PIWI-L1 is a member of the PIWI subfamily of Argonaute proteins, evolutionarily conserved proteins containing both PAZ and Piwi motifs that are crucial for the biogenesis and function of small non-coding RNAs and play important roles in stem cell self-renewal, RNA silencing, and translational regulation in diverse organisms. PIWI-L1 is thought to play a role as an intrinsic regulator of the self-renewal capacity of germline and hematopoietic stem cells as removing PIWI-L1 protein from single germline stem cells significantly decreases the rate of their division. Recent studies have shown that overexpression of PIWI-L1 (as well as other PIWI-like proteins) are potential biomarkers for colon and other cancers.