Temozolomide sensitivity of malignant glioma cell lines – a systematic review assessing consistencies between in vitro studies

Abstract

Background Malignant glioma cell line models are integral to pre-clinical testing of novel potential therapies. Accurate prediction of likely efficacy in the clinic requires that these models are reliable and consistent. We assessed this by examining the reporting of experimental conditions and sensitivity to temozolomide in glioma cells lines. Methods We searched Medline and Embase (Jan 1994-Jan 2021) for studies evaluating the effect of temozolomide monotherapy on cell viability of at least one malignant glioma cell line. Key data items included type of cell lines, temozolomide exposure duration in hours (hr), and cell viability measure (IC50). Results We included 212 studies from 2789 non-duplicate records that reported 248 distinct cell lines. The commonest cell line was U87 (60.4%). Only 10.4% studies used a patient-derived cell line. The proportion of studies not reporting each experimental condition ranged from 8.0–27.4%, including base medium (8.0%), serum supplementation (9.9%) and number of replicates (27.4%). In studies reporting IC50, the median value for U87 at 24 h, 48 h and 72 h was 123.9 μM (IQR 75.3–277.7 μM), 223.1 μM (IQR 92.0–590.1 μM) and 230.0 μM (IQR 34.1–650.0 μM), respectively. The median IC50 at 72 h for patient-derived cell lines was 220 μM (IQR 81.1–800.0 μM). Conclusion Temozolomide sensitivity reported in comparable studies was not consistent between or within malignant glioma cell lines. Drug discovery science performed on these models cannot reliably inform clinical translation. A consensus model of reporting can maximise reproducibility and consistency among in vitro studies.

Meta-analysis on reporting practices as a source of heterogeneity in in vitro cancer research

“…A recent study has also identified suboptimal reporting of basic experimental parameters and varying cell viability reducing effects of TMZ in in vitro glioma cell line experiments with TMZ single treatment. 14 …”

“…However, the reporting of experimental parameters in this literature—including such fundamental issues as the concentration of the drug and the treatment duration—is limited. A recent study has also identified suboptimal reporting of basic experimental parameters and varying cell viability reducing effects of TMZ in in vitro glioma cell line experiments with TMZ single treatment 14…”

“…We also required that cell viability was measured by colorimetric assay or by cell counting, and that the authors used Dulbecco’s Modified Eagle Medium (DMEM) as the ATCC recommends using a modified Eagle medium for U-87 MG cell cultures 16 and as a recent review identified DMEM as the most frequently used medium for this type of experiment. 14 This culture medium restriction was introduced to guarantee sufficient comparability of experiments across studies and to prevent interference of different culture media in the analysis of the impact of culture medium ingredients (eg, glucose concentration and antibiotics) on the overall effect and its reproducibility. We only included original peer-reviewed research articles in the English language, with no restrictions made on the publication year.…”

“…We included studies describing controlled in vitro cell culture experiments that compared the effect of a single TMZ treatment on the viability of U-87 MG cells with that in untreated controls. We also required that cell viability was measured by colorimetric assay or by cell counting, and that the authors used Dulbecco’s Modified Eagle Medium (DMEM) as the ATCC recommends using a modified Eagle medium for U-87 MG cell cultures16 and as a recent review identified DMEM as the most frequently used medium for this type of experiment 14. This culture medium restriction was introduced to guarantee sufficient comparability of experiments across studies and to prevent interference of different culture media in the analysis of the impact of culture medium ingredients (eg, glucose concentration and antibiotics) on the overall effect and its reproducibility.…”

“…A previous systematic review of the in vivo literature describing the efficacy of TMZ showed limited reporting of key study design features and low prevalence of reporting of measures to reduce risks of bias 12. In vitro glioblastoma research commonly uses the commercially available cell line Uppsala-87 Malignant Glioma (U-87 MG),13 14 originally derived in 1966 from a female patient at Uppsala University 15. However, the currently available U-87 MG line distributed by the American Type Culture Collection (ATCC, Manassas, Virginia, USA)16 has been found to be different from the original version 17.…”