MST1 and familial pancreatic carcinoma: As a valuable tumor suppressor gene, the KL protein is expressed at a low rate in various cancerous tissues, including renal, breast, liver, lung, and pancreatic cancers, which elucidates its ability to inhibit tumor cell growth.[13] Mammalian STE20-like kinase 1 (MST1) is a Hepatocyte growth factor-like protein alpha chain and a link in the Hippo pathway.