Caudatin Inhibits Human Glioma Cells Growth Through Triggering DNA Damage-Mediated Cell Cycle Arrest

Caudatin attenuates inflammatory reaction by suppressing JNK/AP-1/NF-κB/caspase-1 pathways in activated HMC-1 cells

One of the interfering factors in Coronavirus disease 2019 (COVID-19) is the cytokine storm, which contributes to hyperinflammation. Mast cells cause COVID-19 hyperinflammation by increasing inflammatory cytokine levels. We investigated whether caudatin, an active compound of Cynanchum auriculatum, could suppress inflammatory response signaling in human mast cell line, HMC-1 cells. Caudatin suppressed activation of c-Jun N-terminal kinase (JNK) and activator protein-1 (AP-1) in HMC-1 cells. Caudatin suppressed nuclear translocation of catalytic subunit (p65) of nuclear factor (NF)-κB by blocking IκBα phosphorylation and degradation. Caudatin also reduced levels of activated-caspase-1 protein and activation of caspase-1. Non-toxic caudatin doses inhibited the mRNA expression and protein synthesis of pro-inflammatory cytokines. A significant finding was that caudatin inhibited JNK/AP-1/NF-κB/caspase-1 signaling molecules, reducing the secretion of inflammatory cytokines. Consequently, we propose that caudatin might be used as a material in health functional foods to alleviate mast cell-mediated inflammatory conditions like COVID-19.

Evaluation of anti-glioma effects of benzothiazoles as efficient apoptosis inducers and DNA cleaving agents

Glioma is the fast-growing, aggressive, and prevalent brain cancer with a great level of morbidity and mortality. Current therapy is usually found insufficient for glioma treatment. In the course of our research attempting to identify effective anti-glioma agents, three benzothiazole derivatives (1-3) were examined on U251 glioma cells. Among these derivatives, compound 3 was found to have the strongest cytotoxic effect on glioma cells with an IC₅₀ value of 9.84 ± 0.64 μM in reference to cisplatin (IC₅₀ = 8.41 ± 1.27 μM). Further mechanism of anti-glioma effects of compound 3 was characterized by the determination of its apoptotic effects in glioma cells and DNA cleaving capacity. Compound 3 caused a significant apoptotic death of U251 cell line. Besides, this compound cleaved DNA with FeSO₄, H₂O₂ and ascorbic acid system. Molecular docking results also showed that compound 3 possessed a significant binding potential to DNA via important π-π stacking interaction with DG-16. Some pharmacokinetic determinants of compound 3 complied with standard limits making it as an efficient bioavailable anti-glioma drug candidate for upcoming exploration.

Cynanchum auriculatum Royle ex Wight., Cynanchum bungei Decne. and Cynanchum wilfordii (Maxim.) Hemsl.: Current Research and Prospects

Cynanchum auriculatum Royle ex Wight. (CA), Cynanchum bungei Decne. (CB) and Cynanchum wilfordii (Maxim.) Hemsl. (CW) are three close species belonging to the Asclepiadaceous family, and their dry roots as the bioactive part have been revealed to exhibit anti-tumor, neuroprotection, organ protection, reducing liver lipid and blood lipid, immunomodulatory, anti-inflammatory, and other activities. Until 2021, phytochemistry investigations have uncovered 232 compounds isolated from three species, which could be classified into C21-steroids, acetophenones, terpenoids, and alkaloids. In this review, the morphology characteristics, species identification, and the relationship of botany, extraction, and the separation of chemical constituents, along with the molecular mechanism and pharmacokinetics of bioactive constituents of three species, are summarized for the first time, and their phytochemistry, pharmacology, and clinical safety are also updated. Moreover, the direction and limitation of current research on three species is also discussed.

