Mechanisms associated with temozolomide resistance in U87MG cell line: in silico and in vitro approaches

IDH-wildtype grade diffuse glioma is the most aggressive primary brain tumor in adults, with limited survival despite standard therapy with temozolomide (TMZ). Resistance to TMZ is driven by DNA repair pathways, tumor heterogeneity, and microenvironmental adaptations, indicating the need for novel therapeutic strategies. Using a systems biology approach, a compound-protein and protein–protein interaction networks was constructed with STRING 12.0 and STITCH 5.0 databases, identifying hub-bottleneck proteins associated with TMZ resistance. Topological and gene ontology analyses revealed 5 functional modules enriched in DNA repair and apoptosis, with PARP1, PCNA, TP53, MSH2, and HSPA1a emerging as key regulators. HSPA1a modulated survival by inhibiting TP53 and caspase signaling, while also blocking mismatch repair via MSH2 and MLH1 upregulation. In vitro studies using U87MG cells exhibited greater sensitivity to demethoxycurcumin (DMC) compared to TMZ. Importantly, DMC synergized with TMZ to reduce the concentration required for growth inhibition. Comet assays data confirmed TMZ-induced DNA damage and transient base excision repair (BER) impairment, while DMC enhanced both PCNA expression and caspase-mediated apoptosis. Co-treatment with DMC and TMZ sustained PARP1 downregulation, prolonged DNA damage, and amplified apoptosis. These findings indicated that DMC functions as an effective chemosensitizer, elevating TMZ efficacy. Combining DMC with DNA repair inhibitors may represent a promising therapeutic strategy to overcome resistance and improve IDH-wildtype grade diffuse glioma treatment outcomes.