Western blot analysis. The pMTH1-U937 (pMTH1) and asCD11b-U937 (asCD11b) cells were cultured in the absence and in the presence of 5nM TPA for 24 h up to 72 h, respectively. Thereafter, the different populations were harvested, lyzed and 40 μg of total cellular protein was separated by 10% SDS-PAGE followed by Western blotting. a) For the expression of the metabolic enzymes MnSOD, p97/VCP and the 20 S proteasome (α-subunits), gels were subsequently stripped corresponding to a β-actin loading control. b) Analysis of the expression patterns of different extracellular matrix proteolytic enzymes were tested using antibodies against MMP-1, MMP-7 and MMP-9 for matrix restructuring. The unaltered expression level of β-actin serves as a loading control.