Knockdown of Smad2 expression down-regulates PTPRK expression in EBV-negative HL cells. (A) Semiquantitative RT-PCR for Smad2 and PTPRK mRNA (left panel) and immunoblotting for Smad2 and PTPRK (right panel) in KM-H2 cells show that knockdown of Smad2 expression decreases PTPRK expression. The black dividing lines signify where images from different parts of the same gel have been moved together to bring samples next to each other for direct comparison. (B) Semiquantitative RT-PCR analysis of 2 other EBV-negative HL cell lines (HDLM-2 and L428) shows that PTPRK transcription is also reduced following the knockdown of Smad2 expression in these cells. In all cell lines, transfection with irrelevant siRNA oligonucleotides had no effect on Smad2 or PTPRK expression (data not shown).