title: Actinomycin D and gemcitabine synergistically sensitize androgen-independent prostate cancer cells to Apo2L/TRAIL-mediated apoptosis.
abstract: The cytotoxic efficacy and kinetics involved in sensitization of Apo2L/TRAIL-resistant, androgen-independent prostate cancer cells to Apo2L/TRAIL or tumor necrosis factor-alpha or Fas ligand-mediated apoptosis were tested using subclinical concentrations of actinomycin D, paclitaxel, cisplatinum, gemcitabine, and radiation in CL-1, LNCaP, DU-145, and PC3 prostate cancer cell lines. CL-1 cells expressed all four Apo2L/TRAIL receptors and were resistant to Apo2L/TRAIL-mediated apoptosis (1-5,000 ng/mL) and to the sensitizers when given alone. Pretreatment with actinomycin D followed by Apo2L/TRAIL or tumor necrosis factor-alpha or anti-Fas CH-11 monoclonal antibody, but not in the reverse order, induced apoptosis in all cell lines. Synergistic sensitization in CL-1 cells was shown also with gemcitabine but not with cisplatinum, VP-16, paclitaxel, or radiation. Incubating the Apo2L/TRAIL-resistant CL-1, LNCaP, DU-145, and PC3 cell lines with 100 ng/mL actinomycin D for 4 hours followed by Apo2L/TRAIL for 24 hours resulted in 45.4 +/- 10.3%, 58.8 +/- 3.6%, 53.4 +/- 1.4%, and 84.2 +/- 8.4% apoptosis, respectively. Prolonging the sensitization time to 24 hours followed by 20 hours of incubation with Apo2L/TRAIL further enhanced the killing activity against CL-1 cells to 89 +/- 1% (delta = 60%, synergistic ratio = 3.1). This killing has a biphasic pattern that was contributed to by apoptosis (83%) and necrosis (17%) at 10 hours (peak) and 40% and 60%, respectively, at 20 hours. These results suggest that prostate cancer cells' resistance to Apo2L/TRAIL-mediated apoptosis can be reversed and synergy is achieved by sensitization of tumor cells with subclinical concentrations of actinomycin D or gemcitabine and may be useful clinically for the treatment of metastatic hormone- and drug-refractory prostate cancer.
authors.affiliation: Department of Urology, UCLA School of Medicine, University of California at Los-Angeles, 90095, USA.
authors.forename: A
authors.initials: A
authors.lastname: Zisman
authors.forename: C P
authors.initials: CP
authors.lastname: Ng
authors.forename: A J
authors.initials: AJ
authors.lastname: Pantuck
authors.forename: B
authors.initials: B
authors.lastname: Bonavida
authors.forename: A S
authors.initials: AS
authors.lastname: Belldegrun
mesh_terms: D000728:Androgens / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology*; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004357:Drug Synergism; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011471:Prostatic Neoplasms; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D000093542:Gemcitabine
chemical_list: D000728:Androgens; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D003841:Deoxycytidine; D003609:Dactinomycin; D005047:Etoposide; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D017239:Paclitaxel; D002945:Cisplatin; D000093542:Gemcitabine