As a precursor of effective angiopoietin-2, such protein is a potential biomarker in brain cancer (Seifert et al., 2015), breast cancer (Han et al., 2016), multiple myeloma (Nowicki et al., 2017), and pancreatic cancer (Chou et al., 2016), but not esophageal cancer and normal controls, together with ANGPT2. Here, ANGPT2 is linked to AL amyloidosis.