Overexpression of the NIK mRNA and protein in PBMCs from ATL patients. (A) Total RNA was extracted from PBMCs from healthy donors and ATL patients and then subjected to quantitative RT-PCR. The NIK mRNA levels were normalized to 18S RNA. The relative nik mRNA levels shown represent the fold increases in mRNA abundance relative to that of healthy donor 1 (arbitrarily set at 1). These data are expressed as the mean plus or minus SD of 3 independent experiments. (B) PBMCs were cultured in the presence of actinomycin D (5 μg/mL) for the times indicated, and then total RNA was isolated and subjected to quantitative RT-PCR. The relative amounts of NIK mRNA shown represent the percentages in mRNA abundance, relative to that of PBMCs before the addition of actinomycin D (arbitrarily set at 100%). (C) PBMCs from a healthy donor and an ATL patient were treated with (+) or without (−) MG132 (20 μM) for 3 hours, lysed with RIPA buffer, and subjected to immunoblotting with anti-NIK or anti-α-tubulin antibodies.