Nimbolide Induces ROS-Regulated Apoptosis and Inhibits Cell Migration in Osteosarcoma

Arecoline induces neurotoxicity in HT22 cells via the promotion of endoplasmic reticulum stress and downregulation of the Nrf2/HO-1 pathway

Arecoline, the predominant bioactive substance extracted from areca nut (AN), is the world's fourth most frequently used psychoactive material. Research has revealed that chewing AN can affect the central nervous system (CNS) and may lead to neurocognitive deficits that are possibly linked to the action of arecoline. However, the mechanism behind the neurotoxicity caused by arecoline remains unclear. This study aimed to investigate the neurotoxic effects of arecoline and its underlying mechanism. The results showed that arecoline caused cytotoxicity against HT22 cells in a dose-dependent manner and induced apoptosis by upregulating the expression of pro-apoptotic caspase and Bcl-2 family proteins. Furthermore, arecoline escalated intracellular reactive oxygen species (ROS) levels and Ca2+ concentration with increasing doses, thereby motivating endoplasmic reticulum stress (ERS) and ERS-associated apoptotic protein expression. Additionally, the study found that arecoline attenuates intracellular antioxidant defense by inhibiting the translocation of NF-E2-related factor-2 (Nrf2) into the nucleus and decreasing downstream Heme oxygenase-1 (HO-1) levels. The specific inhibitor Sodium 4-phenylbutyrate (4-PBA) can dramatically attenuate arecoline-mediated cell apoptosis and ERS-associated apoptotic pathway expression by blocking ERS. The antioxidant N-Acetylcysteine (NAC) also effectively reverses the arecoline-mediated increase of ERS-related apoptotic pathway protein levels by scavenging intracellular ROS accumulation. In conclusion, this study suggests that arecoline induces neurotoxicity in HT22 cells via ERS mediated by oxidative stress- and Ca2+ disturbance, as well as by downregulation of the Nrf2/HO-1 pathway.

Limonoids from neem (Azadirachta indica A. Juss.) are potential anticancer drug candidates

Neem (Azadirachta indica A. Juss.), a versatile evergreen tree recognized for its ethnopharmacological value, is a rich source of limonoids of the triterpenoid class, endowed with potent medicinal properties. Extracts of neem have been documented to display anticancer effects in diverse malignant cell lines as well as in preclinical animal models that has largely been attributed to the constituent limonoids. Of late, neem limonoids have become the cynosure of research attention as potential candidate agents for cancer prevention and therapy. Among the various limonoids found in neem, azadirachtin, epoxyazadiradione, gedunin, and nimbolide, have been extensively investigated for anticancer activity. Azadirachtin, a potent biodegradable pesticide, exhibits profound antiproliferative effects by preventing mitotic spindle formation and cell division. The antiproliferative activity of gedunin has been demonstrated to be mediated primarily via inhibition of heat shock protein90 and its client proteins. Epoxyazadiradione inhibits pro-inflammatory and kinase-driven signaling pathways to block tumorigenesis. Nimbolide, the most potent cytotoxic neem limonoid, inhibits the growth of cancer cells by regulating the phosphorylation of keystone kinases that drive oncogenic signaling besides modulating the epigenome. There is overwhelming evidence to indicate that neem limonoids exert anticancer effects by preventing the acquisition of hallmark traits of cancer, such as cell proliferation, apoptosis evasion, inflammation, invasion, angiogenesis, and drug resistance. Neem limonoids are value additions to the armamentarium of natural compounds that target aberrant oncogenic signaling to inhibit cancer development and progression.

Nimbolide Exhibits Potent Anticancer Activity Through ROS-Mediated ER Stress and DNA Damage in Human Non-small Cell Lung Cancer Cells

The non-small cell lung cancer (NSCLC) accounts for about 85% of all lung cancers. It is usually diagnosed at an advanced stage with poor prognosis. Nimbolide (NB), a terpenoid limonoid isolated from the flowers and leaves of neem tree, possesses anticancer properties in various cancer cell lines. However, the underlying mechanism of its anticancer effect on human NSCLC cells remains unclear. In the present study, we investigated the effect of NB on A549 human NSCLC cells. We found that NB treatment inhibits A549 cells colony formation in a dose-dependent manner. Mechanistically, NB treatment increases cellular reactive oxygen species (ROS) level, leading to endoplasmic reticulum (ER) stress, DNA damage, and eventually induction of apoptosis in NSCLC cells. Furthermore, all these effects of NB were blocked by pretreatment with antioxidant glutathione (GSH), the specific ROS inhibitor. We further knockdown CHOP protein by siRNA markedly reduced NB-induced apoptosis in A549 cells. Taken together, our findings reveal that NB is an inducer of ER stress and ROS; these findings may contribute to increasing the therapeutic efficiency of NSCLC.

Nimbolide-based nanomedicine inhibits breast cancer stem-like cells by epigenetic reprogramming of DNMTs-SFRP1-Wnt/β-catenin signaling axis

Triple-negative breast cancer (TNBC) harbors a high percentage of breast cancer stem-like cells (BCSCs) that significantly contribute to poor prognosis, metastasis, and relapse of the disease. Thus, targeting BCSCs could be a promising approach to combat TNBC. In this context, we investigated nimbolide (Nim), a limonoid triterpenoid that has potent anticancer properties, but poor pharmacokinetics and low bioavailability limit its therapeutic application. So, to enhance the therapeutic potential of Nim, Nim-encapsulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (Nim NPs) were formulated and the anticancer stem cell (CSC) effects evaluated in vitro and in vivo. In vitro studies suggested that Nim NPs significantly inhibited several inherent characteristics of BCSCs, such as stemness, self-renewability, chemoresistance, epithelial-to-mesenchymal transition (EMT), and migration in comparison to native Nim. Next, the mechanism behind the anti-CSC effect of Nim was explored. Mechanistically, we found that Nim epigenetically restores tumor suppressor gene secreted frizzled-related protein 1 (SFRP1) expression by downregulating DNA methyltransferases (DNMTs), leading to Wnt/β-catenin signaling inhibition. Further, in vivo results demonstrated that Nim NPs showed enhanced anti-tumor and anti-metastatic effects compared to native Nim in two preclinical models without any systemic toxicity. Overall, these findings provide proof of concept that Nim-based phytonanomedicine can inhibit BCSCs by epigenetic reprogramming of the DNMTs-SFRP1-Wnt/β-catenin signaling axis.

