PTEN and breast cancer: Poliseno et al. (2010) firstly reported that pseudogene PTENP1 derepresses the expression of tumor-suppressor gene PTEN through competing for PTEN-targeting miRNAs in prostate cancer cells and colon carcinoma cells, therefore exerting a tumor-suppressive role. Furthermore, they extended their analysis to other cancer driver genes with pseudogenes, such as oncogene KRAS and its pseudogene KRAS1P. Thereafter, the ceRNA function of more pseudogenes is revealed in various cancers, including breast cancer and gliomas (Shi X. et al., 2016; Li et al., 2017b; Wang Y. et al., 2019).