Resistance of Tax-expressing cells to TGF-β treatment.

(A) Expression of Tax mRNA in stable Mv1Lu transfectants. A clone Neo-10 (lane 1) is a control line obtained from Mv1Lu cells transfected with pH2Rneo, followed by G418 selection. Clones Tax-3 (lane 2), Tax-10 (lane 3), and Tax-15 (lane 4) were established from cells transfected with pH2R40M. As a positive control, total cellular RNA from HTLV-I–infected HUT-102 cells (lane 5) was used. (B) Tax-expressing (clones Tax-3 [●], Tax-10 [○], and Tax-15 [▵]) and unmodified (clone Neo-10 [■]) Mv1Lu cells were treated with the indicated concentrations of TGF-β for 48 hours. Proliferation of cells was examined by MTT assay. Results are expressed as percentages of the values obtained from control cultures that did not receive TGF-β. Each experiment was performed at least 3 times, and representative results are shown.