title: The human immunodeficiency virus protease inhibitor ritonavir inhibits lung cancer cells, in part, by inhibition of survivin.
abstract: BACKGROUND
  Ritonavir is a potential therapeutic agent in lung cancer, but its targets in lung adenocarcinoma are unknown, as are candidate biomarkers for its activity.
  
  
  METHODS
  RNAi was used to identify genes whose expression affects ritonavir sensitivity. Synergy between ritonavir, gemcitabine, and cisplatin was tested by isobologram analysis.
  
  
  RESULTS
  Ritonavir inhibits growth of K-ras mutant lung adenocarcinoma lines A549, H522, H23, and K-ras wild-type line H838. Ritonavir causes G0/G1 arrest and apoptosis. Associated with G0/G1 arrest, ritonavir down-regulates cyclin-dependent kinases, cyclin D1, and retinoblastoma protein phosphorylation. Associated with induction of apoptosis, ritonavir reduces survivin messenger RNA and protein levels more than twofold. Ritonavir inhibits phosphorylation of c-Src and signal transducer and activator of transcription protein 3, which are important events for survivin gene expression and cell growth, and induces cleavage of PARP1. Although knock down of survivin, c-Src, or signal transducer and activator of transcription protein 3 inhibits cell growth, only survivin knock down enhances ritonavir inhibition of growth and survivin overexpression promotes ritonavir resistance. Ritonavir was tested in combination with gemcitabine or cisplatin, exhibiting synergistic and additive effects, respectively. The combination of ritonavir/gemcitabine/cisplatin is synergistic in the A549 line and additive in the H522 line, at clinically feasible ritonavir concentrations (<10 μM).
  
  
  CONCLUSIONS
  Ritonavir is of interest for lung adenocarcinoma therapeutics, and survivin is an important target and potential biomarker for its sensitivity. Ritonavir cooperation with gemcitabine/cisplatin might be explained by involvement of PARP1 in repair of cisplatin-mediated DNA damage and survivin in repair of gemcitabine-mediated double-stranded DNA breaks.
authors.affiliation: Division of Hematology, Oncology and Transplantation, University of Minnesota and University of Minnesota Cancer Center, Minneapolis, MN 55455, USA.
authors.forename: Anjaiah
authors.initials: A
authors.lastname: Srirangam
authors.forename: Monica
authors.initials: M
authors.lastname: Milani
authors.forename: Ranjana
authors.initials: R
authors.lastname: Mitra
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Guo
authors.forename: Mariangellys
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Hitesh
authors.initials: H
authors.lastname: Kathuria
authors.forename: Seiji
authors.initials: S
authors.lastname: Fukuda
authors.forename: Anthony
authors.initials: A
authors.lastname: Rizzardi
authors.forename: Stephen
authors.initials: S
authors.lastname: Schmechel
authors.forename: David G
authors.initials: DG
authors.lastname: Skalnik
authors.forename: Louis M
authors.initials: LM
authors.lastname: Pelus
authors.forename: David A
authors.initials: DA
authors.lastname: Potter
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000008:administration & dosage; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004359:Drug Therapy, Combination; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019438:Ritonavir / Q000494:pharmacology*; D000077022:Survivin; D014407:Tumor Cells, Cultured; D000093542:Gemcitabine
chemical_list: C107489:BIRC5 protein, human; C530104:CCND1 protein, human; D017320:HIV Protease Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077022:Survivin; D003841:Deoxycytidine; D019938:Cyclin D1; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D019438:Ritonavir; D002945:Cisplatin; D000093542:Gemcitabine