TSA effect on Pgp levels and activity in pancreatic cancer cells. A. MDR1 mRNA levels determined by real time RT-PCR. IMIM-PC-1, IMIM-PC-2 and RWP1 cell lines were treated or not with 1 μM TSA or 7.5 μM SAHA for 24 h. GAPDH mRNA was also determined as internal control. Results are shown as the mean ± SD of at least three independent experiments with three replicates in each experiment. B. Western blot analysis of Pgp expression in IMIM-PC-1, IMIM-PC-2 and RWP1 pancreatic carcinoma cell lines treated or not with 1 μM TSA for 24 h. As a positive control the Pgp expressing K-562/Adr cell line was included. β-Actin is included as internal control. C. Pgp activity in the pancreatic carcinoma cell lines IMIM-PC-1, IMIM-PC-2 and RWP1 treated or nontreated with 1 μM TSA for 24 h and in the presence or absence of 2.5 μM verapamil (Pgp inhibitor). Pgp activity was estimated as daunomycin accumulation determined by flow cytometry. Daunomycin accumulation was also determined in the L1210R cell line for positive control.