Celastrol induces apoptosis of human osteosarcoma cells via the mitochondrial apoptotic pathway

Gedunin modulates cellular growth and apoptosis in glioblastoma cell lines

BACKGROUND

Glioblastomas are characterized by aggressive behavior. Surgery, radiotherapy, and alkylating agents, including temozolomide are the most common treatment options for glioblastoma. Often, conventional therapies fail to treat these tumors since they develop drug resistance. There is a need for newer agents to combat this deadly tumor. Natural products such as gedunin have shown efficacy in several human diseases. A comprehensive study of gedunin, an heat shock protein (HSP)90 inhibitor, has not been thoroughly investigated in glioblastoma cell lines with different genetic modifications.

AIMS

A key objective of this study was to determine how gedunin affects the biological and signaling mechanisms in glioblastoma cells, and to determine how those mechanisms affect the proliferation and apoptosis of glioblastoma cells.

METHODS

The viability potentials of gedunin were tested using MTT, cell counts, and wound healing assays. Gedunin's effects on glioma cells were further validated using LDH and colony formation assays. In addition, we investigated the survival and apoptotic molecular signaling targets perturbed by gedunin using Western blot analysis and flow cytometry.

RESULTS

Our results show that there was a reduction in cell viability and inhibition of wound healing in the cells tested. Western blot analysis of the gene expression data revealed genes such as EGFR and mTOR/Akt/NF kappa B to be associated with gedunin sensitivity. Gedunin treatment induced apoptosis by cleaving poly ADP-ribose polymerase, activating caspases, and downregulating BCL-xL. Based on these results, gedunin suppressed cell growth and HSP client proteins, resulting in apoptosis in glioblastoma cell lines.

CONCLUSION

Our data provide in vitro support for the anticancer activity of gedunin in glioma cells by downregulating cancer survival proteins.

Withaferin A and Celastrol Overwhelm Proteostasis

Withaferin A (WA) and celastrol (CEL) are major bioactive components of plants that have been widely employed in traditional medicine. The pleiotropic activities of plant preparations and the isolated compounds in vitro and in vivo have been documented in hundreds of studies. Both WA and CEL were shown to have anticancer activity. Although WA and CEL belong to different chemical classes, our synthesis of the available information suggests that the compounds share basic mechanisms of action. Both WA and CEL bind covalently to numerous proteins, causing the partial unfolding of some of these proteins and of many bystander proteins. The resulting proteotoxic stress, when excessive, leads to cell death. Both WA and CEL trigger the activation of the unfolded protein response (UPR) which, if the proteotoxic stress persists, results in apoptosis mediated by the PERK/eIF-2/ATF4/CHOP pathway or another UPR-dependent pathway. Other mechanisms of cell death may play contributory or even dominant roles depending on cell type. As shown in a proteomic study with WA, the compounds appear to function largely as electrophilic reactants, indiscriminately modifying reachable nucleophilic amino acid side chains of proteins. However, a remarkable degree of target specificity is imparted by the cellular context.

Mechanistic engineering of celastrol liposomes induces ferroptosis and apoptosis by directly targeting VDAC2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of most common and deadliest malignancies. Celastrol (Cel), a natural product derived from the Tripterygium wilfordii plant, has been extensively researched for its potential effectiveness in fighting cancer. However, its clinical application has been hindered by the unclear mechanism of action. Here, we used chemical proteomics to identify the direct targets of Cel and enhanced its targetability and anti-tumor capacity by developing a Cel-based liposomes in HCC. We demonstrated that Cel selectively targets the voltage-dependent anion channel 2 (VDAC2). Cel directly binds to the cysteine residues of VDAC2, and induces cytochrome C release via dysregulating VDAC2-mediated mitochondrial permeability transition pore (mPTP) function. We further found that Cel induces ROS-mediated ferroptosis and apoptosis in HCC cells. Moreover, coencapsulation of Cel into alkyl glucoside-modified liposomes (AGCL) improved its antitumor efficacy and minimized its side effects. AGCL has been shown to effectively suppress the proliferation of tumor cells. In a xenograft nude mice experiment, AGCL significantly inhibited tumor growth and promoted apoptosis. Our findings reveal that Cel directly targets VDAC2 to induce mitochondria-dependent cell death, while the Cel liposomes enhance its targetability and reduces side effects. Overall, Cel shows promise as a therapeutic agent for HCC.

Protein Phosphatase 2A as a Therapeutic Target in Pulmonary Diseases

New disease targets and medicinal chemistry approaches are urgently needed to develop novel therapeutic strategies for treating pulmonary diseases. Emerging evidence suggests that reduced activity of protein phosphatase 2A (PP2A), a complex heterotrimeric enzyme that regulates dephosphorylation of serine and threonine residues from many proteins, is observed in multiple pulmonary diseases, including lung cancer, smoke-induced chronic obstructive pulmonary disease, alpha-1 antitrypsin deficiency, asthma, and idiopathic pulmonary fibrosis. Loss of PP2A responses is linked to many mechanisms associated with disease progressions, such as senescence, proliferation, inflammation, corticosteroid resistance, enhanced protease responses, and mRNA stability. Therefore, chemical restoration of PP2A may represent a novel treatment for these diseases. This review outlines the potential impact of reduced PP2A activity in pulmonary diseases, endogenous and exogenous inhibitors of PP2A, details the possible PP2A-dependent mechanisms observed in these conditions, and outlines potential therapeutic strategies for treatment. Substantial medicinal chemistry efforts are underway to develop therapeutics targeting PP2A activity. The development of specific activators of PP2A that selectively target PP2A holoenzymes could improve our understanding of the function of PP2A in pulmonary diseases. This may lead to the development of therapeutics for restoring normal PP2A responses within the lung.

