PF-3758309 suppressed the activities of PAK1 and PAK4. The six TKCC cell lines were incubated with PF-3758309 at the concentrations listed in Table 1 under hypoxia (5% O2) for 48 h. The protein levels of total and phospho-PAK1 and PAK4 were determined by Western blot, and representative images were presented (A). Relative protein amount was calculated as described in Materials and Methods, and the values for untreated cells were taken as 100% (B-E). The results were summarized from three independent experiments. *P < 0.05, **P < 0.01, compared to the values for non-PF-3758309-treated cells. pPAK1, phospho-PAK1; tPAK1, total PAK1; pPAK4, phospho-PAK4; tPAK4, total PAK4.