Implications of reactive oxygen species in lung cancer and exploiting it for therapeutic interventions

Lung cancer is the second (11.4%) most commonly diagnosed cancer and the first (18%) to cause cancer-related deaths worldwide. The incidence of lung cancer varies significantly among men, women, and high and low-middle-income countries. Air pollution, inhalable agents, and tobacco smoking are a few of the critical factors that determine lung cancer incidence and mortality worldwide. Reactive oxygen species are known factors of lung carcinogenesis resulting from the xenobiotics and their mechanistic paths are under critical investigation. Reactive oxygen species exhibit dual roles in cells, as a tumorigenic and anti-proliferative factor, depending on spatiotemporal context. During the precancerous state, ROS promotes cancer origination through oxidative stress and base-pair substitution mutations in pro-oncogenes and tumor suppressor genes. At later stages of tumor progression, they help the cancer cells in invasion, and metastases by activating the NF-kB and MAPK pathways. However, at advanced stages, when ROS exceeds the threshold, it promotes cell cycle arrest and induces apoptosis in cancer cells. ROS activates extrinsic apoptosis through death receptors and intrinsic apoptosis through mitochondrial pathways. Moreover, ROS upregulates the expression of beclin-1 which is a critical component to initiate autophagy, another form of programmed cell death. ROS is additionally involved in an intermediatory step in necroptosis, which catalyzes and accelerates this form of cell death. Various therapeutic interventions have been attempted to exploit this cytotoxic potential of ROS to treat different cancers. Growing body of evidence suggests that ROS is also associated with chemoresistance and cancer cell immunity. Considering the multiple roles of ROS, this review highlights the exploitation of ROS for various therapeutic interventions. However, there are still gaps in the literature on the dual roles of ROS and the involvement of ROS in cancer cell immunity and therapy resistance.

Naringenin induces endoplasmic reticulum stress-mediated cell apoptosis and autophagy in human oral squamous cell carcinoma cells

Human oral squamous cell carcinoma (OSCC) has been one of the most common oral cancers owing to high percentage of betel nuts chewers, smokers, and alcohol consumption. With current treatment strategies in OSCC, more than half patients relapse and develop distant metastases with poor prognosis. To overcome the incident, OSCC poses a challenge in current therapies and treatments. Naringenin, a natural flavonoid, has been noted for antitumor effects on various types of cancers; however, the effects of naringenin on OSCC remain bias. In this study, naringenin demonstrated the potential multifunction in human OSCC cells not only leading to cell apoptosis, but also alternating the general function of autophagy, serving as pro-survival mechanism by inducing the endoplasmic reticulum (ER) stress signaling through intracellular reactive oxygen species (ROS) production. In the process of programmed cell death, naringenin induced apoptotic signaling through caspase-cascade, mitochondrial dysfunction, and ER stress by aberrance of Ca²⁺ release. In contrast, under the presence of naringenin, the pro-survival has been altered into pro-death to activate the caspases-mediated apoptosis achieving cell death. The cross-function of apoptosis and autophagy has demonstrated the effect of naringenin-induced intracellular ROS activity in OSCC cells. Therefore, this study found that the effect of naringenin induces intracellular ROS to trigger programmed cell death and ER stress through the mechanisms of apoptosis and autophagy in human oral squamous carcinoma. PRACTICAL APPLICATIONS: This study revealed that naringenin debilitated the OSCC cell viability via the intracellular ROS production, ER stress, and autophagy, leading to cell apoptosis. Based on these studies and findings, naringenin provided an antitumor effect as a novel natural compound to improve the current therapies in OSCC.

Nimbolide retards T cell lymphoma progression by altering apoptosis, glucose metabolism, pH regulation, and ROS homeostasis

Nimbolide is reported as one of the potential anticancer candidates of the neem tree (Azadirachta indica A. Juss). The cytotoxic action of nimbolide has been well reported against a wide number of malignancies, including breast, prostate, lung, liver, and cervix cancers. Interestingly, only a few in vivo studies conducted on B cell lymphoma, glioblastoma, pancreatic cancer, and buccal pouch carcinoma have shown the in vivo antitumor efficacy of nimbolide. Therefore, it is highly needed to examine the in vivo antineoplastic activity of nimbolide on a wide variety of cancers to establish nimbolide as a promising anticancer drug. In the present study, we investigated the tumor retarding action of nimbolide in a murine model of T cell lymphoma. We noticed significantly augmented apoptosis in nimbolide- administered tumor-bearing mice, possibly due to down-regulated expression of Bcl2 and up-regulated expression of p53, cleaved caspase-3, Cyt c, and ROS. The nimbolide treatment-induced ROS production by suppressing the expression of antioxidant regulatory enzymes, namely superoxide dismutase and catalase. In addition, nimbolide administration impaired glycolysis and pH homeostasis with concomitant inhibition of crucial glycolysis and pH regulatory molecules such as GLUT3, LDHA, MCT1, and V-ATPase, CAIX and NHE1, respectively. Taken together, the present investigation provides novel insights into molecular mechanisms of nimbolide inhibited T cell lymphoma progression and directs the utility of nimbolide as a potential anticancer therapeutic drug for the treatment of T cell lymphoma.

