CDKN1B and breast cancer: Given that tumors with p27 downregulation have poor prognosis [65, 66], including colon, ovary and breast cancers, and p27 is rarely inactivated in human cancers, our results can suggest that loss of PCBP1 most likely could be the key initial step for p27 downregulation, leading to eventual tumorigenesis, as we tentatively used various types of tumor cells as well as tumor datasets in this study to draw the similar conclusion, hinting the general role of PCBP1-p27 signaling in tumorigenesis suppression.