COX-2, PGE2, and IL-8 decreased PDCD4 protein levels. (a) The expression of COX-2 and PDCD4 proteins in three independent clones of MCF-7/COX-2 cells and MCF-7 parental cells was determined by immunoblotting equal amounts of total cell lysates with COX-2 monoclonal and PDCD4 polyclonal antibodies, respectively. COX-2 and PDCD4 levels were analyzed by densitometry, normalized to β-actin level, and expressed as percentages of MCF-7 parental cells. (b) MCF-7 cells were untreated or treated with 10 μM PGE2 or 100 ng/ml IL-8 for 24 h. Protein lysates were immunoblotted with PDCD4 and β-actin antibodies. PDCD4 levels were analyzed by densitometry, normalized to the corresponding β-actin levels, and the ratios were expressed as percentage of untreated cells