Introduction of DUSP5 expression in ATL cells inhibits cell growth and ERK phosphorylation. (A) Experimental protocol for the establishment of HTLV-1–infected cell lines exogenously expressing DUSP5 and assays. (B) The ratio of GFP-positive cells was monitored at the indicated days, and changes in the GFP population were calculated as follows: 100 × (GFP population at day X)/(GFP population at day 0) based on data from 3 independent experiments. Day 0 was defined as 3 days after lentivirus infection. Gray lines indicate cells infected with empty vector. Blue lines indicate cells infected with lentiviral vectors expressing DUSP5. (C) The total number of GFP-positive cells was calculated from the data of panel B. (D) Immunoblots showing the effect of phosphorylation of ERK1/2 in MT-1 and TL-Om1 cells induced by exogenously expressed DUSP5 under normal growth conditions. Data are expressed as the mean of 3 independent individuals with SD. Differences were tested using the paired t test. (E) Immunoblots showing changes in the phosphorylation pattern of ERK1/2. TL-Om1 cells exogenously expressing DUSP5 were isolated and treated with 10% FBS for the indicated times after serum starvation for 15 hours. FBS, fetal bovine serum; SD, standard deviation.