KPNA3 drives temozolomide resistance in glioblastoma by upregulating MGMT and activating STAT3 to sustain glioma stem cells

Glioblastoma (GBM) invariably develops resistance to temozolomide (TMZ), the frontline chemotherapeutic agent, leading to treatment failure. The molecular mechanisms underlying this resistance remain incompletely understood. Here, we identify karyopherin subunit alpha 3 (KPNA3) as a novel and critical driver of TMZ resistance. Through integrated bioinformatics analysis of temozolomide-resistant glioma cells (SF126R) and patient databases, we found KPNA3 expression is elevated in TMZ-resistant contexts and correlates with poor prognosis in TMZ-treated patients. Functional studies demonstrated that KPNA3 knockdown in resistant cells impaired malignant behaviors, re-sensitized cells to TMZ-induced apoptosis, and suppressed glioma stem cell (GSC) properties, including sphere formation and expression of stemness factors (OCT4, ALDH1A1). Mechanistically, KPNA3 promotes resistance via a dual pathway: it upregulates the expression of the DNA repair enzyme MGMT and activates the STAT3 signaling pathway. KPNA3 knockdown reduced both MGMT levels and STAT3 phosphorylation (Tyr705). Furthermore, pharmacological inhibition of STAT3 mirrored the effect of KPNA3 knockdown by potently inhibiting GSC generation. Clinically, KPNA3 and p-STAT3 protein levels were positively correlated in high-grade glioma tissues. Collectively, our findings unveil KPNA3 as a central regulator that concurrently enhances DNA repair and sustains the GSC population to foster TMZ resistance, nominating it as a promising therapeutic target for overcoming chemoresistance in GBM.