BTNL9 and neoplasm: Single-cell RNA (scRNA) analysis of LUAD using CancerSEA [34] database (Fig. 5E) showed that BTNL9 expression is significantly negatively correlated with tumor malignant features including invasion (r = − 0.53, P < 0.0001), metastasis (r = − 0.35, P = 0.011), EMT (r = − 0.47, P = 0.0006), proliferation (r = − 0.37, P = 0.0086), Hypoxia (r = − 0.36, P = 0.011), and DNA damage (r = − 0.34, P = 0.017) (Fig. 5F).