PTX and MG132 reduce the expression of Bcl-2 and Bcl-XL antiapoptotic proteins in U937 cells. U937 human leukemia cells were incubated alone or were treated with 8 mM PTX, 1 μM MG132, or PTX + MG132. After 24 hours the Bcl-2 (A) and Bcl-XL (B)antiapoptotic proteins were determined by flow cytometry. For each sample, at least 20,000 events were acquired. The results represent mean ± standard deviation of the Mean Fluorescence Intensity (MFI) of Bcl-2 or of Bcl-XL of three independent experiments carried out in triplicate. *p < 0.01 vs the untreated control group.