Fig. 4.

The toxic interaction between PDE5 inhibitors and chemotherapy is blocked by overexpression of BCL-XL or c-FLIP-s. Bladder cancer cells (HT-1376; J82; T24) were infected with empty vector adenovirus (CMV) or three other viruses to express dominant negative caspase 9 (dn casp 9); BCL-XL; c-FLIP-s. (A–C) Thirty-six hours after infection cells were treated with vehicle, sildenafil (SIL, 2 μM), mitomycin C (MITO, 100 nM), DOX (200 nM), Gemzar (50 nM) as indicated. Cells were isolated after 24 hours, and viability was determined by trypan blue exclusion (n = 3, ± S.E.M.). *P < 0.05 less than corresponding value in CMV control. (D) Prostate cancer cells (DU145) were infected with CMV or three other viruses to express dn casp 9, BCL-XL, c-FLIP-s. Thirty-six hours after infection cells were treated with vehicle, SIL (2 μM), DOX (200 nM), as indicated. PC-3 prostate cancer cells that lack phosphatase and tensin homolog and have constitutive AKT activity were used as an internal control. Cells were isolated after 24 hours, and viability was determined by trypan blue exclusion (n = 3, ± S.E.M.). *P < 0.05 less than corresponding value in CMV control. (E and F) Pancreatic cancer cells (PANC-1, Mia Paca2) were infected with CMV or three other viruses to express dn casp 9: BCL-XL, c-FLIP-s treated with vehicle, SIL (2 μM), and/or gemcitabine (Gemzar, 50 nM) and/or paclitaxel (TAX, 10 nM) as indicated. Cells were isolated after 24 hours, and viability was determined by trypan blue exclusion (n = 3, ± S.E.M.). (G–I) Bladder cancer cells (HT-1376; J82; T24) were transfected with scrambled siRNA (siSCR) or siRNA molecules to knock down expression of CD95 or Fas-associated death domain protein (FADD) (siCD95, siFADD). Thirty-six hours after transfection cells were treated with vehicle, SIL (2 μM), MITO (100 nM), DOX (200 nM), Gemzar (50 nM) as indicated. Cells were isolated after 24 hours, and viability was determined by trypan blue exclusion (n = 3, ± S.E.M.). *P < 0.05 less than corresponding value in siSCR control.