Anticancer properties of caudatin and related C-21 steroidal glycosides from Cynanchum plants

Numerous C-21 steroidal glycosides have been isolated from Cynanchum plants. Many of them derive from the aglycone caudatin (CDT) which includes a tetracyclic deacylmetaplexigenin unit and an ikemaoyl ester side chain. CDT can be found in diverse traditional medicines, such as Baishouwu radix used to treat gastro-intestinal disorders. The compound has revealed marked anticancer properties, reviewed here. CDT and its mono-glycoside analogue CDMC display antiproliferative activities against different cancer cell lines in vitro and have revealed significant anticancer effects in tumor xenograft models in vivo. Their mechanism of action is multifactorial, implicating several signaling pathways (Wnt/GSK3/β-catenin, TRAIL/DR5/ER and TNFAIP1/NFκB) which contribute to the antiproliferative, antiangiogenic, antimetastatic and proapoptotic effects of the natural products. CDT also modulates DNA replication, is antioxidant and targets some cancer stem cells. CDT and CDMC are interesting anticancer products, while other CDT glycoside derivatives display antiviral and antifungal activities. Altogether, the present review provides a survey of the pharmacological profiles of CDT and derivatives. The lack of knowledge about the molecular targets of CDT currently limits drug development but the natural product, orally active, warrants further pharmacology and toxicology studies.

CCT128930 induces G1-phase arrest and apoptosis and synergistically enhances the anticancer efficiency of VS5584 in human osteosarcoma cells

Osteosarcoma is a highly invasive primary malignant bone tumor. PI3K/mTOR pathway plays a key role in tumor progression, and inhibition of PI3K/mTOR pathway represents a novel strategy in therapy of osteosarcoma. CCT128930 and VS5584 are both inhibitors of PI3K/mTOR, but the anticancer mechanism of CCT128930 or/and VS5584 against human osteosarcoma cells remains unclear. Herein, U2OS and MG63 human osteosarcoma cells were cultured, and the anticancer effects of CCT128930 alone and the combined effect of CCT128930 and VS5584 against human osteosarcoma cells were explored. The results showed that CCT128930 as PI3K/mTOR inhibitor effectively inhibited p-p70 and p-AKT expression and dose-dependently inhibited U2OS cells and MG63 human osteosarcoma cells growth. Further studies found that CCT128930 triggered significant G-1 phase arrest and apoptosis, as convinced by the dysfunction of p27, Cyclin B1, Cyclin D1 and Cdc2, and PARP cleavage and caspase-3 activation. Moreover, CCT128930 treatment obviously enhanced VS5584-induced growth inhibition and apoptosis in human osteosarcoma cells, followed by enhanced PARP cleavage and caspase-3 activation. Taken together, CCT128930 alone or combined treatment with CCT128930 and VS5584 both effectively inhibited human osteosarcoma cells growth by induction of G1-phase arrest and apoptosis through regulating PI3K/mTOR and MAPKs pathways.

Digitoxin inhibits proliferation of multidrug-resistant HepG2 cells through G2/M cell cycle arrest and apoptosis

Hepatocellular carcinoma (HCC) remains a challenge in the medical field due to its high malignancy and mortality rates particularly for HCC, which has developed multidrug resistance. Therefore, the identification of efficient chemotherapeutic drugs for multidrug resistant HCC has become an urgent issue. Natural products have always been of significance in drug discovery. In the present study, a cell-based method was used to screen a natural compound library, which consisted of 78 compounds, and the doxorubicin-resistant cancer cell line, HepG2/ADM, as screening tools. The findings of the present study led to the shortlisting of one of the compounds, digitoxin, which displayed an inhibitory effect on HepG2/ADM cells, with 50% inhibitory concentration values of 132.65±3.83, 52.29±6.26, and 9.13±3.67 nM for 24, 48, and 72 h, respectively. Immunofluorescence, western blotting and cell cycle analyses revealed that digitoxin induced G₂/M cell cycle arrest via the serine/threonine-protein kinase ATR (ATR)-serine/threonine-protein kinase Chk2 (CHK2)-M-phase inducer phosphatase 3 (CDC25C) signaling pathway in HepG2/ADM cells, which may have resulted from a DNA double-stranded break. Digitoxin also induced mitochondrial apoptosis, which was characterized by changes in the interaction between Bcl-2 and Bax, the release of cytochrome c, as well as the activation of the caspase-3 and −9. To the best of our knowledge, the present study is the first report that digitoxin displays an anti-HCC effect on HepG2/ADM cells through G₂/M cell cycle arrest, which was mediated by the ATR-CHK2-CDC25C signaling pathway and mitochondrial apoptosis. Therefore, digitoxin could be a promising chemotherapeutic agent for the treatment of patients with HCC.