Dihydromyricetin functions as a tumor suppressor in hepatoblastoma by regulating SOD1/ROS pathway

Background

Hepatoblastoma has an unsatisfactory prognosis, and traditional chemotherapy has strong side effects. Dihydromyricetin is a flavonoid extracted from a woody vine of the genus Serpentine in the family Vitaceae, with effects such as preventing alcoholic liver and reducing the incidence of liver cancer. However, the effect of DHM on hepatoblastoma and its specific pathway are still unclear.

Purpose

The purpose of this study was to investigate the effects of DHM on children's hepatoblastoma and its related mechanisms.

Methods

CCK-8 assays were used to measure proliferation. Apoptosis and reactive oxygen species (ROS) were analyzed by flow cytometry. Apoptotic cells were observed using Hoechst 33342 staining and fluorescence microscopy. Protein expression levels in HuH-6 and HepG2 cells were determined by western blotting.

Results

We found that DHM was able to inhibit the growth and increase cellular mortality in HuH-6 and HepG2 cells. Furthermore, DHM decreased the intracellular ROS level and increased the expression of SOD1. ROS scavenger NAC promoted apoptosis, while the use of SOD1 inhibitor LCS-1 weakened the ROS scavenging effect of DHM , and to some extent reduced the killing effect of DHM on hepatoblastoma cells.

Conclusion

These results suggest that regulating SOD1/ROS pathway to induce apoptosis is one of the potential mechanisms of DHM as a tumor suppressor in hepatoblastoma. Therefore, DHM may be a novel candidate for inhibiting hepatoblastoma growth and deserves further study.

Nanotherapeutic macrophage-based immunotherapy for the peritoneal carcinomatosis of lung cancer

Lung cancer is the top cause of cancer mortality in the world. Distant metastasis leads to high mortality. Abdominal metastasis of lung cancer is characterized by very poor prognosis and the median survival time is usually less than two months. Therefore, it is of clinical significance to develop a new effective method for the treatment of abdominal metastasis of lung cancer. Cell therapy has promoted the development of new technology and strategy in oncology. Macrophages, as an important component of solid tumors, have also attracted great attention as a promising strategy of cell therapy in oncology. However, the reinfusion of autologous macrophages would be easily "re-educated" by the tumor microenvironment into a phenotype that promotes tumor development. This work developed a potential therapy using celastrol nanoparticle-containing M1-like macrophages (NP@M1) as a combinatory therapeutic system. M1-like macrophages (M1Φ) not only can serve as a drug delivery carrier for celastrol but also as a biotherapeutic agent. In turn, the celastrol nanoparticles (NPs) can maintain an anticancer polarized status of M1Φ, and subsequently, the exocytosed NPs can also execute the tumor cell-killing effect. Such a system thus provides a "two-birds-one-stone" therapeutic strategy and a proof of concept for the currently incurable abdominal metastasis of lung cancer.

Naringenin Induces ROS-Mediated ER Stress, Autophagy, and Apoptosis in Human Osteosarcoma Cell Lines

Osteosarcoma, a primary bone tumor, responds poorly to chemotherapy and radiation therapy in children and young adults; hence, as the basis for an alternative treatment, this study investigated the cytotoxic and antiproliferative effects of naringenin on osteosarcoma cell lines, HOS and U2OS, by using cell counting kit-8 and colony formation assays. DNA fragmentation and the increase in the G2/M phase in HOS and U2OS cells upon treatment with various naringenin concentrations were determined by using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and Annexin V/propidium iodide double staining, respectively. Flow cytometry was performed, and 2′,7′-dichlorodihydrofluorescein diacetate, JC-1, and Fluo-4 AM ester probes were examined for reactive oxygen species (ROS) generation, mitochondrial membrane potential, and intracellular calcium levels, respectively. Caspase activation, cell cycle, cytosolic and mitochondrial, and autophagy-related proteins were determined using western blotting. The results indicated that naringenin significantly inhibited viability and proliferation of osteosarcoma cells in a dose-dependent manner. In addition, naringenin induced cell cycle arrest in osteosarcoma cells by inhibiting cyclin B1 and cyclin-dependent kinase 1 expression and upregulating p21 expression. Furthermore, naringenin significantly inhibited the growth of osteosarcoma cells by increasing the intracellular ROS level. Naringenin induced endoplasmic reticulum (ER) stress-mediated apoptosis through the upregulation of ER stress markers, GRP78 and GRP94. Naringenin caused acidic vesicular organelle formation and increased autophagolysosomes, microtubule-associated protein-light chain 3-II protein levels, and autophagy. The findings suggest that the induction of cell apoptosis, cell cycle arrest, and autophagy by naringenin through mitochondrial dysfunction, ROS production, and ER stress signaling pathways contribute to the antiproliferative effect of naringenin on osteosarcoma cells.

