Additionally, there is evidence presenting that kallikrein-related peptidase 6 (KLK6) and trypsin, two members of the serine protease family, can activate protease-activated receptor-2 (PAR2) to boost the growth of lung adenocarcinoma (LUAD) cells, thus to advance cancer progression [5–7]. Here, KLK6 is linked to lung adenocarcinoma.