title: Monocytes and the 38kDa-antigen of mycobacterium tuberculosis modulate natural killer cell activity and their cytolysis directed against ovarian cancer cell lines.
abstract: BACKGROUND
  Despite strong efforts to improve clinical outcome of ovarian cancer patients by conventional and targeted immuno-based therapies, the prognosis of advanced ovarian cancer is still poor. Natural killer (NK) cells mediate antibody-dependent cellular cytotoxicity (ADCC), release immunostimulatory cytokines and thus function as potent anti-tumour effector cells. However, tumour cells developed mechanisms to escape from an effective immune response. So highly immunogenic substances, like the 38 kDa-preparation of M. tuberculosis, PstS-1, are explored for their potential to enhance cancer-targeted immune responses. In this study we examined the modulation of different NK cell functions by accessory monocytes and PstS-1. We focussed on NK cell activation as well as natural and antibody-dependent cellular cytotoxicity directed against epidermal-growth-factor-receptor (EGFR)-positive ovarian cancer cell lines.
  
  
  METHODS
  Activation, cytokine release and cytotoxicity of NK cells stimulated by monocytes and PstS-1 were determined by FACS-analysis, ELISA, Bioplex assay and quantitative polymerase-chain reaction (qPCR). Transwell assays were used to discriminate cell-cell contact-dependent from contact-independent mechanisms. Five ovarian cancer cell lines (A2780, IGROV-1, OVCAR-3, OVCAR-4 and SKOV-3) with different EGFR-expression were used as target cells for natural and antibody-dependent cellular cytotoxicity assays. Cetuximab (anti-EGFR-antibody) was used for ADCC studies.
  
  
  RESULTS
  Our data show that monocytes effectively enhance activation as well natural and antibody-dependent cytolytic activity of NK cells. PstS-1 directly stimulated monocytes and further activated monocyte-NK-co-cultures. However, PstS-1 did not directly influence purified NK cells and did also not affect natural and antibody-dependent cellular cytotoxicity directed against EGFR-positive ovarian cancer cells, even in presence of monocytes. Direct cell-cell contact between NK cells and monocytes was required for NK activation, while released cytokines seemed to play a minor role.
  
  
  CONCLUSIONS
  Our data suggest that monocytes enhance natural and antibody-dependent cytotoxic activity of NK cells in a cell-cell contact dependent manner. The TLR-agonist PstS-1 provides additional monocyte activation and induces NK activation markers, while NK cytotoxicity remains unaffected. We conclude that monocytes provide accessory function for ADCC exerted by NK during antibody-based cancer immunotherapy directed against EGFR-positive ovarian cancer cells.
authors.affiliation: Department of Otorhinolaryngology, University of Duisburg-Essen, Essen 45147, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Gottschalk
authors.forename: Stephan
authors.initials: S
authors.lastname: Lang
authors.forename: Rainer
authors.initials: R
authors.lastname: Kimmig
authors.forename: Mahavir
authors.initials: M
authors.lastname: Singh
authors.forename: Sven
authors.initials: S
authors.lastname: Brandau
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology*; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D015153:Blotting, Western; D002450:Cell Communication / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D018920:Coculture Techniques; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019409:Interleukin-15 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020382:Interleukin-18 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008970:Molecular Weight; D009000:Monocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018528:ATP-Binding Cassette Transporters; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D019409:Interleukin-15; D020382:Interleukin-18; C581205:PstS-1 protein, Mycobacterium tuberculosis; D018664:Interleukin-12; D007371:Interferon-gamma; C512478:EGFR protein, human; D066246:ErbB Receptors