Effects of triptolide on radiosensitivity of human glioma cells and its mechanism.

PURPOSE: To study the effect of triptolide (TP) on radiosensitivity of human glioma U251 cells and its mechanism, so as to provide new ideas and methods for the radiotherapy of glioma. METHODS: U251 cells were treated with 10, 50, 100 nmol/L TP at different concentrations and irradiated with 0, 2, 4, 6, 8 Gy X-ray. The radiosensitivity of cells in each group were detected by MTT. U251 cells were then divided into control group, 10 nmol/L TP group, 4 Gy radiation group, 10 nmol/L TP + 4 Gy radiation group. The formation ability of U251 cells in each group was detected by colony formation assay. Flow cytometry was used to detect cell cycle and apoptosis in each group. Western blot was used to detect the changes of PI3K/Akt signal pathway in each group. RESULTS: When 10, 50, 100 nmol/L TP were combined with 2, 4, 6, 8 Gy X-ray, the proliferation inhibition rate of U251 cells in each group increased significantly (p<0.05); compared with 10 nmol/L TP alone group and 4 Gy radiation alone group, the colony formation ability rate of U251 cells in 10 nmol/L TP + 4Gy radiation combined group decreased significantly (p<0.05), the cell cycle was blocked in G1 phase, and the apoptosis rate was significantly reduced (p<0.05). The level of p-pi3k and p-Akt decreased significantly (p<0.05). CONCLUSION: Triptolide could significantly increase the radiosensitivity of human glioma U251 cells and play a role by inhibiting the PI3K/Akt signal pathway.

Construction of low melting point alloy/graphene three-dimensional continuous thermal conductive pathway for improving in-plane and through-plane thermal conductivity of poly(vinylidene fluoride) composites.

As the temperature of hot spots increases in electronic devices, thermal management is a key issue for maintaining a device's reliability and performance. The usual approaches of quickly extracting the heat from the hot spots have focused on aligning two-dimensional filler along the in-plane orientation in the polymer matrix. Meanwhile, improving the through-plane thermal conductivity of polymer-based composites is as important as in-plane thermal conductivity. In this study, poly(vinylidene fluoride) composites with three-dimensional continuous thermal conductive pathways of a low melting point alloy (LMPA)/graphene were prepared through a two-step method. Poly(vinylidene fluoride)@graphene (PVDF@Gr) microspheres were firstly prepared by an in-situ water-vapor induced phase separation method. Subsequently, PVDF@Gr/LMPA composites were obtained by hot-pressing after mixing the LMPA with the PVDF@Gr microspheres. Attributed to the unique solid-liquid phase transition advantage of the LMPA and the good matching of the phonon power spectrum between the LMPA and the graphene, the PVDF@4.8Gr/10LMPA composites with 4.8 vol% graphene and 10.0 vol% LMPA exhibited an outstanding in-plane thermal conductivity of 9.41 W m-1 K-1 and through-plane thermal conductivity of 0.35 W m-1 K-1, which was nearly increased by 245% and 130% compared to that of the PVDF@4.8Gr composites, respectively. The enhanced elasticity modulus and reduced thermal expansion coefficient were attributed to the LMPA constructing a three-dimensional continuous thermal conductive pathway along with the graphene and reducing interface thermal resistance. This study offeres a straightforward and repeatable method for fabricating highly thermally conductive polymer composites and widens the application of LMPAs in the fields of thermal management.

Oncogenic Ras is downregulated by ARHI and induces autophagy by Ras/AKT/mTOR pathway in glioblastoma.