Surfactin induces ER stress-mediated apoptosis via IRE1-ASK1-JNK signaling in human osteosarcoma

Osteosarcoma, one of primary bone tumor in children and young adults, has poor prognosis and drug resistances to chemotherapy. In order to reinforce the conventional therapies and antagonize the osteosarcoma in patients, a novel strategy is required for developing a new treatment. In this study, surfactin, a natural product from Bacillus subtilis, showed the efficiency of cell death in osteosarcoma, but not in normal cells. Surfactin triggers ER stress mechanism by promoting the aberrant Ca²⁺ release from ER lumen and ER-signaling to mitochondrial dysfunction following caspases activation mediating cell apoptosis. Surfactin-induced ER stress not only upregulated of glucose-regulated protein 78/94 and IRE1-ASK1-JNK pathway but also leading to calpains and Bcl-2 proteins family involving the release of cytochrome c. The releases into cytosol trigger the cleavage of caspase-9 and caspase-3 to induce cell apoptosis. In this study, surfactin demonstrated the potential functions to trigger the ER stress, ER stress-associated IRE1-ASK1-JNK signaling pathway, mitochondrial dysfunction, and caspase activations leading to programmed cell apoptosis. Importantly, implicating the signaling pathway that regulates the connection between ER stress and mitochondrial dysfunction causing apoptosis associated with surfactin. These results indicated a potential application of surfactin strengthen current conventional therapies.

In vitro antibacterial activity of nimbolide against Helicobacter pylori

ETHNOPHARMACOLOGICAL RELEVANCE

Nimbolide is one of hundreds of phytochemicals that have been identified within the neem tree (Azadirachta indica A. Juss). As an evergreen tree native to the Indian subcontinent, components of the neem tree have been used for millennia in traditional medicine to treat dental, gastrointestinal, urinary tract, and blood-related ailments, ulcers, headaches, heartburn, and diabetes. In modern times, natural oils and extracts from the neem tree have been found to have activities against a variety of microorganisms, including human pathogens.

AIM OF THE STUDY

Helicobacter pylori, a prevalent gastric pathogen, shows increasing levels of antibiotic resistance. Thus, there is an increasing demand for novel therapeutics to treat chronic infections. The in vitro activity of neem oil extract against H. pylori was previously characterized and found to be bactericidal. Given the numerous phytochemicals found in neem oil extract, the present study was designed to define and characterize specific compounds showing bactericidal activity against H. pylori.

MATERIALS AND METHODS

Azadirachtin, gedunin, and nimbolide, which are all common in neem extracts, were tested for antimicrobial activity; the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for nine strains of H. pylori. The specific properties of nimbolide were further characterized against H. pylori strain G27. Bactericidal kinetics, reversibility, effectiveness at low pH, and activity under bacteriostatic conditions were examined. The hemolytic activity of nimbolide was also measured. Finally, neem oil extract and nimbolide effectiveness against H. pylori biofilms were examined in comparison to common antibiotics used to treat H. pylori infection.

RESULTS

Nimbolide, but not azadirachtin or gedunin, was effective against H. pylori; MICs and MBCs against the nine tested strains ranged between 1.25-5 μg/mL and 2.5-10 μg/mL, respectively. Additionally, neem oil extract and nimbolide were both effective against H. pylori biofilms. Nimbolide exhibited no significant hemolytic activity at biologically relevant concentrations. The bactericidal activity of nimbolide was time- and dose-dependent, independent of active H. pylori growth, and synergistic with low pH. Furthermore, nimbolide-mediated H. pylori cell death was irreversible after exposure to high nimbolide concentrations (80 μg/mL, after 2 h of exposure time and 40 μg/mL after 8 h of exposure).

CONCLUSIONS

Nimbolide has significant bactericidal activity against H. pylori, killing both free living bacterial cells as well as cells within a biofilm. Furthermore, the lack of hemolytic activity, synergistic activity at low pH and bactericidal properties even against bacteria in a state of growth arrest are all ideal pharmacological and biologically relevant properties for a potential new agent. This study underscores the potential of neem oil extract or nimbolide to be used as a future treatment for H. pylori infection.

Nimbolide, a Neem Limonoid, Inhibits Angiogenesis in Breast Cancer by Abrogating Aldose Reductase Mediated IGF-1/PI3K/Akt Signaling

Background & Objectives:

There is growing evidence to implicate the insulin/IGF-1R/PI3K/Akt signaling cascade in breast cancer development and the central role of aldose reductase (AR) in mediating the crosstalk between this pathway and angiogenesis. The current study was designed to investigate whether nimbolide, a neem limonoid, targets this oncogenic signaling network to prevent angiogenesis in breast cancer.

Methods:

Breast cancer cells (MCF-7, MDA-MB-231), EAhy926 endothelial cells, MDA-MB-231 xenografted nude mice, and tumour tissues from breast cancer patients were used for the study. Expression of AR and key players in IGF-1/PI3K/Akt signaling and angiogenesis was evaluated by qRT-PCR, immunoblotting, and immunohistochemistry. Molecular docking and simulation, overexpression, and knockdown experiments were performed to determine whether nimbolide targets AR and IGF-1R

Results:

Nimbolide inhibited AR with consequent blockade of the IGF-1/PI3K/Akt and HIF-1/VEGF signaling circuit by influencing the phosphorylation and intracellular localisation of key signaling molecules. Downregulation of DNMT-1, HDAC-6, miR-21, HOTAIR, and H19 with upregulation of miR-148a/miR-152 indicated that nimbolide regulates AR and IGF-1/PI3K/Akt signaling via epigenetic modifications. Coadministration of nimbolide with metformin and the chemotherapeutic drugs tamoxifen/cisplatin displayed higher efficacy than single agents in inhibiting IGF-1/PI3K/Akt/AR signaling. Grade-wise increases in IGF-1R and AR expression in breast cancer tissues underscore their value as biomarkers of progression.

Conclusions:

This study provides evidence for the anticancer effects of nimbolide in cellular and mouse models of breast cancer besides providing leads for new drug combinations. It has also opened up avenues for investigating potential molecules such as AR for therapeutic targeting of cancer.

