Cell proliferation assay and Western blotting using prostate cancer DU145 cells. (A) Cells were pretreated with 0, 50, 100 and 200 μM astaxanthin for 48 h. Proliferation was measured by MTT assay. Data are presented as the average of three experiments (±SD), * p < 0.05, ** p < 0.01, and *** p < 0.001. (B) DU145 cells were pretreated with 200 μM astaxanthin for 24 h. Western blotting results show that 200 μM astaxanthin reduces the level of STAT3. (C) Relative protein expression analysis. * p < 0.05, ** p < 0.01, and *** p < 0.001. (D) Relative mRNA expression analysis. ** p < 0.01, and *** p < 0.001.