BACKGROUND: Glioblastoma is a disease with high heterogeneity that has long been difficult for doctors to identify and treat. ARHI is a remarkable tumor suppressor gene in human ovarian cancer and many other cancers. We found over-expression of ARHI can also inhibit cancer cell proliferation, decrease tumorigenicity, and induce autophagic cell death in human glioma and inhibition of the late stage of autophagy can further enhance the antitumor effect of ARHI through inducing apoptosis in vitro or vivo. METHODS: Using MTT assay to detect cell viability. The colony formation assay was used to measure single cell clonogenicity. Autophagy associated morphological changes were tested by transmission electron microscopy. Flow cytometry and TUNEL staining were used to measure the apoptosis rate. Autophagy inhibitor chloroquine (CQ) was used to study the effects of inhibition at late stage of autophagy on ARHI-induced autophagy and apoptosis. Protein expression were detected by Western blot, immunofluorescence and immunohistochemical analyses. LN229-derived xenografts were established to observe the effect of ARHI in vivo. RESULTS: ARHI induced autophagic death in glioma cells, and blocking late-stage autophagy markedly enhanced the antiproliferative activites of ARHI. In our research, we observed the inhibition of RAS-AKT-mTOR signaling in ARHI-glioma cells and blockade of autophagy flux at late stage by CQ enhanced the cytotoxicity of ARHI, caused accumulation of autophagic vacuoles and robust apoptosis. As a result, the inhibition of RAS augmented autophagy of glioma cells. CONCLUSION: ARHI may also be a functional tumor suppressor in glioma. And chloroquine (CQ) used as an auxiliary medicine in glioma chemotherapy can enhance the antitumor effect of ARHI, and this study provides a novel mechanistic basis and strategy for glioma therapy.

Peiminine Inhibits Glioblastoma in Vitro and in Vivo Through Cell Cycle Arrest and Autophagic Flux Blocking.

BACKGROUND/AIMS: Glioblastoma multiforme (GBM) is the most devastating and widespread primary central nervous system tumour in adults, with poor survival rate and high mortality rates. Existing treatments do not provide substantial benefits to patients; therefore, novel treatment strategies are required. Peiminine, a natural bioactive compound extracted from the traditional Chinese medicine Fritillaria thunbergii, has many pharmacological effects, especially anticancer activities. However, its anticancer effects on GBM and the underlying mechanism have not been demonstrated. This study was conducted to investigate the potential antitumour effects of peiminine in human GBM cells and to explore the related molecular signalling mechanisms in vitro and in vivo Methods: Cell viability and proliferation were detected with MTT and colony formation assays. Morphological changes associated with autophagy were assessed by transmission electron microscopy (TEM). The cell cycle rate was measured by flow cytometry. To detect changes in related genes and signalling pathways in vitro and in vivo, RNA-seq, Western blotting and immunohistochemical analyses were employed. RESULTS: Peiminine significantly inhibited the proliferation and colony formation of GBM cells and resulted in changes in many tumour-related genes and transcriptional products. The potential anti-GBM role of peiminine might involve cell cycle arrest and autophagic flux blocking via changes in expression of the cyclin D1/CDK network, p62 and LC3. Changes in Changes in flow cytometry results and TEM findings were also observed. Molecular alterations included downregulation of the expression of not only phospho-Akt and phospho-GSK3ß but also phospho-AMPK and phospho-ULK1. Furthermore, overexpression of AKT and inhibition of AKT reversed and augmented peiminine-induced cell cycle arrest in GBM cells, respectively. The cellular activation of AMPK reversed the changes in the levels of protein markers of autophagic flux. These results demonstrated that peiminine mediates cell cycle arrest by suppressing AktGSk3ß signalling and blocks autophagic flux by depressing AMPK-ULK1 signalling in GBM cells. Finally, peiminine inhibited the growth of U251 gliomas in vivo. CONCLUSION: Peiminine inhibits glioblastoma in vitro and in vivo via arresting the cell cycle and blocking autophagic flux, suggesting new avenues for GBM therapy.

Nitazoxanide, an antiprotozoal drug, inhibits late-stage autophagy and promotes ING1-induced cell cycle arrest in glioblastoma.