Nimbolide inhibits 2D and 3D prostate cancer cells migration, affects microtubules and angiogenesis and suppresses B-RAF/p.ERK-mediated in vivo tumor growth

BACKGROUND

Prostate cancer (PCa) is the most prominent malignancy among men worldwide. PCa cells have a high tendency to metastasize to various distant organs, and this activity is the main cause of PCa mortality. Nimbolide is a promising phytochemical constituent of neem Azadirachta indica (Meliaceae). Previous studies showed that nimbolide exhibited potent anticancer activity however, its role against PCa tumorigenesis has not been fully elucidated.

PURPOSE

Our work aims to explore the role of nimbolide in regulating the essential tumor-associated processes involved in the metastatic cascade in PCa cells.

STUDY DESIGN

Cytotoxicity assay, wound healing and spheroid invasion assays, western blotting, immunofluorescence, tube-formation assay, in vivo and immunohistochemistry.

METHODS

The cytotoxicity of nimbolide towards PCa cell lines was assessed by resazurin assays. The cell mobility and migration of nimbolide-treated DU145 cells were determined by wound healing and spheroid invasion assays. Tubulin network was visualized using U2OS cells and DU145 cells. The effect of nimbolide on E-cadherin, β-catenin, acetylated α-tubulin and HDAC6 protein expressions levels were measured by Western blot. The potentiality of nimbolide to inhibit angiogenesis was revealed by HUVEC tube-formation assay. Nimbolide antitumor effect was studied in a syngeneic model of murine prostate cancer.

RESULTS

The current study indicated that nimbolide negatively affected the migratory and invasive capacity of DU145 prostate cancer cells in 2D and three-dimensional (3D) spheroid cultures. Interestingly, nimbolide induced downregulation of E-cadherin without any influence on the expression level of β-catenin. Additionally, we demonstrated that nimbolide influenced the microtubule network which was supported by the upregulation of acetylated α-tubulin and the reduction in HDAC6 protein. Moreover, the inhibitory effect of nimbolide on angiogenesis was clearly observed in HUVEC tube formation assay. In vivo experiments revealed the significant suppression of PCa growth and targeting of the B-RAF/p.ERK signaling pathway by nimbolide.

CONCLUSION

Our results showed that nimbolide inhibited 2D and 3D prostate cancer cells migration and downregulated E-cadherin protein expression, a marker for metastatic chemoresistance and tumor recurrence. Nimbolide stabilized the microtubules, combated angiogenesis and suppressed B.RAF/ERK-mediated in vivo tumor growth. Nimbolide may be considered as potential therapeutic agent for metastatic and advanced PCa patients and merits further investigations.

Nimbolide attenuated the inflammation in the liver of autoimmune hepatitis's mice through regulation of HDAC3

A chronic liver disease named autoimmune hepatitis (AIH) will carry elevated levels of inflammatory cytokines, but there is currently no effective treatment to cure it. Histone deacetylase 3 (HDAC3) takes an important position in regulating the expression of inflammatory genes. Nimbolide (NIB) is a limonoid extracted from the neem tree (Azadirachta indica) that has been found to be effective against many diseases, including cancer, scleroderma, and acute respiratory distress syndrome. Here, we investigated the protective effect of nimbolide on AIH liver. Mice and AML12 cells were employed to establish AIH model with liver antigen S100 and cell injury model of LPS, and then treated with different concentrations of nimbolide. After the successful establishment of the animal model and cell model, inflammatory cytokines of IL-1β, IL-6 and TNF-α as well as cellular signaling related to inflammation such as STAT3, IκB-α and NF-κB were examined. We observed for the first time about nimbolide can effectively inhibit inflammation in AIH mice's liver and AML12 cells by inhibiting HDAC3 expression. HDAC3 knocked down by siRNA in cells can also effectively alleviate the inflammation in AML12 cells, further confirming that HDAC3 plays an important role in the inflammation of liver cells. These results suggest nimbolide could be a potential new treatment for autoimmune hepatitis, and HDAC3 may become a new target for autoimmune hepatitis.

α-Mangostin Induces Apoptosis in Human Osteosarcoma Cells Through ROS-Mediated Endoplasmic Reticulum Stress via the WNT Pathway

α-mangostin has been confirmed to promote the apoptosis of MG-63 cells, but its specific pro-apoptosis mechanism in osteosarcoma (OS) remains further investigation. Here, we demonstrated that α-mangostin restrained the viability of OS cells (143B and Saos-2), but had little effect on the growth of normal human osteoblast. α-mangostin increased OS cell apoptosis by activating the caspase-3/8 cascade. Besides, α-mangostin induced endoplasmic reticulum (ER) stress and restrained the Wnt/β-catenin pathway activity. 4PBA (an ER stress inhibitor) or LiCl (an effective Wnt activator) treatment effectively hindered α-mangostin-induced apoptosis and the caspase-3/8 cascade. Furthermore, we also found that α-mangostin induced ER stress by promoting ROS production. And ER stress-mediated apoptosis caused by ROS accumulation depended on the inactivation of Wnt/β-catenin pathway. In addition, α-mangostin significantly hindered the growth of xenograft tumors, induced the expression of ER stress marker proteins and activation of the caspase-3/8 cascade, and restrained the Wnt/β-catenin signaling in vivo. In short, ROS-mediated ER stress was involved in α-mangostin triggered apoptosis, which might depended on Wnt/β-catenin signaling inactivation.