Furin-responsive triterpenine-based liposomal complex enhances anticervical cancer therapy through size modulation

The accumulation and penetration of antitumor drugs in tumor tissues are directly related to their antitumor effects. The particle size of the nanodrug delivery system is one of the most important factors for the accumulation and penetration of antitumor drugs within tumor tissues. Generally, nanodelivery systems of intermediate size (100–120 nm) are capable of efficient accumulation owing to prolonged circulation and enhanced permeability and retention (EPR) effect; however, smaller ones (20–40 nm) are effective for deep penetration within tumor tissue. Currently a conventional drug delivery system cannot possess two types of optimal sizes, simultaneously. To solve this and to enhance cervical cancer treatment, a furin-responsive triterpenine-based liposomal complex (PEGcleavable Tf-CTM/L), with Tf-CTM (transferrin-modified tripterine-loaded coix seed oil microemulsion) in core, coated with a thermo-sensitive lipid and a kind of PEG shell modified with a furin-cleavable peptide was developed to improve tumor-specific accumulation and penetration. Herein, PEGcleavable Tf-CTM/L was capable of efficient accumulation because of EPR effect. The PEG shells could timely detach under stimulation of overexpressed furin protein to solve the problem of the steric hindrance dilemma. The small-sized Tf-CTM released under stimulation of tumor microthermal environment in cervical cancer, which was efficient with regards to deep penetration at tumor sites. Notably, compared to the use of triterpenine alone, PEGcleavable Tf-CTM/L promoted anticervical efficacy and displayed diminished systemic toxicity by efficient accumulation and deep penetration of antitumor drugs within tumor tissues. Our study provides a new strategy, and holds promising potential for anticervical cancer treatment.

Diallyl trisulfide regulates cell apoptosis and invasion in human osteosarcoma U2OS cells through regulating PI3K/AKT/GSK3β signaling pathway

AIMS

To investigate the effects and the mechanisms of action of Diallyl trisulfide (DATS) on the proliferation and metastasis of human osteosarcoma (OS) U2OS.

METHODS

U2OS cells were treated by different concentrations of DATS at different time points. Cell proliferations were measured by MTT assay. DATS induced cell cycle distribution and apoptosis were evaluated by flow cytometry (FCM) with Annexin-V. Cell migration and invasion were detected by wound healing assay and transwell assay. The effects of DATS in U2OS cell growth and metastasis were also detected in a mouse OS xenograft model.

RESULTS

A time- and concentration-dependent cytotoxic effect of DATS was observed in U2OS cells. FCM with PI staining and Annexin-V -FITC indicated that DATS induces apoptosis and a G0/G1 cell cycle arrest of U2OS cells at all concentrations from 25 μmol/l to 100 μmol/l. DATS also inhibits the migration and invasion of U2OS cells. Western blot showed that the expression levels of p-AKT, p-GSK3β, Bcl-2, Vimentin and β-catenin were decreased, while the expression levels of Bad, Bax and E-cadherin were significantly increased in DATS treated U2OS cells. Analysis using a mouse xenograft model indicated that xenografts of DATS treatment group had a significant decrease in tumor volume and weight compared to the control group. Lung metastasis models in mice demonstrated that treatment of DATS inhibits lung metastasis of OS in vivo.

CONCLUSIONS

These data suggested that DATS inhibits OS development and progression through the regulation of PI3K/AKT/GSK3β signaling pathways, accompanied by downregulation of Bcl-2, Vimentin and β-catenin, as well as upregulation of Bad, Bax and E-cadherin. Therefore, our data demonstrated that DATS exerted its anticancer effects by inhibiting cell proliferation, migration and invasion in vitro and in vivo. These results provide evidence for the use of the natural product DATS either alone or in combination with standard therapy for OS.

Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and Alzheimer's Disease

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase which participates in the regulation of multiple cellular processes. As a confirmed tumor suppressor, PP2A activity is downregulated in tumors and its re-activation can induce apoptosis of cancer cells. In the brains of Alzheimer's disease (AD) patients, decreased PP2A activity also plays a key role in promoting tau hyperphosphorylation and Aβ generation. In this review, we discussed compounds aiming at modulating PP2A activity in the treatment of cancer or AD. The upstream factors that inactivate PP2A in diseases have not been fully elucidated and further studies are needed. It will help for the refinement and development of novel and clinically tractable PP2A-targeted compounds or therapies for the treatment of tumor and AD.

