IGFBPL1 is a secreted IGF (Insulin-like growth factor) binding protein that is known to contain an Ig-like C2-type (immunoglobulin-like) domain, an IGFBP N-terminal domain and a Kazal-like domain. IGF-binding proteins characteristically act to extend the half-life of IGFs and may influence the growth promoting effects of the IGFs. The interaction of IGFBPs with IGFs can affect cell surface receptors, specifically, IGFBPs may enhance or decrease a cells insulin sensitivity. IGFBPL1 has been found to be down-regulated in multiple tumors and thus may be a likely tumor suppressor candidate. Highly expressed in both brain and testis, IGFBPL1 is found at lower levels in the prostate, bladder and lung.