Knockdown of PDK1 partially sensitizes MAPK4-overexpressing tumor cells to PI3K blockade.

(A) Plate colony formation assays and (B) soft-agar assays on the engineered SUM159 and HCC1806 cells with 0.5 μg/ml Dox-induced overexpression of MAPK4 (iMAPK4) or control (iCtrl), also with stable knockdown of PDK1 (shPDK1-1 and shPDK1-2) or control (NT). The cells were also treated with PI3K inhibitor Alpelisib (1 μm or 2 μm) or DMSO control. Scale bar: 500 μm. Quantification data as means ± SD. P values by two-way ANOVA followed by Sidak’s multiple comparisons. **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001. ns, not significant. Data are representative of at least 3 independent experiments. The numerical values underlying the figures can be found in S1 Data. MAPK4, mitogen-activated protein kinase 4; PDK1, phosphoinositide-dependent kinase-1.