title: [Effect of soluble PD-L1 released by lung cancer cells in regulating the function of T lymphocytes].
abstract: OBJECTIVE
  To explore the expression of soluble programmed death ligand-1 on lung cancer cells and to clarify its biological function through PD-1/PD-L1 pathway in regulating the function of T lymphocytes.
  
  
  METHODS
  Labeled monoclonal antibody and flow cytometry were used to analyze the expression of PD-L1 and its receptor PD-l on lung cancer cells and human T lymphocytes, respectively. The level of sPD-L1 in the supernatant of lung cancer cells was determined with an ELISA kit. The inhibition of proliferation of T lymphocytes by mPD-L1 and sPD-L1 was studied using CCK-8 incorporation.
  
  
  RESULTS
  Low or no expression [(16.08 ± 2.28)%] of PD-1 was found on resting T lymphocytes from human peripheral blood with flow cytometry, but up-regulated expression of PD-1 [(78.06 ± 7.21)%] was found on the surface of activated T lymphocytes. Soluble PD-L1 was found in supernatant of some lung cancer cell lines, such as H1299, HO8910, SPCA-1, H460, H446 cells, with PD-L1 expressing on their cell surface [(78.34 ± 10.25)%, (68.17 ± 11.56)%, (45.32 ± 7.98)%, (47.52 ± 9.62)% and (40.95 ± 8.56)%, respectively], but very low expression on A549 cells [(16.02 ± 6.28)%]. The level of mPD-L1 on H1299 cells was highest [(78.34 ± 10.25)%], compared with HO8910 cells (68.17 ± 11.56)%, SPCA-1 cells (45.32 ± 7.98)%, H446 cells (40.95 ± 8.56)%, and H460 cells (47.52 ± 9.62)%. At the same time, the sPD-L1 level on H1299 cells was low [(0.17 ± 0.01) ng/ml], compared with HO8910 cells (0.30 ± 0.03) ng/ml, SPCA-1cells (0.59 ± 0.03) ng/ml, H446 cells (0.34 ± 0.02) ng/ml, and H460 cells (0.57 ± 0.03) ng/ml, but not expressed on A549 cells. PD-L1 expressing H1299 cells inhibited the proliferation of T lymphocytes in the co-culture system. Supernatant of the cultured PD-L1(+) lung cancer cells also inhibited T cell proliferation. Anti-human PD-L1 blocking antibody could partly restore the proliferation capacity of T lymphocytes.
  
  
  CONCLUSIONS
  Membrane-bound PD-L1 and soluble PD-L1 released from lung cancer cells can effectively inhibit the proliferation of T lymphocytes in mixed culture system and down-regulate cell-mediated immunity in vitro. This may lead to inactivation of tumor antigen-specific T cells and immune escape of lung cancer cells.
authors.affiliation: Department of Respiratory Diseases, the Second Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Min-hua
authors.initials: MH
authors.lastname: Shi
authors.forename: Yu-fei
authors.initials: YF
authors.lastname: Xing
authors.forename: Zeng-li
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Jian-an
authors.initials: JA
authors.lastname: Huang
authors.forename: Yong-jing
authors.initials: YJ
authors.lastname: Chen
mesh_terms: D060890:B7-H1 Antigen / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018920:Coculture Techniques; D006801:Humans; D007111:Immunity, Cellular; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D008213:Lymphocyte Activation; D061026:Programmed Cell Death 1 Receptor / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D019139:Tumor Escape; D015854:Up-Regulation
chemical_list: D060890:B7-H1 Antigen; D061026:Programmed Cell Death 1 Receptor