Metabolomics Reveals that Cysteine Metabolism Plays a Role in Celastrol-Induced Mitochondrial Apoptosis in HL-60 and NB-4 Cells

Recently, celastrol has shown great potential for inducing apoptosis in acute myeloid leukemia cells, especially acute promyelocytic leukaemia cells. However, the mechanism is poorly understood. Metabolomics provides an overall understanding of metabolic mechanisms to illustrate celastrol's mechanism of action. We treated both nude mice bearing HL-60 cell xenografts in vivo and HL-60 cells as well as NB-4 cells in vitro with celastrol. Ultra-performance liquid chromatography coupled with mass spectrometry was used for metabolomics analysis of HL-60 cells in vivo and for targeted L-cysteine analysis in HL-60 and NB-4 cells in vitro. Flow cytometric analysis was performed to assess mitochondrial membrane potential, reactive oxygen species and apoptosis. Western blotting was conducted to detect the p53, Bax, cleaved caspase 9 and cleaved caspase 3 proteins. Celastrol inhibited tumour growth, induced apoptosis, and upregulated pro-apoptotic proteins in the xenograft tumour mouse model. Metabolomics showed that cysteine metabolism was the key metabolic alteration after celastrol treatment in HL-60 cells in vivo. Celastrol decreased L-cysteine in HL-60 cells. Acetylcysteine supplementation reversed reactive oxygen species accumulation and apoptosis induced by celastrol and reversed the dramatic decrease in the mitochondrial membrane potential and upregulation of pro-apoptotic proteins in HL-60 cells. In NB-4 cells, celastrol decreased L-cysteine, and acetylcysteine reversed celastrol-induced reactive oxygen species accumulation and apoptosis. We are the first to identify the involvement of a cysteine metabolism/reactive oxygen species/p53/Bax/caspase 9/caspase 3 pathway in celastrol-triggered mitochondrial apoptosis in HL-60 and NB-4 cells, providing a novel underlying mechanism through which celastrol could be used to treat acute myeloid leukaemia, especially acute promyelocytic leukaemia.

Celastrus orbiculatus Extracts Inhibit Human Hepatocellular Carcinoma Growth by Targeting mTOR Signaling Pathways

OBJECTIVE

To characterize the molecular mechanism underlying the antineoplastic activity of Celastrus orbiculatus Thunb. extracts (COE).

METHODS

The human hepatocellular carcinoma HepG2 cells with mammalian target of rapamycin (mTOR) knockdown expressed (HepG2/mTOR) were constructed using molecular biological technology. In vitro, the HepG2/mTOR^- cells were treated with COE at various concentrations (10, 20, 40, 80, 160 and 320 µ g/mL). Cell viability was determined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays. According to the half-maximal inhibitory concentration (IC₅₀) value (140 mg/L), the concentrations of COE in the subsequent experiment was set to alleviate cytotoxicity. The HepG2/mTOR^- cells were divided into 5 groups: negative control (untreated), COE treatment groups (40, 80, 120 mg/L COE) and positive control group (cisplatin, DDP, 2 mg/L), respectively. Wild-type HepG2 cells were used as a blank control. The effects of COE on the cell apoptosis were analyzed by flow cytometry and transmission electronic microscopy (TEM), respectively. The protein expression levels of mTOR signal pathways were determined by Western blotting. In vivo, HepG2/mTOR^- cells (2 × 10⁶ cell/mice) were subcutaneously injected into the right flank of nude mice. Thirty-six female nude mice were randomly assigned to 6 groups according to body weight (6 mice per group) as follows: solvent vehicle control, Banmao Capsule treated group (BM, 195 mg/kg), Tegafur, Gimeracil and Oteracil Potassium Capsules (10 mg/kg) treated group, and different dosages of COE (10, 20, 40 mg/kg) groups. Tumor growth was monitored and immunohistochemical staining was used to examine the expression of apoptosis-related proteins in tumor tissues.

RESULTS

COE inhibited the proliferation significantly in a concentration-dependent manner in HepG2/mTOR^- cells (P<0.01). COE significantly induced the apoptosis of HepG2/mTOR^- cells (P<0.01), and the apoptotic bodies can be observed under TEM. COE significantly inhibits the proteins expression of mTOR-related signal pathways. In vivo, COE significantly inhibited tumor growth in nude mice (P<0.01). Moreover, the results showed that COE down-regulated the expression of Bcl-2 and Bcl-xL, and up-regulated the levels of Bax and caspase-3 protein (P<0.01).

CONCLUSION

COE was a potential chemotherapeutic drug in HCC treatments via targeting mTOR signal pathway.

Celastrol induces vincristine multidrug resistance oral cancer cell apoptosis by targeting JNK1/2 signaling pathway

BACKGROUND

Oral cancers are one of the most aggressive malignancies, with high mortality rates globally. Patients with these cancers are treated using combination therapies including surgery, chemotherapy, and radiotherapy.

HYPOTHESIS/PURPOSE

Traditional Chinese medicines and other herbal medicines have been used to treat various diseases in Asia. Celastrol is a pentacyclic triterpenoid isolated from the Chinese herbal medicine Trypterygium wilfordii, which has therapeutic potential in multiple diseases. The present study was to determine the effect of celastrol on vincristine-resistant cancer cell line and to illuminate the mechanism of celastrol-induced cell apoptosis.

STUDY DESIGN

Celastrol was added to vincristine-resistant cancer cell and immunoreactive proteins were detected.

METHODS AND RESULTS

Our study demonstrated that celastrol leads to apoptosis of head and neck cancer cells through mitochondria- and Fas-mediated pathways. However, whether this herbal medicine exhibits beneficial effects on vincristine-resistant oral cancer patients remains uncertain. Therefore, our study examined the apoptotic effect exerted by celastrol and the mechanism by this drug acts on a vincristine-resistant cancer cell line. The present study demonstrated that celastrol triggered apoptotic cell death by inducing cell cycle arrest at the G2/M phase via the intrinsic and extrinsic pathways (increased cleaved caspase-3, caspase-8, caspase-9, and PARP). Increased expression of tBid also indicated the presence of crosstalk between the two pathways. Celastrol mediated cell apoptosis through the downregulation of the expression of Bcl-2, not Bcl-xL. Moreover, JNK1/2 signaling was the main pathway of celastrol-induced apoptosis.

