PIWIL1 and malignant colon neoplasm: Given that PIWIL2 exhibits the most allelic losses in the entire PIWI pathway and is also downregulated in ulcerative colitis and colon cancer correlating with disease progression (Figs 1C, 2, 3, 4), we sought to investigate whether loss of PIWIL2 may indeed promote pro-tumorigenic phenotypes.