Cytocidal effects of arenobufagin and hellebrigenin, two active bufadienolide compounds, against human glioblastoma cell line U-87

Abstract

Glioblastoma is the most common and lethal intracranial tumor type, characterized by high angiogenic and infiltrative capacities. To provide a novel insight into therapeutic strategies against glioblastoma, the cytotoxicity of arenobufagin and hellebrigenin was investigated in the human glioblastoma cell line, U-87. Similar dose-dependent cytotoxicity was observed in the cells, whereas no detectable toxicity was confirmed in mouse primary astrocytes. Treatment with each drug downregulated the expression levels of Cdc25C, Cyclin B1 and survivin, which occurred in parallel with G2/M phase arrest. Necrotic-like cell death was only observed in the cells treated with a relatively high concentration (>100 ng/ml). These results indicate that the two drugs exhibited distinct cytotoxicity against cancerous glial cells with high potency and selectivity, suggesting that growth inhibition associated with G2/M phase arrest and/or necrosis were attributed to their toxicities. Activation of the p38 mitogen activated protein kinase (MAPK) signaling pathway was also observed in treated cells. Notably, a specific inhibitor of p38 MAPK, SB203580, itself caused a significant decrease in cell viability, and further enhanced the cytotoxicity of the two drugs, suggesting an important pro-survival role for p38 MAPK. Given that p38 MAPK serves an essential role in promoting glioblastoma cell survival, developing a novel combination regimen of arenobufagin/hellebrigenin plus a p38 MAPK inhibitor may improve the efficacy of the two drugs, and may provide more therapeutic benefits to patients with glioblastoma. The qualitative assessment demonstrated the existence of arenobufagin in the cerebrospinal fluid of arenobufagin-treated rats, supporting its clinical application.

Cytotoxic Effects of Arsenite in Combination With Gamabufotalin Against Human Glioblastoma Cell Lines

“…Bufadienolides are the major effective constituents of cinobufacini (also known as Huachansu), a well-known Chinese medicine that comes from the dried skin of Bufo bufo gargarizans Cantor, and cinobufacini has been employed to treat patients with different types of cancers such as hepatoma, gallbladder carcinoma, and lung cancer ( 15 – 17 ). We previously clarified that active bufadienolide compounds such as gamabufotalin and arenobufagin showed selective cytocidal effects against intractable cancer cells such as glioblastoma, but minimal effects on human normal peripheral blood mononuclear cells (PBMCs) ( 18 ) and mouse primary astrocytes ( 19 ). Notably, nearly non-toxic gamabufotalin concentrations on PBMCs effectively reduced the percentages of T-regulatory cells (Treg) cells ( 18 ), which has been characterized to play a critical role in limiting antitumor immune response and promoting immunological ignorance in cancer ( 20 – 22 ), suggesting the capability of gamabufotalin to enhance antitumor immunity.…”

“…It has been demonstrated that cell cycle arrest, necrotic and autophagic cell death contribute to cytocidal effect of chemotherapeutic agents ( 19 , 25 – 27 ). Cell cycle is coordinately and tightly regulated by the cyclin-dependent kinases (CDKs) and their associated regulatory cyclins (CDK/Cyclin complexes) ( 28 , 29 ).…”

“…In addition, p38 kinase, a member of the mitogen-activated protein kinases (MAPKs) family, has been considered to be positively related to diverse cellular processes including cell cycle arrest and cell death signaling ( 31 – 33 ). Inversely, a novel prosurvival role of p38 MAPK has been demonstrated in human cancer cells such as glioblastoma cells ( 19 , 34 – 36 ). Despite this, the molecular events underlying the potential cytotoxic effects caused by As III and gamabufotalin, alone or in combination, against glioblastoma cells remain to be seen.…”

Bersaldegenin-1,3,5-orthoacetate induces caspase-independent cell death, DNA damage and cell cycle arrest in human cervical cancer HeLa cells

“…These authors also studied arenobufagin and hellebrigenin on human glioblastoma cell line U-87 (Han et al. 2018 ). Dose-dependent cytotoxicity was observed in these cells at the compounds concentration of about 20 ng/mL.…”

Arenobufagin Promoted Oxidative Stress‐Associated Mitochondrial Pathway Apoptosis in A549 Non‐Small‐Cell Lung Cancer Cell Line

“…Anyway, a lot of studies have demonstrated its broadspectrum antitumor activities in cancers such as breast cancer, pancreatic carcinoma, and liver cancer [12][13][14]. We previously found that ARE can induce liver cancer cell apoptosis and autophagy through PI3K/Akt/mTOR signal routing [14]; induce cell cycle arrest and apoptosis in human cervical cancer HeLa cells [15]; have anticancer effect on human esophageal squamous cell carcinoma (its mechanism of exerting anticancer efficacy may be activation of cysteinecontaining aspartate proteolytic enzyme (caspase) by endogenous and exogenous pathways); promote apoptosis of esophageal cancer cells by enhancing caspase phosphorylation and activating p53 signaling [16]; promote apoptosis of human glioblastoma U-87 cells by inhibiting p38MAPK signaling pathway [17]; and inhibit epithelial-mesenchymal conversion by going down the β-catenin pathway, consequently repressing motility and invasiveness of prostate cancer PC3 cells [18]. Nevertheless, the role and mechanisms of ARE on NSCLC remain unclear.…”