Downregulation of BASP1 promotes temozolomide resistance in gliomas via epigenetic activation of the FBXO32/NF-κB/MGMT axis.

The chemoresistance of temozolomide (TMZ)-based therapy is a serious limitation for lasting effective treatment of gliomas, while the underlying mechanisms remain unclear. In this study, we showed that downregulation of BASP1 correlated negatively with the response to TMZ therapy and disease-free survival of patients with gliomas. Silencing BASP1 significantly enhanced the TMZ-resistance of glioma cells both in vitro and in vivo through repair of TMZ-induced DNA damage via activation of the FBXO32/NF-κB/MGMT axis in both MGMT methylated and unmethylated gliomas. We demonstrated that loss of BASP1 resulted in removal of TRIM37/EZH2 complex-induced repressive histone modifications, including H2A-ub and H3K27me3, but addition of WDR5/MLL complex-mediated active histone modifications, including H3K4me3 and H3K9ac, on the FBXO32 promoter, which elicited in FBXO32 upregulation and further activated NF-κB/MGMT signaling via ubiquitin-dependent degradation of IκBα. Importantly, treatment with OICR-9429, an antagonist of the WDR5-MLL interaction, impaired the FBXO32/NF-κB/MGMT axis-mediated repair of TMZ-induced DNA damage, leading to significant apoptosis of BASP1-downregulated glioma cells. These findings shed light on the molecular mechanism underlying BASP1-mediated epigenetic transcriptional repression and may represent a potential strategy in the fight against TMZ-resistant gliomas. Implications: BASP1 downregulation promotes TMZ resistance in gliomas through WDR5/MLL complex-mediated epigenetic activation of the FBXO32/NF-κB/MGMT axis, providing new target for improving outcomes in patients with TMZ-resistant gliomas.