Examining the extent of senescence induced in normal human astrocytes following physiologically relevant doses of temozolomide
Glioblastoma is the most lethal form of astrocytic brain cancer. The aggressiveness of this disease is partly due to survival mechanisms adopted by tumor cells. Senescence is one such mechanism by which cells evade apoptosis. Senescent cells are no longer capable of proliferating but are still metabolically active. Understanding the cellular and molecular mechanisms by which tumor cells survive and recover via senescence-related processes may ultimately lead to the identification of more efficacious therapies to treat GBM. Recently, investigators argued that the interactions between astrocytes and tumor cells could promote disease progression; however, how therapy-induced senescence (TIS) influences these interactions is unknown. This study focused on understanding the response of human astrocytes (NHA) to temozolomide, a standard-of-care GBM treatment. We studied the extent of TMZ-induced senescence through a series of phenotypic assays performed subsequent to treatment administration in NHA cells in order to characterize the response of these cells. Minimum levels of cell death, even at supraphysiological doses of TMZ, indicated an alternative cell response. EdU staining demonstrated loss of proliferation with treatment, suggesting a growth-arrest related response. As such, we conducted X-Gal, which suggested TIS due to prominent senescence-associated β-galactosidase activity. Enhanced expression of p21, a senescence-associated cyclin-dependent kinase inhibitor, further supported TIS induction. Findings from this project ultimately contribute to our understanding of potential TIS-driven interactions between astrocytes and tumor cells, and future studies may identify druggable targets based on these interactions.