['To determine whether deguelin can regulate the expression of nuclear factor kappa B (NF-kappaB) binding protein (IkappaBalpha) in U937 human leukemia cells and Raji human B lymphoma cells.', 'The localization of IkappaBalpha protein was investigated by using an immunofluorescence method. The expression of IkappaBalpha and NF-kappaB /p65 proteins in Raji and U937 cells were investigated by using Western blotting. Apoptosis was detected through annexin V/PI double-labeled cytometry.', 'IkappaBalpha localized in the cytoplasm in untreated and deguelin-treated cells. After treatment with tumor necrosis factor alpha (TNF-alpha) or deguelin plus TNF-alpha for 15 min, there was a substantial reduction in the amount of IkappaBalpha protein. The expression of IkappaBalpha was downregulated by deguelin in Raji and U937 cells. Deguelin induced apoptosis in U937 cells.'] Does deguelin inhibit expression of IkappaBalpha protein in Raji and U937 cells?