Cancer Management and Research (Dec 2018)
Knockdown of nucleophosmin 1 suppresses proliferation of triple-negative breast cancer cells through activating CDH1/Skp2/p27kip1 pathway
Abstract
De Zeng,1,* Yingsheng Xiao,2,* Jianling Zhu,3 Chunyan Peng,4 Weiquan Liang,5 Haoyu Lin5 1Department of Medical Oncology, Cancer Hospital of Shantou University Medical College, Shantou 515031, China; 2Department of Thyroid Surgery, Shantou Central Hospital, Shantou 515000, China; 3Department of Pathology, Cancer Hospital of Shantou University Medical College, Shantou 515031, China; 4Department of Clinical Laboratory, Taihe Hospital of Hubei University of Medicine, Hubei 442008, China; 5Department of Thyroid and Breast Surgery, The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong 515000, China *These authors contributed equally to this work Background: NPM1 is a multifunctional phosphoprotein that commutes between the cytoplasm and nucleus in cell cycle process, which appears to be actively involved in tumorigenesis. Herein, we sought to investigate the possible role and prognostic value of NPM1 in triple-negative breast cancer (TNBC). Methods: An array of public databases, including bc-GenExMiner v4.0, GOBO, GEPIA, UALCAN, ONCOMINE database and Kaplan-Meier plotter, were used to investigate the expression feature and potential function of NPM1 in TNBC. Immunohistochemistry, immunofluorescence, proliferation and colony formation, flow cytometry and western-blotting assays were used to analyze and verify the function and relevant mechanism of NPM1 in TNBC tissues and cells. Results: According to analysis from bc-GenExMiner, the expression level of NPM1 was significantly higher in basal-like subtypes than luminal-A, HER-2 or normal-like subtypes of breast cancer (P<0.0001). GOBO database analysis indicated that the expression of NPM1 in basal-A or basal-B was significantly higher than luminal-like breast cancer cells. Immunohistochemistry assay in 52 TNBC tissue samples showed that positive expression of Ki-67 was 93.5% in the high-NPM1-expression group and 66.7% in the low-NPM1-expression group, respectively (P=0.032). Proliferation and colony formation assays demonstrated that inhibition of NPM1 suppressed cell growth by approximately 2-fold and reduced the number of colonies by 3-4-fold in MDA-MB-231 and BT549 cells. Moreover, inhibition of NPM1 in MDA-MB-231 and BT549 cells increased the percentage of cells at G0/G1 phase and decreased the percentage of cells at both S and G2/M phase, as compared with control counterparts. Western-blotting results showed that down-regulation of NPM1 could elevate CDH1 and p27kip1 expression, while decrease Skp2 expression both in MDA-MB-231 and BT549 cells. In addition, high mRNA expression of NPM1 correlated with shorter RFS (HR=1.64, P=0.00013) and OS (HR=2.45, P=0.00034) in patients with TNBC. Conclusions: NPM1 is significantly high expressed basal-like/triple-negative breast cancer and is correlated with shorter RFS and OS in this subset of patients. Knockdown of NPM1 impairs the proliferative capacity of TNBC cells via activation of the CDH1/Skp2/ p27kip1 pathway. Targeting NPM1 is a potential therapeutic strategy against TNBC. Keywords: nucleophosmin 1, proliferation, mechanism, prognosis, triple-negative breast cancer
