MK-2048 induces ER stress–related apoptosis in MK-2048-sensitive HTLV-1–infected cells. (A) CHOP mRNA expression levels in the indicated cells after 16-hour treatment with 25 μM MK-2048. The mRNA expression levels of treated cells relative to those of untreated cells are shown. The results are expressed as the mean ± SD of 3 independent experiments. The bar graph is shown as a dot plot. (B) The levels of protein expression in ER stress–related molecules at the indicated times after the addition of 25 μM MK-2048 in indicated cells are shown. (C) The levels of protein expression in ER stress–related molecules at the indicated times after the addition of 1 μg/mL tunicamycin in Jurkat cells are shown. (D) Representative immunostaining for CHOP (green) in KK1 cells after 24-hour treatment with 25 μM MK-2048. Bars represent 10 μm. (E) Cell viability, caspase-3/7 activity, and CHAC1 and CHOP mRNA expression levels in ED cells 24 hours after treatment with 50 μM MK-2048. The indicated values show the ratio of MK-2048–treated or –untreated cells. ED cells were pretreated for 1 hour with the indicated concentrations of GSK2606414 prior to the addition of 50 μM MK-2048. The indicated concentrations of GSK2606414 were added to the control cells. The results are expressed as the mean ± SD of 3 independent experiments. (F) Protein expression levels of ER stress–related molecules in ED cells at the indicated concentrations of GSK2606414 and 50 μM MK-2048.