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.

Salinomycin exhibits anti-angiogenic activity against human glioma in vitro and in vivo by suppressing the VEGF-VEGFR2-AKT/FAK signaling axis.

Tumor angiogenesis plays a crucial role in tumor growth, progression and metastasis, and suppression of tumor angiogenesis has been considered as a promising anticancer strategy. Salinomycin (SAL), an antibiotic, displays novel anticancer potential against several human cancer cells in vitro and in vivo. However, little information concerning its anti-angiogenic properties is available. Therefore, the anti­angiogenic effect of SAL and the underlying mechanism in human glioma were evaluated in the present study. The results indicated that SAL treatment significantly inhibited human umbilical vein endothelial cell (HUVEC) proliferation, migration, invasion and capillary-like tube formation. Further investigation on intracellular mechanisms showed that SAL markedly suppressed FAK and AKT phosphorylation, and downregulated vascular endothelial growth factor (VEGF) expression in HUVECs. Pretreatment of cells with a PI3K inhibitor (LY294002) and FAK inhibitor (PF562271) markedly enhanced SAL-induced inhibition of HUVEC proliferation and migration, respectively. Moreover, U251 human glioma xenograft growth was also effectively blocked by SAL treatment in vivo via inhibition of angiogenesis involving FAK and AKT depho-sphorylation. Taken together, our findings validated that SAL inhibits angiogenesis and human glioma growth through suppression of the VEGF-VEGFR2-AKT/FAK signaling axis, indicating the potential application of SAL for the treatment of human glioma.

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.

Caudatin induces caspase-dependent apoptosis in human glioma cells with involvement of mitochondrial dysfunction and reactive oxygen species generation.

Caudatin as one species of C-21 steroidal from Cynanchum bungei decne displays potential anticancer activity. However, the underlying mechanisms remain elusive. In the present study, the growth suppressive effect and mechanism of caudatin on human glioma U251 and U87 cells were evaluated in vitro. The results indicated that caudatin significantly inhibited U251 and U87 cell growth in both a time- and dose-dependent manner. Flow cytometry analysis revealed that caudatin-induced cell growth inhibition was achieved by induction of cell apoptosis, as convinced by the increase of Sub-G1 peak, PARP cleavage and activation of caspase-3, caspase-7 and caspase-9. Caudatin treatment also resulted in mitochondrial dysfunction which correlated with an imbalance of Bcl-2 family members. Further investigation revealed that caudatin triggered U251 cell apoptosis by inducing reactive oxygen species (ROS) generation through disturbing the redox homeostasis. Moreover, pretreatment of caspase inhibitors apparently weakens caudatin-induced cell killing, PARP cleavage and caspase activation and eventually reverses caudatin-mediated apoptosis. Importantly, caudatin significantly inhibited U251 tumour xenografts in vivo through induction of cell apoptosis involving the inhibition of cell proliferation and angiogenesis, which further validate its value in combating human glioma in vivo. Taken together, the results described above all suggest that caudatin inhibited human glioma cell growth by induction of caspase-dependent apoptosis with involvement of mitochondrial dysfunction and ROS generation.