Fig. 3

Sorafenib induces macropinocytosis via mitochondrial dysfunction-induced activation of PI3K-RAC1-PAK1 signaling. A Gene set enrichment analysis of PI3K signaling related genes expressed by sorafenib-treated SK-Hep1 cells. B Levels of phosphorylated AKT, activation of RAC1, and phosphorylated PAK1 and AMPK, in SK-Hep1 and Huh7 treated with sorafenib. C The oxygen consumption rate (OCR) of SK-Hep1 at the indicated time points after sorafenib treatment. D Levels of phosphorylated AKT, PAK1, and AMPK in SK-Hep1 and Huh7 cells after treatment with oligomycin (Oligo) and antimycin A (AA). E Effect of a PI3K inhibitor (LY294002) on RAC1 activation in sorafenib-treated SK-Hep1 and Huh7 cells. F Levels of phosphorylated PAK1 in sorafenib-treated SK-Hep1 and Huh7 cells in the presence or absence of a PI3K inhibitor (LY294002), an AMPK inhibitor (compound c), or a RAC1 inhibitor (NSC23766). (G and H) Representative images of macropinosomes (red), and DQ-BSA fluorescence (green) in sorafenib-treated SK-Hep1 (G) and Huh7 (H) in the presence or absence of a PI3K inhibitor, an AMPK inhibitor, or a RAC1 inhibitor (upper panel). Quantification of macropinosomes and DQ-BSA fluorescence in cells (lower panel). Data are normalized against values measured in vehicle-treated cells (Con) and expressed as the mean ± SEM of at least three independent experiments. Scale bar, 20 µm. ***p < 0.001