Nimbolide induces cell death in T lymphoma cells: Implication of altered apoptosis and glucose metabolism

Nimbolide is a tetranortriterpenoid derived from the leaves and flowers of Azadirachta indica (Neem). It exhibits anticancer activity against a variety of cancers by modulating various crucial features, including cell proliferation, apoptosis, and invasion and metastasis. More importantly, the cytotoxic effect of nimbolide has also been observed against T cell lymphoma, but the underlying mechanisms are still unexplored. So far, no study has been conducted to observe the effect of nimbolide on cancer cell metabolism. Therefore, the present investigation was designed to explore the molecular mechanisms of the antitumor potential of nimbolide against T cell lymphoma, a neoplastic disorder of thymic origin. In addition, we also unraveled the anti-glycolytic activity of nimbolide against T lymphoma cells with possible molecular mechanisms. Our results showed the cytotoxic action of nimbolide against three different cell lines of T cell lymphoma, namely Dalton's lymphoma, HuT-78, and J6. Nimbolide-induced apoptosis in T lymphoma cells by altering the level of reactive oxygen species, p53, Bcl2, Bax, and cytochrome c, with subsequent cleavage of caspase 3. Remarkably, nimbolide inhibited the expression of hypoxia-inducible factor-1α, glucose transporter 3, hexokinase II, and pyruvate dehydrogenase kinase 1, which led to the suppression of glycolysis with concomitant activation of oxidative phosphorylation. Hence, the results of the present investigation demonstrate that nimbolide exerts tumoricidal activity against T lymphoma cells via augmentation of apoptosis and reversal of altered cell metabolism. Thus, the present study provides a new insight for the therapeutic utilization of nimbolide against T cell lymphoma.

Nimbolide, a Neem Limonoid, Is a Promising Candidate for the Anticancer Drug Arsenal

Nimbolide, a major limonoid constituent of Azadirachta indica, commonly known as neem, has attracted increasing research attention owing to its wide spectrum of pharmacological properties, predominantly anticancer activity. Nimbolide is reported to exert potent antiproliferative effects on a myriad cancer cell lines and chemotherapeutic efficacy in preclinical animal tumor models. The potentiality of nimbolide to circumvent multidrug resistance and aid in targeted protein degradation broaden its utility in enhancing therapeutic modalities and outcome. Accumulating evidence indicates that nimbolide prevents the acquisition of cancer hallmarks such as sustained proliferation, apoptosis evasion, invasion, angiogenesis, metastasis, and inflammation by modulating kinase-driven oncogenic signaling networks. Nimbolide has been demonstrated to abrogate aberrant activation of cellular signaling by influencing the subcellular localization of transcription factors and phosphorylation of kinases in addition to influencing the epigenome. Nimbolide, with its ever-expanding repertoire of molecular targets, is a valuable addition to the anticancer drug arsenal.

Involvement of actin cytoskeletal modifications in the inhibition of triple-negative breast cancer growth and metastasis by nimbolide

Triple-negative breast cancers (TNBCs) are aggressive cancers, which currently do not have effective treatment options. Migration and establishment of metastatic colonies require dynamic cytoskeletal modifications characterized by polymerization and depolymerization of actin. Studies have demonstrated a direct molecular link between the integrin-focal adhesion kinase (FAK) pathway and cytoskeletal modifications. Nimbolide, a major bioactive compound present in neem leaves, shows promising anti-cancer effect on various cancers. In this study, we have demonstrated the growth and metastasis inhibitory potential of nimbolide on TNBC cells. Nimbolide inhibited cell proliferation, migratory, and invasive abilities of TNBC cells and also changed the shape of MDA-MB-231 cells, which is correlated with cytoskeletal changes including actin depolymerization. Furthermore, analysis revealed that integrins αV and β3, ILK, FAK, and PAK levels were downregulated by nimbolide. Even in cells where Rac1/Cdc42 was constitutively activated, nimbolide inhibited the formation of filopodial structures. Immunofluorescence analysis of phosphorylated p21 activated kinase (pPAK) showed reduced expression in nimbolide-treated cells. Nimbolide significantly reduced the metastatic colony formation in lung, liver, and brain of athymic nude mice. In conclusion, our data demonstrate that nimbolide inhibits TNBC by altering the integrin and FAK signaling pathway.

β-Elemonic acid inhibits the growth of human Osteosarcoma through endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP activation and Wnt/β-catenin signal suppression

BACKGROUND

Osteosarcoma (OS) is a significant threat to the lives of children and young adults. Although neoadjuvant chemotherapy is the first choice of treatment for OS, it is limited by serious side-effects and cancer metastasis. β-Elemonic acid (β-EA), an active component extracted from Boswellia carterii Birdw., has been reported to exhibit potential anti-inflammatory and anticancer activities. However, the anti-tumor effects and underlying mechanisms on OS as well as pharmacokinetic characteristics of β-EA remain unknown.

PURPOSE

This study was aimed to investigating the anti-tumor effects of β-EA on human OS, the underlying mechanisms, and the pharmacokinetic and tissue distribution characteristics.

STUDY DESIGN AND METHODS

Cell viability and colony formation assays were performed to determine the effect of β-EA cell on cell proliferation. Apoptosis rates, mitochondrial membrane potential and cell cycle features were analyzed by flow cytometry. qRT-PCR, Western blot, immunofluorescence and immunohistochemical assays were conducted to evaluate the expression levels of genes or proteins related to the pathways affected by β-EA in vitro and in vivo. Cell migration and invasion were evaluated in wound healing and Transwell chamber assays. The effects and pharmacokinetic characteristics of β-EA in vivo were evaluated by analyzing tumor suppression, pharmacokinetics and tissue distribution.

RESULTS

Explorations indicated that endoplasmic reticulum (ER) stress conditions provoked by β-EA activated the PERK/eIF2α/ATF4 branch of the unfolded protein reaction (UPR), stimulating C/EBP homologous protein (CHOP)-regulated apoptosis and inducing Ca²⁺ leakage leading to caspase-dependent apoptosis. Furthermore, β-EA induced G0/G1 cell cycle arrest and inhibited metastasis of HOS and 143B cells by attenuating Wnt/β-catenin signaling effects, which included decreased levels of p-Akt(Ser473), p-Gsk3β (Ser9), Wnt/β-catenin target genes (c-Myc and CyclinD1) along with a decline in nuclear β-catenin accumulation. The fast absorption, short elimination half-life, and linear pharmacokinetic characteristics of β-EA were also revealed. The distribution of β-EA was detected in the tumor and bone tissues.

CONCLUSIONS

Overall, both in vitro and in vivo investigations showed the potential of β-EA for the treatment of human OS. The pharmacokinetic profile and considerable distribution in the tumor and bone tissues warrant further preclinical or even clinical studies.

