title: Arrest of B16 melanoma cells in the mouse pulmonary microcirculation induces endothelial nitric oxide synthase-dependent nitric oxide release that is cytotoxic to the tumor cells.
abstract: Metastatic cancer cells seed the lung via blood vessels. Because endothelial cells generate nitric oxide (NO) in response to shear stress, we postulated that the arrest of cancer cells in the pulmonary microcirculation causes the release of NO in the lung. After intravenous injection of B16F1 melanoma cells, pulmonary NO increased sevenfold throughout 20 minutes and approached basal levels by 4 hours. NO induction was blocked by N(G)-nitro-L-arginine methyl ester (L-NAME) and was not observed in endothelial nitric oxide synthase (eNOS)-deficient mice. NO production, visualized ex vivo with the fluorescent NO probe diaminofluorescein diacetate, increased rapidly at the site of tumor cell arrest, and continued to increase throughout 20 minutes. Arrested tumor cells underwent apoptosis with apoptotic counts more than threefold over baseline at 8 and 48 hours. Neither the NO signals nor increased apoptosis were seen in eNOS knockout mice or mice pretreated with L-NAME. At 48 hours, 83% of the arrested cells had cleared from the lungs of wild-type mice but only approximately 55% of the cells cleared from eNOS-deficient or L-NAME pretreated mice. eNOS knockout and L-NAME-treated mice had twofold to fivefold more metastases than wild-type mice, measured by the number of surface nodules or by histomorphometry. We conclude that tumor cell arrest in the pulmonary microcirculation induces eNOS-dependent NO release by the endothelium adjacent to the arrested tumor cells and that NO is one factor that causes tumor cell apoptosis, clearance from the lung, and inhibition of metastasis.
authors.affiliation: Department of Pathology, Faculty of Medicine, and the Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Hongming
authors.initials: H
authors.lastname: Qiu
authors.forename: F William
authors.initials: FW
authors.lastname: Orr
authors.forename: Derrek
authors.initials: D
authors.lastname: Jensen
authors.forename: Hui Helen
authors.initials: HH
authors.lastname: Wang
authors.forename: Alan R
authors.initials: AR
authors.lastname: McIntosh
authors.forename: Brian B
authors.initials: BB
authors.lastname: Hasinoff
authors.forename: Dwight M
authors.initials: DM
authors.lastname: Nance
authors.forename: Susan
authors.initials: S
authors.lastname: Pylypas
authors.forename: Ke
authors.initials: K
authors.lastname: Qi
authors.forename: Chun
authors.initials: C
authors.lastname: Song
authors.forename: Ruth J
authors.initials: RJ
authors.lastname: Muschel
authors.forename: Abu-Bakr
authors.initials: AB
authors.lastname: Al-Mehdi
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology*; D004730:Endothelium, Vascular / Q000473:pathology*; D004790:Enzyme Induction; D007700:Kinetics; D008546:Melanoma, Experimental / Q000098:blood supply / Q000201:enzymology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008833:Microcirculation / Q000473:pathology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009362:Neoplasm Metastasis / Q000473:pathology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019335:Nitroarginine / Q000494:pharmacology; D011652:Pulmonary Circulation / Q000502:physiology*; D013997:Time Factors
chemical_list: D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019331:NG-Nitroarginine Methyl Ester