CONCLUSION

Celastrol could become a useful agent for treating oral cancers with MDR.

Efficacy of celastrol combined with cisplatin in enhancing the apoptosis of U-2OS osteosarcoma cells via the mitochondrial and endoplasmic reticulum pathways of apoptosis

Osteosarcoma is a common primary malignant tumor of bone, and the poor prognosis and low 5-year survival rate have not improved for three decades. The present study aimed to study the effect a combination of celastrol and cisplatin on the human osteosarcoma cell line U-2OS, and to investigate the mechanism by which celastrol/cisplatin induces the apoptosis of osteosarcoma cells. MTT and Annexin V-FITC/PI assays were used to evaluate the effects of combined celastrol/cisplatin on growth and apoptosis, respectively, in U-2OS cells. Morphological changes accompanying cell growth inhibition were observed using a fluorescence microscope. Combination index (CI) analysis was used to evaluate the combinatorial effects of celastrol/cisplatin treatment. Western blotting was used to quantify the expression of apoptosis-associated proteins. It was identified that celastrol/cisplatin inhibited the growth of U-2OS cells in a dose-dependent manner. CI analysis revealed that combined celastrol/cisplatin demonstrated a synergistic effect in U-2OS cells, with CIs ranging from 0.80 to 0.97 at effect levels from IC₁₀ to IC₇₀. In addition, it was observed that celastrol/cisplatin upregulated the expression of Bcl-associated X protein, cytochrome c, caspase-3 and C/EBP homologous protein, and downregulated the expression of Bcl-2, poly(ADP-ribose) polymerase, 78 kDa glucose-regulated protein and caspase-9, whereas the expression of caspase-8 remained unchanged. To conclude, celastrol/cisplatin induced apoptosis in U-2OS cells via the mitochondrial and endoplasmic reticulum pathways, particularly in the former. Celastrol/cisplatin therefore exhibits potential as a novel therapeutic combination for the treatment of osteosarcoma.

Nickel-smelting fumes induce mitochondrial damage and apoptosis, accompanied by decreases in viability, in NIH/3T3 cells

Nickel (Ni) is widely present in the occupational environment and causes various adverse effects on the human body. Apoptosis induced by Ni²⁺ may be a key mechanism underlying its toxic effect. In the present study, we investigated the effect of Ni-smelting fumes on cell viability, mitochondrial damage, and apoptosis-related proteins in NIH/3T3 cells. The effects of Ni-smelting fumes at concentrations of 0, 25, 50, and 100 μg/mL were tested. Treatment with Ni-smelting fumes for 24 h and 48 h significantly decreased cell viability and lactate dehydrogenase activity in a dose- and time-dependent manner compared with the blank control group. Exposure to Ni-smelting fumes increased mitochondrial permeability transition pore opening in a dose-dependent manner and decreased mitochondrial membrane potential and the activity of the mitochondrial respiratory chain complexes I, II, and IV. The fumes significantly downregulated Bcl-2, procaspase-9, and procaspase-3 and upregulated Bax, caspase-9, and caspase-3 (P < 0.05). Ni-smelting fumes caused significant cytotoxicity, oxidative stress, mitochondrial damage, and apoptosis through the intrinsic pathway in mammalian cells. The present paper provides hypotheses and experimental support for these hypotheses that Ni-smelting fumes cause cytotoxicity through the mechanism of inducing mitochondrial damage and apoptosis in NIH/3T3 cells.

Celastrol increases osteosarcoma cell lysis by γδ T cells through up-regulation of death receptors

γδ T cells has been shown to exhibit profound antitumor effects in a broad range of tumor entities, including OS. However, resistance to γδ T cells is a serious problem in the management of OS. This study investigates the impact of celastrol on the expression of death receptors 4/5 (DR4/5) on OS cell lines (HOS, U2OS) and cancer cell lysis by γδ T cells. The results showed that celastrol increased transcription of DR4/5 in HOS and U2OS, leading to increased cell surface, and total DR4/5 protein expression. Celastrol sensitizes OS cell lines or autologous OS cells to healthy donors-derived or OS patient-derived γδ T cell cytotoxicity in vitro. The induction of DR4/5 molecules increased lysis of HOS and U2OS by γδ T cells which was abolished by addition of a blocking TRAIL antibody. Importantly, the cytotoxic activity of γδ T cells was unaltered by small-dose celastrol. Taken together, our data show that celastrol up-regulated DR4/5 on OS cells to be responsible for intercellular TRAIL/APO-2L crosslink that confers increased cancer cell lysis by γδ T cells. These results suggest the clinical evaluation of celastrol in OS, especially in combination with immunotherapy approaches employing adoptive γδ T cell transfer.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

Gold nanourchins and celastrol reorganize the nucleo- and cytoskeleton of glioblastoma cells

