Atranorin Impedes Glioma Invasiveness and Progression by Inhibiting the Epithelial‐Mesenchymal Transition and Stemness in Monotherapy and in Combination Therapy With Temozolomide

Lichens are commensal organisms that contain secondary metabolites such as atranorin, which have intrinsic bioactive properties, including anticancer effects. The present study aimed to investigate the therapeutic potential and molecular mechanisms of atranorin and its hydrolytic derivatives in monotherapy and in combination treatment with temozolomide in glioma. The effects of atranorin on gliomas were investigated using an MTT assay, transwell invasion assay, spheroid formation assay, clonogenic assay, reporter assay, western blotting, quantitative real-time PCR, an orthotopic mouse glioma model with in vivo bioluminescence imaging, and immunohistochemical staining. Here, we found that atranorin inhibited glioma cell invasion and spheroid formation by downregulating epithelial-mesenchymal transition (EMT) and cancer stemness regulators and markers. The atranorin hydrolytic derivatives atraric acid and haematommic acid inhibited glioma cell invasiveness and stemness, respectively. Also, major oncogenic signaling pathways-Wnt, AP-1, STAT, Hedgehog, Notch, and NF-κB-were investigated, revealing that atranorin robustly decreased the transcriptional activities of TOPFLASH, AP-1, Gli, CBF1/Su(H)/Lag-1, hairy/enhancer of Split, and expression of the related downstream targets such as β-catenin, cyclin-D1, c-myc, c-Jun, c-Fos, Gli1, Gli2, Smoothened, and Notch 1 intracellular domain. Moreover, atranorin-mediated upregulation of Dusp3 and Ptpn1 suppressed the invasiveness and stemness of gliomas by dephosphorylating STAT and NF-κB. Importantly, atranorin exerts synergistic antiglioma effects on invasion and spheroid formation in combination treatment with temozolomide. These findings identified that atranorin could be developed as a specific therapy to target EMT and CSC pathways to suppress malignant behaviors in glioma.