PI3K and inhibitors of Akt that have already demonstrated cl

PI3K and inhibitors of Akt that have already demonstrated clinical efficacy for different tumors. Since FKBP5 negatively regulates Akt activity, we would expect that the addition of inhibitors targeting the Akt SB 216763 supplier pathway might reverse resistance to gemcitabine. To test this hypothesis, we performed a series of in vitro experiments using three pancreatic tumor cell lines and two breast cancer cell lines. We selected three different Akt pathway inhibitors, including an upstream inhibitor of PI3K, LY294002, a specific Akt inhibitor, triciribine that inhibits phosphorylation of all three isoforms of Akt, and an mTOR inhibitor, rapamycin. We then evaluated the cytotoxicity effect of gemcitabine in combination with LY294002, TCN, and rapamycin, respectively. Table 1 summarizes IC50 values of each treatment for these five cell lines. Our data confirmed, once again, that knockdown of FKBP5 desensitized cells to gemcitabine treatment in all of the cell lines tested. LY294002, TCN and 92169-45-4 rapamycin had very modest effects when used alone in either FKBP5 knockdown cells or control cells, especially at the concentrations that we used for combination treatments. TCN sensitized both control and FKBP5 knockdown cells to gemcitabine. However, the TCN sensitization effect was greater in FKBP5 knockdown cells than in wtFKBP5 cells. The sensitization effects of LY294002 and rapamycin were much less than that of TCN. We had previously found that level of FKBP5 also affects response to other chemotherapeutic agents, including etoposide and taxanes. Therefore, we tested whether TCN could also sensitize those agents in the four cell lines studied. In all four cell lines, FKBP5 knockdown made the cells more resistant to etoposide treatment alone, which is consistent with previous findings. We found that TCN could significantly sensitize etoposide in BXPC3, ASPC1, HS578T and MCF7 cells when compared IC50 values for etoposide treatment alone vs. different combination treatments. The sensitization effect was more prominent in cells with FKBP5 knockdown. LY294002 could also sensitize etoposide in BXPC3 and MCF7 cells with both control and siFKBP5 transfection, while rapamycin had a much less significant effect in control or FKBP5 knock down cells. Addition of TCN could also sensitize pac