B10

Recombinant human granulocyte-colony stimulating factor (rhG-CSF) is the most common hematopoietic growth factor used for treatment of chemotherapy-induced neutropenia or mobilization of hematopoietic stem cells for transplantation. Natural killer (NK) cells, regulate cytotoxic response in both innate and adaptive immunity, are critical for host defense against infected cells and tumors. However, the cellular and molecular events of NK cells responding to rhG-CSF remain unclear. Toward this end, we treated human NK cells with rhG-CSF and assessed their cytotoxic function as well as proteomic characteristics. Unlike the other tested hematopoietic cytokines, rhG-CSF decreased NK cell-mediated cytotoxicity without affecting the viability of NK cells. rhG-CSF also reduced the production of nitric oxide and expression of inducible nitric oxide synthase in rhIL-2-activated NK cells. By using cytokine array, rhG-CSF reduced secretion of growth-related oncogene (GRO)-α from NK cells. Intriguingly, rhG-CSF did not affect production of various inflammatory cytokines (MCP-1, IL-6, TNF-α, GM-CSF and IL-8) which are markedly stimulated by rhGM-CSF. Proteomic analysis of rhG-CSF- and rhGM-CSF-treated NK cells by two-dimensional gel electrophoresis and mass spectrometry uncovered unique molecules possibly involving rhG-CSF effect. These proteins were classified into 6 groups according to their functions as follows: glycolysis, apoptosis, cytotoxicity, inflammation, antigen processing and presentation, and the others. We conclude that although rhG-CSF is beneficial to myelopoiesis, it may impair NK-mediated cytotoxicity accompanied by alterations in protein expression profile distinct from that of rhGM-CSF. To validate this unwanted immune shaping by rhG-CSF, further in vivo or clinical investigations are warranted.

Second AACR Centennial Conference on Translational Cancer Medicine-- July 20-23, 2008; Monterey, CA