UCHL1 promotes temozolomide resistance in glioblastoma by inhibiting the ubiquitination-mediated degradation of keratin 8

• This article is the first to reveal the role of UCHL1 in temozolomide resistance. • UCHL1 Knockdown enhances glioblastoma sensitivity to temozolomide. • UCHL1 promotes temozolomide resistance by stabilizing KRT8 in glioblastoma cells. • Targeting the UCHL1-KRT8 axis may help overcome temozolomide resistance. Background: Resistance to temozolomide (TMZ)-based chemotherapy is a major cause of progression and recurrence in patients with glioblastoma. Although the deubiquitinating enzyme ubiquitin C-terminal hydrolase L1 (UCHL1) has been implicated in tumor chemoresistance, its roles and underlying mechanisms in TMZ resistance remain unclear. Methods: Bioinformatics analyses and immunohistochemistry were used to assess the prognostic significance and the levels of UCHL1 in glioma specimens. Co-immunoprecipitation assays and mass spectrometry were performed to identify protein interactors of UCHL1. The impact of the UCHL1-Keratin 8 (KRT8) axis on TMZ resistance was evaluated using the cell counting kit-8 (CCK-8) assay and western blotting. Results: We found that UCHL1 induced resistance of glioblastoma cells to TMZ. Moreover, UCHL1 expression was significantly upregulated in patients with TMZ-resistant glioma and correlated with poor prognosis. As a deubiquitinase belonging to the UCH enzyme family, UCHL1 utilizes its deubiquitination activity to remove K27-linked polyubiquitin chains from KRT8, thereby preventing KRT8 degradation by the proteasome and maintaining its stability. In vitro assays further demonstrated that depletion of the UCHL1-KRT8 axis weakened chemoresistance by increasing TMZ-induced apoptosis. Conclusion: These findings reveal a novel signaling axis underlying TMZ resistance in glioblastoma and highlight the UCHL1-KRT8 axis as a promising therapeutic target.