In addition, matriptase briefly expresses in two of five lung cancer cell lines,54 and hepsin is amplified only in 5.4% cases of lung adenocarcinoma.53 The results together suggest that matriptase and hepsin may not be implicated in HAI-2 downregulation-mediated lung adenocarcinoma progression. Here, SPINT2 is linked to lung adenocarcinoma.