OBJECTIVES: Liver cancer is the sixth most common malignant tumor in the world. Hepatocellular carcinoma (HCC) accounts for 85%-90% of all patients with liver cancer. It possesses the characteristics of insidious onset, rapid progression, early recurrence, easy drug resistance, and poor prognosis. NIMA related kinase 2 (NEK2) is a cell cycle regulating kinases, which regulates cell cycle in mitosis. Cellular senescence is a complex heterogeneous process, and is a stable form of cell cycle arrest that limits the proliferative potential of cells. This study aims to investigate the relationship between the expression level of NEK2 and the senescence in hepatoma cells, and to explore the effect of NEK2 expression on hepatoma cell senescence and the underlying molecular mechanism. METHODS: A total of 581 senescence-relevant genes were obtained from the GenAge website. The gene expression data of tumor tissues of 370 HCC patients were downloaded from the Cancer Genome Atlas database. The co-expression of NEK2 and aging-related genes was analyzed by R-package. KEGG was used to analyze the significant gene enrichment pathway of differentially expressed genes in NEK2 overexpression HEK293. The stable transfected cell lines with overexpression and knockdown of NEK2 were constructed in hepatoma cell line SMMC-7721 and HepG2, and senescence-associated β-galactosidase (SA-β-gal) staining was used to detect senescence, the cell proliferation was detected by CCK-8 method and clone formation experiment, the cell cycle was analyzed by flow cytometry, and the expression of proteins related to p53/p21, p16/Rb, and phosphatase and tensin homolog deleted on chromosome ten (PTEN)/Akt signal transduction pathway was detected by Western blotting. RESULTS: There were 320 senescence related genes co-expressed with NEK2. KEGG analysis showed that the senescence signaling pathway was significantly enriched in HEK293 cells with overexpression of NEK2.Compared with SMMC-7721 or HepG2 without knockdown of NEK2, the senescent cells of SMMC-7721 and HepG2 with knockdown of NEK2 were increased, cell proliferation and clone formation were decreased significantly, the percentage of cells in G₀/G₁ phase was increased, the expression levels of phospho-Akt (p-Akt) and phospho-Rb (p-Rb) protein were decreased significantly, and the expression level of p16 protein was increased significantly (all P<0.05). Compared with SMMC-7721 or HepG2 transfected with blank plasmid, the senescent cells of SMMC-7721 and HepG2 overexpressing NEK2 were decreased, the cell proliferation and clone formation were increased significantly, the percentage of cells in G₀/G₁ phase were decreased, the expression levels of p-Akt and p-Rb protein were increased significantly, and the expression level of p16 protein was decreased significantly (all P<0.05). CONCLUSIONS NEK2 may mediate the anti-aging effect of hepatoma cells through p16/Rb and PTEN/Akt signal transduction pathways, which provides a new theoretical basis for NEK2 to promote the progress of liver cancer and a new idea for the targeting treatment for liver cancer.
Carcinoma, Hepatocellular/pathology* ; Cell Line, Tumor ; Cell Proliferation/physiology* ; Cellular Senescence/genetics* ; HEK293 Cells ; Humans ; Liver Neoplasms/pathology* ; NIMA-Related Kinases/genetics* ; Proto-Oncogene Proteins c-akt/metabolism*

OBJECTIVETo study interaction between a novel centrosomal protein TACP1 and mitotic kinase Nek2A.

METHODSNek2A305-446 protein was expressed and purified in E.coli and TACP1 protein was expressed in transfected 293T cells. Pull-down assay was used to examine the interaction between Nek2A305-446 and TACP1. TACP1 and Nek2A complex was tested by co-immunoprecipitation assay with polyclonal anti-TACP1 antibody. The localization of those two proteins in Hela cells was verified by immunofluorescence.

RESULTSTACP1 was pulled down by Nek2A305-446 protein but not by GST control. Nek2A was co-precipitated with TACP1 protein by polyclonal anti-TACP1 antibody but not by pre-immunization serum. The Immunofluorescence test showed that these two proteins formed a complex at centrosome during mitosis.

CONCLUSIONCentrosomal protein TACP1 is a novel interacting protein with Nek2A, both of which are localized in centrosome during mitosis.

Cell Line ; Centrosome ; metabolism ; Escherichia coli ; genetics ; Fluorescent Antibody Technique ; HeLa Cells ; Humans ; Immunoprecipitation ; Mitosis ; NIMA-Related Kinases ; Protein Binding ; Protein-Serine-Threonine Kinases ; genetics ; metabolism ; Recombinant Proteins ; genetics ; metabolism ; Telomere-Binding Proteins ; genetics ; metabolism ; Transfection