Search for a command to run...
Jiranan Chotitumnavee,1 Peeratchai Seemaung,1 Rapeewan Settacomkul,2 Ratchanon Sukprasert,2 Yukihiro Itoh,3 Takayoshi Suzuki,4 Sirada Srihirun,1 Christopher Power,5 Pornpun Vivithanaporn2 1Department of Pharmacology, Faculty of Dentistry, Mahidol University, Bangkok, Thailand; 2Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand; 3Laboratory for Biomaterials and Bioengineering, Institute of Integrated Research, Institute of Science Tokyo, Tokyo, Japan; 4SANKEN, The University of Osaka, Osaka, Japan; 5Department of Medicine, University of Alberta, Alberta, CanadaCorrespondence: Pornpun Vivithanaporn, Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand, Email pornpun.viv@mahidol.ac.thIntroduction: Histone deacetylase 8 (HDAC8) plays a role in glioblastoma progression, making it a promising therapeutic target. While HDAC8 inhibitors (HDAC8is) suppress glioblastoma growth and prolong survival in animal models, they do not eliminate HDAC8. In contrast, HDAC8-targeting proteolysis-targeting chimera (PROTAC), a selective HDAC8 degrader, induces proteasomal degradation of HDAC8 and thus eliminates all of its functions.Purpose: In this study, we investigated the antitumor activity and underlying mechanisms of a previously reported HDAC8 PROTAC in glioblastoma cells.Methods: Cytotoxicity in glioblastoma-derived U-87 MG, A172 and T98G cells and primary human astrocytes (PHA) was assessed via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assays. Live-cell imaging was performed using an Incucyte® Live-Cell Analysis System. Cell proliferation, cell cycle distribution, and apoptosis were analyzed using flow cytometry. HDAC8 and key regulators of cell cycle and apoptosis were quantified via Western blotting.Results: HDAC8 PROTAC effectively degraded HDAC8 and exhibited cytotoxic and antiproliferative effects in human glioblastoma cells, while demonstrating minimal toxicity in PHA. It induced S-phase arrest and reduced Cdk1, Cdk2, Cdk4, Cdk6, and cyclin B1 expression. It elevated caspase-3/7 activation, downregulated Bcl-2, induced apoptosis, and upregulated key endoplasmic reticulum (ER) stress response proteins, including BiP, XBP1s, CHOP, and p-JNK in U-87 MG glioblastoma cells. The HDAC8 PROTAC demonstrated stronger antitumor activity than HDAC8i and pan-HDACi vorinostat. Moreover, the HDAC8 PROTAC showed selective toxicity toward glioblastoma cells compared to primary human astrocytes.Conclusion: HDAC8 PROTAC selectively suppressed glioblastoma cell growth and viability by arresting the cell cycle and inducing ER stress-mediated apoptosis via the IRE1α/XBP1s–JNK–CHOP pathway. Hence, HDAC8 PROTAC is a potential therapeutic agent for glioblastoma treatment.Keywords: HDAC8, PROTAC, HDAC8 degradation, cell cycle arrest, apoptosis, endoplasmic reticulum stress