The physicochemical properties and cytotoxicity of diverse gold nanoparticle (AuNP) morphologies with smooth surfaces have been examined extensively. Much less is known about AuNPs with irregular surfaces. This study focuses on the effects of gold nanourchins in glioblastoma cells. With limited success of monotherapies for glioblastoma, multimodal treatment has become the preferred regimen. One possible example for such future therapeutic applications is the combination of AuNPs with the natural cytotoxic agent celastrol. Here, we used complementary physical, chemical and biological methods to characterize AuNPs and investigate their impact on glioblastoma cells. Our results show that gold nanourchins altered glioblastoma cell morphology and reorganized the nucleo- and cytoskeleton. These changes were dependent on gold nanourchin surface modification. PEGylated nanourchins had no significant effect on glioblastoma cell morphology or viability, unless they were combined with celastrol. By contrast, CTAB-nanourchins adversely affected the nuclear lamina, microtubules and filamentous actin. These alterations correlated with significant glioblastoma cell death. We identified several mechanisms that contributed to the impact of AuNPs on the cytoskeleton and cell survival. Specifically, CTAB-nanourchins caused a significant increase in the abundance of Rock1. This protein kinase is a key regulator of the cytoskeleton. In addition, CTAB-nanourchins led to a marked decline in pro-survival signaling via the PI3 kinase-Akt pathway. Taken together, our study provides new insights into the molecular pathways and structural components altered by gold nanourchins and their implications for multimodal glioblastoma therapy.

Synthesis and characterisation of celastrol derivatives as potential anticancer agents

In the present study, three series of novel celastrol derivatives were designed and synthesised by modifying the carboxylic acid at the 20th position with amino acid, amine, and triazole derivatives. All the synthesised compounds were screened for their anticancer activities using MTT assay against AGS, MGC-803, SGC-7901, HCT-116, A549, HeLa, BEL-7402, and HepG-2 cell lines. Most of the synthesised compounds exhibited potent antiproliferative effects. The most promising compound 3-Hydroxy-9β,13α-dimethyl-2-oxo-24,25,26-trinoroleana-1(10),3,5,7-tetraen-29-oic amide, N-(R)-methyl-3-(1H-indol-2-yl)propanoate (11) showed considerable high anticancer activity against AGS cell lines, with an IC₅₀ value of 0.44 μM, and considerably higher activities against HCT-116, BEL-7402, and HepG-2 cell lines, with IC₅₀ values of 0.78, 0.63, and 0.76 μM, respectively. The results of apoptosis tests and molecular docking study of compound 11 binding to Caspase-3 revealed that its mechanism of action with antiproliferative was possibly involved in inducing apoptosis by inducing the activation of caspase-3.

Therapeutic targeting of PP2A

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that regulates many cellular processes. Given the central role of PP2A in regulating diverse biological functions and its dysregulation in many diseases, including cancer, PP2A directed therapeutics have become of great interest. The main approaches leveraged thus far can be categorized as follows: 1) inhibiting endogenous inhibitors of PP2A, 2) targeted disruption of post translational modifications on PP2A subunits, or 3) direct targeting of PP2A. Additional insight into the structural, molecular, and biological framework driving the efficacy of these therapeutic strategies will provide a foundation for the refinement and development of novel and clinically tractable PP2A targeted therapies.

Effects of baicalein on proliferation, apoptosis, migration and invasion of Ewing's sarcoma cells

Ewing's sarcoma (ES) is a rare tumor that is more frequent in pediatric and adolescent age groups. In the past few decades, long-term survival in affected patients has improved due to the success of multimodal therapy. However, long-term survival is inevitably restricted by the late side-effects of chemotherapy. Besides, early metastasis also contributes to the poor prognosis of ES. Recently, traditional Chinese medicines (TCMs) have increasingly attracted interest due to the promising clinical results and fewer side-effects for the treatment of cancers. Among the various TCMs, the root of Scutellaria baicalensis exerts anti-inflammatory properties as a well-known herb in traditional Chinese medicine. Baicalein (5,6,7-trihydroxyflavone) derived from the root of Scutellaria baicalensis is a bioactive compound, which possesses a powerful pro-apoptotic activity in various cancers such as hepatocellular carcinoma and myeloma. However, the effects of baicalein on ES cells remain still unknown. We anticipated that baicalein also has apoptotic activity in ES. The aim of the present study was to investigate the effects of baicalein on viability, apoptosis, migration and invasion of ES cells, and further to elaborate the molecular mechanism of baicalein-induced ES cell apoptosis. We found that baicalein markedly inhibited ES cells viability in a time- and dose-dependent manner, especially SK-ES-1 cells and could promote the apoptosis of ES cells. Additionally, baicalein was capable of upregulating the expression of the pro-apoptotic proteins Bax and cytochrome c, reducing the expression of the anti-apoptotic protein Bcl-2, elevating the ratio of Bax/Bcl-2, and triggering the mitochondrial apoptotic pathway, which led to caspase-3 and caspase-9 activation and PARP cleavage. Meanwhile, the activation of caspase-8 and the death receptor pathway was also observed. Besides, baicalein could reduce ES migration and invasion in vitro, which showed its potential to inhibit ES metastasis, besides contributing to the decrease in the expression of matrix metalloproteinases (MMP)-2 and MMP-9. In conclusion, baicalein has a potent tumor-suppressor activity by inducing cell apoptosis through the mitochondrial apoptotic pathway and the death receptor pathway in ES cells, thus it may serve as a novel and effective candidate agent for ES treatment.

