Figure 5.

Genotoxic drugs activate TAK1 by uric acid production. (a) HeLa cells were incubated in the absence or presence of gemcitabine (2 μM) and allopurinol (AP) (200 μg/ml). After incubation for 24 hr, cell lysates were prepared and analyzed for TAK1, ERK, JNK, p38, and p65 phosphorylation and their total proteins by Western blot. (b) XOR overexpression enhances genotoxic drug-induced TAK1 activation. MCF-7 cells were transfected with pcDNA3.1 or pCMV/XOR. After incubation for 24 hr, the cells were left untreated or treated with gemcitabine (2 μM) or 5-FU (10 μM) for another 24 hr. The cells were harvested and analyzed for the levels of TAK1, JNK, p38, and p65 phosphorylation and their total proteins by Western blot. Relative phosphorylation levels were analyzed by quantifying the density of phosphorylated protein bands normalized by the density of their corresponding total protein bands with NIH Image-J software and presented as bar graphs. Data are the mean ± SD of three experiments. **p < .01, compared to the untreated control. ^#p < .05, ^##p < .01, compared to the corresponding gemcitabine or pcDNA3.1-transfected controls.