03); **represents significant difference between

group ’1%FBS + 10 ng/ml TGF-β1′ and group ’1%FBS’ (P = 0.044). Figure 6 The effects of TGF-β1 on expression levels of PKCα and p38 MAPK. BxPC3 cells were treated with 0.1, 1 and 10 ng/ml TGF-β1 for 10 min, 30 min and 24 h. Total cellular protein was extracted and subjected to western blotting analysis to detect expression of PKCα, phosphorylated-p38/total p38 MAPK and phosphorylated-ERK1/2/total ERK1/2. Bx represents BxPC3 cells and Bx/T represents the stably transfected BxPC3 cells with TGF-β1 plasmid. To determine whether the induced PKCα activity is responsible for the TGF-β1-induced decrease in the sensitivity of BxPC3 cells to cisplatin, we treated the cells with a selective PKCα inhibitor, Gö6976, and assessed TGF-β1-induced drug resistance. We found that inhibition of PKCα

activity could partially reverse TGF-β1-induced drug resistance of BxPC3 cells to cisplatin AZD5582 (Figure 7). Figure 7 MTT assay. (A) BxPC3 cells were grown in DMEM containing 5 μg/ml of TGF-β1 and then treated with or without Gö6976, an inhibitor of PKCα at the indicated concentrations. After this pretreatment, the cells were further treated with cisplatin for an additional 48 h, and the cell viability was determined via MTT assay. (B) IC50 values. * represents a significant difference in IC50 values between groups for TGF-β1 (5 ng/ml) and all other groups. high throughput screening Blockade of PKCα and TβRII reversed BCKDHB the resistant status of BxPC3 cells We designed and constructed a TGF-β type II receptor (TβRII) siRNA expression vector to knockdown TβRII expression. We stably transfected the TβRII siRNA vector into BxPC3 cells and isolated three stable clones.

Western blotting analysis showed that TβRII expression was significantly knocked down in clone 2 relative to the other two clones (Figure 8A). We chose clone 2 for the following experiments. The IC50 of clone 2 to gemcitabine was 812 μg/ml, much lower than that for the vector-only-transfected BxPC3 and the parental cells (Figure 8B), indicating that knockdown of TβRII increases the mortality of cancer cells and increases sensitivity to gemcitabine. Figure 8 Role of TβRII siRNA in BxPC3 cells. (A) Western blotting analysis of TβRII (type II receptor or TGF-β1) protein levels. BxPC3 cells were grown and transfected with TβRII siRNA. After selection with G418, three clones were isolated and the cells from these clones underwent protein isolation. They were subjected to Western blotting analysis with anti-TβRII antibody. Lane 1, total pool of BxPC3 cells; lane 2, mock clone (transfected with empty plasmid, psilenser 2.1 U6); lane 3, knockdown (KD) clone 1; lane 4, KD clone 2; and lane 5, KD clone 3. (B) MTT assay. The transfected BxPC3 cells were grown and treated with gemcitabine at the indicated doses for 2 days. The cell viability was detected by using the MTT assay.