a, Whole-brain GFP fluorescence image overlaid on a brightfield image representing characteristic tumours at time of death. b, Representative bioluminescence intensity images taken at 1-month intervals starting at 2 months of age, reflective of median survival trend. Scale bar for bioluminescence intensity quantifies photon counts over the 5 min of IVIS recording. Experiments were independently repeated three times with similar results for each variant. c, Longitudinal T2 MRI of variant tumours. Readings were taken at 1-week intervals from 4 weeks of age. All images are spatially matched along the rostral–caudal axis. Red dotted outline at P42 denotes the tumour boundary. Yellow scale bar, 2.5 mm. n = 4 mice for each variant. These experiments were not independently repeated. d, BrdU (red) antibody staining on 30-day-old mouse brains. White scale bar, 40 µm. n = 4 mice for each variant. n = 18 (R88Q), 19 (C420R) and 16 (H1047R) technical repeats. e, Associated quantification for relative tumour area from MRI and BrdU incorporation analysis. Box plots are as in Fig. 3b. *P < 0.05, ***P < 0.001, one-way ANOVA. f, Left, immunofluorescence analysis of BrdU (red) incorporation on PDX tumour sections. Human tissue was identified by staining for human HLA (green). Blue scale bar, 100 μm. Right, quantification of BrdU incorporation in a 2,000 μm2 area. n = 4 mice; n = 5 technical repeats. Box plots are as in Fig. 3b. ***P < 0.001, one-way ANOVA. g, Schematic illustrating experimental approach and timeline. h, Representative image of control GFP IUE. Proliferative index was calculated by dividing the number of BrdU+ cells on the electroporated side (marked by GFP) by the number of BrdU+ cells on the non-electroporated, contralateral side. Purple scale bar, 100 μm. i, Quantification of proliferative index for activating variants C420R and H1047R along with control (GFP), demonstrating no significant difference in proliferation. n = 3 mice; n = 5 technical repeats. Box plots are as in Fig. 3b. P values were not significant (P > 0.05, one-way ANOVA).