title: Pharmacological modulation of cytotoxicity and cellular uptake of anti-cancer drugs by PDE5 inhibitors in lung cancer cells.
abstract: OBJECTIVE
  Previous research has led to the recognition of a cGMP signaling pathway governing drug transport. This study is to investigate whether inhibitors of phosphodiesterase type 5 (PDE5), which increase intracellular cGMP levels, modulate the cytotoxicity and uptake of anti-cancer drugs in cancer cells.
  
  
  METHODS
  The experiments were conducted with and without PDE5 inhibitors: dipyridamole, vardenafil, and/or sildenafil. The cytotoxicity of doxorubicin, cisplatin and oxaliplatin was determined in multiple cancer cell lines derived from different tissues. The cellular uptake of structurally diverse compounds was further examined in lung cancer cells with and without various endocytotic inhibitors. The tumor accumulation and the anti-tumor effect of trastuzumab were examined in a lung cancer xenograft mouse model.
  
  
  RESULTS
  Dipyridamole could modulate the cytotoxicity of doxorubicin, cisplatin, and oxaliplatin in cancer cells. Particularly, PDE5 inhibitors increased cellular uptake of structurally diverse compounds into lung cancer cells both in vitro and in vivo. The effect of vardenafil on drug uptake could be blocked by endocytotic inhibitors. The growth of lung cancer xenograft in nude mice was significantly suppressed by addition of vardenafil to trastuzumab treatment.
  
  
  CONCLUSIONS
  PDE5 inhibitors may increase the efficacy of anti-cancer drugs by increasing endocytosis-mediated cellular drug uptake, and thus serve as adjuvant therapy for certain cancers such as lung cancer.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland at Baltimore, 20 Penn Street, HSFII Room 555, Baltimore, Maryland, 21201, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Shu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D006152:Cyclic GMP / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D061986:MCF-7 Cells; D051379:Mice; D008819:Mice, Nude; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D058986:Phosphodiesterase 5 Inhibitors; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP