PiRNAs are a small class of non-coding small RNAs newly discovered in recent years. Millions of
piRNAs have been discovered to date, and more than 20,000
piRNA genes have been found in the human genome. Due to the relatively small number of studies related to
piRNA, our understanding of
piRNAs is very limited. Currently, the clear biological function of
piRNAs is transposon mobilization inhibition by promoting transcript degradation and regulating
chromatin formation. In addition,
piRNAs can form
piRNA-PIWI
protein complexes with some members of the PIWI branch of the
Argonaute protein. Based on these biological functions,
piRNAs and PIWI
proteins are important in maintaining the genomic integrity of germline cells. Because of this, the popularity of
piRNAs research has been focused on its role in germline cells for a long time after the discovery of
piRNAs. As the field of research expands, there is growing evidence that
piRNAs and PIWI
proteins are abnormally expressed in various types of
cancers, which may be potential
cancer biomarkers and
cancer therapeutic targets. In this review, we will focus on the relationship between
piRNAs and PIWI
proteins and
cancers based on previous research, as well as their significance in
cancer detection, grading and treatment.