Knockdown of NUSAP1 inhibits cell proliferation and invasion through downregulation of TOP2A in human glioblastoma

Nucleolar and spindle associated protein 1 (NUSAP1), an indispensable mitotic regulator, 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 (GBM), an aggressive brain tumor type with largely ineffective treatment options. Analysis of the molecular data in CGGA, TCGA and Rembrandt datasets demonstrated that NUSAP1 was significantly upregulated 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 downregulated by the loss of NUSAP1. Molecular analysis of the CGGA data revealed a strong correlation between NUSAP1 and TOP2A expression in primary gliomas and recurrent gliomas samples. 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. Taken together, NUSAP1 gene silencing induced apoptosis possibly through the downregulation 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.