PIWIL1 and urinary bladder cancer: In contrast, PIWI proteins are highly expressed in various other tumors, including gastric, colon, liver, glioma, and bladder cancers.397–400 piRNAs regulate gene expression in cancer analogous to normal cells, dependent on PIWI proteins, and can also exert epigenetic control by interacting with regulatory factors or through direct regulating their expression.401 Additionally, piRNA can also bind to target genes, thereby degrading mRNA, altering its stability, or inhibition of its translation.402,403