Figure 1.

Culture supernatants of thyroid cancer cells inhibit natural killer (NK) cell cytotoxicity. (A) NK cells were cultured with IL-2 either in control medium (circle) or in medium containing culture supernatant of thyroid cancer cells including TPC-1 (cross), FRO (triangle), and 850-5C (diamond) for 48 h. The cytotoxicity of the NK cells was assessed relative to K562 cells at different E:T ratio as described in Section “Materials and Methods.” Bars represent mean ± SD from three experiments. (B) Percent cytotoxicity by NK cells treated with culture supernatants of thyroid cancer cells relative to NK cells grown in control medium. K562 cells were used as targets and the effector:target (E:T) ratio was bar which represent mean ± SD of three independent experiments. Statistical analysis was performed using the paired two-tailed Student’s t-test. *P < 0.05 and ***P < 0.001. (C) Expression of NK activating receptors and death receptors (profiles filled with dark gray), inhibitory receptors (profiles filled with light gray), and isotype controls (white profiles) was analyzed by flow cytometry. Numbers indicate mean fluorescence intensity. Y-axis shows cell counts.