STK26 and neoplasm: ATG4B is an intriguing ATG that has been reported to have tumorigenic functions and is regarded as a potential therapeutic target and prognostic marker.166,167 As a member of the mammalian sterile20-like (STE) serine/threonine kinase (STK) family, MST4 is prone to promoting tumor development through its phosphorylation activity (e.g., activating the tumor-promoting p-ERK pathway168).