title: Cancer-expanded myeloid-derived suppressor cells induce anergy of NK cells through membrane-bound TGF-beta 1.
abstract: NK cells, the important effector of innate immunity, play critical roles in the antitumor immunity. Myeloid-derived suppressor cells (MDSC), a population of CD11b(+)Gr-1(+) myeloid cells expanded dramatically during tumor progression, can inhibit T cells and dendritic cells, contributing to tumor immune escape. However, regulation of NK cell innate function by MDSC in tumor-bearing host needs to be investigated. In this study, we found that the function of NK cells from liver and spleen was impaired significantly in all tumor-bearing models, indicating the impairment of hepatic NK cell function by tumor is a universal phenomenon. Then we prepared the orthotopic liver cancer-bearing mice as tumor model to investigate how hepatic NK cells are impaired. We show that down-regulation of NK cell function is inversely correlated with the marked increase of MDSC in liver and spleen. MDSC inhibit cytotoxicity, NKG2D expression, and IFN-gamma production of NK cells both in vitro and in vivo. After incubation with MDSC, NK cells could not be activated to produce IFN-gamma. Furthermore, membrane-bound TGF-beta1 on MDSC is responsible for MDSC-mediated suppression of NK cells. The impaired function of hepatic NK cells in orthotopic liver cancer-bearing mice could be restored by depletion of MDSC, but not regulatory T cells. Therefore, cancer-expanded MDSC can induce anergy of NK cells via membrane-bound TGF-beta1. MDSC, but not regulatory T cells, are main negative regulator of hepatic NK cell function in tumor-bearing host. Our study provides new mechanistic explanations for tumor immune escape.
authors.affiliation: Institute of Immunology, Zhejiang University School of Medicine, Hangzhou, Peoples Republic of China.
authors.forename: Hequan
authors.initials: H
authors.lastname: Li
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Han
authors.forename: Qiuli
authors.initials: Q
authors.lastname: Guo
authors.forename: Minggang
authors.initials: M
authors.lastname: Zhang
authors.forename: Xuetao
authors.initials: X
authors.lastname: Cao
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000276:immunology; D045744:Cell Line, Tumor; D017635:Clonal Anergy / Q000276:immunology*; D018920:Coculture Techniques; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D022423:Myeloid Cells / Q000276:immunology* / Q000473:pathology / Q000637:transplantation; D009368:Neoplasm Transplantation; D011485:Protein Binding / Q000276:immunology; D053773:Transforming Growth Factor beta1 / Q000378:metabolism / Q000502:physiology*; D019139:Tumor Escape / Q000276:immunology
chemical_list: D008565:Membrane Proteins; D053773:Transforming Growth Factor beta1