Figure 4. Increased p27Kip1 and decreased phosphorylated p27Kip1 at S10 and T198 by lowering H₂O₂ levels.

The expression of p27Kip1 and p27Kip1 phosphorylated at S10 (p27pS10) and T198 (p27pT198) was analyzed by western blot. (A–B) A375 melanoma cells treated with catalase (CAT) for 6 and 24 h. FBS starved cells were used as control of G1 arrest. (C–D) Catalase overexpression model (A375-CAT-E9 cells) vs. controls (A375-pcDNA3 and A375 control cells). (E–F) Non-tumor (PIG-1) vs. tumor (A375) cells. (A, C and E) Representative immunoblot images. (B, D and F) Relative densitometric values of () p27Kip1 levels, (□) p27pS10 and (■) p27pT198. Actin densitometric values were used to standardize for protein loading. Results are referred to control without treatment (in B and D) and to non-tumor (PIG-1) cells (in F). Data are expressed as mean ± SD. (B) *p<0.05 and **p<0.01 vs. untreated control. (D) **p<0.01 vs. A375 control. (F) **p<0.01 vs. non-tumor cells.