Resistin enhances angiogenesis in osteosarcoma via the MAPK signaling pathway

Over the last two decades, there have been no significant changes in patient outcomes in relation to the treatment of osteosarcoma, an aggressive malignant neoplasm. It is known that vascular endothelial growth factor-A (VEGF-A) plays a crucial role in angiogenesis and in osteosarcoma. Moreover, VEGF-A expression correlates with clinical stages of osteosarcoma. The adipokine resistin exhibits proinflammatory, proangiogenic and metastatic properties, and evidence suggests that resistin may serve as a prognostic biomarker linking obesity and inflammation to cancer. However, whether resistin has a role in osteosarcoma angiogenesis is unclear. This investigation shows that resistin promotes VEGF-A expression in human osteosarcoma cells and activates the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 signaling pathways, while ERK, JNK, and p38 inhibitors or their small interfering RNAs (siRNAs) inhibit resistin-induced VEGF-A expression as well as endothelial progenitor cell (EPC) migration and tube formation. We also found that resistin upregulates VEGF-A expression by enhancing activation of the transcription factor nuclear factor-kappa B (NF-κB). Finally, resistin promotes angiogenesis in the chick chorioallantoic membrane (CAM) model. Resistin appears to be a promising target for human osteosarcoma.

Piperlongumine, a Novel TrxR1 Inhibitor, Induces Apoptosis in Hepatocellular Carcinoma Cells by ROS-Mediated ER Stress

Hepatocellular carcinoma (HCC) is the sixth most common cancer and the third leading cause of cancer-related deaths globally. Despite advances in diagnosis and treatment, the incidence and mortality of HCC continue to rise. Piperlongumine (PL), an alkaloid isolated from the fruit of the long pepper, is known to selectively kill tumor tissues while sparing their normal counterparts. However, the killing effects of PL on HCC and the underlying mechanism of PL are not clear. We report that PL may interact with thioredoxin reductase 1 (TrxR1), an important selenocysteine (Sec)-containing antioxidant enzyme, and induce reactive oxygen species (ROS)-mediated apoptosis in HCC cells. Our results suggest that PL induces a lethal endoplasmic reticulum (ER) stress response in HCC cells by targeting TrxR1 and increasing intracellular ROS levels. Notably, PL treatment reduces TrxR1 activity and tumor cell burden in vivo. Additionally, TrxR1 is significantly upregulated in existing HCC databases and available HCC clinical specimens. Taken together, these results suggest PL as a novel anticancer candidate for the treatment of HCC. More importantly, this study reveals that TrxR1 might be an effective target in treating HCC.

Anticancer Effects of Constituents of Herbs Targeting Osteosarcoma

Osteosarcoma is a rare primary malignancy of bone that is prone to early metastasis. Resection surgery and chemotherapeutic regimens are current standard treatments for osteosarcoma. However, the long-term survival rate of patients with osteosarcoma is low due to a high risk of metastasis. Hence, a new approach is urgently needed to improve the treatment of osteosarcoma. Compared with chemotherapy, natural active constituents isolated from herbs exhibit less adverse effects and better anti-tumor effects. This study aimed to summarize the anticancer effects of constituents of herbs on the progression and metastasis of osteosarcoma cells. It showed that many constituents of herbs inhibited osteosarcoma by targeting proliferation, matrix metalloproteinases, integrin and cadherin, and angiogenesis. The findings might be beneficial for the development of new drugs and treatment strategies.

Tomentosin Displays Anti-Carcinogenic Effect in Human Osteosarcoma MG-63 Cells via the Induction of Intracellular Reactive Oxygen Species

Tomentosin is a natural sesquiterpene lactone extracted from various plants and is widely used as a medicine because it exhibits essential therapeutic properties. In this study, we investigated the anti-carcinogenic effects of tomentosin in human osteosarcoma MG-63 cells by performing cell migration/viability/proliferation, apoptosis, and reactive oxygen species (ROS) analysis assays. MG-63 cells were treated with various doses of tomentosin. After treatment with tomentosin, MG-63 cells were analyzed using the MTT assay, colony formation assay, cell counting assay, wound healing assay, Boyden chamber assay, zymography assay, cell cycle analysis, FITC Annexin V apoptosis assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, western blot analysis, and ROS detection analysis. Our results indicated that tomentosin decreased cell viability and migration ability in MG-63 cells. Moreover, tomentosin induced apoptosis, cell cycle arrest, DNA damage, and ROS production in MG-63 cells. Furthermore, tomentosin-induced intracellular ROS decreased cell viability and induced apoptosis, cell cycle arrest, and DNA damage in MG-63 cells. Taken together, our results suggested that tomentosin exerted anti-carcinogenic effects in MG-63 cells by induction of intracellular ROS.

Nimbolide, a neem limonoid inhibits cytoprotective autophagy to activate apoptosis via modulation of the PI3K/Akt/GSK-3β signalling pathway in oral cancer

Of late, nimbolide, a limonoid from the neem tree (Azadirachta indica) has gained increasing research attention owing to its potent antiproliferative and apoptosis-inducing effects. The present study was designed to investigate the effect of nimbolide on autophagy and the time point at which the phosphorylation status of GSK-3β and PI3K dictate the choice between autophagy and apoptosis in SCC131 and SCC4 oral cancer cells. Additionally, we analysed changes in the expression of proteins involved in autophagy and apoptosis after therapeutic intervention with nimbolide in a hamster model of oral oncogenesis. Furthermore, we also demonstrate changes in the expression of key genes involved in apoptosis and autophagy during the stepwise evolution of hamster and human OSCCs. Nimbolide-induced stereotypical changes in oral cancer cells characteristic of both apoptosis and autophagy. Time-course experiments revealed that nimbolide induces autophagy as an early event and then switches over to apoptosis. Nimbolide negatively regulates PI3K/Akt signalling with consequent increase in p-GSK-3βTyr216, the active form of GSK-3β that inhibits autophagy. Downregulation of HOTAIR, a competing endogenous RNA that sponges miR-126 may be a major contributor to the inactivation of PI3K/Akt/GSK3 signalling by nimbolide. Analysis of key markers of apoptosis and autophagy as well as p-AktSer473 during sequential progression of hamster and human OSCC revealed a gradual evolution to a pro-autophagic and antiapoptotic phenotype that could confer a survival advantage to tumors. In summary, the results of the present study provide insights into the molecular mechanisms by which nimbolide augments apoptosis by overcoming the shielding effects of cytoprotective autophagy through modulation of the phosphorylation status of Akt and GSK-3β as well as the ncRNAs miR-126 and HOTAIR. Development of phytochemicals such as nimbolide that target the complex interaction between proteins and ncRNAs that regulate the autophagy/apoptosis flux is of paramount importance in cancer prevention and therapeutics.