Caudatin Isolated from Cynanchum auriculatum Inhibits Breast Cancer Stem Cell Formation via a GR/YAP Signaling

In the complex tumor microenvironment, cancer stem cells (CSCs), a rare population of cells, are responsible for malignant tumor initiation, metastasis, drug resistance and recurrence. Controlling breast CSCs (BCSCs) using natural compounds is a novel potential therapeutic strategy for clinical cancer treatment. In this study, a mammosphere assay-guided isolation protocol including silica gel, a C18 column, gel filtration, and high-pressure liquid chromatography was used to isolate an inhibitory compound from Cynanchum auriculatum extracts. The isolated inhibitory compound was identified as caudatin. Caudatin inhibited breast cancer cell proliferation, mammosphere formation and tumor growth. Caudatin decreased the CD44⁺/CD24⁻ and aldehyde dehydrogenase⁺ cell proportions and the levels of c-Myc, Oct4, Sox2, and CD44. Caudatin induced ubiquitin (Ub)-dependent glucocorticoid receptor (GR) degradation and blocked subsequent Yes-associated protein (YAP) nuclear accumulation and target gene transcription signals in BCSCs. These results show that the GR/YAP signaling pathway regulates BCSC formation and that caudatin may be a potential chemopreventive agent that targets breast cancer cells and CSCs.

Anticancer effect of caudatin in diethylnitrosamine‑induced hepatocarcinogenesis in rats

An overwhelming endoplasmic reticulum stress (ERS) and the following unfolded protein response (UPR) can induce hepatic inflammation, fibrosis and hepatocellular carcinoma (HCC). Caudatin, one of the species of C-21 steroidal glycosides mainly isolated from the roots of Cynanchum bungei Decne, exhibits potent anticancer activities in vivo. However, the effect of caudatin on HCC remains unclear. In the present study, a diethylnitrosamine (DEN)-induced HCC model was established. Nodules and tumors in rat livers were monitored by T2-/T1-weighted-magnetic resonance imaging (MRI) using a 1.5 T scanner. Caudatin reduced the number and size of nodules and alleviated the inflammatory foci in the liver. In addition, the hepatic pro-inflammatory levels of interleukin (IL) 6, monocyte chemoattractant protein 1 and IL-1β were decreased in caudatin-treated rats. The DEN-induced surge in malondialdehyde, aspartate aminotransferase, alanine transaminase and TBIL were alleviated following caudatin treatment. The expression of ERS chaperones glucose-regulated protein, 94 kDa, glucose-regulated protein, 78 kDa and protein disulfide-isomerase A4 and the proliferation marker Ki-67 in liver nodules were all downregulated by caudatin as demonstrated by immunohistochemistry, reverse transcription-quantitative PCR and western blot analysis. Caudatin reduced the cytoprotective ERS sensor activating transcription factor 6-mediated signal transduction and inhibited the PKR-like endoplasmic reticulum kinase/eukaryotic initiation factor 2α/activating transcription factor 4 pathway. However, the effect of caudatin on inositol requiring enzyme 1 signaling was negligible. In conclusion, restoration of the dysregulated UPR program was involved in the antitumor efficacy of caudatin without inducing cumulative hepatotoxicity.

