Among them, A549, PC-9 and H1975 lung adenocarcinoma cells were originally isolated from in situ lung cancer lesions and represent the non-metastatic group of lung adenocarcinoma; pleural effusion-derived cells (CL141 and CL97) and lymph node-derived cells (H1299) are considered to be the metastatic group of lung adenocarcinoma.34–37 The results from cell invasion assays showed that the cells in the metastatic group had highly invasive abilities (Fig. 1a, upper panel) and expressed low levels of HAI-2, compared to those in the non-metastatic (in situ) group (Fig. 1a, lower panel). Here, SPINT2 is linked to Pleural effusion.