LOC400891 is higher in prostate cancer (PCa) tissues and cells. The patients with higher LOC400891 expression have advanced clinical features and a shorter biochemical recurrence-free survival time. Furthermore, multivariate analysis shows that the status of LOC400891 expression is an independent predictor of biochemical recurrence-free survival in PCa. Functionally, knockdown of LOC400891 could inhibit cell proliferation, migration and invasion. Mechanistically, LOC400891 is involved in the promotion of PCa cell proliferation and seems to be mediated by modulation of the PI3K-AKT-mTOR pathway and PTEN gene. LOC400891 involves cell migration and invasion by regulating the epithelial–mesenchymal transition (EMT) pathway (1).