title: Mitochondria of a human multidrug-resistant hepatocellular carcinoma cell line constitutively express inducible nitric oxide synthase in the inner membrane.
abstract: Mitochondria play a crucial role in pathways of stress conditions. They can be transported from one cell to another, bringing their features to the cell where they are transported. It has been shown in cancer cells overexpressing multidrug resistance (MDR) that mitochondria express proteins involved in drug resistance such as P-glycoprotein (P-gp), breast cancer resistant protein and multiple resistance protein-1. The MDR phenotype is associated with the constitutive expression of COX-2 and iNOS, whereas celecoxib, a specific inhibitor of COX-2 activity, reverses drug resistance of MDR cells by releasing cytochrome c from mitochondria. It is possible that COX-2 and iNOS are also expressed in mitochondria of cancer cells overexpressing the MDR phenotype. This study involved experiments using the human HCC PLC/PRF/5 cell line with and without MDR phenotype and melanoma A375 cells that do not express the MDR1 phenotype but they do iNOS. Western blot analysis, confocal immunofluorescence and immune electron microscopy showed that iNOS is localized in mitochondria of MDR1-positive cells, whereas COX-2 is not. Low and moderate concentrations of celecoxib modulate the expression of iNOS and P-gp in mitochondria of MDR cancer cells independently from inhibition of COX-2 activity. However, A375 cells that express iNOS also in mitochondria, were not MDR1 positive. In conclusion, iNOS can be localized in mitochondria of HCC cells overexpressing MDR1 phenotype, however this phenomenon appears independent from the MDR1 phenotype occurrence. The presence of iNOS in mitochondria of human HCC cells phenotype probably concurs to a more aggressive behaviour of cancer cells.
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Internal Medicine and Hepatology, University of Florence and Azienda Ospedaliero Universitaria Careggi, Florence, Italy.
authors.forename: Ornella
authors.initials: O
authors.lastname: Fantappiè
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Anatomy and Histology, University of Florence, Florence, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Sassoli
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Anatomy and Histology, University of Florence, Florence, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Tani
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Anatomy and Histology, University of Florence, Florence, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Nosi
authors.affiliation: Department of Experimental Therapy and Medical Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Serena
authors.initials: S
authors.lastname: Marchetti
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Anatomy and Histology, University of Florence, Florence, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Formigli
authors.affiliation: Department of Experimental and Clinical Medicine - Section of Internal Medicine and Hepatology, University of Florence and Azienda Ospedaliero Universitaria Careggi, Florence, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Mazzanti
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000068579:Celecoxib / Q000494:pharmacology; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D052246:Cyclooxygenase 2 Inhibitors; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D000068579:Celecoxib
keywords: COX-2; MDR; coxib; iNOS; mitochondrion