SDF-1α Reduces Human Natural Killer Cell Cytotoxicity against Chronic Myelogenous Leukemia K562 Cells

Stromal cell-derived factor-1 alpha (SDF-1α) has been shown to be up-regulated in a variety of malignancies. So that, its expression is associated with poor prognosis and invasiveness. Natural killer (NK) cells are important effector cells against virus-infected and transformed cells. Especially they play a key role in tumor immune surveillance. Whereas it was not well understood whether SDF-1α modulates anti-tumor immune response or not, the purpose of the present study was to investigate the effect of SDF-1α on the cytotoxic properties of peripheral blood NK cells. Human peripheral blood NK cells were freshly isolated using MACSxpess system and cultured in the presence or absence of recombinant human SDF-1α or SDF-1α plus CXCR4 antagonist, AMD3100. CD107a degranulation assay was conducted through the co-culture of NK cells with K562 cells. The percentage of CD107a positive cells was assessed by flowcytometry. Effect of SDF-1α was also examined on the mRNA levels of NKG2A and NKG2D as indicator examples of NK cell inhibitory and activating receptors, respectively. SDF-1α significantly decreased the degranulation activity of NK cells (p=0.04). The mRNA content of NKG2D was down-regulated under the influence of SDF-1α (p=0.03). Moreover, AMD3100 exhibited a trend in recovering the NKG2D mRNA level to its un-treated state (p=0.05).  The present study reveals that SDF-1α has a negative impact on NK cell activity and might is involved in tumor immune-suppression. Thus, it can be concluded that microenvironment manipulations targeting SDF-1α may reinforce current cancer therapies by disturbing one of the immune-suppressive axes in the cancerous milieu.