Monocytes and the 38kDa-antigen of mycobacterium tuberculosis modulate natural killer cell activity and their cytolysis directed against ovarian cancer cell lines

BMC Cancer. 2012 Oct 4:12:451. doi: 10.1186/1471-2407-12-451.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • ATP-Binding Cassette Transporters / immunology*
  • ATP-Binding Cassette Transporters / pharmacology
  • Antibody-Dependent Cell Cytotoxicity / immunology*
  • Antigens, Bacterial / chemistry
  • Antigens, Bacterial / immunology*
  • Antigens, Bacterial / pharmacology
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / immunology*
  • Bacterial Proteins / pharmacology
  • Blotting, Western
  • Cell Communication / immunology
  • Cell Line, Tumor
  • Cells, Cultured
  • Coculture Techniques
  • ErbB Receptors / immunology
  • ErbB Receptors / metabolism
  • Female
  • Flow Cytometry
  • Humans
  • Interferon-gamma / genetics
  • Interferon-gamma / immunology
  • Interferon-gamma / metabolism
  • Interleukin-12 / genetics
  • Interleukin-12 / immunology
  • Interleukin-12 / metabolism
  • Interleukin-15 / genetics
  • Interleukin-15 / immunology
  • Interleukin-15 / metabolism
  • Interleukin-18 / genetics
  • Interleukin-18 / immunology
  • Interleukin-18 / metabolism
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / immunology*
  • Killer Cells, Natural / metabolism
  • Lymphocyte Activation / drug effects
  • Lymphocyte Activation / immunology
  • Molecular Weight
  • Monocytes / drug effects
  • Monocytes / immunology*
  • Monocytes / metabolism
  • Mycobacterium tuberculosis / immunology
  • Mycobacterium tuberculosis / metabolism
  • Ovarian Neoplasms / immunology
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / pathology
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • ATP-Binding Cassette Transporters
  • Antigens, Bacterial
  • Bacterial Proteins
  • Interleukin-15
  • Interleukin-18
  • PstS-1 protein, Mycobacterium tuberculosis
  • Interleukin-12
  • Interferon-gamma
  • EGFR protein, human
  • ErbB Receptors