Figure 4. Temozolomide reduces cell viability of mSDH GIST models by induction of DNA double-strand breaks and impairing DNA repair.

A-C. Cell viability of mSDH GIST models determined by CellTiter-Glo viability assay after treatment by Imatinib (A), sunitinib (B) and temozolomide (C). Viability was measured after 3 days of treatment for imatinib and sunitinib and on 7 days of TMZ treatment. Data are presented as mean ± s.d.

D. Representative images of a neutral comet assay for mSDH GIST models treated with either DMSO or 500 μM TMZ for 72 h. Comet tail lengths were measured (n = 100+ cells per group) and plotted.

E. Representative immunofluorescence images of mSDH GIST models treated with DMSO or TMZ (500 μM) and stained for γ-H2AX⁺ nuclei. Quantification of γ-H2AX ⁺ cells in mSDH GIST models treated with DMSO or TMZ for 72 h. For each GIST model, γ-H2AX ⁺ nuclei were quantified and shown as % of total nuclei. Mann-Whitney t-test was performed for statistical analysis with **, P<0.01; ***, P<0.001, ****, P<0.0001.

F. Immunoblots of mSDH GIST models treated with DMSO or TMZ (500 μM) for 3 days and probed for indicated proteins.

G. Immunoblots of mSDH GIST models treated with DMSO or TMZ (500 μM) for 7 days and probed for indicated proteins. CC3 denotes cleaved caspase 3.