Effectively -Terpineol Suppresses Glioblastoma Aggressive Behavior and Downregulates KDELC2 Expression

Background: Glioblastoma (GBM) is notorious for the aggressive behaviors and easily results in chemo-resistance. Studies have shown that the use of herbal medicines as treatments for GBM as limited by the blood -brain barrier (BBB) and glioma stem cells. Purpose: The aim of this study was to investigate the relationship between GBM suppression and alpha-terpineol, the monoterpenoid alcohol derived from Eucalyptus glubulus and Pinus merkusii. Study Design: Using serial in -vitro and in -vivo studies to confirm the mechanism of alpha-terpineol on down -regulating GBM development. Methods: The 3-[4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate IC50 of alpha-terpineol to inhibit GBM cell survival. In order to evaluate the impact of GBM aggressive behaviors by alpha-terpineol, the analysis of cell migration, invasion and colony formation were implemented. In addition, the ability of tumor spheres and WB of CD44 and OCT3/4 were evaluated under the impression of alpha-terpineol decreased GBM stemness. The regulation of neoangiogenesis by alpha-terpineol via the WB of angiogenic factors and human umbilical vein endothelial cells (HUVEC) tube assay. To survey the decided factors of alpha-terpineol downregulating GBM chemoresistance depended on the impact of O6-methylguanine-DNA methyltransferase (MGMT) expression and autophagy-related factors activation. Additionally, WB and quantitative realtime polymerase chain reaction (qRT/PCR) of KDEL (Lys-Asp-Glu-Leu) containing 2 (KDELC2), endoplasmic reticulum (ER) stress, phosphoinositide 3-kinase (PI3k), mammalian target of rapamycin (mTOR) and mitogenactivated protein kinase (MAPK) cascade signaling factors were examined to explore the mechanism of alpha-terpineol inhibiting GBM viability. Finally, the orthotopic GBM mouse model was applied to prove the efficacy and toxicity of alpha-terpineol on regulating GBM survival. Results: alpha-terpineol significantly suppressed GBM growth, migration, invasion, angiogenesis and temozolomide (TMZ) resistance. Furthermore, alpha-terpineol specifically targeted KDELC2 to downregulate Notch and PI3k/ mTOR/MAPK signaling pathway. Finally, we also demonstrated that alpha-terpineol could penetrate the BBB to inhibit GBM proliferation, which resulted in reduced cytotoxicity to vital organs. Conclusion: Compared to published literatures, we firstly proved alpha-terpineol possessed the capability to inhibit GBM through various mechanisms and potentially decreased the occurrence of chemoresistance, making it a promising alternative therapeutic option for GBM in the future.