CTSK and prostate carcinoma: Similar results were also observed in siRNA-mediated knockdown of cathepsin K. Cathepsin K siRNA decreased Raptor protein expression and phosphorylation of OTUB1 and Src in Caki-1 (renal carcinoma), A549 (lung carcinoma), and DU145 (prostate carcinoma) cells, significantly (Fig. 1B).