Consistently, a recent study revealed that piRNA expression was not detectable in several PIWIL1-expressing cancer cell lines, and co-immunoprecipitation assays failed to detect the association of PIWIL1 with small RNAs in pancreatic, breast, colon and gastric cancer cells that express PIWIL1 (Li et al., 2020). This evidence concerns the gene PIWIL1 and gastric cancer.