The mechanism underlying the anti-cancer activity of curcumin has been extensively investigated, and several signaling pathways including NF B, AP 1, mitogen Linifanib VEGFR inhibitor activated protein kinases, and cell cycle machinery have been recommended because the targets of curcumin. Recently it’s been reported that curcumin inhibits Akt/mTOR signaling in several tumefaction cells including prostate cancer cells, nevertheless, the molecular mechanism where curcumin inhibits Akt/mTOR signaling remains unclear. In today’s study we examined the molecular mechanism through which curcumin inhibits Akt/ mTOR signaling in the separate and PTEN null PC 3 prostate cancer cells. Our show that curcumin concentration and time dependently inhibits Akt/mTOR signaling, and this inhibitory effect is primarily mediated by curcumin activated PP2A and/or unspecified calyculin A sensitive protein phosphatase. In the same time, curcumin also activates MAPKs and AMPK, but these kinases are less involved in curcumin mediated inhibition of Akt/mTOR signaling. Reagents and product Inguinal canal, plasmids, and cell culture Curcumin, PI3K inhibitor Ly294002, MEK1 inhibitor PD98059, JNK inhibitor II and p38 inhibitor SB238004 were obtained from Sigma. L Phosphatidylinositol trisphosphate, Compound D and Tautomycetin were obtained from EMD Bio-sciences. Ser/Thr Phosphatase Assay Kit, active PDK1 protein, akt1/pkb protein and okadaic acid sodium salt were purchased from Upstate. MTS assay kit was obtained from Promega. L and thymidine leucine were received from Perkin Elmer. Calyculin A, siRNA against tuberin/TSC2, control scrambled siRNA, cell lysis buffer and antibodies against p PI3K p85 /p55, p PDK1, p Akt, p Akt, Akt, p FoxO1, p GSK3B, p mTOR, p mTOR, mTOR, p p70 S6K, p S6 ribosomal protein, p 4E BP1, p eIF4G, Tuberin/TSC2, p Tuberin/TSC2, p AMPK, p ACC, methylated and non methylated PP2A catalytic subunit natural product library were obtained from Cell Signaling Technology. Antibodies against B actin, HA label, PDK1, cyclin D1 and HRP conjugated secondary antibodies were purchased from Santa Cruz Biotechnology. recombinant protein G conjugated agarose and all cell culture materials were obtained from Invitrogen. All of those other chemicals were of the best level available. HA branded Akt and AMPK1 expressing plasmids were presents from Dr. Kun liang Guan, the constitutively activated Akt expressing plasmid was something special from Dr. Cory Abate Shen. The principal negative AMPK1 was constructed by mutation of Threonine 172 to Alanine using QuickChange site directed mutagenesis kit and the mutation was confirmed by sequencing. Human prostate cancer PC 3 cells were cultured in minimal crucial medium supplemented with one hundred thousand fetal bovine serum. TSC1 and wild-type MEFs were gifts from Dr. David J. Kwiatkowski and Dr. Shengkan Victor Jin and maintained in Dulbeccos minimum crucial medium supplemented with 10 percent fetal bovine serum and 3.