PRF1 and non-small cell lung carcinoma: MUC21 expression showed significant negative correlations with IFNG (R = -0.13, P = 0.0014), PRF1 (R = -0.15, P = 0.00039), GZMB (R = -0.27, P = 3.3 × 10–11), and GZMA (R = -0.19, P = 3.7 × 10 − 6), indicating that upregulated MUC21 correlates with a decreased cytotoxic activity of NK and CD8+T cells in NSCLC patients (Fig. 6E).