title: Characterization of small spheres derived from various solid tumor cell lines: are they suitable targets for T cells?
abstract: T cell based immunotherapy has been investigated in a variety of malignancies and analyses have been mostly founded on in vitro data with tumor cell monolayers. However, three-dimensional (3D) culture models might mimic more closely the 'in vivo' conditions than 2D monolayers. Therefore, we analyzed the expression of tumor-associated antigens (TAA) and of molecules involved in antigen processing and presentation (APM) in tumor spheres, which served as an in vitro model for micrometastasis which might be enriched in tumor propagating cancer stem cells. For enrichment of sphere cells 12 human solid tumor cell lines were cultured in serum-free medium. Expression of a variety of TAA and APM were analyzed by RT-PCR and/or flow cytometry and compared to expression in corresponding adherent bulk cells grown in regular growth medium. Compared to adherent cells, spheres showed equal or higher mRNA expression levels of LMP2, LMP7 and MECL-1, of TAP1 and TAP2 transporters and, surprisingly, also of TAA including differentiation antigens. However, downregulation or loss of HLA-I and HLA-II molecules in spheres was observed in 8 of 10 and 1 of 2 cell lines, respectively, and was unresponsive to stimulation with IFN-γ. Although tumor spheres express TAA and molecules of intracellular antigen processing, they are defective in antigen presentation due to downregulation of HLA surface expression which may lead to immune evasion.
authors.affiliation: Department of Medicine III, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12200, Berlin, Germany, antonia.busse@charite.de.
authors.forename: Antonia
authors.initials: A
authors.lastname: Busse
authors.forename: Anne
authors.initials: A
authors.lastname: Letsch
authors.forename: Alberto
authors.initials: A
authors.lastname: Fusi
authors.forename: Anika
authors.initials: A
authors.lastname: Nonnenmacher
authors.forename: David
authors.initials: D
authors.lastname: Stather
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ochsenreither
authors.forename: Christian R A
authors.initials: CR
authors.lastname: Regenbrecht
authors.forename: Ulrich
authors.initials: U
authors.lastname: Keilholz
mesh_terms: D017951:Antigen Presentation; D000951:Antigens, Neoplasm / Q000032:analysis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006680:HLA Antigens / Q000032:analysis; D006801:Humans; D007167:Immunotherapy; D007371:Interferon-gamma / Q000502:physiology; D009369:Neoplasms / Q000473:pathology* / Q000628:therapy; D014411:Neoplastic Stem Cells / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology*; D019139:Tumor Escape
chemical_list: D000951:Antigens, Neoplasm; D006680:HLA Antigens; D007371:Interferon-gamma