H2O2-clearance Kinetics of Crude Catalase Preparations from Prostate Cancer Cell Lines Treated with Physiological and Synthetic Small Organic Ligands of PPAR-γ

Aim: To determine the differences in H2O2-clearance of two prostate cancer cell lines PC-3 and LNCaP treated with peroxisome proliferator-activated receptor gamma (PPAR-γ) ligands 15-deoxy-Δ 12, 14 – prostaglandin J2 (PGJ2) and nafenopin (Naf)

Study Design: Catalase activity in cytosolic protein fractions was determined and the kinetic parameters Michaelis constant Km, maximum velocity Vmax, and Vmax/Km were used to determine H2O2-clearance differences and the presence of isozymes. Western blot of microsomal and nuclear protein fractions were used to determine the induction of PPAR-γ by ligand treatment and cytochrome P450 (CYP450) enzymes.

Place of Study: Department of Experimental Pathology, University of Vienna, Medical School Vienna; part of an ongoing study which started in 2000.

Methodology: One million cells of cultured PC-3 and LNCaP cell lines were treated with PGJ2 or Naf for 48 hours. Enzyme kinetics and Western blots were used to confirm differences in H2O2-clearance.

Results: PGJ2 and Naf induced PPAR-γ greater in PC-3 than in LNCaP. Vmax of PC-3 catalase was increased by PGJ2 (1.37 fold increase) but not by Naf (0.09 fold decrease) treatment while Naf (1.29 fold increase) but not PGJ2 (0.26 fold decrease) increased the Vmax of catalase in LNCaP. The changes in Km by the two chemical substances were statistically not significant (0.2 < p < 0.6) for both PC-3 (mean Km = 0.59±0.05 mM) and LNCaP (mean Km = 1.2±0.036 mM) cultures. Changes in Vmax led to equal magnitude of change in Vmax/Kmbut which was again not statistically significant (p = 0.6) between PC-3 and LNCaP cultures (control and treatment cultures). Lower Km always led to a lower Vmax and the vice versa but Vmax and Vmax/Km values were always higher for LNCaP than their corresponding catalase from PC-3 cultures.

Conclusion: The marked catalase activity of PC-3 and LNCaP, the high expression of drug metabolizing CYP450 enzymes and the different PPAR-γ induction kinetics in prostate cancer cells observed in this study can be explored for the modulation of redox status of prostate cancer cells with PPAR-γ ligands.