Knockdown of NUSAP1 Inhibits Cell Proliferation and Invasion Through Down-Regulation of TOP2A in Human Glioblastoma

Abstract Background: Nucleolar and spindle associated protein 1 (NUSAP1) is an indispensable mitotic regulator, which has been reported to be involved in the development, progression, and metastasis of several types of cancer. Here, we investigated the expression and biological function of NUSAP1 in human glioblastoma multiforme (GBM). Methods: The expression of NUSAP1 on GBM tissues and cells were determined by database analysis, immunohistochemistry and Western blot. EdU assay, transwell assay and flow cytometric analysis were performed to evaluate the effect of NUSAP1 knockdown on GBM cell proliferation, cell invasion and cell apoptosis. RNA sequencing was used to screen for downstream molecules altered in GBM cells after NUSAP1 depletion. An intracranial mice model and bioluminescent imaging were used to assess the effect of NUSAP1 on tumor growth and survival time in vivo. Results: Analysis of the molecular data in CGGA, TCGA and Rembrandt datasets demonstrated that NUSAP1 was significantly up-regulated in GBM relative to low grade gliomas and non-neoplastic brain tissue samples. Kaplan-Meier analysis indicated that patients with tumors showing high NUSAP1 expression exhibited significantly poorer survival in both CGGA (P = 0.002) and Rembrandt cohorts (P = 0.017). Analysis of RNA sequencing data from P3-cells with stable knockdown of NUSAP1 revealed topoisomerase 2A (TOP2A) as a possible molecule down-regulated by the loss of NUSAP1. SiRNA knockdown of either NUSAP1 or TOP2A in U251, T98 and GBM derived patient P3 cells inhibited GBM cell proliferation and invasion, and induced cell apoptosis. Finally, stable knockdown of NUSAP1 with shRNA led to decreased tumor growth in an orthotopic xenograft model of GBM in mice. Conclusions: Taken together, NUSAP1 gene silencing induced apoptosis possibly through the down-regulation of the candidate downstream molecule TOP2A. Interference with the expression of NUSAP1 might therefore inhibit malignant progression in GBM, and NUSAP1 might thus serve as a promising molecular target for GBM treatment.