Programed cell death 4 (Pdcd4) is a newly discovered tumor suppressor gene，which was found to inhibit oncogenesis by suppressing transcription and translation related genes. Expression of Pdcd4 has been found loss or low in several types of human tumors. It is reported that 5’CpG island methylation is the predominant cause of Pdcd4 mRNA silencing in gliomas. MicroRNA-21 regulates Pdcd4 in post-transcription by binding Pdcd4, and the target site is at the Pdcd4 mRNA 3’-UTR region. The mean Pdcd4 protein levels in cells is correlated with the antitumor activity of some drugs, upregulation of Pdcd4 expression may increase cytotoxicity of certain antitumor drugs and downregulation of Pdcd4 expression may reduce cytotoxicity of certain antitumor drugs. Some antitumor drug may affect the expression of Pdcd4. Pdcd4 interferes with the acetylation of p53. Phosphorylation of Pdcd4 by Akt/PKB (protein kinase B) causes nuclear translocation of Pdcd4 and a decreased ability to function as an inhibitor of AP-1( activator protein-1)-mediated transcription. Phosphorylated Pdcd4 by protein kinase S6K1 can be degraded via the ubiquitin pathway by SCF^βTRCP ligase.