[Expression and significance of Nek2B and β-catenin in triple negative breast cancer]

Objective: To investigate the expression and significance of Nek2B and β-catenin expression in triple negative breast cancer (TNBC) at molecule levels. Methods: By using the methods of bioinformatics [GEO2R online tool, gene ontology (GO) function analysis, KEGG biological pathway enrichment analysis], the differentially expressed genes were screened from TNBC microarray data.Expression levels of Nek2B and β-catenin TNBC cell lines were detected by Western blot and qRT-PCR.From January 1, 2007 to December 31, 2012, eighty cases of TNBC were collected from the Second Hospital of Shanxi Medical University. The expression of Nek2B in TNBC tumor tissue was detected by immunohistochemistry and tissue microarray, and the relationship between Nek2B and clinical pathological characteristics of TNBC was analyzed. Results: Through bioinformatics analysis of the cDNA chip sets of 2 TNBC tumors(GSE38959,GSE27447), 998 differentially expressed genes were obtained in the initial screening, and 13 differentially expressed genes were revealed after intersection. The results of biological pathway analysis showed that the common differential expression genes were closely related to Wnt/β-catenin pathway, among which Nek2 expression showed the greatest difference and was associated with poor prognosis. Expression intensity of Nek2B and repeated β-catenin in the same TNBC cell line was consistent.The results of immunohistochemistry showed that the high expression of Nek2B was related to the high histological stage (G3;84.3% vs.37.9%, P<0.001), lymph node metastasis group (76.7% vs.54.1%, P=0.032), high Ki-67 positive index group (78.6% vs.52.6%, P=0.007) and β-catenin positive expression group (72.5% vs.27.3%, P=0.018). Conclusions: The high level of Nek2B expression is related to a poor prognosis in TNBC patients. In TNBC tissues and cells, the expression of Nek2B is correlated with β-catenin, suggesting that Nek2B may affect the occurrence and development of TNBC by regulating the Wnt/β-catenin patients signaling pathway.

Nek2B activates the wnt pathway and promotes triple-negative breast cancer chemothezrapy-resistance by stabilizing β-catenin

Background

The chemotherapy-resistance of triple-negative breast cancer (TNBC) remains a major challenge. The Nek2B kinase and β-catenin serve as crucial regulators of mitotic processes. The aim of this study was to test the correlation between Nek2B and TNBC chemotherapy sensitivity, and to determine the regulation of Nek2B on β-catenin and wnt/β-catenin signal pathway.

Methods

Gene Expression Omnibus(GEO) databases were used to gather gene exprsssion data of TNBC patients who undergoing chemotherapy. The co-expression of Nek2B and β-catenin in TNBC surgical sections and cells were analysed by immunohistochemistry, Q-RT-PCR, Western-blot and immunofluorescent staining. The impact of the expression of Nek2B and β-catenin in prognosis was also assessed using the Kaplan-Meier curves. CCK8 assay was used to detect the IC50 value of TNBC cell line. The endogenous binding capacity of Nek2B and β-catenin and phosphorylation of β-catenin by Nek2B were detected using co-immunoprecipitation (CO-IP). Chromatin immune-precipitation (ChIP) analysis and Luciferase Assays were used to evaluate the binding ability of the Nek2B, β-catenin and TCF4 complex with LEF-1 promoter. Nek2B-siRNA and Nek2B plasmid were injected into nude mice, and tumorigenesis was monitored.

Results

We found that overexpression of Nek2B and β-catenin in TNBC samples, was associated with patients poor prognosis. Patients with positive Nek2B expression were less sensitive to paclitaxel-containing neoadjuvant chemotherapy. Interestingly, in a panel of established TNBC cell line, Nek2B and β-catenin were highly expressed in cells exhibiting paclitaxel resistance. Our data also suggest that β-catenin binded to and was phosphorylated by Nek2B, and was in a complex with TCF4. Nek2B mainly regulates the expression of β-catenin in TNBC nucleus. Nek2B, β-catenin and TCF4 can be binded with the WRE functional area of LEF-1 promoter. Nek2B can activite wnt signaling pathway and wnt downstream target genes. The tumors treated by Nek2B siRNA associated with paclitaxel were the smallest in nude mouse, and Nek2B can regulate the expression of β-catenin and wnt downstream target genes in vivo.

Conclusion

Our study suggested that Nek2B can bind to β-catenin and the co-expression correlated with TNBC patients poor prognosis. It appears that Nek2B and β-catenin might synergize to promote chemotherapy resistance.