PIK3CB and neoplasm: As systemic siRNA administration by intraperitoneal injection (i.p.)did not deplete PI3Kβ efficiently in tumors (not shown), we optimized administration by direct injection into the tumor center of PIK3CB siRNA1 (siPIK3CB1) (12.5, 50, 120 pmol/mm3 tumor) on days 1, 3 and 5, and effects were tested on day 7.