Celastrol: A Spectrum of Treatment Opportunities in Chronic Diseases

The identification of new bioactive compounds derived from medicinal plants with significant therapeutic properties has attracted considerable interest in recent years. Such is the case of the Tripterygium wilfordii (TW), an herb used in Chinese medicine. Clinical trials performed so far using its root extracts have shown impressive therapeutic properties but also revealed substantial gastrointestinal side effects. The most promising bioactive compound obtained from TW is celastrol. During the last decade, an increasing number of studies were published highlighting the medicinal usefulness of celastrol in diverse clinical areas. Here we systematically review the mechanism of action and the therapeutic properties of celastrol in inflammatory diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel diseases, osteoarthritis and allergy, as well as in cancer, neurodegenerative disorders and other diseases, such as diabetes, obesity, atherosclerosis, and hearing loss. We will also focus in the toxicological profile and limitations of celastrol formulation, namely, solubility, bioavailability, and dosage issues that still limit its further clinical application and usefulness.

Celastrol-induced apoptosis in human nasopharyngeal carcinoma is associated with the activation of the death receptor and the mitochondrial pathway

Nasopharyngeal carcinoma (NPC) is a cancer that arises from the epithelium of the nasopharynx. Celastrol is a triterpene from traditional Chinese medicine, which demonstrates anti-proliferative activity in several cancer cell lines. However, the effect of celastrol on human NPC and the underlying mechanisms are not yet elucidated. The present study investigated whether celastrol induced apoptosis in human NPC cells, and the underlying molecular mechanisms were explored. Celastrol decreased the viability of HONE-1 and NPC-039 cells in a dose-dependent manner, and induced G1 and G2/M phase cell cycle arrest. The level of cleaved caspases-3, -8, and -9 and poly (ADP-ribose) polymerase 1 increased in cells treated with celastrol. There was an increase in active Bcl-2-like 11 isoform S, Bcl-2-associated X, Bcl-2 antagonist/killer and truncated BH3-interacting death antagonist, and the levels of the anti-apoptotic Bcl-2 and Bcl-2-like 1 decreased. Celastrol induced an increase in Fas, Fas-associated via death domain, TNF receptor superfamily members (TNRSF) 1A and 10B, and TNFRSF1A associated via death domain, and induced a dose-dependent reduction in mitochondrial membrane potential. Celastrol inhibited activation of mitogen-activated protein kinase (MAPK) 1/3 and 14, and induced MAPK 8/9 activation. The results indicated that celastrol induced apoptosis through the death receptor and the mitochondrial pathway in human NPC cells, and is a promising candidate in the development of drugs against NPC.

Assessing the anticancer effects associated with food products and/or nutraceuticals using in vitro and in vivo preclinical development-related pharmacological tests

This review is part of a special issue entitled "Role of dietary pattern, foods, nutrients and nutraceuticals in supporting cancer prevention and treatment" and describes a pharmacological strategy to determine the potential contribution of food-related components as anticancer agents against established cancer. Therefore, this review does not relate to chemoprevention, which is analysed in several other reviews in the current special issue, but rather focuses on the following: i) the biological events that currently represent barriers against the treatment of certain types of cancers, primarily metastatic cancers; ii) the in vitro and in vivo pharmacological pre-clinical tests that can be used to analyse the potential anticancer effects of food-related components; and iii) several examples of food-related components with anticancer effects. This review does not represent a catalogue-based listing of food-related components with more or less anticancer activity. By contrast, this review proposes an original pharmacological strategy that researchers can use to analyse the potential anticancer activity of any food-related component-e.g., by considering the crucial characteristics of cancer biological aggressiveness. This review also highlights that cancer patients undergoing chemotherapy should restrict the use of "food complements" without supervision by a medical nutritionist. By contrast, an equilibrated diet that includes the food-related components listed herein would be beneficial for cancer patients who are not undergoing chemotherapy.

Cathepsin F Knockdown Induces Proliferation and Inhibits Apoptosis in Gastric Cancer Cells

Gastric cancer (GC) is one of the most common cancers in the world. The cathepsin F (CTSF) gene has recently been found to participate in the progression of several types of cancer. However, the clinical characteristics and function of CTSF in GC as well as its molecular mechanisms are not clear. Six GC cell lines and 44 paired adjacent noncancerous and GC tissue samples were used to assess CTSF expression by quantitative polymerase chain reaction (qPCR). We used lentivirus-mediated small hairpin RNA (Lenti-shRNA) against CTSF to knock down the expression of CTSF in GC cells. Western blot and qPCR were used to analyze the mRNA and related protein expression. The biological phenotypes of gastric cells were examined by cell proliferation and apoptosis assays. Microarray-based mRNA expression profile screening was also performed to evaluate the potential molecular pathways in which CTSF may be involved. The CTSF mRNA level was associated with tumor differentiation, depth of tumor invasion, and lymph node metastasis. Downregulation of CTSF expression efficiently inhibited apoptosis and promoted the proliferation of GC cells. Moreover, a total of 1,117 upregulated mRNAs and 1,143 downregulated mRNAs were identified as differentially expressed genes (DEGs). Further analysis identified the involvement of these mRNAs in cancer-related pathways and various other biological processes. Nine DEGs in cancer-related pathways and three downstream genes in the apoptosis pathway were validated by Western blot, which was mainly in agreement with the microarray data. To our knowledge, this is the first report investigating the effect of CTSF on the growth and apoptosis in GC cells and its clinical significance. The CTSF gene may function as a tumor suppressor in GC and may be a potential therapeutic target in the treatment of GC.

