PER2 and colorectal cancer: A decrease in per2 expression after miR-34a has been implicated previously by in silico analysis [67], cross-linking immunoprecipitation sequencing (GSE161238, GSE161239), a negative correlation between per2 expression and miR-34a was observed in colorectal cancer tissue [27] and recent results clearly confirmed that miR-34a inhibits the expression of per2 under in vitro conditions.