Targeting the miR-19b/PPP2R5E axis enhances temozolomide response in glioblastoma via ROS-induced DNA damage

Glioblastoma is the most aggressive primary brain tumor. Although temozolomide induces DNA damage, its efficacy is limited by intrinsic resistance mechanisms, leading to tumor relapse. In this study we aimed to identify microRNA-mediated resistance mechanisms.

MicroRNA screens were performed to identify temozolomide resistance mechanisms. Temozolomide response was evaluated using clonogenic and spheroid assays in glioblastoma cell lines and patient-derived primary cells. DNA damage response was assessed by γH2AX foci formation. Cell cycle distribution, senescence and ferroptosis were assessed following miR-19b attenuation. An orthotopic xenograft and a syngeneic mouse model were used to confirm findings.

Our screen and subsequent phosphoprotein analysis identified miR-19b and its target PPP2R5E, a subunit of the phosphatase PP2A, as modulators of temozolomide response. Attenuation of miR-19b upregulated PPP2R5E, inducing genotoxic stress, thereby enhancing temozolomide response. Mechanistically, DNA damage correlated with elevated nuclear ROS, promoting senescence and ferroptosis. Consistently, pharmacological activation of PP2A with FTY720 phenocopied the effects of miR-19b suppression. Conversely, knockdown of PPP2R5E reversed temozolomide sensitisation in vitro, in vivo, and ex vivo models, confirming the critical role of the miR-19b/PPP2R5E axis in modulating drug response.

Therapeutic targeting of the PPP2R5E/PP2A complexes holds promise for enhanced temozolomide efficacy in glioblastoma.