Torulene and torularhodin, protects human prostate stromal cells from hydrogen peroxide-induced oxidative stress damage through the regulation of Bcl-2/Bax mediated apoptosis

The current study was designed to elucidate the cytoprotective effects and possible mechanisms of torulene and torularhodin on hydrogen peroxide (H₂O₂)-induced oxidative stress damage in human prostate stromal cells (WPMY-1). After treated with H₂O₂, a notable decrease was appeared in cell viability, yet the decrease was attenuated when cells were pretreated with torulene and torularhodin (0.5-10 μM) as evaluated by WST-1 assay. Pretreatment with these two carotenoids significantly attenuated H₂O₂-induced apoptosis in WPMY-1 cells through the inhibition of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) overproduction, as well as the activation of the activities in catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Finally, pretreatment of cells with carotenoids resulted in the regulation of the mRNA and protein expression of Bcl-2 and Bax in H₂O₂-exposed prostate stromal cells. The present results indicate that both torulene and torularhodin can protect human prostate stromal cells from oxidative stress damage via Bcl-2/Bax mediated apoptosis.

Celastrol negatively regulates cell invasion and migration ability of human osteosarcoma via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro

Osteosarcoma (OS) is a primary malignant tumor of the bone, with a tendency to metastasize early. Despite the advances in treatment options, more than 30% of patients develop distant metastases, and the prognosis of these patients with metastases is extremely poor. Celastrol has been demonstrated to manifest multiple pharmacological activities, including induction of apoptosis in numerous types of cancer cell lines. Our previous studies have also suggested that Celastrol is capable of inducing apoptosis of human osteosarcoma cells via the mitochondrial-dependent pathway. The purpose of this study was to investigate the effects of Celastrol on the migration and invasion of human osteosarcoma U-2OS cells in vitro. Cell migration and invasion were investigated using wound healing and Boyden chamber Transwell assays. We observed that Celastrol suppressed cell invasion and migration in human osteosarcoma U-2OS cells. Furthermore, protein expression levels of phosphorylated phosphatidylinositol 3-kinase (PI3K), Akt, inhibitor of κB kinase α/β, inhibitor of κB α, nuclear factor-κB (NF-κB subunit p65) and matrix metalloproteinase (MMP)-2 and -9 were measured by western blot analysis. We observed that the PI3K/Akt/NF-κB signaling pathway was inhibited following Celastrol treatment. In addition, the expression levels of MMP-2 and -9 proteins were also reduced significantly following Celastrol treatment. Therefore, we confirmed that Celastrol suppressed osteosarcoma U-2OS cell metastasis via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro.

Cell apoptosis, autophagy and necroptosis in osteosarcoma treatment

Osteosarcoma is the most common primary bone tumor in children and adolescents. Although combined therapy including surgery and multi-agent chemotherapy have resulted in great improvements in the overall survival of patients, chemoresistance remains an obstacle for the treatment of osteosarcoma. Molecular targets or effective agents that are actively involved in cell death including apoptosis, autophagy and necroptosis have been studied. We summarized how these agents (novel compounds, miRNAs, or proteins) regulate apoptotic, autophagic and necroptotic pathways; and discussed the current knowledge on the role of these new agents in chemotherapy resistance in osteosarcoma.

Enhanced bioavailability of tripterine through lipid nanoparticles using broccoli-derived lipids as a carrier material

Chemotherapy via the oral route remains a considerable challenge due to poor water-solubility and permeability of anticancer agents. This study aimed to construct lipid nanoparticles using broccoli-derived lipids for oral delivery of tripterine (Tri), a natural anticancer candidate, and to enhance its oral bioavailability. Tri-loaded broccoli lipid nanoparticles (Tri-BLNs) were prepared by a solvent-diffusion method. The resulting Tri-BLNs were 75±10 nm in particle size with entrapment efficiency over 98%. In vitro release study indicated that Tri was almost not released from Tri-BLNs (<2%), whereas the lipolytic experiment showed that Tri-BLNs possessed a relatively strong anti-enzymatic degradation ability to Tri-CLNs (Tri-loaded common lipid nanoparticles). In situ single-pass intestinal perfusion manifested that the effective permeability of Tri-BLNs were significantly higher than that of Tri-CLNs. Further, Tri-BLNs exhibited more efficient cellular uptake in MDCK-II cells as evidenced by flow cytometry and confocal microscopy. The relative bioavailability of Tri-BLNs and Tri-CLNs was 494.13% and 281.95% compared with Tri suspensions, respectively. Depending on the ability in enhancement of biomembrane permeability, broccoli-derived lipids as an alternative source should be useful to construct lipid nanoparticles for bettering oral delivery of drugs with low bioavailability.