Functional characterization of NIMA (never in mitosis gene a)-related kinase 2 in Hepatocellular Carcinoma

Abstract

Background: The centrosomal kinase NIMA (never in mitosis gene a)-related kinase 2 (Nek2), which regulates the separation of centrosome, has been reported to be overexpressed in various cancers. Nevertheless, the expression profile of Nek2 in HCC has not been investigated and its role in HCC remains unknown. Previously our team has demonstrated the involvement of centrosomal protein TAX1BP2 in hepatocarcinogensis, prompting us to examine the functional role of Nek2 in HCC. Material and Methods: Nek2 mRNA and protein expressions were examined in paired clinical HCC samples by RT-PCR and immunohistochemistry respectively, and the clinical significance was evaluated. Nek2 knockdown stable clones were established in HCC cell line PLC and metastatic 97L cell line by lentiviral transduction. The stable clones were then subjected to various functional assays. The effects of Nek2 on cell proliferation, migration and invasion were investigated.

Results: Overexpression of Nek2 was found in 80% (39/49) of tumours as compared to their non-tumour counterparts (P<0.0001). Nek2 expression was significantly associated with the absence of tumour encapsulation (P=0.013), higher tumour stage (P=0.003) and presence of venous invasion (P=0.012). Immunohistochemistry revealed Nek2 localization at nucleus and cytoplasm, suggesting that Nek2 might have functions other than controlling centrosome separation. Nek2 expression was detected in all HCC cell lines. Diminution of Nek2 dramatically impeded the proliferation rate of HCC cells (P<0.0001) and profoundly suppressed the cell motility (P<0.0001) as well as invasiveness (P=0.0232).

Conclusions: Our data has shown for the first time the oncogenic role of Nek2 in HCC. We believe that Nek2 expression encouraged aggressive tumour behaviour by promoting cell proliferation and invasiveness.