KLK4 and lung adenocarcinoma: Significantly higher levels of CA15-3 (138.6 U/mL vs 21.3 U/mL) and CA19-9 (516.6 U/mL vs 181.5 U/mL) were found in 128 lung adenocarcinoma cases than in 18 mesotheliomas.17 Kallikreins are a subgroup of serine proteases which have been implicated in carcinogenesis.