Nimbolide induced apoptosis by activating ERK-mediated inhibition of c-IAP1 expression in human hepatocellular carcinoma cells

Nimbolide is one of the major compounds from the leaves and flowers of the neem tree and exhibits antitumor properties on various cancer cells. However, no report has shown that nimbolide induces apoptosis in vitro and in vivo in human hepatocellular carcinoma cells. Our results indicated that it inhibited cell growth in Huh-7 and PLC/PRF/5 cells. We also found that nimbolide induced cell death through the induction of G2/M phase arrest and mitochondrial dysfunction, accompanied by the increased expression of cleaved caspase-7, caspase-9, caspase-3, caspase-PARP, and Bax and decreased expression of Mcl-1 and Bcl-2. A human apoptosis antibody array analysis demonstrated that inhibition of the apoptosis family proteins (XIAP, c-IAP1, and c-IAP2) was one of the major targets of nimbolide. Additionally, nimbolide sustained activation of ERK expression. Moreover, pretreatment with U0126 (MEK inhibitor) markedly abolished nimbolide-inhibited cell viability, induced cell apoptosis, ERK phosphorylation, cleaved caspase-9, caspase-3, cleaved-PARP activation, and increased c-IAP1 expression in Huh-7 cells. An in vivo study showed that nimbolide significantly reduced Huh-7 tumor growth and weight in a xenograft mouse model. This study indicated the antitumor potential of nimbolide in human hepatocellular carcinoma cells.

Evaluation of Apoptosis and Autophagy Inducing Potential of Berberis aristata, Azadirachta indica, and Their Synergistic Combinations in Parental and Resistant Human Osteosarcoma Cells

Cancer is a multifactorial disease and hence can be effectively overcome by a multi-constituently therapeutic strategy. Medicinal plant extracts represent a perfect example of such stratagem. However, minimal studies have been done till date that portray the effect of extraction techniques on the phyto-constituent profile of plant extracts and its impact on anticancer activity. In the present study, we have evaluated the anticancer potential of methanolic extracts of Berberis aristata root and Azadirachta indica seeds prepared by various extraction techniques in human osteosarcoma (HOS) cells. Soxhlation extract of B. aristata (BAM-SX) and sonication extract of A. indica (AIM-SO) were most effective in inducing apoptosis in parental drug sensitive, as well as resistant cell type developed by repeated drug exposure. Generation of reactive oxygen species and cell cycle arrest preceded caspase-mediated apoptosis in HOS cells. Interestingly, inhibition of autophagy enhanced cell death suggesting the cytoprotective role of autophagy. Combination studies of different methanolic extracts of BAM and AIM were performed, among which, the combination of BAM-SO and AIM-SO (BAAISO) was found to show synergism (IC₅₀ 10.27 µg/ml) followed by combination of BAM-MC and AIM-MC (BAAIMC) with respect to other combinations in the ratio of 1:1. BAAISO also showed synergism when it was added to cisplatin-resistant HOS cells (HCR). Chromatographic profiling of BAM-SX and AIM-SO by high performance thin layer chromatography resulted in identification of berberine (R_f 0.55), palmitine (R_f 0.50) in BAM-SX and azadirachtin A (R_f 0.36), azadirachtin B (R_f 0.56), nimbin (R_f 0.80), and nimbolide (R_f 0.43) in AIM-SO. The cytotoxic sensitivity obtained can be attributed to the above compounds. Our results highlight the importance of extraction technique and subsequent mechanism of action of multi-constituential B. aristata and A. indica against both sensitive and drug refractory HOS cells.

Nimbolide induces apoptosis in human nasopharyngeal cancer cells

Nasopharyngeal carcinoma (NPC), a tumor arising from epithelial cells that cover the surface and line the nasopharynx, is a rare malignancy worldwide but is prevalent in certain geographical areas, such as Southern Asia (Taiwan, Hong Kong, Singapore, Malaysia, and Southern China) and North Africa. Despite advances in diagnostic techniques and improvements in treatment modalities, the prognosis of NPC remains poor. Therefore, an effective chemotherapy regimen that enhances tumor sensitivity to chemotherapeutics is urgently required. Nimbolide, derived from Azadirachta indica, has a wide range of beneficial effects, including anti-inflammatory and anticancer properties. The present study evaluated the antitumor activity of nimbolide in NPC cells and its underlying mechanisms. Our results revealed that the treatment of HONE-1 cells with nimbolide potently inhibited cell viability. Moreover, nimbolide led to cell cycle arrest, which subsequently activated caspase-3, -8, and -9 and poly (ADP-ribose) polymerase to induce cell apoptosis. Moreover, nimbolide induced Bik, Bax, and t-Bid expression in HONE-1 cells. The results indicated that nimbolide induces apoptosis through the modulation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathways. Nimbolide induces apoptosis in human NPC cells and is a potential chemopreventive agent against NPC proliferation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 2085-2092, 2017.

