Ovatodiolide inhibits the oncogenicity and cancer stem cell-like phenotype of glioblastoma cells, as well as potentiate the anticancer effect of temozolomide

Abstract

BackgroundOvatodiolide (Ova), a major bioactive diterpenoid isolate of Anisomeles indica has drawn considerable attention lately as an effective anticancer agent with several published works demonstrating its tumor-inhibitory activity in various cancer types. PurposeIn this study, we examined the modulatory effect of Ova on the oncogenicity, proliferation, and cancer stem cell-like traits of glioblastoma (GBM) cells, as well as investigated the underlying molecular mechanism for the anticancer activity of Ova in GBM cell lines, U-87MG and GBM8401. MethodsThe antiproliferative, apoptotic, and stemness-attenuating effects of Ova were evaluated using the sulforhodamine B (SRB) colorimetric assay, western blot and fluorescent immunocytochemistry. Cell apoptosis was analyzed based on variation in the expression levels of Bcl-2 family of regulator proteins Bax, Bak, Bcl-2 and Bcl-xL. ResultsOva induced the apoptosis of the U-87MG and GBM8401 cells, as well as effectively inhibited the proliferation and motility of the GBM cell lines in a dose- and time-dependent manner. Ova-induced apoptosis correlated with increased Bax/Bcl-2 ratio, while inhibition of tumor cell migration and colony formation was associated with reduced Slug, Vimentin, NCadherin and β-catenin protein expression and increased E-Cadherin. In addition, exposure to Ova inhibited tumorsphere formation, elicited downregulation of CD44, CD133, Sox2, and Oct4, as well as correlated with dysregulation of the JAK2-STAT3 signaling pathway. Furthermore, we showed for the first time to the best of our knowledge that Ova potentiate the chemotherapeutic effect of Temozolomide. ConclusionTaken together, our findings demonstrate the anticancer potential of Ova in GBM and its efficacy in the treatment of GBM as monotherapy and in combination with Temozolomide.