Subcellular localization of nucleolar protein 14 and its proliferative function mediated by miR-17-5p and E2F4 in pancreatic cancer.

Pancreatic cancer is one of the most lethal malignancies worldwide. Acquiring infinite proliferation ability is a key hallmark and basis of tumorigenesis. NOP14 is an identified ribosome biogenesis protein that plays potential roles in cell proliferation. However, the function and molecular mechanism of NOP14 remain ambiguous in most human cancers. In this study, we first investigated the subcellular localization and expression of NOP14 by multiple quantitative assays in pancreatic cancer. We confirmed that NOP14 was mainly localized in nucleolus in human pancreatic cancer cells. Then we studied the regulatory effects of this nucleolus protein on tumor cell proliferation in vitro . NOP14 was demonstrated to play a dominant pro-proliferation role in pancreatic cancer. Furthermore, we identified miR17-5p as a downstream target of NOP14. Transfection of miR17-5p mimics or inhibitors rescued the down- or upregulated effect of NOP14 on cell proliferation by regulating expression of P130. In addition, NOP14 induced expression of transcription factor E2F4 independent of miR17-5p/P130 signaling, which simultaneously activated a set of targeted genes, such as CCNE1, PIM1, AKT1 etc., to promote tumor proliferation. These findings might provide novel insights for better understanding the diverse function of NOP14 in human malignancies to develop new strategies for targeted therapy.