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

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

Valproate Attenuates Endoplasmic Reticulum Stress-Induced Apoptosis in SH-SY5Y Cells via the AKT/GSK3β Signaling Pathway

Endoplasmic reticulum (ER) stress-induced apoptosis plays an important role in a range of neurological disorders, such as neurodegenerative diseases, spinal cord injury, and diabetic neuropathy. Valproate (VPA), a typical antiepileptic drug, is commonly used in the treatment of bipolar disorder and epilepsy. Recently, VPA has been reported to exert neurotrophic effects and promote neurite outgrowth, but its molecular mechanism is still unclear. In the present study, we investigated whether VPA inhibited ER stress and promoted neuroprotection and neuronal restoration in SH-SY5Y cells and in primary rat cortical neurons, respectively, upon exposure to thapsigargin (TG). In SH-SY5Y cells, cell viability was detected by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and the expression of ER stress-related apoptotic proteins such as glucose‑regulated protein (GRP78), C/EBP homologous protein (CHOP), and cleaved caspase-12/-3 were analyzed with Western blot analyses and immunofluorescence assays. To explore the pathway involved in VPA-induced cell proliferation, we also examined p-AKT, GSK3β, p-JNK and MMP-9. Moreover, to detect the effect of VPA in primary cortical neurons, immunofluorescence staining of β-III tubulin and Anti-NeuN was analyzed in primary cultured neurons exposed to TG. Our results demonstrated that VPA administration improved cell viability in cells exposed to TG. In addition, VPA increased the levels of GRP78 and p-AKT and decreased the levels of ATF6, XBP-1, GSK3β, p-JNK and MMP-9. Furthermore, the levels of the ER stress-induced apoptosis response proteins CHOP, cleaved caspase-12 and cleaved caspase-3 were inhibited by VPA treatment. Meanwhile, VPA administration also increased the ratio of Bcl-2/Bax. Moreover, VPA can maintain neurite outgrowth of primary cortical neurons. Collectively, the neurotrophic effect of VPA is related to the inhibition of ER stress-induced apoptosis in SH-SY5Y cells and the maintenance of neuronal growth. Collectively, our results suggested a new approach for the therapeutic function of VPA in neurological disorders and neuroprotection.

Inhibition of cell survival and proliferation by nimbolide in human androgen-independent prostate cancer (PC-3) cells: involvement of the PI3K/Akt pathway

Prostate cancer is most common malignancy among men in the world. PI3K-Akt signaling appears to be critical to prostate cancer cell proliferation and survival. Our earlier study reveals that nimbolide (2 µM) prevents cell survival via IGF signaling pathway through PI3K/Akt and induces apoptosis in PC-3 cell line. Akt mediates the phosphorylation and activation of mTOR that plays a critical role in the regulation of protein translation and synthesis, angiogenesis, and cell cycle progression. The present study was aimed to investigate the effect of nimbolide on tPI3K, tAkt, pAkt, tmTOR, GSK3β, pGSK3β, PCNA, c-Myc, Cyclin D1, and Survivin protein levels by western blot analysis. Apoptosis was visualized by Ao/EtBr dual staining (20×), and protein expression of PCNA by immunocytochemistry was performed. Molecular docking was performed to understand the possible interaction between nimbolide and Akt, PCNA, and Cyclin D1. Nimbolide altered the PI3K-Akt-mediated cell survival and proliferative molecules. Thus, nimbolide exerted anticancer effects in vitro by representing the PI3K-Akt-mTOR pathway in PC-3 cells. Thereby, it acts as a potent anticancer drug for prostate cancer.

BL-038, a Benzofuran Derivative, Induces Cell Apoptosis in Human Chondrosarcoma Cells through Reactive Oxygen Species/Mitochondrial Dysfunction and the Caspases Dependent Pathway

Chondrosarcoma is a highly malignant cartilage-forming bone tumor that has the capacity to invade locally and cause distant metastasis. Moreover, chondrosarcoma is intrinsically resistant to conventional chemotherapy or radiotherapy. The novel benzofuran derivative, BL-038 (2-amino-3-(2,6-dichlorophenyl)-6-(4-methoxyphenyl)benzofuran-4-yl acetate), has been evaluated for its anticancer effects in human chondrosarcoma cells. BL-038 caused cell apoptosis in two human chondrosarcoma cell lines, JJ012 and SW1353, but not in primary chondrocytes. Treatment of chondrosarcoma with BL-038 also induced reactive oxygen species (ROS) production. Furthermore, BL-038 decreased mitochondrial membrane potential (MMP) and changed mitochondrial-related apoptosis, by downregulating the anti-apoptotic activity members (Bcl-2, Bcl-xL) and upregulating pro-apoptotic members (Bax, Bak) of the B-cell lymphoma 2 (Bcl-2) family of proteins, key regulators of the apoptotic machinery in cells. These results demonstrate that in human chondrosarcoma cells, the apoptotic and cytotoxic effects of BL-038 are mediated by the intrinsic mitochondria-mediated apoptotic pathway, which in turn causes the release of cytochrome c, the activation of caspase-9 and caspase-3, and the cleavage of poly (ADP-ribose) polymerase (PARP), to elicit apoptosis response. Our results show that the benzofuran derivative BL-038 induces apoptosis in chondrosarcoma cells.

Anticancer properties of nimbolide and pharmacokinetic considerations to accelerate its development

Nimbolide is one of the main components in the leaf extract of Azadirachta indica (A. indica). Accumulating evidence from various in vitro and in vivo studies indicates that nimbolide possesses potent anticancer activity against several types of cancer and also shows potential chemopreventive activity in animal models. The main mechanisms of action of nimbolide include anti-proliferation, induction of apoptosis, inhibition of metastasis and angiogenesis, and modulation of carcinogen-metabolizing enzymes. Although multiple pharmacodynamic (PD) studies have been carried out, nimbolide is still at the infant stage in the drug development pipeline due to the lack of systematic pharmacokinetic (PK) studies and long-term toxicological studies. Preclinical PK and toxicological studies are vital in determining the dosage range to support the safety of nimbolide for first-in-human clinical trials. In this review, we will provide a comprehensive summary for the current status of nimbolide as an anticancer and chemopreventive lead compound, and highlight the importance of systematic preclinical PK and toxicological studies in accelerating the process of application of nimbolide as a therapeutic agent against various malignancies.