Hypoxia Impairs NK Cell Cytotoxicity through SHP-1-Mediated Attenuation of STAT3 and ERK Signaling Pathways

Figure 3

Hypoxia diminishes the phosphorylation level of ERK and STAT3. (a–c) Western blotting analysis shows the expression levels of the phosphorylated ERK and STAT3 in KHYG-1 (a), NK92 (b), and primary NK cells (c), respectively. Upper panel: representative Western blot images are shown from three independent experiments; lower panel: densitometric analysis of the p-ERK/ERK and p-STAT3/STAT3 band gray optical density ratios (, , ). (d) Inhibition of ERK and STAT3 decreases the expression of activating receptors on the NK cell surface. Representative flow cytometry results show the effects of STAT3 inhibitor cryptotanshinone (CPT) (upper panel) and ERK inhibitor U0126 (lower panel) on the expression of activating receptors on the NK cell surface. Left panel: one of three representative flow cytometry results; Right panel: statistical analysis of the flow cytometry data (, , ). KHYG-1 and NK92 cells were treated with vehicle, 10 μM ERK inhibitor U0126, and 10 μM STAT3 inhibitor CPT for 24 h. (e) Inhibition of ERK and STAT3 decreases NK cell cytotoxicity. Statistical analysis showing the effects of ERK and STAT3 inhibition on NK cells cytotoxicity against K562 cells (, , ). KHYG-1 cells were pretreated with 10 μM U0126 and 10 μM CPT for 6 h and then incubated with K562 at different ratios for 4 h.

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