PRF1 and erythroleukemia: In this study, Cirsiliol, a dimethoxylated flavone enhanced the cytolytic activity of KHYG-1 NK cells concentration-dependently against erythroleukemia K562 cells (Fig. 4A) and induced perforin and granzyme B approximately concentration-dependently between 0.2 μM and 15 μM of cirsiliol for 24 h, suggesting that increase of NK activity was triggered by exocytosis of cytolytic granules by NK cells (Fig. 4B).