TP53 and neoplasm: Intratumor injection of PEPD siRNA once every 2–3 days strongly downregulated PEPD in both types of tumors, strongly inhibited HCT116-p53+/+ tumors, which was accompanied by p53 activation (Bcl-2 downregulation, upregulation of p21 and Bax, and caspase 3 activation) in the tumors, but had no effect on HCT116-p53−/− tumor growth or the p53 targets in these tumors (Fig. 2g–l).