Cynanchum bungei Decne and its two related species for "Baishouwu": A review on traditional uses, phytochemistry, and pharmacological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Cynanchum bungei Decne. (CB) (Asclepiadaceae) and its two related species Cynanchum auriculatum Royle ex Wight. (CA) and Cynanchum wilfordii (Maxim.) Hemsl. (CW) are well known Chinese herbal medicines known by the name Baishouwu. Among them, CB has long been used for nourishing the kidney and liver, strengthening the bones and muscles, and regulating stomachache. However, to date, no comprehensive review on Baishouwu has been published.

AIM OF THE REVIEW

This review aims to provide a comprehensive summary on traditional uses, phytochemistry, pharmacology, and toxicology of the three herbal components of Baishouwu with the ultimate objective of providing a guide for future scientific and therapeutic potential use of Baishouwu.

MATERIAL AND METHODS

A literature search was undertaken on CB, CA and CW by analyzing the information from scientific databases (SciFinder, Pubmed, Elsevier, Google Scholar, Web of Science, and Baidu Scholar). Information was also gathered from local classic herbal literatures and conference papers on ethnopharmacology and the information provided in this review has been obtained from peer-reviewed papers.

RESULTS

Comparative analysis of literature search indicate that ethnopharmacological use of CB was recorded in China, however, CA and CW have been used in China, Korea and Japan. To date, 151 chemical compounds have been isolated from these species, and the major chemical constituents have been revealed to be acetophenones, C₂₁-steroids, terpenoids, and alkaloids. These compounds and extracts have been proven to exhibit significant pharmacological activities, including anti-tumor, anti-inflammatory, immunomodulatory, hypolipidemic, anti-obesity, hepatoprotective, antifungal, antiviral, anti-depressant, vasodilating and estrogenic activities.

CONCLUSIONS

CB, CA and CW collectively known as Baishouwu are valuable medicinal herbs with multiple pharmacological activities. The traditional use for nourishing liver is closely associated with the hepatoprotective activity. The available literature performs that various of the activity of Baishouwu can be attributed to acetophenones and C₂₁-steroids. It is high time that more efforts should be focused on the underlying mechanisms of their beneficial bioactivities and the structure activity relationship of the constituents, as well as their potential synergistic and antagonistic effects. The proper toxicology evaluation is crucial to guarantee the safety, efficacy, and eligibility for medical use. Further research on the comprehensive evaluation of medicinal quality and the understanding of multi-target network pharmacology of Baishouwu is in great request.

Baishouwu Extract Suppresses the Development of Hepatocellular Carcinoma via TLR4/MyD88/NF-κB Pathway

Purpose: The root of Cynanchum auriculatum Royle ex Wight, known as Baishouwu, has been widely used for a tonic supplement since ancient times. The current study was performed to explore the effect of Baishouwu extract on the development of experimental hepatocellular carcinoma (HCC) and the potential mechanism involved.

Methods: Rats were injected diethylnitrosamine (DEN) to initiate the multistep hepatocarcinogenesis. Animals were treated concurrently with Baishouwu extract given daily by oral gavage for 20 weeks to evaluate its protective effects. Time series sera and organ samples from each group were collected to evaluate the effect of Baishouwu extract on hepatic carcinogenesis.

Results: It was found that Baishouwu extract pretreatment successfully attenuated liver injury induced by DEN, as shown by decreased levels of serum biochemical indicators (AST, ALT, ALP, TP, and T-BIL). Administration of Baishouwu extract inhibited the fibrosis-related index in serum and live tissue, respectively from inflammation stage to HCC stage after DEN treatment. It significantly reduced the incidence and multiplicity of DEN-induced HCC development in a dose-dependent manner. Macroscopic and microscopic features suggested that pretreatment with Baishouwu extract for 20 weeks was effective in inhibiting DEN-induced inflammation, liver fibrosis, and HCC. Furthermore, TLR4 overexpression induced by DEN was decreased by Baishouwu extract, leading to the markedly down-regulated levels of MyD88, TRAF6, NF-κB p65, TGF-β1 and α-SMA in hepatitis, cirrhosis, and hepatocarcinoma.

