title: Urokinase-mediated recruitment of myeloid-derived suppressor cells and their suppressive mechanisms are blocked by MUC1/sec.
abstract: The transmembrane isoform of mucin 1 (MUC1/TM) is a well-recognized tumor antigen, contributing to tumorigenesis and immune evasion. Although MUC1/TM has been correlated with malignancy, we have previously reported on antitumor properties and prevention of tumor development by a secreted splice variant of MUC1 (MUC1/sec). Because myeloid-derived suppressor cells (MDSCs) play a critical role in tumor-induced immunosuppression, we investigated their recruitment by tumor cells expressing either MUC1/TM or MUC1/sec. DA-3 tumor cells expressing MUC1/sec recruit dramatically lower levels of MDSCs, relative to MUC1/TM-expressing DA-3 cells. Because MUC1/sec was previously shown to down-regulate tumor expression of urokinase plasminogen activator (uPA), a protease linked to tumor aggressiveness and metastasis, the potential role of uPA in MDSC recruitment was investigated. Tumor-derived uPA is capable of recruiting MDSCs, and correlates with tumor development. In addition to diminishing recruitment of MDSCs, the effect of MUC1/sec on MDSC-suppressive mechanisms was investigated. MUC1/sec, or its unique immunoenhancing peptide, is capable of blocking expression of arginase 1 and production of reactive oxygen species in MDSCs, implicated in the suppression of T cells. These findings demonstrate a new mechanism of MDSC recruitment, and provide evidence that MUC1/sec has antitumor properties affecting MDSCs.
authors.affiliation: Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, FL 33101, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Ilkovitch
authors.forename: Diana M
authors.initials: DM
authors.lastname: Lopez
mesh_terms: D000818:Animals; D001119:Arginase / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008822:Mice, Transgenic; D018396:Mucin-1 / Q000502:physiology*; D022423:Myeloid Cells / Q000473:pathology*; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018396:Mucin-1; D017382:Reactive Oxygen Species; D014568:Urokinase-Type Plasminogen Activator; D020780:Matrix Metalloproteinase 9; D001119:Arginase