Attenuated anti-tumor activity of NK-92 cells by invasive human breast carcinoma MDA-MB-231 cells

[摘要] Background Natural killer (NK) cells are typical innate lymphocytes that directly kill cancer cells. However, the anti-tumor function of NK cells can be modulated by various cancers in a tumor microenvironment. Objective We investigated whether the functional characteristics of NK cells are affected by coculture with human breast carcinoma MCF-7 or MDA-MB231 cells and further examined the underlying molecular mechanisms that are associated with attenuated anti-tumor activity of NK cells. NK-92 cells were cocultured with MCF-7 or MDA-MB-231 cells at a ratio of 1:2 (target:effector) for 6 h. The cytotoxic effect of NK-92 cells was measured using CytoTox96 assay. The frequency of CD56, NKp30+, NKp44+, NKG2D+, and NKG2A+ in NK-92 cells was investigated using individual fluorescent antibodies and flow cytometry. In addition, the production of cytokines was measured using Human Cytokine Array C1 kit. Proteins in cancer cell lysates were quantified and the expressions of PI3K, pAkt, Stat3, and pStat3 were examined by western blot analysis. Results The cytotoxicity of NK-92 cells is greater against MCF-7 than against MDA-MB-231 cells and cocultures with MCF-7 or MDA-MB-231 cells increased the frequency of CD56dim population in NK-92 cells as well as IFN-γ production. The frequency of the NKp30+ or NKG2D+ population in NK-92 cells was significantly decreased in coculture with MCF-7 or MDA-MB-231 cells. However, the frequency of NKG2A+ expression in NK-92 cells was significantly increased in coculture with MCF-7 or MDA-MB-231 cells. The secretions of IL-6, IL-8, monocyte chemoattractant protein-1, and granulocyte–macrophage colony-stimulating factor were significantly higher in supernatant from coculture of NK-92 and MDA-MB-231 cells than in supernatants from NK-92 cell single culture or coculture of NK-92 and MCF-7 cells, which positively correlates with the enhanced expression of pStat3 in MDA-MB-231 cells cocultured with NK-92 cells. Conclusion These findings demonstrate that the anti-tumor function of NK-92 cells is significantly suppressed by an invasive human breast carcinoma, MDA-MB-231, and the impairment of NK-92 cell function is associated with the upregulation of the IL-6/Stat3 signaling pathway.

[关键词] NK-92 cells;MDA-MB-231 cells;Tumor invasion