Glioblastoma is the most common and aggressive primary brain tumor in adults. New drug design and development is still a major challenge for glioma treatment. Increasing evidence has shown that nitazoxanide, an antiprotozoal drug, has a novel antitumor role in various tumors and exhibits multiple molecular functions, especially autophagic regulation. However, whether nitazoxanide-associated autophagy has an antineoplastic effect in glioma remains unclear. Here, we aimed to explore the underlying molecular mechanism of nitazoxanide in glioblastoma. Our results showed that nitazoxanide suppressed cell growth and induced cell cycle arrest in glioblastoma by upregulating ING1 expression with a favorable toxicity profile. Nitazoxanide inhibited autophagy through blockage of late-stage lysosome acidification, resulting in decreased cleavage of ING1. A combination with chloroquine or Torin1 enhanced or impaired the chemotherapeutic effect of nitazoxanide in glioblastoma cells. Taken together, these findings indicate that nitazoxanide as an autophagy inhibitor induces cell cycle arrest in glioblastoma via upregulated ING1 due to increased transcription and decreased post-translational degradation by late-stage autophagic inhibition.

Raddeanin a Suppresses Glioblastoma Growth by Inducing ROS Generation and Subsequent JNK Activation to Promote Cell Apoptosis.

BACKGROUND/AIMS: Raddeanin A (RA), an active pharmacological ingredient from Anemone raddeana Regel, plays an important role in tumor suppression. In this study, we assessed the potentially therapeutic effect of RA on glioblastoma and its underlying mechanisms. METHODS: Cell viability was examined using the MTT assay. Invasive and migratory capacities were examined using Transwell and wound healing assays. Apoptosis was determined by Hoechst staining, flow cytometry, DCFH-fluorescent probe and immunohistochemical staining. Autophagy was detected by transmission electron microscopy and western blotting. A U251 glioma xenograft model was established to evaluate the effect of RA in vivo. RESULTS: The data demonstrated that RA inhibited viability, and abrogated the invasive/migratory abilities of glioblastoma cells. In addition, RA induced apoptosis by reactive oxygen species (ROS)/ Jun N-terminal kinase (JNK) signaling in glioblastoma. Conversely, the antioxidant N-Acetyl-L-cysteine (NAC) and pan-caspase inhibitor z-VAD-fmk attenuated RA-induced apoptosis by scavenging ROS and inactivating caspase-3. Furthermore, the inhibition of autophagy by 3-MA exacerbated apoptosis through ROS generation and JNK phosphorylation. In vivo, RA exhibited a curative effect on U251-derived xenografts in nude mice. CONCLUSIONS: The results of this study suggest that RA suppressed the growth of glioblastoma, thus serving as a promising and potential strategy for glioblastoma chemotherapy.

Isogambogenic Acid Inhibits the Growth of Glioma Through Activation of the AMPK-mTOR Pathway.

BACKGROUND/AIMS: Glioma is the most devastating cancer in the brain and has a poor prognosis in adults. Therefore, there is a critical need for novel therapeutic strategies for the management of glioma patients. Isogambogenic acid, an active compound extracted from the Chinese herb Garcinia hanburyi, induces autophagic cell death. METHODS: Cell viability was detected with MTT assays. Cell proliferation was assessed using the colony formation assay. Morphological changes associated with autophagy and apoptosis were tested by TEM and Hoechst staining, respectively. The apoptosis rate was measured by flow cytometry. Western blot, immunofluorescence and immunohistochemical analyses were used to detect protein expression. U87-derived xenografts were established for the examination of the effect of isogambogenic acid on glioma growth in vivo. RESULTS: Isogambogenic acid induced autophagic death in U87 and U251 cells, and blocking late-stage autophagy markedly enhanced the antiproliferative activities of isogambogenic acid. Moreover, we observed the activation of AMPK-mTOR signalling in isogambogenic acid-treated glioma cells. Furthermore, the activation of AMPK or the inhibition of mTOR augmented isogambogenic acid-induced autophagy. Inhibition of autophagy attenuated apoptosis in isogambogenic acid-treated glioma cells. Finally, isogambogenic acid inhibited the growth of U87 glioma in vivo. CONCLUSION: Isogambogenic acid inhibits the growth of glioma via activation of the AMPK-mTOR signalling pathway, which may provide evidence for future clinical applications in glioma therapy.