Suppression of PKK expression inhibits tumor growth of xenografted OCI-Ly7 cells in NOD/SCID mice. OCI-Ly7 cells expressing shControl or shPKK-1 were injected subcutaneously into NOD/SCID mice (n = 4, each). The tumor volumes were measured at the indicated times. The average tumor volumes from 4 injected mice were shown. The tumors from cells expressing shControl are significantly larger than those from the cells expressing shPKK-1 (P < .01 at day 27 after implantation).