Conclusion: In conclusion, Baishouwu extract exhibited potent effect on the development of HCC by altering TLR4/MyD88/ NF-κB signaling pathway in the sequence of hepatic inflammation-fibrosis-cancer, which provided novel insights into the mechanism of Baishouwu extract as a candidate for the pretreatment of HCC in the future.

Total C-21 steroidal glycosides, isolated from the root tuber of Cynanchum auriculatum Royle ex Wight, attenuate hydrogen peroxide-induced oxidative injury and inflammation in L02 cells

Oxidative stress plays an important role in the pathology of liver disorders. Total C-21 steroidal glycosides (TCSGs), isolated from the root tuber of Cynanchum auriculatum Royle ex Wight, have been reported to exert numerous effects, including liver protective and antioxidant effects. In order to investigate the potential mechanisms underlying the protective effects of TCSGs on liver function, the present study used the human normal liver cell line, L02, to evaluate the effects of TCSGs on hydrogen peroxide (H₂O₂)-induced oxidative injury and inflammatory responses. The L02 cells were pretreated with various concentrations of TCSGs, followed by exposure to 1.5 mM H₂O₂. Cell viability was determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide (MTT) assay. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and nitric oxide (NO) were measured using colorimetric assays. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the production of malondialdehyde (MDA) were also determined. Intracellular reactive oxygen species (ROS) levels were detected using a fluorescent probe. H₂O₂-induced oxidative toxicity was attenuated following treatment with TCSGs, as indicated by the increase in cell viability, the decreased levels of ALT, AST, LDH, NO, MDA and ROS, and the increased activities of SOD, CAT and GSH-Px. To further explore the possible mechanisms of action of TCSGs, the nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF)-κB pathways were examined. The results revealed that treatment with TCSGs markedly induced Nrf2 nuclear translocation and upregulated the expression of heme oxygenase-1 (HO-1) in the L02 cells damaged by H₂O₂. In addition, pretreatment with TCSGs inhibited the NF-κB signaling pathway by blocking the degradation of the inhibitor of nuclear factor κBα (IκBα), thereby reducing the expression and nuclear translocation of NF-κB, as well as reducing the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2). On the whole, the findings of this study demonstrate that TCSGs can protect L02 cells against H₂O₂-induced oxidative toxicity and inflammatory injury by increasing the expression of Nrf2 and HO-1, mediated by the NF-κB signaling pathway.

Measuring the lactate-to-creatine ratio via 1H NMR spectroscopy can be used to noninvasively evaluate apoptosis in glioma cells after X-ray irradiation

BACKGROUND

Radiotherapy is among the commonly applied treatment options for glioma, which is one of the most common types of primary brain tumor. To evaluate the effect of radiotherapy noninvasively, it is vital for oncologists to monitor the effects of X-ray irradiation on glioma cells. Preliminary research had showed that PKC-ι expression correlates with tumor cell apoptosis induced by X-ray irradiation. It is also believed that the lactate-to-creatine (Lac/Cr) ratio can be used as a biomarker to evaluate apoptosis in glioma cells after X-ray irradiation. In this study, we evaluated the relationships between the Lac/Cr ratio, apoptotic rate, and protein kinase C iota (PKC-ι) expression in glioma cells.

METHODS

Cells of the glioma cell lines C6 and U251 were randomly divided into 4 groups, with every group exposed to X-ray irradiation at 0, 1, 5, 10 and 15 Gy. Single cell gel electrophoresis (SCGE) was conducted to evaluate the DNA damage. Flow cytometry was performed to measure the cell cycle blockage and apoptotic rates. Western blot analysis was used to detect the phosphorylated PKC-ι (p-PKC-ι) level. 1H NMR spectroscopy was employed to determine the Lac/Cr ratio.

