Figure 5.

Par-4 expression prevents the long-term survival of cells following inhibition of the PI3K-Akt pathway. A, Western blot showing Par-4 expression in BT-474 cells expressing a non-targeting sgRNA or one of two sgRNAs targeting Par-4. B, Growth curves for control and Par-4 knockout BT-474 cells. C, Fluorescent micrographs from a cellular competition assay. Control cells labeled with H2B-mStrawberry were mixed in a 1:1 ratio with Par-4 knockout cells labeled with H2B-eGFP. Cells were left untreated or treated with Lapatinib or MK-2206 for 31 days, at which point the drug was removed and surviving cells were allowed to grow out for 2 weeks. D, Quantification of the percentage of Par-4 knockout (GFP+) cells in untreated cells at day 1 and after 5 population doublings (d11). E, Quantification of the percentage of Par-4 knockout (GFP+) cells in the residual population that survives following treatment with Lapatinib or MK-2206 (d31), and after removal of drug to allow the outgrowth of residual cells (d14). F, Model for Par-4 regulation following therapies targeting the PI3K-Akt-mTOR pathway. Data are presented as the mean of three biological replicates plus SD. *, p<0.05; **, p<0.01; ***, p<0.001.