P13.09 Inconsistent effect of temozolomide exposure on cell viability in glioblastoma cell line models - a systematic review
Abstract BACKGROUND The alkylating agent temozolomide is part of standard care for patients with glioblastoma. Potential novel therapeutic agents are often first evaluated against temozolomide in glioblastoma cell line models. Despite the importance of this step in compound development, there is no standard concentration or exposure duration of temozolomide in laboratory research, and consistency in the effect of temozolomide on glioblastoma cell lines has not been assessed. This systematic review aimed to summarise the concentration and exposure duration of temozolomide and its effect on cell viability in studies using glioblastoma cell lines. MATERIAL AND METHODS We searched Medline and Embase Jan 1994 - Feb 2021 for studies that used at least one glioblastoma cell line and reported a measure of cell viability associated with temozolomide exposure. Studies were excluded if they used modified cell lines or did not report a cell viability measure associated with temozolomide as monotherapy. One reviewer screened all records and two reviewers assessed potentially eligible studies for inclusion. The main data items included the cell lines used, the concentration and exposure duration to temozolomide, and cell viability measures. We summarised findings using descriptive statistics. RESULTS Of 1,533 potentially eligible studies we included 213 studies reporting 209 different cell lines. The most common cell lines were U87, U251 and T98G, used in 61%, 41%, and 27% of studies, respectively. Twenty-five (12%) studies used patient-derived cell lines. The concentration of temozolomide used ranged from 0 to 8000μM. The temozolomide exposure duration ranged from <24 hours to >96 hours, with 29% studies using 72 hours. The most common cell viability measure was half maximal inhibitory concentration (IC50), which was reported in 183 (86%) studies. The median IC50 in 32 studies using the U87 cell line was 180μM (interquartile range [IQR]: 52–254μM) at 48-hour temozolomide exposure and 202μM (IQR 52–518μM) at 72-hour exposure. The median IC50 in 31 studies using U251 cell line was 84μM (IQR: 34–324μM) at 48-hour exposure and 102μM (IQR: 35–358μM) at 72-hour exposure. CONCLUSION Experimental setup of temozolomide and its effect on cell viability vary widely between studies using similar glioblastoma cell lines. This inconsistency of response to temozolomide questions reproducibility and the translational value of study findings.