BGN and cancer: Biglycan (BGN), a member of small leucine rich PGs (SLRPGs) (Schaefer et al., 2017), is overexpressed and secreted by various cancers (Wang et al., 2011; Liu et al., 2014; Fujiwara-Tani et al., 2020), which is related to the regulation of immunological responses (Neill et al., 2015).