Transformed astrocytes confer temozolomide resistance on glioblastoma via delivering ALKBH7 to enhance APNG expression after educating by glioblastoma stem cells‐derived exosomes

• Published in: CNS neuroscience & therapeutics 2024-02, Vol.30 (2), p.e14599-n/a
• Main Authors: Liu, Xinglei, Liu, Liang, Wu, Anyi, Huang, Shilu, Xu, Zhipeng, Zhang, Xiaopei, Li, Zengyang, Li, Haoran, Dong, Jun
• Format: Article
• Language: English
• Subjects: Adult; AlkB Enzymes; ALKBH7; Antibodies; Antineoplastic Agents, Alkylating - pharmacology; Antineoplastic Agents, Alkylating - therapeutic use; APNG; APNG gene; Apoptosis; Astrocytes; Astrocytes - metabolism; Brain Neoplasms - genetics; Brain tumors; CD44 antigen; Cell culture; Cell Line, Tumor; Centrifugation; Cytotoxicity; Drug resistance; Drug Resistance, Neoplasm; Enzyme-linked immunosorbent assay; Exosomes; Exosomes - metabolism; Flow cytometry; Gene expression; Genetic transformation; Glial cells; Glioblastoma; Glioblastoma - pathology; glioblastoma stem cells‐derived exosomes; Humans; Mitochondrial Proteins; Proteins; Stem cells; Stem Cells - metabolism; Temozolomide; Temozolomide - pharmacology; Temozolomide - therapeutic use; Tenascin; Tenascin C; TMZ resistance; Transformed cells; Transforming growth factor-b; tumor‐associated astrocytes; Western blotting; Xenograft Model Antitumor Assays
• ISSN: 1755-5930; 1755-5949
• DOI: 10.1111/cns.14599

Background Glioblastoma is the most malignant primary brain tumor in adults. Temozolomide (TMZ) stands for the first‐line chemotherapeutic agent against glioblastoma. Nevertheless, the therapeutic efficacy of TMZ appears to be remarkably limited, because of low cytotoxic efficiency against glioblastoma. Besides, various mechanical studies and the corresponding strategies fail to enhancing TMZ curative effect in clinical practice. Our previous studies have disclosed remodeling of glial cells by GSCs, but the roles of these transformed cells on promoting TMZ resistance have never been explored. Methods Exosomes were extracted from GSCs culture through standard centrifugation procedures, which can activate transformation of normal human astrocytes (NHAs) totumor‐associated astrocytes (TAAs) for 3 days through detect the level of TGF‐β, CD44 and tenascin‐C. The secretive protein level of ALKBH7 of TAAs was determined by ELISA kit. The protein level of APNG and ALKBH7 of GBM cells were determined by Western blot. Cell‐based assays of ALKBH7 and APNG triggered drug resistance were performed through flow cytometric assay, Western blotting and colony formation assay respectively. A xenograft tumor model was applied to investigate the function of ALKBH7 in vivo. Finally, the effect of the ALKBH7/APNG signaling on TMZ resistance were evaluated by functional experiments. Results Exosomes derived from GSCs can activate transformation of normal human astrocytes (NHAs)to tumor‐associated astrocytes (TAAs), as well as up‐regulation of ALKBH7expression in TAAs. Besides, TAAs derived ALKBH7 can regulate APNG gene expression of GBM cells. After co‐culturing with TAAs for 5 days, ALKBH7 and APNG expression in GBM cells were elevated. Furthermore, Knocking‐down of APNG increased the inhibitory effect of TMZ on GBM cells survival. Conclusion The present study illustrated a new mechanism of glioblastoma resistance to TMZ, which based on GSCs‐exo educated TAAs delivering ALKBH7 to enhance APNG expression of GBM cells, which implied that targeting on ALKBH7/APNG regulation network may provide a new strategy of enhancing TMZ therapeutic effects against glioblastoma. ALKBH7 was upregulated in TAAs, which were stimulated by GSC‐derived exosomes. Next, ALKBH7 can be transported into GBM cells and lead to upregulation of APNG. These results further illustrated the mechanism of the ALKBH7/APNG axis contributing to TMZ resistance.