RESULTS

The DNA damage increased in a radiation dose-dependent manner (p < 0.05). With the increase in X-ray irradiation, the apoptotic rate also increased (C6, p < 0.01; U251, p < 0.05), and the p-PKC-ι level decreased (C6, p < 0.01; U251, p < 0.05). The p-PKC-ι level negatively correlated with apoptosis, whereas the Lac/Cr ratio positively correlated with the p-PKC-ι level.

CONCLUSION

The Lac/Cr ratio decreases with an increase in X-ray irradiation and thus can be used as a biomarker to reflect the effects of X-ray irradiation in glioma cells.

Cynanbungeigenin C and D, a pair of novel epimers from Cynanchum bungei, suppress hedgehog pathway-dependent medulloblastoma by blocking signaling at the level of Gli

Uncontrolled excessive activation of Hedgehog (Hh) signaling pathway is linked to a number of human malignant tumorigenesis. To obtain valuable Hh pathway inhibitors from natural product, in present study, a pair of novel epimers, Cynanbungeigenin C (CBC) and D (CBD) from the plant Cynanchum bungei Decne were chemically characterized by multiple spectroscopic data and chemical derivatization, and evaluated for their inhibition on Hh pathway. Mechanistically, CBC and CBD block Hh pathway signaling not through targeting Smo and Sufu, but at the level of Gli. In addition, both eipmers significantly suppress Hh pathway-dependent Ptch^+/-; p53^-/- medulloblastoma in vitro and in vivo. Furthermore, both CBC and CBD inhibited two Smo mutants induced Hh pathway activation, which suggested that they are potential compounds for the treatment of medulloblastoma with primary or acquired resistance to current Smo inhibitors. These results highlight the potential of CBC and CBD as effective lead compounds in the treatment of medulloblastoma and other Hh-dependent malignancy.

Selenocysteine antagonizes oxygen glucose deprivation-induced damage to hippocampal neurons

Designing and/or searching for novel antioxidants against oxygen glucose deprivation (OGD)-induced oxidative damage represents an effective strategy for the treatment of human ischemic stroke. Selenium is an essential trace element, which is beneficial in the chemoprevention and chemotherapy of cerebral ischemic stroke. The underlying mechanisms for its therapeutic effects, however, are not well documented. Selenocysteine (SeC) is a selenium-containing amino acid with neuroprotective potential. Studies have shown that SeC can reduce irradiation-induced DNA apoptosis by reducing DNA damage. In this study, the in vitro protective potential and mechanism of action of SeC against OGD-induced apoptosis and neurotoxicity were evaluated in HT22 mouse hippocampal neurons. We cultured HT22 cells in a glucose-free medium containing 2 mM Na₂S₄O₂, which formed an OGD environment, for 90 minutes. Findings from MTT, flow cytometry and TUNEL staining showed obvious cytotoxicity and apoptosis in HT22 cells in the OGD condition. The activation of Caspase-7 and Caspase-9 further revealed that OGD-induced apoptosis of HT22 cells was mainly achieved by triggering a mitochondrial-mediated pathway. Moreover, the OGD condition also induced serious DNA damage through the accumulation of reactive oxygen species and superoxide anions. However, SeC pre-treatment for 6 hours effectively inhibited OGD-induced cytotoxicity and apoptosis in HT22 cells by inhibiting reactive oxygen species-mediated oxidative damage. Our findings provide evidence that SeC has the potential to suppress OGD-induced oxidative damage and apoptosis in hippocampal neurons.

