The aspartic protease family member napsin A is involved in processing of SP-B in alveolar epithelial cell type II (AECII), and can be used as a marker for adenocarcinomas of the lung (Chuman et al, 1999; Hirano et al, 2003; Dejmek et al, 2007). This evidence concerns the gene NAPSA and lung adenocarcinoma.