NOL7 Inhibits Ovarian Cancer Progression and Suppresses Angiogenesis by Stabilizing GADD45A to Deactivate STAT3

Ovarian Cancer is one of the most prevalent gynecologic malignancies worldwide. Dysregulated cell proliferation and angiogenesis are well-recognized to be involved in the pathogenesis of ovarian Cancer. Nucleolar Protein 7 (NOL7), a novel RNA-binding protein, has been identified as a tumor suppressor and a key anti-angiogenetic factor. However, the function of NOL7 and its underlying molecular mechanisms in ovarian Cancer remain unclear. In this study, we demonstrated that NOL7 expression was down-regulated in ovarian Cancer tissues, and low NOL7 expression was associated with poorer prognosis in patients with ovarian Cancer. Overexpression of NOL7 decreased cell viability, inhibited cell cycle entry and proliferation, and promoted Apoptosis in OVCAR-3 and SKOV-3 cells. Additionally, NOL7 overexpression decreased VEGF-A level, increased TSP-1, and suppressed angiogenesis of human umbilical vein endothelial cells (HUVECs). Conversely, knockdown of NOL7 in ovarian Cancer cells enhanced cell proliferation and angiogenesis, while reducing Apoptosis. In vivo experiments further confirmed that NOL7 overexpression inhibited tumor growth and angiogenesis. Mechanistic studies revealed that NOL7 could bind to the 3'UTR of growth arrest and DNA damage inducible alpha (GADD45A), and overexpression of NOL7 up-regulated GADD45A expression by stabilizing GADD45A mRNA in ovarian Cancer cells. The anti-cancer effects of the NOL7/GADD45A were mediated by inhibiting the phosphorylation of STAT3 at Ser727. Collectively, our findings indicate that NOL7 functions as a tumor suppressor in ovarian Cancer and provide a novel therapeutic target for the treatment of ovarian Cancer.

GADD45A; NOL7; angiogenesis; ovarian cancer; tumor growth.