Antiangiogenic properties of caudatin in vitro and in vivo by suppression of VEGF‑VEGFR2‑AKT/FAK signal axis

Tumor angiogenesis provides essential nutrients and oxygen to the tumor microenvironment, which is important in tumor growth, progression and metastasis. Inhibition of tumor angiogenesis represents one of the most promising strategies in tumor therapy. The authors previously demonstrated that caudatin, one species of C‑21 steroidal from Cynanchum auriculatum (C. auriculatum), effectively inhibits human glioma growth in vitro and in vivo through triggering cell cycle arrest and apoptosis. However, little information regarding the antiangiogenic properties of caudatin in human glioma is available. Based on the author's previous study, the antiangiogenic effect of caudatin against human glioma was explored, and the underlying mechanism was investigated. The results suggested that caudatin treatment significantly inhibited HUVEC human umbilical vein endothelial cell proliferation, blocked the HUVECs migration, invasion and capillary‑like tube formation by disturbing the vascular endothelial growth factor (VEGF)‑VEGFR2‑protein kinase B (AKT)/focal adhesion kinase (FAK) signal axis. Notably, caudatin treatment abolished the glioma cell growth by suppression of the in vivo angiogenesis, which involved FAK and AKT dephosphorylation and inhibition of VEGF expression. The findings validated the antiangiogenic potential of caudatin in hunting human glioma.

Selenocysteine induces apoptosis in human glioma cells: evidence for TrxR1-targeted inhibition and signaling crosstalk

Thioredoxin reductase (TrxR) as a selenium (Se)-containing antioxidase plays key role in regulating intracellular redox status. Selenocystine (SeC) a natural available Se-containing amino acid showed novel anticancer potential through triggering oxidative damage-mediated apoptosis. However, whether TrxR-mediated oxidative damage was involved in SeC-induced apoptosis in human glioma cells has not been elucidated yet. Herein, SeC-induced human glioma cell apoptosis was detected in vitro, accompanied by PARP cleavage, caspases activation and DNA fragmentation. Mechanically, SeC caused mitochondrial dysfunction and imbalance of Bcl-2 family expression. SeC treatment also triggered ROS-mediated DNA damage and disturbed the MAPKs and AKT pathways. However, inhibition of ROS overproduction effectively attenuated SeC-induced oxidative damage and apoptosis, and normalized the expression of MAPKs and AKT pathways, indicating the significance of ROS in SeC-induced apoptosis. Importantly, U251 human glioma xenograft growth in nude mice was significantly inhibited in vivo. Further investigation revealed that SeC-induced oxidative damage was achieved by TrxR1-targeted inhibition in vitro and in vivo. Our findings validated the potential of SeC to inhibit human glioma growth by oxidative damage-mediated apoptosis through triggering TrxR1-targeted inhibition.

Combinatorial therapy with adenoviral-mediated PTEN and a PI3K inhibitor suppresses malignant glioma cell growth in vitro and in vivo by regulating the PI3K/AKT signaling pathway

PURPOSE

Glioblastoma is a highly invasive and challenging tumor of the central nervous system. The mutation/deletion of the tumor suppressor phosphatase and tensin homolog (PTEN) gene is the main genetic change identified in glioblastomas. PTEN plays a critical role in tumorigenesis and has been shown to be an important therapeutic target. The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 is commonly used to inhibit glioma cell growth via regulation of the PI3K/AKT signaling pathway. In this study, we examined the growth inhibitory effects of a combinatorial therapy of adenoviral-mediated PTEN (Ad-PTEN) and LY294002 on LN229 and U251 glioma cells in vitro and on tumor xenografts in vivo.

METHODS

In vitro, LN229 and U251 glioma cells were treated by combinatorial therapy with Ad-PTEN and LY294002. The growth ability was determined by MTT assay. The cell cycle distribution was analyzed by flow cytometry. Cell invasive ability was analyzed by transwell invasion assay and cell apoptosis analysis via FITC-Annexin V analysis. In vivo, U251 subcutaneous glioblastoma xenograft was used to assay anti-tumor effect of combinatorial therapy with Ad-PTEN and LY294002 by mean volume of tumors, immunohistochemistry and TUNEL method.

