Temozolomide-induced senescent glioblastoma cells acquire sensitivity to TRAIL death receptor 5-mediated apoptosis.

Therapy-induced senescence plays a crucial role in cancer treatment, evolving the resistance of malignant cells to therapeutic interventions. Therefore, the discovery of safe and effective senolytics may serve to develop new promising therapeutic options. Here we have revealed the enhanced apoptotic potential of DR5 receptor agonist, receptor-selective TRAIL variant DR5-B in temozolomide-induced senescent glioblastoma cell lines U87MG and T98G and primary tumor samples from patients with diagnosed glioblastoma. Senescence features were most pronounced in p53-proficient, MGMT-deficient U87MG cells, as demonstrated by enlarged cell and nuclei size, increased β-galactosidase activity, p21 expression and lipofuscin autofluorescence. This was accompanied by a metabolic shift towards glycolysis measured by fluorescence lifetime imaging (FLIM) of NADH, and upregulation of DR5, DcR1, DcR2 and cFLIP. As a result, a strong sensitization of U87MG cells to DR5-B-mediated apoptosis was observed after TMZ pre-treatment. However, neither was observed in p53-mutated, MGMT-proficient T98G cells. Differential gene expression analysis in TMZ-treated U87MG cells showed the activation of proinflammatory and proapoptotic signaling and downregulation of genes related to DNA metabolism and cell cycle. Two of three primary patient-derived glioblastoma samples tested acquired similar senescence features and were sensitized to DR5-B-mediated apoptosis by TMZ pre-treatment. These findings suggest that TMZ-induced senescence enhances glioblastoma cell sensitivity to DR5 receptor agonists. However, when developing strategies for senolytic antitumor therapy, the heterogeneous response of tumor cells to senescence induction should be taken into account.