title: Nitric oxide (NO) enhances pemetrexed cytotoxicity via NO‑cGMP signaling             in lung adenocarcinoma cells in vitro and in vivo.
abstract: Pemetrexed (PEM) is a novel, multitargeted, antifolate, antineoplastic agent for the treatment of non-small cell lung cancer and malignant pleural mesothelioma. Additional effects of nitric oxide (NO) donors on the chemosensitivity of cancers have been reported. However, the effects of an NO donor on PEM-induced cytotoxicity remain unknown. In this study, we investigated the effects of the NO donors, NOC-18 on the cytotoxicity in A549 cells in vitro and of nitroglycerin (GTN), on the tumor growth of Lewis lung carcinoma cells in a murine syngraft model treated with PEM. The effects of NO donors on the expression of proteins associated with PEM metabolism, including thymidylate synthase (TS), reduced folate carrier 1 (RFC1), folylpolyglutamate synthase (FPGS), γ-glutamyl hydrolase (GGH) and multidrug resistance-related protein (MRP)5, and the effects of cyclic guanosine mono-phosphate (cGMP) signaling on these proteins were examined in A549 cells. Treatment with 100 nM NOC-18 for 3 days significantly enhanced PEM-induced cytotoxicity and increased the expression of RFC1 and FPGS in A549 cells. Treatment with 10 nM 8-bromo-cGMP (8-Br-cGMP) for 3 days also increased the expression of RFC1 and FPGS in A549 cells. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µm) significantly reversed the increase in RFC1 and FPGS expression induced by 100 nM NOC-18 in A549 cells. Combination therapy with GTN and PEM significantly reduced tumor growth compared with PEM alone in the syngraft model. The enhanced antitumor effect of GTN plus PEM was significantly reversed by the concomitant addition of ODQ. These findings suggest that NO donors, such as NOC-18 and GTN, enhance the anticancer effects of PEM by increasing the RFC1 and FPGS expression and stimulating cGMP signaling pathways in cancer cells.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine,                     Kyoto University, Kyoto, Kyoto 606-8507, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nagai
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Yasuda
authors.forename: Yukimasa
authors.initials: Y
authors.lastname: Hatachi
authors.forename: Deng
authors.initials: D
authors.lastname: Xue
authors.forename: Takahiko
authors.initials: T
authors.lastname: Sasaki
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Yamaya
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sakamori
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Togashi
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Masago
authors.forename: Isao
authors.initials: I
authors.lastname: Ito
authors.forename: Young Hak
authors.initials: YH
authors.lastname: Kim
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mio
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima
mesh_terms: D000230:Adenocarcinoma; D000077192:Adenocarcinoma of Lung; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D018827:Carcinoma, Lewis Lung / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005971:Glutamates / Q000008:administration & dosage; D006147:Guanine / Q000008:administration & dosage / Q000031:analogs & derivatives; D006801:Humans; D008175:Lung Neoplasms; D051379:Mice; D008810:Mice, Inbred C57BL; D020030:Nitric Oxide Donors / Q000008:administration & dosage / Q000494:pharmacology*; D005996:Nitroglycerin / Q000008:administration & dosage; D009603:Nitroso Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D000068437:Pemetrexed; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism; D051818:Replication Protein C / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems; D047368:Tumor Burden / Q000187:drug effects
chemical_list: D005971:Glutamates; C093285:NOC 18; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; C081632:RFC1 protein, human; D000068437:Pemetrexed; D006147:Guanine; D051818:Replication Protein C; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D005996:Nitroglycerin