RESULTS

The combinatorial treatment clearly suppressed cell proliferation, arrested the cell cycle, reduced cell invasion and promoted cell apoptosis compared with the Ad-PTEN or LY294002 treatment alone. The treatment worked by inhibiting the PI3K/AKT pathway. In addition, the growth of U251 glioma xenografts treated with the combination of Ad-PTEN and LY294002 was significantly inhibited compared with those treated with Ad-PTEN or LY294002 alone.

CONCLUSIONS

Our data indicated that the combination of Ad-PTEN and LY294002 effectively suppressed the malignant growth of human glioma cells in vitro and in tumor xenografts, suggesting a promising new approach for glioma gene therapy that warrants further investigation.

Assessment of alterations in X-ray irradiation-induced DNA damage of glioma cells by using proton nuclear magnetic resonance spectroscopy

Glioma is one of the most common types of brain tumors. DNA damage is closely associated with glioma cell apoptosis induced by X-ray irradiation. Alterations of metabolites in glioma can be detected noninvasively by proton nuclear magnetic resonance (1H NMR) spectroscopy. To noninvasively explore the micro mechanism in X-ray irradiation-induced apoptosis, the relationship between metabolites and DNA damage in glioma cells was investigated. Three glioma cell lines (C6, U87 and U251) were randomly designated as control (0Gy) and treatment groups (1, 5, 10, 15Gy). After X-ray exposure, each group was separated into four parts: (i) to detect metabolites by 1H NMR spectroscopy; (ii) to make cell colonies; (iii) to detect cell cycle distribution and apoptosis rate by flow cytometry; and (iv) to measure DNA damage by comet assay. The metabolite ratios of lactate/creatine and succinate/creatine decreased (lactate/creatine: C6, 22.17-66.27%; U87, 15.93-44.56%; U251, 26.27-74.48%. succinate/creatine: C6, 14.41-48.35%; U87, 22.03-70.62%; U251, 17.33-60.06%) and choline/creatine increased (C6, 52.22-389.68%; U87, 56.15-82.36%; U251, 31.87-278.62%) in the treatment groups compared with the control group (each P<0.05), which linearly depended on DNA damage. An increasing dose of X-ray irradiation increased numbers of apoptotic cells (P<0.01), and the DNA damage parameters were dose-dependent (P<0.05). The colony-forming rate declined (P<0.01) and the percentage of cells at G1 stage increased when exposed to 1Gy X-ray (three cell lines, P<0.05). Metabolite alterations detected by 1H NMR spectroscopy can be used to determine DNA damage induced by X-ray irradiation. 1H NMR spectroscopy is a noninvasive method to predict DNA damage of glioma cell at the micro level.

Induction of G1 Cell Cycle Arrest in Human Glioma Cells by Salinomycin Through Triggering ROS-Mediated DNA Damage In Vitro and In Vivo

Chemotherapy has always been one of the most effective ways in combating human glioma. However, the high metastatic potential and resistance toward standard chemotherapy severely hindered the chemotherapy outcomes. Hence, searching effective chemotherapy drugs and clarifying its mechanism are of great significance. Salinomycin an antibiotic shows novel anticancer potential against several human tumors, including human glioma, but its mechanism against human glioma cells has not been fully elucidated. In the present study, we demonstrated that salinomycin treatment time- and dose-dependently inhibited U251 and U87 cells growth. Mechanically, salinomycin-induced cell growth inhibition against human glioma was mainly achieved by induction of G1-phase arrest via triggering reactive oxide species (ROS)-mediated DNA damage, as convinced by the activation of histone, p53, p21 and p27. Furthermore, inhibition of ROS accumulation effectively attenuated salinomycin-induced DNA damage and G1 cell cycle arrest, and eventually reversed salinomycin-induced cytotoxicity. Importantly, salinomycin treatment also significantly inhibited the U251 tumor xenograft growth in vivo through triggering DNA damage-mediated cell cycle arrest with involvement of inhibiting cell proliferation and angiogenesis. The results above validated the potential of salinomycin-based chemotherapy against human glioma.