PTPRK inhibits the cell migration and invasion ability of NKTCL cells. (A) Images show cell-cell interactions of NKTCL cells after resuspension in fresh medium for 6 hours. (i) Clumps of 5 to 10 cells were formed by GFP-sorted PTPRK-transduced NKYS cells in culture (diffused green fluorescence over the entire cell). Mock vector-transduced NKYS cells were used as the control. (ii) Clumps of 5 to 10 cells were only formed by RFP-sorted control shRNA-transduced SNK6 cells in culture (diffused red fluorescence over the entire cell), but not cells transduced with PTPRK-specific shRNA#1 and shRNA#2. Original magnification ×400. (B) Bar charts show the migration and invasion rate of NKTCL cells according to the number of sorted cells that passed through transwell inserts containing 8-µm pore polyethylene terephthalate membranes and the number of cells that passed through inserts covered with diluted Matrigel basement membrane, respectively. The cells that migrated to the lower chambers were counted in 5 randomly selected microscopic fields (200×). Each assay was repeated 3 times. The bars indicate the mean ± SE. Re-expression of PTPRK significantly inhibited the cell migratory and invasion abilities of non–PTPRK-expressing NKYS cells (i), whereas knockdown of PTPRK enhanced SNK6 cell migration and invasion (ii).