Fig. 8. Egr/JNK-mediated necrosis restricts oncogenic growth of scrib mutant cells.

a–c′ Late 3rd instar larval eye disks with GFP-positive scrib mutant (scrib^−/−, a), scrib^−/−-p35 (b) or scrib^−/−-p35-bsk^DN (c) clones in an otherwise wild-type background. These disks are labeled with Propidium Iodide (PI, red in a–c and gray in a′–c′). Compared with scrib mutant clones (a, a′), PI-positive necrosis is induced in scrib^−/−-p35 clones (arrows, b, b′). This necrosis is suppressed by inhibition of JNK via expression of bsk^DN (c, c′). d, e Adult eye images. scrib mutant clones only cause a mild rough-eye phenotype (d). In contrast, necrotic patches (arrow, e) are observed in over 90% of scrib^−/−-p35 mosaic eyes (n = 44). f scrib^−/−-p35-bsk^DN mosaic animals are pupal lethal. g Quantification of the clone/disk size ratio in late 3rd instar larval eye disks with various genetic backgrounds as indicated. The ratio is a comparison of the total clone size in each eye disk to the full disk size. One-way ANOVA with Bonferroni multiple comparison test was used to compute p-values. Asterisks indicate statistically significant changes (****P < 0.0001). Compared with wild-type clones which occupy an average of 40% of the whole eye disk, scrib mutant (scrib^−/−) clones are much smaller with an average of 8% coverage on the disk. Expression of P35 in scrib^−/− clones (scrib^−/−-p35) moderately increases their sizes leading to an average disk coverage of 28%. Further expression of bsk^DN in these clones results in their massive overgrowth and increases the clone/disk ratio to an average of 78%