title: Serum Dickkopf-1 expression level positively correlates with a poor prognosis in breast cancer.
abstract: BACKGROUND
  The different expression level of Dickkopf-1 (DKK-1) in different cancers shows that the function of DKK-1 depends on the histological type of the cancer cells and the tissue microenvironment. To our knowledge, the serum expression level of DKK-1 in breast cancer is little known.
  
  
  METHODS
  Blood samples from 125 consecutive patients diagnosed with breast cancer and 53 control subjects from March 2008 to August 2013 were investigated. Serum DKK-1 expression levels were measured by enzyme-linked immunosorbent assay (ELISA). The overall survival (OS) and relapse-free survival (RFS) analyzed by log-rank test, and survival curves were plotted according to Kaplan-Meier.
  
  
  RESULTS
  The mean serum level of DKK-1 in patients with breast cancer was 4.99 ± 1.50 ng/mL, and was significantly higher than that in healthy individuals (1.88 ± 0.81 ng/mL, P < 0.001). DKK-1 level correlated significantly with TNM stage (P = 0.009), tumor grade (P = 0.02), lymph node metastasis (P = 0.001), and expression of HER2 (P = 0.002). The DKK-1 expression level was classified as high or low in relation to the median value, and patients with breast cancer (n = 125) were divided into a high expression group (n = 63) and a low expression group (n = 62). The Kaplan-Meier method for survival analysis showed that the patients with a high serum DKK-1 level had a poorer OS (48.7% vs. 81.3%, p = 0.01) and RFS (24.3% vs. 71.6%, p = 0.003) than those with a low expression level. The multivariate Cox regression analysis indicated that serum DKK-1 level was independent prognostic factors for OS and RFS.
  
  
  CONCLUSIONS
  Serum DKK-1 level can be used as a noninvasive biomarker for the prognosis of breast cancer.
  The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_161.
authors.forename: Shao-jie
authors.initials: SJ
authors.lastname: Zhou
authors.forename: Shou-rong
authors.initials: SR
authors.lastname: Zhuo
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Yang
authors.forename: Chun-xin
authors.initials: CX
authors.lastname: Qin
authors.affiliation: Department of Breast and Thyroid Surgery, Weihai Municipal Hospital, 70 HePing Road, Weihai 264200, Shandong, China. weihai_wangziliang@126.com.
authors.forename: Zi-liang
authors.initials: ZL
authors.lastname: Wang
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D053208:Kaplan-Meier Estimate; D008207:Lymphatic Metastasis; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D016019:Survival Analysis
chemical_list: D014408:Biomarkers, Tumor; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins