The protein levels of p-Akt, p-mTOR, Bax, Bcl-2, caspase-3, and caspase-9 were quantified using western blot analysis.

RESULTS

In DU145 cells, afrocyclamin A increased cytotoxicity, caused changes in cell morphology, and induced sub-G0/G1 phase indicating increased apoptosis. Afrocyclamin A robustly induced autophagic cell death as demonstrated by the conversion of LC3B-I to LC3B-II, and the formation of autophagic vacuoles as revealed by western blot analysis and fluorescence staining, respectively. Afrocyclamin A also inhibited the phosphorylation of PI3K, Akt, and mTOR, suggesting their role in afrocyclamin A induced cell death. In addition, afrocyclamin A inhibited cell migration and invasion in concentration and time-dependent manners. In an in vivo xenograft model, afrocyclamin A inhibited the growth of DU145 cells.

CONCLUSION

Afrocyclamin A has anticancer activity via the PI3K/Akt/mTOR pathway, which leads to cell death.

New quinoline/chalcone hybrids as anti-cancer agents: Design, synthesis, and evaluations of cytotoxicity and PI3K inhibitory activity

A series of quinoline-chalcone hybrids was designed as potential anti-cancer agents, synthesized and evaluated. Different cytotoxic assays revealed that compounds experienced promising activity. Compounds 9i and 9j were the most potent against all the cell lines tested with IC₅₀ = 1.91-5.29 µM against A549 and K-562 cells. Mechanistically, 9i and 9j induced G₂/M cell cycle arrest and apoptosis in both A549 and K562 cells. Moreover, all PI3K isoforms were inhibited non selectively with IC₅₀s of 52-473 nM when tested against the two mentioned compounds with 9i being most potent against PI3K-γ (IC₅₀ = 52 nM). Docking of 9i and 9j showed a possible formation of H-bonding with essential valine residues in the active site of PI3K-γ isoform. Meanwhile, Western blotting analysis revealed that 9i and 9j inhibited the phosphorylation of PI3K, Akt, mTOR, as well as GSK-3β in both A549 and K562 cells, suggesting the correlation of blocking PI3K/Akt/mTOR pathway with the above antitumor activities. Together, our findings support the antitumor potential of quinoline-chalcone derivatives for NSCLC and CML by inhibiting the PI3K/Akt/mTOR pathway.

Autophagy and its potent modulators from phytochemicals in cancer treatment

Autophagy is a ubiquitous catabolic process by which damaged or harmful intracellular components are delivered to the lysosomes for self-digestion and recycling. It is critical in cancer treatment. Therapy-induced autophagy predominantly acts as a pro-survival mechanism, but progressive autophagy can lead to non-apoptotic cell death, also known as autophagic cell death. Plants or herbs contain various natural compounds that are widely used in the treatment of many types of malignancies. Emerging evidence indicates that phytochemicals targeting the autophagic pathway are promising agents for cancer treatment. However, these compounds play different roles in autophagy. In this review, we discussed the role of autophagy in cancer development and therapy, and focussed on elucidating the anti-cancer activities of autophagic modulators, especially phytochemicals. Notably, we described a novel premise that the dynamic role of phytochemicals should be evaluated in regulation of autophagy in cancer.

Indirubin-3'-oxime suppresses human cholangiocarcinoma through cell-cycle arrest and apoptosis

Cholangiocarcinoma (CCA) is one of the most serious of all cancers and a major public health problem. CCA is an extremely invasive cancer, and the survival rate for CCA patients is only 24 months after diagnosis. Although surgery and chemotherapy can extend the survival rate to 5 years, < 20-40% of CCA patients will survive this long; therefore, it is crucial to discover an effective chemotherapeutic agent for CCA. Indirubin-3'-oxime (I3O), a derivative of indirubin, has been shown to suppress cell proliferation and induce cell-cycle arrest and cell apoptosis in various human cancers. In this study, four human CCA cell lines-NOZ, HuCCT1, OCUG-1, and OZ-were used to evaluate the anticancer properties of I3O. Cell viability, cell-cycle arrest, and apoptosis were assessed using Western blotting, immunofluorescence, and flow cytometry analysis. The data show that I3O treatment can inhibit cell proliferation and induce cell-cycle arrest, and caspase-dependent apoptosis in CCA cells. These findings suggest that I3O could suppress tumor growth by regulating the cell cycle and inducing apoptosis, and is a potential therapeutic agent for treating human CCA.

A simple robust method of synthesis of copper-silver core-shell nano-particle: evaluation of its structural and chemical properties with anticancer potency

A simple method of synthesis of a stable bimetallic copper-silver nano-particle (CuAg-NP) was developed by successive reduction of Cu(NO₃)₂ and AgNO₃, using hydrazine hydrate as the reducing agent and gelatin and poly-vinyl pyrrolidone (PVP) as the capping agents. The round-shaped particles were of a core-shell structure with a core of Cu⁰ atoms surrounded by a shell of Ag⁰ atoms. The size and the mol. wt. of the NPs were (100 ± 10) nm and (820 ± 157) Kd, respectively; the particles were crystalline in nature and 90% of the precursors Cu(NO₃)₂ and AgNO₃ were converted to the NPs. The particles were more toxic to cancer cells than normal cells; the dose of the NPs (4-5 μg ml^-1), that killed about 75% of the different human cancer cell lines viz, HepG2 (liver cancer), A549 (lung cancer) and AGS (stomach cancer), killed only about 22.5% of the normal cell lines viz, WRL68 (liver) and WI38 (lung). Therefore, the NP may be developed as a potent anticancer drug in future. The more detailed study on the cytotoxicity of the CuAg-NP on the HepG2 cell line revealed that the particles caused cell cycle arrest in a G2/M phase, depolarization of mitochondrial membrane potential, translocation of phosphatidylserine residues from inner to outer leaflets of cell membrane and DNA degradation; these phenomena confirmed that the NP-induced cell death was apoptotic in nature.