Partial PTPRK knockdown inhibits its tumor suppressive properties. (A) Knockdown of PTPRK expression significantly increased the proliferation rate of SNK6 cells. The graph shows the proliferation rates of PTPRK-specific shRNA#1- and shRNA#2-treated, and scrambled shRNA-treated SNK6 cells. The cell proliferation rate was determined as the degree of absorbance in the MTS assay. The average absorbance of triplicate wells was plotted against the number of days after seeding. (B) PTPRK expression knockdown significantly increased the anchorage-independent growth of SNK6 cells. (Top) The anchorage-independent colony formation assay was performed on PTPRK-specific shRNA#1- and shRNA#2-treated, and control shRNA-treated SNK6 cells in 0.4% methylcellulose. (Bottom) Bar chart showing the number of colonies formed in 5 randomly selected microscopic fields after 1 week. The experiments were performed in triplicate and repeated 3 times. The graph indicates the mean ± SD.