The function and regulation mechanism of piRNAs in human cancers.

Piwi-interacting RNAs (piRNAs) are mainly expressed in mammalian germ cells, playing an important role in maintaining germ line DNA integrity, inhibiting transposon transcription and translation, participating in heterochromatin formation, epigenetic regulation, and germ cell genesis. They combine with P-element induced wimpy testis (PIWI) proteins to form effector complexes known as piRNA-induced silencing complexes (pi-RISC) to regulate the gene silencing pathway. Recent evidence suggests that numerous piRNAs, with tumor-promoting and tumor-suppressing functions in cancer development, are dysregulated in tumor tissues, and are related to clinical prognosis. In the present review, we summarize the current state of knowledge on the function and regulatory mechanisms of piRNAs in the tumorigenesis and progression of cancer, providing evidence for the potential use of piRNAs in the diagnosis and clinical treatment of cancer.