title: Deletion of cyclooxygenase 2 in mouse mammary epithelial cells delays breast cancer onset through augmentation of type 1 immune responses in tumors.
abstract: Inhibition of cyclooxygenase (COX) 2, which is associated with >40% of breast cancers, decreases the risk of tumorigenesis and breast cancer recurrence. To study the role of COX-2 in breast cancer, we engineered mice that lack selectively mammary epithelial cell (MEC) COX-2 (COX-2 KO(MEC)). Compared with wild type (WT), MEC from COX-2 KO(MEC) mice expressed >90% less COX-2 messenger RNA (mRNA) and protein and produced 90% less of the dominant pro-oncogenic COX-2 product, prostaglandin (PG) E(2). We confirmed COX-2 as the principle source of PGE(2) in MEC treated with selective COX-2 and COX-1 inhibitors. Tumors were induced in mice using medroxyprogesterone acetate and 7,12-dimethylbenz[a]anthracene. Breast cancer onset was significantly delayed in COX-2 KO(MEC) compared with WT (P = 0.03), equivalent to the delay following systemic COX-2 inhibition with rofecoxib. Compared with WT, COX-2 KO(MEC) tumors showed increased mRNA for Caspase-3, Ki-67 and common markers for leukocytes (CD45) and macrophages (F4/80). Analysis of multiple markers/cytokines, namely CD86, inducible nitric oxide synthase (iNOS), interleukin-6, tumor necrosis factor α (TNFα) and Tim-3 indicated a shift toward antitumorigenic type 1 immune responses in COX-2 KO(MEC) tumors. Immunohistochemical analysis confirmed elevated expression of CD45, F4/80 and CD86 in COX-2 KO(MEC) tumors. Concordant with a role for COX-2 in restraining M1 macrophage polarization, CD86 and TNFα expression were offset by exogenous PGE(2) in bone marrow-derived macrophages polarized in vitro to the M1 phenotype. Our data reveal the importance of epithelial COX-2 in tumor promotion and indicate that deletion of epithelial COX-2 may skew tumor immunity toward type 1 responses, coincident with delayed tumor development.
authors.affiliation: Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Nune
authors.initials: N
authors.lastname: Markosyan
authors.forename: Edward P
authors.initials: EP
authors.lastname: Chen
authors.forename: Victoire N
authors.initials: VN
authors.lastname: Ndong
authors.forename: Yubing
authors.initials: Y
authors.lastname: Yao
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Sterner
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Chodosh
authors.forename: John A
authors.initials: JA
authors.lastname: Lawson
authors.forename: Garret A
authors.initials: GA
authors.lastname: Fitzgerald
authors.forename: Emer M
authors.initials: EM
authors.lastname: Smyth
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity; D002478:Cells, Cultured; D003280:Contraceptives, Oral, Synthetic / Q000633:toxicity; D051546:Cyclooxygenase 2 / Q000502:physiology*; D016207:Cytokines / Q000378:metabolism; D015777:Eicosanoids / Q000378:metabolism; D004847:Epithelial Cells / Q000276:immunology* / Q000378:metabolism; D005260:Female; D007124:Immunoenzyme Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000378:metabolism; D008297:Male; D008321:Mammary Glands, Animal / Q000276:immunology* / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000276:immunology* / Q000517:prevention & control*; D008525:Medroxyprogesterone / Q000633:toxicity; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018417:Th1 Cells / Q000276:immunology* / Q000378:metabolism
chemical_list: D002273:Carcinogens; D003280:Contraceptives, Oral, Synthetic; D016207:Cytokines; D015777:Eicosanoids; D018836:Inflammation Mediators; D012333:RNA, Messenger; D015127:9,10-Dimethyl-1,2-benzanthracene; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D008525:Medroxyprogesterone